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Table of Content
25 July 2022, Volume 41 Issue 7
Invited review
Designing petrochemical smart plant of the future: state of the art, comparison and prospects
WANG Zizong, GAO Libing, SUO Hansheng
2022, 41(7):  3387-3401.  doi:10.16085/j.issn.1000-6613.2022-0306
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It has been a 10-year development history of smart plant undertaken by China Petrochemical Corporation since 2012. The planning and design smart plant 3.0 is currently underway. What problems exist in the current petrochemical smart plant? What are the development trends of intelligent process manufacturing? How to carry out top-level design of future smart plant?In response to these three questions, this paper summarizes the existing problems, business need and technical capability requirements of petrochemical plant. The technology development trend of intelligent process manufacturing is analyzed from three perspectives, including industrial software, open process automation (OPA) and EPC implementation. The cases and enlightenment of Global Lighthouse Network (GLN) are studied. The basic characteristics, connotation and evolution route of intelligent process manufacturing are expounded. The six characteristics and five key capabilities that petrochemical smart plant should have in the future are put forward. Scope of construction content, implementation consideration and key elements of use cases were discussed, and finally the future development is prospected.

Exploration on technical path of modern coal chemical industry under the background of carbon neutralization
YANG Xueping
2022, 41(7):  3402-3412.  doi:10.16085/j.issn.1000-6613.2022-0475
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This paper analyzes the technical path of low-carbon development of modern coal chemical industry, the effect on reducing carbon emissions and future application prospect from four aspects: carbon reduction from the source, carbon emission control in the process, carbon capture and storage at the end, and high value-added utilization of carbon resources. The technical path of carbon reduction from the source includes raw material structure adjustment and energy structure adjustment. By introducing hydrogen-rich and green-hydrogen resources, coal utilization efficiency is improved; and by replacing coal with natural gas and electricity, especially by using abandoned wind and electricity, energy consumption is reduced, which can significantly reduce carbon emissions and production costs. The technical path of carbon emission control in the process includes energy saving and efficiency improvement, and development of innovative technologies. Relying on the technical advancements to break through the bottleneck of traditional process, it is easy for enterprises to take measures to realize energy-saving and emission reduction. The technical path of carbon capture and storage at the end includes geological deep burial, oil displacement, and strengthening deep salt water exploitation, etc. By capturing high-concentration CO2 produced in the process at low cost, it can effectively improve the oil and gas recovery, and provide additional water supply for water deficient areas. The technical path of high value-added utilization of carbon resources mainly includes the chemical conversion of CO2 to high value-added and bulk chemicals. China is accelerating the technological R&D and demonstration application of CO2 to low-carbon olefins, aromatics, methanol and carbonate, striving to transform CO2 from the end emitter of fossil utilization to the participant of carbon recycling. In the future, it is the general trend for modern coal chemical industry to be integrated with new energy, and break through the key core technologies of carbon emission reduction, so as to contribute to the goal of carbon neutrality.

Chemical processes and equipment
Solid-liquid two-phase mixing method and its uniformity detection technology
GUO Changhao, YA Mingsheng, XU Youlin, ZHENG Jiaqiang
2022, 41(7):  3413-3430.  doi:10.16085/j.issn.1000-6613.2021-1875
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Solid-liquid two-phase mixing technology is an important operation technology in industrial and agricultural production applications, which is widely used in solid dispersion, dissolution and leaching, crystallization and precipitation, solid catalytic reaction, powder pesticide mixing, and so on. The uniformity of the solid-liquid two-phase mixing has an important influence on the production or application of products. Therefore, the research status of solid-liquid two-phase mixing technology is reviewed in this paper. Firstly, the dispersion mechanism of solid particles in the liquid phase is introduced. Then, two common solid-liquid two-phase mixing methods are discussed—chemical dispersion and physical dispersion. The chemical dispersion method includes adding surfactants and coupling agents or electrochemical modification. Physical dispersion methods include mechanical mixing which using stirred tanks, impinging stream mixers, jet mixers, static mixers, and dynamic mixers, as well as ultrasonic dispersion, and electrostatic dispersion which can be used to pre-dispersion. At the same time, some representative detection methods of solid-liquid two-phase dispersion and mixing uniformity are introduced, such as using probes, image analysis and processing, ultrasonic attenuation and dynamic light scattering, electrical resistance tomography, etc. Finally, based on the analysis of existing problems, the future development of solid-liquid two-phase mixing technology in the direction of diversification and intelligence has been prospected.

Research progress on working medium and heat transfer structure of liquid cooling plate with array jet impingement
TANG Zhenbiao, CUI Xiaoyu
2022, 41(7):  3431-3445.  doi:10.16085/j.issn.1000-6613.2021-1739
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Liquid array jet impingement cooling is one of the most effective techniques to solve the heat dissipation problem of high heat flux. It can effectively remove heat from the target surface. It has the advantages of high heat dissipation capacity, high energy efficiency ratio and low noise, having a huge advantage in heat dissipation. In this paper, the research progress of array jet impingement at home and abroad is briefly summarized. The influence of array jet impingement on heat transfer characteristics of liquid array jet is comprehensively analyzed from two aspects that heat transfer medium and heat transfer structure of jet impingement cold plate. Two new array jet types that incline jet and swirl jet are introduced. The principle of strengthening heat transfer in jet impingent process by common liquid working medium and nano fluid working medium is introduced. Three kinds of array jet structures including nozzle shape, nozzle arrangement and impact surface structure are introduced. The results show that the nozzle with different shapes will affect the jet velocity and turbulent characteristics of the fluid, the nozzle arrangement will affect the interaction of the jet fluid and the effective impact area, and the impact surface will affect the circulation mixing of the jet working medium. These kinds of array jet structures will have a great influence on the heat transfer characteristics of the array jet impingement cooling plate. Understanding the main influence factors of array jet impact effect is the fundamental method to improve jet heat transfer performance.

Numerical simulation of membrane reactor of methane steam reforming for distributed hydrogen production
YAN Peng, CHENG Yi
2022, 41(7):  3446-3454.  doi:10.16085/j.issn.1000-6613.2021-1868
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The membrane reactor system with integrated chemical reaction and membrane separation for distributed hydrogen production is of vital importance to simplify chemical process, lower energy consumption and improve techno-economics. Herein, the mathematical model were adopted to simulate methane steam reforming process in membrane reactor, and thus analyze the effect of operational strategies of permeation side, reaction pressure, reaction temperature, palladium-based membrane performance and activity of catalyst on the behaviors of membrane reactor. Subsequently, case study was conducted with the aim of maximum conversion of 1m3/h CH4 to compare membrane reactor technology and "conventional reactor + membrane separation" process. The results showed that compact design of membrane reactor under the conditions of 30atm and 500℃ can be achieved and the membrane reactor presented obvious advantages over the process technology of "conventional reactor+membrane separation". However, more active palladium-based membranes and catalysts, particularly 10 times than current performance, were in urgent need for further process intensification. The results can provide fundamental guidelines for the design, operation and further performance intensification of membrane reactor for distributed hydrogen production with various scales.

Analysis and characterization of gas swirling flow dynamic characteristics in a cyclone separator
XIE Ming, SUN Liqiang, SONG Jianfei, WEI Yaodong
2022, 41(7):  3455-3464.  doi:10.16085/j.issn.1000-6613.2021-1752
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Gas swirling flow in the cyclone separator exists strong dynamic characteristics, which are characterized by the instantaneous parameters fluctuate over time. In order to characterize the dynamic characteristics of the gas swirling flow in a cyclone separator, the instantaneous tangential velocity and instantaneous pressure in the cyclone measured by the hot wire/film anemometer (HWFA) and dynamic pressure sensor were analyzed on both time and frequency domain. The results showed that the waveform distribution of the instantaneous tangential velocity in the time domain wass related to the gas swirling flow swing, and the standard deviation was dependent on the fluctuation intensity of gas swirling flow. The dominant frequency and power spectral density (PSD) in the frequency domain were used to illustrate the quasi-periodic behavior, transmission behavior and attenuation characteristics of the swirling flow dynamic parameter. It is also the reflection of the swirling flow swing behavior and its range of influence. Therefore, time-frequency analysis based on the instantaneous tangent velocity and the instantaneous pressure might better indicate the fluctuation characteristics of the swirling flow, consequently, which can be applied to characterize the dynamic characteristics of the gas swirling flow in the cyclone separator.

Analysis of heat transfer and resistance performance of U-shaped baffle heat exchanger
GU Xin, ZHANG Qianxin, WANG Chaopeng, FANG Yunge, LI Ning, WANG Yongqing
2022, 41(7):  3465-3474.  doi:10.16085/j.issn.1000-6613.2021-1633
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Periodic whole cross-section models of U-shaped baffle heat exchanger and torsional flow heat exchanger were established, and the shell side performance of two heat exchangers was numerically studied by using computational fluid dynamics(CFD) method. Compared with the torsional flow heat exchanger, the results showed that the pressure drop in the shell side of the U-shaped baffle heat exchanger was reduced by 45.3%—47.5%, the heat transfer coefficient was reduced by 9.9%—13.5%, the uniformity was improved by 2.4%—4.0%, and the comprehensive performance was improved by 4.0%—14.6%. The field synergy results showed that the synergy of fluid velocity and pressure gradient in the shell side of U-shaped baffle heat exchanger was superior to that of the torsional flow heat exchanger, while the synergy of fluid velocity and temperature gradient was not as good as that of the torsional flow heat exchanger. The Laser Doppler Velocimeter (LDV) experiment verifies the accuracy of the simulation method and the reliability of the simulation results. The influence of U-shaped baffle structure parameters and arrangement on the pressure drop and heat transfer performance of the heat exchanger shell side is studied. The results show that the angle and arrangement of the baffles have a significant impact on the performance, while the width and spacing of baffles have little impact.

