Central heating supply method of large scale absorption CHP based on st-hp

doi:10.16085/j.issn.1000-6613.2019-0710

Abstract

Abstract:

This paper proposed a screw turbine-heat pump (st-hp) cogeneration heat supply method to exploit the residual heat and pressure utilization potential of the steam-water system to achieve better energy-saving effect and higher heating power. Based on the second law of thermodynamics and the theory of entranspy, the exergy and entranspy analysis of the main newly added components under variable operating conditions were carried out. Using the IPC exhausting, the heating capacity was improved by means of “extra pressure for electric and residual heat for heating”. Absorption heat exchanger located in the thermal station was designed by algorithm to enlarge the temperature difference of the network water and the model was verified. A 600MW unit was used as an example to analyze the exergy and entranspy efficiency of new main heating elements in the power plant side under variable operating conditions using Ebsilon software. The results showed that st-hp system can not only increase the heat capacity of the municipal heat network by 50% without enlarging output of the boiler, but also meet the part demand of the plant. The energy-saving research of absorption heat pump and peak heater shall focus on improving the perfection of thermal cycle to reduce exergy loss. Screw turbine and peak heater should focus on improving the coordinative degree of working fluid velocity field and temperature field in heat transfer process. The operating conditions have a great influence on the thermal economy of the unit. When the thermal load is different, the minimum and maximum values of coal consumption for power generation are -5g/(kW·h) and 22.97g/(kW·h) respectively.

Key words: thermodynamics, cogeneration, waste heat and pressure utilization, exergy efficiency, entranspy efficiency, heat transfer, model

摘要：

提出基于螺杆膨胀机-热泵（st-hp）的热电联产供热方法来挖掘汽水系统的余热余压利用潜力，实现了更好的节能效果和更高的供热功率，基于热力学第二定律和理论对主要新增元件在变工况下进行了?分析和分析。通过让中压缸排汽“余压发电、余热采暖”的手段提高集中供热能力；利用算法设计热力站处吸收式换热装置以提升一次热供回网水温差，并予以模型验证；以某600MW机组为算例，利用Ebsilon软件分析变工况下电厂侧新增主要供热元件效率和效率。结果表明：st-hp系统不仅能在不增加市政热网运输管径和机组出力的同时使供热量提高50%，而且满足部分厂用电需求；吸收式热泵和尖峰加热器的节能研究重点是提高热力循环的完善程度以减少?损；螺杆膨胀机和尖峰加热器应着重于提高传热过程中工质的速度场和温度场协同程度。运行工况对机组热经济性影响很大，热负荷不同时，发电煤耗率极差极小值和极大值分别为-5g/(kW·h)和22.97g/(kW·h)。

关键词: 热力学, 热电联产, 余热余压利用, ?效率, 效率, 传热, 模型

CLC Number:

TK123

Haochen LIU,Zhi GENG,Yujiong GU. Central heating supply method of large scale absorption CHP based on st-hp[J]. Chemical Industry and Engineering Progress, 2020, 39(2): 468-477.

刘浩晨,耿直,顾煜炯. 基于膨胀机-热泵（st-hp）的大型吸收式热电联产机组集中供热方法[J]. 化工进展, 2020, 39(2): 468-477.

Figures/Tables 12

参数	文献[6]	本文	绝对误差	相对误差/%
热力站一次热网水供水温度/℃	130	115	15.00	11.54
一次热网水回水温度/℃	25	25	0.00	0.00
二次热网回水温度/℃	48	45	3.00	6.25
二次热网供水温度/℃	60	68	8.00	13.33
电厂侧单效吸收式热泵COP	1.75	1.68	0.07	4.00
热网供热能力提高的份额/%	75.0	66.6	8.33	11.11

序号	项目	流量/t·h^-1	温度/℃	压力/MPa	比焓/kJ·kg^-1
1	锅炉主蒸汽	1782.0	566.0	24.200	3398.8
2	锅炉再热蒸汽	1521.1	566.0	3.769	3598.9
3	中压缸排汽	1302.5	373.2	1.059	3206.4
4	用于采暖的中压缸排汽抽汽	302.3	373.2	1.059	3206.4
5	螺杆膨胀机进汽	43.2	373.2(t_i)	1.059	3206.4
6	螺杆膨胀机排汽	43.2	183.2(t_o)	0.200	2836.9
7	热泵发生器驱动热源出口水	43.2	120.0(T_g,o)	0.005	83.9
8	尖峰加热器蒸汽热源进口	259.1	373.2(T_r,i)	1.059	3206.4
9	尖峰加热器热源冷凝水出口	259.1	182.4(T_r,o)	1.059	773.8
10	一次热网回水	1980.0	20.0(T_a,i)	0.120	84.0
11	一次热网水中间点	1980.0	44.2(T_c,o)	0.120	185.0
12	尖峰加热器一次热网水进口	1980.0	44.2(T_l,i)	0.800	185.9
13	尖峰加热器一次热网水出口	1980.0	120.0(T_l,o)	0.800	504.2
14	热泵蒸发器低温热源入口水	1872.0	31.0	0.100	130.0
15	热泵蒸发器低温热源出口水	1872.0	20.7	0.100	86.7

序号	项目	流量/t·h^-1	温度/℃	压力/MPa	比焓/kJ·kg^-1
1	一次热网供水	1998.0	115.0(t₃)	0.78	483.03
2	进换热器的一次热网供水	1998.0	85.0(t₂)	0.78	356.58
3	出换热器的一次热网供水	1998.0	50.0(t₁)	0.78	210.00
4	一次热网回水	1998.0	25.0(t₀)	0.78	105.55
5	二次热网回水	7818.3	45.0( $t 0'$ )	0.65	188.99
6	进换热器的二次热网回水	2325.6	45.0( $t 0'$ )	0.65	188.99
7	出换热器的二次热网回水	2325.6	75.0( $t 4'$ )	0.65	314.52
8	二次热网供水	7818.3	68.0( $t 3'$ )	0.65	285.19
9	进热泵吸收器的二次热网回水	5492.7	45.0	0.65	188.99
10	进热泵冷凝器的二次热网回水	5492.7	60.0( $t 1'$ )	0.65	251.71
11	出热泵冷凝器的二次热网回水	5492.7	65.0( $t 2'$ )	0.65	272.63

序号	项目	流量/t·h^-1	温度/℃	压力/MPa	比焓/kJ·kg^-1
1	一次热网供水	1998.0	115.0(t₃)	0.78	483.03
2	进换热器的一次热网供水	1998.0	85.0(t₂)	0.78	356.58
3	出换热器的一次热网供水	1998.0	50.0(t₁)	0.78	210.00
4	一次热网回水	1998.0	25.0(t₀)	0.78	105.55
5	二次热网回水	7818.3	45.0( $t 0'$ )	0.65	188.99
6	进换热器的二次热网回水	2325.6	45.0( $t 0'$ )	0.65	188.99
7	出换热器的二次热网回水	2325.6	75.0( $t 4'$ )	0.65	314.52
8	二次热网供水	7818.3	68.0( $t 3'$ )	0.65	285.19
9	进热泵吸收器的二次热网回水	5492.7	45.0	0.65	188.99
10	进热泵冷凝器的二次热网回水	5492.7	60.0( $t 1'$ )	0.65	251.71
11	出热泵冷凝器的二次热网回水	5492.7	65.0( $t 2'$ )	0.65	272.63

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