Clean Coal Technology

2020年04期目次

Research progress on chemical-looping combustion and pollutant release for solid fuels
HU Donghai;HUANG Jiejie;Li Chunyu;YU Zhongliang;KANG Sile;ZHANG Jianli;WANG Zhiqing;DU Meijie;Fang Yitian;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences;Graduate University of Chinese Academy of Sciences;Tongmei Guangfa Chemical Industry Co.,Ltd.;State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University;
Chemical-looping combustion( CLC) has become a promising solid fuel combustion technology due to its inherent advantages of high concentration of CO_2,easy separation and low cost of CO_2 reduction. At present,CLC technology includes in-situ gasification CLC( i G-CLC) and oxygen uncoupling( CLOU) of solid fuel chemical-looping combustion.When solid fuel is used for combustion,the pollution elements will be released into the atmosphere or doped into the target gas of CO_2 in the form of gas,which will bring environmental and operational problems.In this paper,two technologies and related principles of i G-CLC and CLOU for chemical looping combustion of solid fuel were introduced,the research status at home and abroad was briefly described,and the properties,advantages and disadvantages of the two technologies were analyzed.At the same time,the pollution elements and their release rules in the process of solid fuel chemical chain combustion were summarized and analyzed.Most of the S elements in the solid fuel will eventually be transferred to the gas phase and released in the form of H2 S and SO_2( i G-CLC) or single SO_2( CLOU),a small portion of which will be fixed in the ashes or combined with the oxygen carrier.In terms of emission ratio,with the increase of fuel reactor temperature,the content of sulfur gas at the outlet of fuel reactor increases,while the content of sulfur gas at the source of air reactor decreases.For the solid fuel,all the N elements will be transferred to the gas phase and released in the form of N2 and NO in both technologies.The difference is that in CLOU technology,the formation of NO is more due to the oxygen release of oxygen carrier.At the same time,the change of nitrogen content and temperature at the outlet of fuel reactor and air reactor is consistent with that of S.The Hg elements in the solid fuel will be mainly presented in the gas in the form of Hg0 and Hg2+,and mainly in the form of Hg0 in the fuel reactor,and in the form of Hg2+in the air reactor,and a considerable part of the Hg( 42.5%) in the CLOU technology will be retained in the combustion ash.The release of Hg in the fuel reactor will increase with the increase of the temperature of the fuel reactor,and the release of Hg in the air reactor will decrease.The volatile matter in the chemical chain combustion process of solid fuel,as a pollutant,also needs to be paid attention to in the aspect of emission.The results show that the type of fuel seems to have a decisive effect on the amount of tar in the outlet gas of the fuel reactor.At present,tar emission is only found in the i G-CLC of biomass with high volatile content,while in CLOU technology,the tar compounds are completely burned due to the presence of gaseous oxygen in the fuel reactor.Finally,combined with the properties of pollution elements and the release law in the two chemical chain combustion technologies,some suggestions are put forward for the process development and design by the raw material treatment and process improvement to reduce the emission of pollutants.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 4113K]

Present situation and development of zero-discharge technology for desulfurization wastewater in coal-fired power plants
LYU Wuxue;YU Yanfei;QU Baozhong;CHEN Jianing;CUI Lingxiao;MA Shuangchen;Huaneng Weihai Power Co.,Ltd.;Department of Environmental Science and Engineering,North China Electric Power University;University of Illinois at Urbana-Champaign;
Desulfurization wastewater from coal-fired power plant has problems such as poor water quality,large water volume,and high treatment cost.The wastewater treatment technology is also constantly updated.The water quality and quantity of desulfurization wastewater of different power plants are also greatly different,and there are also big differences in the choice of treatment technology.In order to choose the desulfurization wastewater treatment technology more scientifically and effectively,the current desulfurization wastewater treatment technology of coal-fired power plants was summarized and analyzed,and the advantages and disadvantages of various treatment technologies were analyzed in detail according to the actual case.It provides a reference for coal-fired power plants to choose the zero-discharge technology of desulfurization wastewater. The research results show that the current zero-emission treatment technology for desulfurization wastewater of coal-fired power plants mainly includes: pretreatment technology for desulfurization wastewater,concentration and reduction technology,evaporative crystallization technology and transfer solidification technology,and the zero-emission treatment technologies of various wastewater are uneven.The triple tank method and double-alkali method in the pretreatment technology were analyzed in detail.According to the characteristics of the wastewater,the pretreatment link can be omitted,which can be omitted to reduce the investment cost.Concentration reduction technology includes membrane concentration( RO,FO,ED,etc.) and thermal concentration( using steam concentration,flue gas waste heat concentration).Membrane concentration can achieve a higher concentration ratio and system stability,but its higher investment and operating cost needs to be resolved.Thermal concentration has gradually become the mainstream concentration technology due to its low cost and high efficiency. The evaporative crystallization technology uses flue gas waste heat evaporation( bypass flue gasification,flue gasification),and the problems of corrosion and scaling in its operation need to be resolved.The cementing and fixing technology in the transfer and solidification technology not only can fix the high concentration of chloride ions in the desulfurization wastewater,but also have a good fixing effect on various heavy metal ions in the wastewater.The technology points out the place of the terminal high concentration brine produced by the treatment,and the solidified body can be reused.High concentration chloride ion can also be used to prepare water purifying agent to realize the secondary utilization of wastewater.At the same time,four principles for the selection of desulfurization wastewater treatment technology were proposed.The low-cost,low-risk and high-efficiency desulfurization wastewater zero-discharge process route is more in line with the current needs of enterprises.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 3646K]

Research progress of activated coke flue gas purification reactor
ZHANG Yunlei;SUN Zhongchao;LIANG Daming;XIONG Yinwu;LI Yanfang;Coal Chemistry Branch of China Coal Research Institute;Beijing Key Laboratory of Coal Based Carbon Materials;State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources;
Activated coke dry method flue gas purification technology has the advantages of low water consumption,no secondary pollution and recyclable use of adsorbent,and has broad development prospect.As the core of the process,the research of reactor has become the key to restrict the development of this technology.The flue gas emission characteristics and the pollutant emission limits of different industries are different.Accurately selecting the reactor type and optimizing the reactor structure according to the flue gas characteristics is an effective means to improve the system flue gas purification efficiency.In this paper,the advantages and disadvantages of various types of reactors currently used in the field of activated coke flue gas purification and its scope of application were introduced,the effects of different types of internal components on the gas-solid two-phase motion state in the reactor were discussed,and the future research direction of activated coke and the optimization of flue gas purification reactor were finally proposed.In terms of reactor bed type,the technical advantages and shortcomings of three types of reactors,including fixed bed reactors,moving bed reactors and fluidized bed reactors,were summarized.Among them,the structure of fixed-bed reactor is simple and usually used in the active coke desulfurization process. When the flue gas treatment volume is small,the flexibility is strong.As the flue gas treatment volume increases,its purification effect decreases and multiple reactors are required to operate in parallel,which has large area,high input cost; fluidized bed reactor has the advantages of large gas-solid flux,high automation,excellent mass and heat transfer performance,but it is not suitable for granular active coke due to strong internal particle wear,and has good applicability for powdery activity coke; the moving bed reactor is currently the most widely used in the field of active coke flue gas purification,with the advantages of strong continuity,large flue gas treatment capacity,and low requirements for particle mechanical strength,but its internal structure is complex,and materials are prone to abnormal flow.With regard to the internal components of the reactor,the effects of flue gas guide components,ammonia injection mixing components,and discharge components on the system's flue gas purification efficiency were discussed.In view of the turbulent gas flow in the reactor,the uniformity of flue gas in the reactor can be improved by adding a deflector or a rectifying layer; in order to improve the uniformity of ammonia injection,ammonia injection components can be provided in the ammonia injection area to improve the denitrification efficiency of the system,the more common ammonia injection components include static mixers,ammonia injection grids,and vortex components.Among them,static mixer is precisely controlled,but the cost is high and the processing capacity is limited.The ammonia injection grid can achieve zone control but is easy to appear the problem of pipeline clogging.The cost of vortex component reconstruction is low,but the control flexibility is poor.In industrial production,it is necessary to flexibly select ammonia injection components according to the amount of ammonia injection and flue gas emission indicators; in order to prevent solid materials from appearing " funnel flow" and other abnormal flows during the movement of the reactor,a discharge member can be added inside the reactor,which can effectively improve the flow state of solid materials in the reactor.After adding internal components,the gas-solid contact in the reactor is enhanced,the system purification efficiency is significantly improved,and the cost of transformation is reduced.Finally,it was clarified that the future activated coke flue gas purification reactor will be developed in the direction of innovative reactor bed type,enhancing industry matching,optimizing reactor structure,and reducing operation and maintenance costs.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 6625K]

