Clean Coal Technology

2021年01期目次

Coal gasification technologies in China: Review and prospect
WANG Fuchen;Institute of Clean Coal Technology,East China University of Science and Technology;
In this paper,about 150 years application and development history of coal gasification technologies in China was systematically reviewed. The introduction and application process of different imported coal gasification technologies in China was described based on three periods,i.e.,before the founding of new China,from the founding of new China to the reform and opening-up and after the reform and opening-up; The important progress and achievement in the process of hard exploration,systematic research and technology demonstration and application of China's coal gasification technologies before and after the reform and opening-up were summarized; The R&D process,technological features,application and latest progress of China's self-reliance coal gasification technologies were introduced; The domestic R&D progress of new gasification technologies,such as underground gasification,catalytic gasification,hydrogasification,supercritical water gasification and plasma gasification,were briefly reviewed. Additionally,this paper also summarized the experience in introduction,independent research and industrial application of China's coal gasification technologies,and the future development of coal gasification technology was also prospected from different aspects,such as unit investment reduction,system efficiency improvement,environmental friendliness achievement,collaborative treatment of liquid/solid organic waste,integrated development with information technology,new technology development and intellectual property protection.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 34511K]

Research progress on the preparation of biodiesel and its application in flotation
ZHANG Mengni;CHENG Gan;LI Yulong;College of Chemistry and Chemical Engineering,Henan Polytechnic University;Synergism Innovative Center of Coal Safety Production in Henan Province,Henan Polytechnic University;
Petroleum is one of the bases for the survival and development of human society. Petroleum product is an important collector for fine coal flotation. The rapid development of China economy and the energy structure characteristic of " rich coal,poor oil and little gas" result in the high dependence on foreign countries. In order to alleviate the contradiction between energy supply and demand and reduce production cost,the development of new collectors is increasingly urgent. Biodiesel is similar to petrochemical diesel in property,which is renewable and biodegradable,and can be used as a substitute for petroleum products collector. The properties of biodiesel were introduced,and the feasibility of using biodiesel instead of petroleum product collector was analyzed. The main preparation methods of biodiesel were summarized: direct mixing method,hydrolysis method,homogeneous acid-base catalysis method,heterogeneous acid-base catalysis method,enzyme catalysis method,supercritical fluid method,etc. The research progress of biodiesel used as coal slime flotation collector was analyzed,and the comprehensive development trend of biodiesel in the future was put forward. The results show that compared with the traditional diesel collector,biodiesel can be used alone or mixed with petrochemical diesel,which can improve the recovery of clean coal,and can also be used for flotation of other minerals,and has a broad application prospect. In the future,further studies should be carried out on the modification treatment,mechanism research and performance optimization of biodiesel collector,so as to make it more suitable for flotation process. Further efforts should be made in the utilization and deep promotion of by-products to accelerate the sustainable and healthy development of the economy.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 2814K]

Research progress on coal water slurry particle size gradation model and practice
LI Qiang;LIAO Changlin;HOU Jian;ZHANG Jiansheng;Key Laboratory of Thermal Science and Power Engineering of Ministry of Education,Department of Power and Energy Engineering,Tsinghua University;
Coal water slurry( CWS),a coal-based liquid fuel with similar physical properties to oil,is an important way for efficient and clean utilization of coal,which can significantly reduce the emission of NOxand SO_2. At present,China's CWS demand has exceeded 250 million tons/year. Particle size gradation technology is an important factor affecting the concentration of coal water slurry,as different sizes of coal particles can be filled with each other to improve the packing efficiency of particles and the concentration of CWS. This paper analyzes the influence of particle gradation on CWS,and points out that in the CWS making process,the particle gradation only involves physical crushing and grinding,and the energy consumption is relatively small,which has significant effect on improving the concentration and has wide applicability and economy. The theory and model of particle gradation developed in recent years,especially the interlayer packing theory and fractal gradation theory,are discussed,and the specific calculation method,formula,hypothesis and applicability are given. The development and application of the interlayer packing theory in recent years and the evaluation of the packing efficiency are given by examples. The feasibility and new progress of fractal gradation theory and its application in bituminous coal and lignite CWS are analyzed. The technological process and industrial practice cases of three-peak gradation are given. Scholars have done a lot of work on the basic theory and application of particle gradation to improve CWS concentration. However,in following specific theoretical details need to be further studied: the simplified calculation of interlayer packing for arbitrary particle size distribution,the fitting accuracy of fractal gradation and the theory of three-peak gradation. In the application of gradation theory,the combination of basic theory and industrial practice needs to be further improved. It is suggested to introduce the influence of internal water and establish a prediction model for different types of coal in the future research.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 3951K]

Research progress on influencing factors and technology of low-rank coal pyrolysis
LIU Zhuang;TIAN Yishui;HU Erfeng;MA Dachao;SHAO Si;LI Moshan;DAI Chongyang;State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University;School of Resources,Environment and Materials,Guangxi University;Key Laboratory of Energy Resource Utilization from Agriculture Residue,Chinese Academy of Agricultural Engineering Planning Design Minty of Agriculture and Rural Affairs;
There are tremendous reserves of low rank coal resources in China,and the efficient utilization of coal resources can ensure the energy security. High value coal gas,tar and char can be obtained from low rank coal by pyrolysis technology,which achieveshigh value cascade utilization. In this paper,the pyrolysis mechanism of low rank coal was elucidated through three stages of pyrolysis process. In addition,the effects of pyrolysis conditions including coal rank,temperature,particle size,heating rate and atmosphere,and pretreatment methods such as acid washing,hydrothermal treatment,swelling and ionic liquid on pyrolysis reaction of low rank coal were described in detail. Besides,the catalytic pyrolysis of low rank coal is beneficial to high-quality pyrolysis products because of the directional control in pyrolysis process. Based on the differences in catalyst characteristics and catalytic behavior,the effects of different catalysts including molecular sieves,transition metal compounds,alkali metal compounds,and natural ores on the catalytic pyrolysis of low rank coal were classified. On the basis of the research status and latest development of low-rank coal pyrolysis technology,the technology of low rank coal pyrolysis for solid heat carrier,gas heat carrier and moving bed pyrolysis of internal components were summarized,and the further research direction for low rank coal pyrolysis were prospected,so as to provide a theoretical basis for the development of low-rank coal pyrolysis technology.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 6626K]

Research progress on the technology of coal catalytic hydrogasification
YAN Shuai;XIA Zihong;CHEN Caixia;QU Xuan;BI Jicheng;School of Resources and Environmental Engineering,East China University of Science and Technology;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry of Chinese Academy of Sciences;
The technology of coal hydrogasification to natural gas has the advantages of short process and high thermal efficiency.The basic research of its application has attracted much attention.However,coal structure contains large quantities of inert carbon and the hydrogenation reactivity is poor,which are hard to be converted although harsh reaction conditions(～1 000℃,～7 MPa) are applied.The reactivity of coal can be improved by adding desirable catalysts,and The carbon conversion and CH_4 yield under mild conditions can be increased simultaneously by coal catalytic hydrogasification(CCHG).The catalytic mechanism of alkali metal(K,Na,et al.),alkaline earth metal(Ca),and transition metals(Fe,Co,Ni,et al.) on hydrogasification of model carbon was reviewed.The effects of temperature,H_2 pressure and carbon structure on C-H_2 catalytic reaction process were discussed.On these bases,the optimal catalyst and process conditions forthe catalytic hydrogasification of raw coal were proposed.Moreover,the catalytic behavior of catalysts on hydropyrolysis of coal and hydrogasification of pyrolyzed coal char were analyzed,in terms of formation of CH_4 and light hydrocarbon liquids (HCL) and the evolution process of carbon structure in coal with the reaction.Finally,further research suggestions for co-production of CH_4 and HCL from CCHGwere put forward from an application perspective.The existing research results indicate that the use of iron-group metals with calcium salts(Fe/Co/Ni-Ca) as bimetallistic catalysts hasprofound catalytic performance on hydrogasifification.Transition metals mainly provide active hydrogen for C-H_2 reaction and decrease the energy for the fracture of C—C bonds.Ca mainly promotes the dispersion of transition metals and prevents its deactivation by sulfur poisoning,and enhances catalyst-carbon interaction.On the one hand,higher temperature provides higher energy for fracturing chemical bonds in coal,and accelerates the C-H_2 reaction.On the other hand,higher temperature facilitates the diffusion of the catalyst into the interior of coal matrix,and thus promotes the active hydrogen supplying and C—C bonds fracturing efficiency.Increasing pressure promotes the supply of active hydrogen,meanwhile,dilutes the concentration of CH_4,and the reaction moves to the direction of generating CH_4.In the presence of 5%Co-1%Ca at 850℃and 3 MPa,90.0%of coal conversion and 77.3%of CH_4 yield can be simultaneously achieved in 30 min.Co-Ca catalyst has the function of catalytic depolymerization and hydrogenation effect on coal during hydropyrolysis,which resulted in the promoted yield of CH_4,tar.At the same time,the catalyst has the catalytic activation effect on the coal structure in the process of coal hydropyrolysis,which makes the semi coke have higher gasification activity.The mechanism of coal catalytic hydrogenation remains in the speculation stage.In addition,the catalyst recycling performance and adaptability of gasification agent and coal type need to be further clarified.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 5742K]

