• Experimental study on premixed ammonia/air swirl combustion assisted by dielectric barrier discharge

    CHEN Lei;SHEN Jie;JIANG Yiman;WU Jin;CHEN Jiahuai;FANG Shidong;Institutes of physical Science and Information Technology,Anhui University;Hefei Institutes of Physical Science,Chinese Academy of Sciences;Institute of Energy,Hefei Comprehensive National Science Center;

    Ammonia is an efficient hydrogen carrier that is expected to become the next generation of carbon free fuel. However, its use is hindered due to the narrow combustion limit and high NO_x emission. Plasma is an efficient and low energy consumption method to enhence combustion, which has been widely used. A self-made ammonia/air premixed swirl combustion platform coupled with dielectric barrier discharge was designed and constructed. The changes of combustion limit, flame shape, O_2 and NO_x were studied. The limit of lean combustion is 0.75 and the limit of rich combustion is 1.1-1.2 without discharge. When the equivalent ratio is 0.9, the flame propagating speed is the fastest and the flame is the shortest. The flame fills the entire combustion chamber near the low/rich combustion limit. When the equivalent ratio is 1.05-1.10, NO emissions remain at a low level and NO_2 is not generated. When the equivalent ratio decreases from 1.05 to 0.75, the volume fraction of NO increases from 97×10~(-6 )(3.5% O_2) to 2 785×10~(-6)(3.5% O_2). As the equivalent ratio decreases, a small amount of NO is further oxidized to NO_2, and the volume fraction of NO_2 reaches 171×10~(-6)(3.5% O_2) at the equivalent ratio of 0.75. The dielectric barrier discharge significantly enhances the combustion reaction and inhibits the negative effect of flame quenching at the wall of combustion chamber. The O_2 decreases slightly and the combustion limit extends to 0.65-1.30. Simultaneously, NO_x generated from the equivalence ratio of 0.75 to 1.05 is reduced by 40%-45%. The mechanism of NO_x generated by ammonia combustion was analyzed and discussed. It is found that NO_x mainly comes from fuel. With the decrease of equivalent ratio, the concentration of O/H increases, the concentration of NH_i decreases, and the proportion of side reaction that produce NO increases, which is more conducive to NO_x generation. Discharge produces a large number of active free radicals, and the promotion of NO+NH_i and NH_i+NH_i by NH_i is an important reason for NO_x reduction. Ammonia combustion assisted by plasma can significantly expand the combustion limit and reduce NO_x, providing a new method for clean and efficient ammonia combustion.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 18019K]

  • Solid oxide fuel cell stack performance in integrated gasification fuel cell system

    BA Liming;XIONG Xingyu;YANG Zhibin;PENG Suping;School of Chemical & Environment Engineering,China University of Mining and Technology-Beijing;National Institute of Clean and-Low-Carbon Energy;School of Energy Power and Mechanical Engineering,North China Electric Power University;

    Integrated gasification fuel cell system is one of the important candidates for the next generation clean and high efficiency power generation technology. In order to avoid carbon deposition caused by the carbon monoxide disproportionation reaction of the coal syngas in the solid oxide fuel cell stack, it is necessary to humidify the syngas to a certain extent. A multi-physics multi-scale model of the solid oxide fuel cell stack was constructed based on alternative mapping method to analyze the performance of the stack under different humidification levels. After humidification, the water gas shift reaction rate in the stack increases significantly and interacts with the electrochemical reactions of hydrogen and carbon monoxide. The water gas shift reaction is relatively strong near the inlet of the cell flow channel in the stack, rapidly converting CO to H_2, and, supplementing the consumption of hydrogen in its electrochemical reaction. However, the increase of humidification degree will also reduce the Nernst potential of hydrogen and inhibit the electrochemical reaction rate of hydrogen near the inlet section of the flow channel. The partial pressures of carbon monoxide and hydrogen are close to equilibrium at a distance greater than 60 mm from the inlet of the flow passage, the water gas shift reaction is weakened, and the gas reaction rate is controlled by the electrochemical reaction. The H/O and C/O volume fraction ratio in the inlet section of the flow channel are both low, which is easy to occur carbon deposition. More than 50% humidification can significantly reduce the risk of carbon deposition in the stack. Humidification will also cause performance degradation of the stack. Under the conditions of syngas composition adopted in this paper, humidification of 100% will cause 4.65% performance degradation.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 28167K]