Comprehensiveutilization situation of fly ash in coal-fired power plants and its development suggestions
JIANG Long;North China Electric Power Research Institute Co.,Ltd.;
Coal is the main energy source of electric power in China.600 million tons of fly ash is produced in hte coal-fired power plant of China produces every year,accounting for half of the world's total output of fly ash.The comprehensive utilization rate of fly ash in China is only 70%.In order to fully understand the comprehensive utilization of fly ash in China and improve the comprehensive utilization of fly ash in China,the main utilization situation,relevant standards,relevant laws and policies,and main utilization ways of fly ash at home and abroad were introduced.By comparing the utilization status at home and abroad,the rationalization suggestions of comprehensive utilization of fly ash in China in the future were put forward from three aspects: utilization ways,standard formulation,laws and regulations.The comprehensive utilization rate of fly ash in China is the same as the world average level,but there are some problems in the comprehensive utilization of fly ash in China due to the large output,uneven distribution and existing national energy policies,such as shrinking demand for traditional building materials,seasonal effects,lack of guidance and no compulsory use of policies,imperfect standard system,low proportion of high value-added utilization,etc.Fly ash is mainly used in building materials industry in China. Compared with other developed countries,its application rate in road and mine backfilling is relatively low.Due to the wide distribution of coal-fired power plants and the demand reduction of building materials industry in the western region of China,the comprehensive utilization of fly ash is far lower than the national water level.The index range and limit value of China's standard on fly ash are relatively loose than those of foreign countries,and most of the fields involved are traditional building materials and infrastructure construction,which cannot guide the application of fly ash in other fields well.Most of the existing relevant policies are to encourage the use of fly ash,which is lack of mandatory,and the content of policies cannot effectively improve the subjective initiative of the ash production enterprises.In order to better promote the comprehensive utilization of fly ash in China,we should start from the following aspects in the future combined with own national conditions and compared with the current situation of developed countries: increase the application of fly ash in construction,filling,agriculture,environmental protection and high value-added utilization; promote the application of fly ash in landfill and agriculture in the western region of China; improve the standards of various utilization ways,which should reflect our own particularity of our country in the standard formulation and give priority to the formulation of local standards; the current utilization of fly ash in China depends too much on the policy,so the policy content should guide the ash production enterprises in detail,so as to improve the subjective initiative of ash treatment of ash producing enterprises; increase the policy of compulsory utilization of fly ash; improve the transparency of solid waste utilization information,and strengthen the social supervision of comprehensive utilization of fly ash.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 2232K]

Research advance on influencing factors and mechanisms of coal selective agglomeration separation process
DONG Zilong;YANG Qiaowen;DOU Meng;ZHAO Jianbing;School of Chemical and Environment Engineering,China University of Mining and Technology-Beijing;
In recent years,based on the high added value and excellent performance of Ultra Clean Coal,it has been widely concerned as a coal-based material.In order to obtain high-quality Ultra Clean Coal,a kind of economic and environmental protection preparation technology was studied.The potential value of Ultra Clean Coal as fuel,raw material and coal based material was introduced. The preparation methods of Ultra Clean Coal can be divided into chemical method and physical method.Due to the acid-base corrosion equipment in the process of preparing Ultra Clean Coal by chemical method,the energy consumption is high,and the coal-based structure is damaged.Therefore,it is of great significance to adopt the economic and environmental protection selective agglomeration method to prepare Ultra Clean Coal.Selective agglomeration method has a good effect on ash removal from coal,and it is the most promising method to prepare Ultra Clean Coal by physical method.The ash content and yield of clean coal are the key problems limiting the development of this technology.In order to reduce the ash content and increase the yield of clean coal,the main influencing factors of selective agglomerations in coal deashing process were summarized.The effect of coal metamorphism degree,particle size,slurry p H value,slurry concentration,stirring intensity and stirring time,electrolyte,dispersant,additives,emulsified oil and bridging liquid on ash content and yield were analyzed.In this paper,the change rules of ash content and yield of clean coal were mainly summarized.Among them,coal metamorphism degree,particle size,stirring intensity and bridging liquid have great influence on separation effect. The results show that the higher the degree of coal metamorphism is,the lower the ash content of ultra pure coal is.Small particle size is conducive to the separation of minerals and coal organic matter.Sunflower oil and soybean oil as bridging fluid are effective for agglomeration of high rank coal,while castor oil has a strong effect on agglomeration of low rank coal,especially high ash coal.When additives( methanol and lauryl alcohol) are added to the bridging solution,the aggregates and ash content decrease.The thermodynamic mechanism and kinetic model of coal agglomeration were discussed.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 2405K]

Research status of coal chemical high-concentrated wastewater treatment and degradation mechanism of characteristic organic pollutants
GAO Minglong;Coal Chemistry Branch of China Coal Research Institute;State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;
It is an important way to realize clean and efficient utilization of coal by the advanced coal chemical engineering,but coal chemical industry wastewater is difficult to be treated economically and effectively.That is mainly manifested in the high concentration of characteristic organic pollutants,such as heterocycles,aromatic hydrocarbons,long-chain alkanes,etc,which seriously restrict the sustainable development of coal chemical industry.The water quality characteristics of high concentration coal chemical wastewater and the step-by-step removal process of organic matter in wastewater were introduced,and the research status of coal chemical wastewater treatment was discussed.The characteristics and existing problems of each technology were analyzed.The selection of Dephenol extractant should be determined after technical and economic analysis according to the content of polyhydric phenol in waste water. At present,anaerobic + multistage aerobic process and the optimization and improvement process based on this process are the common processes for the treatment of high concentration organic wastewater in coal chemical industry,that mainly using the advantages of anaerobic process to improve the biodegradability of wastewater.Ozone catalytic oxidation technology based on no secondary pollution and no increase of salt content in waste water is a suitable choice for advanced treatment,but the effect of catalyst needs to be further improved.The biodegradation mechanism of typical organic pollutants such as phenols,benzene series,alkanes,polycyclic aromatic hydrocarbons and heterocyclic compounds in coal chemical wastewater was discussed emphatically.For example,phenol is first hydroxylated and transformed into catechol,and then metalytic and ortho cleavage can be carried out without bacteria.Resorcinol is first converted to pyrogallol and then further split in ring opening.The aerobic degradation pathway of benzene is relatively clear,however the anaerobic degradation pathway is not clear,but phenol and benzoic acid are important intermediate products in the anaerobic degradation process of benzene. There are four main oxidation ways of long-chain alkane biodegradation: single end oxidation,double end oxidation,secondary end oxidation and direct dehydrogenation.Firstly,different dihydrodiols are formed in PAHs degradation,which are further converted into catechol or gentianic acid for ring opening degradation.The biochemical degradation mechanism of nitrogen-containing heterocyclic pollutants is that denitrifying bacteria use organic matter as electron donor and oxygen in nitrate nitrogen as electron acceptor to carry out metabolic activities.At present,there are many researches on the degradation mechanism of characteristic organic pollutants and the analysis of degradation intermediates,and some achievements have been made. However,there are few researches on the toxicity of intermediates and the control of reaction in different degradation paths,which need to be further explored to find the most favorable reaction conditions and strengthen or accelerate the degradation of organic pollutants.The treatment of high concentration organic wastewater from coal chemical industry should strengthen the physicochemical pretreatment process,reduce the impact on water quality and quantity of biochemical system and make full use of anaerobic process to improve biodegradability,as well as reduce repeated p H regulation in the process of treatment,reduce the increase of salt in the system.It is also suggested to carry out the study on the analysis of the intermediate products,toxicity comparison and optimal control of different degradation paths of the characteristic refractory pollutants in coal chemical wastewater,which is the basis of strengthening the treatment of the coal chemical wastewater.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 1301K]