Shell-side heat transfer enhancement of a novel longitudinal flow oil cooler
LIU Shijie, MO Xun, TU Aimin, ZHU Dongsheng, TAN Lianyuan
2022, 41(7):  3475-3482.  doi:10.16085/j.issn.1000-6613.2021-1879
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In this paper, a heat transfer enhancement scheme for the novel twisted trifoliate tube longitudinal flow oil cooler was proposed. The heat transfer and pressure drop performance of the shell side of twisted trifoliate tube oil cooler was experimentally investigated and compared to the twisted oval tube oil cooler and conventional segmental baffle oil cooler. The experimental results showed that under the same oil flow rate, the shell-side heat transfer coefficient, pressure drop and h/?p of the twisted trifoliate tube oil cooler were 138.7%—190.5%, 19.6%—37.8% and 77.2%—130.4% higher than that of the conventional segmental baffle oil cooler, and were 257.8%—298.6%, 140.5%—158.4% and 40.1%—65.7% higher than that of the twisted elliptical tube oil cooler, respectively. The results proved the twisted trifoliate tube oil cooler had a good heat transfer enhancement effect. The mechanism of heat transfer enhancement was also analyzed. Based on the experimental data, the correlations of Nu and f on the shell side of twisted trifoliate tube and twisted oval tube oil cooler were deduced with Re ranging from 80 to 550.

Boiling heat transfer and resistance characteristics of two types of sintered structures
MAO Jijin, ZHANG Donghui, SUN Lili, LEI Qinhui, QU Jian
2022, 41(7):  3483-3492.  doi:10.16085/j.issn.1000-6613.2021-1794
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The boiling heat transfer enhancement by porous materials is an important topic in the fields of energy and chemical industry. The subcooled flow boiling experiment was carried out with the deionized water as the working fluid. Two types of sintered structures were investigated: parallel porous microchannel and flat channel (only the bottom layer sintered). It was found that parallel porous microchannels presented higher HTC (heat transfer coefficient) and CHF (critical heat flux) than flat microchannels, which was attributed to the excellent capillary liquid supply performance of porous microchannels. The ratio of the bottom thickness to the particle size (δ/d) had a great effect on the boiling heat transfer performance of parallel porous microchannels. Too high δ/d would cause a deterioration in heat transfer performance. The mass flux exerted different influence on heat transfer performance over sintered samples with small or large particle size. Parallel microchannels showed greater pressure drops than flat microchannels. With the same bottom thickness, the average pressure drop increased almost linearly with sintered particle size. The visual observation showed that the flow patterns of the two channels were different at medium and high heat flux, and the main phase-change mechanism was thin film evaporation.

Evolution characteristics of transient evaporation rate of Al2O3 nanofluid droplet
LI Yucan, HU Dinghua, LIU Jinhui
2022, 41(7):  3493-3501.  doi:10.16085/j.issn.1000-6613.2021-1808
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The applications of nanofluid droplet evaporation play an important role in inkjet printing, chip manufacturing and medical diagnosis. An arbitrary Lagrangian-Euler (ALE) method was applied to transiently simulate the evaporation period of alumina nanofluid droplets. The physical fields of vapor concentration, nanoparticle concentration, temperature gradient and flow direction during the evaporation process were coupled and the effect of Marangoni flow inside the droplets was taken into consideration. Meanwhile, according to the visualization images of evaporation experiments, the evolution behavior of the transient evaporation rates of nanofluid droplets and the effects of particle concentration along with substrate temperature on the evaporation modes were analyzed and discussed, respectively. The results demonstrated that at the beginning of the evaporation process, the nanofluid droplets remained in the evaporation mode with constant contact radius, and the transient evaporation rates decreased gradually with the decrease of the gas-liquid interface area. In the middle stage of evaporation process, when the particle concentration increased to 26%, the transient evaporation rate curve reached the stationary point. Due to the influence of Marangoni flow on the internal flow field of the droplets, the internal heat transfer of droplets was enhanced as the evaporation process reached to the end. Moreover, the droplets formed a liquid film on the surface of the particles which had been deposited on the substrate, the transient evaporation rates of droplets raised rapidly therefore.

Flow boiling heat transfer characteristics of R1234yf in horizontal microchannel
FENG Longlong, ZHONG Ke, ZHANG Yusen, SHANG Qingchun, JIA Hongwei
2022, 41(7):  3502-3509.  doi:10.16085/j.issn.1000-6613.2021-1823
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The flow boiling heat transfer characteristics of environmentally friendly refrigerant R1234yf in a 0.5mm horizontal circular microchannel were studied experimentally. The heat transfer coefficients (HTCs) of R1234yf were measured and compared with that of R134a, and the effects of mass flux, heat flux and vapor quality on HTC were analyzed. The saturation temperature was (17±1)℃, and the mass fluxes vary from 1000kg/(m2·s) to 2500kg/(m2·s) with heat fluxes ranging from 25kW/m2 to 143kW/m2. The experimental results showed that the HTC of R1234yf in 0.5mm microchannel increases with the increase of heat flux, while the mass flux and vapor quality showed a weak influence on it. The trend indicated that nucleate boiling was the dominant mechanism for flow boiling heat transfer. In addition, the heat transfer performance of R1234yf and R134a were compared under the same working conditions. The HTCs of R1234yf and R134a were almost identical and both increased with the increase of heat flux, but the heat flux for the occurrence of dryout of R1234yf was smaller than that of R134a. Finally, the experimental data for the two refrigerants were compared with two nucleate boiling-dominated correlations from literature and good agreements were obtained.

Experimental and numerical investigation of loop heat pipe with flat ceramic capillary wick
ZHENG Suzheng, LI Nanxi, DONG Deping
2022, 41(7):  3510-3518.  doi:10.16085/j.issn.1000-6613.2021-1840
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A flat ceramic capillary wick LHP was designed and manufactured, and its heat transfer performance was experimentally studied with the environment-friendly refrigerant R245fa as the working fluid. Based on the traditional thermal resistance network model, the calculation process was optimized. The reservoir temperature was calculated in parallel through two paths, and their residuals were used as the convergence condition to improve the calculation speed. The experimental and simulation results showed that the thermal resistance of the condenser accounts for about 90% of the total thermal resistance in the fixed conductance mode (FCM). When the system just entered the FCM, the thermal resistance of the evaporator was the smallest, and the heat transfer performance of the evaporator was the best. The simulation results were in good agreement with the experimental ones. The maximum temperature calculation error did not exceed 5℃, and the maximum relative error of thermal resistance was 17%. According to the model calculation, the pressure drop caused by the working medium flowing through the capillary wick accounted for 90% of the total pressure drop of the system. The evaporation temperature increased with the increase of wick thickness, and increasing the thickness of the wick was beneficial to reduce the heat leakage to the reservoir. The increase of the effective thermal conductivity of the wick will significantly increase the heat leakage.

Energy processes and technology
Research progress in preparation and kinetics of γ-valerolactone synthesis from hemicellulose and its derivatives
ZHUANG Yuting, WANG Jianhua, XIANG Zhiyan, ZHAO Juan, XU Qiong, LIU Xianxiang, YIN Dulin
2022, 41(7):  3519-3533.  doi:10.16085/j.issn.1000-6613.2021-1632
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Hemicellulose is one of the three main components of wood biomass resources, which can be converted into high value-added compounds such as furfural (FAL), furfuryl alcohol (FOL), levulinic acid (LA), γ?-valerolacton (GVL) by chemical or biological methods. This route can realize the high-value utilization of carbon containing renewable resources, and is of great significance for the development of renewable bioenergy. In this paper, the domestic and international research progress of direct conversion of hemicellulose, FAL and FOL to GVL are reviewed from the aspects of catalysts, hydrogen sources and solvents. Moreover, the typical kinetic models of the processes of xylose to FAL and FAL to GVL are summarized. Bifunctional acid catalysts with adjustable Br?nsted/Lewis acid sites, such as metal modified molecular sieves, are highly efficient catalysts for the transfer hydrogenation of hemicellulose and its derivatives to GVL, and the strategy and mechanism of acid site regulation are the key issues. The development of multi-metal coordination or acid-base coordination catalysts is the direction of catalytic system innovation.

Demulsification process and enhancement by viscosity reduction for water-in-heavy oil emulsions
ZHANG Xincheng, HE Lin, SUI Hong, LI Xingang
2022, 41(7):  3534-3544.  doi:10.16085/j.issn.1000-6613.2021-1708
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Water-in-heavy oil（heavy W/O）emulsions widely exist in the petroleum exploration and petrochemical processing. Due to their high viscosity, high density, and strong interface stability, the separation of heavy W/O emulsions is fairly difficult, inevitably leading to an increasing cost in production. To enhance the separation efficiency of heavy W/O emulsions, in this study, the influence of temperature and toluene addition on the viscosity of heavy oil was systematically investigated. On this basis, the synergistic mechanism between viscosity reduction and dehydration ratio was discussed. A proposed TJU-3 demulsifier was used to break the heavy W/O emulsions. The optimal process conditions were obtained by varying the demulsifier concentration and the demulsification temperature. The molecular simulation method was used to build the heavy oil average molecular model and calculate the diffusion coefficient of SARA in the heavy oil with different content of toluene. The effect of toluene on the interaction of SARA in heavy oil was analyzed and the transport process of asphaltenes and TJU-3 demulsifier molecules at oil-water interface was studied. The results showed that a complete demulsification could be achieved within 1h when the viscosity of the heavy oil was reduced to 1500mPa·s. When the viscosity was reduced to 50mPa·s, the demulsification could be completed within 20min. When the concentration of demulsifier in the emulsions was 400mg/L, the dehydration ratio of the emulsions was the highest. When demulsification temperature was 60℃, demulsification rate was the highest. The diffusion coefficient of resins increased most significantly in SARA components, which was the main reason that the viscosity of heavy oil could be rapidly reduced by toluene. The TJU-3 demulsifier could break the asphaltene interface film, which achieved the demulsification of heavy W/O emulsions. The synergistic mechanism and technological conditions can provide reference for rapid demulsification of heavy W/O emulsion at low temperature in petroleum industry.