  • Direct carbon solid oxide fuel cells with fuels derived from Hami coal

    GU Xiaofeng;YAN Xiaomin;ZHOU Mingyang;TAN Kai;FAN Zidai;LIU Jiang;School of Environment and Energy,South China University of Technology;College of Chemistry and Chemical Engineering,Xinjiang Normal University;

    Conventional coal-fired power generation has the problem of limited conversion efficiency and serious pollution emissions. The chemical energy in coal can be converted into electricity through direct carbon solid oxide fuel cell(DC-SOFC) technology with high efficiency. The high concentration of CO_2 produced from the DC-SOFC is beneficial for following carbon capture, utilization, and storage(CCUS) process, which is a potential high efficiency and clean coal technology. There has been some previous work on using coal-based fuel in DC-SOFCs. However, the composition and structure of coals are complex, and there is a lack on investigating the effects of these factors on the performances of DC-SOFCs using coal-based fuels. To evaluate the feasibility of using coal-based fuels in DC-SOFCs, the key factors affecting the performances of DC-SOFCs using coal-based fuel were studied by comparing the DC-SOFC performance of raw coal, raw coal loaded with Fe catalyst, coke, and coke loaded with Fe catalyst using Xinjiang Hami coal as fuel, combining with EDS analysis of the fuels. The results show that Hami coal from Xinjiang can be used as the fuel of DC-SOFCs. The DC-SOFC using 5% Fe-loaded coke as the fuel shows the best output performance, with a peak power density of 255 mA/cm~2 at 850 ℃. Meanwhile, the DC-SOFC fueled by coke shows the best fuel utilization efficiency, with a carbon conversion efficiency of 95% at a constant current of 200 mA under 850 °C. Obviously, Hami coal is the promising fuel of DC-SOFC, especially when the coal is carbonized and to load a certain amount of Fe catalyst after coalification as fuels, the cell has the better output performance and high utilization rate.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 20905K]

  • Recent research progresses of mathematical modeling and simulation of solid oxide fuel cell/gas turbine (SOFC/GT) hybrid systems

    LIAN Yanke;MING Pingwen;CAI Liming;School of Automotive Studies,Tongji University;

    Anode of solid oxide fuel cell(SOFC) can take internally reforming reaction due to the high operating temperature, which provides high fuel flexibility. The SOFC can also be combined with gas turbine(GT) to form a hybrid power system to further improve performance efficiency. The SOFC/GT hybrid system can be operated with bottom or top cycle. Considering the limited demonstration projects and high construction costs of SOFC/GT, mathematical modeling and simulation methods are generally used to carry out SOFC/GT related research work. Different from separate SOFC or GT models, thermodynamic modeling and simulation studies are often conducted to analyze and optimize the performance of SOFC/GT systems. In this paper, the commonly applied thermodynamic modeling approaches of SOFC/GT hybrid system were first introduced and summarized. Following that, the common steady state and dynamic thermodynamic modeling work for SOFC/GT hybrid systems at present were reviewed. Considering that commercial software(Aspen Plus, COMSOL, gPROMs) is commonly used for modeling SOFC/GT hybrid systems at this stage, and the modeling functions are limited and not easy to expand, open source code programming can be performed based on Matlab, Python and other software. At the same time, the analysis mainly focuses on SOFC/GT lumped models, which cannot accurately describe the local characteristics of fuel cells. One-dimensional or even higher dimensional SOFC models can be introduced into SOFC/GT modeling to further improve modeling accuracy.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 5235K]

  • Numerical simulation of carbon deposition in solid oxide fuel cells

    WANG Yinan;WANG Yuqing;ZHANG Ruiyu;LI Xiaoxiao;SHI Yixiang;School of Mechatronical Engineering,Beijing Institute of Technology;Department of Energy and Power Engineering,Tsinghua University;

