Clean Coal Technology

2019年03期目次

Research progress of CO₂ capture with the assist Ca O-based energy storage materials at coal-fired power station
MA Zhangke;WU Shuimu;LI Yingjie;School of Energy and Power Engineering,Shandong University;SPIC Power Plant Operation Technology ( Beijing) Co.,Ltd.;
The greenhouse effect is aggravated by CO_2 generated by large-scale combustion of fossil fuels.Calcium cycle technology can not only achieve low-cost CO_2 capture,but also is one of the important methods of the thermochemical energy storage( TCES).In order to cope with the global warming problem,the renewable energy is large-scale developed and utilized,and the solar energy has broad prospects of large-scale industrial applications.However,the solar radiation is intermittent,the thermochemical energy storage technology emerges as the times require.The auxiliary CO_2 capture system of Ca O energy storage at coal-fired power stations and the high-temperature energy storage technology based on calcium cycle at solar thermal power stations were introduced. The influence factors including calcination conditions and particle sizes of materials on the cyclic energy storage performance of Ca O-based materials were analyzed.In addition,different methods of the improvement of the heat storage performance of Ca O-based materials were reviewed: the Ca O/Al_2O_3、Ca O/MgO、Ca O/SiO_2 composite energy storage materials are prepared by mechanical blending or chemical combustion synthesis.The results show that the Ca O energy storage system at coal-fired power station can improve power generation efficiency,reduce consumption of coal,and achieve emission reduction of CO_2.The energy storage density of Ca O/Ca CO_3 high temperature thermochemical system is as high as 3.2 GJ/m~3,which has high stability of energy storage cycle and can realize long-term energy storage without heat loss. The addition of inert carrier( Al_2O_3,MgO,SiO_2) can improve the activity and stability of Ca O heat cycle storage performance.The TCES based on carbonation/calcination reaction( calcium cycle) of Ca O-based materials at high temperature has great application prospects.In addition,the existing problems and research difficulties of Ca O-based energy storage materials were analyzed,and the research direction of energy storage was prospected. At present,the cycle activity of Ca O-based energy storage materials is reduced,and there is still a certain gap between the high-efficiency energy storage devices and practical applications. The preparation of the Ca O-based energy storage materials should be developed towards high energy storage density and high cycle activity.The improvement of overall power generation efficiency is the key to the optimization of energy storage systems.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 1600K]

Formation mechanism and research progress of fine mode particle matter during coal char combustion
LIU Siqi;NIU Yanqing;WEN Liping;YAN Bokang;WANG Denghui;HUI Shien;School of Energy and Power Engineering,Xi'an Jiaotong University;
In order to control the emission of particulate matter( PM) from coal combustion,it is necessary to have a thorough understanding of the emission rule and formation mechanism of PM. During pulverized coal combustion,PM can be divided into three formation modes: coarse mode,fine mode,and ultrafine mode.Compared to the coarse mode,the fine mode particles account for a larger proportion,and affect human health and atmospheric environment due to their small sizes and enrichment characteristics.Besides,the systemic summary of formation mechanism and research progress on fine mode PM are relatively lacking,compared with that of ultrafine mode,and it is difficult to suppress the emission of the fine mode PM.In this paper,the formation mechanisms of fine mode PM( char fragmentation,mineral melt coalescence,exterior mineral fragmentation and ash shedding) as well as the main influencefactors were analyzed.The research progress of simulationwere discussed and the research emphasis in future was pointed out.The particle size distribution of PM in coal ash turns out to be the result of competition between the char fragmentation and mineral aggregation. The fragmentations results in the increase of amount and the decrease of particle size of fine mode PM,while mineral aggregation leads to the amount decrease of PM,which is conducive to the formation of coarse mode PM.The main factors affecting the formation of PM arepore structure,combustion mode and char particle size.With relatively higher porosity,char cenospheres are more likely to broken up into more fine mode PM than other chars.Both increasing temperature,oxygen content and decreasing particle size are helpful to the formation of PM,but the aggregation of ash particles at higher temperature may lead to the particle size distribution towards coarse mode PM.The simulation of coke combustion characteristics by fragmentation behavior is mainly divided as population balance model and percolative fragmentation model. On the basis of the formation mechanism and influencing factors of fine mode PM,the percolative model is more suitable for simulating the char fragmentation,which takes the porous char structure into account.Therefore,the combination of kinetics combustion model and percolative fragmentation model is the key for the accurate prediction on the ash particle size distribution,which is the next research focus.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2607K]

Research progress on Fe-based oxygen carrier in chemical looping combustion
WEI Zehua;LIU Daocheng;JING Jieying;LI Wenying;Training Base of State Key Laboratory of Coal Science and Technology,Taiyuan University of Technology;
Chemical looping combustion is one of the most important technologies to deal with climate change in China.As the carrier of oxygen and heat,oxygen carrier is the key factor to realize chemical looping combustion.In recent years,how to develop cheap oxygen carriers has become a major concern.Due to its advantages of low cost,abundant resources,environmental friendliness and good mechanical properties,Fe-based oxygen carrier has attracted extensive attention,but its reactivity is relatively poor,and how to improve its reactivity is the key to its large-scale application. In this paper,the research progress on the improvement of the activity of Fe-based oxygen carrierin chemical looping combustion was reviewed.In order to improve the reactivity of Fe-based oxygen carrier,the optimization of preparation method,the doping of components and the structure regulation of Fe-based oxygen carrier were discussed.It is pointed out that the preparation method of oxygen carrier should be further improved by combing the factors such as the reaction performance,the preparation duration and cost of oxygen carrier.For the oxygen carrier components,the addition of the inert carrier,preparation of the composite oxygen carrier and alkali metal doping can improve the reactivity of the oxygen carrier to some extent.However,there are certain problems in the use of a single measure,such as the interaction of the active component with the inert carrier,the sintering of the composite oxygen carrier,and the loss of the alkali metal.Therefore,it is necessary to further study the interaction among various factors.For the oxygen carrier with different structures,it has good structural stability or thermal stability,but it also has its own disadvantages.For example,the oxygen carrier with perovskite structure has low oxygen storage capacity and oxygen release ability.The oxygen carrier with spinel structure may be deactivated by crystal phase separation and particle sintering during a long cycle.The oxygen carrier with core-shell structure,shell materials need to be further optimized so as to maintain its stability and reactivity in the cycle.Based on the current research status,it is pointed out that further improvement of the Fe-based oxygen carrier reactivity needs to comprehensively consider various factors and deeply explore the interaction between various factors.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 1133K]

