2021年06期目次

  • Mechanism and development trend of desulfurization & denitrification of activated carbon used in flue gas purification

    XIE Wei;LI Xiaoliang;LU Xiaodong;MA Rongfu;WU Qian;WU Tao;LI Long;Beijing Research Institute of Coal Chemistry,CCTEG China Coal Research Institute;State Key Laboratory of Coal Mining and Clean Utilization;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;Activated Carbon Branch,National Energy Group Xinjiang Energy Co.,Ltd.;China Pingmei Shenma Group;

    Based on the characteristics of activated carbon for flue gas purification, the desulfurization and denitrification mechanism of activated carbon was described, and the application fields of activated carbon dry flue gas purification technology were listed, and the key application indexes were combined with laboratory tests. The development trend of activated carbon production technology for flue gas purification was discussed according to the application status and cost analysis of activated carbon for flue gas purification. The analysis shows that the activated carbon dry flue gas purification technology is suitable for the flue gas purification treatment of ore sintering and pellet with large flue gas and complex pollutant composition. The device covers a small area, the process is short and the reliability is high. It is also suitable for the upgrading projects of coking gas treatment with limited sites space, and the operation cost is low. The main advantage of activated carbon flue gas purification technology is that it still has SCR denitrification catalytic activity at low temperature(<200 ℃). However, the low denitrification efficiency becomes one of its main disadvantages in the context of the implementation of ultra-low emission standards. Under the existing application and operation of activated carbon for flue gas purification, it is key to reduce the production cost of activated carbon. Selecting some solid wastes with high carbon content as raw materials, using dry binder molding, carbonization-activation integrated process is the future development trend.

    2021 06 [Abstract][OnlineView][HTML全文][Download 14810K]

  • Research progress and application prospect of coal gasification slag resource utilization

    ZHU Jufen;LI Jian;YAN Long;SHANG Junfei;WANG Yufei;LI Qiang;WANG Jianyou;College of Chemistry and Chemical Engineering,Yulin University;Yulin Kaiyue Coal Chemical Co.,Ltd.,Shaanxi Yanchang Petroleum(Group)Co.,Ltd.;Yulin Solid Waste Recycling Engineering Technology Research Center;Yulin Yushen Industrial Park Management Committee;

    The research introduced the main sources and hazards of coal gasification slag and the physical and chemical properties of coal chemical gasification slag, and discussed status of slag generated by different coal gasification processes(including fixed bed, fluidized bed and entrained flow bed),further discussed the utilization status of coal gasification slag in boiler blending, cement and concrete filler, brick making, adsorption, industrial materials and agriculture and outlooks the application prospects of coal gasification slag. At present, the utilization rate of coal gasification slag is low, the carbon and ash are mutually restricted, boiler blending and the constmction materials are the main utilization way, and the high value utilization is mostly in the laboratory research stage. Boiler blending is the main way to solve the coal gasification slag locally, because of high moisture, low carbon residue and insufficient calorific value, so in practical application need to consider economic benefits and impact on the stability of boiler system.Construction materials is the scale of coal gasification slag elimination path, but the high burn loss of coal gasification slag has exceeded national and industry standards, the residual carbon is inert substance which affects the quality of cement and concrete and bricks.Adsorption in the field of actual engineering may exist water secondary pollution, production technology complexity and high investment risk which still need to be further optimized with the actual production design and test.The preparation of catalyst carrier, rubber and plastic filler, carbon and silicon composites, polyaluminium chloride, ceramic material and other industrial materials is the current research hotspots, with high value-added products, but the high cost and complex process, mostly in the laboratory research stage and need to develop feasible industrial routes to further expand the high-value resource utilization of coal gasification slag and provide technical support for its high-value utilization.The use of coal gasification slag for sand improvement, compost additive and heavy metal degradation has been flourishing, but the risk of heavy metals in coal gasification slag to the environment still needs in-depth research. In order to improve the economic efficiency of enterprises and solve the environmental problems of coal gasification slag, in view of the current situation of coal gasification slag piling and landfill, based on the characteristics of large production of coal gasification slag, abundant carbon aluminum silicon resources, large specific surface area and well-developed pore structure, it is suggested that coal gasification slag grade utilization, and gradually develop simple, feasible and economic benefits of the gasification slag ash separation and utilization technology, moderate development of gasification slag in the ecological field of application, to achieve the harmlessness, reduction and resource of coal gosification slag.

    2021 06 [Abstract][OnlineView][HTML全文][Download 19087K]

  • Research and application progress of coarse gas dust removal technology and equipment

    RU Yi;ZHU Liyun;WANG Zhenbo;HAN Xiao;College of New Energy,China University of Petroleum(East China);Qingdao Special Equipment Inspection and Testing Institute;

    In the production process of crude gas, due to the entrainment effect of air flow, the crude gas contains a large number of solid particles, causing erosion, blockage and even failure of equipment in downstream production units. Meanwhile, the dust of crude gas will also lead to serious air pollution. Gas dust removal technology and equipment on the author to the existing advantages and disadvantages were analyzed, introduced several has a development prospect of fine dust and dust removal technology, higher dust removal efficiency, points out that the agglomeration technology has economy good characteristic, but because of its high energy consumption, secondary pollution, such as short running period faults obviously, at present is still in the laboratory research stage, did not see related industrial application report.Although the high temperature and dry dust removal process such as ceramic base filter and particle bed filter has been industrialized to a certain extent, the dust removal equipment still has the disadvantages of limited operation cycle and high maintenance cost. Based on the analysis of the existing technological problems, it is proposed that the combined pre-agglomeration technology can consider the rational application of various technologies, and the combined composite pre-agglomeration technology can realize the complementary advantages among different technologies, so as to maximize the dust removal efficiency and comprehensive economy of pre-agglomeration technology. The strength, heat resistance, and fatigue resistance of filter materials should be improved for high-temperature dry dust removal, and the operating environment of the dust removal unit should be improved by optimizing the dust removal process. Finally, the potential advantages of several kinds of coarse gas dedusting processes with application prospect were prospected. Some ideas are provided for the research and optimization of coarse gas dedusting processes so as to ensure the efficient recovery and utilization of coarse gas and reduce the “three wastes” emission of energy enterprises.

    2021 06 [Abstract][OnlineView][HTML全文][Download 13340K]

  • Research progress on zero discharge technology of phenol ammonia wastewater produced by pyrolysis of low rank coal

    YANG Xueting;SONG Guoliang;Institute of Engineering Thermophysics,Chinese Academy of Science;University of Chinese Academy of Science;