Research progress on catalysts for hydrogen production by CO_2 sorption enhancement of CH_4/H_2O reforming
LIU Lu;XU Kai;JING Jieying;FENG Jie;LI Wenying;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;Key Laboratory of Coal Science and Technology,Ministry of Education,Taiyuan University of Technology;
Hydrogen production from methane steam(CH_4/H_2O) reforming enhanced by CO_2 adsorption is a potential approach to economically provide low-cost and high-purity hydrogen and reduce CO_2 emission.Catalysts and adsorbent are the important parts of the process,and activity and selectivity restrict the reaction rate and product yield.Furthermore,their lifespan will affect the production cost.In this work,the current research progress and existing problems in catalysts and adsorbents for hydrogen production by CO_2 enhanced sorption by CH_4/H_2O reforming were reviewed.It is found that when catalysts and adsorbents are mechanically mixed in the reaction,the catalytic active sites will be covered by adsorption products during the reaction process,which leads to a rapid drop of catalyst activity.Thus,the structural characteristics,research status and existing problems in the cycle regeneration process of bifunctional composite catalysts with different structures were further discussed.It is found that the bifunctional catalyst with core-shell structure has the advantages of the relative independence between adsorption components and catalyst components,the highly dispersed distribution of catalytic components,and the large specific surface area,etc.,which has the potential for further research in adsorption enhanced hydrogen production.In order to accelerate the industrial application of CO_2 enhanced sorption CH_4/H_2O reforming for hydrogen production technology,the research hotspot is to employ the structural characteristics of bifunctional catalysts to match the catalytic and decarbonization reactions in the cyclic regeneration process
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 5141K]

Research progress on sintering characteristics of high sodium coal ash
HUANG Dongdong;ZHANG Shouyu;CHANG Ming;SHI Yue;LIN Chunyu;XU Jiaqing;ZHANG Peizheng;ZHANG Hua;HU Nan;School of Energy and Power Engineering,University of Shanghai for Science and Technology;Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering;Changchun Institute of Technology;
Zhundong coal in Xinjiang with the characteristics of huge reserves,low mining cost,high volatile yield and low sulfur content,is a high-quality power coal. However,due to high sodium content of Zhundong coal,ash sintering and depositing easily occur on the heating surface during its combustion process,resulting in the serious ash deposits and slagging,which greatly limits the development and utilization of the high sodium coal. Thus,to realize the clean and efficient utilization of high sodium coal,it is necessary to fully understand the sintering characteristics of high sodium coal ash. In this paper,the research progress on the ash depositing and slagging mechanism and ash sintering behavior of high sodium coal was summarized. Furthermore,the inherent relationship between the sintering characteristic and the fouling and slagging behavior of the high sodium coal ash was explored. During the combustion process,alkali metals( mainly sodium)in coal is released into flue gas in the forms of Na_2SO_4,Na Cl and Na,which contact with the heating surface and condenses onto it to form viscous inner white layer. The fly ash particles in the flue gas can be captured by the inner white layer and reacts to form low melting point compounds,and thus,the sintering temperature decreases,and the contamination-enhanced " contamination sintering" process on the heating surface of the boiler is promoted and accelerated. The sintering process of high sodium coal ash includes: solid state sintering,liquid phase sintering and gas phase sintering. The influencing factors on the sintering process of the coal ash include reaction temperature,ash composition,ash particle size,reaction atmosphere,additives,boiler design and boiler operating conditions,etc. The additives can be divided into basic oxides and acidic oxides according to the types of oxides. Basic oxides can reduce the sintering temperature of the coal ash,and acidic oxides can increase the sintering temperature of the coal ash to some extent. The future research focuses on the development of new and low-cost additives consisting of single or mixed compound,which can fix sodium matters in the flue gas or react with low-melting sodium-containing minerals in the ash to increase the sintering temperature of high sodium coal ash. Moreover,the influence mechanism of sodium vapor on the dynamic depositing and slagging characteristics should be further studied from the micro-level. The methods for the sintering temperature measurement of coal ash are also introduced,including thermal conductivity analysis method,pressure measurement method,thermomechanical analysis method,sieving method and pressure drop method. Among them,the pressure drop method is relatively accurate for the sintering temperature measurement so far. Laboratory for Clean Conversion of Carbon-based Fuels,USST has engaged in the research on the sintering and slagging characteristics of high-sodium coal ash,in order to provide some guiding meaning for the coal combustion and utilization process.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 3105K]

Research progress on the optical diagnostics of pulverized coal ignition and combustion process
QI Hongliang;SUN Rui;PENG Jiangbo;YU Xin;ZHU Wenkun;CAO Zhen;YU Yang;GAO Long;ZHANG Zeyue;School of Energy Science and Engineering,Harbin Institute of Technology;National Key Laboratory of Science and Technology on Tunable Laser,Harbin Institute of Technology;
Coal,as an important fossil fuel,has abundant reserves. Despite the rapid development of new and renewable energy,coal resources will continue to be an important part of China's primary energy in the coming decades. However,the utilization of coal brings a lot of environmental pollution problems. As a result,the utilization of China ' s coal resources gradually transforms to the high efficiency,low carbon,and low NOxtechnology. With the rapid development of optical diagnostics technology,a variety of in situ non-invasive optical diagnostic techniques that is suitable for pulverized coal combustion diagnosis have emerged,which greatly promotes the development of the combustion science and provides more experimental methods for the clean and efficient utilization of coal. In this paper,the research progress of optical diagnosis on ignition and combustion characteristics of pulverized coal in different ways at home and abroad was introduced. The optical diagnostics research progress on ignition and combustion process of pulverized coal for both single particle and particle streams was summarized. At present,the optical diagnostic techniques used for pulverized coal combustion includes: full spectrum imaging,CH*/C2*chemiluminescence imaging,planar laser induced fluorescence( PLIF),double color/three-color pyrometer,Mie scattering,laser induced incandescence( LII),coherent anti stokes Raman spectroscopy( CARS),laser-induced breakdown spectroscopy( LIBS) and so on.The optical diagnosis research on ignition delay,devolatilization,volatile combustion,ignition mode,environmental factors( ambient temperature,oxygen concentration,atmosphere),oxy-fuel combustion,oxy-steam combustion,the release of alkali metals for both single particle and particle streams was analyzed to provide theoretical and experimental foundation for clean and efficient utilization of coal. The ignition and combustion characteristics of pyrolyzed char and Shenhua bituminous coal blended fuel were studied by using OH-PLIF and three-color pyrometer. Considering the ignition delay and the burnout ratio of the blending,the optimal blending ratio of pyrolyzed char is20%,which provides a reference for actual industrial application of pyrolyzed char. OH-PLIF diagnostic technology with high temporal and spatial resolution of 500 Hz and 5 k Hz were used to investigate the development process of volatiles combustion and the evolution process of volatiles ignition of single particle in pulverized coal particle stream. The time characteristics from ignition to volatiles combustion of pulverized coal particle stream were obtained through the combination of the two. The devolatilization and volatile combustion behavior of pulverized bituminous coal and lignite were investigated with OH-PLIF technology. The relative standard deviation of radial OH signal distribution was used to describe the flame stability. The stability of bituminous coal particle stream combustion is higher than that of lignite under the same combustion conditions. Based on OH-PLIF and CH*chemiluminescence diagnostic techniques,a dynamic mode decomposition method( DMD) was proposed to investigate the combustion oscillation characteristics of volatiles in pulverized coal particle stream.With increase of oxygen concentration,the oscillation of volatile flame is enhanced. The agglomeration of particles may lead to lower frequency oscillation for pulverized coal volatiles combustion. On the contrary,higher oscillation frequency will be produced by individual or separate particle combustion. However,the current achievements are not sufficient. So it is necessary to continue to carry out in-depth research on the optical diagnosis test of pulverized coal combustion,explore the generation and emission of NOxand the mechanism of water vapor in new water-oxygen combustion technology,and develop new clean coal combustion technology,so as to make further contribution to the clean and efficient utilization of Chinese coal resources.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 25987K]

