摘要
化学链燃烧(CLC)由于其固有的CO2浓度高、易分离、CO2减排成本低等优点已成为一种具有发展前景的固体燃料燃烧技术。目前CLC技术由原位气化化学链燃烧(iG-CLC)和氧解耦化学链燃烧(CLOU)2种技术为代表。采用固体作为燃料燃烧时,其污染元素会以气体形式释放到大气或掺杂到CO 2目标气体中,带来环境及操作问题。论述了固体燃料化学链燃烧的iG-CLC及CLOU2种技术及相关原理,简述了国内外研究现状,并对2种技术的性能和优缺点进行分析。同时,着重对固体燃料化学链燃烧过程中存在的污染元素及其释放规律进行总结。对于固体燃料中的S元素,最终将会大部分转移到气相中并以H2S和SO2(iG-CLC)或单一SO2(CLOU)的形式释放,小部分会固存于灰烬中或与氧载体结合。在排放比例方面,随着燃料反应器温度的增加,燃料反应器出口处含硫气体含量上升,同时空气反应器出口处含硫气体含量下降。固体燃料中的N元素将全部转移到气相中并在2种技术中均以N2和NO形式释放,不同之处在于CLOU技术由于氧载体的释氧性使得NO生成偏多,燃料反应器和空气反应器出口处的含氮气体含量与温度的关系与S元素变化一致。固体燃料中Hg元素主要以Hg^0 和Hg^2+分布在气相中,在燃料反应器中主要以Hg^0形态存在,而在空气反应器中主要是Hg^2+,在CLOU技术中有相当一部分Hg(42.5%)保留在燃烧的灰中。燃料反应器中Hg释放量将随燃料反应器温度的升高而增加,空气反应器的Hg释放量随温度升高而降低。固体燃料化学链燃烧过程中的挥发分作为一种污染物在排放方面也需关注。结果表明燃料类型似乎对燃料反应器出口气体中的焦油量具有决定性影响,目前只发现高挥发分生物质的iG-CLC过程有焦油排放问题,而在CLOU技术中由于燃料反应器中气态氧的存在导致焦油化合物完全燃烧。最后结合污染元素性质及在2种化学链燃烧技术中的释放规律,针对减少相关污染物的排放提出了原料处理及工艺改进建议。
Chemical-looping combustion(CLC)has become a promising solid fuel combustion technology due to its inherent advantages of high concentration of CO2,easy separation and low cost of CO2 reduction.At present,CLC technology includes in-situ gasification CLC(iG-CLC)and oxygen uncoupling(CLOU)of solid fuel chemical-looping combustion.When solid fuel is used for combustion,the pollution elements will be released into the atmosphere or doped into the target gas of CO2 in the form of gas,which will bring environmental and operational problems.In this paper,two technologies and related principles of iG-CLC and CLOU for chemical looping combustion of solid fuel were introduced,the research status at home and abroad was briefly described,and the properties,advantages and disadvantages of the two technologies were analyzed.At the same time,the pollution elements and their release rules in the process of solid fuel chemical chain combustion were summarized and analyzed.Most of the S elements in the solid fuel will eventually be transferred to the gas phase and released in the form of H2S and SO2(iG-CLC)or single SO2(CLOU),a small portion of which will be fixed in the ashes or combined with the oxygen carrier.In terms of emission ratio,with the increase of fuel reactor temperature,the content of sulfur gas at the outlet of fuel reactor increases,while the content of sulfur gas at the source of air reactor decreases.For the solid fuel,all the N elements will be transferred to the gas phase and released in the form of N2 and NO in both technologies.The difference is that in CLOU technology,the formation of NO is more due to the oxygen release of oxygen carrier.At the same time,the change of nitrogen content and temperature at the outlet of fuel reactor and air reactor is consistent with that of S.The Hg elements in the solid fuel will be mainly presented in the gas in the form of Hg^0 and Hg^2+,and mainly in the form of Hg^0 in the fuel reactor,and in the form of Hg 2+in the air reactor,and a considerable part of the Hg(42.5%)in the CLOU technology will be retained in the combustion ash.The release of Hg in the fuel reactor will increase with the increase of the temperature of the fuel reactor,and the release of Hg in the air reactor will decrease.The volatile matter in the chemical chain combustion process of solid fuel,as a pollutant,also needs to be paid attention to in the aspect of emission.The results show that the type of fuel seems to have a decisive effect on the amount of tar in the outlet gas of the fuel reactor.At present,tar emission is only found in the iG-CLC of biomass with high volatile content,while in CLOU technology,the tar compounds are completely burned due to the presence of gaseous oxygen in the fuel reactor.Finally,combined with the properties of pollution elements and the release law in the two chemical chain combustion technologies,some suggestions are put forward for the process development and design by the raw material treatment and process improvement to reduce the emission of pollutants.
作者
胡东海
黄戒介
李春玉
余钟亮
康思乐
张建利
王志青
杜梅杰
房倚天
HU Donghai;HUANG Jiejie;Li Chunyu;YU Zhongliang;KANG Sile;ZHANG Jianli;WANG Zhiqing;DU Meijie;FangYitian(State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences,Taiyuan 030001,China;Graduate University of Chinese Academy of Sciences,Beijing 100049,China;Tongmei Guangfa Chemical Industry Co.,Ltd.,Datong 037005,China;State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University,Yinchuan 750021,China)
出处
《洁净煤技术》
CAS
2020年第4期1-10,共10页
Clean Coal Technology
基金
中国科学院洁净能源创新研究院合作基金资助项目(DNL180205)
省部共建煤炭高效利用与绿色化工国家重点实验室开放课题资助项目(2019-KF-04)。
关键词
化学链燃烧
固体燃料
CO2分离
污染物释放
环境保护
chemical-looping combustion
solid fuel
CO2 separation
pollutant release
environmental protection