    In this paper, seven commonly used pyrolytic wastewater treatment technologies were discussed from the aspects of technical principle, advantages and disadvantages, and the feasibility of each technology to treat pyrolytic wastewater was compared and analyzed. When the technical route of "pretreatment—biochemical treatment—advanced treatment—concentrated brine treatment" is adopted to treat pyrolytic wastewater, the effluent can meet the discharge requirements and reuse the water resources. The zero discharge of pyrolytic wastewater can be achieved to a certain extent, which is suitable for the areas lacking water resources. However, the process is complex, and the technical route is highly dependent on microorganisms, while the tolerance of microorganisms to hydrocarbon organics and aminophenol and other toxic substances is limited, which limits their treatment capacity for high concentration pyrolytic wastewater. The thermal treatment technologies destroy the molecular structure of various harmful substances through high-temperature chemical reactions which are not affected by water quality and water temperature. They can oxidize the organic and harmful substances in pyrolytic wastewater into harmless substances CO_2 and H_2O,which truly realizes zero discharge of pyrolytic wastewater. It is a very potential pyrolytic wastewater treatment technology. In this paper, the integrated technology of semi-coke high-temperature post-combustion and collaborative pyrolytic waste water incineration was finally proposed. Coal is first pyrolyzed in a fluidized bed pyrolysis furnace, and the pyrolytic wastewater generated during pyrolysis is sprayed into the combustion furnace under compressed air atomization. The heat released from semi-coke combustion after coal pyrolysis is used to provide heat for high-temperature incineration of pyrolytic wastewater. The reducing atmosphere in the furnace makes the majority of nitrogenous organic matter converted into NH_3,HCN and N_2,and the NO_x concentration produced in the combustion furnace is low. Post-combustion air is sprayed into the high-temperature post-combustion chamber, which can fully burn the unreacted CO and carbon residue in the combustion furnace to ensure the combustion efficiency of the system. The heat of high-temperature flue gas in the post-combustion chamber can generate high-temperature steam for power generation and heating. The integrated technology of high-temperature post-combustion of char and pyrolytic wastewater incineration combines the utilization of low rank coal with high-temperature post-combustion technology, and the advantages of post-combustion technology are used to reduce the emission of pollutants in the combustion process of char and pyrolytic wastewater. The key of this technology is to decompose the organic hazardous substances completely and ensure the original emission of NO_x,SO_2 and other pollutants to meet the standards, which has a broad development prospect. If the conditions of waste liquid incineration are further explored and the amount of waste liquid treated is increased, this technology can be used to treat not only pyrolytic wastewater, but also other industrial wastewater, which can effectively alleviate the problem of waste liquid treatment in China.

    2021 06 [Abstract][OnlineView][HTML全文][Download 16801K]

  • Research status and prospect of preparation and application of coal water slurry

    XU Tong;HE Guofeng;LI Lei;China Coal Research Institute;China Coal Technology & Engineering Group Clean Energy Company Limited Department;

    In Combination with the influencing factors of coal-water slurry preparation, the research status of coal-water slurry preparation, the application status of coal-water slurry as clean fuel and the typical gasification technology of coal-water slurry were reviewed. Combined with the existing problems of coal-water slurry technology, the future development direction of coal-water slurry was prospected. With the shortage of medium-grade metamorphic coal resources and the rise of coal prices, it is very important to broaden the raw coal types of coal water slurry in the industrialization development of coal water slurry. Coal blending and lignite modification can effectively improve the slurry characteristics of low-rank coal, and coal water slurry can realize the reduction, harmlessness and resource utilization of waste by synergistic treatment with waste, which has dual economic and environmental benefits and is in line with the national policy orientation of “increasing efficiency and reducing consumption”. The influence of coal water slurry additives on the properties of slurry is very important, and anionic additives are widely used. The coal water slurry additives developed by using humic acid, lignin and other biomass resources as raw materials have far-reaching significance. Efficient and economical coal water slurry additives to improve the concentration of coal slurry and reduce viscosity have been the research focus of coal water slurry technology. Slurry preparation process is the core of coal water slurry preparation technology. Reasonable slurry preparation process can improve the quality of coal water slurry and reduce the cost of slurry preparation. The core point of different slurry preparation processes is to continuously improve the accumulation efficiency of particles, and to achieve the purpose of coal slurry concentration by improving the particle size distribution, which has become the mainstream technology of low-rank coal concentration. The development of new slurry preparation process should broaden the raw coal type and continuously improve the concentration of coal slurry. At the same time, considering the energy consumption in the process of slurry preparation, the development and research of new slurry preparation process with increasing concentration and reducing consumption is of great significance to the development of coal water slurry technology in the future. As clean fuel, coal-water slurry is mainly used in power plant boilers, industrial boilers, ceramics and other building materials industries. As raw materials of gasification, coal-water slurry is mainly used in the field of coal chemical industry of gasification technology. Common gasification technologies include Texaco gasification technology, multi-nozzle opposed gasification technology and Jinhua boiler gasification technology. In the future, coal-water slurry gasification will develop in the direction of technology autonomy, diversification and large-scale equipment.

    2021 06 [Abstract][OnlineView][HTML全文][Download 14714K]

  • Technical research status and analysis of flotation tailings reselection

    LI Wengxiu;ZHANG Guodong;WANG Dapeng;Institute of Chemical Engineering and Technology,China University of Mining and Technology;

    The washing rate of coking coal has increased obviously, which can ensure its full utilization from the source, and using resource from the flotation tailings has become an important way to fully recover coking coal. But it is difficult to recollect flotation tailings. The methods of flotation tailings reselection in current mainly include oil agglomeration, gravity separation, flotation and combination of gravity separation and flotation, and the technical mode of direct recovery and separation with secondary separation was mainly presented. The oil agglomeration method is suitable for fine coal slime separation. The waste vegetable oil has low cost and environmental friendly, but it has not been widely used. The recovery of flotation tailings coal by heavy separation method is mainly through joint equipment to recover coarse coal slime. The recovered coal ash content is relatively high, so more Chinese coal is mixed into the sales in practical application.The combined method of gravity separation and flotation is mainly used for coarse coal slime and fine coal slime after classification, which can effectively reduce the ash cleaned coal, but the recovery cost is relatively high. Flotation process which involves many factors and therefore recovery of coal flotation tail has more possibilities. It′s helpful to determine the reasonable and efficient recycling method to strengthen the research of flotation tailings surface properties. Ultrasonic, plasma processing coal slime or collectors for reelection flotation tailings provides a new train of thought.

    2021 06 [Abstract][OnlineView][HTML全文][Download 8499K]

  • Research progress of dioxins and heavy metal pollution control technology in MSWI

    CHEN Huaijun;NIU Fang;WANG Naiji;China Coal Research Institute;China Coal Research Institute Company of Energy Conservation;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

    This paper discussed the formation mechanism and control technology of dioxins and the migration mechanism of heavy metals in the process of waste incineration, compared and analyzed the fly ash disposal technology after incineration.The control technology of dioxin and heavy metals in the waste incineration process mainly includes the classification and pretreatment of waste before combustion.The promotion of complete combustion of waste during combustion or the addition of dioxin formation inhibitors can reduce the generation of dioxin.The rapid cooling technology of the flue gas after combustion can avoid the re-generation of dioxins. The emission concentration of dioxins and heavy metals in the flue gas can be reduced by the flue gas purification technology, so that the flue gas can meet the emission standards. The dioxins and heavy metals in the flue gas can be transferred into fly ash, and the final disposal of them is mainly carried out on fly ash. At present, the fly ash disposal technologies reported have been divided into several groups: landfill(direct landfill, solidification and stabilization plus landfill),separation extraction(separation and extraction of heavy metals, water washing treatment),and resource utilization of fly ash(sintered light bone materials and glass ceramics, cement, building material). The solidification stabilization + landfill technology is mature, simple to operate, and relatively low in disposal cost. Among them, chemical stabilization + landfill is one of the main methods of fly ash disposal in China, but this technology has long-term stability of dioxins and heavy metals insufficient, and landfill occupies a large amount of land resources, which is mainly used as a technology for temporary storage of fly ash. Separating/extracting heavy metals and chloride salts from fly ash can realize the utilization of fly ash resources, but the composition and content of heavy metals and soluble salts in garbage, high investment cost and difficulty in subsequent wastewater treatment restrict the application of this technology. At present, large-scale industrial applications have not been realized. Water washing can also remove part of the heavy metals and a large amount of chloride salts in fly ash, and is often used as a pretreatment of fly ash to promote the subsequent utilization of fly ash as a resource. The key to the resource utilization of fly ash is the long-term stability of heavy metals and the thorough degradation of dioxins, and the performance requirements of related products are met, so as to realize the resource utilization of fly ash. High-temperature treatment technology can effectively fix heavy metals and completely decompose dioxins, which is one of the most promising fly ash treatment technologies. However, due to the high investment and operation cost, high energy consumption, and the relatively backward high temperature disposal technology in China, the technology has not been applied on a large scale. Cement kiln co-processing technology directly realizes the resource utilization of fly ash through high temperature solidification, and does not consume more energy. This technology has become the most important fly ash disposal method in China, besides chemical stabilization + landfill. The hydrothermal and mechanochemical methods have lower energy consumption than high-temperature treatment, and are currently still in the experimental research stage.