Status and development for characteristic of ammonium bisulfate as a by-product of SCR denitrification
JIAO Kunling;CHEN Xiangyang;BIE Xuan;LIU Daokuan;MA Shuangchen;Department of Environmental Science and Engineering,North China Electric Power University;School of Energy and Environment,Inner Mongolia University of Science and Technology;
After the denitrification device using NH_3 and urea as reducing agents is installed in a coal-fired power plant,ammonium bisulfate( ABS) is formed by the reaction of reducing agent NH_3 with sulfur oxides and water vapor in the flue gas. ABS deposition will lead to the reduction of selective catalytic reduction( SCR) and the blockage of downstream thermal equipment,such as air preheater( APH) and electrostatic precipitator( ESP). The formation and deposition of ABS are related to the operating environment,but there are some unclear understandings about the characteristics of ABS in the industry. Therefore,starting from the emergence of the ABS problem,and then the reason why the wide-load denitrification of thermal power plants causes the aggravation of the ABS influence was pointed out,and the behavior of ABS formation,migration and deposition in the SCR reactor and air preheater was reviewed subsequently. The significant characteristics of ABS,such as formation method,formation temperature,dew point temperature,volatilization and deposition characteristics and decomposition characteristics were summarized. Based on the above summary,suggestions for the study of the characteristics of ABS formation-migration-volatility-decomposition-deposition were put forward,and the direction and development trend of studying the overall influence of ABS migration and volatilization characteristics on SCR and air preheaterwas pointed out.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 10249K]

Research progress on MgO sorbents for CO_2 capture
XU Yunfei;LI Yingjie;WANG Tao;LEI Wentao;School of Energy and Power Engineering,Shandong University;Shandong Naxin Electric Power Technology Co.,Ltd.;
Due to CO_2 produced by large-scale coal combustion aggravates the greenhouse effect,CO_2 capture,utilization and storage(CCUS) is a key technology to achieve large-scale carbon emission reduction at coal-fired power station.CO_2 adsorption by solid materials is considered as a promising carbon capture technology.Among many solid CO_2 adsorbents,MgO is considered as an ideal CO_2 adsorption material because of its high adsorption capacity,low cost,low regeneration energy consumption and wide availability.In this paper,the CO_2 adsorption performance of conventional MgO adsorbents was reviewed.According to the existing problems of CO_2 adsorption by MgO,the methods to improve the CO_2 adsorption performance by MgO were introduced,including the feasible methods such as optimizing the structure and adding alkali metal molten salt.Finally,the advantages and challenges of MgO adsorbents for industrial CO_2 capture were comprehensively analyzed.In addition,the research direction from the aspects of the fabrication strategy of MgO,large-scale molding of MgO pellets and CO_2 capture system design optimization using MgO in the future were prospected.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 5417K]

Porous carbon structure control and its application in the field of carbon dioxide adsorption
WANG Xiu;HAO Jian;GUO Qingjie;State Key Laboratory of Coal High-efficiency Utilization of Coal and Green Chemical Engineering;
The greenhouse effect caused by the massive emission of CO_2 has become a significant environmental problem in the world today.Coal-fired power plant is a centralized source of CO_2 emissions,which accounts for about 42% of the total emissions. Therefore,efficient capture of CO_2 in the flue gas of coal-fired power plants is imminent. The adsorption technology is considered as the most promising CO_2 capture technology for flue gas,due to simple operation,low energy consumption,easy practical application. In recent years,porous carbon adsorbents have become the current research hotspot of CO_2 capture technology due to the advantages of a wide range of raw materials,strong controllability of physical and chemical properties,and high adaptability of target adsorbates. In this paper,the preparation methods of porous carbons such as physical activation,chemical activation,carbon aerogel and template methods in recent years were reviewed. The effects of preparation methods on pore structure,element doping defects and surface properties of porous carbon were investigated. Besides,the effects of different pore structure,element doping and surface functional group modification on CO_2 adsorption capacity,cycle stability,and CO_2 adsorption selectivity in the flue gas were also described. The problems and critical technologies of porous carbon adsorption in practical application were summarized. The mechanism can be further studied in the future to prepare more efficient porous carbon for CO_2 adsorption.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 4117K]

Application status and prospects of coal chemical VOCs treatment technology
LI Hui;WANG Denghui;HUI Shien;School of Energy and Power Engineering,Xi'an Jiaotong University;
The coal chemical industry is a typical emission industry of volatile organic compounds( VOCs),involving chemical processes such as gasification,liquefaction,coking,and low-temperature pyrolysis. With the in-depth promotion of VOCs emission reduction action in China,the comprehensive treatment of VOCs exhaust gas from the coal chemical industry has been widely concerned. By analyzing the emission sources and emission characteristics of VOCs in the coal chemical industry and the advantages and disadvantages of mainstream VOCs treatment technologies,some targeted suggestions of VOCs treatment technology were given. According to the differences in the main emission sources and emission characteristics of VOCs in the coal-to-gas and coal-to-coking industries,suggestions on VOCs treatment technology were given respectively. By summarizing the technological research progress and the actual industrial application situation,the future research direction was prospected. At present,the technical system for VOCs emission accounting in the coal chemical industry is imperfect( such as the supplement and adjustment of experience coefficients,localized update of emission coefficients,etc.),the inspection system is imperfect,and the reliability of the test data is insufficient,leading to errors in the accounting results,which seriously affects the fine control of VOCs. Due to the lack of uniform and standardized industry standards,the commonly used " Guidelines for VOCs Pollution in the Petrochemical Industry" is not fully applicable to the coal chemical industry. By optimizing production technology,improving process equipment and strengthening the promotion of LADR technology,the prevention and control of fugitive emission of VOCs should be strictly controlled from the source. The technical performance,economic performance and environmental performance should be considered comprehensively in the treatment of end-point VOCs: VOCs exhaust with recycling value is given priority to use recycling treatment technology,and VOCs exhaust with low recycling value or no recycling value uses destruction treatment technology; single-end treatment technology is difficult to effectively reduce VOCs emissions,and combined technology can achieve higher purification efficiency,effectively reduce secondary pollution and reduce energy consumption. The widely used regenerative catalytic oxidation technology( RCO) has the advantages of strong applicability and good economic benefits,but it is still restricted by the performance of the catalyst. Recently,more and more combined treatment technologies have been proposed and applied,such as adsorption concentration-catalytic combustion,adsorption concentration-regenerative oxidation-adsorption,chemical absorption-photocatalysis-adsorption,chemical absorption-low temperature plasma-photocatalysis,etc. However,the reaction mechanism and interaction of combined governance technologies urgently require to be further studied. For VOCs collection and purification,treatment process,and equipment,coal chemical companies should strengthen fine integrated management,and build a technical system for source control and purification system overall supervision to eliminate human factors.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 6273K]

Research progress and prospect of coal chemical VOCs adsorption treatment technology
LIAO Zhengzhu;TIAN Hong;College of Mechanical and Electrical Engineering,Guangdong University of Petrochemical Technology;
Volatile organic compounds( VOCs) produced in coal chemical processes are complex,toxic and harmful. In order to avoid the harm of VOCs and its photochemical in coal chemical industry to the environment and human health,and based on the analysis of VOCs emission control and treatment technology,it is pointed out that the adsorption technology of VOCs is an economic and effective removal technology that can control VOCs emission,recover adsorption materials and valuable VOCs. Based on the analysis of the physical and chemical process of VOCs adsorption and its influencing factors,as well as the process and method of desorption,the modification research and development of commonly used adsorption materials were summarized and analyzed. By comparing the structure,adsorption characteristics and advantages and disadvantages of different adsorption devices,the combination of VOCs adsorption technology and other technologies in practical engineering application were compared and analyzed. Finally,the future research direction of adsorption technology was prospected. The factors that affect the adsorption process include the physical and chemical properties of adsorption materials,such as structural properties,surface chemical properties and thermal stability,the molecular properties of VOCs,the interaction between adsorbents and adsorbents,the competition between different adsorbents,and the adsorption environment,etc. The physical adsorption process includes: external surface value transfer adsorption stage,internal surface diffusion stage,equilibrium stage between pores with different pore sizes; adsorbent micropores provide the main adsorption sites,while adsorbent mesopores and macropores enhance the diffusion channels of VOCs. The adsorption material has excellent VOCs adsorption capacity after proper modification; the content of oxygen-containing functional groups on the surface of activated carbon fiber can be increased and the adsorption capacity can be enhanced by H2 O2 impregnation and modification. The surface of the activated carbon is modified by concentrated sulfuric acid with strong oxidation to enhance the adsorption capacity of the activated carbon for nitrogen. The surface area of activated carbon modified by alkaline hydroxide is increased,the surface functional groups are increased by acid modification,and the porosity is improved by KOH activation. It is necessary to select suitable adsorption devices according to the characteristics of VOCs,such as types,concentrations,flow rates and emissions.Adsorption technology is an economic,effective and promising technology to control the emission of VOCs from coal chemical industry and recycle valuable VOCs. It can be combined with other technologies to treat VOCs and recycle valuable VOCs,so as to achieve VOCs emission standard. The future research of adsorption technology can focus on the modification of adsorption materials( or directional modification),new modification methods and new adsorption materials,high-efficiency and low-cost adsorption device,simultaneous removal of multi-component adsorbate,and put forward the research idea of composite adsorption device for multi-component VOCs adsorption and desorption.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 16081K]