    Fuel flexibility is one of the most significant advantages of Solid Oxide Fuel Cell(SOFC). However, when using hydrocarbons as fuel, the degradation of cell performance caused by anode carbon deposition is one of the most important reasons affecting the long-term stable operation of SOFC. To investigate the mechanism of the influence of anode carbon deposition on cell performance, a one-dimensional transient elementary reaction kinetic model of an SOFC fueled with syngas(H_2,CO,H_2O,CO_2,CH_4) was developed. This model incorporates the coupling effect of heterogeneous elementary chemical and electrochemical reactions, the electrode microstructure evolution, the charge and mass transport processes and the detailed evolution reaction of surface adsorbed carbon. The accuracy of the model was verified using the electrochemical impedance spectra at different moments in the reference experiment, and the mechanism of carbon deposition at SOFC anode was proposed based on the model. Under high temperature(>1 000 K) conditions, carbon is coverd on the Ni surface and Ni/YSZ/gas three-phase interface in the form of thin-film carbon, blocking the nonhomogeneous phase reaction and charge transfer reaction. At lower temperatures(<1 000 K), film carbon evolves into solid carbon, which grows inside the porous anode, blocking the anode pores and impeding gas diffusion. The constructed model can reflect this mechanism. Finally, the SOFC performance degradation due to carbon accumulation in different fuel components was investigated using the model. Study show that reducing the CH_4 content in the fuel can effectively reduce the performance degradation rate of SOFCs and improve its operational performance.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 18418K]

  • Design and operation characteristics study of integrated coal gasification fuel cell power generation and methanol cogeneration system

    SUN Shaodong;LI Zhi;YUAN Benfeng;LI Yan′an;LIU Yun;LIU Xin;LU Wenxue;ZHANG Zhiwei;LI Chengxin;State Key Laboratory for Mechanical Behavior of Materials,School of Materials Science and Engineering,Xi′an Jiaotong University;National Engineering Research Center of Coal Gasification and Coal-based Advanced Materials,Shandong Energy Group Co.,Ltd.;Shanghai Institute of Applied Physics,Chinese Academy of Sciences;

    Based on the actual coal chemical system, the research on the coupling technology of coal gasification chemical industry, solid oxide fuel cell and gas turbine is a new idea to accelerate the engineering and commercial development of IGFC. The Inner Mongolia Rongxin Chemical multi-nozzle opposed coal water slurry gasification and methanol production system of Shandong Energy Group Co., Ltd. was designed to carry out the construction of coal gasification chemical engineering, solid oxide fuel cell, and turbine process flows by Aspen Plus, a chemical process analysis software. The effects of operating parameters on the integrated coal gasification fuel cell power generation and methanol co-generation(IGFC-PMC) system were studied by simulation calculation, and the chemical output, power and thermal output of the system under typical conditions were analyzed. On this basis, the influences of key parameters of gasifier on output, efficiency and other operating parameters of key components were analyzed. The results show that the methanol production unit combined with fuel cells can improve the overall efficiency of the system from 57.71% to 59.22%, indicating that the new system has advantages in energy utilization efficiency. When the concentration of coal water slurry increases from 55% to 60%, there is the greatest influence on the power and efficiency of fuel cells and little improvement on the overall efficiency. The efficiency of fuel cell increases from 42.46% to 68.42%, the power increases from 2.65 MW to 4.22 MW, and the power of turbine 1st increases from 6.23 MW to 6.56 MW. When the proportion of pumping gas increases from 0 to 51.59%, the impact on methanol production is small because the pumping volume is less than 2% relative to the total amount of syngas. In addition, the overall efficiency increases from 59.20% to 60.70%. It is feasible to adjust the supply of "chemicals, heat and electricity" by extracting part of the purified gas. It is suggested to expand the generator set by setting parallel standby units, so as to reduce the difficulty of operation regulation and maintain the high efficiency of fuel cells. The optimized design of the original methanol production system not only improves the overall energy efficiency of the system, but also realizes the transformation from a single output chemical and waste heat to the combined supply of chemical, heat and electricity, providing a new idea for chemical system to relieve the pressure of production electricity and product diversity and economic optimization.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 7310K]

  • Development and performance test of molten carbonate fuel cell reactor

    ZHANG Ruiyun;HAN Minfang;LU Chengzhuang;YANG Guanjun;HUANG Hua;WANG Ju;WANG Jinyi;State Key Laboratory of Efficient and Flexible Coal Electricity and Carbon Capture,Utilization and Storage,Huaneng Clean Energy Research Institute Co.,Ltd.;Department of Energy and Power Engineering,Tsinghua University;