    2021 06 [Abstract][OnlineView][HTML全文][Download 22129K]

  • Numerical simulation on combustion of a 1000 MW ultra supercritical dual tangential circle boiler

    ZHOU Yaming;WANG Xinyu;HUANG Yaji;GAO Ruibin;JIANG Xinjun;WAN Xu;LIU Yuqian;LIU Xiaodong;DAI Weibao;CHEN Guoqing;CHN Energy Taizhou Power Generation Co.,Ltd.;Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education,Southeast University;Guodian Science and Technology Research Institute Co.,Ltd.;

    In order to explore the combustion law of dual tangential boiler and determine its high-temperature corrosion area, a 1 000 MW ultra supercritical dual tangential coal-fired boiler was taken as the research object, and Fluent software was used to simulate the furnace combustion operation. The velocity field, temperature field, distribution of O_2,CO and NO_x in the furnace were analyzed to explore the combustion characteristics of double tangential boiler. The results show that the simulation results of numerical simulation method are basically consistent with the measured parameters of boiler.There are two symmetrically distributed ellipses in the simulated velocity field, temperature field and gas molar concentration, which conforms to the law of double tangential boiler.The distribution of temperature and average molar concentration of gas along the height direction conforms to the law of low NO_x combustion mode.There are still velocity deviation and temperature deviation in horizontal flue. The velocity and temperature of flue gas are distributed in "M" shape along the furnace width, and the maximum values appear at the furnace width of 12 and 22 m. The velocity deviation and temperature deviation will lead to the thermal load deviation of convective heat exchanger. It is suggested that during boiler retrofit, either the method of increasing the flow rate of deviation pipe or reducing the length of heating pipe can be adopted to prevent the deviation pipe from overheating, and the reverse cutting air technology can also be used to eliminate the residual swirling. Due to the phenomenon of flue gas deflection, the volume fraction of CO in the upstream area of the hot angle is very large, which is higher than 0.1 locally, and may cause high temperature corrosion. It is suggested that the tangential radius should be reduced by changing the incident angle of primary air to prevent the flue gas from brushing the wall. Meanwhile, the wall attached air device can be installed on the water wall to protect the water wall according to the actual corrosion situation.

    2021 06 [Abstract][OnlineView][HTML全文][Download 23304K]

  • Numerical study on the gas-solid uniformity of the four-cycle loop of 660 MW high-efficiency ultra-supercritical CFB boiler

    HAN Ping;ZHANG Dongwang;XIE Guowei;XIN Shengwei;ZHENG Weijia;GU Congyang;ZHANG Man;CHN Energy Guoyuan Electric Power Co.,Ltd.;Department of Energy and Power Engineering,Tsinghua University;School of Energy and Environmental Engineering,University of Science & Technology Beijing;

    Circulating Fluidized Bed(CFB) combustion technology is developing towards higher parameters and larger size, and the number of the separator is increasing accordingly. The structure with multiple separators arranged in parallel can lead to uneven gas-solid distribution and bias flow phenomenon. The uneven flow distribution problem of the separator system under an asymmetric structure is closely related to the structural asymmetry. In order to understand the gas-solid partial flow phenomenon caused by the parallel connection of multiple separators in M-type arrangement of 660 MW high efficiency ultra-supercritical CFB boiler, Eulerian two-fluid model was used to numerically analyze the gas-solid flow characteristics in the thermal circulation loop, and the pressure distribution, furnace chamber and gas-solid flow characteristics in the separator were obtain. The reason for the formation of gas-solid bias flow caused by the parallel connection of multiple separators in M-type arrangement of the ultra-supercritical CFB boiler was analyzed. The simulation results show that the overall pressure distribution of the circulating circuit of circulating fluidized bed presents an oblique "8" distribution, and the pressure distribution of the four circulating circuits in the furnace chamber is basically the same. The gas flow distribution among the four separators is relatively uniform, but the solid flow shows a distribution state of low in the middle and high on both sides. This is related to the location arrangement of the four exit flue windows and the design conditions such as the angle and length of the separator inlet flue. The structural symmetry of the separator is basically the same. However, due to the volatility of the gas-solid flow field in the furnace, the separator is more likely to be under bias flow operating conditions during transient operation, which is not conducive to the separation work. The bed material is distributed more uniformly in the furnace chamber, but the volatility of the gas-solid flow field in the furnace is easy to cause the separator to be in the partial flow condition instantaneously, which is not conducive to the separation work.

    2021 06 [Abstract][OnlineView][HTML全文][Download 11743K]

  • Performance of 350 MW supercritical circulating fluidized bed boiler under different loads

    ZHANG Peng;FAN Haodong;YU Yao;HE Jianping;DU Jiajun;XIN Shengwei;ZHANG Man;YANG Hairui;Shenhua Group CFB Technology R&D Center;College of Electrical and Power Engineering,Taiyuan University of Technology;Deparment of Energy and Power Engineering,Tsinghua University;State Key Laboratory of Power System and Generation Equipment,Tsinghua University;Shenhua Shendong Electric Power Shanxi Hequ Power Generation Co.,Ltd.;

    In order to improve the power generation efficiency of thermal power plants and meet the requirements of clean and efficient utilization of coal, coal-fired boiler units are developing in the direction of large capacity and supercritical parameters. Circulating fluidized bed(CFB) boiler has the advantages of wide fuel adaptability, high efficiency desulfurization, low NO_x emission and wide load regulation range. In recent years, with the successful application of supercritical technology in CFB boiler, supercritical CFB boiler technology perfectly integrates the above two technologies. At present, China has become the largest supercritical CFB boiler Market in the world. More than 40 supercritical CFB boilers have been officially put into commercial operation, of which 350 MW supercritical CFB units have become the main units. In order to meet the requirements of deep peak shaving and ultra-low emission of power grid and ensure the safe, environmental protection and economic operation of CFB boiler, it is necessary to further study the operation performance of units under different loads. The gas-solid flow, heat transfer characteristics, boiler efficiency and pollutant emission law of CFB boiler under different loads were studied on 350 MW unit. The results show that supercritical CFB boiler unit has good load adaptability, and reasonable parameter control such as bed temperature creates favorable conditions for SO_2 and NO_x pollution control.Moreover, when the unit operates in the load range of 80%-90%,its economy is the best. At the same time, in order to take into account the peak load regulation requirements of power grid, it is necessary to conduct more in-depth research on the temperature distribution, load distribution and pollutant control in CFB boiler.