Study progress on the composition characteristics of fly ash from municipal solid waste incineration and treatment technology of heavy metal melting and solidification
YANG Fengling;LI Pengfei;YE Zefu;ZHANG Peihua;WU Shaohua;CHENG Fangqin;Collaborative Innovation Center of High Value-added Utilization of Coal-related Wastes,State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources,Shanxi University;Shanxi Gemeng Sino-american Clean Energy R & D Center Co.,Ltd.;
In recent years,municipal solid waste( MSW) removal volume in China has been growing at an annual rate of about 5%,and the disposal capacity of MSW incineration has also been continuously improved. In the process of MSW incineration,fly ash of MSW incineration accounts for about 3% ～ 5% of the total incineration amount. With the continuous improvement of waste incineration treatment capacity,the output of fly ash also increases year by year,and the pressure of fly ash disposal will become more and more severe. As a kind of hazardous waste leached by high heavy metals,fly ash from MSW incineration does great harm to the environment. In this paper,the MSW fly ash composition characteristics and the distribution and properties of heavy metals were discussed. The research progress of fusion treatment technology of municipal solid waste fly ash were expounded from the aspects of fly ash melting process principle,heavy metal conversion characteristics and heavy metal solidification influencing factors,and the effects of the fly ash composition and melting conditions on the melting process and the influence of the curing effect of heavy metals were investigated. Plasma melting technology was introduced,and the effect of melting and solidification of heavy metals was analyzed. At last,some reference suggestions were given for the optimization treatment of fly ash melting and cooling process,and the development direction of fly ash melting technology in the future was pointed out.Heavy metals in fly ash mainly exists in the form of the oxide,chloride,sulfate,melt treatment can change the fly ash composition and phase behavior,resulting in polycrystalline transition and melting phase transformation in the fly ash process.The heavy metal ions are solidified in the silicate Si—O tetrahedral lattice structure by isomorphic substitution reaction,which greatly reduces the leaching toxicity of fly ash and realizes resource utilization of slag. In the melting process,the melting atmosphere,time and the composition of fly ash have great effects on the process characteristics and the migration and transformation of heavy metals,and the different cooling methods will affect the physical properties of vitreous slag. According to the characteristics of melting point and boiling point of heavy metals,some heavy metals with high volatility and low boiling point will be carried in flue gas and secondary fly ash after melting treatment. In the future research,it is necessary to conduct cooling or secondary capture treatment for flue gas and secondary fly ash,and to explore the composition of flue gas. Due to the high energy consumption,high investment and difficult research and development of key equipment in the melting process of fly ash,the melting treatment technology of waste incineration fly ash is still in the technological research and development stage in China,and there is no stable chemical industry operation example. But there have been some pilot studies. Before melting treatment,the composition of fly ash should be analyzed and pretreated according to the composition of fly ash. By adding fluxing agent and adjusting the basicity of fly ash,the melting treatment of fly ash is carried out to reduce the energy consumption of melting treatment and treat heavy metals efficiently and stably. On the basis of the stable and effective test in the laboratory,the technology improvement and innovation of the plasma melting treatment device can be carried out to improve the stability of the plasma flame,realize the efficient separation of molten slag and enhance the durability of the device.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 5774K]

Research progress on the effect of residual carbon in coal gasification slag on ash and slag flow property
WANG Ji;KONG Lingxue;BAI Jin;LI Huaizhu;GUO Zhenxing;BAI Zongqing;LI Wen;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry of Chinese Academy of Sciences;University of Chinese Academy of Sciences;
Coal gasification is a process in which coal or coal char is used as raw material,oxygen( air,oxygen rich or pure oxygen),steam or hydrogen are used as gasifying agents to convert organic matter in coal or coal char into gas fuel or downstream raw materials through chemical reaction at high temperature. In the process of coal slagging gasification,the organic matter in coal is converted into syngas,and the minerals are gradually transformed into solid ash after sintering and melting and then further converted into liquid slag. Because the organic matter in coal cannot be completely transformed in the process of gasification,there are unreacted coal char particles in the gasification slag,which leads to the formation of residual carbon in the gasification slag. The presence of residual carbon not only reduces the carbon conversion of coal gasification,but also has an important impact on the flow property of the coal ash. In this paper,the formation mechanism of residual carbon in ash and slag from slagging gasifier and the latest development of research on effect of residual carbon on flow property of ash and slag in recent years were reviewed. Firstly,the formation reason of residual carbon in coal gasification slag was analyzed. It is found that coal ranks and operation conditions are the main factors affecting residual carbon content in ash,while the interaction between residual carbon and slag determines occurrence of residual carbon in ash. In order to optimize operation conditions and reduce residual carbon in gasification ash,it is necessary to further study the influence of gasification conditions and ash composition on interaction between residual char and slag. Some researchers separated residual carbon by flotation and acid leaching to analyze its characteristic. Compared with low-temperature coal char,residual carbon in ash has less volatile,more pores,high graphitization degree and poor reactivity due to its high temperature and long residence time in gasifier. As an important component of ash,the presence of residual carbon significantly improves the ash melting temperature. In addition,the graphitization degree of residual carbon and the chemical composition of coal ash( Si/Al,Fe_2O_3 content) show great influence on the fusibility of coal ash containing carbon. The existence of residual carbon leads to formation of refractory minerals such as Fe Si,Si C and Fe. During the cooling process,the residual carbon promotes the crystallization of minerals in the slag and improves the viscosity of the slag. However,there is a lack of systematic study on the reduction rate of iron by residual carbon and its influence on crystallization behavior of mineral in different slags. Besides,residual carbon is prone to react with silicon and iron mineral. The temperature and rate of carbothermal reaction is influenced by composition of carbothermal reactants and diffusion of products. Thus,it is necessary to study the kinetics of carbothermal reaction under different gasification conditions.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 25453K]

Advances on dust removal technology of high temperature pyrolysis of coal gas containing dust and oil
YANG Shuaiqiang;DU Lin;LI Songgeng;SONG Wenli;State Key Lab of Multi-phase Complex Systems,Institute of Process Engineering,Chinese Academy of Sciences;School of Chemical Engineering,University of Chinese Academy of Sciences;Sino-Danish College,University of Chinese Academy of Sciences;
The problem of dust removal from high temperature pyrolysis gas is one of the important reasons affecting the large-scale application of coal pyrolysis technology. According to the characteristics of the dust carried by high-temperature pyrolysis gas,the research progress of high-temperature dust removal technology of dust containing pyrolysis gas were analyzed,the characteristics of dust removal technology of high-temperature pyrolytic gas were discussed. According to the characteristics of high-temperature dust removal technology of dust containing pyrolytic gas,the future research direction of pyrolysis gas dust removal technology was prospected. The pyrolysis gas containing dust has the characteristics of complex composition,sensitive to temperature,easy condensation of heavy components,small particle size of dust and difficult separation. The cyclone separator is used for the dust removal of pyrolysis gas,and the dust removal efficiency of coarse dust with particle size greater than 10 μm is high,which is generally used as the pre-separator of pyrolysis gas dust removal. Electrostatic precipitator,metal microporous filter and granular bed filter have higher efficiency for dust with smaller particle size in high-temperature dust-containing pyrolytic gas,which are suitable for fine dust removal. The results of the pyrolysis gas dust removal technology show that if the filtration temperature is too low,the tar is easy to condense,causing the decrease of oil and gas yield. If the temperature is too high,the secondary reaction of the pyrolysis vapor will be intensified,which causes serious carbon deposition in the filtration process and affects the operation cycle of the dust collector. In terms of the dust removal efficiency of high-temperature dust containing pyrolysis gas,the metal microporous dust removal technology has the highest filtration efficiency,which is more than 99%. The filtration efficiency of granular bed filter for high-temperature pyrolysis gas is more than 90%. Affected by the temperature,the filtration efficiency of electrostatic precipitator is generally less than 90% when the temperature is higher than 400 ℃.In the same filtration time,the metal microporous filtration technology has the highest filtration pressure drop,the electrostatic precipitator has the lowest pressure drop,and the pressure drop of granular bed filter is between the two. Electrostatic precipitator technology has the characteristics of " double low" of pressure drop and filtration efficiency. Therefore,on the basis of optimization of process conditions,the development of new electrode materials becomes its development direction. Metal micropore filtration technology has the characteristics of high filtration efficiency and high pressure drop. The development direction of metal mesh technology is to develop low-cost,high temperature resistant,corrosion-resistant carbon deposition resistant materials,and regulate the structure and distribution of metal mesh. In the process of granular bed dust removal,there are some problems such as carbon deposition of filter material and secondary reaction of pyrolysis vapor. In the future,it will be an important research direction of granular bed dust removal technology to develop new dust removal filter material and achieve the integration of dust removal and quality improvement. In the process of dust removal of pyrolysis gas,various dust removal technologies have their own unique characteristics. Based on the advantages of the existing technology,it is expected to ensure the high efficiency and stable operation of the dust removal process through the technical combination. At present,most of the pyrolysis gas dust removal technologies are in the stage of pilot and demonstration projects. However,the pilot experiment has a short time and lacks long-term operating data. In the future,it is necessary to strengthen the research on the realization of engineering application of pyrolysis gas dust removal technology.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 4802K]