    The preparation method of large-area molten carbonate fuel cell matrix and electrode was developed, and the assembly and test operation method of 10 kW level molten carbonate fuel cell stack was proposed in view of the difficulties in the preparation and matching characteristics of the key materials during the development of large-area molten carbonate fuel cell and its large power stack. A 10 kW class MCFC stack with 120 cells and an effective area of 0.2 m~2 for each cell was assembled and operated. During the constant voltage discharge test, the maximum output power reaches 16.51 kW and the current density is above 95 mA/cm~2. Through multiple experimental studies and analysis, an effective online evaluation method for the baking effect of MCFC electrolyte matrix is obtained, which makes the matrix, electrode and molten salt electrolyte in the molten carbonate fuel cell body matched well, and has important guiding significance for improving the success rate and the long cycle operation life of MCFC stack assembly. Meanwhile, the study of MCFC stack body and performance test methods will provide effective theoretical and experimental guidance for the subsequent development of larger power molten carbonate fuel cell power generation system, and have important significance in the commercial demonstration and promotion of MCFC.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 21322K]

  • Research status and development prospect of solid oxide electrolyzer cells materials

    WANG Aoxue;GUO Lin;ZHENG Jinyu;MI Wanliang;ZHANG Panpan;YANG Zhibin;SINOPEC Research Institute of Petroleum Processing;School of Chemical &Environmental Engineering,China University of Mining and Technology-Beijing;

    Hydrogen has the advantages of high energy density, clean and pollution-free, and is considered to be the most suitable strategic energy for low-carbon development. Electrolysis technology can be used for the conversion and storage of renewable energy such as solar energy and wind energy, which can convert electrical energy into chemical energy for the synthesis of hydrogen. Common electrolytic water technologies include alkaline water electrolysis(AWE), polymer electrolyte membrane(PEM) and solid oxide electrolysis cell(SOEC). SOEC has high efficiency and does not require the use of precious metal catalysts, making it the first choice for efficient large-scale hydrogen production. SOEC operates at high temperatures, requiring the materials used to have high conductivity and stability at high temperatures. At the same time, the materials used for different components should match the thermal expansion coefficient and have good compatibility. Therefore, the research status of cathode materials, anode materials and electrolytes in SOEC were summarized. The cathode materials are mainly metal ceramics and perovskite-type ceramics. The high temperature and humidity environment of the cathode can easily lead to the deactivation of cermets, and there are problems such as oxidation, loss, and agglomeration of metals during long-term operation. Therefore, the factors that led to the deactivation of metal ceramics were described, and the methods to improve the stability were discussed. The problems of low ionic conductivity and catalytic activity of perovskite-type materials were briefly described, and the methods to improve the properties of materials were introduced, such as doped transition metal in situ dissolution, loaded active metal nanoparticles, etc. Anode materials are mainly perovskite materials. The factors affecting the decline of neutral energy of anode operation were described, such as delamination, cracks, and other issues that lead to poor long-term stability of anode materials during long-term operation. The methods to improve anode durability were discussed, such as adding barrier layer, circulating operation, and preparing perovskite materials with high conductivity and catalytic activity. Electrolyte materials are mainly composed of fluorite-type or perovskite materials. Two methods of preparing high conductivity materials and thin-film process were introduced to reduce their impedance. Although SOEC is still considered to be in the stage of laboratory research and development, its electrolytic performance has been significantly improved with the continuous deepening of research on SOEC. Developed countries such as the United States, the European Union are laying out the commercial application of SOEC. The commercial application prospect of SOEC was discussed and prospected from the aspect of materials.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 6387K]

  • Simulation of the effect of flow channel structure on the performance of PEM electrolyzer

    WANG Hua;MA Xiaofeng;HE Yong;XU Chaoqun;ZHU Yanqun;WANG Zhihua;Zhejiang Fuxing Shipping Co.,Ltd.;State Key Laboratory of Clean Energy Utilization,Zhejiang University;