Progress and research direction of dry deep screening technology of fine grained coal
ZHAO Huanshuai;Tangshan Landsky Technology Co.,Ltd.;Research Center for Engineering Technology of Fine Screen in Chinese Metallurgical Mines;
The dry deep screening technology of fine coal plays an important role in the coal industry and has become a hot and difficult study point in the field of screening.At present,the particle size limit of dry screening of fine-grained coal is mainly 6 mm and 3 mm,especially for 3 mm steam coal,which can be directly used for thermal power generation without separation.Therefore,the realization of 6 mm or3 mm fine grained dry screening method of raw coal can not only improve the utilization rate of coal,but also can save a lot of seperation cost.In this paper,the related theoretical research results of dry deep screening of fine coal were discussed,and the structure and performance characteristics of some typical dry deep screen equipments of fine grained coal were emphatically expounded.In addition,the research direction of the dry deep screening technology of fine grained coal was discussed in depth. At present,the related theoretical research achievements of the dry deep screen theory of fine grained coal abroad include probability screen principle,equal thickness screening theory,electromagnetic excitation theory,relaxation screen theory and strengthening screen theory. In this paper,the model of depth screen of adhesive fine-grained materials,the formula for calculating the adhesion force of moist fine-grained materials and the method of reducing adhesion force,the method of reducing the plugging of wet fine-grained materials and the technique of double plasmid resonance and mesh vibration screen were discussed.The domestic research mainly focuses on the practical probabilistic screening model,the reason for the accumulation of wet fine grained materials on the screen surface and the mechanism of adhesion and the influence factors of the adhesion force and adhesion thickness,and the design scheme of overcoming the phenomenon of wet fine grained raw coal deep screening blocking holes and sticky holes,the screening of difficult materials by means of vibration of sieve plate and non-vibration of sieve box,the mechanism of elastic screen surface overcoming blockage and comparison with the screening effect of rigid screen,and the distribution characteristics and distribution model of fine-grained coal,etc.The screening technology and equipment development are constantly innovated.Recently,the structures and performance characteristics of the developed screen equipments,such as probability screen,equal thickness screen,bo hou screen,high amplitude screen,arthropod screen,string screen,relaxation screen,ejection screen,resonant Taylor screen,double plasmid screen,electromagnetic high frequency fine screen and other dry deep screen equipments of fine coal,are different and suitable for different purposes.Based on the current development status of the dry deep screen technology of fine-grained coal,it is suggested that the deep research direction should be screen theory,key technology,screen structure optimization,optimization configuration of vibration parameters,related technology of screen plate and diversification research in the future.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 1099K]

Optimization of promoting effect of SDBS on low rank coal flotation utilizing based on response surface method
MA ChuANDong;LIU Jiayou;ZHANG Qingjian;CHI Yani;LI Lin;College of Chemical and Environmental Engineering,Shandong University of Science and Technology;School of Chemical Engineering & Technology,China University of Mining and Technology;Shandong Entry-Exit Inspection and Quarantine Bureau Inspection and Quarantine Technology Center;
In order to solve the problem that there are many oxygen-containing functional groups on the surface of low-rank coal and the separation effect of traditional flotation agents is poor,the low rank coal flotation experiment was carried out by using the anionic surfactant SDBS as flotation promoter.By single factor condition test,the suitable range of diesel oil and SDBS dosage were determined to be 6-9 kg/t and 800-1 500 g/t respectively,and the ratio of sec-octanol to diesel oil dosage was 1 ∶ 10-1 ∶ 5. On this basis,the response surface method was used to optimize the amount of diesel,sec-octyl alcohol and SDBS.The optimization test results show that there is an interaction among diesel,sec-octyl alcohol and SDBS,and the main effect relationship was as follows: SDBS>diesel>sec-octyl alcohols,and the second order regression equation with flotation perfect degree as the response values is obtained,which determines the best dosage of diesel,sec-octyl alcohols,SDBS to be 8. 57 kg,1. 28 kg/t,1 307 g/t,respectively.At this time,the theoretical value of the flotation perfect degree is 24. 16%.Under the condition of the optimal dosage of reagents,the flotation experiment was carried out. The obtained flotation perfect degree is 23. 98%,which is consistent with the theoretical value of the response surface methodvalue.The results show that the response surface method used to optimize agent system is accurate and feasible.The XPS wide-range scanning test results show that the oxygen-carbon ratio on the surface of low-rank coal is 1.40%.After adsorbing SDBS,diesel oil and diesel oil+SDBS,the oxygen-carbon ratio decrease to 1. 26%,1. 12% and 1. 01%,respectively.XPS C1 s analysis results show that the content of C—C/C—H group on the surface of low-rank coal is 66. 47%.After adsorbing SDBS,diesel oil and diesel oil+SDBS,the oxygen-carbon ratio increase to 72. 60%,75. 13%and 77. 12%,respectively.Before and after adsorption,the content of oxygen-containing functional groups on the surface of low-rank coal decreases significantly,the content of C—O group decreases from 16. 59% before adsorption to 15. 71%,14. 66% and 12. 71%,the content of C O group decreases from 10.09% to 7. 70%,4. 23% and 5.64%,and the content of O C—O group decreases from 6. 85% to3. 99%,5. 98% and 4.54%,respectively.The XPS test results show that the combined use of diesel and SDBS is better than that of diesel and SDBS alone.When SDBS as promoter,the content of C—C/C—H groups on the surface of low rank coal increases and the content of oxygen containing functional groups decreases,which indicates that the hydrogen bonding adsorption is the main physical adsorption of SDBS on the surface of low rank coal,the effective implementation of oxygen containing functional groups in low rank coal surface is realized,at the same time,C—C/C—H groups of SDBS expose on the surface of low rank coal enhance the hydrophobicity of low rank coal surface,which helps improve the flotability of low rank coal slime.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2647K]