Study on the X-ray recognition law of intelligent sorting by mineral components
ZHU Jinbo;YIN Jianqiang;YANG Chenguang;ZHOU Wei;ZHU Hongzheng;ZHANG Yong;SHI Qinghui;ZENG Qiuyu;GUO Yongcun;YANG Ke;School of Materials Science and Engineering,Anhui University of Science and Technology;
Aiming at the problems of selection and separation basis in the intelligent separation process of coal and gangue,the change rule of gray value of mineral and coal with different nature at different scales and densities was studied by X-rays identify minerals principle and image grayscale extraction method. The results show that the grayscale value of single mineral and mixed mineral decreases gradually with the increase of thickness and density. At the same thickness,the higher mineral density is,the smaller the gray value is,and this result is also applicable to different coal type. The regression equation for single mineral and mixed mineral was obtained by regression analysis method. The regression equation coefficients a of graphite,quartz,kaolin and montmorillonite in high and low energy regions are 59.25,65.69,61.61,58.02 and 174.95,177.31,186.95,161.81,respectively. Graphite is mixed with other three minerals to produce graphite ∶quartz,graphite:kaolin,graphite:montmorillonite,graphite:kaolin:quartz,graphite: montmorillonite:kaolin,graphite:quartz,graphite:montmorillonite:kaolin,and the regression equation coefficients in high and low energy regions are 151.12,156.00,153. 13,152.43,152.98,151.98 and 193.34,201.34,192.93,191.26,194.68,193.08,respectively. Then,the regression equation of single mineral was used to verify the mixed minerals. It is found that the gray-scale interval corresponds to the density interval,which conforms to the principle of X-ray recognition. The gray-scale values of different kinds of coal( coking coal,fat coal,gas coal) have a highly significant regularity with their thickness and density,and the change trend was consistent with that of single mineral and mixed mineral.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 9789K]

Experimental study on co-degradation of polyacrylamide in coal slime water by mixed bacteria
ZHANG Dongchen;WANG Fanglue;WANG Tao;DAI Wen;School of Material and Engineering,Anhui University of Science and Technology;
In order to solve the problems of residual polyacrylamide( PAM) in the coal slime water,such as reducing the flotation performance and polluting the environment. Firstly,the mixed strain was formed by combining Phanerochaete chrysosporium( P. chrysosporium) and Rhodopseudomonas spheroides( R. spheroides) in equal volume. The effects of environmental factors and nutritional conditions on PAM degradation were investigated by mixed strain. Secondly,the degradation products were analyzed by FT-IR and viscosity method. Finally,the enzyme activity of degradation culture was tested. The results indicate that P. chrysosporium and R. spheroides can degrade PAM with degradation rate of 30.2% and 24.9%,respectively when added separately. The mixed strain degradation rate of PAM reaches 34.3%. The degradation rate of PAM reaches 37.5% under the optimal conditions. Different conditions will lead to significantly different degradation effects. A small amount of the glucose and the ammonium tartrate can promote the degradation,and the temperature has a significant effect on the degradation of PAM. The amide group of the side chain of PAM is converted into carboxyl group,which can be used as nitrogen source for microorganisms. The carbon chain skeleton of PAM is broken under the action of strong oxidase,resulting in the decline of molecular weight,which can provide carbon source for microbes. Laccase,manganese peroxidase and lignin peroxidase are detected in the degraded fermantation liquid with enzyme activity of 16.48 U/m L,12.09 U/m L and 6.73 U/m L,respectively.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 7012K]

Effect of non-ionic dispersant on the preparation of CWS from low rank coal
LIU Yaoyao;LI Qianwen;XU Chenggong;LI Lin;College of Chemical and Biological Engineering,Shandong University of Science and Technology;
In order to improve the poor quality of coal water slurry from low rank coal and realize the efficient and clean utilization of low rank coal,nonylphenol polyoxyethylene ether( NPEO-40),a non-ionic surfactant,was used as dispersant to prepare low rank coal water slurry. The research on the slurrying performance and the mechanism of coal water slurry was carried out. The test of Shendong coal( SDC)low-rank coal water slurry shows that the apparent viscosity η100 of coal water slurry decreases with the increase of NPEO-40 dosage.When the dosage of NPEO-40 increases to 1.0%,the apparent viscosity η100 remains basically constant. When the dosage of additive is1% and the concentration of coal water slurry is 60%-68%,the slurry is a pseudoplastic fluid with shear thinning,and the maximum slurry concentration C1000 is 67.5%. When the concentration range of low rank coal water slurry is 60%-68%,the stability of slurry decreases with the increase of concentration. Isothermal adsorption studies show that the adsorption behavior of NPEO-40 on low rank coal surface is in accordance with Langmuir isothermal adsorption model and Gibbs free energy ΔGa0 dsis-29.27 k J/mol,proving that the reaction occurs spontaneously. The infiltrating experiment shows that when the dosage of NPEO-40 is 1.0%,it will be beneficial to the coal infiltration in the solution. XPS narrow-range scanning is performed on the coal before and after adsorption,and the content of C—C/C—H functional group decreases from 78.79% to 70.12%. The total amount of oxygen-containing functional groups C—O,C■O,and O■C—O increases from 21.21% to 29.88%,indicating that the hydrophobic functional group of NPEO-40 is combined with the C—C/C—H functional group on the coal surface after adsorption of NPEO-40. Therefore,the oxygen-containing functional group is exposed to the outside,thereby reducing the content of C—C/C—H functional group on the coal surface. The proportion of oxygen-containing functional groups increases and the hydrophilicity is enhanced,which is conducive to the formation of a hydration film. The pulverized coal particles are separated from each other through the hydration film,thereby reducing the flow resistance between the pulverized coal particles and achieving a viscosity reduction effect.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 6259K]

Study on hydrothermal upgrading of Zhundong coal and catalytic gasification characteristics of its derived liquid
CHEN Xuan;ZHANG Xiaopei;YU Shenghui;ZHANG Cheng;Guangdong Energy Group Zhuhai Power Plant;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
Zhundong coal( ZD) has a high content of alkali metals( especially Na and Ca),and its direct combustion as steam coal will cause serious boiler contamination and slagging. The hydrothermal upgrading method can effectively remove alkali metals from coal and can also improve the physical and chemical properties of coal,therefore,it has been widely studied. However,hydrothermal upgrading will also generate a large amount of waste liquid,resulting in the loss of organic matter and low energy efficiency of raw materials,which limits the application of this method. In response to the above problems,the hydrothermal upgrading technology was coupled with the waste liquid gasification technology,and the experimental research on the hydrothermal upgrading of ZD and the derived waste liquid catalysis on the hydrothermal reactor and the self-made two-stage reactor was carried out. The distribution characteristics of the three-phase products after upgrading and the catalytic gasification characteristics of the waste liquid were also explored. The results show that as the hydrothermal temperature increases,the solid recovery rate of coal samples decreases,and the total organic carbon( TOC) and gas products in waste liquid increase significantly,but at least 97.8% of carbon elements are distributed in solid phase products. Catalytic gasification of waste liquid produces combustible gas rich in CH_4 and H_2,with the highest proportion reaching 70%. It is found that Ni element in Ni/C catalyst plays a catalytic role in the gasification of waste liquid. The catalytic efficiency increases with the increase of hydrothermal temperature and vaporization temperature,and decreases with the increase of liquid hourly space velocity. The preferred catalytic gasification experimental conditions are: Ni/C catalyst,hydrothermal temperature of 300 ℃,catalytic gasification temperature of 350 ℃ and liquid hourly space velocity of 150 h-1. In short,the combined technology of hydrothermal upgrading-waste liquid catalytic gasification technology( HT&CHTG-Process) can not only realize the modification of coal quality,but also recover the energy in the waste liquid,which can provide new ideas for the clean and efficient utilization of ZD.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 11635K]