    In order to improve the performance of proton exchange membrane(PEM) electrolyzer, reduce the voltage loss, and enhance the operational stability, a three-dimensional model of a full-size multi-channel PEM electrolyzer was established using Comsol software under certain assumptions. the simulation calculation results were compared with the experimental test results of the same size PEM electrolyzer in the literature to verify that the simulation results were basically consistent with the experimental test results in the literature. The effects of runner height, blocking and ridge width on the performance of PEM electrolyzer were investigated to optimize the flow field structure based on this electrolyzer model. The simulation results show that the optimal flow channel height is 2 mm under the PEM electrolyzer size set in the study. The oxygen mass fraction in the diffusion layer can be reduced by about 2.6%, the average temperature of the membrane electrode can be reduced by about 2.2 K, and the electrolytic potential of the electrolyzer can be reduced by about 0.023 5 V by setting the block at the top of the flow channel. When the width of the ridge of the flow field is reduced from 2 mm to 1 mm, the average oxygen mass fraction is decreased by about 8.7%, the average temperature of the membrane electrode is decreased by 6.21 K, and the electrolytic potential of the electrolyzer is decreased by about 0.04 V. The optimized flow field structure is conducive to take away oxygen in the diffusion layer for circulating water, and reduce the possibility of oxygen bubbles blocking the pores of the diffusion layer, reduce the mass transfer resistance, and enhance the heat transfer process to discharge the excess heat from the electrolyzer in time, reduce the electrolytic potential of the electrolyzer, and improve electrolyzer performance and operational stability.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 10512K]

  • Na catalyst deactivation and Na-Al reaction and transformation behaviors during catalytic gasification

    MEI Yangang;GAO Songping;ZHANG Qian;Department of Chemistry and Chemical Engineering,Taiyuan Institute of Technology;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;

    Catalytic gasification is a new type of coal gasification method, and the catalysts used in catalytic gasification are usually alkali metals. However, in catalytic gasification process, alkali metal catalysts react with Si and Al minerals in coal, directly affecting the catalytic activity of alkali metal in catalytic gasification. The deactivation behaviors of alkali metals and Na-Al reaction and transformation during catalytic gasification with Na_2CO_3 addition was studied. Kaolinite and boehmite were used as model compounds to study the Na-Al reaction and conversion process, and the catalytic effects of Na-Al conversion products were compared. The study shows that Na_2CO_3 has good catalytic effect. During catalytic gasification, Na_2CO_3 reacts with Si and Al minerals in coal to form nepheline and sodium aluminosilicate, resulting in catalyst deactivation. Kaolinite reacts with Na_2CO_3 at 700 ℃ to form sodium aluminosilicates, and boehmite reacts with Na_2CO_3 at 860 ℃ to form NaAlO_2, which is unstable at higher temperature and is converted into sodium aluminosilicates. Compared with Na_2CO_3, the catalytic effect of sodium aluminosilicates and NaAlO_2 is poor, resulting in the deactivation of Na_2CO_3, and the catalytic effect of NaAlO_2 is better than that of sodium aluminosilicates.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 18076K]

  • Study and demonstration of H_2/CO_2 separation of syngas from coal by elevated temperature pressure swing adsorption

    LI Shuang;ZHANG Jing;WANG Dongdong;WANG Lu;SHI Yixiang;CAI Ningsheng;Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,Department of Energy and Power Engineering,Tsinghua University;Shanxi Research Institute for Clean Energy,Tsinghua University;

    Purification section of syngas from coal is located after water gas shift to remove hydrogen sulfide, carbon dioxide as the main gas impurities and obtain high purity hydrogen. At present, the mature purification processes include wet method represented by low temperature methanol scrubbing and liquid nitrogen scrubbing, and dry method represented by pressure swing adsorption decarburization. The operating temperature of the elevated temperature pressure swing adsorption technology proposed is consistent with the temperature of the incoming shift gas. Self-made hydrophobic nitrogen-rich activated carbon adsorbent was deployed to achieve desulfurization and carburization by increasing the traditional pressure swing adsorption operating temperature to 170-220 ℃ and high humidity environment. Two new PSA steps, high pressure steam rinse and low pressure nitrogen purge, were adopted to improve H_2 recovery to above 99%. The elevated temperature pressure swing adsorption H_2/CO_2 separation demonstration with a processing capacity of 5 000 m~3/h(standard condition)was built and operated using coal based shift gas from Quanji Plant as the feedstock for the pilot plant. The purity of hydrogen reaches the hydrogen fuel level(including N_2) through two-stage ETPSA, and the pilot plant has been running for more than 2 800 hours in total. In addition, the energy consumption of the pilot plant was calculated based on the utilities expenses. When taking power consumption into consideration, the operation cost of H_2 purification for the pilot test can be significantly reduced by about 35% compared with the power consumption of H_2 purification by low temperature methanol scrubbing at Fengxi Plant. This technology breaks through the limitation of temperature of conventional adsorption and purification for solid adsorbents, and realizes directional removal of impurities in hydrogen by using adsorbents with preferred selective adsorption performance at elevated temperature, which confirms a new process route for efficient and high-quality hydrogen purification.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 8199K]