Mechanism of rigid-flexible coupling elastic screening and 3 mm classification test of steam coal
PAN Miao;DUAN Chenlong;SHI Wei;ZHOU Zhiguo;JIANG Haishen;ZHAO Yuemin;China University of Mining and Technology;Jiangsu Hewa Screening product Co.,Ltd.;
Steam coal is widely used in electric power,metallurgy,building materials,chemical engineering and other fields.Screening is the key link of steam coal processing and utilization.With the development of coal mining mechanization,the content of fine particles gradually increases,when the moisture content of materials is high,it is easy to cause particles agglomeration,screening becomes difficult.Therefore,it is important to carry out efficient dry deep screening of viscous-moist steam coal.The traditional dry screening process mainly is classified by 6 mm,or even more than 13 mm,and the beneficiation proportion of raw coal is low,resulting in resources waste and environmental pollution.Reducing the lower limit of classification is a technical problem to be solved urgently at present. The traditional screen surfaces are rigid screen surface and elastic screen surface,the former is easy to cause aperture blockage,the latter is prone to local fever and aging during screening,greatly reducing the screening efficiency and the processing capacity of screen machine.In order to improve the efficiency of 3 mm dry screening of viscous-moist steam coal,the rigid-flexible coupling elastic screening method was proposed.The kinematics characteristics of rigid-flexible coupling elastic screen surface were studied by means of vibration test,motion behavior of sieve surface and the change rule of flexible region were clarified,and the mechanism of rigid-flexible coupling elastic screening was revealed.The influences of treatment capacity and external water content on 3 mm rigid-flexible coupling elastic screening process of steam coal were investigated by multi-factor successive terms test.The results show that the displacement amplitude and acceleration amplitude in elastic region increased by 87.69% and 98.08% respectively compared with that in rigid region; With the increase of treatment capacity,the comprehensive separation index increases first and then decreases,when the treatment capacity is 2.00 kg/s and the external water content of materials is 6.13%,the comprehensive separation index is above 89.00%.The increase of external water content leads to the decrease of comprehensive separation index,while the external water content rises to 11.01%,the comprehensive separation index is up to 78.92%,it is indicated that the rigid-flexible elastic screen surface can realize the high efficiency of 3 mm dry screening of viscous-moist steam coal.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2505K]

Enhanced removal of sulphur from coal by microwave combined with chemical auxiliaries
ZHOU Bingyi;ZHOU Tao;LI Yang;GE Tao;School of Materials Science and Engineering,Anhui University of Science & Technology;
Sulfur is the main harmful element in coal.The emission of sulfur during coal utilization is an important cause of acid rain.Desulfurization is one of the research hotspots for clean utilization of coal.Microwave has the function of promoting the reaction and accelerating the reaction rate.Microwave combined with chemical auxiliaries is an important means of coal desulfurization. In this paper,the effects of sulfur removal in coal were studied by microwave irradiation combined with three chemical additives.The effects of microwave irradiation time,chemical additives types and coal types on desulfurization were investigated by orthogonal test. The results show that the coal types have a great influence on the desulfurization efficiency of microwave assisted additives,and the optimum irradiation time of the selected three coal samples is different.Among the three chemical additives selected,the desulfurization effect of nitric acid combined with microwave is the best.The removal rate of total sulfur in Guizhou( GZ) coal can reach 71.2% under the action of microwave combining with nitric acid.The morphological sulfur test analysis shows that the removal efficiency of inorganic sulfur after coal desulfurization is higher,up to 90.5%,and the removal efficiency of organic sulfur is between 20% and 40%.XRD spectrum analysis shows that after the desulfurization of microwave assisting chemical additives,there is no significant change in the main minerals and coal structure in the coal.The microwaves can maintain the stability of coal matrix while removing sulfur from coal.Through the analysis of XPS spectrum,it is known that the removal of sulphur thioethers and organic sulphur from coal samples is better,the removal rate can reach 49.4%,the sulfoxides are slightly lower,the removal rate is 23%-28%,the removal of the thiophene organic sulfur is the worst,and the removal rate is between 10% and 20%.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2346K]

Pyrolysis characteristics of components with different density grades in Baishihu coal
ZHU Chuan;WU Linlin;Coal Chemistry Branch of China Coal Research Institute;State Key Laboratory of Coal Mining and Clean Utilization;
The serious fouling and slagging derived from direct combustion or gasification of high-alkali-coal limit the large-scale utilization of high-alkali-coal in Xinjiang area.The technology of coal grading pyrolysis does not have the conditions of high temperature and oxidizing atmosphere to trigger fouling and slagging problems,so it has broad application prospects.How to improve the yield and quality of oil and gas during coal pyrolysis is an important direction of research on the utilization of high alkali coal.With coal separation,the components of high oil yield can be concentrated and the adverse effects of alkali and alkaline earth metals( such as sodium and calcium) can also be reduced.In the paper,the vitrinite-rich coal in Baishihu with different density grades was separated by flotation and centrifugation with heavy organic liquid.Fourier infrared spectrum was used to characterize the surface functional groups of different density-level components.In addition,the thermogravimetric analyzer and Gray assay were used to study the change rule of pyrolysis characteristic parameters and dynamics parameters,and the distribution of pyrolysis products.The results show that for the components of Baishihu coal with different density grades,the hydrogen content and the H/C atomic ratio decrease first and then increase,while the oxygen content and O/C atomic ratio increase gradually.The functional groups of —OH are mainly carboxylic acid functional groups and phenolic hydroxyl groups,which are relatively enriched at the medium density fractions.With the increase of density level,the maximum pyrolysis rate and the rate of weight loss decrease gradually,and the activation energy and pre-exponential factors decrease first and then increase.The tar yield first decreases and then increases: the tar yield of BS_(<1. 3) is as high as 25.25% and BS_(>1. 6) is equivalent to that of BS_(1. 3-1. 4),about 15%.The vaporization of crystal water in clay minerals results in the highest moisture yield for BS_(>1. 6).
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2282K]

