基于钠基吸附剂的烟气脱碳系统余热利用研究

doi:10.16085/j.issn.1000-6613.2019-0874

摘要/Abstract

摘要：

针对基于钠基固体吸附剂的燃烧后脱碳技术应用于燃煤电厂后综合能耗偏高的问题，本文提出与供热机组结合的碳捕集/供热双机组系统，利用低温热网回水回收系统低品位余热。依据双机组的抽汽混合与否构建了两种系统流程，分析了两种不同方案下的系统性能。研究结果表明，在有效回收脱碳系统碳酸化反应余热后，独立抽汽方案中碳捕集综合能耗从4.05GJ/t CO₂降低至1.26GJ/t CO₂，而混合抽汽方案中碳捕集综合能耗降低至1.13GJ/t CO₂，同时双机组系统的热网供热量较单供热机组分别增加了67.5%和72.8%，经济效益显著。分析了混合抽汽方案的系统中碳捕集综合能耗随相关运行参数变化的规律，发现碳酸化反应温度和热网回水温度因为能够直接影响系统余热利用程度因而更易对碳捕集综合能耗产生影响。

关键词: 钠基吸附剂, 余热利用, 二氧化碳捕集, 模拟, 优化

Abstract:

Focused on the huge energy consumption by sodium-based CO₂ capture process of the post-combustion CO₂ capture technology, a cogeneration unit (CU) was integrated into the coal-fired power plant with the CO₂ capture process (CCPP), in which the returned water from the heat network could be used to recover the lower-grade waste heat. Two different configurations of this CCPP-CU system, namely the separated extraction configuration and the mixed extraction configuration, were proposed, and the thermal performance of these two configurations was analyzed. Results showed that the comprehensive energy consumption of the separated extraction configuration and the mixed extraction configuration could be reduced from 4.05GJ/t CO₂ to 1.26GJ/t CO₂ and 1.13GJ/t CO₂, respectively. Besides, the corresponding heat capacity of the CCPP-CU system was increased by 67.5% and 72.8%, which showed remarkable economic benefits. Effects of key parameters on the energy consumption of the mixed extraction configuration were investigated, which showed that the carbonation reaction temperature and the heat network return water temperature had great impact on the utilization ratio of the waste heat and the energy consumption of CO₂ capture system.

Key words: sodium-based sorbents, waste heat recovery, CO₂ capture, simulation, optimization

中图分类号:

TK09

谢玮祎,陈晓平,马吉亮,刘道银,梁财,吴烨,蔡天意. 基于钠基吸附剂的烟气脱碳系统余热利用研究[J]. 化工进展, 2020, 39(2): 720-727.

Weiyi XIE,Xiaoping CHEN,Jiliang MA,Daoyin LIU,Cai LIANG,Ye WU,Tianyi CAI. Waste heat recovery from sodium-based CO₂ capture process incoal-fired power plants[J]. Chemical Industry and Engineering Progress, 2020, 39(2): 720-727.

图/表 14

图1 钠基固体吸附剂脱碳原理

图2 基于钠基固体吸附技术的脱碳系统模型

表1 模拟烟气组成成分

体积分数/%
H₂O	O₂	N₂	SO₂	CO₂	NO
13.77	3.04	69.41	0.00	13.77	0.01

图3 基于钠基固体吸附技术的燃煤电厂脱碳流程1—锅炉；2—烟气处理系统；3、8、11—风机；4—碳酸化反应器；5—预热器；6、10、12—旋风分离器；7—再生反应器；9—冷却床；13—气液换热器；14—冷却塔；15—除氧器；16—高压缸；17—中压缸；18—低压缸；19、20、21—高压加热器；22—驱动给水泵的小汽机

图4 吸收式换热技术原理[13]1—吸收式热泵；2—水水换热器

图5 碳捕集供热双机组系统方案A的流程1—热力站；2—水泵；3—碳酸化反应器；4—冷却床；5—预热器；6,16—气液换热器；7—尖峰加热器；8—小汽机；9,12,14—风机；10,13,15—旋风分离器；11—再生反应器；17—冷却塔

图6 碳捕集供热双机组系统方案B的流程1—热力站；2—水泵；3—碳酸化反应器；4—冷却床；5—尖峰加热器；6—小汽机；7,10,12—风机；8,11,13—旋风分离器；9—碳酸化反应器；14—气液换热器；15—冷却塔

表2 不同方案中碳捕集综合能耗结果

项目	输入能量/MW		回收的有效热量/MW			CO₂捕集量/t·h^-1	综合能耗/GJ·(t CO₂)^-1
项目	再生床所需热量	辅助风机耗功	再生气体冷却热	再生吸附剂冷却热	吸附反应热	CO₂捕集量/t·h^-1	综合能耗/GJ·(t CO₂)^-1
碳捕集机组	250.2	52.74	42.9	—	—	231.2	4.05
方案A	250.2	52.74	42.9	62.8	116.04	231.2	1.26
方案B	437.54	52.74	42.53	255.9	119.53	231.2	1.13

表3 不同方案中系统性能分析结果

参数	碳捕集机组	供热机组	方案A	方案B
模拟结果
汽轮机抽汽比例/%	40.60	43.91	42.25	42.25
汽轮机发电量/MW	244.23	228.1	472.33	472.33
小汽机发电量/MW	—	20.57	20.57	6.33
热网供热量/MW	—	264.4	442.94	456.8
辅助风机耗功/MW	52.74	—	52.74	52.74
热网循环水泵耗功/MW	—	0.42	0.87	0.9
凝结水泵耗功/MW	0.2	0.17	0.37	0.37
其他厂用电/MW	15.3	15.3	30.6	30.6
性能评价指标
发电效率/%	33.73	34.34	34.03	33.05
发电效率损失/%	8.56	7.95	8.26	9.24
电厂净效率/%	24.30	32.15	28.19	27.21
净效率损失/%	15.87	8.03	11.98	12.97
燃料利用系数/%	33.73	70.81	64.62	64.59

图7 系统能耗随碳酸化反应温度变化的规律

图8 系统能耗随再生反应温度变化的规律

图9 系统能耗随CO2脱除率变化的规律

图10 系统能耗随热网回水温度变化的规律

图11 系统能耗随热网供水温度变化的规律

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