Effect of particulate diameter of silica gel on performance of solar adsorption refrigeration system
WANG Zepeng, YUAN Zhongxian, WANG Jie, WEN Xin, LIU Yimo
2022, 41(7):  3545-3552.  doi:10.16085/j.issn.1000-6613.2021-1803
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The effect of silica gel adsorbent with different particle sizes on the heat and mass transfer and the cooling capacity of the solar adsorption refrigeration system was experimentally investigated. The system adopted the silica gel-water as the work pair for refrigeration. Under close solar radiation conditions, contrast experiments were conducted in three groups of silica gel particle of 1mm, 3mm and 5mm in average diameter. The results revealed that the silica gel particle of the medium size performed the best with both the highest COP and tspecific cooling power SCP2, which was defined by the whole cycle time. Although the small particle size increased the filling mass of the adsorbent, it also caused the increment of the mass transfer resistance along the adsorption bed axis. This increment of the mass transfer resistance frustrated the adsorbent near the bed end to fully play the role. On the other hand, the silica gel particle of the big size would deteriorate the heat transfer of the bed, leading to longer time in process of the preheat and the cooling to the bed. In general, it was demonstrated that the particulate diameter of the adsorbent material was a significant factor to impact the performance of the solar adsorption refrigeration system and should be paid full attention in engineering design.

Performance characteristics for heating of gas engine-driven heat pump system with waste heat recovery at high ambient temperature
HU Yafei, LYU Jie, HAN Tao, SONG Wenji, FENG Ziping
2022, 41(7):  3553-3563.  doi:10.16085/j.issn.1000-6613.2021-1869
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Gas engine-driven heat pump (GHP) is an advanced low-carbon, energy-saving and clean heating technology. In view of the limitations of the current commonly used in GHP system technology research, such as the lower limit of the ambient temperature of R134a refrigerant for heating mode was high and the energy efficiency of the piston compressor was low, an energy-efficient GHP experimental platform was built innovatively based on the use of R410A refrigerant and scroll compressors. The heating performance characteristics of the GHP system with waste heat recovery device at high ambient temperature were investigated. The changing laws of heating capacity (Qh), gas consumption power (Pgas), compressor power (Pcomp), primary energy ratio(PER) and coefficient of performance (COP) were obtained under the conditions of different outlet water temperature (tw,out), engine speed (Neng), inlet water flow rate (Gw)and whether the engine waste heat was recovered or not. The error analysis of the key performance parameters was carried out. The results illustrate that when tw,out increases from 41℃ to 50℃, Qh, PER and COP decrease by 3.12%, 13.17% and 18.92%, respectively. The decline extent of PER is much smaller than that of COP. When Neng increases from 1200r/min to 1800r/min, the increase of Qh, Pgas and Pcomp are 51.03%, 43.98% and 55.37% respectively at tw,out of 50℃ . Meanwhile, the increase of PER is 4.90% due to the influence of the increase of the effective thermal efficiency of engine. When Gw increases from 5.8m3/h to 11.5m3/h, the system performance parameters are not sensitive to the change of Gw. When the system undergoes waste heat recovery, Qh, PER and COP are all significantly increased, and they increase by 31.18%, 36.06% and 31.54% respectively when Neng is 1200r/min and tw,out is 41℃. The ratios of the recovered waste heat to the total heating capacity and total engine waste heat are 17.48%—24.54% and 44.16%~63.39% respectively. According to the error analysis, the errors of Qh, Pgas and PER are 3.29%, 1.00% and 3.44% respectively, indicating that the test results have high accuracy.

Comparison and analysis of heat-power decoupling technologies for CHP units
WANG Zijie, GU Yujiong, LIU Haochen, LI Changyun
2022, 41(7):  3564-3572.  doi:10.16085/j.issn.1000-6613.2021-1626
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Increasing the flexibility of combined heat and power (CHP) unit operation can improve the utilization rate of renewable energy and reduce the "abandoned wind energy" and "abandoned solar energy". However, there have been few comparison and analysis studies of the flexible modification techniques. In this paper, Ebsilon software was used to establish thermodynamic model of a 600MW unit, and an associated energy consumption model was established by passing simulation results to a Matlab routine. The influence of heat-power decoupling technologies, such as heat pump, electric boiler, heat storage tank, and steam turbine retrofit technologies on the operation feasible region and thermodynamic performance within the operation feasible region was analyzed using thermodynamic and energy consumption models. The results showed that the heat-power decoupling technologies can expand the operation feasible region of the unit. When heat load of the unit was 500MW, minimum peaking capability of the unit can be ranked from the largest to the smallest after using the heat-power decoupling technologies: electric boiler>bladeless shaft operation of low pressure cylinder>low pressure cylinder near zero output>compression heat pump>heat storage tank. However, energy and exergy efficiency of electric boiler were the lowest among all heat-power decoupling technologies. After analysis, it is an energy-saving decoupling way to use compression heat pump or compression heat pump coupled with heat storage tank in CHP units.

Industrial experiment on the effect of SNCR using urea as the reducing agent on the operation of large capacity power station pulverized coal boiler
YANG Xigang, CHEN Guoqing, HUANG Linbin, GU Shijun, LI Changsong, ZHANG Yong, JIN Baosheng
2022, 41(7):  3573-3581.  doi:10.16085/j.issn.1000-6613.2021-1750
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Industrial experiments were carried out on a 660MW super-critical down-fired boiler, and the effects of SNCR on thermal efficiency, NO x emission, NO xdistribution at SCR inlet, and flue gas temperature in the boiler furnace were analyzed in detail. The results showed that the evaporation and heat absorption of the water injected into the furnace by SNCR system was the main reason for the decrease of boiler thermal efficiency. when the water flow rate increased by 1.0t/h, the boiler thermal efficiency decreases by about 0.05%. The dilution water flow rate had a significant effect on the atomization and distribution of urea solution in the furnace. Under the condition of the same amount of urea, the denitration efficiency of SNCR could be significantly improved by appropriately increasing the dilution water flow. Compared with the flue gas flow (about 2400t/h) under the test load, the flow of urea solution injected into the furnace was relatively small, accounting for about 0.2%—0.5%. Therefore, it had no obvious effect on the flue gas temperature in the furnace.Adjusting the flow rate of dilute water and urea solution within a certain range had no obvious influence on NO x distribution in the section of SCR inlet flue, but too low dilution water flow rate would affect the mixing effect of urea in the furnace, and then affected the distribution of NO xconcentration in the section of SCR inlet flue.

Development and commercial application of Russian residue hydrotreating technology
ZHAO Yusheng, CUI Ruili, NIU Guifeng, ZHAO Yuansheng, CHENG Tao, HE Shengbao, SONG Junnan, ZHANG Linzhou
2022, 41(7):  3582-3588.  doi:10.16085/j.issn.1000-6613.2022-0179
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The sulfur, nitrogen, residual carbon and metal contents of Russian residue are higher than the feed requirements of catalytic cracking unit, so hydrotreating is required. The molecular structure of Russian residue was characterized by FT-ICR, MS and NMR. PHR series catalysts and their grading were optimized according to the characterized properties and molecular structure of Russian residue, and the Russian residue hydrotreating technology was then developed. The commercial application has realized the deep removal of S, N, Ni and V and the deep conversion of carbon residue in Russian residue. The catalyst running time reaches 19416h, and the processing of feed oil reaches 6000 tons per ton catalyst, both 62% higher than the design value. Through analyzing the molecular morphology of remaining nitrides in the hydrogenated residue, we proposed the future technical optimization and improvement direction.

Industrial catalysis
Research progress of gold based mercury-free catalysts for acetylene hydrochlorination
ZENG Junjian, ZHAO Jigang
2022, 41(7):  3589-3596.  doi:10.16085/j.issn.1000-6613.2021-1644
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The development of mercury-free acetylene hydrochlorination catalysts has great significance to the green development of polyvinyl chloride (PVC) industry in China, among which the gold-based catalysts have attracted broad attention. In view of the problems of high cost and poor stability of gold-based catalysts in industrial applications, their reaction and deactivation mechanism, and the influence of active component and support on their performance are discussed. The research progress of active component improvement and support modification is highlighted. Finally, the development and trends of carbon supported gold catalysts for acetylene hydrochlorination are prospected. We also point out that deeply studying the intrinsic reaction mechanism, simplifying the preparation and regeneration process, and exploring lower cost and high efficiency mercury-free catalysts and their industrialization will be the hotspots in this field.

Preparation of catalytic porous ceramic balls and catalytic pyrolysis of corn stover
LI Yufeng, WANG Shaoqing, ZHANG Andong, BI Dongmei, LI Zhihe, GAO Liang, WAN Zhen
2022, 41(7):  3597-3607.  doi:10.16085/j.issn.1000-6613.2021-1833
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In order to solve the problems of poor product quality in the process of biomass pyrolysis liquefaction, the research was based on the ceramic ball as a heat carrier, porous ceramic balls loaded with (ZnO, NiO, CeO2, Cr2O3, and Fe2O3) were produced, and the catalytic effect of porous ceramic balls catalyst in the pyrolysis process of corn stover was investigated on a fixed bed reactor. The results indicated that the prepared porous ceramic balls matrix had catalytic activity in the pyrolysis of corn stover. All modified porous ceramic balls could improve the production rate of bio-oil, and the Ni-based porous ceramic balls had the highest production rate of 41.62%. The five metal oxides supported by the porous ceramic balls could increase the content of phenols and furans obviously and reduce the acid substances in bio-oil and its types. Among them, the acid reduction effect of Ce-based porous ceramic balls was significant, with a reduction of 37.15%. The addition of catalytic porous ceramic balls promoted the production of C n H m (n≥2) in non-condensable gases, and among the olefins the ethylene increases the most, which was 50.53%. Meanwhile, the physicochemical properties of biochar were improved. The research would provide an important reference for the efficient preparation of liquid fuels and fine chemicals by the catalytic pyrolysis of biomass.

