Clean Coal Technology

2021年03期目次

Research progress of fly ash activation and its application in the porous catalytic materials
LU Qiang;WU Yachang;XU Mingxin;LIU Zishu;ZHANG Pingxin;OUYANG Haodong;National Engineering Laboratory for Biomass Power Generation Equipment,North China Electric Power University;
Fly ash is a momentous industrial solid waste produced in the process of coal combustion,with huge output. The storage of fly ash not only occupies the pile lands,but also causes a series of environmental problems. Currently,fly ash is mainly utilized as the construction materials in China,which has low economic value. The total amount of SiO_2 and Al_2O_3 in fly ash is more than 80%. The preparation of porous catalytic materials from fly ash can realize the resource utilization of high added value of fly ash. However,due to the high thermal stability and poor moldability of the original fly ash,the original fly ash needs to be modified. In this review,the fundamental physical and chemical properties of fly ash were introduced firstly,including the elemental composition,crystal phase structure and particle size distribution. Then,the current modification methods of fly ash were described in detail,including the preparation of catalyst carriers and molecular sieves. Acid modification,alkali modification and plasma modification methods are frequently used in the process of original fly ash direct modification to obtain catalyst carriers. One-step hydrothermal,two-step hydrothermal,alkali fusion-hydrothermal and microwave-assisted hydrothermal are generally used for the preparation of molecular sieves from fly ash. Besides,the application fields of fly ash-based catalysts were briefly introduced,consisting of organic degradation,organic synthesis and inorganic gaseous pollutants removal. Organic degradation mainly includes photocatalytic and non-photocatalytic reactions,and organic synthesis mainly includes catalytic polycondensation and esterification. The inorganic gaseous pollutant removal is mainly about denitration and mercury catalytic oxidation. It is found that fly ash exhibits good developing potential as catalyst carrier materials. However,the conventional modification methods have their own advantages and disadvantages,and the technology is still not mature enough,and some further research is needed. Besides,the modification methods of fly ash need to be optimized according to the actual catalytic requirements. Finally,some suggestions for the developments of fly ash-based catalysts were presented,which could provide acknowledgment for the subsequent high-value utilization of fly ash and the related research of fly ash based catalysts.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3497K]

Research progress on characteristics and comprehensive utilization of calcium carbide slag
ZHAO Liwen;ZHU Ganyu;LI Shaopeng;MENG Ziheng;MU Xiujuan;ZHANG Jianbo;LI Huiquan;XIE Keqiang;Faculty of Metallurgical and Energy Engineering,Kunming University of Science and Technology;National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology,Key Laboratory of Green Process and Engineering,Institute of Process Engineering,Chinese Academy of Sciences;School of Chemistry and Chemical Engineering,University of Jinan;School of Chemical Engineering,University of Chinese Aca
With the continuous development of chlor alkali industry,the discharge and storage of calcium carbide slag are increasing,which results in serious environmental pollution and the waste of land and calcium resources. Based on the analysis of the composition and structural characteristics and the problem of resource utilization of calcium carbide slag,the usage of calcium carbide slag in building materials,chemical materials and environmental protection was analyzed in this paper. In addition,the problems and research trends of comprehensive utilization of resources was vitally discussed. The analysis shows that calcium carbide slag has fine particle size and high reactivity. The traditional large-scale consumption is mainly used to replace limestone to prepare cement and other building materials,but it is limited by domestic market saturation and geographical concentration. Calcium hydroxide is the main component of calcium carbide slag,which can be used to prepare calcium oxide,calcium carbonate and other chemical products. However,due to the influence of impurities in calcium carbide slag,the cost of treatment process is high and secondary pollution is easy to occur. Moreover,calcium carbide slag has strong alkalinity and good ablation performance,and it has excellent performance in the treatment of acidic waste water and flue gas desulfurization. In addition,it will become one of the development directions of comprehensive utilization of calcium carbide slag replace calcium absorbent for flue gas desulfurization. In conclusion,the utilization of calcium carbide slag has significant economic and environmental benefits. But the harmful components and impurities in calcium carbide slag are the main factors limiting the utilization of calcium carbide slag. At the same time,the utilization modes of different regions should be considered according to their regional characteristics and local conditions to achieve the“waste control by waste”objective.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3898K]

Research progress on the preparation of gypsum mortar from desulfurization gypsum with high chlorine content
ZHAO Li;LIU Zishu;XU Mingxin;WANG Hanxiao;WU Yachang;LU Qiang;National Engineering Laboratory for Biomass Power Generation Equipment,North China Electric Power University;
Wet flue gas desulfurization (WFGD) is the key technology for the desulfurization of flue gas in coal-fired power plants,which will produce a large amounts of desulfurization gypsum,and the preparation of green building materials,such as gypsum mortar,is an important way for their high-value utilization. However,due to water recycling in the desulfurization system and the requirement for zero discharge of desulfurization wastewater,the content of chloride ions in desulfurization gypsum is generally high,which seriously restricts the quality of gypsum mortar. Therefore,it has become a current research hotspot to control the chloride ions in desulfurized gypsum in order to suppress its adverse effects on the performance of gypsum mortar products. Firstly,the influence of chloride ions on gypsum mortar was introduced in detail,including the effects of Cl-on the hydration process of gypsum and its performance of water absorption. Then,the current control technology of chloride ions was systematically introduced,including physically adsorbing chloride ions and blocking the channels of chloride ion migration,and chemically converting to the water-insoluble chloroaluminate. In addition,the detailed preparation parameters of gypsum mortar from WFGD gypsum with high chloride ion contents were summarized. When the calcination temperature is 150-180 ℃ and the duration is 1.5-2.5 hours,the obtained gypsum has higher density and lower porosity,which can hinder the migration of chloride ions. Retarder can prolong the setting time of gypsum,but it is not conducive to the control of chloride ions migration. Waterretention agent can improve the water retention of gypsum mortar but will accelerate the migration of chloride ions. Superplasticizer can decrease the water/ash ratio,which can suppress the migration of chloride ions. Water-proofing agent can improve the pore structure of the gypsum,which inhibits the formation of calcium chloride. Finally,the developing trend of gypsum mortar preparation from WFGD gypsum with high chlorine ions was also proposed.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 1632K]

Progress and prospect of research on comprehensive utilization of coal fly ash for preparation of mullite-based materials
GAO Jianming;DU Zongyuan;GUO Yanxia;CHENG Fangqin;State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources,Institute of Resources and Environment Engineering,Shanxi University;National Local Joint Engineering Laboratory for Comprehensive Utilization Technology of Coal Chemical Waste,Institute of Resources and Environment Engineering,Shanxi University;
Coal fly ash is a kind of solid waste generated in the process of coal-fired power. Its massive accumulation not only takes up land resources,but also causes serious environmental pollution and even endangers human health. However,fly ash contains valuable resources such as silica and alumina,especially the high alumina fly ash produced in western Inner Mongolia and northern Shanxi province with the amount of alumina and silicon oxide reaching more than 80%-85%,which has a great prospect of resource utilization. Mullitebased materials are widely used in the fields of metallurgy,catalysis,water treatment,aviation and other fields because of their excellent physical and chemical properties. The preparation of mullite using natural aluminosilicate minerals or high-purity reagents not only consumes a lot of mineral resources,but also has the problem of high production cost. The synthesis of mullite series materials using fly ash as raw material can effectively reduce the consumption of natural minerals,lower production cost and mitigate environmental pollution. Therefore,the preparation of mullite-based materials from coal fly ash is one of the most important ways to realize the high-value resource utilization. Based on the summary of the compositions,properties,synthesis methods and applications of mullite,the research progress on mullite-based materials prepared by comprehensive utilization of coal fly ash was summarized from the perspective of composition,mineral phase regulation for the preparation of coal fly ash-based mullite,its properties and application. In order to achieve the regulation of the structure and performance of fly ash-based mullite series materials and promote the high value and resource utilization of coal fly ash,the current types of mullite series materials synthesized from coal fly ash and their preparation methods were systematically summarized,the aluminum-silica ratio regulation,impurity control in coal fly ash and mullite generation mechanism were analyzed,and the properties of different coal fly ash-based mullite materials and their influencing factors were described.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 10278K]