    2021 06 [Abstract][OnlineView][HTML全文][Download 11494K]

  • Influence factors of reductive atmosphere close to water wall of an 1000 MW ultra-supercritical boiler with single chamber and dual tangential

    LIU Tonggan;LIU Xiaodong;HE Lijun;DAI Weibao;KONG Junfeng;CHEN Guoqing;DAI Jiaqi;MA Jiangying;CHN Energy Taizhou Power Generation Co.,Ltd.;Guodian Nanjing Electric Test Research Co.,Ltd.;

    In order to study the influence factors on the atmosphere close to water wall of boiler with single chamber and dual tangential, an ultra-supercritical 1 000 MW boiler with single chamber and dual tangential circle was taken as the research object. Experimental tests were carried out to measure the flue gas composition(O_2,CO and H_2S) in the area close to water wall under different loads and different operational conditions, so as to analyze the effects of unit load, operating oxygen, separated over-fired air(SOFA) flow rate, fineness of pulverized coal on the O_2,CO and H_2S concentration close to water wall. The results show that the areas close to burners 2,3,5 and 8 have the relative stronger reductive atmosphere, so as to called hot corners. The O_2 concentration is basically 0 and the CO concentration is more than 50 000×10~(-6) under medium and high load in the hot corners, which have big possibility of high temperature corrosion. Under low load, different concentration of O_(2 ) can be measured at the hot corners, and the CO concentration is more than 30 000×10~(-6),so that just some local positions have possibility of high temperature corrosion. With the increase of furnace height, the reductive atmosphere gradually increases. The third layer has the strongest reduction of the atmosphere near the wall at the hot angle. The higher the unit load, the stronger the reductive atmosphere. The O_2 concentration reduces and the CO concentration increases rapidly, and the reducing atmosphere increased sharply when the load increases from 50% BRL to 75% BRL. The reductive atmosphere can be decreased to a certain extent through appropriate increase of operating oxygen or regulation of the SOFA rate, for the excess air number becomes bigger. It is benefit of ignition and combustion of pulverized coal with the reducing the fineness of pulverized coal. The volume fraction of CO in the wall atmosphere decreases, which can weaken the reductive strength of the wall atmosphere to a certain extent. Combustion adjustment can alleviate the reducing strength of wall atmosphere, however, the problem of high temperature corrosion can not be solved fundamentally.

    2021 06 [Abstract][OnlineView][HTML全文][Download 11180K]

  • Technical innovation and simulation analysis of swirl low NO_x combustion of a 330 MW thermal power unit boiler

    MENG Tao;KANG Zhizhong;LIANG Shuangrong;CHN Energy Long Yuan Bluesky Energy Conservation Technology Co.,Ltd.;School of Energy,Power and Mechanical Engineering,North China Electric Power University;

    In recent years, China has been vigorously promoting the transformation of ultra-low emissions of coal-fired generating units, and nitrogen oxide emissions in the thermal power industry have been effectively controlled. However, there are still a number of early-stage units that have technical bottlenecks in energy conservation and emission reduction. In order to improve the combustion characteristics of the boiler and reduce the NO_x concentration at the inlet of the SCR system, a 330 MW unit boiler of a power plant has proposed a series of reform plans for boiler pulverizing system, burner structure and arrangement. In order to predict the effect of the retrofit, numerical simulation was carried out based on FLUENT software. Eddy Dissipation Concept(EDC) model considering detailed chemical reactions was used to calculate the combustion process accompanied by the mixed rapid pyrolysis mechanism of pulverized coal and gas heat carrier, including the heterogeneous reduction of NO by coke. By observing the distribution of the flow field, temperature field, O_2 and NO distribution in the furnace, the influence of the modification plan on the various measurement fields and pollutant emissions in the boiler furnace was analyzed. The simulation results show that the specific surface area of fine coal powder increases after the modification of pulverizing system. The rapid pyrolysis reaction conditions are sufficient, and the release rate of volatile is increased, the content of hydrogen components and CO are high. It consumes oxygen and reduces NO production. The change of burner structure and arrangement improves the aerodynamic field in the furnace, the velocity distribution in the furnace is more even. The recirculation zone and reduction zone at the outlet of each layer swirl burner are more obvious, which is conducive to the ignition of pulverized coal flow and reduce the formation of NO_x. The concentration of NO_x at the outlet of the furnace decreases from 552 mg/m~(3 )to 345 mg/m~3 after the modification, which is close to the field test data before and after the reform, and the trend is consistent. Thus, the accuracy of the simulation method and the rationality of the modification scheme is verified.

    2021 06 [Abstract][OnlineView][HTML全文][Download 17658K]

  • Effect of load change of an 1000 MW coal-fired unit on particulate matter emission

    LI Yang;LUO Lin;WU Jianqun;WU Hao;YU Dunxi;Guangdong Yudean Jinghai Power Generation Co.,Ltd.;State Key Laboratory of Coal Combustion,Huazhong University of Science & Technology;

    Revealing the influences of load change on particulate emission from coal-fired units are beneficial to the clean utilization of coal. Particular matter(PM) before and after electrostatic precipitator(ESP)and at the inlet of stack were sampled by low pressure impactor(DLPI) when the operating load of the 1 000 MW ultra-supercritical coal-fired unit varied from 600 MW to 900 MW. The mass concentration of PM in the flue gas was achieved by weighting the mass of PM sample, chemical composition of PM was analyzed by X-ray fluorescence probe(XRF). The rules of PM emission under different operation loads of coal-fired unit were revealed. The results show that the decrease of unit load has insignificant effect on the PM concentration before ESP,but promotes the migration of Na, Ca and S in coal to fine particles(PM_(10)). That can be mainly due to the weaker mineral interaction under lower unit load conditions. It enhances the difficulty of dust removal from the flue gas. The load change has insignificant effect on the dust collection efficiency of ESP,when the unit is in high load(more than 70%). However, dust collection efficiency of ESP decreases when the unit is under low load. The wet desulfurization system and wet electrostatic precipitator(WFGD+WESP) of the unit can further remove the PM in the flue gas effectively. The decrease of unit load increases the duration of flue gas in the WFGD and WESP,and decreases the probability of PM further entrained by flue gas. Therefore, lower operation load of the unit improves the dust collection efficiency of WFGD+WESP. Operation of WFGD and WESP ensures that the concentration of PM from the stack is less than 10 mg/Nm~3 under different operation load conditions.

    2021 06 [Abstract][OnlineView][HTML全文][Download 9021K]

  • Hydrogenation of recycle solvent for direct coal liquefaction

    ZHANG Wei;ZHAO Peng;LIU Min;LI Wenbo;Shendong Coal Group,CHN Enecgy;Beijing Research Institute of Coal Chemistry,CCTEG China Coal Research Institute;State Key Laboratory of Coal Mining and Clean Utilization;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

    For further understanding and process optimization of selected hydrogenation of recycle solvent, heavy oil from 0.1 t/d Bench Scale Unit(BSU)were chosen to carry out the study on selected hydrogenation in 100 mL/h fixed bed reactor. The effect of different parameters on products distribution, recycle solvent properties and structures were reviewed. The Naomaohu coal liquefaction experiments with the hydrogenated solvent were carried out in 500 mL autoclave. The results showed that partial elimination of O,N,S and partial saturation of aromatics occurred with less than 0.2% gas yield and approximate 100% oil yield in hydrogenation system ranging from 360 to 380 ℃. Lower gas hourly space velocity in the conditions of proper temperature, more H_2 enters solvent to change the distribution of aromatics-naphthene-alkane especially the proportion of monocyclic and bicyclic aromatics beneficial to improve H_2 donation properties. The largest amount of alkyl benzene, naphthenic benzene, bicyclic alkylbenzene and highest H_2 donation index in recycle solvent under the conditions of 380 ℃,15 MPa and 1 h~(-1)is beneficial for Naomaohu coal liquefaction to oil. 93% conversion rate and 59% oil yield can be realized under the mild conditions of 400 ℃,17 MPa, 60 min.