Preparation of Na2CO3 /CF solid base and its catalytic transesterification of rapeseed oil
ZHAO Jianbing, YANG Dan, SHU Yuancao, ZHU Junbo, PU Shiping, SONG Xiaodan, LIU Shouqing, CHAI Xijuan, LI Xuemei
2022, 41(7):  3608-3614.  doi:10.16085/j.issn.1000-6613.2021-1876
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With Na2CO3 as active component and carbon foam (CF) as carrier, solid base catalyst of Na2CO3/CF was prepared by volume impregnation method. Then, its structure and properties were characterized by SEM, SEM-EDS, FTIR, XRD, and BET. The specific surface area of the Na2CO3/CF catalyst was 182m2/g and the loaded Na2CO3 was evenly deposited on the cell wall surface of CF as fine grains with an average particle size less than 350nm. Subsequently, the catalytic activity and reusability of Na2CO3/CF were studied in the transesterification of rapeseed oil with methanol, and the process conditions were optimized. The optimal conditions were Na2CO3/CF dosage 10% (of oil weight), reaction time 180min, mole ratio of alcohol to oil 27/1, reaction temperature 65℃, and the resulting conversion was 97.80%. Moreover, the conversion still maintained 94.48% with the catalyst used for five times. The study would provide a new idea for the development of carbon-based solid base catalyst with high efficiency using the salt formed by strong base and weak acid as active center.

HPAs-modified V-Mo/Ti-W catalysts for the selective catalytic reduction of NO x over a wide temperature range
ZHOU Jiali, MA Ziran, ZHAO Junping, MA Jing, ZHAO Chunlin, LI Ge, WANG Hongyan, WANG Baodong
2022, 41(7):  3615-3623.  doi:10.16085/j.issn.1000-6613.2021-1888
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A series of Keggin heteropoly acid-modified V-Mo/Ti-W catalysts were prepared by incipient-wetness impregnation method and their physicochemical properties were investigated by using XRD, BET, NH3-TPD, H2-TPR, XPS and FTIR. The analysis indicated that heteropoly acid could inhibit the deposition of ammonium bisulfate by increasing the average pore diameter of the catalyst to improve its resistance to sulfur. Compared with V-Mo/Ti-W catalyst, the HPAs-modified V-Mo/Ti-W catalysts showed higher NH3 adsorption capacity, better reduction performance and more chemisorbed oxygen species, which provided better DeNO x performance and N2 selectivity. The HPAs-modified V-Mo/Ti-W catalysts exhibited high NH3-SCR activity and excellent SO2 resistance performance in a wide temperature range and almost 100% N2 selectivity in simulated atmosphere with high concentrations of SO2 and H2O and under 150000h-1 gas space velocity. Hence, the HPAs-modified V-Mo/Ti-W catalysts can be used as promising wide-temperature catalysts for deep peak shaving in coal-fired power plants.

Materials science and technology
Recent progress of key materials for flexible degradable pressure sensors
BAO Yan, ZHENG Xi, GUO Ruyue
2022, 41(7):  3624-3635.  doi:10.16085/j.issn.1000-6613.2021-1839
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At present, most flexible pressure sensors cannot be disposed and become electronic waste after used due to the using of no-degradable materials, which brings great pressure to the environment. With the development of science and technology, the emergence of biodegradable materials provide a huge opportunity for the reform of flexible pressure sensors. Flexible pressure sensors based on biodegradable materials have become a research hotspot because they play an important role in personal health management, medical monitoring, environmental monitoring and other fields, and they have great potential in reducing electronic waste and alleviating environmental problems. Based on this, the flexible degradable pressure sensors are divided into three types according to the key materials in this paper, which are sensors originated from degradable polymer substrates, sensors come from degradable conductive materials, and sensors produced by double degradation of polymer substrates and conductive materials. Moreover, the latest progress of three kinds of flexible degradable pressure sensors at home and abroad are reviewed. Firstly, the types of key materials and the preparation process of the above three sensors are briefly introduced. Secondly, the advantages, disadvantages and application fields of each type of sensor are summarized. Finally, the problems and development trends of flexible degradable pressure sensors are pointed out to provide reference for the development and application of flexible degradable pressure sensors.

Recent progress of moisture sorbent for adsorption-based atmospheric water harvesting
WANG Shengnan, CHEN Kang, ZHENG Xu
2022, 41(7):  3636-3647.  doi:10.16085/j.issn.1000-6613.2021-1651
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Adsorption-based atmospheric water harvesting is considered as one of the important technologies to solve the global water shortage problem because of its wide applicable environment and low-carbon environmentally friendly characteristics. Freshwater collected from this technology is intimately affected by properties of selected moisture sorbents. This paper summarizes recent research on sorbents. Hygroscopic polymers and composite adsorbents (including porous adsorbents-salt, polymer-salt, polymer-polymer and porous adsorbents-polymer) are focused. Besides, their properties and application in adsorption-based atmospheric water harvesting are analyzed. It is found that composite adsorbents (especially polymer based ones) had better adsorption capacities and are able to operate in a wide range of relative humidity, which can improve water harvesting in arid areas and have a vast application prospect. In the end, some valuable references for the developments and practical applications of the adsorption-based atmospheric water harvesting technology are provided.

Research progress on preparation technology of phase-change bidirectional temperature-regulating textile materials
GUO Zhi’an, SUI Zhihui, LI Yaping, XU Yikun, SUN Fang, ZHAO Xin
2022, 41(7):  3648-3659.  doi:10.16085/j.issn.1000-6613.2021-1652
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Phase-change bidirectional temperature-regulating textile materials are the product of the combination of the energy field and the textile industry, and has the advantage of automatic bidirectional temperature-regulation. From the perspective of preparation technology, this article introduces two major approaches: phase-change fiber preparation method and post-finishing method. Around the phase change fiber preparation method, the principle and application of microcapsule melt spinning method, microcapsule solution spinning method, electrostatic spinning method, PCMs composite spinning method and fiber hollow filling method are explained in detail. For the finishing method, the principle and application of filling method, coating method, printing method, pad-dry-cure method and grafting method are introduced in detail. The advantages and disadvantages of various preparation technologies are analyzed in order to deepen the knowledge and understanding of phase-change bidirectional temperature-regulating textile materials from the preparation technology. The advancement of preparation technology can improve the comprehensive performance of the phase-change bidirectional temperature-regulating textile material. How to prepare the phase-change bidirectional temperature-regulating textile material that to meet the requirements of wearing with excellent comprehensive performance is the key to its application. Finally, suggestions and prospects for the future research directions of phase-change bidirectional temperature-regulating textile materials are put forward in the hope of providing reference for the research of preparation technology of phase-change bidirectional temperature-regulating textile materials.

Design and preparation of porous liquids and their applications in CO2 adsorption
SHENG Lisha, CHEN Zhenqian
2022, 41(7):  3660-3675.  doi:10.16085/j.issn.1000-6613.2021-1678
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Porous liquids (PLs) come up with both liquid fluidity and solid porosity, thereby offering a variety of applications in such as gas sorption and separation, homogeneous catalysis, biomedicine. However, the problems of complex synthesis, organic solvent volatilization, high viscosity, precipitation after setting a long time and so on has restricted the further development and application of PLs. In this paper, the feasibility, stability, fluidity and carbon replenishment performance of PLs in their designing and preparation are discussed. PLs are classified into three categories. The methods and processes of PLs preparation and the effects of the core and canopy structures on the stability and fluidity of PLs are reviewed. Finally, the challenges in the preparation and synthesis of porous liquids are summarized, and their applications in gas adsorption and separation and other aspects are prospected.

Progress in preparation and application of superhydrophobic materials based on polyvinyl chloride
ZHU Xuedan, YAO Yali, MA Lili, WANG Jiaxin, YANG Jie, PENG Lei, HE Jinmei, QU Mengnan
2022, 41(7):  3676-3688.  doi:10.16085/j.issn.1000-6613.2021-1683
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Polyvinyl chloride (PVC) is one of the most widely used plastics in the world because of its excellent chemical and mechanical characteristics, the advantages of cheap accessible and widely used in medical equipment manufacturing, construction, food and electronic industries. PVC has a contact angle of 90° to water and is required to achieve superhydrophobic properties in applications such as biomedical and metal corrosion prevention. Therefore, the demand for PVC-based superhydrophobic materials has become increasingly urgent. In this paper, the classification, preparation methods and application fields of PVC-based superhydrophobic materials are reviewed. The different types, different preparation methods of hydrophobic performance of polyvinyl chloride based superhydrophobic material are compared. Finally, some problems of this field are summarized, mainly including that the preparation process is limited to laboratory operations, and the wear resistance, durability and mechanical strength of the materials need to be investigated, etc. The development direction of this field is pointed out: ①developing a simple, environmentally friendly, low-cost large-scale preparation processes; ②overcoming the weak points of poor thermal and light stability of PVC materials, carrying forward its advantages of good corrosion resistance and high mechanical strength, and further expanding the application range of PVC materials.

Layered double hydroxide (LDH) for phosphate removal
YANG Jing, FAN Yiyi, WANG Saidi, WANG Fukai, MENG Xiuxia, YANG Naitao, LIU Shaomin
2022, 41(7):  3689-3706.  doi:10.16085/j.issn.1000-6613.2021-1694
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Layered double hydroxide (LDH) is an excellent adsorbent for the removal of phosphate anions, which is featured by easy modification, adjustable surface charge, layer spacing controlling, strong adsorption capacity and fast adsorption rate, showing effectiveness to address the issues of eutrophication of water bodies. Proceeding from optimization of phosphate removal properties, this review summarizes the LDH structural features, adsorption mechanism, the frontier theories of the delamination and some application cases. Some challenges are pointed out including the easy aggregation, unstable colloidal solution, performance controlled by pH, as well as the difficulty to recycle LDH as the anion adsorbent. To solve these problems, some composite method and improving scheme for magnetic LDH, biochar/GO, GO(rGO)/LDH copositive materials are analyzed. LDH composite modification and LDH membrane materials are proposed as the new research trend and hot study. It is hopeful that this review can provide some new ideas for new researchers to begin their work in this area using LDH for applications in water treatment. Theoretically, it is general guidelines for the adsorption of phosphate anions on LDH and membrane separation performance.