Progress and perspectives of coking wastewater treatment technology
XIA Liquan;CHEN Guifeng;LI Wenbo;GAO Minglong;China Coal Research Institute;Coal Chemical Branch of China Coal Research Institute;Energy State Key Laboratory of Coal Efficient Utilization and Energy saving Emission Reduction;Beijing Key Laboratory of Coal Based Carbon Materials;
Coking,as a traditional coal chemical industry,has developed rapidly,and most of coking enterprises are distributed in North China where there is relatively little water.Therefore,the effective treatment of coking wastewater plays an important role in the sustainable and stable development of coking industry. In this paper,the research progress of coking wastewater treatment technology was discussed based on the source and water quality characteristics of coking wastewater. The shortcomings of the current coking wastewater treatment technology were pointed out,and its development direction was prospected. Coking wastewater is a typical industrial wastewater,which is difficult to be treated because of its characteristics such as large amount of production and high concentration of organic pollutants.Domestic coking enterprises have relatively weak understanding about the importance of pretreatment section,at present the traditional pretreatment technology is still dominant,and the problems such aslow efficiency,high energy consumption and secondary pollution are outstanding,but the magnetic separation technique in the pretreatment section can be of further application.The anaerobic,anoxic and aerobic technology developed in the 20 th century are mainly used in the biochemical treatment section,which are mature and have been widely used.But the biochemical treatment technology has higher requirements for water quality,especially the wastewater carbon nitrogen ratio( C/N)and the concentration of organic carbon source determine to the final effect of biochemical treatment.Microorganis technology and the development of membrane bioreactor in the future will have great development and breakthrough,and anaerobic technology because of its high energy utilization has attracted the attention of many scholars,and the application of anaerobic technology is helpful to build the ideal type of modern wastewater treatment plants.Deep processing section mainly solves the problem of biochemical effluent substandard,and in the " zero emissions" process,there are higher requirements for the water quality of the membrane,so the depth of processing section is to degradate some organic matters more precisely and specifically,and advanced oxidation technology as a new processing technology is developing rapidly and is gradually adopted by more coking enterprises.The results show that the synergetic effect of the optimization coupling of several treatment technologies can further enhance the treatment effect and make the coking wastewater meet the discharge or reuse standards.With the increasingly strict environmental protection policy,factors such as the popularization of " zero discharge" of wastewater,the acceptable treatment cost of enterprises and the water quality characteristics of coking wastewater jointly determine that the coupling and combination of relatively mature deep treatment technologies such as advanced oxidation technology and membrane separation technology will be the key direction of future development.The development trend of coking wastewater treatment in the future is to improve the utilization rate of resources,improve treatment capacity and efficiency,and reduce energy consumption and operating cost. In the process of coking waste water treatment,membrane separation technology is widely used and at the same time,it can produce high concentrations of saline wastewater.The effective treatment of saline wastewater is related to the points and the purity of salt products,and if the organic pollutants in concentrated brine can not be effectively treated,the treatment cost of the follow-up section will be increased and even the hazardous waste of environmental pollution will be produced.Therefore,the effective treatment for high concentration brine is also the focus of the research community urgent problem.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 1319K]

Study on deashing,desulfurization and upgrading of high sulfur coal by deep-flotation combined with chemical oxidation
XIONG Mingjin;HUANG Yetian;FU Jian'gang;ZHAO Di;WANG Xiaobo;Shanghai Rupai Mining Equipment Co.,Ltd.;School of Chemistry and Chemical Engineering,Central South University;
With the gradual decrease of high-quality coal resources in China,the development and utilization of low-quality coal such as high-sulfur coal is an important way to ensure the safety of coal energy.The research on deashing and desulfurization and upgrading of high sulfur coal is the first choice for clean and efficient utilization of high sulfur coal.In this paper,a deep flotation combined oxidation method was used to conduct a deashing and desulfurization and upgrading experiment of high-sulfur coal in Guizhou.The contact angle was used to test the performance of different collectors,and the effects of different collectors on flotation deashing were studied.The influencing laws of different ash inhibitors and sulfur inhibitors on flotation desulfurization and desulfurization were conducted in closed-circuit flotation experiments.The chemical oxidation was used to further desulfurize the flotation clean coal.The effect of different oxidants on the chemical desulfurization of flotation clean coal was studied.The mechanism of deashing and desulfurization was proved by infrared spectroscopy and scanning electron microscopy. The results show that,compared with diesel,the composite collector M7015 has more advantages in flotation deashing.The contact angle of raw coal is 62.5°.The contact angle of coal after M7015 treatment is increased by 15.0°,and the contact angle after diesel treatment is increased by 5.0°,the optimal dosage of M7015 is 800 g/t.Calcium oxide has a good effect as a desulfurization inhibitor,the dosage is 4 000 g/t,and the optimal dosage of ash inhibitor S-4 is 1 000 g/t. Through the " one coarse-two sweep-two fine" closed-circuit flotation test process,the flotation clean coal with 5.62% ash and 1.34% sulfur content is obtained.The mixed solution of hydrogen peroxide and glacial acetic acid has the best oxidative desulfurization effect.After the flotation clean coal is oxidized,low-ash low-sulfur clean coal with ash content of 5.60% and sulfur content of 0.88% is obtained.SEM analysis shows that the particles attached to the coal surface are reduced,the surface is smooth,the mineral particles between the cracks are significantly reduced,and the effect of deep flotation deashing and desulfurization is obvious. Infrared spectroscopy shows that deep flotation combined with chemical oxidation does not change the basic structure of coal,but can remove most of the ash,and most of the inorganic sulfur such as pyrite is removed by floation,and some organic sulfur such as sulfide and sulfoxide is removed by chemical oxidation.This shows that the new process of deep flotation combined with chemical oxidation has achieved the experimental goal of deashing,desulfurization and upgrading of high-sulfur coal,and obtained high-quality low-ash and low-sulfur clean coal products.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 5426K]

Effects of polymer containing wastewater from oil production on preparation and properties of coal water slurry
ZHANG Hao;WEI Zheng;JIANG Yong;XIE Qiang;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;Poten Environmental Group Co.,Ltd.;
With the development and application of polymer flooding technology,the recovery rate of crude oil is greatly improved.Meanwhile,a large number of polymer containing wastewater is produced,resulting in environmental pollution. The utilization of industrial wastewater in the preparation of coal water slurry( CWS) is one of the effective ways to treat industrial wastewater.However,there are few studies on the use of polymer containing wastewater in the preparation of CWS.In order to study the effect of polymer containing wastewater on the preparation and performance of CWS,coal water slurry( CWS) was prepared by using Shenmu bituminous coal as raw material and naphthalene sulfonate formaldehyde condensate as dispersant and anionic polyacrylamide( HPAM) containing wastewater from oil production When the amount of dispersant and the CWS concentration were experimentally determined,the influence of the dosage of polymer containing wastewater on the rheology and stability of CWS was investigated.The results show that the performance of coal water slurry( CWS) prepared from polymer containing wastewater is good.The apparent viscosity of CWS decreases first and then increases with the increase of the amount of dispersant,and increases with the increase of CWS concentration.The CWS has good performance with the maximum pulping concentration of 56.6% and the apparent viscosity of 1 183 m Pa·s when the concentration of dispersant is 0.8%.The rheological properties of CWS is affected by the addition of polymer containing wastewater.With the increase of the proportion of polymer containing wastewater,the rheological properties of CWS first decreases and then becomes better.When the mixing ratio of wastewater is less than20%,the CWS has low apparent viscosity,good fluidity and more obvious pseudoplastic fluid.The addition of polymer containing wastewater also has great influence on the stability of CWS.The stability of CWS firstly increases and then decreases as the proportion of polymer containing wastewater increases.The stability of CWS can be improved by mixing waste water with a lower proportion( < 40%),for that the addition of polymer containing wastewater improves the slurry structure and makes the CWS hard to form hard precipitation.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 3109K]

Numerical simulation of oil residue spray effect by nozzle in pressurized fixed bed slag gasifier
XU Chunxia;DONG Weiguo;Coal Chemical Branch of China Coal Research Institute;Beijing Key Laboratory of Coal Based Carbon Materials;State Key Laboratory of Coal Mining and Clean Utilization;
In order to explore the feasibility of oil residue gasification in fixed bed slag gasifier,gasifying oil residue and coal together in the fixed bed slag gasifier can produce clean syngas or gas,so as to broaden the efficient utilization way of oil residue.In this paper,the dispersion effect of oil residue after being sprayed by the nozzle in a fixed pressure bed slag gasifier was studied.Taking Shenhua Coal Direct Liquefaction residue as the research object,the impact of oil residue temperature,oil residue spray velocity and air spray velocity on the spray effect of oil residue under pressure in the industrial-grade pressurized fixed bed slag gasifier was studied by using the numerical simulation software Ansys Fluent.Realizable κ-ε turbulence model was adopted to simulate turbulence flow,and the gas-liquid two-phase flow was simulated by VOF model of Euler-Euler method. The nozzle structure was double-channel. The center channel of the nozzle was used for conveying oil residue,and the annular gap channel was used for conveying gasification agent( replace with air). The optimal spray scheme was determined by analysis and comparison.The following conclusions are drawn: The viscosity of oil residue decreases with the increase of temperature under pressure condition,the viscosity of oil residue drops sharply with the increase of temperature from 210 ℃ to240 ℃; the viscosity of oil residue decreases with the increase of temperature from 240 ℃ to 400 ℃,but the decrease gradually weakens.When the temperature exceeds 400 ℃,the viscosity of oil residue gradually increases with the increase of temperature,which may be caused by polycondensation reaction of oil residue. The spray temperature plays a decisive role in the spray effect of oil residue in the gasifier.The lower the oil residue temperature is,the better the diffusion effect will be after the oil residue spray.However,when the oil residue spray temperature is too low,a large amount of oil residue will begin to flow downward under the influence of gravity,which leads to the relatively short distance of spray due to the great viscosity,and even flow into the slag pool along the wall.There is a relatively optimized spray temperature range.the phenomena of diffusion and adherence should be considered in the selection of the atomization effect of oil residue.The spray effect of oil residue in gasifier under pressure is influenced by pressure and dynamic viscosity.To increase the spray pressure and achieve the same spray effect,it is necessary to increase the spray temperature of the oil residue to reduce the dynamic viscosity of the oil residue.When the spray velocity of oil residue is in the range of 2.5-10.0 m/s,it has little effect on the atomization effect of oil residue in gasifier.In the range of 5-20 m/s,the higher the spray velocity of air is,the better the atomization effect of oil residue in the gasifier is.Considering comprehensively,under 4.5 MPa,the spray temperature of oil residue is 230-260 ℃,the spray velocity of oil residue is about 5 m/s,and the spray velocity of air is about 10 m/s,which is a more suitable spray scheme and the spray comprehensive effect of oil residue is better.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 7496K]

