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Combustion and Self-Desulfurization Characterization of Blended Low-Rank coals for Improved Resource Utilization in Fluidized Bed Boilers

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Journal of Thermal Science 2024年第3期33卷 1242-1256页

作者： SU Lipeng ZHANG Cong ZHANG Yongsheng WANG Tao WANG Jiawei Key Laboratory of Power Station Energy Transfer Conversion and System Ministry of EducationNorth China Electric Power UniversityBeijing102206China

The co-combustion of low-rank coals through fluidized bed boiler(CFB)is an effective approach to enhance the level of resource utilization.To date,there has been a lack of investigation concerning the co-combustion kinetics and self-desulfurization characteristics of coal slime,coal gangue,and raw coal.In this study,we adopted multiple model-free and model-fitting methods to comparatively analyze co-combustion kinetics of blended coals on the basis of thermogravimetric data.Then,the sulfur balance and self-desulfurization of blended coals in the co-combustion were intensively investigated using a tube furnace set-up.The results reveal that in the presence of coal gangue in blended coals,the average activation energy(E_(a))falls within the range of 65.7 kJ/mol to 100.4 kJ/mol,as determined by four model-free methods.Conversely,in the absence of coal gangue,only the Flynn-Wall-Ozawa(FWO)and Friedman(FM)methods are deemed appropriate for calculating the average E_(a),yielding a value of 77.3 kJ/mol.The first order reaction model is confirmed to be reliable for analyzing the co-combustion kinetics of low-rank blended coals.Irrespective of the specific composition of the blended coal,a significant linear correlation exists between the Ea and the natural logarithm of the pre-exponential factor(lnA)within an extensive range of parameters.Moreover,the addition of coal gangue to the blended coal substantially enhances the self-desulfurization level,resulting in an increase from 25.7%to60.7%at 1073 K.The self-desulfurization efficiency exhibits a good linear relationship with both the mass ratio of coal gangue to coal slime and the molar ratio of calcium to sulfur.In a practical implementation,the optimal addition ratio of coal gangue is a trade-off between the self-desulfurization efficiency and the ignition capacity.

关键词： coal slime coal gangue fluidized bed boilers self-desulfurization resource utilization

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Experiment Study on the High-Temperature Thermal Treatment and Ultra-Low NOx Control of Solid Waste coal slime in Circulating Fluidized Bed

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Journal of Thermal Science 2022年第6期31卷 2244-2251页

作者： SONG Guoliang XIAO Yuan YANG Zhao YANG Xueting LYU Qinggang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Dalian National Laboratory for Clean Energy Dalian 116023China

coal slime is a kind of solid waste and inferior fuel, which is urgently needed to utilize. In this paper, a high-temperature thermal treatment of coal slime in a circulating fluidized bed(CFB) was attempted to achieve resource utilization. In the experiment, the combustion characteristics of dried coal slime during high-temperature thermal treatment were investigated in a 0.5 MW pilot-scale CFB. The stable fluidized combustion of dried coal slime was realized. When the excess air ratio was closer to 1.0, the furnace temperatures would be uniform. The ignition method of dried coal slime was changed correspondingly while the feeding position changed. However, feeding coal slime to the loop seal was instrumental in decreasing NO_(x) emissions. Moreover, the NO_(x) emissions were tried to further control by the post-combustion technology. Post-combustion technology could significantly reduce NO_(x) emissions below 50 mg·Nm^(-3) while ensuring combustion efficiency. Besides, it was found that there was an optimum excess air ratio in CFB of about 0.9 resulting in minimum NO_(x) emissions of coal slime. The experiment results could well guide the industrial-scale high temperature thermal treatment of coal slime.