Recent progress of synthesis and application of fly ash based zeolite
HE Guangyao;WANG Bing;SHI Pengcheng;BAO Weiren;CHANG Liping;HUANG Zhanggen;WANG Jiancheng;HAN Li'na;College of Materials Science and Engineering,Taiyuan University of Technology;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;Key Laboratory of Coal Science and Technology,Ministry of Education,Taiyuan University of Technology;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences;
A large amount of fly ash is produced in the process of coal combustion. The output of fly ash in China ranks the first in the world. Because the comprehensive utilization rate is only 70%,a large amount of fly ash is still in open storage,resulting in serious environmental pollution and waste of resources. It is of great practical significance to eliminate environmental pollution of fly ash and improve its resource utilization for the development of circular economy in China. The utilization of fly ash in China has gradually changed from the early extensive large-scale utilization to the fine high-value utilization. Since fly ash is rich in silicon and aluminum elements,the synthesis of zeolite molecular sieve from fly ash is a research hotspot in the high-value utilization of fly ash in recent years. In this paper,the synthesis and application of fly ash based zeolite from four aspects were discussed. Firstly,the formation,physical and chemical properties,hazards,treatment and utilization status of fly ash were introduced. Fly ash is a mechanical mixture of particles with different mineral compositions and forms. Its properties are related to the composition,origin and combustion mode of raw coal. The characteristics of fly ash are the key to its comprehensive utilization. Secondly,three main activation methods of fly ash were discussed,including mechanical activation,hydrothermal activation and alkali (salt) melting activation. Silicon and aluminum in fly ash mainly exist in the form of amorphous mineral vitreous,and its surface is a dense glass shell. The key problem in the synthesis of zeolite molecular sieve by fly ash is how to make silicon and aluminum fully activated and effectively utilized. Compared with mechanical grinding activation and alkali (salt) melting activation,hydrothermal activation has higher activation efficiency and lower energy consumption. In the third part,the hydrothermal synthesis methods of fly ash based zeolite were discussed. The direct hydrothermal synthesis method,alkali fusion hydrothermal synthesis method,microwave/ultrasonic hydrothermal synthesis method,crystal seed method and crystal transformation method were mainly introduced. The synthesis of zeolite from fly ash is generally based on hydrothermal synthesis process. The purity of the product can be improved by multi step hydrothermal treatment. the yield,crystallization rate and crystallinity can be improved by ultrasonic,microwave,alkali melting and seed addition. The interzeolite conversion method can greatly expand the framework type and acid sites of fly ash based zeolite,which is a more favorable preparation technology of fly ash based zeolite. Finally,the application of fly ash based zeolite was summarized. The application of fly ash based zeolite is still in the exploratory stage,which is mainly used in the field of environmental treatment,including the adsorption and removal of heavy metal ions in industrial wastewater,the adsorption and removal of air pollutants and the adsorption of greenhouse gas CO2.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 8914K]

Characteristic analysis and utilization of coal gasification fine slag based on particle size classification
WANG Xuebin;YU Wei;ZHANG Tao;BAI Yonghui;LIU Lijun;SHI Zhaochen;YIN Rui;TAN Houzhang;School of Energy and Power Engineering,Xi'an Jiaotong University;School of Chemistry and Chemical Engineering,Xi'an University of Science and Technology;Yantai Longyuan Power Technology Co.,Ltd.;State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering,College of Chemistry and Chemical Engineering,Ningxia University;Beijing ENSA Engineering Co.,Ltd.;
A large amount of gasification fine slag with high carbon content is produced in the process of coal gasification. At present,it is mainly treated by landfill,which not only occupies a lot of land,pollutes soil and water,but also causes energy waste. How to efficiently and environmentally utilize gasification fine slag as a resource is the hot spot of current research. The separation of residual carbon and ash in gasification fine slag is the key to realize its high value,reduction and harmless utilization. The analysis of particle size characteristics of gasification fine slag shows that the ash content of each particle size increases with the decrease of particle size,and the separation and enrichment of carbon and ash can be realized by screening and classification process. The results show that the fixed carbon content of Yulin coal gasification fine slag decreases with the decrease of particle size. There are more SiO_2,Al_2O_3,Fe_2O_3 and Ca O in each particle size.The micro morphology is mainly composed of porous matrix,irregular small particles,flocculent particles and spherical particles. The results show that the pore structure of coal gasification fine slag is developed,the specific surface area is rich,and the products with particle size >75 μm can be directly used as high-quality adsorption materials. Compared with the gasification fuel coal,the combustion characteristic temperature of each particle size of coal gasification fine slag is significantly increased,and the ignition characteristic temperature is higher than that of anthracite except for <45 μm particles. Due to the existence of rich porosity in gasification slag,the contact area between particles and oxygen is increased,so that the peak combustion temperature of combustion is lower than that of anthracite and the burnout temperature is significantly lower than that of anthracite in middle and later stage of combustion.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 6617K]

Fuel-N transformation and NO_x emission characteristics of coal gasification fly ash during preheating process in the flameless combustion mode
DING Hongliang;OUYANG Ziqu;School of Engineering Science,University of Chinese Academy of Sciences;Institute of Engineering Thermophysics,Chinese Academy of Sciences;
To achieve the clean and efficient utilization of the coal gasification fly ash,experimental studies which adopted advanced selfpreheating combustion technology were carried out on a 30 kW preheating flameless combustion test rig for solid carbon-based fuel. FuelN transformation and NO_x emission characteristics from fine ash of bituminous coal gasification fly ash under different preheating temperatures and primary air equivalence ratio were discussed. The results show that the coal gasification fly ash can achieve stable flameless combustion on this experimental system. The combustion characteristics of coal gasification fly ash are greatly improved after preheating. Almost all volatile-N is removed in advance under the strong reducing atmosphere in the self-preheated burner,and is mainly converted to three nitrogen-containing substances: N_2,NH_3 and HCN. Thus char-N is the main source of NO_x emission in subsequent combustion. During the preheating progress,preheating temperature has an obvious effect on the conversion of fuel-N to N_2,while the primary air equivalence ratio mainly affects the conversion rate of fuel-N to N_2,NH_3 and the nitrogen precipitation from char-N. The effects of preheating temperature and primary air equivalence ratio of preheated burner on NO_x emission concentration and conversion rate of fuel-N to NO_x are obviously different. The concentration of NO_x emission and conversion rate of fuel-N to NO_x both reach the lowest value when the preheating temperature is 902 ℃ and the primary air equivalence ratio of preheated burner is 0.45,which are 83.02 mg/m~3 (6% O_2) and 5.94%,respectively.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 5731K]

Experimental study on decarbonization of coal gasification fine slag by flotation
YU Wei;WANG Xuebin;BAI Yonghui;LIU Lijun;SHI Zhaochen;ZHAO Yuxuan;TAN Houzhang;School of Energy and Power Engineering,Xi'an Jiaotong University;School of Chemistry and Chemical Engineering,Xi'an University of Science and Technology;State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering,College of Chemistry and Chemical Engineering,Ningxia University;
Coal gasification fine slag is a solid waste produced in the process of coal gasification. At present,it is mainly treated by landfill.However,due to its high carbon content,it still has certain utilization value. Carbon and ash separation is the key to realize its reduction and resource utilization. Taking coal gasification fine slag in Yulin as the research object,the decarbonization test was carried out by flotation method. Based on the analysis of basic characteristics,the influence of different flotation conditions and processes on separation effect was studied. When the amount of diesel oil is 14 kg/t and the amount of sec-octyl alcohol is 14 kg/t,the ash content of concentrate product is 37.88%,the ash content of tailings product is 51.65%,and the combustible recovery is 51.99% after roughing separation. The concentrate ash content of 18.87% and the yield of 20.30% can be obtained by one roughing one cleaning and one scavenging flotation process when the amount of diesel oil is 14 kg/t in roughing and the amount of diesel oil is 7 kg/t in scavenging. The final calculation shows that the concentrate yield is 41.76%,the ash content is 27.92%,and the combustible recovery is 55.08%. The carbon and ash in the coal gasification fine slag is well separated by one roughing one cleaning and one scavenging flotation process,but the flotation reagent consumption is too high,and the fine materials are more likely to float up into concentrate products in the roughing process. The addition of reagent in the scavenging process can make the coarse materials float up effectively,resulting in the phenomenon that the ash content of the scavenging concentrate is lower than that of the cleaning concentrate. The surface morphology analysis,pore structure analysis,surface functional groups analysis and float and sink analysis of coal gasification fine slag samples show that the samples with large specific surface area and developed pore structure are easy to absorb a large amount of reagents,resulting in excessive consumption of flotation reagents and poor economy.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 6041K]