Numerical simulation study on gas-solid fluidization characteristics of the particles with narrow size distribution
GUO Haoqian;LI Xuefei;LI Xiaoliang;Coal Chemistry Branch of China Coal Research Institute;Beijing Key Laboratory of Coal Based Energy Conservation and Environmental Protection Carbon Materials;State Key Laboratory of Coal Mining and Clean Utilization;
In order to better guide the industrial production,understand the state of particles of different particle sizes in the gas-solid fluidized bed and the distribution of particles in the fluidized bed,the fluidization characteristics of the narrow-screened particles in the gassolid fluidized bed were numerically simulated.The flow field simulation software was used to analyze the volume fraction and the height of the fluidized bed and the time required to reach this target under the conditions of particles with different particle sizes( 46-80,106-113,185-221 μm) in the same fluidized bed and different inlet velocity of the fluidized bed. The Euler-Euler model and SIMPLE algorithm were used to calculate the particle volume fraction and velocity distribution under different gas velocity conditions.The results show that the increase in particle size causes the larger difference between the highest point and the lowest point of the particle volume fraction in the fluidized bed under the same gas velocity,meanwhile,the unevenness of particle distribution increases,the overall height of the bed decreases,the particles in the bed density increases,the fluidization decreases with the decrease of the volume fraction of the particles.In the case of the same particle size,increasing the gas velocity can reduce the volume fraction of particles inside the fluidized bed,increase the contact area of the gas and solid particles,and enhance the fluidization effect.However,the time of the particle velocity vector distribution inside the fluidized bed reaching a uniform is reduced,and the uneven distribution of particles is more obvious.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 8853K]

Structure analysis of low rank coal and its correlation with pyrolysis tar yield
BAI Xiang;ZOU Da;MA Fengyun;LIU Jingmei;ZHONG Mei;School of Chemistry and Environment,Yili Normal University;College of Chemical and Engineering,Xinjiang University;Xinjiang Laboratory of Coal Clean Conversion & Chemical Engineering Process Key laboratory of Autinomous Region;
The composition and structure of six different low-rank coal samples were determined via elemental analyzer and solid13 C-NMR apparatus.The Peak-fit software was used to analyze the13 C-NMR spectrum to semi-quantitatively calculate the ratio of different types of organic carbon in coal samples,and the influence of organic carbon types on tar yield was investigated by Matlab mathematical software.The results show that:( 1) The content of methylene carbon in WCW,PLQ,JJM,TCG,HG and HF coal samples accounts for 34. 41%,34.29%,34.01%,44.78%,41.62% and 49.94% of the total lipid carbon content,respectively.The content of methylene carbon in aliphatic carbon in coal sample structure is high,and the number of aliphatic chain N is less than 9,which indicates that the branched chain connected on the short chain mainly exists in the form of the alicyclic side chain.( 2) The average methylene carbon number of HF coal sample is Cn= 2.13,the rest are less than 2,WCW is the smallest,only 1.05,indicating that aliphatic group is mainly short chain and the chain length is generally 1-3 carbon.( 3) Methylene carbon( I2) is the key factor that controls the coal tar yield,while proton aromatic carbon( I4) and proton with alkyl chain branched degree( I7) are as auxiliary factors.Binary combination of I2 and I4 show a good linear relationship with tar yield.The three-element composition of I2,I5( phenolic hydroxyl or ether oxygen carbon) and I7 has the greatest relevance of coal tar yield,and its Ra2 djis 0.992.( 4) The vitrinite content in different coal samples increases from 26.10% to 82.10%,the number of fragile bridge bonds n and the dehydrogenation content WHincreases from 5.37 to 8.17,3.24 to 5.92.The results show that the smaller the number of crosslinked bridge bonds P0 is,the lower the degree of crosslinked reaction is,the higher the number of brittle bridge bonds n and the dehydrogenation content WHis,the smaller the number of crosslinked bridge bonds P0 is,and the greater the tar characteristic index Xtaris,and the more favorable the tar generation process is.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 2163K]

Study on influencing factors of phenols formation in direct liquefaction of Aiding lignite
LIANG Jiangpeng;Coal Chemistry Branch of China Coal Research Institute;Beijing Key Laboratory of Coal Based Carbon Materials;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;State Key Laboratory of Coal Mining and Clean Utilization;
According to the characteristics of high oxygen content of Aiding lignite,the hydrogenation liquefaction of Aiding lignite were investigated in the autoclave.The effects of reaction temperature,amount of catalyst loading,H2 initial pressure and solvent content on the formation of phenols in direct liquefaction products of Aiding lignite were investigated.The results show that the optimum conditions for the direct liquefaction of Aiding lignite to produce phenolic compounds are listed as follow: reaction temperature 430 ℃,catalyst addition 1%,hydrogen initial pressure 5.0 MPa,solvent content 50%. The proportion of low-boiling phenol in total phenol is 0. 39% phenol,0. 51%o-cresol,1.08% m-cresol,0.97% p-cresol and 5.07% xylenol,respectively.The lower phenol( phenol + C1 phenol + C2 phenol) accounts for 10.7% of the total phenol by alkaline extraction of coal liquefaction oil,and the retention time of low-boiling phenol is 24-33 minutes,high phenol accounts for a large proportion,which is both abundant and complex with the extension of retention time.The increase of reaction temperature,catalyst content,and solvent content can promote the total phenol yield and the reaction of coal to produce phenolic compounds,while the hydrogen initial pressure has little effect on the total phenol yield.The increase of reaction temperature and catalyst content promotes the proportion of low-boiling phenol in total phenol,which makes the high-boiling phenol tend to produce low-boiling phenol,while the solvent content and initial pressure of hydrogen inhibit the proportion of low-boiling.In the process of direct coal liquefaction,high phenol yield can be achieved in the process of low temperature separation through hydrogenation reaction.And through circulation of high fraction,the reaction time of high fraction is prolonged and the oil yield can be increased,that is to say,it will be beneficial to control and increase the yield of oil and phenol by the graded hydroliquefaction.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 3067K]

Experimental study on catalytic cracking of coal tar by semi-coke
LIU Siyuan;ZHANG Jun;CAI Jinyu;LU Qi'an;School of Energy & Environment,Southeast University;
In order to improve the catalytic cracking effect of semi-coke from lignite pyrolysis on tar,the semi-coke prepared by coal pyrolysis was used to catalyze the pyrolysis of coal tar.Two-stage fixed bed reactor was used to study the effects of coking temperature,char consumption and oxygen activation on the catalytic cracking of tar.Coal samples were placed in the upper section of the reactor for pyrolysis,and semi-coke catalyst was placed in the lower section to catalyze the pyrolysis of tar produced in the upper section.The results show that the yield of tar decreases obviously with the increase of coking temperature of lignite.The yield of tar is only 6.3% when the activated semi-coke prepared from lignite at 900 ℃ is 1 g.Increasing the coking temperature is beneficial to the catalytic cracking of macromolecular aromatics in tar into less-loop substances and small-molecule components.Increasing the char consumption has no obvious effect on tar removal,the tar yield decreases slowly.Compared with the unactivated char,the char activated by O_2 has better removal effect on tar.Specific surface area and pore analysis of semi-coke( BET) show that the activated char has larger specific surface area and more pore space.Energy spectrum analysis( EDS) shows that the total amount of metal elements on the surface of activated char is higher than that of unactivated char.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 8582K]