关键词： solid waste coal slime thermal treatment CFB NOx post-combustion

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Influence of Limestone Addition on Combustion and Emission Characteristics of coal slime in the 75 t/h CFB Boiler with Post-Combustion Chamber

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Journal of Thermal Science 2023年第5期32卷 1849-1857页

作者： WANG Chao SONG Guoliang YANG Zhao XIAO Yuan YANG Xueting JI Zengcai LYU Qinggang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China School of Engineering Science University of Science&Technology of ChinaHefei 230026China University of Chinese Academy of Sciences Beijing 100049China Dalian National Laboratory for Clean Energy Dalian 116023China

coal slime can be disposed in quantity and fully utilized in a well-designed circulating fluidized bed(CFB)boiler,but the nitrogen oxides(NO_(x))and sulphur dioxide(SO_(2))emissions generated in the combustion of coal slime have contributed to serious atmospheric pollution.High Temperature&Post-combustion Technology,a novel and high-efficient way to reduce the NO_(x)emission in the process of combustion,is applied to a 75 t/h CFB boiler burning exclusively coal slime,which will succeed to meet the ultra-low NO_(x)emission standard.To further explore an appropriate method to reduce the SO_(2)emission under the condition of new technology,the experiments were conducted on a 75 t/h CFB boiler with post-combustion chamber to study the influence of limestone addition on the combustion and emission characteristics of coal slime.The experimental results showed that High Temperature&Post-combustion Technology combined with the sorbent injection in the furnace is a very promising technology to control the NO_(x)and SO_(2)emissions simultaneously.Limestone addition can cause the slight decrease in combustion temperature.Limestone addition will lead to the increase in NO_(x)emission in the combustion of coal slime.In 75 t/h coal slime CFB boiler,the desulfurization efficiency of limestone injection in furnace is close to 98%,achieving the ultra-low SO_(2)emission.To meet the standard of ultra-low NO_(x)and SO_(2)emission,the two technologies for simultaneous removal of NO_(x)and SO_(2)emissions are economical and feasible currently:Removal of SO_(2)under ultra-low NO_(x)emission and Removal of NO_(x)under ultra-low SO_(2)emission.

关键词： coal slime CFB boiler NO_(x) SO_(2) limestone simultaneous removal

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Combustion and NO_(x)Emission Characteristics of coal slime Solid Waste at Different Feeding Positions

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Journal of Thermal Science 2023年第6期32卷 2351-2360页

作者： YANG Xueting SONG Guoliang YANG Zhao WANG Chao JI Zengcai ZHANG Xingshun Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China Dalian National Laboratory for Clean Energy Dalian116023China School of Engineering Science University of Science&Technology of ChinaHefei230026China Shandong Huaju Energy Co.Ltd Jining273500China

The NO_(x)emission of coal slime burned in circulating fluidized bed(CFB)boilers could hardly meet the increasingly strict standards in China.Feeding coal slime from the top of furnace led to uneven combustion in furnace and cyclones,short residence time and overheated tail heating surface.The effects of feeding positions on the combustion uniformity and pollutant emission characteristics of coal slime were studied.The experimental results showed that the coal slime combustion was more uniform when feeding from the front wall and longer residence time was conducive to the control of NO_(x)emission.When the boiler temperature and excess air ratio were almost identical,the initial NO_(x)emissions were 45.0 mg·m^(−3)and 70.7 mg·m^(−3)when feeding from the front wall and the top of furnace,respectively;the NO_(x)emission was cut down 36.35%when feeding from the front wall,successfully meeting the ultra-low NO_(x)emission standard of China.The adoption of feeding from the front wall greatly reduced the original emission of NO_(x);the operation costs in the practical applications were saved to a large extent.

关键词： solid waste coal slime CFB boiler ultra-low NO_(x)emission feeding positions combustion uniformity

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Combustion Characteristics and NO Emissions during Co-Combustion of coal Gangue and coal slime in O_(2)/CO_(2) Atmospheres

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Journal of Thermal Science 2023年第1期32卷 457-467页

