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CPFD modeling of hydrodynamics,combustion and NOx emissions in an industrial cfb boiler

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Particuology 2023年第10期81卷 174-188页

作者： Jian Chang Xinrui Ma Xin Wang Xiaohang Li School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China Bluestar(Beijing)Chemical Machinery Co. LtdBeijing100176China

The ultra-low NOx emission requirement(50 mg/m^(3))brings great challenge to cfb boilers in China.To further tap the NOx abatement potential,full understanding the fundamentals behind cfb boilers is needed.To achieve this,a comprehensive CPFD model is established and verified;gas-solid flow,combustion,and NOx emission behavior in an industrial cfb boiler are elaborated;influences of primary air volume and coal particle size on furnace performance are evaluated.Simulation results indicate that there exists a typical core-annular flow structure in the boiler furnace.Furnace temperature is highest in the bottom dense-phase zone(about 950℃)and decreases gradually along the furnace height.Oxygen-deficient combustion results in high CO concentration and strong reducing atmosphere in the lower furnace.NOx concentration gradually increases in the bottom furnace,reaches maximum at the elevation of secondary air inlet,and then decreases slightly in the upper furnace.Appropriate decreasing the primary air volume and coal particle size would increase the CO concentration and intensify the in-furnace reducing atmosphere,which favors for NOx reduction and low NOx emission from cfb boilers.

关键词： Hydrodynamics Combustion NOx emission cfb boiler CPFD

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

Thermal Inertia of 330 MW Circulating Fluidized Bed boiler during Load Change

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热科学学报:英文版 2023年第5期32卷 1771-1783页

作者： SUN Guorui WU Haowen LIU Shangzhong LIU Tonghua LIU Jixiang YANG Hairui ZHANG Man Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Wuhan Yongping Science and Technology Co.Ltd. Wuhan 430000China

The operating principles of Circulating Fluidized Bed(cfb)boilers involve a significant amount of heat accumulation,which forms the thermal inertia of the boiler and hinders the improvement of its variable load response rate.This study aims to characterize the thermal inertia of cfb boilers by evaluating the change in the boiler's heat accumulation corresponding to the change in unit power generation.The thermal inertia of a 330MW cfb boiler was determined through the collection of operating data under four different operating conditions of 30%,50%,75%,and 100%load.The study proposes to substitute the existing refractory material with a metal grille to reduce the thermal inertia of the boiler.The effect of the metal grille on heat transfer was confirmed through verification on a 440 t/h cfb boiler,and its performance change and thermal inertia reduction were further predicted.The results indicate that over 50%of the total thermal inertia of cfb boilers originates from the refractory material.The use of metal grille in place of refractory material improved heat transfer in the furnace,resulting in a decrease of the furnace chamber temperature by 13℃in the 330 MW cfb boiler.This reduction of thermal inertia by 30%-35%will facilitate faster load lifting and lowering of the boiler,fulfilling the requirement for flexible peaking.

关键词： cfb boiler refractory thermal inertia heat accumulation

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

Development and technical progress in large-scale circulating fluidized bed boiler in China

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Frontiers in Energy 2020年第4期14卷 699-714页

作者： Zhong HUANG Lei DENG Defu CHE State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an 710049China

Circulating fluidized bed(cfb)boilers has realized the clean and efficient utilization of inferior coal like gangue and coal slime,high sulfur coal,anthracite,petroleum coke,oil shale and other resources.As a country with the largest amount of cfb boilers and the largest installed capacity in the world,China has 440100-600 MWe cfb boilers with a total capacity of 82.29 GWe,including 227 units of 135 MWe,95 units of300 MWe,and 24 supercritical units.The statistics of typical 100-300 MWe cfb boilers showed that the average number of unplanned shut-down was only 0.37 times per year,among which the 135 MWe was 0.26 times per year and 300 MWe was 0.46 times per ycai*.The auxiliary power ratio of some 300 MWe cfb boilers based on flow-pattern reconstruction can be reduced to about 4%,which is closed to the same level of pulverized coal(PC)boilers.This paper summarizes the development process and application status of China's large-scale cfb boilers,analyzes the characteristics and technical performance of the iconic units,and introduces solutions to the problems such as water wall wear and bottom ash cooling.

关键词： cfb boiler installed capacity reliability economics ultra-low emission China

COAL COMBUSTION EFFICIENCY IN cfb boiler

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China Particuology 2005年第1期3卷 142-142页

作者： HairuiYang GuangxiYue DepartmentofThermalEngineering TsinghuaUniversityBering100084P.R.China