Carbon fiber materials used for the electrode of electro-Fenton system: a critical review
XU Hu, GUO Hongkai, CHAI Changsheng, HAO Xiangzhong, YANG Ziyuan, XU Weijun
2022, 41(7):  3707-3718.  doi:10.16085/j.issn.1000-6613.2021-1779
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As a kind of advanced oxidation processes based on the electrochemistry method, electro-Fenton technology can indirectly generated ·OH radicals that can efficiently remove the organic pollution in water. Carbon fiber materials have the advantages of high volumetric area, low-density, corrosion-resistant, and so on. Motivated by these outstanding advantages, it has been employed for the electrode of Electro-Fenton system. This review primarily introduces the mechanism of electro-Fenton reaction, and then reviews the current situation of carbon fiber materials used for the electrode of electro-Fenton technology. The summary and analysis of the modification mechanism and forms of carbon fiber materials are the emphasis of this review, and the application advantage and limitation are point out. Meanwhile, the application of carbon fiber materials employed for anode is summarized. Finally, the industrialization problems, energy consumption problems and multi-functional electrode of carbon fiber materials used in the electro-Fenton system are analyzed and prospected, providing reference for the further study of this subject.

Infrared radiation control principle and its material research progress in thermal management application
HE Meiying, YUE Xuejie, ZHANG Tao, QIU Fengxian
2022, 41(7):  3719-3730.  doi:10.16085/j.issn.1000-6613.2021-1788
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The low utilization rate of traditional energy has exacerbated the environmental crisis, which emerges low-energy thermal management materials. This article introduces the principle of infrared radiation control technology, reviewes the research progress of selective radiation control materials in the fields of building thermal management and human thermal management, and summarizes the related research and application progress of the infrared properties of two types of materials. Radiation selective control materials realizes radiation temperature control by designing the optical characteristics of the surface structure and adjusting solar radiation. Building thermal management materials mainly include transparent coatings, pigment coatings and radiation coolers. Different building envelopes correspond to different performances. Walls and roofs use radiation coolers and pigment coatings with high solar reflectance and high infrared emissivity, while windows provide certain lighting for the interior and thus they also needed to have high solar transmittance. Human thermal management materials are mainly wearable fabrics, including radiant heat dissipation fabrics, radiant thermal insulation fabrics and smart radiant fabrics. In addition to corresponding radiation performance, it should also possess the flexibility, breathability and antibacterial properties of ordinary fabrics. Finally, this article looks forward to future research directions from the perspective of combining the performance of radiation control materials with practical applications.

Research progress on the preparation of lignin-derived adsorption materials and their application in wastewater treatment
ZHANG Lizhu, WANG Huan, LI Qiong, YANG Dongjie
2022, 41(7):  3731-3744.  doi:10.16085/j.issn.1000-6613.2021-1806
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Lignin is a kind of natural phenolic polymer widely existing in plants, which has the advantages of extensive sources, rich oxygen-containing functional groups and high carbon content. Lignin-derived adsorption materials with excellent performance can be obtained by modifying, compounding and pyrolysis carbonization of lignin, which has a wide application prospect in wastewater treatment. In this paper, the structure and properties of lignin, and the types and preparation methods of lignin based adsorbents are described. The modification methods of lignin based adsorbents are analyzed in detail, such as surface modification with metal ions and functional groups containing N, O, S and composite modification. The application of lignin-based adsorbents in the adsorption of dyes, drugs, heavy metals and other pollutants in wastewater is also reviewed. Finally, the current problems of lignin derived adsorbents are summarized, and it is prospected for the future research directions. How to realize the controllable preparation and large-scale production of lignin derived adsorbents and improve the applicability of adsorbents in the actual environment is the main research content in the future.

Nanofluidic channels based on two-dimensional material membranes
LI Peishan, ZHANG Mengchen, LI Mingjie, ZHENG Wenbiao, LIU Minchao, XIE Gaoyi, XU Xiaolong, LIU Changyu, JIA Jianbo
2022, 41(7):  3745-3757.  doi:10.16085/j.issn.1000-6613.2021-1852
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Nanofluidics involves unusual fluids motion in confinement with nanoscale characteristic dimensions. The emergence of a versatile family of two-dimensional (2D) materials and their membranes opens up a new horizon for nanofluidics studies. In this paper, it is started with a concise introduction to 2D materials and highlight how they can be engineered to construct nanofluidic channels by "top-down" strategy, "bottom-up" strategy and perforation strategy for preparing 2D porous membranes, and van der Waals assembly and solution-assisted assembly for preparing 2D laminar membranes. The methodologies of precise control of physical structures including channel size, length and morphology, and rational design of chemical environments including channel affinity and charge property of nanofluidic channels in 2D material membrane are discussed thereafter. Finally, the perspectives are provided to urgent challenges and potential opportunities in the fast-growing fields of 2D material membranes as well as nanofluidics for future research from aspects of material developing, biomimetic designing, mechanism exploring and device implementing.

Research progress on adsorbents of surface ion-imprinted polymer for heavy metal ions
CHI Chenglong, JIA Aizhong, SUN Daolai, ZHAO Xinqiang, WANG Yanji
2022, 41(7):  3758-3769.  doi:10.16085/j.issn.1000-6613.2021-1889
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Ion-imprinted polymer adsorbents display highly selective adsorption for template ions due to their strong recognition ability. However, the adsorption capacity and adsorption-desorption rate of ion-imprinted adsorbents prepared by traditional preparation methods are seriously restrained because the recognition sites of the materials are easy to deeply embed. Fortunately, the abovementioned problems can be effectively resolved by surface ion imprinting technology because all the fabricated adsorption active sites located on the surface are fully exposed to metal ions in solutions. The recent research progress of surface ion-imprinted polymer materials is summarized from three aspects of technical principles and raw materials, preparation technology and supporter in this paper. Aiming at the current status of relevant researches, the shortcomings and challenges in the development of surface ion-imprinted polymer adsorption materials are analyzed and discussed from the perspectives of carrier materials, functional monomers and target ions, and the development prospects and trends are prospected.

Preparation and electrochemical performance of lignin nanoparticles/natural fiber based activated carbon fiber materials
ZHANG Wei, AN Xingye, LIU Liqin, LONG Yinying, ZHANG Hao, CHENG Zhengbai, CAO Haibing, LIU Hongbin
2022, 41(7):  3770-3783.  doi:10.16085/j.issn.1000-6613.2021-1797
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This study was focused on the composite lignin nanoparticles (LNPs) loaded natural fibers, which was by KOH activation to prepare composite porous activated carbon fiber electrode materials. Then the as-prepared activated carbon fiber electrode was tested to evaluate the electrochemical performance in a three-electrode system. The results showed that the specific capacitance of KOH activated carbon fiber electrode material was 351.13F/g at the current density of 0.5A/g, which was much higher than that of non-activated carbon fiber electrode material (7.88F/g) and natural fiber activated carbon fiber material without LNPs (306.50F/g) under the same conditions. In addition, fiber surface loaded with LNPs formed porous activated carbon layer structure during the activation process, which further improved the cyclic stability of the composite activated carbon fiber material. Meanwhile, the abundant hydroxyl of LNPs endowed the composite material with additional pseudocapacitance. After 10000 cycles at a current density of 10A/g, the capacitive retention of the composite activated carbon fiber electrode was still at 95%, which was higher than that of the activated carbon fiber electrode of 87% without LNPs loading. The results indicated that lignin nanoparticles/ natural fiber based activated carbon fiber was an ideal electrode material for supercapacitors. This study also provided a new way for the high-value application of LNPs in biomass carbon fiber as energy storage electrode material.

Ball milled modified pyrolysis carbon adsorb sulfamethoxazole
HUANG Ping’an, XU Jun, YANG Yuxuan, PAN Yuhan, WANG Xinwen, HUANG Qunxing
2022, 41(7):  3784-3793.  doi:10.16085/j.issn.1000-6613.2021-1819
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Aiming at the problems of large particles of pyrolysis carbon, weak surface activity and poor adsorption capacity, a mechanical ball milling surface modification method was proposed, and the adsorption effect of pyrolysis carbon on sulfamethoxazole (SMZ) under different ball milling modification parameters was discussed. Using waste rubber continuous pyrolysis carbon as raw material, stainless steel ball milling was used to prepare ball milled carbon with different surface properties. The structure, surface properties and surface morphology of the pyrolysis carbon before and after ball milling were analyzed, and the SMZ adsorption before and after ball milling modification was compared. The results showed that the ball milling modification process can effectively improve the structure and surface properties of the pyrolysis carbon of waste tires. The pyrolysis carbon after the ball milling treatment for 2hours had the best adsorption effect on SMZ and the adsorption amount can reach 59.37mg/g. The adsorption kinetics was in line with the pseudo two-stage adsorption model.

Preparation and electrochromic properties of graphene oxide and TiO2-B composite films
XIONG Jian, XIA Liufen, YU Lei, FEI Anjie, XU Chu, CHEN Shengya, JIANG Guodong
2022, 41(7):  3794-3800.  doi:10.16085/j.issn.1000-6613.2021-1742
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At present, TiO2 thin films with one-dimensional nanostructures are mainly limited in the field of electrochromic materials such as small light modulation amplitude, long response time and poor cycle stability. To solve the above problems, B-type titanium dioxide nanotubes (TiO2-B) were compounded with graphene oxide by deposition method, and titanate nanotubes were obtained by hydrothermal method with TiO2 powder as raw material. Then, the graphene oxide composite B-type titanium dioxide nanotube electrochromic film (GO/TiO2) with high transparency, large light modulation range and excellent cycle performance was prepared on fluorine-doped tin oxide glass (FTO) substrate by deposition method. XRD, XPS, Raman, FESEM and HR-TEM were used to study the effect of graphene oxide content on the electrochromic properties of GO/TiO2 composite films. The results showed that when the mass ratio of GO to titanate nanotubes was 7%, the ion diffusion coefficient of GO/ TiO2 composite film was 1.46×10-8cm2/s and the coloring efficiency was 38.1cm2/C, indicating good electrochromic properties. At -1.6V and 633nm, the light modulation amplitude of GO/TiO2 electrochromic film can reach 77%, the coloring and bleaching time of GO/TiO2 film were 28.6s and 4.8s, respectively, and the light modulation amplitude retention rate after 100 cycles was 96.1%.