Pore structure control of coal based activated carbon prepared by briquetting method in the presence of FeCl₃
YAO Xin;YANG Qian;ZHAO Xuesong;YE Pengtao;WANG Shuaishuai;QIU Lijun;School of Chemistry and Chemical Engineering,Hefei University of Technology;
In order to adjust the pore structure of coal-based granular activated carbon,a series of activated carbon samples were prepared by briquetting method with Datong bituminous coal and Lingwu bituminous coal as raw materials,using FeCl_3 as the additive.The effects of different Fe introducing methods including mixing,impregnation and ion exchange on the porosity and the magnetic properties of AC samples were investigated.The carbonization process of coal samples and the activation process of carbonized materials were simulated by thermogravimetric analysis.The microcrystalline structure and mineral composition of the carbonized material samples were analyzed by X-ray diffraction.The pore structure and magnetic properties of AC samples were respectively characterized by N2 adsorption-desorption isotherms and vibrating sample magnetometer.The results show that the weight loss rate of coal samples increases before 350 ℃ and decreases between 350 ℃ and 600 ℃ after Fe is introduced into the coal by mixing method and impregnation method. And the graphitization degree of carbonized materials decreases,the gasification reactivity increases,and the specific surface area of activated carbon increases.The BET specific surface area of Datong coal-based activated carbon prepared through Fe-impregnation increases from 672.4 m~2/g to 704.6 m~2/g and the value for Lingwu samples increases from 498.9 m~2/g to 774.1 m~2/g.The magnetic properties of activated carbon samples can be significantly enhanced by mixing method and impregnation method.After Fe is introduced by mixing method,the saturation magnetization of Datong activated carbon and Lingwu activated carbon increases from 1.343 0 emu/g and 2.639 9 emu/g to 4.417 5 emu/g and 9.146 5 emu/g,respectively.Because of the weak ion exchange capacity of the raw coals,Fe is not introduced by ion exchange method.On the contrary,the content of Ca and Fe series primary minerals in raw coal is reduced due to the acidity of the solution,and the pore structure development of activated carbon is limited.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 3148K]

Experimental study on combustion of high alkali coal in horizontal liquid slag cyclone furnace
LAN Dehui;FAN Junjie;ZHANG Zhongxiao;HU Xinglei;CHEN Songlin;School of Architecture and Environment,University of Shanghai for Scinece and Technology;School of mechanical engineering,Shanghai Jiaotong University;School of Energy and Powering Engineering,University of Shanghai for Scinece and Technology;
In Xinjiang region of China,the reserves of high alkali coal are huge.However,the primary minerals of coal in this region contain a large amount of alkali metals such as Na and K,which results in that such coal types cannot be directly burned in Xinjiang.Many power plants have to mix other coal to meet the normal operation of the boiler,which greatly limits the extensive use of the coal.The boiler technology of liquid slag discharge cyclone furnace combustion is a boiler technology that causes most of the ash produced by coal combustion to form a liquid slag film in the cyclone burner and is discharged from the bottom of the boiler.It has certain advantages in solving the problem of strong contamination and slagging of high alkali coal in Xinjiang.In order to study the characteristics of capturing alkali metal in the liquid slag horizontal cyclone furnace by using Xinjiang high alkali coal liquid slag,in this paper,a liquid slag horizontal cyclone test furnace under laboratory conditions was built.And the combustion experiment of coal from Shaerhu in Xinjiang was carried out,and the ash sample collected in the horizontal liquid slag discharge cyclone test furnace during the experiment was analyzed by SEM-EDS,and the solid alkali rate of the alkali metal in the ash sample was calculated according to the analysis results.During the experiment,the formation of liquid slag on the inner wall of the furnace was observed and the temperature distribution in the furnace was measured and analyzed.The research results show that: after the test conditions are stable,the overall temperature distribution in the cyclone furnace is relatively uniform.Shaer Lake coal is suitable for liquid slag discharge horizontal cyclone combustion furnace. When the combustion temperature is1 300 ℃,liquid slag begins to form in the cyclone furnace.With the increase of the combustion temperature,the formation of liquid slag in the furnace is more obvious.When high alkali coal is used in the horizontal liquid slag discharge cyclone furnace and the liquid slag is formed in the furnace,the Fe element in the liquid slag will stick to the surface of the aluminosilicate particles and increase its viscosity and enhance the ability of the sintered layer to capture ash particles and promote the growth of the slag layer.The use of horizontal liquid slag discharge cyclone furnace with high alkali coal can effectively alleviate the problem of fouling and slagging on the inner wall of the furnace,and the mitigation effect of the high temperature combustion area is more obvious than that of the low-temperature combustion zone.When high alkali coal is burned in the horizontal liquid slag discharge cyclone furnace,the capture efficiency of the liquid slag to alkali metals Na and K can reach more than 50%,and the highest can reach 61%,which is higher than its own solid ash and the capture efficiency of Na by adding kaolin in high temperature area.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 14626K]

Experimental study on air-staged combustion of 58 MW pulverized coal industrial boiler
NIU Fang;China Coal Research Institute Company of Energy Conservation;State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;
It is urgent to speed up the environmental protection transformation of coal-fired industrial boilers and effectively reduce the emission of air pollutants,especially the emission of nitrogen oxides.Air staged combustion technology is a low nitrogen combustion technology with significant emission reduction effect and low transformation cost,which has been successfully applied in a large number of utility boilers.In order to investigate the application effect of air staged combustion technology in pulverized coal industrial boiler,a 58 MW pulverized coal industrial boiler air staged transformation project of Coal Research Institute was studied and six nozzles were arranged on the side wall to realize air staged combustion.Through engineering test,the flue gas temperature and flue gas composition at three different sections( 10 sampling points for each section) and six measuring points in the double cone burnerwere measured by using special water-cooled sampling gun and high temperature resistant flue gas analyzer under the original working condition and staged combustion working condition.The results show that a high temperature and strong reducing atmosphere is formed after x = 0.3 m measuring point in the burner under the condition of air-staged combustion,which effectively inhibits the formation of NOxin the initial stage of combustion.This is because the oxygen in the burner is consumed rapidly under the air-staged condition,the combustion reaction rate of char is significantly reduced,the gasifications are significantly enhanced,and a strong reducibility is formed which effectively curbs the generation of NOx.The variation law of flue gas temperature and composition in different sections of the furnace shows that the temperature distribution of flue gas in the original working condition is generally high in the center and low in the outside,and the distribution trend of oxygen content is just opposite to that of temperature distribution. However,the air-staged combustion is affected by the strong reductive high-speed flame of burner and the air injection on the fire,the section temperature fluctuates greatly,and the jet center of the burner is lower in the middle section in the middle section.In the air-staged combustion,there is an obvious reduction zone in the furnace,which is characterized by high CO concentration in the center and low CO concentration on the outside,effectively reducing NOxgeneration in the furnace.The air-staged retrofit of 58 MW pulverized coal industrial boiler has created a reasonable oxygen deficient reduction zone in the burner and furnace,which has a good effect of low nitrogen.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 2174K]

Application ofoxygen-enriched and low NO_x combustion steady technology during flexibility peak-load regulating of 300 MW pulverized coal boiler unit
CHEN Zixi;WANG Qing;WANG Quanhai;LEI Yunhong;LI Jianbo;JIA Yi;KANG Yinhu;LU Xiaofeng;Key Laboratory of Low-grade Fuel Efficient Clean Utilization Technology and System,Chongqing University;Chongqing Furan Technology Co.,Ltd.;
In order to demonstrate the practical application of oxygen-enriched and low-NOxstable combustion technology,the steady combustion characteristics of oxygen-enriched and low-NOxtechnology on a 300 MW sub-critical pulverized coal-fired boiler under low load were studied.After transforming the original 12 primary air burners at A and D floors of the boiler into oxygen-enriched and low-NOxones,the main operating parameters of the boiler were measured and analyzed.The influence of oxygen-enriched and low-NOx stable combustion technology on original NOxemission concentrations and flue gas temperature at the SCR inlet and the overall operating characteristics of the boiler were studied in detail.The results of field tests,daily operation and performance testing done by third parties show that the original NOxproduction is significantly reduced after the original boiler being modified and applied with oxygen-enriched and low-NOxstable combustion technology.The operation after the transformation proves that the boiler can maintain stable operation at a minimum of 23.5% load( 70.4 MW).At the same time,it can ensure that the superheated and reheated steam parameters at the boiler outlet meet the operating requirements,and the SCR inlet flue gas temperature is maintained above 280 ℃ and the original NOxgeneration concentration is lower than300 mg/Nm3,so as to achieve the ultra-low-NOxemission.The statistical analysis of boiler operation economics shows that the peak shaving capacity is greatly improved after using the oxygen-enriched and low-NOxstable combustion technology,which can make boiler operate for a long time at low load,and can be effectively put into the SCR denitration system. The average annual ignition and low-load stable combustion oil is reduced by 65%.Therefore,the oxygen-enriched and low-NOxstable combustion technology can achieve low-load stable combustion and ultra-low emission of the boiler,and greatly reduce the boiler ignition and stable combustion oil,and improve the economy of boiler.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 979K]