Design and operation of a 100 t/d gasification fly ash boiler
MAN Chengbo;ZHU Jianguo;LYU Qinggang;OUYANG Ziqu;LIU Jingzhang;Institute of Engineering Thermophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;
Coal gasification technology is one of the main ways of coal cascade utilization,which develops rapidly and is widely used recently. However,the coal gasification process is not able to convert all the carbon in the coal,and some combustibles remain in the gasification fly ash after coal gasification. The gasification fly ash produced by circulating fluidized bed (CFB) coal gasification usually has high carbon content,and its low calorific value can reach 12-25 MJ/kg. The high-efficient combustion of gasification fly ash powders can improve the coal utilization rate. However,gasification fly ash powder can be hardly burned by the conventional combustion technologies due to its low volatile content. In order to realize efficient combustion of gasification fly ash and control NO_x emission,the technical route of combustion with fuel preheating was put forward and developed. The gasification fly ash powders are first preheated to 850-950 ℃ in a CFB,and then the resulting fuel gas and char particles are burned out in the furnace. In addition,the reaction conditions of high temperature and anoxia are conducive to the removal of fuel nitrogen in the preheated burner,so that the NO_x emission can also be realized with staged air distribution in the furnace. In this study,several commissioning and engineering tests were carried out for a boiler with preheating combustion technology of gasification fly ash. The preheating characteristics of gasification fly ash,combustion characteristics and NO_x emission characteristics of high temperature gas-solid mixture fuel were studied by investigating the temperature distribution and variation in preheating burner and furnace,combustion efficiency and original NO_x emission of gasification fly ash. The results show the gasification fly ash with volatile below 3% could be preheated and burnt out stably. The combustion efficiency can reach 98% and the original NO_x emission can achieve the lowest concentration of 261.94 mg/m~3,and the ultra-low emission can be achieved after denitration treatment.The high efficiency and low nitrogen combustion of gasification fly ash is realized by preheating and burning boiler,and the feasibility and advantage of preheating combustion technology in ultra-low volatile fuel treatment are proved.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 2431K]

Research on physicochemical characteristics of fine slag from gasification in Northwest China
WANG Wenyu;LI Wei;LIANG Chen;REN Qiangqiang;Institute of Engineering Thermophysics,Chinese Academy of Science;University of Chinese Academy of Science;Dalian National Laboratory For Clean Energy,Chinese Academy of Science;
Fine slag from gasification is a coal-based solid waste product,which is precipitated by black water after the coarse gas at the outlet of entrained flow gasifier is washed. There is no large-scale resource disposal plan. In order to develop efficient decarbonization technology of fine slag from gasification,the chemical composition,particle size,micro morphology,pore structure,particle size,pore size and pore size of three kinds of entrained bed coal gasification fine ash (DSG,HL,SH) in Northwest China were analyzed by using laser granulometer,elemental analyzer,scanning electron microscope and energy spectrometer,X-ray diffractometer,X-ray fluorescence spectrometer,BET specific surface area analyzer,thermogravimetric analyzer and other analysis equipment. The results show that the moisture content of gasification fine ash is higher than 40% and the calorific value is lower than 10 MJ/kg. The poor pore structure and the existence of molten slag layer on the surface lead to the low reactivity of fine slag from gasification. In thermogravimetric analysis,the weight loss rates of DSG,HL and SH are 13%,29% and 17%,respectively. Compared with the original residual carbon of 16%,37% and 48% in the three kinds of fine slag from gasification,the residual carbon consumptions of DSG,HL and SH are 81%,78% and 35%,respectively.When the oxygen concentration increases from 21% to 30%,the sample reactivity is improved to a certain extent. At present,the conventional combustion decarburization technology cannot realize the efficient decarburization of fine slag from gasification. Therefore,the new combustion decarburization technology should be developed to provide support for the resource utilization of fine slag from gasification.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3543K]

Analysis and research on basic physical properties of gasification slag in representative areas of Sinopec
YANG Hongquan;SUN Zhigang;QU Jiangshan;ZENG Xiansong;ZHANG Jianbo;LI Shaopeng;LI Huiquan;Sinopec Ningbo Technology Research Institute Co.,Ltd.;Key Laboratory of Green Process and Engineering,Institute of Process Engineering,Chinese Academy of Science;National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology;University of Chinese Academy of Science;
With the continuous development and upgrading of high-value conversion technologies for coal resources,gasification slag has a huge annual output and causes serious pollution to the environment as an important solid waste produced in China in recent years. In view of the resource characteristics of gasification slag,it is currently mainly used to prepare low-end building materials and high-end ceramics and other aluminum-silicon composite materials. However,the market for construction and building materials utilization has become increasingly saturated with the improvement of Chinese infrastructure construction,so the high-value conversion and utilization of slag has become a current main research hotspot. However,due to the lack of knowledge about the stability and occurrence of the element/material composition of the gasification slag,the preparation of most composite materials is currently in the laboratory research stage,which is not enough to realize industrial production. In response to the above problems,gasification slag from four different regions was selected as the raw material for this article,and the element composition,material composition,micro morphology and element occurrence forms of fine slag/coarse slag in different regions were studied. It can be seen that the gasification slag is mainly composed of aluminosilicate glass (≈40%) and amorphous carbon particles (5%-50%). The total content of aluminum and silicon is about 40%,and the content of iron and calcium is 20%-40%; Most of the calcium and iron form a eutectic with it,and only a small amount of calcium and iron exist alone.The main difference between the fine slag and the coarse slag is that the content of carbon in coarse slag (5%-20%) is lower than that in fine slag (20%-50%),the carbon content of fine slag is higher,and the glass phase reactivity is higher than that of the fine slag.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 2854K]

Research on preparation and adsorption properties of ammonia nitrogen sorbent based on coal gasification slag
MA Chao;WANG Bing;FAN Panpan;YAN Xiaohui;BAO Weiren;CHANG Liping;WANG Jiancheng;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;Key Laboratory of Coal Science and Technology,Ministry of Education,Taiyuan University of Technology;China Energy Investment Group Co.,Ltd.;
The high content of ammonia nitrogen in water will lead to “bloom”,“red tide”and other phenomena,destroy the ecological balance. In order to realize the efficient removal of ammonia nitrogen from industrial and domestic wastewater,the coal gasification based ammonia nitrogen adsorbent was prepared by using the product of rich carbon slag (RCS) from the bulk coal gasification slag separated by a water-medium cyclone,and its ammonia nitrogen adsorption performance was studied. The physical adsorption results show that the specific surface area of the adsorbent is 311 m~2/g. The structure of the adsorbent was characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM) and Fourier transform infrared absorption (FT-IR) spectroscopy. Relatively regular zeolite A and SAPO-20 molecular sieve heterocrystals were formed After the RCS hydrothermal treatment. Ammonia nitrogen adsorption experiments show that when the adsorbent solid-liquid ratio is 10 g/L,the initial pH value of the solution is 6.8,the initial ammonia concentration is 60.0 mg/L,and the contact time is 1 min,the equilibrium adsorption capacity of the adsorbent for ammonia nitrogen is 3.5 mg/g,and the removal rate reaches 51.0%. However,under the same conditions,the removal rate of ammonia nitrogen by RCS is only 8.1%. The adsorption isotherm of ammonia nitrogen by adsorbents conforms to Freundlich equation,and the adsorption behavior of ammonia nitrogen by adsorbents conforms to the quasi-first-order kinetic equation.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 2714K]

Experimental study on fluidized modification and regasification of gasification fly ash
LIANG Chen;CHU Fuhao;REN Qiangqiang;WANG Xiaofang;Institute of Engineering Thermophysics,Chinese Academy of Sciences;School of Engineering Science,University of Chinese Academy of Sciences;
With the rise of coal chemical technology,the resource treatment of coal gasification fly ash has become an urgent problem.The gasification fly ash from commercial fluidized bed gasifier was tested on 15 kg/h modified gasification test rig to study the effects of fluidization modification on the morphological properties and ash fusibility of gasification fly ash and the regasification characters of modified fly ash. The results show that the regasification of gasification fly ash at 1 200 ℃ can be achieved by fluidized modification. After the fluidized modification,the total pore volume and specific surface area of fly ash are improved because the crack and gasification reactions of residual carbon have the effect of cleaning and promoting the formation of pores. The pore characteristics of modified fly ash can be further improved with the increase of steam and oxygen concentration of modification gasifying agent. On the other hand,after the fluidized modification of gasification fly ash,due to the transformation of high melting point component of the ash minerals into anhydrite with low melting point,the ash fusion temperatures of gasification fly ash decrease,the viscosity-temperature curve becomes smoother and the temperature of critical viscosity reduces. Compared with the fluidized modification at 900 ℃,the modified fly ash is obviously gasified by water gas reaction in the down-flow gasifier at 1 200 ℃,and the yield of effective gas CO+H_2 increases to 0.29 m~3/kg and the system carbon conversion increases to 71.2%.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3709K]