Simulation study on chemical looping gasification of typical coal in Western China based on Aspen Plus
PAN Xin;HU Xiude;MA Jingjing;YUAN Nini;GUO Qingjie;State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University;
In the face of global warming,it is urgent to develop new comprehensive utilization technology of coal with low energy,low carbon and environmental protection. Chemical looping technology is a new technology of chemical conversion and energy utilization. Aspen Plus software was used to establish the chemical looping gasification process. The influence of typical coal and moisture content on chemical looping gasification process in western China was simulated on a pilot scale. Combined with the coal composition and gasification process,the reasons for different syngas content produced by different coal types were analyzed. The method to simulate different moisture content in coal was proposed to analyze how moisture affects chemical looping gasification process,which provided theoretical guidance for pilot scale enlargement. The results show that the syngas yield of coal of Yangchangwan Coal in Ningxia( NX) and Shenmu coal in Shaanxi( SX) is higher than 2. 0 Nm3/kg( coal),and the cold gas efficiency is higher than 0. 9. The syngas yield from coal of Zhaotong coal in Yunnan( YN) is lower than 1.0 Nm3/kg( coal) and the cold gas efficiency is the lowest. The syngas yield and the cold gas efficiency are as follows: NX>SX> Yili coal in Xinjiang( XJ) > Erdos coal in Inner Mongolia( NM) >YN. Because moisture increases steam and carries away heat,the higher the moisture content in coal is,the worse the gasification is. When the water content in coal drops from22.38%( wt) to 0,the yield of syngas increases and the efficiency of cold gas increases by 34.5%.The heat required for gasification reactors is reduced by 8.89%. Therefore,in terms of raw material selection,in order to get more syngas,coal with high fixed carbon,less moisture and low volatile matter should be selected as raw material. The drying device is added before the coal enters the gasifier to improve the yield of syngas and the efficiency of cold gas.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 3815K]

Diagnosis of the operation state of entrained flow coal water slurry gasifier burner based on qualitative trend analysis
LI Shanshan;GONG Yan;GUO Qinghua;YU Guangsuo;Institute of Clean Coal Technology,East China University of Science and Technology;
Entrained flow coal-water slurry( CWS) gasification technology is a clean and efficient coal energy utilization technology,and the gasifier burner is one of the core equipment of the gasification process. The burner will be gradually worn and ablated during the operation process,and there is a potential safety hazard. However,the diagnosis of burner operation status mainly depends on the engineer's experience in addition to the interlock of the burner itself. Qualitative trend analysis( QTA) is a data-driven method based on process history,which is widely used in process monitoring and fault diagnosis. In this paper,QTA method was applied to the data analysis of entrained flow CWS industrial gasification devices to explore the difference between the operating data of gasification device with different burner working time. A diagnosis method based on the difference of data fluctuation was proposed to judge the operation status of burner in time.The trend primitive sequence and the change rate of primitive segmented data of the gasification plant production data of two different burner operating hours were compared. The results show that the growth of burner operating time is mainly reflected in the data fluctuation frequency and amplitude In two respects. The longer the burner operating time is,the greater the fluctuation range of the four sets of data of coal slurry flow,burner pressure difference,slag mouth pressure difference and outlet syngas CH4 content is,and he higher the fluctuation frequency is. In practical applications,the operating status of the burner can be judged by comparing the fluctuation frequency and amplitude of the burner data. Two types of parameters are mainly monitors: the trend primitive sequence and the data change rate of the trend primitive segment. When the primitive sequence frequently shows the opposite trend or when the data change rate increases to several times of the initial parameters,it can be considered that the operating state of the burner has become unstable,and it is necessary to monitor the operation of the burner or replace the burner. The diagnostic method based on the difference of data fluctuations can help the operator to judge the operating status of the burner in time,and realize the combination of computer-aided judgment and industrial big data.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 8896K]

CFD simulation of pseudo bubble-emulsion drag model in a large-scale high-temperature Fischer-Tropsch fluidized bed reactor
WANG Teng;XIA Zihong;CHEN Caixia;School of Resource and Environmental Engineering,East China University of Science and Technology;
In this paper,three-dimensional computational fluid dynamics( CFD) simulation of a large-scale high-temperature Fischer-Tropsch fluidized bed reactor was carried out. The traditional two-fluid model is based on the assumption of homogeneity at the level of computational cells,which assumes that the gas and solid phases are uniformly distributed within a cell and the mesh size must be small enough to properly reveal all the details of the local heterogeneous structure. When the two fluid model is used to simulate large-scale industrial fluidized bed reactors,the number of grids will be too large,which is far beyond the existing computing capacity. In order to improve the simulation efficiency without losing the simulation accuracy,a pseudo bubble-emulsion triple-phase drag( PBTD) model based on the assumption of local heterogeneity and applicable to coarse meshes was proposed. In this model,the fluidized bed is divided into three phases:emulsified phase gas,emulsified phase particle and bubble. A conservation equation is established for each of the three phases to reflect the effect of the heterogeneous characteristics of the bubbles on the gas-solid drag force. The gas-solid drag force within the emulsion phase and the drag force between the bubble phase and the particles in the emulsion phase are considered separately. A three-dimensional flowtransfer-reaction model of the high-temperature Fischer-Tropsch reactor based on the assumption of local heterogeneity is established using the PBTD model coupled with the mass transfer and reaction models,including the conservation control equations of each phase,the bubble size model,the interphase mass and momentum exchange model,the high-temperature Fischer-Tropsch reaction kinetics model,and the initial and boundary conditions to predict the flow hydrodynamics and gas component concentration distribution. The results show that under the condition of coarse grid,the proposed heterogeneous drag model can obtain good results of the distribution of phase holdup in the bed,and the predicted bed expansion height is in good agreement with empirical correlation with a deviation of 1.2%. The mass fraction of the gas compositions at the reactor outlet is close to measurement values,and the deviations are in the range of 1.5%-16.0%. The simulation results show that the PBTD model is suitable for simulating industrial scale bubbling fluidized bed reactors,which has guiding value for application in the design and operation of industrial reactor.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 9386K]

Effect of surface area on electrochemical performance of coal-based capacitive carbon
ZHANG Fengmei;SHAO Qizhen;ZHANG Buqin;WANG Qian;HUANG Guangxu;ZHANG Zhaohua;LI Yuanyuan;SU Yifan;ZHANG Chuanxiang;College of Chemistry and Chemical Engineering,Henan Polytechnic University;Jizhong Energy Fengfeng Group;
In this paper,using Hebei anthracite as raw material and KOH as activator,coal-based capacitive carbon with high specific surface area was prepared by chemical activation method. The effect of specific surface area of coal-based capacitive carbon on the electrochemical performance of double-layer capacitor in inorganic/organic system was investigated. The results show that the specific surface area,total pore volume and mesopore ratio of the prepared capacitor carbons increase with the increase of alkali-coal ratio. When the alkali-coal ratio reaches 3. 5,the specific surface area,total pore volume and mesopore ratio of the prepared capacitor carbon are3 389 m2/g,2.041 cm3/g and 49.9%,respectively. It can be seen that for the inorganic/organic system,the change rule of the electrochemical performance of the capacitor varies slightly under the same specific surface area change law. When the ratio of alkali to coal is less than 2,the specific surface area of the prepared capacitor carbon is less than 2 400 m2/g. In this case,for the inorganic/organic system,the variation of the specific capacitance of the capacitor is the same,and the specific capacitance increases obviously with the increase of the specific surface area. When the ratio of alkali to coal is greater than 2,the specific surface area of the prepared capacitor carbon is greater than 2 400 m2/g. As the specific surface area continues to increase,the specific capacitance of the electrode material for the inorganic system almost remains unchanged,and the maximum specific capacitance reaches 331 F/g. For the organic system,the specific capacitance of the electrode material increases slowly,and the maximum specific capacitance reaches 192 F/g. When the ratio of alkali to coal is 2,the specific surface area of capacitor carbon is 2 382 m2/g. In this case,both for inorganic and organic systems,the capacitor has a relatively high specific capacitance retention rate while maintaining a relatively high specific capacitance. Therefore,to some extent,It is conducive to improving the electrochemical performance of supercapacitors by increasing the specific surface area of electrode materials. The preparation of capacitive carbon with appropriate specific surface area can not only get capacitors with higher capacitance performance,but also control the cost effectively. At the same time,the preparation of capacitive carbon with coal as raw material can enhance the added value of coal and has a good market prospect.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 10938K]