Study on the slagging characteristics of Xinjiang high-alkali coal in four-nozzle gasifier
KAWA Omarjiang;LIN Xiongchao;YANG Yuanping;LYU Junxin;ZHOU Mengyuan;YAO Gang;WANG Yonggang;School of Chemical and Environmental Engineering,China University of Mining & Technology( Beijing);Yankuang Xinjiang Coal Chemical Co.,Ltd.;
Aiming at the problem of slag plugging in gasifier caused by Xinjiang high alkali coal as gasification raw material,the slag produced in the actual operation of four-nozzle gasifier was taken as the research object and the physical and chemical characteristics of ash and slag were analyzed by means of scanning electron microscopy,X-ray electron spectroscopy( SEM-EDX),X-ray fluorescence spectroscopy( XRF) and ash melting point tester.In addition,the ash transformation behaviors of Beishan( BS) coal,Muchang( MC) coal and their mixture were examined in a high temperature furnace.The results show that the distribution of minerals in Xinjiang coal are heterogeneous.During the process of thermal transformation at high temperature,a series of complex physical and chemical reactions occur among minerals,which result in the diversity of mineral ash.When Xinjiang coal is used as gasification material,a large amount of ash accumulates at the slag mouth of the gasifier and form layered slagwhich is composed of silicate or alumina silicate eutectic of Na,Ca,Mg and Fe and Na-Al-Si-O.The contents of Na in the different forms of slags after coal gasification are quite different,which leads to different viscoustemperature characteristics and curing temperature of mineral slag.The thermodynamic simulation shows that the initial liquid phase forming temperature of Na-Si-O system is ca.800 ℃,and it varies slightly with the increase of Na_2O.Nevertheless,the liquid phase forming temperature rapidly increases to 1 050 ℃ when a certain amount of Al_2Si_2O_7 is mixed. The minerals melt to form complex eutectics at high temperatures with the decrease of temperature,the minerals in liquid ash with high molten point would form crystal nucleus,and then the crystal nucleus grows rapidly and precipitates out into crystalline particles.In the process of thermal transformation at high temperature,the active Na can react with quartz and clay minerals to form Na Al SiO_4 with low melting point.However,Ca,Mg and Fe react with acid minerals to form silica-aluminate minerals substances with high melting point,which are firstly precipitated from slag during the cooling process,resulting in slag blocking.The coal ash slagging propensity could be prevented by selecting or blending the coals with viscosity and melting temperature approaching to the gasification operation parameter.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 3031K]

Preparation and capacitance characteristics study of new coal-based microcrystalline carbon
BAO Ti'ao;WANG Zhenshuai;MA Ailing;XING Baolin;ZHANG Chuanxiang;HOU Lei;YUAN Shaohui;ZHAO Jing;GUO Mengyao;College of Chemistry and Chemical Engineering,Henan Polytechnic University;Henan College of Industry & Information Technology;
The supercapacitor has a wide range of applications.However,the traditional activated carbon can't fully meet the needs of the society in terms of energy density and electrical conductivity,which severely limits its application in large-scale energy storage devices.Therefore,it is of great significance to develop materials with higher energy storage performance.In this paper,a new coal-based microcrystalline carbon was prepared by preliminary carbonization coupled with KOH as activator process with abundant Taixi anthracite and used as electrode material for supercapacitor.The microstructure and pore structure parameter of the coal-based microcrystalline carbon was characterized by the methods of X-ray diffraction and low temperature N_2adsorption-desorption.The electrochemical performances of the corresponding electrode material were also investigated using galvanostatic charge/discharge,cyclic voltammetry and ac impedance.The results show that the coal-based microcrystalline carbon contains a large number of relatively complete graphite-like microcrystalline structure,and with the increase of alkali/carbon ratio,the graphite-like microcrystalline structure is gradually destroyed,and its layer spacing d_(002)gradually increases from 0.391 5 nm to 0.405 9 nm.The microcrystalline carbon with a specific surface area of 928 m~2/g,total pore volume of 0.527 cm~3/g and mesoporosity of 26.46%can be prepared at 800℃for 2 hours under the alkali/carbon ratio 4.The coal-based microcrystalline carbon applied as electrode materials for supercapacitor exhibits an excellent electrochemical performance in(C_2H_5)_4NBF_4/PC electrolyte.The specific capacitance of microcrystalline carbon is 94.8 F/g at a current density of 50 m A/g and the energy density reaches to 40.3 Wh/kg and at a current density of 500 m A/g,the initial specific capacitance is retained 87.3%after 1 000 cycles.It has good cycle stability and also shows smaller ionic diffusion resistance and internal impedance in the impedance curve.In the first charging process,the bend on charging curve means that the"electrical activation"phenomenon occurs.During this time,the electrolyte ions and solvent molecules around the microcrystalline carbon layerintercalate,making full use of the wafer space to store electrons to improve the energy density.The capacitance characteristics of coal-based microcrystalline carbon are mainly composed of intercalation capacitance and double-layer capacitance,among which intercalation capacitance caused by"electrical activation"is the main reason for the higher energy density of microcrystalline carbon.The superior electrochemical performance of the new coal-based microcrystalline carbons is strongly related to the microcrystalline structure and abundant pore structure.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2058K]

