冷凝换热与协同脱硫性能实验分析

doi:10.16085/j.issn.1000-6613.2022-1769

摘要/Abstract

摘要：

锅炉排烟中含有大量水蒸气，直接排放不仅会造成资源和能源的浪费，还会形成白烟，造成视觉污染和局部雾霾，采用凝结换热技术可有效回收排烟余热，并协同脱除部分污染物。本文设计并搭建了天然气燃烧热态实验台，对烟气横向冲刷水平光管的凝结传热特性展开实验研究，分析对比了过量空气系数、给水温度对凝结换热强弱的影响，拟合出2205不锈钢/PTFE两种换热器的水蒸气冷凝率量纲为1准则关联式。此外，基于搭建的SO₃/H₂SO₄雾化蒸发冷凝实验系统，进一步研究分析了不同工况下烟气中SO₃/H₂SO₄的冷凝脱除规律。实验结果表明，2205冷凝换热器冷凝率为19.53%~85.57%，最大凝结换热系数为250.68W/(m²·K)；氟塑料冷凝换热器冷凝率为4.92%~42.04%，最大凝结换热系数为131.09W/(m²·K)。同时，SO₃/H₂SO₄气体冷凝脱除率随着给水温度的升高而增大，随着SO₃/H₂SO₄气体浓度的增大而减小，但一定时间内的H₂SO₄绝对冷凝量在增加，SO₃/H₂SO₄最大冷凝脱除率达到18%以上。

关键词: 烟道气, 换热器, 传热, 凝结, 脱硫

Abstract:

Exhaust from oil-fired and gas-fired boilers contains a large amount of water vapor, and direct emissions will not only result in the waste of resources and energy, but also the formation of white smoke, causing visual pollution and partial haze. Condensation heat transfer technology can effectively recover the waste heat of the exhaust gas and synergistically remove some pollutants. A hot-state experiment for natural gas combustion was designed. It was built to research on the characteristics of condensation heat transfer and decontamination for two heat exchangers with horizontal tubes. The influence of the excess air coefficient and the feed water temperature on the condensation heat transfer was analyzed, and two non-dimensional correlation formulae for the water vapor condensation ratio of 2205 stainless steel/PTFE heat exchangers were fitted. In addition, based on the established SO₃/H₂SO₄ atomization evaporation experimental system, the condensation removal rule of SO₃/H₂SO₄ under different working conditions was further analyzed. The results showed that the condensation rate of 2205 heat exchanger was 19.53%—85.57%, and the maximum condensation heat transfer coefficient was 250.68W/(m²·K). The condensation rate of fluorine plastic heat exchanger was 4.92%—42.04%, and the maximum condensation heat transfer coefficient was 131.09W/(m²·K). At the same time, the condensation removal rate of SO₃/H₂SO₄ increased with the increase of the water supply temperature, and decreased with the increase of the concentration of SO₃/H₂SO₄. However, the absolute condensation amount of H₂SO₄ increased within a certain period of time, and the maximum condensation removal rate of SO₃/H₂SO₄ reached more than 18%.

Key words: flue gas, heat exchangers, heat transfer, condensation, desulfurization

中图分类号:

TK124

王云刚, 焦健, 邓世丰, 赵钦新, 邵怀爽. 冷凝换热与协同脱硫性能实验分析[J]. 化工进展, 2023, 42(8): 4230-4237.

WANG Yungang, JIAO Jian, DENG Shifeng, ZHAO Qinxin, SHAO Huaishuang. Experimental analysis of condensation heat transfer and synergistic desulfurization[J]. Chemical Industry and Engineering Progress, 2023, 42(8): 4230-4237.

图/表 13

图1 实验系统示意图1—湿式体积流量计；2—燃烧器；3—盘管炉膛；4—一级冷却器；5—二级冷凝换热器（实验段）；6—烟气再热器；7—轴流风机；8—水箱；9—水泵；10—转子流量计；11—铠装热电偶；12—冷却塔；13—热电偶；14—数据采集装置；15—计算机；16—冷凝液收集管

图2 二级冷凝换热器本体结构

表1 实验用天然气组分

项目	数值	项目	数值
CH₄体积分数/%	93.18	N₂体积分数/%	2.24
C₂H₆体积分数/%	1.5	CO₂体积分数/%	2.16
C₃H₈体积分数/%	0.22	O₂体积分数/%	0.63
其他烃类体积分数	0.06	总硫/mg·m^-3	≤1
高位热值/MJ·m^-3	35.84	低位热值/MJ·m^-3	32.3

表2 烟气物性计算方法

动力黏度系数	运动黏度系数	热导率	定压比热容
$η = 100 ∑ g i / η i$	$ν = 100 ∑ r i ν i$	$λ = ∑ r i k i (M i) 13 ∑ r i (M i) 13$	$c p = ∑ r i c i 100$

表2 烟气物性计算方法

动力黏度系数	运动黏度系数	热导率	定压比热容
$η = 100 ∑ g i / η i$	$ν = 100 ∑ r i ν i$	$λ = ∑ r i k i (M i) 13 ∑ r i (M i) 13$	$c p = ∑ r i c i 100$

图3 过量空气系数和水蒸气露点温度的关系曲线

图4 过量空气系数与两种换热器换热系数的关系曲线

图5 过量空气系数与水蒸气冷凝率的关系曲线

图6 给水温度与两种换热器换热系数的关系曲线

图7 给水温度与两种换热器水蒸气冷凝率的关系曲线

图8 冷凝率实验值与拟合公式结果比较

图9 不同SO3/H2SO4浓度下冷凝脱除率随给水温度的变化

图10 SO3/H2SO4冷凝率随SO3/H2SO4浓度的变化曲线

图11 SO3/H2SO4冷凝量随SO3/H2SO4浓度的变化曲线

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