    2021 06 [Abstract][OnlineView][HTML全文][Download 10901K]

  • Investigation on the kinetics of pyrolysis reaction of large coal particles based on TGA

    PENG Yangfan;CHEN Shanshan;SUN Fenjin;HU Zhongfa;ZHOU Yuegui;China-UK Low Carbon College,Shanghai Jiao Tong University;Institute of Thermal Energy Engineering,School of Mechanical and Power Engineering,Shanghai Jiao Tong University;Research Institute of Petroleum Exploration and Development;

    Underground Coal Gasification(UCG) is a new mining technology about in-situ gasification of deep coal seams. The pyrolysis and gasification of coal particles with large sizes during the evolution of coal seam cavities is an important part of underground coal gasification. In order to explore the pyrolysis kinetics characteristics of large coal particles, the thermal analyzer(Netzsch STA 449 F3) was used to investigate the effect of heating rates and particle sizes on the pyrolysis characteristics of Inner Mongolia bituminous coal. Under the conditions of test atmosphere N_2,flow rate 100 mL/min and the final temperature is 1 200 ℃,the non-isothermal thermogravimetric analysis was adopted. The characteristic temperatures and the devolatilization index were obtained from the TG/DTG curves at different heating rates and coal particle size. The n-order reaction mechanism function and the Coats-Redfern integration method were adopted for the kinetic analysis to obtain the reaction order, activation energy, and pre-exponential factor. The results show that the initial devolatilization temperature T_i and the maximum mass loss temperature T_(max) of coal particles with large sizes both increase with the increase of the heating rate. T_i increases from 401 ℃ at 5 ℃/min to 425 ℃ at 20 ℃/min, while T_(max) increases from 442 ℃ at 5 ℃/min to 469 ℃ at 20 ℃/min. Besides, the maximum mass loss rate and the devolatilization index increase with the increasing heating rate, enhancing the release of volatiles. The increase of particle size shifts T_i towards higher temperatures, but it has no significant effect on T_(max). The maximum weight loss rate and pyrolysis characteristic index both increase with the increase of coal particle size. The maximum mass loss rate increases slowly from 1.58%/min for the pyrolysis of coal with particle size less than 0.1 mm to 1.85%/min for that with particle size of 0.7-0.8 mm. The devolatilization index increases from 0.54×10~(-6)%~3/(min~2·℃~3) for the pyrolysis of coal with particle size less than 0.1 mm to 0.84×10~(-6) %~3/(min~2·℃~3) for that with particle size of 0.7-0.8 mm. The results of kinetic analysis show that the apparent activation energy for the pyrolysis of coal with large sizes under different cases can be divided into two stages. The apparent activation energy at high temperature zone is much lower than that at low temperature zone, and the reaction orders are both 1.5. The average activation energy decreases from 59.46 kJ/mol at 5 ℃/min to 47.71 kJ/mol at 20 ℃/min, while it increases with the increase of particle size.

    2021 06 [Abstract][OnlineView][HTML全文][Download 8289K]

  • Adjusting method of pyrolysis product distribution of Shendong coal

    CHANG Liang;National Institute of Clean-and-Low Carbon Energy;

    In order to improve the pyrolysis conversion of Shendong coal, adjust the distribution of pyrolysis products, provide data support for industrial plant, the influence of Shendong coal mixed with 15% coal liquefaction residual(DCLR) and 5% olivine respectively on the distribution of pyrolysis products were studied with a 100 kg-level solid heat carrier experimental device. The results show that when Shendong coal is pyrolyzed alone, the char, pyrolysis gas and tar yield are 76.13%,12.97% and 6.19%,respectively, and the light component and heavy component in the tar accounts are 61.89% and 38.11%. When Shendong coal is mixed with 15% DCLR,the char yield is 75.07%,which is 1.39% lower than Shendong coal. The pyrolysis gas yield is reduced by 12.18%,the content of H_2 in gas products increases, and the content of other components decreases.The yield of tar is 8.32%,which is 34.41% higher than Shendong coal. The heavy component in tar is increased to 53.45%,and the quality of tar decreases. When Shendong coal is mixed with 5% olivine, the char yield is 73.90% which is 2.93% lower than Shendong coal.The pyrolysis gas yield is 14.91% which is 14.96% higher than Shendong coal, the CO_2,CH_4 and H_2 content in the gas increase.The tar yield is 5.67% which is 8.40% lower than Shendong coal.The light component in the tar is increased to 70.28%,the heavy component is reduced to 29.72%,and the quality of tar is improved. Through FTIR analysis for three types of char, the absorption peak intensity of functional groups such as ■ in the char of Shendong coal mixed with 15% DCLR is lower than that of Shendong char, O/C and H/C are lower than Shendong char too. In the char of Shendong coal mixed with 5% olivine, the absorption peaks of ■ phenol at 1 220 cm~(-1) basically disappear.The absorption peaks of —CH,—CH_2 and —CH_3 functional group are the smallest among the three types of char, and the O/C and H/C are also the lowest among the three types of char.

    2021 06 [Abstract][OnlineView][HTML全文][Download 10764K]

  • Influence of equivalence ratio of reduction zone on preheating combustion characteristics of pulverized coal

    ZHANG Yi;ZHANG Jiahang;ZHU Jianguo;LIU Jingzhang;Institute of Engineering Thermophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;

    Preheating combustion is a new technology of high temperature preheating modification of pulverized coal and re-combustion of preheated fuel. Based on the 30 kW pulverized coal preheating combustion test apparatus, the influence of the change of the equivalence ratio in the reduction zone on the preheating combustion characteristics of the pulverized coal was researched by basically keeping the operating parameters of the circulating fluidized bed equivalence ratio, preheating temperature, and excess air coefficient unchanged. The results show that the main combustion zone of the downward combustion chamber moves toward the top nozzle, the temperature near the nozzle increases, and the temperature along the downward combustion chamber decreases with the increase of the distance from the nozzle when the equivalence ratio of the reduction zone increases. From the nozzle of the downward combustion chamber to the reducing zone where the tertiary air is fed, it is found that the nitrogen-containing gas mainly exists in the form of NO_2. In the oxidizing zone of the downward combustion chamber after the tertiary air being fed, the nitrogen-containing gas mainly exists in the form of NO. The increase of the equivalence ratio of the reduction zone reduces the CO concentration in the reduction zone of the downward combustion chamber, that is, the reducing atmosphere is weakened. The inhibition effect of low concentration of CO content on NO_2 reduction is weakened, resulting in proportion increase of NO_2 reduced to N_2. The NO_2 concentration in the reduction zone is reduced. The ratio of NO_2 being reduced to N_2 increases. The NO concentration in the oxidizing atmosphere also decreases with the increase of the air equivalence ratio in the reduction zone. It indicates that the form of nitrogen-containing gas in the preheated fuel combustion is closely related to the combustion chamber atmosphere. The generated NO and CO concentrations are both low when the reduction zone equivalence ratio is 0.96.