Effect of air grading technology on NO_x formation of coal gas combustion in a calciner
YANG Xiehe;CAI Runxia;ZHANG Yang;ZHANG Jiansheng;ZHANG Hai;LYU Junfu;Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,Tsinghua University;
Coal gas produced from coal gasification,is frequently used as a fuel in the aluminium hydroxide calcination process.Normally,coal gas generally contains a certain amount of ammonia,resulting in a high amount of nitrogen oxides in the roasting process.In this paper,the low-nitrogen combustion process of gas was studied by air classification method in a gas-fired aluminum hydroxide suspended calciner,and the influence of air classification technology on the formation of nitrogen oxides in gas combustion in the calciner was investigated,so as to guide the actual combustion structure design and optimization in the calciner.Barracuda~(TM)software was utilized to simulate the gas-solid two-phase flow and the combustion process in a 3 000 t/h Al_2O_3calciner.The results show that there is an obvious high temperature zone at the bottom of the suspension calciner.The local high temperature load point is concentrated,and the maximum temperature is up to1 700 K.With the increase of furnace height,the mean temperature decreases gradually.Additionally,due to the effect of airflow reflux,there is a high concentration area of particles in the bottom of the furnace and the upper airflow diversion.Based on the temperature field in the furnace calculated by gas-solid flow,and the detail chemical reaction process was considered by coupling the detailed chemical reaction mechanism.The reactor network was established by using Chemkin Pro software,and the influence of air classification technology on the formation of NO_xin the combustion process of ammonia-containing gas in the calciner was investigated by numerical calculation.The results show that the main nitrogen oxides produced in the calciner burning gas are fuel nitrogen oxides.In addition,the inhibition effect of air classification on the formation of NO_xin gas combustion is limited when the staged-air ratio is 20%.However,the NO_xemission generated by gas combustion in calciner reduced up to 70.3%when the staged-air ratio is 40%,and the reducing atmosphere appears in the main combustion area.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 1554K]

Numerical simulation of synergistic optimization of un-burned carbon and NO_x of blended coal under deep air staging condition
YAN Zhuming;MA Lun;YE Ji;ZHANG Cheng;TAN Peng;FANG Qingyan;CHEN Gang;Guangdong Red Bay Power Generation Co.,Ltd.;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
In order to explore the influence of mixing mode and air distribution mode on burnout rate and NO_xemission of blended coal,a660 MW tangential fired boiler was taken as the research object,numerical simulations were carried out to study the synergistic optimization of un-burned carbon and NO_xformation in the combustion process of blended coal.The results show that under the condition of deep air staging,the un-burned carbon is mainly affected by many factors such as coal particle residence time,coal blending methodand air distribution method and other factors.Synergistic optimization of un-burned carbon and NO_xemissions can be achieved by a combination of reasonable blending method and air distribution method.Compared with the blending method outside the furnace,the in-furnace blending method is more flexible,and the low-volatile coal combustion can be optimized and adjusted to lower the un-burned carbon level of blended coal.Under the in-furnace blending method,the low volatile coal is placed near the upper burner under uniform air distribution or the low volatile coal is placed in the lower burner near the lower burner under"Zhengbaota"air distribution,which are both conducive to the burnout of low volatile coal,while setting high-volatile coal near the upper burner is more conducive to the reduction of NO_xemission.Considering the characteristics of the unburned carbon and NO_xemission of blended coal,the burnout level of the low-volatile coal is increased and the un-burned carbon level of blended coal is decreased by setting high-volatile coal near the upper burner and adopting the"Zhengbaota"air distribution which can provide relatively sufficient oxygen for the combustion of low volatile coal in the lower part.Meanwhile,the volatile from the high-volatile coal near the upper burner contains a large amount of intermediate HCN,which can restore the generated NO_xand is benefit to reduce NO_xformation of blended coal in the furnace.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 4005K]

Experimental investigation on radiative entropy generation and radiative exergy in a large coal-fired boiler
LI Zhi;ZHANG Zhongnong;LOU Chun;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
In order to study the efficiency of radiative heat transfer in the coal-fired furnace,and achieve the aim of saving energy and reducing pollutant emissions,this paper presented an experimental measurement method for radiation entropy generation and radiation exergy in large-scale furnaces.The method was applied in a 670 t/h coal-fired boiler of a 200 MW generator unit.The radiative images in the furnace were captured by CCD cameras installed on the boiler.The temperature distributions and radiative properties in three sections of the furnace were reconstructed by the solution of inverse radiation problem.And then,experimental results of radiative entropy generation,dimensionless radiative entropy generation,and radiative exergy of pulverized coal combustion medium and water cooling wall in the furnace were obtained.The effects of standard deviation of temperature distribution in furnace and radiative heat flux of wall on radiative entropy generation and radiative exergy were analyzed.The results show that with the increase of standard deviation of temperature distribution in coal-fired boilers,the irreversibility of absorption,emission and scattering process of pulverized coal combustion medium increase gradually,and the radiation heat transfer efficiency decreases gradually,and generated by combustion medium,the radiative entropy generation increases from 419 W/K to 629 W/K and the dimensionless radiative entropy generation increases from 0.048 to 0.067.With the increase of heat flow on water-cooled wall,the irreversibility of radiation heat transfer process on water-cooled wall increases gradually,and the radiative heat transfer efficiency decreases gradually,so the radiative entropy generation generated by the water cooling wall increases from1. 566 k W/K to 4. 575 k W/K and the dimensionless radiative entropy generation increases from 0.258 to 0.346.In the burner area of the furnace,due to the relatively highest combustion temperature,the radiation heat exchange process is the most intense,leading to the most available work,so the radiative exergy is the largest.In the furnace exit area where the temperature is relatively lowest,the radiation heat transfer process is relatively weakest,and the available work is relatively least,so the radiation exergy is relatively minimal.It can be seen that for the practical furnace,improving the uniformity of the temperature field in the furnace,especially increasing the uniformity of the temperature field in the furnace burner region,is of great significance for improving the radiation heat transfer efficiency of the coal-fired furnace.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 1793K]