Numerical simulation study on the effect of air distribution on combustion of coal-fired boiler blended with sludge
MENG Tao;XING Xiaolin;ZHANG Jie;ZHOU Lei;ZHANG Tao;WANG Chang'an;Anhui Huainan Pingwei Power Generation Co.,Ltd.;State Key Laboratory of Multiphase Flow in Power Engineering,Xi'an Jiaotong University;Shanghai Power Equipment Research Institute Co.,Ltd.;
The present study on coal-fired coupled sludge power generation technology mainly focused on the influence of mixing ratio,but the effects of factors such as the excess air coefficient in the main combustion zone are still unclear. In view of this point,the eddy dissipation model was used to simulate the municipal sludge combustion in a 600 MW tangentially fired boiler. The effects of sludge blending ratio,excess air coefficient in the main combustion zone and secondary air distribution mode on the sludge mixing combustion and NOxgeneration characteristics in coal-fired boiler were analyzed. The results show that as the sludge blending ratio increases,the overall temperature of the furnace decreases,which affects the stability of combustion,and the NOxconcentration at the outlet of the furnace decreases. When the blending ratio of sludge increases to 20%,the furnace outlet temperature drops by about 100 K,and the NOxconcentration decreases by53.2%. However,the blending ratio has little effect on the velocity field distribution in the furnace. As the excess air coefficient of the main combustion zone increases from 0. 72 to 0. 96,the furnace outlet temperature increases slightly,only by about 15 K,while the NOxconcentration increases significantly,from 174.39 mg/m3 to 352.09 mg/m3,which is about an increase of 50.4%. Within the range of excess air coefficient in this paper,considering temperature and NOxconcentration,it is recommended that the excess air coefficient of the main combustion zone is 0.84. The influence of different secondary air distribution on the co-combustion of sludge in coal-fired boilers is quite different. In the five air distribution modes,the furnace outlet temperature and NOxconcentration change greatly. The furnace outlet temperature under the condition of air distribution at the waist is the lowest at 1 289 K,while the inverted tower air distribution temperature is the highest at 1 341 K. At the same time,the NOxconcentration of the drum waist air distribution is higher,which is 207.77 mg/m3,and the beam waist air distribution is lower,which is 156.42 mg/m3. Considering the temperature and NOxconcentration,the secondary air distribution is recommended to adopt the beam waist distribution mode.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 13336K]

Influence of characteristic elements in coal on ash formation characteristics of pulverized coal under high temperature oxy-fuel combustion
LIU Zhuang;WU Xiaofeng;FAN Weidong;ZHANG Xiang;LIU Yu;School of Mechanical and Power Engineering,Shanghai Jiao Tong University;Shanghai Boiler Works Co.,Ltd.;
Fouling and slagging is one of the main problems in the operation of oxy-fuel combustion boilers. Due to the difference in radiant heat transfer and chemical properties of CO2 comparing to N2,the fouling and slagging on the inner wall of oxy-fuel boilers is more serious. In recent years,scholars carried out systematic analyses on the fouling and slagging of coal ash under the condition of oxy-fuel combustion,and obtained more detailed results. However,there is still a lack of research on the ash formation of pulverized coal combustion based on the characteristic elements and atmosphere under oxy-fuel combustion. In this paper,the key elements Ca,Na,Fe in pulverized coal slagging were selected as characteristic elements,and the oxides or hydroxides of characteristic elements were selected as additives. Shanxi Anthracite with Al and Si as main ash components was employed as the experimental coal to quantitatively study the influence of characteristic elements on high temperature ash formation characteristics of coal under oxygen enrichment. It has found by experiment that when the content of characteristic elements is higher,the reaction time of pulverized coal in an oxygen-enriched atmosphere is reduced by 20-50 min compared with that in air atmosphere,and as the oxygen concentration increases,the reaction time of pulverized coal gradually increases; the ash melting point of high Fe coal and high Na coal is about 150 ℃ lower than the benchmark coal,but Ca has no obvious influence on the deformation temperature of coal ash. At the case of oxy-fuel combustion,calcium aluminosilicate and mullite will appear in the high-Ca coal as the oxygen concentration increases,and aluminosilicate such as anorthite is formed,and the amorphous phase of Na and Fe is strengthened as the temperature increases. The Fe in high-Fe coal changes from oxide to ferric aluminosilicate as the oxygen concentration increases. As the temperature increases,the content of enstatite and magnetite increases. The content of calcium iron silicon oxide and calcium-iron-silicon oxide first increases and then decreases. The coal ash obtained from the low-oxygen combustion of high-Na coal mainly consists of nepheline. The increase of oxygen concentration causes the gradual conversion to form sodium silicate. As the temperature rises,the form of Na changes from stable acid salt to sodium silicate salt or other stable amorphous transformation.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 14770K]

Thermal experimental study on co-combustion of pyrolysis semi-char and coal with different volatile content
CHEN Dengke;YAN Yonghong;PENG Zhengkang;WANG Xingyi;SUN Liutao;SUN Rui;School of Energy Science and Engineering,Harbin Institute of Technology;
Semi-char is the product of low-rank coal pyrolysis at low temperature,which requires higher temperature for its ignition and stable combustion than raw coal.In order to expand semi-char's application in power plants and other fields,it is necessary to introduce some combustible and high-volatile coals as co-combustion fuel.On the other hand,domestic and foreign research on blended coal combustion is mostly based on small-scale test benches and numerical simulations,rather than pilot scale test systems.Therefore,the thermal experimental study was conducted to investigate the influence of different volatile content(lignite,bituminous coal,sub-bituminous coal) on the mixed combustion with Shenmu pyrolysis semi-char in a 350 k W pulverized coal-fired pilot-scale furnace.The furnace temperature at different axial and radial positions,and concentrations of gaseous species(O_2,CO,CO_2and NO_x) at furnace axis were measured in the primary combustion zone to study the effects of blended coal quality change on ignition,NO_xemission and burnout characteristics for co-combustion(the quality blend ratio of semi-char is 50%).The research results show that the ignition and combustion of the fuel-rich jet is better than that of the fuel-poor jet,and the O_2consumption and flue gas generation are also mainly concentrated on the fuel-rich jet.With the increase of dry ash-free volatile(V_(daf)) content in blended coal,the stand-off distance of blended coal decreases,the ignition temperature reduces,and the distance between the burner outlet and the stable combustion zone is shortened.At the exit section of the primary combustion zone,the NO_xemission concentration of the mixed jet for lignite+semi-coke,bituminous coal+semi-coke,and sub-bituminous coal+semi-coke are respectively 473,462 and 532 mg/m~3(under 6%O_2,the same below),while the difference of NO_xconcentration of lignite/semi-char and bituminous/semi-char jet is only 11 mg/m~3.Considering the ignition distance,combustion intensity and NO_xemission from the primary combustion zone comprehensively,the V_(daf)content which is not less than 16%is suitable for co-combustion(the quality blend ratio of semi-char is 50%).
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 14820K]

Performance research on deep peak regulation with flue gas recirculation in a 330 MW subcritical CFB boiler
ZHANG Sihai;ZHANG Shuangming;ZHANG Junjie;MIAO Miao;WANG Jiaxing;ZHANG Man;YANG Hairui;Ningxia Guo Hua Ningdong Power Generation Co.,Ltd.;State Key Laboratory of Power Systems,Department of Energy and Power Engineering,Tsinghua University;Yantai Longyuan Power Technology Co.,Ltd.;
To consume renewable energy,the Circulating Fluidized Bed( CFB) boiler units can play great role in the deep peak regulation and operation flexibility with its strong peak regulation capability. However,due to the safety limitation of fluidization in dense phase zone under ultra-low load operation,the total amount of primary air cannot continue to decrease,which destroys the inherent reductive characteristics of staged primary and secondary air and causes more nitrogen oxides to be formed. In the meanwhile,the furnace outlet temperature is much lower than the temperature window of selective non-catalytic reduction( SNCR),which causes efficiency drop of denitration system in the separator. Flue gas recirculation technology is a kind of low-load NOxcontrol technology suitable for CFB boilers. In this paper,the comparison of operating performance before and after the flue gas recirculation modification in a 330 MW subcritical CFB boiler unit was introduced. The results show that under low load conditions,flue gas recirculation technology can significantly reduce the primary air volume while maintaining the safety of fluidization in the dense zone,strengthen the reducing atmosphere and reduce the temperature in the dense zone,delay the combustion in the furnace,and significantly improve the flue gas temperature at the furnace outlet,which greatly avoid the reduction of SNCR efficiency in the separator. At last,a reasonable operation control strategy was provided for the corrosion in the flue gas recirculation system.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 5859K]

