2023年08期目次

  • Research on hydrogen production pathway by underground coal gasification

    LIU Shuqin;QI Chuan;JI Yutong;LIU Huan;CAO Di;School of Chemistry and Environmental Engineering, China University of Mining and Technology-Beijing;College of Chemistry and Chemical Engineering,Xi'an Shiyou Unversity;

    Hydrogen is a key component of the future national energy system and an important carrier for achieving green low-carbon transformation in energy end-use sectors. The large-scale supply of green and low-cost hydrogen is an urgent need for the future development of the energy system. Underground coal gasification(UCG) technology efficiently can convert in-situ coal into hydrogen-rich combustible gas, and store CO_2 during gasification into gasification cavity, which is expected to be an ideal low-cost hydrogen supply path. The generation mechanism of hydrogen-rich gas during UCG was focused on, typical engineering cases of hydrogen production via UCG was summariztd and cost of different hydrogen production technologies and deepens the deep UCG coupled with carbon capture, utilization, and storage(CCUS) hydrogen production pathway were compared. The research results indicate that, the direct sources of hydrogen-rich gas in the UCG process include coal pyrolysis reaction, steam-reducing reaction, and water-gas shift reaction in the gas flow channel at lower temperature. The medium-to-low temperature pyrolysis zone in the coal seam is a significant part of the product gas, which mainly produces hydrogen-rich gas H_2 and CH_4. The rich water characteristics of the coal seam and the high gasification activity of H_2O(g) make the reduction zone dominated by the steam decomposition reaction. Moreover, the long gas flow channel at lower temperature and catalytic effect of gasification slag further promote water-gas shift reaction. Operating data from typical demonstration projects at home and abroad have verified that UCG has a natural advantage in producing hydrogen-rich gas, and its hydrogen production cost is much lower than that of surface coal gasification and natural gas. Injecting carbon dioxide back into the gasified cavity has the dual advantages of mineral carbonation and physical carbon storage. Coupling CCUS technology with deep UCG for hydrogen production and simultaneously producing chemicals or jointly driving deep oil/gas recovery can form a low-cost hydrogen production path with near-zero carbon emissions of carbon dioxide. The coupling of CCUS technology with deep UCG for hydrogen production has important significance for exerting the pillar role of a new energy system, solving the carbon emission problem of fossil energy hydrogen production, and it is a road to clean transformation and development of fossil energy with Chinese characteristics that conforms to the national conditions of China.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 14797K]

  • Research and development potential analysis of low-carbon technologies based on ex-ante life cycle assessment methodology

    LU Jiaqi;LIAO Wenjie;ZHANG Nan;GU Dungang;RAO Pinhua;LI Guanghui;Innovation Centre for Environment and Resources,Shanghai University of Engineering Science;Institute of New Energy and Low-Carbon Technology,Sichuan University;The Centre for Process Integration,The University of Manchester;

    The development of low-carbon technologies is one of the essential pieces to achieve carbon peak and carbon neutrality in China. However, from a life-cycle perspective, the industrial application of new technologies also requires additional resource inputs and brings new emissions, and the carbon reduction effect is uncertain. Thus, life cycle assessment(LCA) is needed to quantify the contribution of all unit processes to the carbon footprint, and to guide the process design and optimization of low-carbon technologies. For the conventional LCA, the environmental impacts are ex-post evaluated based on the industrial-scale production system, but it is difficult to obtain the data required for LCA for technologies that are still being developed at a pilot scale. Therefore, to evaluate the potential life-cycle environmental impacts of a technology under lab-scale development, the methodology development for ex-ante LCA will be a vital topic in the field of industrial ecology. At first, the main issues about the methodology of ex-ante LCA were summarized, including the difficulty of modeling the inventory data, defining the system boundary, and result interpretation. In addition to the application of the ex-ante LCA method to roughly estimate the potential carbon footprint and other environmental impacts of new technologies, it Is proposed that a more important function is to identify and optimize processes with high environmental impacts by quantifying the current carbon footprint of industrial ecosystems related to new technologies as a baseline target for the research and development of new technologies, so as to make low-carbon design recommendations for industrial applications. By summarizing representative cases of ex-ante LCA of emerging technologies, it is found that there is an order of magnitude gap between the carbon footprint calculated based on pilot-scale data and the actual industrial scale, so it is recommended to invest a small amount of additional manpower and software and hardware resources in the research and development process to realize the amplified simulation of the process, predict the energy consumption and input/output lists of the industrial scale, and carry out the life-cycle environmental impact assessment. Finally, as a case study for guiding the low-carbon development of technologies, the green design of a Cl recovery process for PVC waste was revealed by the integration of experiment, simulation, and ex-ante LCA for quantifying the influence of process variables such as different reactant concentrations, treatment volumes, reactor designs, operating conditions and other process variables on the list of process inputs and outputs, such as consumption of energy and raw and auxiliary materials, direct emissions, product yields, and the amount of wastes generated. Meanwhile, it realizes the use of carbon footprint as an evaluation indicator to guide the research and development of low-carbon process design and operating conditions for new technologies.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 21757K]