Effect of loop seal structure of circulating fluidized bed on the dynamic response characteristics of circulating flow rate
LIU XiANDong;ZHANG Yang;YANG Hairui;ZHANG Man;ZHANG Hai;LYU Junfu;Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,Tsinghua Unversity;
The boiler combustion technology of circulating fluidized bed( CFB) is a kind of clean coal combustion technology,and its flexibility to cope with load change will attract more attention in the future.Recent studies about load change are focused on the optimization of peak shaving,which lack the research of influence factors on CFB boiler itself.The circulation rate will change and reach a new equilibrium state as load of CFB boiler changes.The structure of loop seal is an important factor on the circulation state.Therefore,in order to investigate the influence factors on CFB boiler response rate to load change,the flow behavior of a 75 t/h in standpipe and loop seal of a CFB boiler with circulating rate change was simulated based on CPFD method.The dynamic response rate to circulating flow rate change under different loop seal structure was studied.The results indicate that there are some"flow-dead zone"on the away-recycle-valve side of the standpipe and the bottom of the loop seal.The gas-solid flow in that zones have relatively high moving velocity only in restricted areas,so the moving area of small particle limits the time to reach a higher flux equilibrium state when the circulation rate increases.The flow-dead zone decreases the response rate to the load change.When the loosening air and fluidizing air are 0.14,0.3 m/s respectively and the circulating flow rate increases from 50 kg/( m~2·s) to 60 kg/( m~2·s),the system response time decreases sharply first and then increases moderately with the increase of horizontal section length.The shortest response time is 67 s,when the ratio of loop seal horizontal section length to the standpipe diameter is 3.5.Keeping the fluidizing air and adjusting the loosening air,the system response time decreases with the increase of loosening air while the relation between system response time and the loop seal structure keeps similar.The response rate of loop seal to circulating flow rate change is closely related to the size of flow-dead zone in the loop seal.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2025K]

Se partitioning and species in WFGD and WESP system of the ultra-low emission coal fired power plant
YU Xuehai;ZHANG Yi;CHANG Lin;GU Yongzheng;LI Zenghua;ZHANG Shuai;CUI Xiangzheng;CHEN Yinbiao;ZHAO Yongchun;Shenhua Guohua( Beijing) Eletric Power Research Institute Co.,Ltd.;School of Energy and Power Engineering,Huazhong University of Science and Technology;Guohua Electric Power Branch,China Shenhua Energy Co.,Ltd.;
Se is released to gas phase and combines with fine particles in flue gas after coal combustion which can be captured by the wet desulfurization( WFGD) system and wet electrostatic precipitator( WESP) in flue gas,and it is important to determine the partitioning and species of Se in these systems.Based on hydride generation-atomic fluorescence spectrometry( HG-AFS),the partitioning and species of Se in the key locations of WFGD and WESP were studied.It is found that Se can be removed by WFGD system in flue gas.The concentration of Se in the solid fraction and liquid fraction of desulfurization tower slurry are 1.07 μg/g and 0.123 mg/L,respectively.Over 80% Se in the desulfurization tower is oxidized to Se( VI) under forced oxidation condition.After separated by a hydrocyclone,most Se is transported to effluent treatment process.The predominant Se species in the effluent treatment process is Se( VI),with the proportion exceeds 77%,which accounts for low efficiency in Se removal by traditional three-linked tank technique. Se exhibits a significant enrichment in solid fraction of the flush water from WESP whose concentration is 13.9 μg/g,while 0.001 6 mg/L Se is determined in the liquid fraction where proportions of Se( IV) and Se( VI) are 34.35% and 65.65%,respectively.WESP equipment achieves Se deep removal from flue gas,and transports this part of Se to the solid fraction of ash.It is calculated that with the help of WESP 2.9 kg/yr particle-bound Se is removed.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2050K]

Experimental study on ultra-low emission of nitrogen oxide using ozone oxidation in 220 t/h coal-fired boiler
ZHANG Libo;LIU Peixi;ZHANG Ye;XU Chaoqun;SHAO Jiaming;HE Yong;WANG Zhihua;China Huadian Power Group Harbin Power Generation Co.,Ltd.;State Key Laboratory of Clean Energy Utilization,Zhejiang University;Jilin Zheda Energy Clean Utilization Technology Co.,Ltd.;
In recent years,the requirement of environmental protection has become more and more stringent,and the task of energy saving and emission reduction in coal-fired power industry has become more and more arduous.The transformation of ultra-low emission of coalfired power plants is imminent.In this paper,three 220 t/h pulverized coal fired boilers were revamped with ozone denitration technology,and a series of debugging tests were carried out.With the help of flue gas analyzer and on-line detection system of power plant,the effects of O_3/NO molar ratio and initial concentration of NO_xon denitration effect were mainly explored.The experimental results show that the application of ozone denitration technology in the pulverized coal boiler has a very good denitration effect,and the removal efficiency of NO_x reaches more than 90%.The NO_x concentration at the outlet of the boiler fluctuates greatly with the boiler load.The boiler load increases and the NO_xconcentration at the outlet increases.If the boiler load decreases,the NO_xconcentration at the outlet also decreases,showing a positive correlation.The efficiency of ozone denitration increases with the increase of the molar ratio of O_3/NO and ozone dosage,but when the molar ratio of O_3/NO exceeds a certain value,the rate of ozone denitration increases slowly with the increase of ozone dosage.In ozone denitration technology,the denitration efficiency is less affected by the initial concentration of NO_x.When the molar ratio of O_3/NO reaches a certain value,the denitration efficiency can be guaranteed under different conditions of the initial concentration fluctuation of NO_x.The characteristic curve obtained in this experiment provides a basis for determining the optimum ozone injection quantity in the application of ozone denitration technology,that is,how to select the optimum O_3/NO ratio on the premise of ensuring the denitration efficiency.After the application of ozone denitration technology,the power plant passed 168 hours of test successfully.The concentration of NO_xin flue gas emission is stable below 50 mg/Nm~3,which meets the national ultra-low emission requirements.It can be seen that the use of ozone denitration technology to control the emission of NO_xin flue gas has a very good effect.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 1424K]

