基于3kW塔式串行流化床差异燃料的化学链燃烧解析

doi:10.16085/j.issn.1000-6613.2022-0589

摘要/Abstract

摘要：

化学链燃烧反应器具有广泛的燃料适应性，可同时兼顾气、液、固多类型燃料的运行。本文依托耦合内构件的3kW塔式串行流化床反应器，分别开展异丙醇、污泥以及煤炭的化学链燃烧实验，探究燃料物化属性对化学链燃烧过程与反应器运行的影响，揭示面向目标燃料的反应器针对性设计、载氧体性能选择与流化操作策略，助力形成指向性强、碳捕集效率高与操作灵活的化学链燃烧技术。面对碳化程度低、有机质含量高的固体燃料，焦炭气化速率已非强化重点，如污泥在3kW塔式反应器910℃与150s停留时间内，可实现大于99%的CO₂捕集效率，化学链燃烧反应器应侧重改善可燃气体转化与旋风分离器对轻质焦炭颗粒的捕捉。当采用异丙醇等高CH₄含量的燃料时，Fe基矿石载氧体的反应性能不足，3kW反应器的额外耗氧率高达10%~19%，其中未燃尽CH₄对额外耗氧率的贡献占比超80%。化学链燃烧反应器需依据热解反应气的物化特性，选择或掺混功能性载氧体，以针对性改善气固转化。在煤等高碳化燃料的化学链燃烧过程中，焦炭气化是反应的限制性步骤，简化循环结构的3kW塔式反应器停留时间不足，仅可获得60%的CO₂捕集效率。耦合碳捕集器、增添颗粒的循环回路是实现高效煤化学链燃烧的关键。同时，亟需注重固体燃料给料的连续性与稳定性，螺旋给料器批次、间歇性的非均匀给料方式，可造成燃料反应器与料腿压力的周期性大幅振荡，破坏循环操作的稳定性与安全性。

关键词: 化学链燃烧, 二氧化碳捕集, 燃料, 流化床, 性能优化

Abstract:

Chemical looping combustion (CLC), with wide fuel adaptability, can be operated with multiple fuels, including gas, liquid, and solid fuels. The CLC processes of isopropanol, sewage sludge, and coal were investigated in a 3kW tower interconnected fluidized bed reactors, in which several internal gas distributors were arranged along the fuel reactor to establish a multi-staged chambers structure. The experiments were intended to indicate the rules of reactor optimization design, oxygen carrier selection, and operational fluidization strategy as treating with differential fuels, which was also expected to promote the CLC development with the formation of strong pertinence, high carbon capture efficiency, and flexible fluidization. For the fuel with low carbonization and high organic matter content, the CLC process intensification should emphasize the improvement of gas-solid reaction and cyclone collection efficiency. The char gasification was no longer the critical factor on account that above 99% CO₂ capture efficiency was acquired in the 3kW reactor as adopting sewage sludge as fuel. The Fe-based oxygen carrier showed a limited reactivity with loading isopropanol, which would release abundant CH₄ in the pyrolysis process. The oxygen demand for isopropanol CLC was high as 10%—19%, in the unconverted CH₄ accounted for 80%. The CLC reactors should select or blend functional oxygen carriers according to the physicochemical characteristics of pyrolysis gases. The char gasification was the limited step in the coal CLC process, resulting in only 60% CO₂ capture efficiency obtained in the 3kW reactors, which had a simplified circulation structure resulting in a limited particle residence time. Coupling carbon stripper and adding an additional circulation loop of char particles were the critical factors to realizing high-efficiency chemical chain combustion. In addition, it was urgent to pay attention to the continuity and stability of solid fuel feeding. The intermittent feeding mode of the screw feeder could cause periodic and significant fluctuation of fuel reactor and feed leg pressure and destroy the stability and safety of cyclic operation.

Key words: chemical looping combustion, CO₂ capture, fuel, fluidized bed, performance optimization

中图分类号:

TK12

沈天绪, 沈来宏. 基于3kW塔式串行流化床差异燃料的化学链燃烧解析[J]. 化工进展, 2023, 42(1): 138-147.

SHEN Tianxu, SHEN Laihong. Investigation of multi-fuel chemical looping combustion in a 3kW interconnected fluidized bed reactors[J]. Chemical Industry and Engineering Progress, 2023, 42(1): 138-147.

图/表 8

图1 化学链燃烧原理

图2 3kW塔式化学链燃烧装置结构

表1 煤炭与污泥的工业分析与元素分析

项目	工业分析（质量分数）/%				元素分析（质量分数）/%					低位热值(LHV) /MJ·kg^-1
项目	M	V	FC	A	C	H	O	N	S	低位热值(LHV) /MJ·kg^-1
煤炭	15	35.3	34.6	15.1	45.39	2.85	16.95	0.98	1.45	15.68
污泥	4.8	36.8	3.9	54.5	20.27	3.44	3.52	0.55	12.95	9.4

表2 3kW塔式化学链燃烧反应器的实验工况与运行结果

序号	燃料	温度/℃	FR流化气速/m·s^-1	停留时间/s	η_CC/%	X_C/%	Ω_T/%	$Ω C H 4$ /%
1	异丙醇	840	0.37	115	—	—	19.09	81.62
2	异丙醇	870	0.38	112	—	—	18.35	82.12
3	异丙醇	900	0.37	114	—	—	15.59	82.59
4	异丙醇	930	0.36	117	—	—	10.01	76.36
5	污泥	920	0.34	144	99.26	91.71	6.17	57.66
6	煤炭	920	0.33	151	61.53	95.66	4.87	41.11

表2 3kW塔式化学链燃烧反应器的实验工况与运行结果

序号	燃料	温度/℃	FR流化气速/m·s^-1	停留时间/s	η_CC/%	X_C/%	Ω_T/%	$Ω C H 4$ /%
1	异丙醇	840	0.37	115	—	—	19.09	81.62
2	异丙醇	870	0.38	112	—	—	18.35	82.12
3	异丙醇	900	0.37	114	—	—	15.59	82.59
4	异丙醇	930	0.36	117	—	—	10.01	76.36
5	污泥	920	0.34	144	99.26	91.71	6.17	57.66
6	煤炭	920	0.33	151	61.53	95.66	4.87	41.11

图3 3kW塔式化学链反应器的异丙醇化学链燃烧

图4 3kW塔式化学链反应器的煤炭与污泥化学链燃烧

图5 燃料反应器及其料腿的压降曲线

表3 污泥、煤炭和异丙醇化学链燃烧3kW塔式反应器的温度分布

项目	空气反应器/℃			燃料反应器/℃
项目	T1	T2	T5	T12	T11	T10	T9	T8	T6
污泥	996	994	753	911	914	935	935	934	709
煤炭	1001	998	749	909	912	930	929	931	707
异丙醇	995	991	749	914	929	933	935	933	712

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