Carboxyl graphene composite membranes covalently crosslinked with diols and the n-butanol dehydration properties
HAN Guanglu, LU Kuan, LYU Jie, ZHANG Yonghui, CHEN Mohan
2022, 41(7):  3801-3807.  doi:10.16085/j.issn.1000-6613.2021-1896
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Covalently crosslinked carboxyl graphene/polyethersulfone (CG/PES) composite membranes were prepared by suction filtration. Polyethersulfone (PES) support was coated with dopamine hydrochloride. Diols(ethylene glycol, 1,3-propylene glycol and 1,4-butanediol) were used as crosslinking agents. The stability test showed that the coated dopamine hydrochloride improved the adhesion between the separation layer and the support layer. The diol crosslinking structure ensured the stability of the CG separation layer. The physicochemical properties and micro morphology of the composite membranes were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and water contact angle tester. The results indicated that the separation layer of the composite membrane was continuous and defect-free, and the thickness ranged from 60nm to 64nm. The diol reacted successfully with the carboxyl groups on the CG nanosheets and anchored the CG nanosheets together. The introduction of crosslinking agents did not significantly reduce the membrane hydrophilicity and realized the effective regulation of the d-spacing. With the increase of diol molecular size, the d-spacing of the composite membrane increased from 0.761nm to 0.778nm. CG/PES composite membrane exhibited excellent pervaporation separation performance for n-butanol/water mixture. When the feed temperature was 50℃ and the water mass fraction in feed was 10%, the permeation flux of the composite membrane obtained from the three crosslinking agents reached to 0.79kg/(m2·h), 0.87kg/(m2·h) and 0.96kg/(m2·h), respectively. The separation factor was one order of magnitude higher than that of the non-crosslinked composite membrane. The 15 day stability testing results showed that the separation performance of as-prepared composite membrane had no significant change and can meet the requirements of pervaporation application.

Microstructure and rheology of microporous layer ink for proton exchange membrane fuel cells
CHEN Zhekun, PAN Weitong, YAO Dingsong, DING Lu, WANG Fuchen
2022, 41(7):  3808-3815.  doi:10.16085/j.issn.1000-6613.2021-1856
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The microporous layer (MPL) is an important component of water management in proton exchange membrane fuel cells (PEMFC). It is crucial to gain an in-depth understanding of MPL ink, which determines MPL's structure and performance. In this paper, four typical carbon blacks [ACET, XC-72R, BP2000, and natural gas cracking carbon black (NG)] were selected to systematically study the microstructure of the slurry by using atomic force microscopy (AFM), field emission transmission electron microscopy (TEM) and dynamic light scattering particle size analyzer (DLS PSD). Agglomeration was proposed as an ink evaluation criterion, and quantitative criteria were also given by combining rheology study. The results showed that the agglomeration degree of different carbon blacks was in the following order: ACET>XC-72R>BP2000>NG. The larger the shear thinning index n, the lower the agglomeration degree of MPL slurry and the more uniform the particle dispersion, and the smaller the n, the higher the agglomeration degree. Specifically, for the solid content α=6%, nNG-MPL =0.554, nBP2000-MPL =0.320, nXC-72R-MPL =0.118, and nACET-MPL =0.039. The measured agglomerates particle sizes of ACET, XC-72R, BP2000 and NG were 1.358μm, 1.149μm, 0.732μm and 0.406μm, respectively. So the shear thinning index of the ink should be inversely proportional to the degree of agglomeration. In conclusion, NG-MPL has the lowest shear thinning degree and is a more suitable carbon material for MPL, which also provides guidance for the preparation and optimization of MPL in the future.

Biochemical and pharmaceutical engineering
Effect of flow field on the CO2 reduction performance and products of MEC biocathode
XU Pei, JIA Xuan, WANG Yong, QI Xuejiao, ZHAO Yujiao, LI Mingxiao
2022, 41(7):  3816-3823.  doi:10.16085/j.issn.1000-6613.2021-1715
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This study focused on the issue of low CO2 reduction rate on the biocathode in microbial electrolysis cells (MECs). By changing the flow field environment of cathode chamber, the effect of flow field on the start-up, operation, products transformation and functional microorganism on the biocathode were explored. Furthermore, the response of CO2-reduction biocathode performance of MEC to flow field was clarified. The results showed that the flow field enhanced the ability of CO2-reduction of biocathode (electronic consumption increased by 10%, of which CO2 to acetic acid pathway consumption increased by 30%), and changed the CO2 reduction pathway of biocathode (from methane production in the start-up stage to acetic acid production in the operation stage). The high-throughput analysis showed that the flow field changed the microbial community structure of the biocathode and catholyte, making the biocathode dominated by the hydrogenotrophic methanogens (Methanobacterium) to that by the acetoclastic methanogens (Methanosaeta).The abundance of acetogenic bacterial communities (Petrimonas, Candidatus_Caldatribacterium) increased by 3.8% compared with the control group, which played an important role in the process of CO2-reductionforacetic acid production. This research aims to provide theoretical and technical support for the directed regulation of MEC reduction of CO2 to produce acetic acid.

Fine chemicals
Process optimization and design of eliminating domestic agar phosphate precipitation
DUAN Boyan, NI Hui, LI Zhipeng, JIANG Zedong, ZHU Yanbing, LI Qingbiao
2022, 41(7):  3824-3831.  doi:10.16085/j.issn.1000-6613.2021-1682
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Agar is an important gel matrix for the preparation of microbial medium. Currently, phosphate precipitation is an inevitable problem in the preparation of microbial media using domestic agar, which has effected the accuracy of microbial experiments such as colony calculation. In order to solve this problem, we took turbidity and transparency as evaluation indexes to compare the elimination effects of adsorption method, masking agent method and chemical precipitation method on phosphate precipitation of Sigma agar, domestic agar strip and domestic agar powder, designed the optimized process and analyzed its economic feasibility. The experimental results showed that adsorption method and masking agent method had a certain impact on the transparency and turbidity of the three agars, but the quality of the products could not meet the standard of microbial culture medium configuration. Sigma agar and domestic agar strips were treated by potassium dihydrogen phosphate precipitation method, the agar transparency was increased to more than 94%, and the turbidity after phosphate treatment was reduced to 20NTU, which met the biochemical agar product standard for microbial culture medium. The process of treating domestic agar strips by potassium dihydrogen phosphate precipitation method was designed. The results showed that the total investment profit rate of domestic biochemical agar with an annual output of 1000t was 64.01%, and the static investment payback period was 3.3 years. The results showed that the treatment of domestic agar strips by potassium dihydrogen phosphate precipitation method could significantly eliminate phosphate precipitation, the product quality meets the configuration requirements of microbial culture medium, and it is economically feasible, which provides a technical reference for the removal of domestic agar phosphate precipitation and the production of agar products of microbial culture medium.

Preparation and application of polyacrylamide porous hydrogel by high internal phase emulsion polymerization
CHANG Wei, SHI Qiulan, ZHAO Zhengyang, WANG Ruiting, WANG Zhifu, ZHAO Jianbo
2022, 41(7):  3832-3839.  doi:10.16085/j.issn.1000-6613.2021-1793
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Hydrophilic silica nanoparticles (N20) and emulsifier Tween80 were used as composite stabilizers and cyclohexane as oil phase to prepare high internal phase emulsions (HIPEs). Polyacrylamide (PAM) porous hydrogel was prepared by polymerizing acrylamide in the outer phase with this emulsion as template. The optical microscope photographs of HIPEs and the SEM images of PAM porous hydrogel showed that the amount of N20 and Tween80 affectted the pore appearance and diameter of the material. Mercury injection apparatus results showed that the average pore size of porous hydrogel was 38.06nm, the porosity was 77.54%, and the saturated water absorption rate of 20h reached 402g/g when the dosage of N20 was 3% and Tween80 was 9%. Adsorption experiments showed that PAM porous hydrogel has good adsorption properties for Mn(Ⅱ). The adsorption process conforms to the quasi second-order kinetic equation and belongs to chemical adsorption. When the solution pH was 4, the adsorption saturation reached in 120min and the adsorption amount was 474.64mg/g.

Resources and environmental engineering
Research progress of SO2 removal by solid adsorbents
WU Chuanpeng, LI Chuankun, YANG Zhe, GOU Chengdong, GAO Xinjiang
2022, 41(7):  3840-3854.  doi:10.16085/j.issn.1000-6613.2021-1835
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SO2 Emission has become an important issue, due to the harmful impact on human health and the ecological environment. Adsorption is an effective SO2 removal method that could avoid producing sulfur-containing waste water and realize the recycling of sulfur resources. Adsorption materials play the key role in the design and development of the adsorption system. In this paper, researches about SO2 removal by solid adsorption materials are reviewed and their adsorption performance, mechanisms and shortcomings are analyzed. Finally, the main problems for SO2 removal by adsorption are proposed to provide references for the development of adsorption desulfurization technology. It is suggested that the future adsorption purification of flue gas should be towards simultaneous removal of various flue gas impurities.

Application of municipal solid waste incineration fly ash in the field of pollutant control
QIU Qili, JIANG Xuguang
2022, 41(7):  3855-3864.  doi:10.16085/j.issn.1000-6613.2021-1673
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With the popularization and application of municipal solid waste (MSW) incineration technology, there is an increasing generation of MSW incineration fly ash. Meanwhile, the decrease of landfill resources has drawn much attention to the comprehensive utilization of fly ash. Since fly ash is rich in active substances, such as silica and alumina, it has a good application prospect in the field of adsorption and removal of wastewater and gas pollutants. Combined with the physical and chemical characteristics of fly ash, the pollutant adsorption and removal effect of in different wastewater and waste gas are reviewed in this paper. Based on the research of pollutant removal in recent years, the application effect and mechanism of original and modified fly ash in the removal of heavy metals, phosphate, dyes and other pollutants are emphatically introduced. Meanwhile, the main existing problems of different application processes are also pointed out, and the cost analysis, relative merits are compared. Finally, suggestions and prospects are put forward for further study on the application of microwave hydrothermal technology in improving the adsorption of fly ash and the whole process research of the application of fly ash in the field of pollutant control.