Study on the formation and conversion characteristics of gaseous component CO/CO₂ with fluidized preheating pulverized coal
LIU Yuhua;LIU Jingzhang;LYU Qinggang;ZHU Jianguo;ZHU Shujun;Institute of Engineering Thermophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;Institute of Mechanics,Chinese Academy of Sciences;
The preheating combustion technology based on circulating fluidized bed proposed is one of the new clean coal combustion technologies.The O_2/CO_2 ratio in the gas after fluidized preheating process has a great influence on the subsequent combustion and emissions.Exploring the coke combustion model that can correctly reflect the O_2/CO_2 ratio will help to further understand the fluidized preheating process.Based on the pulverized coal fluidized preheating conversion process,the typical preheated air-rich atmosphere( O_2/N2),oxygenrich atmosphere( O_2/CO_2),and fuel type change were used to study the conversion characteristics of the gaseous component CO/CO_2 after preheating.Moreover,the degree of matching between the existing coke combustion model and the fluidized preheating process was analyzed.The experimental data and model predictions show that in the air-rich oxygen atmosphere,as the oxygen concentration increases from 21% to 28.2%,the proportion of CO_2 in the preheated gas produced by Shenmu semi-coke fluidized preheating process decreases,the proportion of CO increases,and the CO/CO_2 ratio increases from 0.81 to 1.45.When Shenmu bituminous coal is preheated in the same atmosphere,the above-mentioned parameters show the same tendency as Shenmu semi-coke,and the CO/CO_2 ratio increases from 0.51 to0.76 as the oxygen concentration increases from 21.0% to 24.4%.In the oxygen-rich atmosphere,the CO produced by Shenmu semi-coke preheating is higher than that of Shenmu bituminous coal. The CO/CO_2 ratio also increases with the increase of oxygen concentration,but compared with the air-enriched atmosphere,the increasing degree is smaller. The experimental data of the preheated gas component CO/CO_2 of Shenmu bituminous coal is the most consistent with the prediction of the coke combustion model proposed by Tognotti,and the error of experiment and prediction results is within 9% under oxygen-rich atmosphere
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 1841K]

Study on the numerical simulation of flow field optimization in SCR system
WANG Haichuan;ZENG Xianghao;LIAO Yanfen;TIAN Yunlong;MA Xiaoqian;School of Electric Power,South China University of Technology;
In order to improve the flue gas flow uniformity of SCR system,improve the catalytic efficiency of SCR reactor,reduce the erosion and loss of catalyst,increase the service life of catalyst and improve the contact degree of reactants,in this study,the flow field of SCR reactor was simulated and the structure optimization of guide plate and rectifier plate was carried out.The purpose of the study is that through the simulation of velocity field of full scale SCR reactor model,Realizable k-ε model and porous medium model were used to study the effects of diversion plate structure,number of rectifier plates and fly ash deposition on the flow field organization and the air flow uniformity of SCR denitrification system.At the same time,the influence of fly ash particles on the flow field was studied by simulating the particle distribution in the SCR reactor.By calculating the relative velocity deviation of the section in front of the rectifier plate and analyzing the velocity field of SCR reactor under different optimization schemes,the diversion effect of the guide plate and the rectifier plate was evaluated,and then the best scheme was determined.The results show that the " straight arc" guide plate has the best effect among the four kinds of deflector schemes,because the horizontal straight plate and vertical straight plate in front of the arc guide plate can better guide the air flow.According to the geometric characteristics of inclined top design in reactor,the shape optimization of the right guide plate can significantly improve the velocity uniformity,which can significantly optimize the air distribution of flue gas and reduce the energy dissipation at the turning.The rectifier plate in front of the homogeneous catalyst layer can further guide the flow of airflow and greatly improve the uniformity of airflow.However,too many rectifiers increase the gas flow resistance near the wall,aggravate the energy dissipation and velocity inhomogeneity and reduce the rectifying effect of the rectifiers.In this model,the appropriate number of rectifiers is 15.Ultimately,the deviation of upper catalyst velocity is reduced to 6. 68%,which meets the industrial requirements. The analysis of the flue gas particle field shows that the fly ash particles are deposited on the right wall of the flue and the upper wall of the ascending channel,and the necessary fly ash treatment at the particle deposition can reduce the erosion effect of the fly ash on the catalyst.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 2657K]

Flow field simulation and technology development of integrated dedusting and denitration at high temperature
WANG Wei;ZHU Zhaoping;ZHANG Chucheng;CHEN Mu;SU Yinbiao;ZHENG Xiaopan;Central Southern Electric Power Design Institute;Fujian Longking Co.,Ltd.;
Compared with the SCR-De NOxsystem of high temperature and high dust area arrangement,the arrangement of high temperature and low dust area has obvious advantages in protecting catalyst and air preheater.An integrated technology of high temperature dedusting and denitrification was proposed,which combined high temperature electric bag composite dust collector and SCR denitrification reactor.Three types of flow in and out of the denitrification reactor,including lower flow in and upper flow out,side flow in and side flow out,upper flow in and lower flow out were compared and analyzed.The results show that the first type has the advantages of simple structure and high economy.At the same time,,using a 350 MW unit as an example,the numerical simulation of high temperature dedusting and SCR-De NOx integrated device was carried out by using Fluent software.The flow field distribution inside the device was analyzed,and the optimized design scheme was proposed. The simulation results show that the flow field distribution in device can be improved and the vortex in the flue can be reduced by improving flue structure and design diversion measures( flue deflector,rectifier grille,adjusting orifice opening rate,ash-bucket baffle,etc.).After optimization,the velocity distribution variation coefficient at inlet section of AIG,the first electric field,the1 st catalyst and air preheater are decreased from 27.1%,12.1%,38.8%,17.6% before optimization to 22.4%,22.3%,5.5%,11.3%,respectively.And,the ammonia concentration distribution variation coefficient and the flue gas incidence angle at inlet section of the 1 st catalyst are reduced from 15.0% and 172° before optimization to 3.8% and 5.3°,respectively,so as to meet relevant technical requirements of flow field,and provide reliable guidance for engineering design.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 15517K]

Selective photocatalytic reduction of CO₂ into CH₄ by Pt and Cu co-modified TiO₂
LI Changhua;ZHAO Jiangting;XIONG Zhuo;ZHAO Yongchun;National Energy Group Jiangxi Power Generation Corporation;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
Photocatalytic reduction of CO_2 is a challenging renewable energy production technology.However,due to the rapid recombination of photogenerated electron hole pairs and the limited utilization of visible light,TiO_2 shows low photocatalytic reaction efficiency.In order to improve the efficiency of photocatalytic reduction of CO_2 by Ti O_2,it is an effective way to modify TiO_2 by metal.In this paper,Pt and Cu_2O nanoparticles were co-deposited on the surface of TiO_2 nanocrystals by chemical reduction method.The influence of Pt and Cu co-modification on the photocatalytic reduction of CO_2 by Ti O_2 was systematically studied.The experimental results show that Pt deposition tends to promote the production of CH_4 and H_2.However,Cu_2O can suppress H2 production and exhibites lower CH_4 selectivity than that of Pt.Furthermore,after co-deposition of Pt and Cu_2O on Ti O_2 crystal,the formation of H_2 is inhibited,and CO_2 is selectively converted to CH_4,with a selectivity of 96.6%.The characterization experiments and a series of photocatalytic reduction selectivity experiments show that Pt can not only capture the photogenerated electrons,but also improve the electron density on the catalyst,which is conducive to the multi-electron reduction reaction and the formation of CH_4 with high selectivity.Cu_2O enhances the chemical adsorption of CO_2 on TiO_2 and inhibites the adsorption of water,thus the formation of H_2 is inhibited and the selectivity of photogenerated electrons for CO_2 reduction is improved.In addition,Cu_2O in Pt-Cu/TiO_2 after the reaction is almost completely reduced to Cu,which may be caused by the process of photocatalytic reaction,Pt deposition can promote the transfer of photogenerated electrons to Cu_2O. This phenomenon can provide more electrons for the photocatalytic reduction while reducing Cu_2O to zero valent Cu,which is conducive to the selective generation of CH_4.Therefore,Pt-Cu/TiO_2 catalyst can selectively reduce CO_2 to CH_4.After three cycles of tests,the activity of the catalyst is not reduced and has good stability.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 4087K]