Experimental research on pyrolysis products of single oil shale particle
FENG Weiqiang;BAI Ruiqi;FENG Yupeng;YAO Xuan;ZHANG Man;HUANG Yiqun;YANG Hairui;Beijing Guodian Longyuan Environmental Engineering Co.,Ltd.;State Key Laboratory of Power Systems,Department of Energy and Power Engineering,Tsinghua University;
Oil shale is an important unconventional oil and gas resources in China. Its development and utilization is of great significance to alleviate the problem of energy shortage in China. Due to the high ash content of oil shale,the mass transfer resistanceof gaseous matter against the intraparticle is quite high,which has significant effects on the distribution of pyrolysis products of oil shale. In this paper,a pyrolysis experimental system for single particle oil shale was built to study the influence of mass transfer resistance of ash layer on pyrolysis characteristics of single particle oil shale,which can provide a more essential understanding of the pyrolysis process of oil shale and provide a basis for the construction of pyrolysis model. The effects of particle size,pyrolysis temperature and other factors on the distribution of pyrolysis products were studied,and the distribution of pyrolysis products of single grain oil shale with different gas flow rates,particle sizes and pyrolysis temperatures was obtained. It is found that gas flow rate has little effect on the distribution of pyrolysis products of oil shale particles. With the particle size increasing,more secondary pyrolysis reactions happens before the primary pyrolysis products are separated out. Part of the pyrolysis products are fixed in the semi coke again through the complex secondary pyrolysis reaction,which leads to the decrease of shale oil proportion and the increase of gas proportion in the products.The larger the particle size is,the more obvious the secondary pyrolysis reaction is at higher temperatures. As a result,the proportion of shale oil in the pyrolysis products of coarse particles increases first and then decreases with the increase of pyrolysis temperature,while the proportion of shale oil in the pyrolysis products of fine particles increases with the increase of pyrolysis temperature.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 2391K]

Research progress of nickel-based catalysts for carbon dioxide reforming of methane
WU Xingliang;LYU Linghui;MA Qingxiang;ZENG Chunyang;ZHAO Tiansheng;State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University;China petroleum and Chemical Industry Federation;
Carbon dioxide reforming of methane is an effective way for the resource utilization of green house gases such as carbon dioxide and methane. In recent years,there has been an increasing interest in the development of the reaction catalysts,especially for nickel-based catalysts.In order to understand the utilization of the reaction and the nickel-based catalysts comprehensively,the thermodynamic research and mechanism of this reaction were introduced; the causes of the carbon deposition and ways of carbon elimination on nickel-based catalysts were analyzed; the influence of supports,promoters and preparation methods of nickel based catalysts on the catalytic performance were discussed. Finally,the prospects for the future research directions of nickel-based catalysts were finally proposed. The thermodynamic results show that high temperature and low pressure are beneficial to the reaction; there is no uniform conclusion on the mechanism of the carbon dioxide reforming of methane,since the mechanisms are also different with different catalysts; the coke deposition over the nickel-based catalysts is mainly produced by methane decomposition,CO disproportionation reaction and CO redox reaction,and carbon deposition can be inhibited by adjusting the properties of catalyst in the reaction; the various properties of support,the type of promoter,and the preparation method have different effects on the nickel-based catalysts; there is still a long way for industrial applications of nickel-based catalysts,and in the future development,the preparation conditions of catalyst can be optimized; the carbon deposition mechanism can be deeply explored; theory and practice can be combined to further explore the performance of nickel-based catalysts.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 2339K]

Application of electro-adsorption technology in wastewater treatment of electric power industry
XU Yongyi;YANG Dingchang;WANG Feng;LIU Chang;MA Lan;XING Haoruo;CUI Lingxiao;MA Shuangchen;China Power Hua Chuang Electricity Technology Research Company Ltd.;Department of Environmental Science and Engineering,North China Electric Power University;University of Illinois at Urbana-Champaign;
Traditional water treatment technology is still faced with many problems,such as complex system,high operating cost,easy scaling and corrosion. Therefore,it is necessary to adopt an integrated multi-functional coupling system,which can take into account the functions of desalination and anti-scaling to remove the pollutants in the wastewater. Electro-sorption technology is a new water treatment technology for water purification and desalination,which can effectively remove impurity ions from water without scaling under the premise of low energy consumption. In this paper,it was summarized the development history of electro-sorption theory,the principle of electro-sorption and the main points of electric double layer theory,the structure of electro-sorption and its working process,etc. At the same time,several main electro-sorption materials and their advantages and disadvantages were introduced. Based on increasingly strict environmental protection requirements,electro-sorption technology is expected to be widely used and developed in the power industry due to its technical advantages such as low energy consumption,low cost and no secondary pollution.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 2583K]

Study on the influence of mixed pulverization of two single coals on the mineral distribution in coal blends
WU Suozhen;WANG Qingsong;CHENG Jianlin;GAO Tong;YANG Yunfei;ZHANG Hong;Jiangsu Fangtian Electric Power Technology Co.,Ltd.;School of Chemical Engineering,China University of Mining and Technology;
The mineral distribution in pulverized coal directly affects the fouling and slagging of furnace and the formation of particulate matter. In this paper,the influence of mixed pulverization of two single coals on mineral distribution in coal blends was studied. Zhundong raw coal and Jincheng raw coals were crushed to below 3 mm,respectively,mixed and ground to less than 150 μm according to the mass ratio of 70 ∶ 30,50 ∶ 50,30 ∶ 70. The float-sink method with organic solutions was used to separate the pulverized raw coals and coal blends into different density fractions. The changes in density fraction,volatile matter content,maceral composition and chemical composition of coal ash were studied. It is found that the two single coals have strong interaction during mixed pulverization. The density composition of the coal blends is obviously different from the averaged ones of the two single pulverized coals. The density fractions,<1.5 g/cm~3 and>1.7 g/cm~3,in the three blended coals decrease,while the 1.5-1.6 g/cm~3 fraction significantly increases during mixed pulverization. Both volatile matter contents and microscopic observations indicate that Jincheng coal is concentrated in the <1.5 g/cm~3 fraction of the coal blends,and Zhundong coal is mainly concentrated in the 1. 6-1. 7 g/cm~3 fraction. The chemical compositions of the blend coal ashes are more uniform in different density grades compared with the two kinds of single coals. Mechanism analysis indicates that the different grindability of the two kinds of single coal is the fundamental reason for the segregation of pulverized coal composition.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 5350K]

Study on the co-pyrolysis interaction of Hulunbeier coal and three hydrogen-rich organic compounds
HE Wenjing;ZHANG Lanjun;ZHAO Yibo;ZHU Fei;ZHANG Shengxiang;School of Chemical Engineering,Jiangsu Ocean University;Jiangsu Key Laboratory of Marine Biotechnology,Jiangsu Ocean University;
In this paper,the Hulunbuir coal and three hydrogen-rich organic compounds (cellulose,polyvinyl pyrrolidone (PVP),and high-density polyethylene (HDPE)) were used as raw materials to investigate the behaviors of thermogravimetric,the changes of free radical concentration,and the changes of the yield of pyrolysis products on the fixed bed of the co-pyrolysis process and compare with the results of single pyrolysis. The interaction of free radical fragments produced by pyrolysis of different raw materials during the co-pyrolysis was analyzed. The results show that the weight loss of co-pyrolysis of coal/cellulose,coal/PVP,and coal/HDPE at 150-600 ℃ are 61.18%,60.26%,and 64.31% respectively,which are all lower than the calculated values of 62. 55%,63. 53%,and 66. 76%; When the temperature is higher than 400 ℃,the experimental value of free radical concentrations in the co-pyrolysis process are all lower than the calculated value (an average of individual pyrolysis results); According to fixed-bed pyrolysis results,the solid yields are 37. 9%,39.0%,and 34.0%,respectively,which are equal to or slightly higher than the calculated values (37.5%,36.5%,and 33.6%),the liquid (including water and tar) yields are 33.3%,44.9%,and 53.2% respectively,which are all lower than the corresponding calculated values (39.8%,51.3%,and 57.1%),and the gas yield are 28.8%,16.1%,and 12.9%,which are all higher than the calculated values (22.7%,12.2%,and 9.3%). During the co-pyrolysis process,the free radical fragments generated from different raw materials will interact with each other in the process of escaping from the bed. Among them,the combination of volatile free radicals and stable free radicals is the most important. The resistance of volatile free radicals increases,leading to an increase of the secondary reaction of the volatiles.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3967K]