作者： PENG Hao WANG Baofeng LI Wenxiu YANG Fengling CHENG Fangqin Institute of Resources and Environmental Engineering Engineering Research Center of CO_(2) Emission Reduction and Resource Utilization-Ministry of Education of the People's Republic of ChinaShanxi UniversityTaiyuan 030006China

coal slime has low ash content,and adding coal slime during coal gangue combustion may have influence on combustion character;and at this process,NO will emit,and lead to environmental pollution.O_(2)/CO_(2)atmosphere is conducive to NO emission reduction.Thus combustion characteristics and NO emissions during co-combustion of coal gangue and coal slime in O_(2)/CO_(2)atmospheres were studied.The results showed the addition of coal slime increased the combustion activity of the mixed fuels in both air and O_(2)/CO_(2)atmospheres.During co-combustion,there are synergistic effects between them at the fixed carbon combustion stage,and higher blending ratio of coal slime leads to stronger synergistic effect.Furthermore,this study also showed that with the increasing of coal slime blending ratio,the emission concentration of NO increases gradually;with the increase of temperature and O_(2)concentration,the NO emission concentration also gradually increases,and higher O_(2)concentration leads to shorter time required for the complete release of NO.Besides that,the results also demonstrate that the proportion of pyrrole and nitrogen oxide in the ashes increases with the increase of combustion temperature,and pyridine and quaternary nitrogen gradually disappear,while the total nitrogen content in ash decreases with the increase of temperature.The results will contribute to a better understanding of the co-combustion process of coal gangue and coal slime in O_(2)/CO_(2)atmosphere,and provide basic data for the practical industrial application of coal gangue and slime.

关键词： coal gangue coal slime O_(2)/CO_(2)atmosphere co-combustion NO emissions

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Experimental study on conversion path of sulfur in coal slime preheating combustion

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Waste Disposal and Sustainable Energy 2022年第1期4卷 63-68页

作者： Jiahang Zhang Jianguo Zhu Qinggang Lv Yi Zhang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

In this study,coal slime was mainly utilized to conduct experiments on a 30 kW preheating combustion test rig to analyze the conversion pathway of sulfur during the experiment,aiming at reducing slime pollution,controlling sulfur emission reasonably,and providing theoretical support for the preheating combustion technology.The results showed that after the coal slime was preheated,a large number of elements were released.The maximum release rates for H and S were 94.0%and 73.3%,respectively.The released S was converted into the sulfur-containing gases like H_(2)S,COS,CS_(2),and the rest existed in the solid in the five forms of mercaptan,thiophene,sulfoxide,sulfone,and sulfate.Besides,during the combustion process,the gas was oxidized continuously and finally converted into SO2,leaving only the sulfate in the fly ash.In the preheating combustion process,26.7%of the S was released from the coal,73.3%of the S was retained in the semi-coke,and the final SO2 emission concentration of combustion was 959 ppm.

关键词： Preheating combustion Sulfur Conversation path coal slime Experimental study

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Effect of Moisture on Combustion Characteristics of High⁃Moisture⁃Content coal slime

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Journal of Harbin Institute of Technology(New Series) 2022年第1期29卷 77-87页

作者： Yongtang Wang Hui Wang Songlin Liu Hairui Yang Jiangquan Wu Academia Sinica Harbin Electric CorporationHarbin 150028China School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China Department of Energy and Power Engineering Tsinghua UniversityBeijing 100084China

The effects of moisture content on the combustion characteristics and pore structure change of coal slime are studied in this paper.The effect of moisture content on the bed temperature change,combustion efficiency,and NO_(x)and SO_(2)emission were obtained in a bench⁃scale fluidized bed reactor,revealing that the lowest bed temperature decreases with the increase in moisture content,but the effect on the highest bed temperature is not the same.Moreover,with the increase in moisture content,the observed degree of blackening of the flue gas increased,and more CO was produced,which in turn leads to a lower combustion efficiency of the coal slime.However,the presence of moisture plays a positive role in the reduction of NO_(x)and SO_(2).With the increase in moisture content,the amount of NO_(x)and SO_(2)produced tends to decrease.The effect of water on the combustion process of slime is mostly the impact of the severe vaporization process in the early stage to form a large water vapor channel,which is beneficial to the evaporation and loss of water,conducive to the reaction of water and coal combustion products,such as the formation of CO,reduction of NO_(x),SO_(2),etc.The large holes formed by the impact of water vapor decreased with the decrease of moisture content,and the nanoscale pores are mostly caused by the combustion process of volatilization and coke formation after the end of vaporization,and increase with the decrease of moisture content.

关键词： moisture combustion characteristics pore structure coal slime

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