Theory and key technologies of high efficiency desulfurization in circulating fluidized bed boilers
TAN Bo;WANG Chuanzhi;SI Shuo;LIU Zhongpan;LAN Tian;The Engineering and Research Center for Clean Coal Technology,Yankuang Group Co.,Ltd.;Yankuang Technology Company Ltd.;
Desulfurization technology is one of the most effective and optimal way to achieve clean coal combustion in circulating fluidized bed boilers,which is low-cost,no wastewater produced and simple to operate.In addition,there are many influencing factors and the reported data is significantly scattered,which make it too difficult to derive a generalized approach to predict the desulfurization performance,and there is not a reasonable explanation for this seemly abnormal declination in desulfurization efficiency with increasing Ca/S ratio in the process of practical application,and the simple Ca/S ratio cannot be fully represent the amount of limestone actually involved in desulfurization,it is difficult to fully describe the desulfurization law of limestone in the furnace. Based on the movement and distribution law of materials in the boiler,the new concept of"effective limestone inventory"was proposed in order to explore the essence of determining the desulfurization efficiency of limestone in the furnace,and through comprehensive analysis on desulfurization in circulating fluidized bed boilers.A mathematical model was established according to the principle of ash mass balance.The validity of model was validated by comparing with the experimental results of industrial circulating fluidized bed boilers with different scale burning coal particles and coal slime.The results reveal that the key factor that actually determines the desulfurization efficiency in CFB boilers is"the effective limestone inventory".This theory and model provide significantly useful guideline for effectively improving the desulfurization efficiency in the furnace.Based on the theory,it concludes that the key technologies to achieve efficient desulfurization in the furnace include:( 1) optimizing the limestone particle size distribution to effectively increase the limestone quantity in the external circulation and the residence time in the limestone furnace;( 2) smoothing the way to discharge the bottom ash so the loss of the effective limestone can be minimized;( 3) improving the gas-solid contact efficiency so the activity of the effective limestone can be fully utilized.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 4112K]

Catalytic oxidation NO removal and thermal regeneration experiment by activated coke at low temperature
LI Ting;PAN Guanfu;China Coal Research Institute Company of Energy Conservation;
Active coke is a kind of carbon based catalytic denitrification material with high cost performance.In order to study its denitrification performance and thermal regeneration under the condition of low temperature and no NH3,the fixed bed experimental device was used to evaluate the performance of NO removal at low temperature and in-situ thermal regeneration experiment.The specific surface area,pore size distribution and surface functional groups of the two experimental active coke were characterized and analyzed to study the influence of surface characteristics on the NO removal performance.The effect of active coke on NO removal at low temperature and the mechanism of thermal regeneration were preliminarily discussed.The results show that under the experimental conditions of NO removal with the inlet volume concentration of NO 100 × 10-6,the volume concentration of O_26%,the reaction temperature 70 ℃ and the space velocity1 000 h-1,the outlet NO concentration increases gradually with time,and the denitrification rate decreases linearly.Combined with the infrared characterization,it is qualitatively indicated that there is catalytic oxidation and adsorption in the process of NO removal from the active coke.The possible mechanism is that the active functional group in the active coke oxidizes NO to NO_2,which occurs on the pore surface of the active coke in the form of adsorbed NO_2,and some of the chemically adsorbed NO_2 reacts with disproportionation on the surface of the active coke,forming adsorbed NO_3.Under the thermal regeneration test conditions of 6% O_2,70-400 ℃ regeneration temperature and 2 ℃/min heating rate,the NO concentration first increases rapidly,reaches the platform at 100-150 ℃,and reaches the peak value of desorption capacity at 210 ℃ .At this time,the conversion concentration of NO desorption is about 85 mg/m3,and then the NO concentration gradually decreases to zero.When the simulated flue gas is above 250 ℃,CO begins to separate out,and the amount of CO generated is directly proportional to the regeneration temperature.In the process of in-situ thermal regeneration of the activated coke after denitration,the adsorbed NO_2 is decomposed into NO and released.The microstructure of the two kinds of activated coke samples is similar.The isothermal curves of AC1 and AC2 belong to IV type isothermal curves,and the hysteresis loop belongs to H4 type,which shows that the microstructure of the two kinds of samples is mostly slit like pores.The adsorption capacity at the inflection point of the low P/P0 area of the adsorption desorption curve,pore volume and BET specific surface area of AC2 are slightly larger than those of AC1,indicating that there are more micropores in the former sample.The pore size of AC1 and AC2 are 1.76 and 1.57 nm,respectively.The results of XPS and denitrification performance evaluation of the two samples show that the denitrification activity of the active coke samples containing more oxygen/nitrogen functional groups is stronger.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 1413K]

Research and application of on-line monitoring system for CO₂ emissions from thermal power enterprises
LI Zhenghui;LU Weiye;PANG Xiaokun;LI Yunquan;BAI Kaijie;LI Yuesheng;LU Zhimin;YAO Shunchun;School of Power,South China University of Technology;Guangdong Province Engineering Research Center of High Efficient and Low Pollution Energy Conversion;Shunde Inspection Institute of Special Equipment Inspection and Research Institute of Guangdong Province;Foshan Shunde Wusha Thermal Power Co.,Ltd.;
The important foundation for the efficient operation of carbon trading mechanism is the objective,accurate and credible carbon emissions data.At present,the emission factor method is often used to account the greenhouse gas emissions,which has many disadvantages such as low accuracy,low efficiency of collecting data,and severe timeliness lag.Compared with the emission factor,the direct monitoring has the advantages of measure convenience,real-time and high efficiency of collection,less human intervention and so on.But there are few researches and applications on this aspect in China.Therefore,in this paper,the methods of the direct monitoring for coal-fired power generation enterprises were summarized,and a carbon emission online monitoring system for thermal power enterprises was developed. It was successfully applied in a 320 MW cogeneration enterprise,which could achieve online monitoring of major emission parameters such as total carbon emissions,carbon emission rate,etc.,and the statistical of historical data. Based on the carbon emission data monitored by the system,the results of direct monitoring and accounting of carbon emissions were compared,and the reasons for the differences of each other in this paper were analyzed.Meanwhile,with many production datas from the enterprise such as coal consumption,the low-level heat generation of coal,the power supply,the heat supply and so on,the relationship among the direct monitoring of carbon emissions and boiler output energy,carbon emissions per unit of product and boiler efficiency was calculated and analyzed.The results show that the carbon emissions of direct monitoring are about 5%-30% less than accounting of carbon emissions,which is 500-1 500 tons less per day.In addition,there is a positive correlation between direct monitoring of carbon emissions and boiler output energy,so their changing trends are basically identical,it can also reflect the changes of boiler operating conditions. There is a negative correlation between carbon emissions per unit product and boiler efficiency.On-line monitoring system for CO_2 reported in this manuscript has a good application prospect in fixed source emission enterprises such as cement,ceramics,steel and petrochemical industries and so on. It can significantly improve the enterprise' s level of the carbon emission data management and low-carbon production assessment.Moreover,it can provide a strong support of data and technology for greenhouse gas emission reduction and the operation of carbon emission trading.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 3962K]