Study on hydrogen migration and distribution during co-pyrolysis of lignite and rice husk
HE Peihong;HUANG Sheng;WU Youqing;WU Shiyong;Guodian Changyuan Hubei Biomass Gasification Technology Co.,Ltd.;School of Resources and Environmental Engineering,East China University of Science and Technology;
In order to clarify the effect of hydrogen-rich material on the yield and quality of tar from low rank coal pyrolysis and to elucidate the interaction mechanism during co-pyrolyis of low rank coal and hydrogen-rich material,Xilinhot lignite (XL) and rice husk (DK)were used as raw materials for low-temperature co-pyrolysis in an aluminium retort in this study. Hydrogen migration and distribution during co-pyrolysis of XL and DK were studied by comparing the experimental and theoretical values of yield of individual pyrolysis and copyrolysis products and the hydrogen content in pyrolysis products. Results show that there is a synergistic effect between XL and DK in copyrolysis process,the methoxy groups of lignin in DK combine with the free radicals released from XL,which increases the contents of phenolics containing with methoxy groups in co-pyrolysis tar. The co-pyrolysis of XL and DK has a positive synergistic effect on the formation of water and gaseous products. Compared with theoretical value,the hydrogen contents transferred to water and gaseous products increase 1.22%-3.33% and 1.16%-2.39%,respectively. While the hydrogen content transferred to tar decreases 1.00%-3.53%. AAEMs in DK not only intensify the secondary cracking of tar from DK,but also promote the secondary cracking of tar from XL,leading to the increase of C_2-C_4 hydrocarbon yield in gaseous products and the transfer of hydrogen from tar to gas.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3955K]

Fragmentation/pulverization characteristics of Inner Mongolia lignite during pyrolysis
ZHOU Qi;Coal Chemistry Branch,China Coal Research Institute;State Key Laboratory of Coal Mining and Clean Utilization;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;
In order to reveal the fragmentation/pulverization characteristics of Inner Mongolia lignite (X-L and B-L) during pyrolysis,the characterization index of particle fragmentation/pulverization was proposed. The effects of different pyrolysis conditions on particle fragmentation/pulverization were investigated by using laboratory fixed bed and fluidized bed experimental device. The results show that the particle size change rate and pulverization rate are 6.83% and 2.95% respectively under the separate thermal loading mode,and 2.72% and 1.54% respectively under separate mechanical force loading mode. Therefore,the particle size change rate and pulverization rate under the separate thermal loading method are higher than those under the separate mechanical force loading method. The total pore volume of the particles under the single thermal loading method is 4.34 times of that of raw coal,and the volumes of macropores and mesopores are greatly expanded,which verifies that the change of pore structure and particle size distribution of char is mainly related to the thermal force loading,while the mechanical force loading will only cause the particle surface to be broken. The particle size change rate is 9.76% and the pulverization rate is 5. 09% under the coupled loading of thermal and mechanical forces,which are higher than those under the loading mode of thermal or mechanical forces alone. The higher the content of volatile matter in coal is,the higher the yield of pyrolysis tar is,the higher the particle pulverization rate is. A function model of average particle size correlation before and after coal pyrolysis and fragmentation is established. The relative error between the model and the experimental value is small (The relative error corresponding to B-L≤3%,the relative error corresponding to X-L≤10%),which can predict the fragmentation/pulverization degree of lignite in the pyrolysis process.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3019K]

Numerical simulation of structure optimization and layout of near-wall air nozzle on an opposed wall-fired boiler
ZHU Xuaner;HUANG Yaji;YUE Junfeng;CHEN Bo;ZHANG Enxian;ZOU Lei;LI Haiyang;LIU Xinya;ZHU Zhicheng;Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education,Southeast University;Jiangsu Frontier Electric Technology Co.,Ltd.;
Taking a 650 MW supercritical opposed wall-fired boiler as the research object,the distribution characteristics of the flue gas components near the water wall of the side wall under different nozzle types and nozzle heights were analyzed by numerical simulation methods. A circular slot nozzle with height of h = 40 mm is selected to design a combination schemes,which can mitigate the hightemperature corrosion of side walls. And the effect of the scheme was evaluated by the whole furnace simulation. The results show that: the simulated high CO concentration area of the side wall coincides with the actual corrosion location under the original condition without adding the wall wind; With the same installation position,nozzle height,air speed and air flux,the reduction rates of the high-temperature corrosion ratio ε of the circular slot nozzle,the vertical slot nozzle,and the horizontal slot nozzle are 4.23%,2.42%,and 5.70%,respectively,and the circular slot nozzle not only has a good anticorrosive effect,but its O_2 distribution characteristics are also more suitable for engineering applications; With the same nozzle type,installation position and air flux,the relative velocity between the nozzle stream and the main stream plays a leading role in the attenuation of the O_2 concentration at the upstream nozzle stream; The intensity of the main stream and its scouring area to the nozzle stream plays a leading role in the attenuation of the O_2 concentration at the downstream nozzle stream. The declines in the high-temperature corrosion ratios ε of the four nozzles h = 30,40,50,and 60 mm are 5.62%,4.23%,3.87%,3.20%. In engineering applications,in order to maintain a good anti-corrosion effect,and avoid the excessive loss of flow resistance and waterwall wear caused by highspeed airflow,it is recommended to select the nozzle with h = 40 mm. The designed combination scheme of near-wall air can form an intersecting O_2 curtain in most side wall area,the proportion of areas prone to high temperature corrosion is reduced to 12.88%,and the scheme has little impact on combustion and pollutant emissions.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 7330K]

Numerical simulation on combustion characteristics of a 300 MW tangentially-fired boiler under low load
JIANG Zhiming;ZHANG Yan;LI Yuesheng;QIU Yanfei;SONG Changzhi;LIU Hu;DENG Lei;CHE Defu;Shunde Institute of Inspection,Guangdong Institute of Special Equipment Inspection and Research;Quality Supervision and Inspection Center of National Industrial Boiler;School of Energy and Power Engineering,Xi'an Jiaotong University;
With the improvement of environmental protection standards,NO_x emission control of power plant boilers is increasingly strict.Low-NO_x retrofit can effectively reduce NO_x generation,but the research on combustion characteristics in low load after retrofit is limited.The combustion characteristics of a 300 MW low-NO_x retrofitted tangentially-fired boiler under low load and multiple operating conditions were numerically simulated in this work. The influence of excess air ratio,burnout air ratio and pulverized coal feeding rate of primary air nozzle on the velocity,temperature and species distributions in the furnace were studied. By improving the grid system,the accuracy of simulation results is improved. The deviation between the simulation results and the experimental measurements is small,which shows that the simulation results are reliable. The results show that with the increase of excess air ratio,the temperature rises up,the reducing species decrease and the NO_x emission increases. When the excess air coefficient increases from 1. 20 to 1. 30,the NO_x emission increases from 221.12 mg/m~3 to 196.26 mg/m~3. With the increase of burnout air ratio,the temperature of the main combustion zone decreases,the temperature of the burnout zone increases. The reduction of the temperature of the main combustion zone inhibits the generation of thermal NO_x ,and the NO_x emission decreases. When the burnout air ratio increases from 20% to 30%,the NO_x emission decreases from 231.21 mg/m~3 to 180.95 mg/m~3. The influences of pulverized coal feeding rate for primary air nozzle on temperature,species concentration and NO_x emission are small.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 5386K]

Experimental study on design and optimization test in 145 t/h high-temperature and ultra-high-pressure CFB boiler
WU Jianheng;LIAN Rongqing;DENG Guorong;LI Boyang;ZHUANG Huanghuang;CHEN Zhiyuan;JIANG Lu;HE Hongzhou;Cleaning Combustion and Energy Utilization Research Center of Fujian Province,Jimei University;Fujian Funeng Long'an Thermal Power Co.,Ltd.;Fujian Shishi Heat & Power Cogeneration Co.,Ltd.;
In order to realize the efficient and clean combustion of Fujian anthracite,the design characteristics of the first domestic 145 t/h high-temperature and ultra-high pressure CFB boiler burning Fujian anthracite are analyzed and refined,which are the combination of traditional measures such as high combustion temperature,blast furnace height,low flue gas flow rate and advanced equipments such as steam cooled high-temperature cyclone separator,platen superheater arranged on the upper part of furnace. The operation test of the influence of coal particle size and secondary air rate on the combustion efficiency and boiler load was carried out,and improvement suggestions was put forward. The results show that the combustible content of fly ash carbon is reduced from 12%-15% to 8%-10% by increasing the screen size of screening machine and decreasing hammer head gap of crusher to optimize coal particle size. It is found that there is the best secondary air rate (the test result is 0.45-0.50),which makes boiler load smooth and combustion efficiency high. The optimization improvement of reducing the width of the flue at the inlet of the separator and the recycle combustion of the fly ash of the dust collector was carried out,which improved the boiler load capacity,and the boiler efficiency operation increased by about 1%. It is suggested to shorten the length of the central cylinder,the inner diameter of the central cylinder and the inner diameter of the return riser to improve the separation efficiency. More than five years of operation practice has proved that the design is successful. The annual average operation time is more than 7 550 h,and the annual average load rate reaches 95.35%. The third party test shows that the average thermal efficiency of the boiler under the load of 151 t/h is 90.57%,which provides solid practical evidence for the construction of small capacity and high parameter units.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 4933K]