  • Numerical simulation of heat transfer during in-situ convection heating pyrolysis of tar-rich coal

    MAO Qisen;WANG Chang′an;HOU Yujie;CHEN Meijing;NING Xing;DENG Lei;CHE Defu;State Key Laboratory of Multiphase Flow in Power Engineering,Xi′an Jiaotong University;

    Tar-rich coal is a kind of coal resource with the properties of coal, oil and gas, mainly occurring in middle and low rank coal, with the characteristics of high tar yield. In situ pyrolysis of tar-tich coal is a technology that produces small molecule oil and gas by underground heating without mining, thereby achieving efficient and clean utilization of tar-tich coal resources. In order to clarify the influence rule of multiple factors in the heat transfer process of in-situ pyrolysis of gas injection and explore the contradictory relationship restricting the heating rate in the heating process, a three-dimension model of coal seam, heating well and production well was constructed by using Fluent numerical simulation method. The influence of factors such as heating medium, fluid velocity, fluid temperature and fracture distribution on the overall temperature field distribution of coal seam was studied. The numerical simulation results show that there is no significant difference in the effect of different heating media on the temperature of coal seam. Compared with water vapor and nitrogen, carbon dioxide as the heating medium has a relatively better effect. The proportion of effective heating zone cannot be increased to more than 25% with different flow rates under the heating condition of a single fracture, and the average temperature of coal seam is also lower than 380 ℃. The overall heating rate can be increased significantly by increasing the temperature of heating medium.When increasing the temperature of the heating medium by 50 ℃, the effective heating area can be increased by 8% fractures, and the average temperature of the coal seam is increased by 29 ℃. Under the heating conditions of three cracks, the heating rate is greatly improved compared with that of single well mode, and the temperature of the entire coal seam can be raised to 100% effective heating range within 2 years. The uneven fluid distribution in multiple transverse fractures can be improved by adding longitudinal fractures. The influences of different factors on heat conduction and utilization in the pyrolysis process of tar-tich coal are obtained, which is conducive to the enhancement of heat transfer and the improvement of heat utilization efficiency in the heating process of tar-tich coal.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 40442K]

  • Synergistic effect for co-pyrolysis of BHTK and CYFL

    LIU Qiaoxia;GAO Yanan;YANG Huimin;SUN Ming;HAO Ting;HUANG Yong;Hydrocarbon High-efficiency Utilization Technology Research Center of Yanchang Petroleum(group) Co.,Ltd;School of Chemical Engineering,Northwest University;International Science & Technology Cooperation Base for Clean Utilization of National Hydrocarbon Resources,Northwest University;Shaanxi Research Center of Engineering Technology for Clean Coal Conversion,School of Chemical Engineering,Northwest University;

    The co-pyrolysis ofBHTK and CYFL was studied in fixed bed and fluidized bed. The effects of heating rate and mixing ratio on co-pyrolysis were investigated in fixed-bed experiment. The results shows that with the increase of heating rate, the weight loss rate increased, showing a simple addition trend of single pyrolysis, and the synergistic effect of co-pyrolysis is not obvious. The effects of temperature and mixing ratio on the product distribution and the synergistic effect of co-pyrolysis oil were investigated in the fluidized bed experiment.The results shows significant synergy that when the reaction pressure is 0.1 MPa, conveying gas 15 L/min, flow gas 25 L/min, feed rate 1.5 kg/h and N_2 atmosphere, the mixing ratio is 30%( BHTK weight ratio), the oil yield is 18.75% at 600 ℃, and synergistic effect has the maximum 39.30%.Compared with coal tar, the content of S decreased from 0.6% to 0.38%, the content of C decreased from 82.00% to 72.28%, and the H/C increases from 0.095 to 0.099. The quality of oil improves significantly, phenolic compounds are mainly concentrated in 3-cresol(21.80%), phenol(16.43%), 2,4-dimethylphenol(13.15%), catechol(12.53%), and naphthalene compounds are mainly concentrated in 1-methylnaphthalene(45.69%), alkylnaphthalene(19.43%), and 2,6-dimethylnaphthalene(10.75%) and other kinds of compounds for extraction using.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 21338K]