    2021 06 [Abstract][OnlineView][HTML全文][Download 10174K]

  • Effect of air box structure on aerodynamic field in pre-chamber pulverized coal burner

    CUI Yuhong;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;

    In order to explore the influence of air box structure on the distribution characteristics of airflow and aerodynamic field in the pre-chamber of a 14 MW pre-chamber pulverized coal burner, the numerical calculation method was used to calculate the airflow cooling distribution in the pre-chamber with two different air box structures. By extracting the calculated values of multiple cross-section velocity in the calculation domain, the change rule of velocity distribution of different cross-sections with x/D(dimensionless number of axial distance to diameter) and R/D(dimensionless number of radial distance to diameter) was compared and analyzed. The influence of air box structures on the air distribution characteristics in the precombustion chamber was revealed, and the aerodynamic field in the precombustion chamber pulverized coal burner was optimized. The results show that a strong swirling flow occurs in the pre-chamber pulverized coal burner due to the tangential swirling blades. A recirculation zone is formed in the center of the pre-chamber due to the swirling flow intensity. Under the air box structure of the original and improved, the distribution trend of cross-section airflow velocity is similar. The secondary air velocity presents a low-speed zone in the center of the pre-chamber(R/D=0). The radial distance(R/D) increases the velocity of the air flow to a peak velocity. When the radial distance(R/D) increases further, the velocity decreases gradually, and the velocity near the wall of the pre-chamber(R/D maximum) is slightly lower than the peak velocity. After improving the structure of the air box, the pressure stabilizing capacity of the bellows is further improved, the airflow distribution at the inlet of the tangential swirl blade is more uniform. The peak velocity at the center of the pre-chamber is further improved.

    2021 06 [Abstract][OnlineView][HTML全文][Download 16169K]

  • Experimental study on desulfurization with particle size matched complex agent in CFB boiler

    YU Bin;HAN Lijun;ZHU Yewei;DONG Yanfeng;ZHANG Ruijing;XUE Shouhong;Salaqi Power Plant,Beijing Guodian Electric Power Co.,Ltd.;

    The Circulating Fluidized Bed boiler(CFB)adopts combustion desulfurization in the furnace, which is affected by the influence of calcination characteristics of desulfurizer limestone, pore structure and sintering of calcium oxide, so it is difficult to meet the requirements of environmental protection and ultra-low emission. In order to improve the desulfurization efficiency in the combustion of CFB,The CeO_2-MnO_2-Fe_2O_3 complex was prepared by co-precipitation method, sodium silicate or carboxy methyl cellulose sodium was used as binder. After mixing with high-speed mixer, granulating by rotary granulator and shot blasting by spherical shot blasting machine, the spherical composite with a diameter of 0.8-1.2 mm was obtained. The specific surface area, bulk density and compressive strength of CeO_2-MnO_2-Fe_2O_3 complex were 55-68 m~2/g, 1.80-2.10 g/cm~(3 )and 2.8-3.1 MPa, respectively. The deep desulfurization tests which was mixed with CeO_2-MnO_2-Fe_2O_3 complex, coal, and desulfurizer limestone were proceeded in the combustion of CFB boiler for improving desulfurization efficiency by catalytic oxidation principle. The experimental results show that the concentration of SO_2 in the flue gas is decreased obviously which are compared with the limestone desulfurizer mode after adding CeO_2-MnO_2-Fe_2O_3 composite. The concentration of SO_(2 ) is decreased by 22.1%、22.8% and 19.0% in the combusting temperatures of 850,880,920 ℃ and calcium sulfur ratio of 2.5,respectively compared with the coal and limestone desulfurization conditions, which shows CeO_2-MnO_2-Fe_2O_3 complex has the obvious catalytic effect on the combustion of CFB boiler. The desulfurization efficiency is first increased and then decreased in 920 ℃ because of the inverse decomposition of CaSO_3,the decrease of specific surface area of CeO_(2 )and pore plugging of desulphurization CaSO_4. The concentration of NO_x in the flue gas is little change after the addition of CeO_2-MnO_2-Fe_2O_3. The micro morphology of the combustion ash is massive and irregular, and the ash contains O,Ca, Si, Al, Fe, S,Na, Te and other elements, which is similar to that without composite agent. In addition, the particle size of CeO_2-MnO_2-Fe_2O_(3 )composite agent is matched with that of limestone powder of sulfur fixing agent. During the combustion process, the CeO_2-MnO_2-Fe_2O_3 complex can back to furnace after gas solid separating by cyclone separator. It is good for recycling of CeO_2-MnO_2-Fe_2O_3 complex during CFB combustion.

    2021 06 [Abstract][OnlineView][HTML全文][Download 12593K]

  • Numerical simulation of flow field in gas-liquid downstream desulfurization reactor

    YU Fei;SHI Hanxiang;LIU Changsheng;RAO Wenjun;SHI Yuezhan;YU Yong;School of Aerospace Engineering,Beijing Institute of Technology;Ningbo Taiji Environmental Protection Equipment Co.,Ltd.;

    In order to explore the influence of blades angle on the flow field distribution and energy consumption of desulfurization reactor, the desulfurization reaction device model was established and the flow field in the desulfurization reactor was numerical simulated using computational fluid dynamics software STAR-CCM+. Three-dimensional desulfurization reactor model was established by using STAR-CCM+ software with the k-Epsilon turbulence model and the finite volume method was used to solve the incompressible flow in the reactor. By keeping the structure of the reaction device unchanged, the results of changing conditions were analyzed by only adjusting the installation angle of the blades. By observing the distribution of streamline, fluid velocity and turbulent kinetic energy, and regularities of pressure drop at the different blade installation angles(30°,35°,40°,45°,50°,55°,and 60°),the influence of distribution of gas phase on desulfurization efficiency and energy consumption was analyzed. The results show that the maximum velocity occurs at the blades. The larger the angle, the more disordered the fluid, and the more sufficient the reaction between gas and desulfurization liquid. The disturbance degree in the reactor is ideal when the angle of blades is 60°. The angle increases from 30°to 60°,and the fluid velocity through the blades increases from 16 m/s to 35 m/s. The increase of blades angle increases the maximum value of turbulent kinetic energy, but the distribution range of turbulent kinetic energy is ideal at 30°. The larger the blades angle, the larger the total pressure drop of the desulfurization reactor and the more energy consumption. The pressure drop is minimum at 30°,about 54% of the pressure drop at 60°,which is beneficial to energy saving and increasing economic benefits.

    2021 06 [Abstract][OnlineView][HTML全文][Download 14671K]

  • High temperature corrosion problem of offset cyclone boiler solved by near-wall air and bowl-type air distribution

    YANG Zhen;ZHU Xuaner;HUANG Yaji;YUE Junfeng;WANG Xinyu;ZHANG Qiang;XU Ligang;XIE Ling′ou;Jiangsu Frontier Electric Technology Co.,Ltd.;Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education,Southeast University;Jiangsu Guoxin Yangzhou Power Generation Co.,Ltd.;

    In order to solve the problem of high temperature corrosion, a 650 MW supercritical offset cyclone boiler was used as the research object. In the numerical study, the air volume deviation of the bowl-type air distribution and the near-wall air distribution method were used as variables to explore a synergetic method to solve the problem of high temperature corrosion. The results show that the simulated CO enrichment area of the side wall is basically consistent with the actual corrosion location of the water wall, and the error between the simulated parameters and the measured furnace outlet parameters is less than 5%.Compared with single near-wall air method, the synergetic method has better anti-corrosion effect. When to solve the problem of high-temperature corrosion, the amount of near-wall air can be appropriately reduced. When the total air volume deviation of the bowl-type air distribution increase to 24%,the synergetic method reduce the high-temperature corrosion ratio to below 1%. When the deviation of the total air volume of the bowl-type air distribution reaches 36%,the NO_x mass concentration at the boiler outlet increase significantly. Therefore, in practical engineering applications, the deviation of the total air volume of the bowl-type air distribution should not exceed 24%.