Current situation and development trend of NO x and dioxins emission reduction in sintering flue gas
LONG Hongming, DING Long, QIAN Lixin, CHUN Tiejun, ZHANG Hongliang, YU Zhengwei
2022, 41(7):  3865-3876.  doi:10.16085/j.issn.1000-6613.2021-1650
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The sintering process is an important step in the production chain of the iron and steel industry but it is also the main emission source of sulfur dioxide, nitrogen oxide, and dioxin in the atmosphere. With desulphurization technology becoming mature, the reduction of nitrogen oxides and dioxins has become the top priority of emission reduction for sintering flue gas. In this paper, the new regulations and relevant standards for emission reduction of multiple pollutants in sintering flue gas are introduced. The latest research progress and industrial application status of nitrogen oxides and dioxins reduction in sintering process are reviewed from the three aspects of source control, process reduction and end treatment. Moreover, it is proposed that adopting the whole process multi-technology coupling mode is the development direction to realize the multi-pollutant emission reduction of sintering flue gas at low cost. Under the new development requirement of "carbon emission reduction" in the iron and steel industry, the research challenge of low-temperature denitrification/dioxin catalysts for sintering flue gas is summarized. Finally, this paper prospects the future research directions of improving the water and sulfur resistance for the low-temperature catalysts.

Research progress on catalytic cracking of waste tires
YANG Chao, JIAO Qingze, FENG Caihong, ZHAO Yun
2022, 41(7):  3877-3889.  doi:10.16085/j.issn.1000-6613.2021-1910
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Huge amounts of waste tires are difficult to degrade and they pollute the environment. Therefore, waste tires are thought as a kind of black pollution. Catalytic cracking is an important means for the treatment of waste tires, which can not only achieve efficient conversion and resource utilization but also obtain high value-added chemical products, such as monocyclic aromatic hydrocarbons, light olefins and limonene. In this paper, the distribution characteristics of catalytic cracking products of waste tires are discussed from the aspects of physical structure and chemical composition, catalytic cracking process and characteristics of cracking products, reactor types and characteristics, catalyst types and functions, and process conditions. By comparing the effects of reactors, catalysts and process conditions on the product distribution, the existing problems for the industrialization of catalytic cracking of waste tires are further analyzed. According to the current research situation of catalytic cracking of waste tires, it is proposed that reactors and supporting processes suitable for large-scale treatment should be designed, and catalysts with high stability and high selectivity for specific products should be developed at the same time. The resource utilization of waste tires characterized by low energy consumption, high conversion and high added value is then realized.

A novel anaerobic hydrolysis acidification-partial denitrification anaerobic ammonia oxidation process for advanced nitrogen removal from simulated domestic and nitrate-containing wastewater
WANG Chaochao, WU Yiling, CHEN Jiaqiao, CAI Tianning, LIU Wenru, LI Xiang, WU Peng
2022, 41(7):  3890-3899.  doi:10.16085/j.issn.1000-6613.2021-1775
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A new anaerobic hydrolytic acidification (AnHA)-partial denitrification anaerobic ammonia oxidation (PD/A) process was constructed to realize the simultaneous and efficient treatment of simulated domestic sewage with low carbon nitrogen ratio and low concentration nitrate wastewater. By controlling the influent NO3--N/NH4+-N=1.2 and COD/TN=2.36, and adjusting the subsection influent ratio of domestic sewage to 3∶7 and AnHA reactor HRT=3.2h, AnHA-PD/A system had achieved 94.78% TN removal, and the corresponding effluent TN concentration was only 5.47mg/L, which was far lower than the level A discharge standard of urban sewage treatment plants in China. During the stable operation, PD-Anammox process was the most important nitrogen removal process in the AnHA-PD/A system, whose contribution rate to TN removal was as high as 95.87%. The results of gas chromatography showed that acetic acid, as the main organic component of AnHA effluent (43.65%), that is, high-quality carbon source supply, greatly promoted the supply process of NO2--N in the PD/A system. Microbial high-throughput sequencing showed that Commonas and Omatilinea, as the hydrolysis and acidification bacteria with the highest relative abundance in the AnHA system, played an important role in the degradation and acid production of macromolecular organics, with corresponding abundances of 2.97% and 3.74% respectively, and the main dominant functional bacteria in the PD/A system were CandidatusBrocadia and Thauera, with corresponding abundances of 2.93% and 7.37% respectively.

Rapid start-up and nitrogen removal performance of anammox process using activated sludge as an inoculation
CHEN Jiabo, ZHOU Xin, LI Xu
2022, 41(7):  3900-3907.  doi:10.16085/j.issn.1000-6613.2021-1776
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Rapid start-up of biofilm-anammox process for low-strength wastewater in anaerobic sequencing biofilm batch reactor (AnSBBR) with activated sludge as inoculum and highly efficient performance have been achieved. According to the operation effect, the key control factors such as influent dissolved oxygen (DO) and hydraulic retention time (HRT) were adjusted to accelerate the rapid formation of biofilm-anammox process. The results showed that the start-up of anammox was achieved. After 90 d of operation, the nitrogen removal efficiency (NRE) and nitrogen removal load rate (NRLR) reached 99.7% and 0.048kg/(m3·d), respectively. The microbial community analysis showed that anammox bacteria were mainly Candidatus Brocadia and Candidatus Kuenenia, and the relative abundance reached up to 12% at 168d, indicating that anammox bacteria became the dominant genera in biofilm. Biofilm images and scanning electron microscope (SEM) results showed that anammox mainly existed in the biofilm inside the biocarrier, and biofilm-anammox structure was formed by multiple small polymers, mostly cocci and closely.

Effect of magnetic nanoparticles type and mass concentration on microwave pyrolysis of oily sludge
JIANG Huayi, HU Juan, QI Hongyuan, YOU Yanzhen, WANG Yulong, WU Zhe
2022, 41(7):  3908-3914.  doi:10.16085/j.issn.1000-6613.2021-1914
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In view of the problems of low pyrolysis efficiency and high treatment cost when traditional microwave absorbent is used in the synergistic microwave pyrolysis of oily sludge, this paper introduced magnetic nanoparticles as a new microwave absorbent to explore the effects and rules of the type and mass concentration of magnetic nanoparticles in the enhancement of microwave pyrolysis of oily sludge. The experimental results showed that in the six magnetic nanoparticles (ZnFe2O4, Fe3O4, Ni, NiFe2O4, γ-Fe2O3 and Co3O4), the final pyrolysis temperature of the experimental group adding ZnFe2O4 was up to 284℃, and the gas and liquid products were 382mL and 10.5mL, respectively. When the microwave power was 800W and the microwave heating time was 20min, the final pyrolysis temperature of the experimental group adding nano-ZnFe2O4 was the highest at the mass concentration of 5.0mg/g. In addition, with the increase of nano-ZnFe2O4 mass concentration, the contents (volume fraction) of H2, CH4 and C2H6 in the gas phase pyrolysis products increased, while the contents of C x H y and CO2 decreased. The contents of C4—C12 components in the oil phase products increased gradually, and the contents of C18+ components decreased gradually. The contents of C13—C18 components increased at first, then decreased and at last increased a little with the increase of the concentration of ZnFe2O4.

Synthesis of 2-pyridinecarboxaldehyde functionalized SBA-15 mesoporous material for the adsorption of Cr(Ⅲ) ions from aqueous solution
JIANG Xiaoqing, GUO Yu, WU Hongmei
2022, 41(7):  3915-3924.  doi:10.16085/j.issn.1000-6613.2021-1827
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A novel functionalized SBA-15 material (N-SBA-15) was synthesized via Schiff's base reaction of 2-pyridinecarboxaldehyde with amino modified SBA-15 mesoporous material for adsorption of Cr(Ⅲ) ions from aqueous solution. The organic functional groups, morphology, pore structure and chemical property of N-SBA-15 were determined by FTIR, XRD, EDX, SEM, TEM, XPS, TGA and N2 adsorption-desorption. Moreover, the adsorption performance of N-SBA-15 adsorbent on Cr(Ⅲ) ions in aqueous solution was investigated. The adsorption capacity of 84.3mg/g toward Cr(Ⅲ) ions was obtained. The kinetics analysis and adsorption isotherms revealed that the adsorption process of Cr(Ⅲ) ions by N-SBA-15 was consistent with pseudo-second-order kinetic model and Langmuir isotherm model. The thermodynamic parameters showed that Cr(Ⅲ) adsorption onto N-SBA-15 was spontaneous, endothermic and entropy-increasing process (?G<0, ?S>0, ?H>0). The adsorption mechanism analysis indicated that Cr(Ⅲ) adsorption onto N-SBA-15 was mainly based on the chemical combination of N atoms on the organic functional groups of N-SBA-15 through coordination bond. Furthermore, N-SBA-15 still kept high adsorption capacity after five adsorption–desorption cycles.

Preparation of xanthate-functionalized cross-linked baker's yeast and its adsorption characteristics for Pb(Ⅱ)
DUAN Zhengyang, HU Ningmeng, LI Tianguo
2022, 41(7):  3925-3937.  doi:10.16085/j.issn.1000-6613.2021-1900
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Xanthate-functionalized cross-linked baker's yeast (XCBY) was prepared by a two-step method and applied to remove Pb(Ⅱ) from aqueous solutions. The physicochemical characteristics of non-modified baker's yeast, XCBY and Pb(Ⅱ)-loaded XCBY were characterized by SRA, SEM, EDS, FTIR, XRD, and XPS. The impacts of operating parameters of pH, adsorbent dosage, initial concentration of Pb(Ⅱ) on the adsorption performance of XCBY were systematically investigated, and the adsorption kinetics, isotherm, thermodynamics and regeneration performance of XCBY were discussed. The results showed that the original baker's yeast had no significant change in cell morphology after crosslinking and xanthic acid modification, and its adsorption performance for Pb(Ⅱ) was significantly improved. Pseudo-second-order and Langmuir isotherm models effectively described the adsorption behavior of XCBY, and the thermodynamic analysis revealed that the adsorption process of Pb(Ⅱ) onto XCBY was spontaneous and endothermic. The adsorption process for Pb(Ⅱ) reached equilibrium at 30℃ in 40min with a maximum adsorption capacity of 319.91mg/g from the Langmuir isotherm model. Additionally, the adsorption mechanism of Pb(Ⅱ) on XCBY mainly depended on the coordination of —NH2, ion exchange of —OH and complexation of —C($????????$S)—S-. As a facile and economical chemical modification method of baker's yeast, the modified material was a potential and prospective adsorbent for use in the treatment of heavy metal-bearing wastewater.