  • Performance optimization of catalyst for direct coal liquefaction

    WANG Xiwu;CHEN Chuanfu;XIE Jing;GUI Hezheng;Ordos Coal to Oil branch,China Shenhua Coal to Oil Chemical Co.,Ltd.;Shanghai Research Institute,China Shenhua Coal to Liquid and Chemical;National Engineering Laboratory for Direct Coal Liquefaction;

    In order to improve the performance of direct coal liquefaction catalyst and the operation stability of oxidation reactor, the influencing factors of catalyst performance and operation stability of oxidation reactor were analyzed. The operating conditions such as oxidation reaction temperature, pH of reaction environment, oxidation air volume, material flow rate and material concentration in the reactor, as well as the optimization and adjustment measures of oxidation reactor tray structure during the preparation of catalyst were studied. The catalysts prepared under different operating conditions were evaluated in the laboratory for direct liquefaction of autoclave coal. The results show that the morphology of α-FeOOH and γ-FeOOH crystal catalysts is rod-like or slate-like structure, and the higher the specific surface area is, the higher the coal liquefaction activity is. γ-FeOOH crystal catalyst has the best catalytic effect on coal pyrolysis to asphaltene compared with Fe_3O_4 crystal catalyst. Different catalysts is prepared by adjusting the operating conditions such asthe oxidation reaction temperature, reaction environment pH, oxidation air flow. Through comparison with electronmicroscope scanning, it is found that the catalyst prepared under operating conditions of lower reaction temperature, loweroxidation environment, pH and higher oxidation air volume on industrial devices has better crystal morphology. The product of the catalyst can form α-FeOOH or γ-FeOOH crystal phase, which has high dispersion characteristics and the best performance of the catalyst. Through analyzing the problems of high oxidation reaction temperature, frequent failure of online pH meter and frequent clogging of oxidation reactor tray in the preparation of direct coal liquefaction catalyst in industrial installations, the methods of reducing oxidation reaction temperature, optimizing pH monitoring of reaction environment and subsequent improvement measures were put forward. At the same time, by increasing the flow rate of materials and reducing the number of trays in the oxidation reactor, the blocking of trays can be slowed down, and the operation time of the oxidation reactor can be prolonged and the operation stability can be improved.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 26296K]

  • Solubility and morphology of wax crystal of vacuum distillate of Fischer-Tropsch oil in solvent

    YU Yanan;JIANG Chenguang;ZHANG Shengzhen;ZHANG Cuiqing;National Institute of Clean-and-Low-Carbon Energy;

    The commonly used production process of paraffin from feedstock oil is solvent dewaxing, so it is very important to find out the thermodynamic basic data of feedstock oil in organic solvent and the crystalline morphology of wax crystals.The solubility of hydrofining of 3rd vacuum side-cut foots oils obtained from Fischer-Tropsch synthesis(i.e. vacuum distillate) in Toluene, Methyl isobutyl ketone, 2-Butanone, 2-Propaol and 2-Butanone-Toluene mixed solvents(3∶1) were measured by a dynamic method.The results show that the solubility of the vacuum distillate in those 6 solvents all increases with the increase of temperature, with the greatest solubility in toluene and the lowest solubility in 2-Propaol.The modified Apelblat equation, simplified Van′t Hoff equation and Polynomial equation were used to correlate the experimental solubility data.The results indicate that the solubility data can be well correlated by these three models, and the obtained model equation can predict the solubility of vacuum fractions in 6 solvents within the measured temperature range, with the binomial equation fitting the best.The dissolution Gibbs energy, dissolution enthalpy and dissolution entropy of the binary system of vacuum distillate oil and organic solventwere obtained on the basis of the modified Van′t Hoff model and the experimental data. The results show that the dissolution process of vacuum distillate in the studied solvents is an endothermic and non-spontaneous process, and the confusion of the system increases during the dissolution. The morphology of wax crystals crystallized in 6 solvents were observed with a polarizing microscope.The results show that the wax molecules precipitated to form flake crystals with short-range ordering. The wax crystals have the largest radial dimension in the 2-Butanone-Toluene mixed solvents, but still not exceeding 50 μm. the wax crystals precipitate in 2-Butanone-Toluene and Methyl isobutylketone have larger radial size and better deoilization effect.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 11977K]