Effect of particle shape on the concentration measurement of particle mass with light extinction method
XIA Jisheng;ZOU Jun;WU Kai;TAN Zixing;HUANG Jing;HUANG Guohui;HUANG Weizhen;HAN Jinke;LIU Xiaowei;SPIC Jiangxi Electric Power Co.,Ltd.;Nanchang Kechen Electric Power Test Research Co.,Ltd.;Jingdezhen Power Plant,SPIC Jiangxi Electric Power Co.,Ltd.;Hudian Hubei Power Generation Co.,Ltd.;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
As one of the primary sources of atmospheric particulate matter,the emissions of particulate matter( PM) from coal-fired power plants have been widely concerned. It is of great significance to realize the accurate on-line monitoring of PM mass concentration. As a commonly used on-line measurement method for PM concentration,the light extinction method is likely to cause a large deviation due to the influence of particle characteristics. To explore the effect of particle shape on the mass concentration measurement,the light extinction test rig was set up,and the test system was calibrated by spherical silica particles. The calibration results show that the mass concentration of spherical silica particles is highly linearly related to the extinction ratio,the correlation coefficient R2 is greater than 0.99,and the deviation between the measured concentration and the actual concentration is only 1.8%. Furthermore,three kinds of non-spherical( prismatic,irregular and flaky) silica particles were tested with two wavelengths at 633 nm and 532 nm respectively. The results show that the mass concentration of the three kinds of particles is highly correlated with the extinction ratio,and R2 is higher than 0.99; the deviation of the measured value and the actual value of the three shapes of particle mass concentration varies with the shape of the particles and the incident wavelength. When the incident wavelength is 633 nm,the measured deviations of the mass concentration of irregular,prismatic and flake particles from the actual value are 16.1%,27.4% and 36.6%,respectively. When the incident wavelength is 532 nm,the measurement deviations of the mass concentrations of three kinds of particle are 4.8%,11.4% and 17.4% respectively; under the condition of the same particle shape,the measurement deviation at the incident wavelength of 532 nm is significantly smaller. The measurement deviation caused by the change of particle shape can be reduced by the selection of the wavelength.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 11371K]

Study on the model for controlling arsenic emissions from blended coals combustion
CAO Na;YU Shenghui;XU Hao;ZHANG Cheng;Department of Energy and Power Engineering,Wenhua College;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
Blended coals combustion is an effective method to control arsenic emissions from coal combustion,but due to the lack of relevant coal blending models,the application of this technology is limited. Based on the mechanism of arsenic volatilization and release in coal combustion process,a coal blending model was proposed,in which arsenic release index P was used to describe arsenic release characteristics during coal combustion. The ash content of coal,the content of mineral elements in each ash,the fixed coefficient of arsenic of each mineral element,and the arsenic content in coal were considered in this model. The results demonstrate that with the increase of coal ash fixation coefficient from 23. 12 to 50. 90,the arsenic adsorption capacity in coal ash increases from 3. 39 mg/g to 6.14 mg/g. The fixed rates of arsenic decreases with the increase of the release index P,and with the increase of temperature,the correlation increases from 0.67 at 900 ℃ to 0.86 at 1 300 ℃.According to the P value,the coals are screened for blending combustion. When the difference in P value of blended coals is large,the low P value coal can not only reduce the arsenic content in the blended coals,but also promote the enrichment of arsenic in the high P value coal,which is up to 77.14%. However,when the P value difference of the blended coal is small,the combustion of blended coal with low P value will promote the release of arsenic. This model can be used to screen coal types well and provide a new idea to control the emission of trace elements such as arsenic by blended coals combustion.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 6120K]

Experimental study on kinetic characteristics of ACF electro-sorption process and influencing factors of desalination
MA Lan;HUANG Luyue;XU Yongyi;WANG Feng;LIU Chang;MA Shuangchen;Department of Environmental Science and Engineering,North China Electric Power University;China Power Hua Chuang Electricity Technology Research Co.,Ltd.;
In recent years,the treatment intensity and discharge standards of various types of sewage have been continuously improved.Among them,industrial wastewater has greater water saving and reuse potential. An efficient and low-cost desalination technology is urgently needed. At present,electro-sorption technology is widely used in the field of water treatment by virtue of its low energy consumption,no need to add chemicals,and high salt removal efficiency. The rapid desalination of wastewater by electro-sorption technology mainly needs to start from two aspects: the increase of desalination speed and high-throughput water production. The kinetic factors determine the adsorption rate of ions inside the adsorbent,and the adsorption capacity determines the salt removal rate. Therefore,exploring the kinetic characteristics of the electro-sorption process and the influencing factors of desalination is the key to this technology. Using activated carbon fibers as electrodes,multiple sets of electro-sorption tests were carried out in a self-made plate-type electro-sorption device using activated carbon fibers as electrodes. In this paper,the effects of solution concentration,applied voltage,p H value and temperature on its salt removal efficiency and saturated adsorption capacity were studied,and the electro-sorption kinetics results under different voltages and different concentrations were fitted. The kinetic study indicates that voltage is the main factor affecting the ion adsorption rate. When the voltage is less than 0.8 V,it is suitable for pseudo-second-order kinetic equation,and when the voltage is greater than 0.8 V,pseudofirst-order kinetic model is applicable. The higher the voltage is,the faster the adsorption rate is. The adsorption isotherm research shows that electro-sorption capacity increases with the increase of voltage and initial concentration,and the adsorption process conforms with the Langmuir adsorption isotherm model. Weakly acidic condition is conducive to the improvement of electro-sorption desalination performance. The increase of temperature inhibits ion adsorption,and room temperature is best experimental temperature.
2021 01 v.27;No.131 [Abstract][OnlineView][HTML全文][Download 6930K]

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2021年01期目次

Coal gasification technologies in China: Review and prospect

Research progress on the preparation of biodiesel and its application in flotation

Research progress on coal water slurry particle size gradation model and practice

Research progress on influencing factors and technology of low-rank coal pyrolysis

Research progress on the technology of coal catalytic hydrogasification

Research progress on catalysts for hydrogen production by CO_2 sorption enhancement of CH_4/H_2O reforming

Research progress on sintering characteristics of high sodium coal ash

Research progress on the optical diagnostics of pulverized coal ignition and combustion process

Status and development for characteristic of ammonium bisulfate as a by-product of SCR denitrification

Research progress on MgO sorbents for CO_2 capture

Porous carbon structure control and its application in the field of carbon dioxide adsorption

Application status and prospects of coal chemical VOCs treatment technology

Research progress and prospect of coal chemical VOCs adsorption treatment technology

Study progress on the composition characteristics of fly ash from municipal solid waste incineration and treatment technology of heavy metal melting and solidification

Research progress on the effect of residual carbon in coal gasification slag on ash and slag flow property

Advances on dust removal technology of high temperature pyrolysis of coal gas containing dust and oil

Study on the X-ray recognition law of intelligent sorting by mineral components

Experimental study on co-degradation of polyacrylamide in coal slime water by mixed bacteria

Effect of non-ionic dispersant on the preparation of CWS from low rank coal

Study on hydrothermal upgrading of Zhundong coal and catalytic gasification characteristics of its derived liquid

Simulation study on chemical looping gasification of typical coal in Western China based on Aspen Plus

Diagnosis of the operation state of entrained flow coal water slurry gasifier burner based on qualitative trend analysis

CFD simulation of pseudo bubble-emulsion drag model in a large-scale high-temperature Fischer-Tropsch fluidized bed reactor

Effect of surface area on electrochemical performance of coal-based capacitive carbon

Numerical simulation study on the effect of air distribution on combustion of coal-fired boiler blended with sludge

Influence of characteristic elements in coal on ash formation characteristics of pulverized coal under high temperature oxy-fuel combustion

Thermal experimental study on co-combustion of pyrolysis semi-char and coal with different volatile content

Performance research on deep peak regulation with flue gas recirculation in a 330 MW subcritical CFB boiler

Effect of particle shape on the concentration measurement of particle mass with light extinction method

Study on the model for controlling arsenic emissions from blended coals combustion

Experimental study on kinetic characteristics of ACF electro-sorption process and influencing factors of desalination