Experimental study on direct coupled combustion of biomass and coal
NI Gang;YANG Zhangning;RAN Shenming;LI Weicheng;MO Chunhong;ZHANG Xiuchang;Clean Combustion and Flue Gas Purification Key Laboratory of Sichuan Province;Dongfang Boiler Group Co.,Ltd.;
In order to study the influence of different blending position,proportion,primary air temperature and air rate of biomass and different coal blending on NO emission and combustible matter in fly ash of boiler,the thermal experiments of biomass particle blending combustion was carried out based on a 50 kW downer pulverized coal test boiler. The results show that when the proportion of biomass input heat is 6% and biomass is mixed in from different locations,NO emissions are reduced to a certain extent,and different locations have different rates of reduction. NO emission decreases the most when biomass is fed into the reduction zone,The decrease of bituminous coal is 23.47%,and that of lean coal is 13.64%. After the biomass is mixed in,the flue gas temperature at the outlet of the furnace rises to varying degrees. The biomass blended with bituminous coal should be added in the early stage of combustion,which is more conducive to the burnout of pulverized coal,but the biomass blended with lean coal should be added in the later stage of combustion. When the proportion of biomass blended with combustion is increased from 6% to 12%,the reduction of NO emission increases from 23.31% to 39.5% when coupled with bituminous coal. When coupled with lean coal combustion,the reduction of NO emission decreases from 13.61% to about 10%. When lean coal is used as the main fuel,the absolute value of NO decrease is higher than that of bituminous coal. The reduction of NO by different biomass is related to the nitrogen content in biomass,and the lower the nitrogen content is,the greater the reduction of NO is. By increasing the primary air temperature of biomass,the content of combustible matter in fly ash decreases from 13.88% to 7.62%,and the primary air temperature of biomass should be increased as much as possible without affecting safety. The change of primary air rate of biomass has little impact on combustion efficiency.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3286K]

Study on the corrosion characteristics of KCl molten salt in biomass oxygen-enriched combustion mode
BATE Delige;ZHANG Jiaye;WANG Yongbing;LI Peng;WANG Zhao;WANG Xuebin;TAN Houzhang;Xinjiang Uygur Autonomous Region Special Equipment Inspection and Research Institute;School of Energy and Power Engineering,Xi'an Jiaotong University;Xi'an Thermal Power Research Institute Co.,Ltd.;
The coupling of oxy-biomass combustion and oxygen-enriched combustion technology makes it possible to realize CO_2 negative emissions. However,compared with conventional fossil fuels,biomass contains a large number of alkali metal compounds,which may aggravate the hot corrosion of the heating surfaces in combusting process,and bring great potential danger to boiler operation. As one of the key compounds in biomass ash,it is of great significance to study the corrosion behavior of KCl molten salt on heating surface. In this paper,the molten salt corrosion test of KCl was studied in the simulated flue gas high temperature corrosion test system. Two kinds of superheater and reheater materials (TP347H,HR3C) were studied in different gas environment. Meanwhile,a new salt plating system was used to simulate the condensation process of alkali metal on the tube wall. Then,the corrosion weight gain test was carried out in different simulated flue gas environment. Finally,the corrosion product on the microstructure and composition analysis were further studied. The results show that the weight curves of molten salt corrosion and atmospheric corrosion follow parabola law with time. When KCl is deposited on the surface of superheater and reheater under the same corrosion temperature,the corrosion rate is significantly higher than that of atmospheric corrosion. The increase of temperature can significantly aggravate the corrosion of the materials mentioned above. Compared with 450 ℃,the average corrosion rate of the two materials at 650 ℃ is increased by more than 16 times. Compared with the conventional air combustion mode,CO_2 can promote the migration of Cr element to the metal surface under the oxygen enriched combustion mode,thus protecting the metal surface and reducing the corrosion degree under the oxygen enriched combustion mode. The high concentration of moisture can slightly inhibit the hot corrosion. Compared with TP347H,HR3C is more resistant to molten salt corrosion because of high Cr and Ni content.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 6846K]

Investigation on the reaction kinetics of simultaneous removal of NO_x and Hg by ozone in waste incineration flue gas
SHAO Jiaming;WANG Zhihua;LIN Fawei;TANG Hairong;XU Yanwei;HE Yong;CEN Kefa;State Key Laboratory of Clean Energy Utilization,Zhejiang University;School of Environmental Science and Engineering,Tianjin University;Everbright Environmental Technology Research Institute (Nanjing) Co.,Ltd.;
In recent years,the integrated removal technology of multi-pollutants by ozone has been successfully applied in air pollution treatment.Ozone,as one of strong oxidant,can not only realize NO deep oxidation in flue gas,but also remove trace heavy metal Hg by oxidation.In this paper,the kinetics reaction mechanism of ozone and multi-pollutants was established and the simultaneous removal of NO_x and Hg by ozone in waste incineration flue gas was investigated by using Chemkin Pro software.By analyzing the sensitivity coefficient of NO and Hg and O_3 reaction,the key elementary reactions of NO and Hg oxidation by O_3 were obtained,and the reaction pathways of NO and Hg oxidation were also proposed.Besides,the effect of reaction temperature,O_3/NO molar ratio and reaction time on NO_x and Hg removal were also studied by changing the initial parameters. The modeling results show that the NO and Hg oxidation efficiency increases with the increasing O_3/NO molar ratio.The reaction temperature plays an important role on the process of NO deep oxidation by O_3 and the process of Hg oxidation removal.The low reaction rate at too low temperature leads to longer reaction time,while too high temperature resultes in the decomposition of intermediate species,thereby reducing the removal efficiency.The reaction time of NO deep oxidation to N_2O_5 is much longer than that of primary oxidation to NO_2.The reaction time for NO deep oxidation is about 5-8 s under the optimal reaction temperature 60-80 ℃. The presence of HCl in the waste incineration flue gas is beneficial for Hg oxidation.The Hg oxidation reaction time and optimal temperature is 4-6 s and 110-130 ℃,respectively,with HgO and HgCl_2 as the finally products.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 4683K]

Experiment and mechanism study on NO removal from flue gas by activated coke at low temperature
ZHANG Yuan;CHEN Long;China Coal Research Institute Company of Energy Conservation;State Key Laboratory of Coal Mining and Clean Utilization;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;China Coal Research Institute;
activated coke is an excellent pore structure material. The desulfurization and denitration performance of activated coke at medium and high temperature has been studied extensively by predecessors,but the denitration performance of activated coke at low temperature (<100 ℃) has been rarely studied. In order to study the characteristics of NO removal by activated coke at low temperature,simulated flue gas was prepared according to the actual flue gas group of pulverized coal industrial boiler,and the test bench of fixed-bed reactor was built. The influence of process conditions on NO removal efficiency of activated coke was studied by changing the parameters such as temperature,oxygen concentration,SO_2 concentration and moisture. The microstructure and surface chemical properties of the activated coke before and after the reaction were characterized by FT-IR,in-situ IR,TG-DTA,photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). The experimental results show that at 50-90 ℃,the lower the temperature is,the higher the oxygen concentration is,and the higher the NO removal efficiency of activated coke is. The presence of SO_2 and water is not conducive to the removal of NO by activated coke. SO_2 has strong polarity and will compete with NO for adsorptive sites and active sites. Water will form a layer of water film on the surface of activated coke,which makes the activated coke toxic. Physical adsorption and chemical catalytic oxidation take place simultaneously in the NO removal of activated coke at low temperature,and physical adsorption is the main process. Physical adsorption depends on the rich microporous structure and excellent specific surface area of activated coke. Chemical catalytic oxidation depends on free oxygen in flue gas and oxygen-containing functional groups on the surface of activated coke. The initial desorption temperature of NO is 150 ℃,the highest desorption concentration is observed at 225 ℃,and the desorption complete at 600 ℃. The initial desorption temperature of NO_2 is 175 ℃,the desorption concentration reaches the highest at 225 ℃,and NO_2 is completely desorbed at 500 ℃.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 5576K]