  • Preparation of coal tar pitch-based mesophase pitch and electrochemical performance of derived carbons for lithium-ion batteries

    YAO Weiqiang;TONG Lingwen;HE Hu;CAO Ruixiong;LIU Xuewei;CHEN Wensheng;LI Kun;YIN ZHipeng;SONG Huaihe;State Key Laboratory for Effective Utilization of Chemical Resources,Beijing University of Chemical Technology;Changzhou Carbon New Material Technology,Beijing University of Chemical Technology;

    In order to study the influence of the preparation conditions of needle coke on the performance of lithium-ion batteries, the formation of semi-coke were studied during the thermal polycondensation reaction of coal tar pitch, and the morphological structure of the polymerized products was characterized by polarized light microscopy and X-ray diffraction spectroscopy(XRD), focusing on the effects of temperature, time and pressure on the polymerized products during the polymerization of coal pitch. The effect of temperature, time and pressure on the structure of the polymerized products was investigated. The experimental results shows that the temperature has the most obvious influence on the reaction, and when the temperature is lower than 430 ℃, the reaction can not further coke the product for a longer time. When the temperature is 440 ℃, the structure of the polymerization product can be controlled by time and pressure, and the structure of the polymerization product is fine grains or mosaic structure of fine grains and coexistence of coarse grains. Comparing the electrochemical data of the polymerized product after charring and graphitization under different pressure, it can be seen that the condition of pressure 2 MPa has the highest charge/discharge specific capacity, the charge specific capacity is 219 mAh/g and the discharge specific capacity is 268 mAh/g. After graphitization of 2 800 ℃ and 50 cycles, the specific capacity is 331 mAh/g and the retention rate is 98%.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 54388K]

  • Preparation and electrochemical performance of nitrogen-doped coal tar pitch-based porous carbon by chemical foaming coupled with KOH activation

    JIN Zhanzhan;HE He;SHI Feng;XING Baolin;HUANG Guangxu;ZHANG Chuanxiang;LIU Quanrun;College of Chemistry and Chemical Engineering, Henan Polytechnic University;State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization;

    Using the coal tar pitch as the carbon precursor, ammonium sulfate as the foaming agent and nitrogen source, and KOH as the activator.Nitrogen-doped three-dimensional structured porous carbon was prepared by chemical foaming coupled with KOH activation. The microstructure and heteroatom content of coal tar pitch based porous carbon were controlled by adjusting the alkali carbon ratio and the effects of alkali carbon ratio and heteroatom content on the performance of porous carbon were investigated. The structure and composition of the materials were characterized by SEM, XPS, and N_2 adsorption and desorption, and the electrochemical properties of the materials were evaluated with Galvanostatic Charge-Discharge, Cyclic Voltammetry, and Electrochemical Impedance Spectroscopy. The results show that chemical foaming coupled with KOH activation not only optimizes the internal pores to form a hierarchical pore structure and dopes the carbon skeleton with an appropriate amount of heteroatoms, but also effectively improves the electrochemical performance of the porous carbon under the dual effect. The optimized NPC-2 shows a high specific surface area(1 636 m~2/g), abundant nitrogen(5.27%), and mutually cross-linked nitrogen-doped carbon skeleton. In the three-electrode system, the NPC-2 electrode material obtains a high mass specific capacitance with a mass specific capacitance of 374.2 F/g at a current density of 0.5 A/g; when the current density is as high as 100 A/g, its mass specific capacitance can still reach 249.5 F/g and the capacitance retention rate can reach 66.7%, showing excellent electrochemical performance. This excellent performance is derived from the well-developed graded pore structure and excellent carbon conductive network.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 24037K]

  • Preparation of activated carbon for flue gas cleaning by carbonization and activation integration process and its denitrification performance

