Design and evaluation of a coal-based polygeneration system with carbon cycle

doi:10.11949/0438-1157.20211568

Abstract

Abstract:

By applying the high-density triple bed circulating fluidized bed (TBCFB) to a series-parallel integrated polygeneration system, a coal-based polygeneration system based on carbon cycle process and parameters co-optimization is proposed, which can promote the high-quality and high-efficiency conversion of low-rank coal resources. The carbon cycle is embodied in two aspects. First, this system uses a pyrolysis gas cycle as the pyrolysis atmosphere, which can increase the tar yield and realize the high-quality conversion of low-rank coal.The second is the use of oxygen-enriched combustion in TBCFB, which can increase the concentration of carbon dioxide in the flue gas. While, using the flue gas instead of nitrogen directly as a working fluid for gas turbine power generation also reduces nitrogen consumption. The Aspen Plus is used here to investigate the influence of unreacted syngas circulation ratio and flue gas injection rate on the process via performing material, energy and exergy balance calculations for polygeneration systems. In addition, with energy efficiency as the optimization goal, suitable operating conditions are further found for the coal-based polygeneration system with carbon cycle. The results show that when the flue gas is used for gas injection in the power unit, the energy utilization efficiency of the coal-based polygeneration system with carbon cycle reaches 49.7%, which is higher than that of the traditional system using nitrogen as the pyrolysis atmosphere. Compared with the traditional unit production system, the coal-based polygeneration system can save 13% of energy, which is equivalent to reducing carbon dioxide emissions by 14.9×10⁴ tons per year for a system with an annual capacity of 30×10⁴ tons of coal.

Key words: carbon cycle, coal-based polygeneration system, energy analysis, computer simulation, integration, optimization design

摘要：

将高密度三塔式循环流化床(TBCFB)应用于串并联综合型多联产系统，提出一种基于碳循环的流程与参数共优化的煤基多联产系统，促进低阶煤资源的高质高效转化。碳循环体现在两方面，一是系统以热解煤气循环作为热解气氛，提高了焦油产率，实现低阶煤高质化转化；二是在TBCFB使用富氧燃烧，提高了烟气中二氧化碳浓度，将烟气替代氮气直接用于燃气轮机发电工质，减少了氮气消耗。利用Aspen Plus对全系统进行模拟，对多联产系统进行物料、能量和?衡算，研究未反应合成气循环比和烟气注入量对过程的影响；以能量利用效率为优化目标，对煤基多联产碳循环系统的操作条件寻优。结果表明，动力单元注入气体使用烟气时，煤基多联产碳循环系统的能量利用效率达49.7%，高于用氮气作为热解气氛的传统煤基多联产系统，相比传统的单产系统，煤基多联产系统的能量可节约13%，对于年处理30万吨煤的系统，折合减少二氧化碳排放量为14.9万吨/年。

关键词: 碳循环, 煤基多联产, 能量分析, 计算机模拟, 集成, 优化设计

CLC Number:

TQ 015.2

Qiwang HOU, Zhaolun WEN, Zhonglin ZHANG, Yegang LIU, Jingxuan YANG, Dongliang CHEN, Xiaogang HAO, Guoqing GUAN. Design and evaluation of a coal-based polygeneration system with carbon cycle[J]. CIESC Journal, 2022, 73(5): 2073-2082.

侯起旺, 文兆伦, 张忠林, 刘叶刚, 杨景轩, 陈东良, 郝晓刚, 官国清. 一种煤基多联产碳循环系统的设计及评价[J]. 化工学报, 2022, 73(5): 2073-2082.

Figures/Tables 12

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Proximate analysis/ %(mass，d)			Ultimate analysis/ %(mass，daf)					LHV/(MJ/kg)
FC	A	V	C	H	N	S	O^①
47.21	5.8	46.99	74.35	5.13	0.72	0.31	19.49	23.45

Proximate analysis/ %(mass，d)			Ultimate analysis/ %(mass，daf)					LHV/(MJ/kg)
FC	A	V	C	H	N	S	O^①
47.21	5.8	46.99	74.35	5.13	0.72	0.31	19.49	23.45

参数	值
压气机绝热压缩效率/%	91
透平绝热膨胀效率/%	86
氧气温度/℃	15
氧气压缩比/%	29.6
汽轮机高压缸效率/%	87
汽轮机中压缸效率/%	90
汽轮机低压缸效率/%	88
机械电机效率/%	98

参数	值
压气机绝热压缩效率/%	91
透平绝热膨胀效率/%	86
氧气温度/℃	15
氧气压缩比/%	29.6
汽轮机高压缸效率/%	87
汽轮机中压缸效率/%	90
汽轮机低压缸效率/%	88
机械电机效率/%	98

物流	摩尔分数/%							摩尔流量/ (kmol/h)	质量流量/(t/h)	温度/℃	压力/MPa
物流	H₂+CH₄	CO	CO₂	N₂	O₂	H₂O	CH₃OH	摩尔流量/ (kmol/h)	质量流量/(t/h)	温度/℃	压力/MPa
1	—	—	—	—	—	—	—	—	37.5	200	0.1
2	59.1	27.7	5.4	—	—	7.7	—	1398.1	18.3	40	6.5
3	67.9	30.0	2.1	—	—	—	—	1204.6	13.2	35.9	5.57
4	—	—	—	—	—	10.8	86.6	462.0	14.3	65.3	3.5
5	—	—	93.6	1.2	5.1	—	—	885.8	38.3	843.8	0.1
6	3.6	3.4	6.8	—	—	85.3	—	599.9	12.0	593.7	5.0
7	—	—	54.6	0.6	3.0	41.8	—	1347.2	44.1	227.8	0.1