    2021 06 [Abstract][OnlineView][HTML全文][Download 22576K]

  • Partitioning and environmental impact of Hg in desulfurization sludge with different particle diameter

    LI Changhua;CHANG Lin;YU Xuehai;ZHANG Yi;LIU Yi;ZHAO Yongchun;ZHANG Junying;CHN Energy Jiangxi Power Generation Corporation;Shenhua Guohua(Beijing) Electric Power Research Institute Co.,Ltd.;School of Energy and Power Engineering,Huazhong University of Science and Technology;

    Generated from coal combustion, Hg can be found in the products from WFGD system, in particular WFGD sludge. The mineral composition and Hg content were studied by X-Ray diffraction(XRD) and scanning electron microscope energy dispersive X-ray(SEM-EDX) in the present study. The partitioning of Hg species in WFGD sludge with different diameter was investigated by Hg temperature programmed decomposition method(Hg-TPD) in the present study. The results indicate that the Hg content in WFGD sludge is 5.652 μg/g which is much higher than that in gypsum. Hg species including HgS,HgO,and HgSO_4 are identified in the WFGD sludge whose proportions are 47%,49%,and 5%,respectively. The proportions of HgO and HgSO_4 decreases when the particular diameter decreased, while the proportion of HgS increased. The percentage of HgS reached over 80% in the sample of 38 μm. Also, the environmental potential risk is evaluated by applying the standard toxicity characteristic leaching procedure. The results indicate that the particular diameter and the Hg species constitution are the dominant factors that influence Hg leaching ability. The sample 74 μm exhibites the highest environmental potential risk with Hg leaching concentration 3.8 μg/g.

    2021 06 [Abstract][OnlineView][HTML全文][Download 18051K]

  • Experiment on mercury removal in simulated flue gas by injecting halogen modified rice husk coke

    TAO Jun;GU Xiaobing;WANG Hongyu;LU Jincheng;GENG Xinze;LIU Meng;DUAN Yufeng;Datang Environment Industry Group Co.,Ltd.;School of Energy and Environment,Southeast University;

    Coal-fired power plants are one of the main sources of anthropogenic mercury emissions in China. It is very important to find reasonable and effective ways to control mercury emissions. At present, most of the mercury adsorbents are made from activated carbon. It is actually significant to develop low cost high effective biomass cokes in place of activated carbon for mercury removal. Rice husk coke(RHC) was modified with ammonium bromide solution(NH_4Br) by impregnation method, and a brominated adsorbent for mercury removal from rice husk coke(Br-RHC) was prepared. The pore structure of the mercury removal adsorbent before and after modification was analyzed by BET. A test for mercury removal by injecting the Br-RHC adsorbent into a simulated flue gas duct was conducted. The effects of halogen modification, flue gas temperature, adsorbent residence time, inlet mercury concentration, and adsorbent injection amount on the mercury removal efficiency were investigated. The results show that the rice husk coke modified by halogen has an abundant pore structure than before. The BET specific surface area, microporous volume, and total pore volume are greatly improved. The injection mercury removal efficiency of Br-RHC is 3.27-3.75 times higher than that of unmodified RHC. The halogen modification of RHC can significantly improve its injection mercury removal performance. As the inlet, the Hg~0 concentration is 16.7 μg/m~3 and the residence time is 2.03 s, the Hg~0 removal rate reaches the maximum. The effect of flue gas temperature on injection mercury removal efficiency increases first and then decreases, and the best temperature is 120 ℃. When the injection mass amount of Br-RHC is 7.3 g/h, the Hg~0 removal rate reaches 70.62%. The increase of adsorbent injection amount always promotes the efficiency of mercury removal, which finally tends to be stable.

    2021 06 [Abstract][OnlineView][HTML全文][Download 10280K]

  • Development of coal-based hollow-plate carbon membrane and its application in phenolic wastewater treatment

    PAN Zonglin;XU Ruisong;LI Lin;SONG Chengwen;WANG Tonghua;College of Environmental Science and Engineering,Dalian Maritime University;School of Chemical Engineering,Dalian University of Technology;

    The electric field-enhanced coal-based conductive carbon membrane which couples electrochemical oxidation and membrane separation simultaneously exhibits excellent organic wastewater treatment performance. In this work, a novel Hollow-Plate Carbon Membrane(HPCM) was prepared from low-cost coal. The structural performances of HPCM were characterized via SEM,pore size analyzer, four-probe analyzer, FTIR,XRD and Raman Spectrometer. The electrochemical performance of HPCM was evaluated by using an electrochemical workstation. The phenolic wastewater treatment performance of HPCM was also investigated by using typical refractory organic phenol as target pollutant under the enhancement of electrical filed. It is found that the HPCM possesses developed pore structures, and its mean pore width and porosity are 0.71 μm and 47.73%,respectively. The carbon structure of HPCM is consisted mainly of the carbon microcrystallites with relatively low orderliness and it showes a high electrical conductivity and electrochemical activity. The HPCM has a very low removal rate for phenol molecules in wastewater without the assistance of electrical-field. HPCM showes good electrochemical oxidation on phenol under the application of electric filed, and its electrochemical oxidation mechanism includes both direct oxidation and indirect oxidation. The phenol removal rate and COD removal rate of HPCM reach to 98% and 82.15%,respectively, under the optimal operation condition of applied voltage of 2.5 V,phenol concentration of 100 mg/L and flow rate of 5 mL/min. These results show that the HPCM has a good application prospect on the phenolic wastewater treatment.

    2021 06 [Abstract][OnlineView][HTML全文][Download 14459K]

  • Research and engineering application on evaporation technology of FGD wastewater using low-temperature flue gas

    LIAO Shuxin;ZHU Wenyu;TANG Fuquan;ZHENG Wei;MA Shuangchen;Hubei Energy Group Ezhou Power Plant Co.,Ltd.;Chengdu Raise Environmental Technology Co.,Ltd.;North China Electric Power University(Baoding);

    As the technology of evaporation of FGD wastewater using low-temperature flue gas had the cost advantage, the technology attractes the attention of thermal power industry. By the technology researching, the technological conditions not only were determined, but also the key design parameters that it was optimal to select concentrating tower were provided. In the concentrating tower the flue gas velocity was determined to be 3.5 m/s and height of evaporation zone was determined to be 5.8 m. At the same time, two spray layers were arranged in the concentrating tower, each of which was a hollow cone-shaped high-flow silicon carbide nozzle. The flow fields of concentrating tower as core equipment were researched by CFD software. Taken the double phase coupling into account, gas phase and liquid drop respectively were studied by using Euler′s method and Lagrangian′s method. The simulation results are exhibited. Not only do the velocity of flue gas and valid height of tower reasonably design, but also two spray layers and the arrangement of nozzle is reasonably designed. The flow fields between the gas phase and liquid phase are uniformly distributed and the thermal efficiency are high in concentrating tower, which has a performance that there is rational design for concentrating tower. According to the results of simulation and design basis, the demonstration project of evaporation of FGD wastewater using low-temperature flue gas was constructed in Ezhou power plant the third project. During operation, with salt concentration reached saturation, the crystals of salt is precipitated from concentrated solution, which has a phenomenon that concentration ratio could reaches 15 in terms of chloride ions. The project has continued operating 5 000 h, so it is proved that zero liquid discharge of desulfurization wastewater is attained.