    LU Xiaodong;XI Yi;YANG Qian;MA Rongfu;XIE Wei;Activated Carbon Branch,Xinjiang Energy Co., Ltd.,China National Energy Group;Huaibei Clean ECO-Technology Co.,Ltd.;China Coal Processing and Utilization Association;State Key Laboratory of Coal Mining and Clean Utilization;Beijing Research Institute of Coal Chemistry,China Coal Research Institute Corporation Ltd.;

    Carbonization and activation integration process can shorten the process of activated carbon preparation, save investment and reduce consumption, for the production of flue gas purification of activated carbon has more obvious advantages. Under the established production process conditions, raw coal determines the strength, pore structure and surface chemistry of activated carbon to a large extent. At present, the influence of using the characteristics of raw material coal to adjust the performance of activated coal products is rarely studied. Typical coal of different rank is selected as raw materials, and the activated carbon is prepared by carbonization and activation integrated(CAI) and carbonization and activation segmentation(CAS) process respectively. And the use of CAI process with single coal to prepare activated carbon products. Compared with the yield rate and the main indexes of activated carbon samples, the pore structure and surface chemical characteristics of activated carbon are correlated with the denitrification, and the results show that: the yield rate of activated carbon prepared by CAI process is significantly higher than that of the comprehensive rate of CAS, and the abrasive resistance and compression strength of activated carbon samples are improved compared with the segmented process. The bulk density, abrasive resistance and compression strength of the activated carbon prepared from lignite and long-flame coal cannot meet the requirements of national standards. The SCR denitrification activity of activated carbon prepared from single coal is sorted as: weakly caking coal > anthracite > long flame coal > lignite. Activated carbon prepared from lignite and long flame coal has a high mesopore ratio, but the carbonization and activation yield are considerable low, and the surface functional groups are not developed, especially the low content of acid oxygen-containing functional groups on the surface which leads to the poor denitrification performance of SCR. The specific surface area and pore structure of activated carbon prepared by blending anthracite and weak coking coal are in between the parameters of the activated carbon preparation from single coal. The activated carbon prepared from coal blending has abundant surface functional groups, and the total concentration of acidic/basic sites is higher than that prepared from single coals. In particular, the concentration of acidic oxygen-containing functional groups is increased to promote the SCR denitrification performance of activated coke.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 13891K]

  • Application and prospect of coal-based activated carbon in O3-biological activated carbon of water purification process

    LI Xiuchun;China Coal Huali Energy Holding Co.,Ltd.;China Coal Huali Xinjiang Carbon Technology Co.,Ltd.;

    The intensification of water pollution and the improvement of water quality standards make the efficient and economic O_3-Biological Activated Carbon(O_3-BAC) drinking water advanced purification process has been more and more widely used. Based on O_3-Biological Activated Carbon process and purification mechanism, the role of coal-based activated carbon were discussed, and the key influencing factors of activated carbon for water purification were analyzed. Based on the production process of coal-based briquetted activated carbon, the research status of the pore regulation, the development trend of coal-based activated carbon in O_3-BAC water purification process was discussed. Activated carbon plays an adsorption, synergistic and biological carrier role in the O_3-BAC process, which has better purification effect on dissolved organic compounds(DOC), on odor and disinfection by-product(DBP). Flotation ratio, hardness, loading density and pore structure are the key indexes of activated carbon for water purification, Adjustable pore, high hardness, low flotation ratio, rough surface with high interception capacity of briquetted activated carbon, and on the scarce domestic raw material coal resources, it is expected to manufacture activated carbon products that can fully meet the stringent requirements of O_3-BAC process for composition performance index. Since it is still difficult to quantify and accurately regulate the pore structure of activated carbon by coal blending technology in actual production, the mixing technology of activated carbon in O_3-BAC filter is a feasible solution at present, which is worthy of further in-depth study. In addition, the existing activated carbon standard system does not yet fully cover all aspects of production and application. It is necessary to study and formulate standards stepping up for filter backwashing, service life of activated carbon and regeneration technical index.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 13989K]

  • Prediction and optimization of decoupled combustion parameters in fluidized bed air distribution based on multi-process model integration method

    DI Zichen;CHANG Chenggong;YANG Fengling;WU Haibin;CHENG Fangqin;Institute of Resources and Environment Engineering, Shanxi University;School of Environment,Tsinghua University;