Effects of atmosphere on gas-phase arsenic adsorption by oxides and mechanism analysis
HE Ziqian;YU Shenghui;ZHANG Cheng;XU Hao;FANG Qingyan;CHEN Gang;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
Coal combustion is the main way for harmful heavy metal arsenic to enter the atmosphere.It is an effective way to control arsenic emission in-furnace by the adsorption of gaseous arsenic by mineral oxides i. However,coal-fired flue gas contains a large amount of acid gases,including CO_2,HCl,SO_2,etc.,which will combine with mineral oxides,occupy the active site of the sorbents,and thereby reduce the gas-phase arsenic adsorption capacity.In order to understand the effect of acidic gas in flue gas on the adsorption of gaseous arsenic by oxides,some mineral oxides such as Ca O,MgO and Fe_2O_3 were selected as sorbents to carry out gas-phase arsenic adsorption experiments under 700/900 ℃ in simulated flue gas atmosphere.O_2/CO_2 atmosphere and the simulated flue gas containing HCl and SO_2 atmosphere was prepared in a two-stage fixed bed reactor.The arsenic content of the samples was measured by atomic fluorescence spectrometer after extraction with HCl solution,the specific surface area and the pore structure of the adsorbent were analyzed by BET,and the microstructure of the sample was obtained by SEM analysis.The results show that Ca O has the best adsorption effect on gas-phase arsenic,followed by MgO.The arsenic adsorption of Ca O and MgO in the 900 ℃ simulated flue gas is higher than that of 700 ℃,while Fe_2O_3 adsorbs more arsenic at 700 ℃ .In the O_2/CO_2 atmosphere,the amount of arsenic adsorbed by MgO and Ca O is less than that of simulated flue gas,while the capacity of gaseous arsenic adsorbed by Fe_2O_3 is higher than that of simulated flue gas.The effect of acidic gas on arsenic adsorption by oxides is related to the temperature and types of oxides.The O_2/CO_2 atmosphere inhibits the adsorption of gas-phase arsenic by Ca O and MgO,and it promotes Fe_2O_3.HCl in simulated flue gas inhibits the adsorption of gas-phase arsenic by Ca O,and it inhibits the adsorption of gaseous arsenic by MgO and Fe_2O_3 at 700 ℃ and promotes at 900 ℃ .SO_2 in the flue gas inhibites Ca O and MgO,but has no significant effect on Fe_2O_3.CaO,MgO and Fe_2O_3 are mainly chemisorbed by gas-phase arsenic,Fe_2O_3 has the largest specific surface area,but the adsorption is the weakest.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 8949K]

Adsorption research on blue coke-activated carbon modified by organic acid/inorganic acid on coking wastewater
XIN Yingjuan;JIANG Xu;ZHANG Zhao;FENG Weishuai;Research Institute of Energy and Chemical Industry,Xianyang Vocational Technical College;School of Metallurgical Engineering,Xi'an University of Architecture and Technology;
Blue coke is a kind of high-quality and cheap raw material for activated carbon( AC) production because of its high fixed-carbon content,chemical activity,as well as the rich microporous structure of low metamorphic coal.However,the properties of AC prepared by blue coke powder,such as pore structure irregularity,low surface area,disordered pore size distribution,and limited surface chemical properties,limit its application effect,which can be made up by chemical modification.In this paper,the affection of blue coke-activated carbon( BAC) modified by organic acid inorganic acid on the pore structure and the surface chemical properties was investigated. The BAC was modified by nitric acid,phosphoric acid,oxalic acid and acetic acid respectively. By using iodine adsorbed,cryogenic N2 adsorption techniques,scanning electron microscopy( SEM),and Boehm titration,the properties of BAC were studied,and the adsorption of coking wastewater was carried out.The effects of modification on the adsorption behaviors of coking wastewater onto BACs at different temperatures and amount were researched,and the adsorption isotherms experiment has been studied by Langmuir model and Freundlich model.The results show that the active point with high affinity on the surface of the modified activated carbon is enlarged due to the etching of acid,resulting in the decrease of the iodine adsorption value,specific surface area and pore structure parameter.,And because the high active carbon atoms on the edge of activated carbon will combine with oxygen atoms to form oxygen-containing functional groups after being oxidized by acid,the content of oxygen-containing functional groups on the surface will increase,and the stronger the oxidizing acid is,the more oxygen atoms are,and the oxygen-containing functional groups will increase most obviously after nitric acid modification,and the number is2.41 times as many as unmodified. The adsorption test of coking wastewater shows that the adsorption effect of the acid modified activated carbon on coking wastewater is obviously better than that before modification,among which the inorganic acid is better than the organic acid,and the best adsorption effect can be obtained when the nitric acid modification and the COD removal rate increase to 31. 34%at most.This is because the pollutants in coking wastewater are mainly organic pollutants with large molecular weight and molecular diameter,and the acid modification makes the average pore diameter of the activated carbon based on Lancan increase,and the proportion of the medium and large pore increase,which is conducive to the adsorption of the organic pollutants,and the oxygen-containing functional groups added on the surface of the modified activated carbon also improve the hydrophilicity of the pollutants and the affinity to polar organic matters.The isothermal adsorption test shows that when 4 g BAC-N is added into 50 m L coking wastewater in 90 min at 318 K,the COD removal efficiency reaches to 86.79%,and the adsorption process is in accordance with Langmuir model.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 1394K]

Effect of carbon content on the activation of coal gangue and acid leaching for aluminum extraction
CAO Liqiong;ZHANG Lihong;GUO Yanxia;CHENG Fangqin;State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources,Institute of Resources and Environmental Engineering,Shanxi University;
The extraction of alumina from coal gangue is one of the main ways of high value utilization of coal gangue. Thermal activation can effectively stimulate the reaction activity of aluminum bearing minerals in coal gangue and improve the dissolution rate of aluminum in acid leaching process,which is a simple and effective way to activate coal gangue.However,the process is affected by calcination temperature,oxygen concentration,carbon content and other factors.In this paper,the effects of different oxygen concentration and calcination temperature on the efficiency of thermal activated acid leaching of gangue were investigated,and the effects of carbon content in coal gangue and anthracite coal gangue with carbon on the efficiency of thermal activated acid leaching of gangue were studied.The results show that the increasing oxygen concentration( 0-21%) can significantly improve the leaching rate of aluminum from coal gangue after thermal activation.When the oxygen concentration is increased to 21%,that is close to the air atmosphere,the leaching rate of aluminum reaches to 74.24%.However,when the oxygen concentration is increased to 50%,the effect on the leaching rate of aluminum is not significant.In addition,when the calcination temperature is between 600 ℃ and 900 ℃,with the increase of calcination temperature,the alumina leaching rate of coal gangue after calcining presents a trend of first increasing and then decreasing slowly.When the calcination temperature is 700 ℃,the alumina leaching rate reaches to 72.99%.But when the calcination temperature is increased to 900 ℃,the aluminum leaching rate is greatly reduced to 31.77%.Besides,the loss of coal gangue is mainly caused by the combustion of organic matter,such as carbon,which has a certain effect on the leaching rate of activated aluminum.The loss on ignition increases with the increase of oxygen concentration( 0-21%) and calcination temperature. The increase of loss on ignition is propitious to the increase of leaching rate of aluminum,mainly because of the increase of gas released from roasting process and the loosening of coal gangue,which makes the contact between active component and acid more fully,and thus is propitious to the leaching of aluminum. Lastly,the effect of carbon content in coal gangue and coal gangue with carbon on the leaching efficiency of aluminum from coal gangue by thermal activation acid is similar.When the carbon content is less than 23%,the leaching rate of aluminum decreases with the increase of carbon content.But when the carbon content is above 23%,the leaching rate of aluminum increases with the increase of carbon content.
2020 04 v.26;No.128 [Abstract][OnlineView][HTML全文][Download 2992K]

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2020年04期目次

Research progress on chemical-looping combustion and pollutant release for solid fuels

Present situation and development of zero-discharge technology for desulfurization wastewater in coal-fired power plants

Research progress of activated coke flue gas purification reactor

Comprehensiveutilization situation of fly ash in coal-fired power plants and its development suggestions

Research advance on influencing factors and mechanisms of coal selective agglomeration separation process

Research status of coal chemical high-concentrated wastewater treatment and degradation mechanism of characteristic organic pollutants

Progress and perspectives of coking wastewater treatment technology

Study on deashing,desulfurization and upgrading of high sulfur coal by deep-flotation combined with chemical oxidation

Effects of polymer containing wastewater from oil production on preparation and properties of coal water slurry

Numerical simulation of oil residue spray effect by nozzle in pressurized fixed bed slag gasifier

Numerical simulation study on gas-solid fluidization characteristics of the particles with narrow size distribution

Structure analysis of low rank coal and its correlation with pyrolysis tar yield

Study on influencing factors of phenols formation in direct liquefaction of Aiding lignite

Experimental study on catalytic cracking of coal tar by semi-coke

Pore structure control of coal based activated carbon prepared by briquetting method in the presence of FeCl₃

Experimental study on combustion of high alkali coal in horizontal liquid slag cyclone furnace

Experimental study on air-staged combustion of 58 MW pulverized coal industrial boiler

Application ofoxygen-enriched and low NO_x combustion steady technology during flexibility peak-load regulating of 300 MW pulverized coal boiler unit

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Flow field simulation and technology development of integrated dedusting and denitration at high temperature

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Catalytic oxidation NO removal and thermal regeneration experiment by activated coke at low temperature

Research and application of on-line monitoring system for CO₂ emissions from thermal power enterprises

Effects of atmosphere on gas-phase arsenic adsorption by oxides and mechanism analysis

Adsorption research on blue coke-activated carbon modified by organic acid/inorganic acid on coking wastewater

Effect of carbon content on the activation of coal gangue and acid leaching for aluminum extraction