The carbon content in the fly ash from most Chinese circulating fluidized bed (cfb) boilers is much higher than expected, thus directly influencing the combustion efficiency. In the present paper, carbon burnout was investigated both in field tests and laboratory experiments. The effect of coal property, operation condition, gas-solid mixing, char deactivation, residence time and cyclone performance are analyzed seriatim based on large amount of experimental results. A coal index is proposed to describe the coal rank, defined by the ratio of the volatile content to the coal heat value, is a useful parameter to analyze the char burnout. The carbon content in the fly ash depends on the coal rank strongly. cfb boilers burning anthracite, which has low coal index, usually have high carbon content in the fly ash. On the contrary, the cfb boilers burning brown coal, which has high coal index, normally have low carbon content. Poor gas-solid mixing in the furnace is another important reason of the higher carbon content in the fly ash. Increasing the velocity and rigidity of the secondary air could extend the penetration depth and induce more oxygen into the furnace center. Better gas solid mixing will decrease the lean oxygen core area and increase char combustion efficiency. The fine char particles could be divided into two groups according to their reactivity. One group is 'fresh' char particles with high reactivity and certain amount of volatile content. The other group of char particles has experienced sufficient combustion time both in the furnace and in the cyclone, with nearly no volatile. These 'old' chars in the fly ash will be deactivated during combustion of large coal particles and have very low carbon reactivity. The generated fine inert char particles by attrition of large coal particles could not easily burn out even with the fly ash recirculation. The fraction of large coal particles in coal feed should be reduced during fuel preparation process. The cyclone efficiency controls the particle residence tim

关键词： cfb boiler combustion efficiency char fly ash

COAL COMBUSTION EFFICIENCY IN cfb boiler

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Particuology 2005年第Z1期 142-142页

作者： Hairui Yang* and Guangxi Yue Department of Thermal Engineering, Tsinghua University, Beijing 100084, P. R. China

The carbon content in the fly ash from most Chinese circulating fluidized bed (cfb) boilers is much higher than expected, thus directly influencing the combustion efficiency. In the present paper, carbon burnout was investigated both in field tests and laboratory experiments. The effect of coal property, operation condition, gas-solid mixing, char deactivation, residence time and cyclone performance are analyzed seriatim based on large amount of experimental results. A coal index is proposed to describe the coal rank, defined by the ratio of the volatile content to the coal heat value, is a useful parameter to analyze the char burnout. The carbon content in the fly ash depends on the coal rank strongly. cfb boilers burning anthracite, which has low coal index, usually have high carbon content in the fly ash. On the contrary, the cfb boilers burning brown coal, which has high coal index, normally have low carbon content. Poor gas-solid mixing in the furnace is another important reason of the higher carbon content in the fly ash. Increasing the velocity and rigidity of the secondary air could extend the penetration depth and induce more oxygen into the furnace center. Better gas solid mixing will decrease the lean oxygen core area and increase char combustion efficiency. The fine char particles could be divided into two groups according to their reactivity. One group is "fresh" char particles with high reactivity and certain amount of volatile content. The other group of char particles has experienced sufficient combustion time both in the furnace and in the cyclone, with nearly no volatile. These "old" chars in the fly ash will be deactivated during combustion of large coal particles and have very low carbon reactivity. The generated fine inert char particles by attrition of large coal particles could not easily burn out even with the fly ash recirculation. The fraction of large coal particles in coal feed should be reduced during fuel preparation process. The cyclone efficiency controls the particle residence tim

关键词： cfb boiler combustion efficiency char fly ash

Prediction of NOx Generation concentration of cfb boiler based on PCA-GA-BP algorithm

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Prediction of NOx Generation concentration of CFB Boiler bas...

Comprehensive Solution to Flue Gas Desulfurization and Denitration of Circulating Fluidized Bed boiler

第32届中国过程控制会议(CPCC2021)

作者： Qi Wang Bin Niu Qian Sun Zhen Li Peihua Zhang Xinfeng Wang School of Automation and Software Engineering Shanxi University School of Mathematical Sciences.Shanxi University Shanxi Hepo Power Generation Co. Ltd.

In this paper,300 sets of original data of 9 variables in DCS of 2 x350 MW circulating fluidized bed boiler unit2 in a power plant in Shanxi Province were selected to predict the concentration of NOx.Due to a large number of input variables,the accuracy of GA-BP prediction model was low,so 9 variables in the original data were transformed into 4 principal components by principal component analysis,and then the model was predicted by GA-BP.The simulation results show that the PCA-GABP algorithm is consistent with the changing trend of the actual value of NOx concentration,with higher accuracy,smaller errors,and closer to the actual NOx concentration,and the prediction model is better than the GA-BP neural network prediction model.

关键词： cfb boiler PCA-GA-BP principal component analysis NOx concentration

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Meteorological and Environmental Research 2014年第7期5卷 31-33页

作者： Wang Jianchun Fujian Longking Co. Ltd. Lonjing Environment Technology Co. Ltd.

With the advantages of high combustion efficiency, wide fuel flexibility and low concentrations of discharged pollutants, circulating fluid- ized bed （cfb） boiler has been widely used in recent years. However, in order to meet the requirement of new emission standard, it＇s necessary to add flue gas desulfurization and denitration devices. In this paper, the choice of flue gas purification processes for cfb boiler has been discussed firstly, and then the economy and rationality of the SNCR ＋ cfb-FGD ＋ COA comprehensive solution to flue gas desulfurization and denitration have been analyzed.

关键词： cfb boiler Flue gas Desulfurization Denitration SNCR ＋cfb-FGD ＋COA China