    Circulating fluidized bed(CFB) has been widely used for the conversion of low-grade fuels such as gangue and sludge. In recent years, with the changes in the applications and requirements, extensive adaptive modifications have been made to the CFB. Accurate simulation and prediction of the combustion performance inside the fluidized bed can provide fundamental support for these modifications. A fluidized bed model based on thermodynamics and kinetics was constructed to address the complexity of current fluidized bed models and the difficulty of accurately predicting multiple parameters. The influence of fuel variation on the oxygen demand, as well as the variation of void fraction and temperature with bed height were calculated. By constructing the thermodynamic model, the theoretical oxygen demands for four types of coal gangue with carbon contents of 74.05%, 17.71%, 24.27% and 34.01% were predicted, with theoretical oxygen demand of 15.17, 4.00, 4.47 and 6.20 kg/h, respectively. The calculated results were related to fuel type and theoretical oxygen demand, which can assist in the design of parameters such as fan power and air volume. Furthermore, by embedding 10 RCSTR dynamic modules in series into the kinetic model, the key parameters, including void fraction, temperature, and gas distribution, for different bed layers were calculated, with the single-point parameter error of less than 15%. The classification and prediction of different types of static indicators can be achieved by the establishment of a multi process model fusion method, providing theoretical basis and design references for regulating parameters such as fluidized bed air flow rate and primary-secondary air inlet positions during fuel transformation.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 14958K]

  • Experiment of sulfur retention characteristics of fly ash in pulverized coal oxy-fuel-firing flue gas

    ZHANG Jian;CAO Ruijie;School of Environment and Architecture Engineering,University of Shanghai for Science and Technology;Shanghai Institute for Design and Research on Environmental Engineering;

    During the oxy-fuel combustion, rich CO_2 is produced in flue gas with varied SO_x concentration. In this paper, the characteristics of sulfur retention in fly ash from different coal in oxy-fuel combustion was studied. The SO_x absorption in fly ashes of six coals was tested on the high-temperature drop-tube furnace, in which the flue gas atmosphere set for oxy-fuel or air burning. The influencing factors were analyzed. The results show that the sulfur retention amount is very low in bituminous coal ash, which is related to the lack of alkaline earth metal(Ca, Mg) in bituminous coal ash. However, the sulfur retention of lignite ash is significant. The fixed sulfur efficiency is about 43% for lignite ash after air-firing, as compared with 60% after its oxy-fuel combustion. The sulfur absorption rate is much higher in oxy-fuel flue gas in 1 000 ℃ rather than in 800 ℃. The temperature window and reaction effect of fly ash sulfur fixation are consistent with the reaction of SO_2 oxidation to SO_3. Some alkaline earth metals have combined with Si or Al, etc., and these alkaline earth metals do not have sulfur fixation activity. SO_3 formation is effected by both catalytic effect of Fe_2O_3 and the sulfur-retention behavior in ash. Through both oxy-fuel combustion and dry scrubbing of Ca sorbent added together, it is promising to control SO_x emission deeply in furnace.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 22358K]

  • NOx emission model of 300 MW subcritical circulating fluidized bed unit

    LIU Chun;GAO Mingming;ZHANG Hongfu;ZHANG Guohua;YUE Guangxi;State Key Lab of Alternate Electric Power System with Renewable Energy Sources (North China Electric Power University);Department of Energy and Power Engineering,Tsinghua University;

    With the increasingly strict pollutant emission standards, SNCR has become a new technology widely used in circulating fluidized bed(CFB) units to reduce NO_x emissions. However, the difficulty of SNCR control will be increased due to the fluctuation of NO_x emission concentration during variable load operation of circulating fluidized bed units. Due to the variable load dynamic NO_x emission model study is less, and in order to the realization of the dynamic prediction of NO_x load change process of circulating fluidized bed unit, the article mechanism of NO_x formation and SNCR reaction mechanism inside the furnace was analyzed, with coal and air volume, injection amount of ammonia, as input parameters, such as bed temperature, and mathematical modeling methods were used to establish a NO_x dynamic emission model. Combined with the actual operation data of a 300 MW subcritical CFB unit, the dynamic simulation of different loads was carried out. The results show that the model can better fit the NO_x emission trend in the dynamic process. The average absolute errors between the calculated values of the model and the real values under 300 MW and 150 MW typical load conditions and variable load conditions are 3.5, 1.2 and 5.7 mg/m~3, respectively, with high accuracy, which can realize the real-time prediction of NO_x emission of CFB unit, with the predicted time of 4-5 min. Then, the open-loop step experiments of coal supply, air supply, urea flow and multi-variable under different working conditions were carried out. The experimental results show that the model can better reflect the dynamic characteristics of NO_x emission process. The results can provide reference for the optimization of ultra-low emission control of CFB units.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 19144K]