Research on SNCR/flue gas recycling synergistic denitration technology
LEI Yu;LIU Yang;NIU Yanqing;HUI Shien;State Key Laboratory of Multiphase Flow in Power Engineering,School of Energy and Power Engineering,Xi'an Jiaotong University;Xi'an Thermal Power Research Institute Co.,Ltd.;
In the short term,the status quo of coal as the main energy in China will not change.Because coal combustion will release a lot of NO_xand cause serious environmental pollution,so the control of NO_xin coal combustion process is very important.Chain grate furnace as one of the most widely used coal-fired boilers in China must be paid more attention to the reduction of NO_xemission.Especially with the implementation of Boiler Air Pollutant Emission Standard(GB 13271—2014),the NO_xemission value of grate furnace in key areas should not be higher than 200 mg/m~3,the technology of low-nitrogen combustion and NO_xremoval in chain grate furnace has attracted wide attention.In order to reduce the NO_xemission of chain grate furnace,meet the requirements of national environmental protection,reduce the cost of operation and maintenance of enterprises and improve the economic benefits of enterprises,the technical improvement study of flue gas recirculation and SNCR denitrification system was performed in a 4×75 t/h chain grate furnace of a heating station at Gaoxin District in Xi'an to reduce the NO_xemission.The influence of the parameters of SNCR and flue gas recirculation coupled low nitrogen combustion system,such as flue gas recirculation ratio,the feed ratio of recirculation flue gas in primary and second air chamber,the ammonia nitrogen molar ratio and the change of boiler load on NO_xremoval efficiency and combustion characteristics were researched.The optimum operating parameters of flue gas recirculation coupled with SNCR technology were determined.The results show that the SNCR coupled flue gas recirculation low nitrogen combustion technology can effectively reduce the NO_xemission of chain grate furnace.When the flue gas recirculation rate is 16%-18%,the feed ratio of recirculation flue gas in primary air chamber is 82%,and the molar ratio of ammonia nitrogen is 0.78,the SNCR coupled flue gas can achieve the best denitrification efficiency in the circulating system.At this point,the denitration efficiency of SNCR coupling flue gas recycling is up to 56%and the denitrification efficiency of SNCR single operation is 40%and the actual NO_xemission is reduced from 250 mg/m~3to 110 mg/m~3,which is much higher than the national emission standard of NO_x.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 1516K]

Investigation on the occurrence morphology and quantitative analysis of amorphous silicon in coal fly ash
ZHANG Jianbo;LI Zhanbing;YANG Chennian;LI Shaopeng;LI Huiquan;CAS Key Laboratory of Green Process and Engineering,Institute of Process Engineering,Chinese Academy of Science;National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology;Chinese Academy of Sciences;
Coal fly ash is regarded as the important solid waste in the large coal power base,and above 600 million tons coal fly ash is generated annually.The utilization ratio is only 60%approximately,the most of fly ash is mainly stored in piles,which can cause serious environmental problems,and its resource utilization is of great significance.In this paper,the high alumina coal fly ash(HAFA)generated in Shanxi and the north of Inner Mongolia was adopted and researched.The basic physical property analysis shows that aluminum,silicon,iron,calcium are the main elements in the coal fly ash,which are in the form of mullite,amorphous silica and ferruginous spheres.Mullite is a stable phase.The reactivity of amorphous phase aluminum silicate is high,but its coordination structure is complex and the reactivity is different.Nowadays,in terms of its abundant aluminum/silicon resources,the main high-value research directions focus on the extraction of alumina and preparation of aluminum-siliconcomposite,in which the removal of amorphous silica is the key processing technology.In view of the occurrence morphology and quantitative analysis of amorphous silicon,firstly,the NMR analysis combined with EPMA was used to determine the complex structure of aluminium-silicate in amorphous phase.The silicon atoms mainly exist in five coordination structures:Q~4(4Al)/Q~4(3Al)/Q~4(2Al)/Q~4(0Al)/Q~2(1Al),and the content of Q~4(0Al)is occupied about 56.5%in the amorphous phase.Secondly,by means of acid-base combination method,the possibility of spontaneous reaction in alumina-silica zeolite was gradually weakened,active aluminium was selectively separated,and the active sites were exposed in large quantities,so as to realize the step-by-step separation of amorphous aluminium-silicate.Further,the efficient separation between mullite crystalline phase and aluminium-silicate amorphous phase was identified by ICP,XRF,XRD,SEM and EPMA.Two groups of parallel experiments were carried out,and the error of the test results was small.The results indicate that the content of silicon in amorphous phase is 57%-58%.The"bulging peak"of amorphous silica has disappeared,the grain structure of mullite enwrapped by the amorphous silica is exposed,which proves that amorphous silicon dioxide can be removed efficiently.There are three advantages of mild experimental conditions,minor errorand wide operating flexibility,which provides an important guiding significance for high value conversion and utilization of fly ash aluminium-silicon resources.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2606K]