Optimization of Pd/AC preparation conditions for catalytic reduction of dilute nitric acid
ZHENG Min, XU Lei, CHEN Chen, XU Zhongning, FU Minglai
2022, 41(7):  3938-3946.  doi:10.16085/j.issn.1000-6613.2021-1913
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One of the nitrogen sources in water is the excessive discharge of nitrogen-containing compounds by chemical industry, such as nitric acid. A large amount of nitric acids produced in the process of coal to ethylene glycol as by-product could be further converted to methyl nitric through catalytic reduction. This strategy could realize resource recycling, reduce nitrogen input in water, and control the occurrence of entrophication in water bodies. Activated carbon supported Palladium (Pd/AC) catalyst can effectively increase the conversion of nitric acid. In this study, Pd/AC was prepared by impregnation method, and characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), physical adsorption, and X-ray photoelectron spectroscopy (XPS). The effects of calcination and reduction condition on the structure of material and catalytic reduction activity of nitric acid were investigated to optimize the preparation conditions. The results indicated that with the increase of the calcination temperature, and the extension of the calcination time and the reduction time, the Pd particle size and the ratio of elemental palladium to oxidized palladium (Pd∶PdO) were increased, while the specific surface area and pore volume both decreased, which would lower the catalytic activity.

Design and performance analysis of mechanical vapor recompression salt fractionation evaporation crystallization system
JIANG Hua, ZHANG Zihui, GONG Wuqi, CHANG Yueyong
2022, 41(7):  3947-3956.  doi:10.16085/j.issn.1000-6613.2021-1619
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Multi-component high salinity wastewater treatment by salt fractionation crystallization technology can realize resource utilization of wastewater. The solubility of sodium sulfate and sodium chloride varies with temperature. To solve the above issue, mechanical vapor recompression(MVR) salt fractionation evaporation crystallization system was proposed. The proposed system was based on a falling film evaporator as a pre-evaporator, combined with two forced circulation evaporators, which can separate sodium sulfate and sodium chloride from wastewater by crystallization and recover condensate. After designing the specific process flow, mathematical model of the proposed system was established according to balance relationship of mass and energy and validated by experimental data. Taking mixed solution with sodium sulfate concentration of 5% and sodium chloride concentration of 8% at atmospheric pressure as an example, the model was calculated by Matlab software. A five-effect evaporation salt separation system was introduced as a contradistinction system. Based on energy and exergy analysis, the results showed that MVR salt fractionation evaporation crystallization system was much more energy-efficient. Its coefficient of performance (COP) was 93.5%, higher than that of the contradistinction system. Its unit energy consumption was 77.6%, lower than that of the contradistinction system. Meanwhile, MVR salt fractionation evaporation crystallization system had higher thermodynamic perfectibility. Its exergy efficiency was 70.4%, higher than that of the contradistinction system, and exergy loss was 33.6%, lower than that of the contradistinction system.

Effect of cation on hydrothermal crystallization of desulfurized gypsum whiskers in chloride system and its mechanism
WANG Xiao, JIN Biao, ZHANG Xiaoting, ZHANG Jianwu, WANG Yubin, YUAN Dongdong, YANG Liushuan
2022, 41(7):  3957-3965.  doi:10.16085/j.issn.1000-6613.2022-0099
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Using pretreated desulfurized gypsum as raw material, and NaCl, CuCl2 and AlCl3 as additives, desulfurized gypsum whiskers were prepared by hydrothermal method in order to explore the effect of cations on their crystallization regulation. The study focused on the effect of cations on the crystal of desulfurized gypsum whiskers in the presence of Cl- and their mechanism. The results showed that Na+, Cu2+, Al3+ could affect the microstructure, aspect ratio and quality of desulfurized gypsum whiskers, but the effect of Cu2+ was more significant. Cu2+ could chemically adsorb on (200), (400) and (020) crystal faces of the crystal of whisker to form a CuSO4 film, which hindered its radial growth. At the same time, a little of Cu2+ could replace Ca2+, thereby promoting the desolvation of Ca2+, which caused an increase of the whisker aspect ratio to 200. However, both Na+ and Al3+ acted on (200), (400) and (020) crystal faces through physical adsorption and hindered the radial growth of desulfurized gypsum whiskers. In addition, Al3+ reacted with OH- in the solution to generate Al(OH)2+ and Al(OH)2+, and they were adsorbed on the (200), (400) and (020) planes with negative charges, which reduced surface energy of the above planes and also promoted the growth of desulfurized gypsum whiskers along the c-axis.

Products prediction of carbon-based solid waste pyrolysis based on FUSION model
YANG Lei, SONG Jinling, TANG Chuyang, YU Shiyao, YANG Xinyu
2022, 41(7):  3966-3973.  doi:10.16085/j.issn.1000-6613.2021-1720
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Low-temperature pyrolysis is a promised method for cleanly converting carbon-based solid waste, achieving carbon sequestration and reducing emissions. By establishing a mathematical model for predicting the yields of carbon-based solid waste pyrolysis products, the time for scientific research and exploration can be greatly shortened, and the pyrolysis reaction process can be optimized and controlled. In this paper, 80 sets of pyrolysis experimental data as samples were used. The neural network (ML), support vector machine (SVM) and linear regression (LR) models were firstly trained and tested to analyze the effectiveness of machine learning, and then the three models through algorithm fusion, an adaptive FUSION model (FUSION) was established. At last, the model was further trained and tested with experimental data to form a data model suitable for predicting carbon-based solid waste pyrolysis products. The FUSION model can effectively solve the problem that a single model is affected by the interaction of pyrolysis in the process of predicting the distribution of carbon-based solid waste pyrolysis products, and the prediction accuracy fluctuates. Meanwhile, the predicted value of this model has high accuracy, and the relative error between the predicted value and the experimental value is less than 2%.

Emission characteristics and photochemical reactivity of volatile organic compounds from petrochemical intermediate storage tanks
CAO Dongdong, LI Xingchun, XUE Ming
2022, 41(7):  3974-3982.  doi:10.16085/j.issn.1000-6613.2021-1842
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Petrochemical intermediate storage tanks are key volatile organic compounds (VOCs) emission sources which play vital roles in regional air pollution and abatement. During the working loss process, the intermediate product tank vents of refining and petrochemical processes and waste oil tanks in a petrochemical facility were sampled and measured in this study. The emission characteristics of VOCs were analyzed and speciated source profiles for specific sources were developed. The ambient photochemical reactivity were developed based on the value of OH loss rate. By virtue of the maximum increment reactivity method, ozone formation potential of sources were determined. The results suggested that level of VOCs from working loss process reaches tens of thousands mg/m3, and the corresponding emission strength ranged from 0.55g/m3 to 71.3g/m3 per material turnover. The VOCs emission characteristics differed among specific tanks, with refining process related tank and waste oil tank dominant in alkane and petrochemical tank prevailing in alkene and aromatics. The C3—C7 alkane, C3—C4 alkene, benzene, toluene and acetone were ranked as primary pollutants with highest weight percentage. The intermediate storage tank vented VOCs features in relative high photochemical reactivity (1.43×104—2.37×106s-1) and OFP (2.84×105—7.53×107mg/m3), with waste oil tank of delayed coking process having the lowest value and heavy oil product of ethylene cracking process the highest value. The alkane and alkene were found to contribute mostly to VOCs related photochemical reactivity and OFP during the working loss process. The C6—C7 alkane such as methylpentane, hexane and methylcyclohexane, C3—C5 alkene, and xylene were recommended to give preferred control priority.

Steel slag stability treatment and free oxide activation utilization in the production of autoclaved building material
ZHENG Qi, ZHANG Yuting, ZHAO Fengqing
2022, 41(7):  3983-3989.  doi:10.16085/j.issn.1000-6613.2021-1807
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The stability treatment of steel slag often leads to the loss of cementitious activity. Therefore, the modified additives were used to eliminate the hydroxides produced in the hydration process of steel slag and generate cementitious products, so as to realize the stability treatment of steel slag and the active utilization of free oxides in the production of autoclaved building materials, and avoid the loss of active substances caused by the separate disposal of steel slag. The results showed that the autoclaved tailings-steel slag samples produced with 8% straw ash and 3% ammonium dihydrogen phosphate as modifier had a stable volume with compressive strength of 24.0MPa. The digestion rate of free oxides, the amount of chemically bound water, thermogravimetry and XRD analysis were performed for the samples, and the stability treatment and activation mechanism of steel slag was proposed: the siliceous material combines with the Ca(OH)2 generated by the hydration of f-CaO in the steel slag to quickly generate C—S—H, which is good for the mechanical strength of the system, avoiding the volume expansion caused by the accumulation of Ca(OH)2; NH4+ and H2PO42- in phosphate combines with f-MgO to generate magnesium ammonium phosphate and other low-solubility complex salts, thereby eliminating the hidden danger of volume expansion caused by f-MgO hydration to generate Mg(OH)2. After the sample was autoclaved at 180℃ for 4h, the digestion rates of f-CaO and f-MgO could reach 86.28% and 89.73%, respectively. This technology will provide a basis for the production of autoclaved building materials by using steel slag to replace cement and lime in a large proportion, and is of great value for improving the utilization rate of steel slag and reducing carbon emission.