    2021 06 [Abstract][OnlineView][HTML全文][Download 9453K]

  • Analysis on position selection of dosing point in slime water treatment

    ZHANG Lei;SHI Yawen;KANG Xuegang;Daliuta Coal Preparation Plant,CHN Energy Shendong Coal Preparation Center;

    In order to avoid no mixing equipment for slime water and reagent due toimproper selection of dosing point location, it is not sufficient to mix slime water and chemicals by gravity flow, which can not give full play to the efficacy. Aiming at the problem that the location of dosing point is more arbitrary, taking the slime water treatment of Daliuta Coal Preparation Plant as an example, the process flow of coal preparation plant was analyzed, the causes of difficult settlement of slime water, the importance of fully mixing slime water and chemicals was clarified. The flow pattern of slime water in the backflow buffer pool and concentration pool was investigated by using the fluid flow state criterion Reynolds number. Through theoretical calculation, the Reynolds number of slime water in the open channel pipeline of the backflow buffer pool is between 503-1 246,and the Reynolds number in the feed submerged pipeline of the concentration pool is between 714-1 886. According to the critical number of Reynolds number turbulent laminar flow transition in open channel and submerged circular pipe, the flow pattern of slime water in the open channel pipeline of slime water reflux buffer pool is turbulent, and the flow state of slime water in the submerged pipeline of concentration pool is laminar flow. The mixing and interference of various parts of slime water in turbulent flow state is conducive to mixing with chemicals, but the laminar flow state is not conducive to the mixing of slime water and chemicals. The position of dosing point should be that the flow pattern of slime water is turbulent flow, but not laminar flow. Finally, it is pointed out that the reasonable position of dosing point is limited, so a mixing tank or box should be set up between the buffer tank and the concentration tank, and the pipeline mixer can also be added to provide a place for the full mixing of coal slime water and chemicals, but the new facilities are required to not only fully mix the slime water agent, but also provide stable feeding for the concentration tank.

    2021 06 [Abstract][OnlineView][HTML全文][Download 6645K]

  • Compulsory defoaming of coal flotation froth by polydimethylsiloxane

    ZHAO Hui;CUI Guangwen;Shaanxi Energy Institute;College of Chemical and Environmental Engineering,Shandong University of Science and Technology;

    The excessively stabilized coal flotation froth is the main reason of the insufficient volume of the flotation clean coal bucket and the low efficiency of clean coal dewatering. It is a useful solution to add defoamer in coal flotation froth as a chemical defoamation method. In this work, polydimethylsiloxane was used as a demoamer in coal flotation froth. The defoamation performance was evaluated via the measurements of three-phase froth stability, pulp viscosity, and solution surface tension under different water hardness. The three-phase froth stability results show that the froth stability first decreases and then increases with the increase of demoamer dosage from 0 to 0.5 g/L,and the defoamation effect is more significant at low water hardness. The pulp viscosity results show that polydimethylsiloxane defoamer can significantly decrease pulp viscosity and again the variation is more profound at low water hardness. The surface tension results indicate that defoamer can decrease the solution surface tension just like frother when it is used solely, but it can increase solution surface tension when frother is present. As a result, the bubble coalescence and bursting can promoted and the froth can destabilized. The work shows that polydimethylsiloxane can work as the defoamer of coal flotation froth, and it can destabilize the flotation froth quickly and improve clean coal dewatering efficiency at low dosage(0.1 g/L).

    2021 06 [Abstract][OnlineView][HTML全文][Download 7163K]

  • Effects of extractant and pretreatment on the structure of humic acid from methane fermentation peat residue

    LU Yanan;MA Litong;School of Chemistry and Chemical Engineering,Inner Mongolia University of Science and Technology;Inner Mongolia Engineering Research Center of Comprehensive Utilization of Bio-coal Chemical Industry;

    Using herbaceous peat as a raw, the humic acids were extracted by alkali-extraction acid-precipitation method from residue after methane fermentation. At the same time, they were extracted by sodium carbonate, sodium bicarbonate, ammonia water, and sodium sulfite, respectively. In addition, the humic acids were characterized by Ultraviolet-visible spectra, Fourier transform infrared spectroscopy, and Fluorescence spectrum. Simple parts of humic acids such as hydroxyl, methylene, and methyl were consumed and utilized by microorganism, while the complex structures such as benzene ring, carbonyl, triple bond and accumulated double bond cannot be consumed and utilized during the methane fermentation process. Furthermore, sodium hydroxide pretreatment can promote this process and produce more methane. Methane production increases by 1.12 times, and the yield of humic acid is significantly reduced after methane fermentation. Extractions with different extractants have an obvious effect on the yield, content and structure of humic acid. Humic acids extracted by sodium carbonate have a higher content, and the content of hydroxyl, methylene, carbonyl, benzene ring, and ether bond is at a higher level. Humic acids extracted by sodium sulfite have a higher yield and contains more triple bonds and accumulated double bonds. The results of the study show that the process of coupling extracting humic acid from herbaceous peat and the process of sodium hydroxide pretreatment methane fermentation is feasible, and it has a certain reference value for realizing high-value utilization of peat.

    2021 06 [Abstract][OnlineView][HTML全文][Download 11821K]

  • Optimization of wet desulfurization limestone feeding system based on critical deposition rate

    GU Xiaobing;NING Xiang;MENG Lei;SHI Hao;XIAO Haiping;Datang Environment Industry Group Co.,Ltd.;School of Energy,Power and Mechanical Engineering,North China Electric Power University;

    During the low-load operation of the wet desulfurization system, the limestone slurry pump is frequently started, which seriously endangers the equipment safety. The minimum non-deposition velocity experiment was conducted to study the critical deposition velocity of limestone slurry, and the slurry supply system was optimized accordingly. The results show that the critical flow velocity gradually increases with the pipe diameter increasing. The critical flow velocity increases from 1.28 m/s at a pipe diameter of 40 mm to 1.76 m/s at a pipe diameter of 70 mm which increases by 37.50%. The critical flow velocity gradually decreases with the decrease of solid content. The critical velocity decreases from 1.42 m/s at a solid content of 20% to 1.06 m/s at a solid content of 4% which decreases by 25.35%. With the change of pipe diameter and solid content, the trend of critical velocity of coarse and fine particles is consistent. The effect of pipe diameter on coarse particles is more obvious, and the effect of solid content on coarse and fine particles is similar. Under the same pipe diameter and solid content, the critical deposition velocity of coarse particles is higher than that of fine particles. The minimum flow is determined according to the critical deposition velocity of limestone slurry and thus wide-load water supply process is developed accordingly. And a low-load water-supply electric regulating valve control scheme is designed to achieve real-time regulation of limestone slurry under different loads. The switching control logic has been successfully applied to engineering to ensure the normal operation of the limestone slurry pump and improve the stability and safety of equipment.

    2021 06 [Abstract][OnlineView][HTML全文][Download 9377K]



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