CO_2 adsorption characteristics of synthesized Na Y zeolite
SUN Feng;WANG Chenyang;LUO Cong;LI Xiaoshan;LUO Tong;China Ship Development and Design Center;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
zeolite based CO_2 adsorbents has many advantages of low energy consumption,low corrosion rate to facility and high cyclic stability,while its adsorption capacity is relatively low. In order to screen out zeolite adsorbents suitable for large-scale CO_2 capture technology,advanced synthesis methods are needed to improve the CO_2 sorption capacity of zeolite adsorbents to overcome the disadvantage of low sorption capacity. In this paper,the NaY zeolite was synthesized through hydrothermal synthesis,and the CO_2 adsorption properties of NaY,13X and 4A zeolite adsorbents were investigated. The influence of pressure,temperature and sodium bromide modification on the adsorption capacity was analyzed comprehensively. The results show that the CO_2 adsorption capacity of the three adsorbents decreases with the increase of temperature but increases with the increase of pressure. NaY zeolite has the highest CO_2 adsorption capacity at 25 ℃,0.1 MPa,which is 3.74 mmol/g. And its adsorption performance maintains stable after 8 regenerative cycles with a decrease of 2.5%. The NaY zeolite modified with sodium bromide impregnation method was investigated. The results show that the CO_2 adsorption capacity of NaY zeolite enhanced by impregnation modification with sodium bromide. With the increasing concentration of sodium bromide solution,the CO_2 adsorption capacity of the modified adsorbent increases within certain limits. The NaY zeolite modified with sodium bromide solution of 0.1 mmol/g shows the CO_2 adsorption capacity of 4.05 mmol/g at 25 ℃,under 0.1 MPa pressure,of which the performance is improved by 8.4% comparing to the unmodified sorbents. However,when the concentration of the sodium bromide solution exceeds 0.1 mmol/g,the performance of the adsorbent is not significantly improved by further increasing the concentration. The optimal concentration of the sodium bromide solution used for impregnation method is 0.1 mmol/g.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3847K]

Study on NO_x migration path and detailed mechanism after fuel fluidized preheating
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;
In order to further control pollutant emissions and achieve the goal of carbon neutrality,oxy-fuel combustion technology has received more and more attention as a clean combustion technology.Combined with oxy-fuel combustion technology and preheating combustion technology based on circulating fluidized bed,it is beneficial to further reduce NO_x emissions and improve fuel adaptability.For exploring the migration path of NO_x of different fuels with preheating oxy-fuel combustion technology and based on the O_2/CO_2 combustion technology of circulating fluidized bed preheating,Shenmu bituminous coal and semi-coke were used as contrast fuels,and the perfectly stirred reactor (PSR) in CHEMKIN software were used with preheated fuel as the input parameters.Moreover,the rate of production analysis (ROP) and sensitivity analysis (SA) were used to explore the migration path of NO_x in combustion. Comparing the simulation calculation results with the previous experimental results,the results show that the two-stage PSR model can perform a good calculation simulation of the gas-phase combustion in the down-fired combustor (DFC),and the adaptability of the model is good,and the method of the input parameter setting is feasible.In the O_2/CO_2 atmosphere,the combustion of CO_2 in the DFC is dominated by the formation reaction.Besides,the increase of CO_2 partial pressure promotes the generation of NO.The basic migration path of the gas-phase reaction of nitrogen-containing in the combustion process of bituminous coal and semi-coke is consistent.In the main combustion zone,the main path of NH_3 conversion is NH_3→NH_2→NH→HNO→NO,the reactions of NH→N→NO are occurred during the combustion of bituminous coal.In addition to the consumption reaction,HCN can also be generated by the reaction of hydrocarbon groups with NO.The increase in the concentration of hydrocarbon groups can promote the formation of NH_3 and HCN for semi-coke.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 10285K]

Study on particulate matter emission characteristics of semi-dry desulfurization and dust removal system for coal fired industrial boilers
WANG Jianpeng;DUAN Lu;JI Renshan;WANG Zhiqiang;YANG Shi;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;
With more and more strict national requirements on the emission of fixed-source particulate matter,it is necessary to conduct in-depth study on the physical and chemical changes of the emission process of particulate matter in the pollutant control system. In this paper,a pollution control system of pulverized coal industrial boiler was designed based on semi-dry desulphurization technology,four measuring points were set along the system,and the particles were sampled at constant velocity,and the particulate matter was tested and analyzed by weighing,laser particle size meter,SEM-EDS and XRD. The results show that the particulate matter concentrations at the four sites are 9.90 g/Nm~3,793.50 g/Nm~3,92.14 g/Nm~3 and 26.72 mg/Nm~3,respectively.The measured concentration of particulate matter at the outlet of flue gas emission is 16.84 mg/m~3,the measured oxygen content is 8.07%,and the emission concentration of particulate matter at the outlet of bag dust collector is 12.69 mg/m~3 when the oxygen content is 9%,which can meet the emission requirements of industrial boiler. Particulate matter at the inlet of the semi-dry desulfurization reactor is mainly composed of boiler outlet fly ash and humidifying circulating ash. The particle size distribution shows a typical bimodal distribution pattern,with the peak value at 0.7 μm and 22 μm.The fraction of particle size less than 1,1.0-2.5,2.5-10 μm and more than 10 μm is 2.38%,2.59%,16.47% and 78.54% respectively;the particle size distribution peak value migrates to the large particle size direction after desulphurization reactor,which appears at 1 μm and 90 μm respectively,and the fraction of particle size varies little. After cyclone separator,the particle size distribution peak value of fly ash particles migrates to small particle size direction,which appears at 0.7 μm and 6 μm respectively. The total concentration and classification concentration of fly ash particles decrease,and the proportion of large particles decreases significantly. The particles of the four measuring points are different in morphology and composition,the irregular structure of the fly ash particles at the outlet of the boiler is more,and there is obvious agglomeration phenomenon,the particle size is larger,and its composition is similar to that of the coal-fired fly ash. At the outlet of desulphurization reactor,the larger irregular porous block structure of fly ash particles decreases obviously,while the content of inhomogeneous regular spherical structure increase,the surface of particles is accompanied by fine irregular substances,and the content of Si,S and Ca elements in element content increase. Through XRD detection and analysis,it is found that the main components of particulate matter before desulphurization are ettringite,SiO_2 and Ca(OH)_2,which are consistent with the components of coal-fired fly ash,and the main components after desulphurization are CaO,CaSO_4·2H_2O and SiO_2,respectively.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 6539K]

Research on the technology of co-pyrolysis and dust removal of biomass and bituminous coal in fluidized bed
HUANG Yong;LIU Qiaoxia;LIU Dan;ZHANG Xiaoqian;WANG Wusheng;Engineering Research Center for High-efficiency Utilization of Fossil Hydrocarbon Research of Petroleum and Chemical Industry;Hydrocarbon High-efficiency Utilization Technology Research Center,Shaanxi Yanchang Petroleum (group) Co.,Ltd.;
The co-pyrolysis characteristics of straw and low rank bituminous coal were investigated in a self-designed fluidized bed pyrolysis device,and the influence of temperature,pressure and feed rate on dust removal efficiency on the pyrolysis oil yield was studied. The results show that: with the condition of biomass blending ratio of 70 ∶ 30,600 ℃,0.3 MPa and nitrogen atmosphere,straw pyrolysis can provide enough hydrogen and alkaline/alkaline earth metal elements to balance the reaction of free radical and hydrogen donor in coal pyrolysis,change the caking property of coal,destroy the caking coke reaction of coal,and release the volatiles to the greatest extent. The total yield of co-pyrolysis oil is 16.90%,which is 13.05% higher than the theoretical value. With the increase of temperature,the density,viscosity and other properties of dusty gas are changed,and then the movement law of dust is changed. The dust removal efficiency increases at first and then decreases,influenced by enhanced thermal agglomeration and increased viscous resistance of char particles. The maximum dust removal efficiency reaches 94.8% at 450-500 ℃. When the pressure of pyrolysis increases from 0.1 MPa to 0.7 MPa,the gas-solid separation efficiency decreases from 97.52% to 96.34%,and the yield of pyrolysis oil decreased from 21.05% to 18.64% due to inhibition of volatilization under pressurized condition. The gas-solid separation efficiency is reduced because of the high powder concentration with high feed rate. The feed rate increases from 1.0 kg/h to 2.5 kg/h,the gas-solid separation efficiency decreases from 98.2% to 93.5%,the yield of pyrolysis oil decreases from 21.05% to 18.22%,and the dust content in oil increases from 1.05% to 5.04%.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 2719K]