  • Experiment on ash-slag formation characteristics of weathered coal in fluidized bed combustion

    WANG Bo;WANG Qinhui;LU Xinyao;CHENG Leming;WU Yingchun;State Key Laboratory of Clean Energy Utilization,Zhejiang University;

    The high ash content and low calorific value of Shanxi weathered coal limit its utilization in combustion and electricity generation. Extraction and utilization of humic acid from weathered coal has been extensively studied, but few studies have been conducted on its ash formation characteristics. To study the ash-slag formation characteristics of the weathered coal, a small fluidized bed reactor was used as the main experimental device to conduct hot combustion tests on weathered coal under different coal particle size and combustion atmosphere. Balance, vibrating screen, muffle furnace, laser analyzer and X-ray diffraction analyzer were used to analyze the slag-ash ratio, particle size distribution and mineral contents, which revealed the differences in the ash-slag formation characteristics of weathered coal. The results show that with the increase of coal particle size, the particle attrition in the furnace is inhibited and the fly ash ratio decreases from 43.20% to 1.51%, and the production of Quartz, Mullite and Hematite content and the conversion of Kaolinite increase. The increase of oxygen concentration in flue gas promotes the conversion of Kaolinite and Pyrite into Quartz, Mullite and Hematite: as oxygen concentration increases from 0 to 5.16%, Quartz content increases from 41.21% to 51.13%, Mullite content increases from 7.24% to 21.42%, and the Hematite content increases from 6.81% to 23.32%. High ash and low calorific value weathered coal can achieve stable combustion in fluidized bed, and when the oxygen concentration of flue gas is between 3%-5%, 2-4 mm weathered coal can maintain high combustion efficiency and mineral conversion rate, which is conducive to the stable operation of the system and secondary utilization of ash-slag. The result can be used for the fuel-selection of circulating fluidized bed.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 20046K]

  • Effect of calcium based desulfurizers on rheological properties of sludge

    CHEN Chunrui;ZHANG Yuanyuan;ZHAO Peizhen;ZHAO Wenxin;WANG Pengcheng;JIANG Ping;YANG Fengling;State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources,Engineering Research Center of CO2Emission Reduction and Resource Utilization-Ministry of Education of the People′s Republic of China,Shanxi University;Shanxi Hepo Power Generation Co.,Ltd.;

    The improvement of sludge rheological properties is very important for large-scale resource utilization of high-moisture sludge. The effects of adding calcium desulphurizer such as limestone and calcium carbide slag on the rheological properties of sludge were systematically studied. The effects of limestone or calcium carbide slag ratio, particle size and shear time on the rheological characteristics of sludge were investigated by using a rotating rheometer. The results show that the apparent viscosity and shear stress of the mixture increase with the proportion of desulfurizer limestone or calcium carbide slag, and the rheological properties of the mixture change significantly when the proportion of desulfurizer is greater than 15%. The fluid changes from a yield pseudoplastic fluid to a Bingham fluid when the proportion of limestone is more than 15%. The apparent viscosity of the mixed paste decreases with the increase of shear time at the same shear rate, showing the phenomenon of shear thinning. The smaller the proportion of two desulfurizers is, the more obvious the shear thinning phenomenon is, and the apparent viscosity decreasing trend is more significant at the lower shear rate of 35 s~(-1). The analysis of desulfurizer mixed paste with the same proportion at the same shear rate is found that the apparent viscosity of the mixed paste with the particle size of 0-0.075 mm is greater, indicating that the smaller the particle size of the desulfurizer is, the more significant the effect on the rheological properties of the mixture is. The moisture content of the mixed paste can be reduced by pumping the sludge with calcium-based desulfurizer, and the desulfurization function can be played in the furnace after pumping into the furnace. The optimal proportion of desulfurizer is 15%-20%. This study provides theoretical guidance for sludge combustion utilization and optimal design of pumping scheme in circulating fluidized bed.

    2023 08 v.29;No.156 [Abstract][OnlineView][HTML全文][Download 27405K]



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