Treatment of the secondary biochemical effluent from coking wastewater by different advanced oxidation processes
HE Can;CHEN Zhuomiao;LI Yi'nan;WU Zhaoyu;HUANG Guowei;WANG Can;WANG Jianbing;School of Chemical and Environmental Engineering,China University of Mining and Technology( Beijing);
The COD of the effluent from the secondary biological treatment process of coking wastewater couldn't meet the standard.In order to resolve the problem,the effects of advanced treatment of coking wastewater by single ozonation,O_3/H_2O_2oxidation and UV-Fenton processes respectively,were investigated through laboratory test,which were carried out in semi-continuous mode.The quality of effluent from the different processes were analyzed,where UV_(254),BOD_5/COD,the luminescent bacteria toxicity,three-dimensional fluorescence spectrum were evaluated.The influence of different advanced oxidation processes on effluent quality was explored.The results show that the increase of ozone dosage and addition of H_2O_2can significantly enhance the removal of organic compounds in the secondary biochemical effluent from coking wastewater.When the COD of the influent is(200±10)mg/L,the average COD removal rate for 120 min reaction in single ozonation process is 36%with the ozone dosage of 30 mg/L.When the COD of the influent is(200±10)mg/L,the average COD remov-al rate for 120 min reaction in UV-Fenton process is 50%with the H_2O_2dosage of 2 g/L and the molar ratio of Fe~(2+)and H_2O_2of 1∶10.When the COD of the influent is(200±10)mg/L,the average COD removal rate for 120 min reaction in O_3/H_2O_2oxidation process is63%with the ozone dosage of 30 mg/L and H_2O_2dosage of 2 g/L,which meets the Emission Standard of Pollutants for Coking Chemical Industry,China(GB 16171—2012).Among the three processes,the O_3/H_2O_2oxidation process is the most effective for organic compounds removal.This is mainly attributed to the synergistic production of strong oxidizing radicals by O_3and H_2O_2.However,when the concentration of H_2O_2is too high,·OH produced in the system reacts with H_2O_2instead,resulting in the decline of oxidation capacity of O_3/H_2O_2system.All the three processes can reduce its toxicity.The results of acute toxicity test of with luminescent bacteria shows that the relative luminosity of effluent after single ozonation and O_3/H_2O_2oxidation for 15 min increaseto 90%and 87%,respectively.After UV-Fenton oxidation for 30 min,the relative luminescence of effluent increases to 71.57%.Compared with single ozonation and O_3/H_2O_2oxidation process,the effluent of UV-Fenton treatment has relatively higher acute toxicity,which may be related to the disinfection effect of ozone.The three processes can hardly improve its biodegradability,while BOD_5/COD only increases from 0.02 to about 0.1.The comparative analysis of UV_(254)and EEM(Excitation-emission Matrix)show that the three processes have obvious decomposition effect on aromatic compounds and fluorescent substances in the secondary biochemical effluent.The conjugated double-bond substances of humic acid-like substances in wastewater can be preferentially degraded in single ozonation process,while O_3/H_2O_2oxidation process has more significant oxidation effect on cyclic conjugated pollutants.In the UV-Fenton process,humic acid-like substances and UV-fulvic acid-like in coking wastewater are oxidized preferentially,and eventually converted into visible fulvic acid-like and protein-like,which still have relatively high concentration in the effluent.Among the three oxidation processes,the removal of fluorescent substances by UV-Fenton oxidation process is the worst.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2507K]

Effect of saline wastewater of coal chemical industry on the sedimentation characteristics of coal slurry
HUANG Gen;GUO Xuan;School of Chemical and Environmental Engineering,China University of Mining and Technology( Beijing);
The saline wastewater of coal chemical industry contains a large amount of inorganic salt ions.For saline wastewater,the discharge will cause environmental pollution,while the treatment and recovery cost is relatively high.In this paper,saline wastewater of coal chemical industry was used as a coagulant for coal slurry as the inorganic salt ions in the saline wastewater were similar to the effective ionic components of the coagulant.The influence of saline dosage on the sedimentation characteristics of coal slurry was discussed with non-stick coal sample from Inner Mongolia.The stability of coal slurry was analyzed by a turbiscan lab.The changes of the coal particle size were measured by a laser particle size analyzer.The effects of saline dosage on the sedimentation effect and supernatant turbidity were studied with polyacrylamide as a flocculant.The results show that the coal slurry system is relatively stable when no saline wastewater is added and the turbiscan ability index(TSI)has no obvious change.With the increase of saline dosage at 0-62.5 kg/t,the coal particles begin to agglomerate,and the TSI value increases significantly.The TSI at the top area of the coal slurry reaches a maximum value when saline dosage is 50.0 kg/t,then the TSI value begins to decrease when saline dosage is further added.Simultaneously,the zeta potential of the coal slime surface increases rapidly and then tends to be steady with the increase of saline dosage,indicating that the cations in the saline have an effect on compressing electric double layer and reducing the surface potential.The results of particle size analysis show that the D_(50)and D_(90)of the coal slime particles is 9.43μm and 45.57μm separately without adding saline wastewater.And these two values increase to 11.92μm and 63.77μm,separately,when 12.5 kg/t saline dosage is added,demonstrating that the addition of saline wastewater promot the coagulation among particles.The results of slurry water sedimentation test are basically consistent with TSI,and the settling rate of the coal slurry gradually accelerates with the increase of saline dosage.When the saline dosage is 50 kg/t,the settling rate reaches the maximum value and the supernatant turbidity reaches the minimum value.The results show that the saline wastewater can effectively promote the coagulation of coal slime particles and improve the sedimentation effect of difficult-to-settle slurry water.Therefore,saline wastewater from coal chemical industry can be considered to use as a coagulant for coal slurry in order to reduce the treatment cost of saline wastewater and improve the sedimentation effect of coal slurry.However,the influences of saline wastewater on the separation index,product performance and equipment life in the whole coal preparation process system need further study.
2019 03 v.25;No.121 [Abstract][OnlineView][HTML全文][Download 2007K]

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2019年03期目次

Research progress of CO₂ capture with the assist Ca O-based energy storage materials at coal-fired power station

Formation mechanism and research progress of fine mode particle matter during coal char combustion

Research progress on Fe-based oxygen carrier in chemical looping combustion

Progress and research direction of dry deep screening technology of fine grained coal

Optimization of promoting effect of SDBS on low rank coal flotation utilizing based on response surface method

Mechanism of rigid-flexible coupling elastic screening and 3 mm classification test of steam coal

Enhanced removal of sulphur from coal by microwave combined with chemical auxiliaries

Pyrolysis characteristics of components with different density grades in Baishihu coal

Study on the slagging characteristics of Xinjiang high-alkali coal in four-nozzle gasifier

Preparation and capacitance characteristics study of new coal-based microcrystalline carbon

Effect of air grading technology on NO_x formation of coal gas combustion in a calciner

Numerical simulation of synergistic optimization of un-burned carbon and NO_x of blended coal under deep air staging condition

Experimental investigation on radiative entropy generation and radiative exergy in a large coal-fired boiler

Effect of loop seal structure of circulating fluidized bed on the dynamic response characteristics of circulating flow rate

Se partitioning and species in WFGD and WESP system of the ultra-low emission coal fired power plant

Experimental study on ultra-low emission of nitrogen oxide using ozone oxidation in 220 t/h coal-fired boiler

Research on SNCR/flue gas recycling synergistic denitration technology

Investigation on the occurrence morphology and quantitative analysis of amorphous silicon in coal fly ash

Treatment of the secondary biochemical effluent from coking wastewater by different advanced oxidation processes

Effect of saline wastewater of coal chemical industry on the sedimentation characteristics of coal slurry