Preparation of coconut shell activated carbon used for separation of CH_4/CO_2 in coal bed methane
LIANG Jiangpeng;MA Bowen;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;
In order to solve the problem of adsorbents for the separation of CH_4/CO_2 from coal bed methane,activated carbon adsorbent was prepared by steam activation process with coconut shell carbonized material as raw material. The effects of activation temperature,activation time and dosage of modifier on the separation performance of CH_4/CO_2 by pressure swing adsorption were studied. The results show that the optimum conditions for preparation of activated carbon adsorbent are as follows: carbonization temperature is 600 ℃,activation temperature is 800 ℃,activation time is 30 min,dosage of modifier is 10%. Under the optimum conditions,the saturated adsorption capacity of the prepared activated carbon adsorbent for CH_4 and CO_2 is 2.34 mmol/g and 3.23 mmol/g respectively. The equilibrium adsorption separation coefficient is 10.27,which is 190% higher than that without modification. There is a good separation effect for CO_2/CH_4. The CO_2/CH_4 equilibrium adsorption separation coefficient and the adsorption capacity of CO_2 and CH_4 increase firstly and then decrease with the increase of activation temperature. This is because when the activation temperature reaches 800 ℃,the activation temperature reaction speed increases significantly,which makes the wall of the micropores easy to burn through to form mesopores,and even further form macropores. The specific surface area of activated carbon adsorbent decreases,the number of micropores decreases,and the adsorption capacity decreases. The CO_2/CH_4 equilibrium separation coefficient and the adsorption capacity of CO_2 and CH_4 increase at first and then decrease with the extension of activation time. The reason is that after the activation time reaches 30 minutes,more water vapor reacts with the carbon to burn through the micropores,resulting in the decrease of the specific surface area and volume of the micropores,as well as the decrease of the adsorption capacity of adsorbent for CO_2 and CH_4,and the reduction of CO_2 adsorption capacity is more obvious. The equilibrium separation coefficient of CO_2/CH_4 increases gradually with the increase of modifier content,and the adsorption capacity of CO_2 and CH_4 increase firstly and then decrease,The adsorption performance of the adsorbent for CO_2 is significantly improved,while the adsorption performance for CH_4 is significantly reduced.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3738K]

Experimental study on the complex extraction of acidic organic compounds in Fischer Tropsch synthesis water
WANG Jikun;GAO Minglong;LI Wenbo;CHEN Guifeng;Coal Chemical Branch of China Coal Research Institute;
In order to determine the best extraction agent of Fischer Tropsch synthesis water complexing and the process conditions of high efficient removal of acidic organic compounds. Trioctylamine (TOA) and tributyl phosphate (TBP) was elected complexing agents and Noctanol was elected diluent and sulfonated kerosene was elected cosolvent to investigate the extraction effect,stratification time,emulsification of different extractants. The impact of extraction stages,agent-water ratio,extraction time and temperature on the extraction rate of acidic organic compounds were studied and the optimum extraction conditions were determined. The stability of the continuous deacidification effect of extractant was studied under the optimum conditions; Finally,the association mechanism of the extraction of acidic organic compounds by complexation extractant was studied. It is concluded that the organic matter in the wastewater is mainly acidic organic matter,and mainly consisted of formic acid,acetic acid,propionic acid and butyric acid; The experimental study on complex extractant show that the extraction effect of TOA is better than TBP,considering the good extraction effect,low economic cost,fast stratification effect and no emulsification,and the best complexing extractant is 20% TOA-30% N-octanol-50% sulfonated kerosene; Through the experimental study,the best extraction deacidification process conditions is that the ratio is 1 ∶ 4,the temperature is 25 ℃,the extraction time is 10 minutes,and the acid organic matter removal rate is stable at 92% after three-stage extraction; Under the optimum extraction conditions,the deacidification rate is about 93% after continuous extraction for 45 h; It is found that the association mechanism of TOA extraction of acidic organic compounds is ion association and hydrogen bond association,and that of TBP extraction of acidic organic compounds is hydrogen bond association.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 3236K]

Influence of ultra-high temperature plasma gasification and melting on municipal solid waste incineration fly ash
YANG Fengling;LI Pengfei;REN Lei;JIA Yangjie;ZHU Zhujun;ZHANG Peihua;Collaborative Innovation Center of High Value-added Utilization of Coal-related Wastes,State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources,Shanxi University;Shanxi Rui En Ze Technology Co.,Ltd.;Shanxi Gemeng Sino-American Clean Energy R & D Center Co.,Ltd.;
In recent years,the amount of harmless waste incineration treatment in China has been increasing year by year. With the increasing amount of fly ash generated after garbage incineration,the heavy metals and other harmful substances in fly ash have great pollution to the environment. Taking the municipal solid waste incineration (MSWI) fly ash produced by a municipal solid waste power plant in Taiyuan as the research object,The samples of ash/coke (6∶1) and ash/coke (9∶1) were melted at 1 700 ℃ in an ultra-high temperature plasma gasification melting furnace,and the composition,microstructure and element distribution of MSW fly ash and molten glass slag were characterized and analyzed by XRF,XRD and SEM-EDS. The study shows that the metal chlorides in the fly ash of MSWI mostly exist in the form of Na Cl and KCl,accounting for about 5% of the composition of the fly ash. High temperature melting is conducive to the gasification of chlorine salt in the fly ash of MSWI,and the content of chlorine salt in the fly ash of MSWI is reduced. The fly ash is mainly flocculent and spherical,and the surface is enriched with many metal elements. can The acid oxide Si O2 in the fly ash can be recombined by the high temperature melting,which realize the encapsulation of heavy metals. The leaching amount of molten glass slag after melting is lower than the leaching toxicity standard of various countries.The high temperature melting at 1 700 ℃ will make the high temperature resistant material ZrO_2 fall off inside the furnace,leading to a shorter service cycle. The basicity coefficient is the main reason affecting the melting temperature. The reduction of basicity coefficient can reduce the melting temperature. It is necessary to further adjust the basicity coefficient so as to reduce the melting temperature in the furnace and extend the service life of ZrO_2. Therefore,before melting treatment,the characteristic temperature of the ash melting point of the sample can be determined,and the melting temperature of the melting furnace can be set accordingly to avoid the falling off of the insulation material due to the high temperature.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 6977K]

Leaching of high alumina fly ash sintered clinker with low lime dosage
ZHENG Huan;FENG Xiaolan;ZHAO Bo;YANG Gang;YANG Pengcheng;LIU Yuchun;ZHANG Jinfei;Shanxi Coal Chemial Industry Technology Research Institute Co.,Ltd.;Xi'an Hi-TECH Industries Development Zone Environmental Protection Bureau;Xi'an University of Architecture and Technology;
In this paper,the leaching technology of high-alumina fly ash from the clinker obtained by low-calcium dry sintering of soda lime was studied. The effects of leaching time,leaching temperature,liquid-solid ratio and alkali concentration on the leaching rate of sodium aluminate in clinker were investigated. The optimum technological parameters for leaching sodium aluminate from alumina clinker were explored. The phase of clinker was characterized by XRD and SEM before and after leaching. The kinetics of NaAlO_2 in leached alumina clinker was discussed. The results show that the leaching rate of sodium aluminate reaches more than 94% under the conditions of leaching time 7 min,leaching temperature about 65 ℃,liquid-solid ratio 5,and alkali concentration 0. Compared with the traditional standard leaching of bauxite at the temperature of (85±1) ℃ for 15 min,the leaching process is simple,the consumption of alkali is low,the leaching time is short and the leaching efficiency of aluminum is high. The kinetic analysis of sodium aluminate (NaAlO_2) leaching process of alumina clinker was carried out by shrinking core model,and its apparent activation energy was 26. 585 kJ/mol. The reaction is under mixed control and the activation energy of leaching reaction is low. This study provides basic parameters for the industrial practice of fly ash preheating and precalciner-lime suspension precalciner-low calcium dry sintering. The new process can reduce the consumption of alkali,shorten the leaching time,improve the leaching efficiency of aluminum,and promote the industrialization process of extracting alumina from high aluminum fly ash.
2021 03 v.27;No.133 [Abstract][OnlineView][HTML全文][Download 4104K]

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