  • Review on hydrogen liquefaction and cryo-compression hydrogen storage technologies

    WANG Haocheng;YANG Jingyao;DONG Xueqiang;GONG Maoqiong;Key Laboratory of Cryogenics,Technical Institute of Physics and Chemistry,Chinese Academy of Sciences;University of Chinese Academy of Sciences;

    Hydrogen is an important clean and carbon-free secondary energy carrier in the future due to its extensive source, clean and carbon free, which will play a significant role in the world energy pattern. Hydrogen cryogenic densification technology can greatly improve hydrogen storage density and effectively solve the problems in large-scale storage and transportation caused by the low density and low boiling point of hydrogen. The developments of two cryogenic hydrogen storage technologies, hydrogen liquefaction and cryo-compressed hydrogen, were reviewed in this paper. The performance and characteristics of various cryogenic densification processes were introduced and compared, and the future development directions were summarized, providing a reference for the development of hydrogen storage and transportation technologies. Hydrogen liquefaction can achieve high hydrogen storage density with low hydrogen storage pressure, which is one of the mainstream large-scale hydrogen storage and transportation method at present. Cryo-compressed hydrogen could also reach a high storage density near liquid hydrogen with advantages of low intrinsic energy consumption and free of ortho-to-para hydrogen conversion, which has great development potential. Besides, closed refrigeration cycles such as mixed-refrigerant J-T cycles can effectively replace liquid nitrogen in the precooling or cooling hydrogen, which can significantly reduce the energy consumption of hydrogen densification and is an important development trend of cryogenic hydrogen storage technologies.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 42808K]

  • Improving ash fusibility and gasification reactivity of anthracite based on coal blending technology

    XIE Ying;WU Chengli;LIU Tao;CHEN Hejing;LI Hanxu;School of Chemical Engineering,Anhui University of Science and Technology;Engineering Technology Research Center of Coal Resources Comprehensive Utilization of Anhui Province;

    To improve the ash melting and gasification reactivity of anthracite coal, a Jincheng anthracite coal(JC) and Indonesian lignite coal(YN) were selected as raw materials, and the effects of YN coal addition on the ash melting temperature, gasification activity, microcrystalline structure, specific surface area and total pore volume of coal char were investigated by using ash melting tester, TGA, XRD, BET and other analytical test methods. The results show that the ash melting temperature of JC coal could be effectively reduced by adding YN, and the flow temperature T_F decreases to 1 387 ℃ when the addition amount reaches 40%, and the coal char reactivity is also obviously improved, and the time required to reach 50% carbon conversion t_(0.5) is only 27.2 min when YN is added at 40%, which is about half of that of JC coal char, and there is a good linear relationship between the reactivity index R_(0.5) and the alkalinity factor B_f. The XRD data of coal char are also fitted and found that the layer spacing d_(002), aromatic lamellae stacking height L_c, aromaticity f_a, and number of aromatic layers N decreases with the addition of YN, and the addition of YN makes the microcrystalline structure of coal char more disordered, and the greater the addition ratio, the greater the degree of graphitization inhibition. The specific surface and total pore volume of coal coke are correlated with the addition of YN, and when 40% is added, the specific surface area could reach 81.102 m~2/g about 42 times that of JC, and the total pore volume is one order of magnitude higher than that of JC.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 13849K]

  • Review of manganese based catalysts for catalytic removal of NO_x and CO at low temperature

    XUAN Chengbo;ZHANG Xingyu;WANG Luyuan;ZHAO Tiantian;HAN Shiwang;CHEN Zhengxin;LIU Qianqian;WANG Xuetao;School of Energy and Power Engineering,Qilu University of Technology;Energy Research Institute of Shandong Academy of Sciences,Shandong Academy of Sciences;Transportation Engineering School,Henan University of Science Technology;

    NO_x and CO are the key pollutants to be treated. With the further improvement of flue gas emission standards such as steel sintering, the traditional NH_3-SCR(NH_3 selective catalytic reduction of NO_x) denitration technology has significant shortcomings, especially the sintering flue gas emission temperature is lower than the window temperature of vanadium based catalysts, causing that the activity of vanadium based denitration catalyst is insufficient and the generated ammonium sulfide blocks the catalyst surface, but there is still a lack of effective means for CO control. Therefore, the development of low-temperature catalyst has become the key factor for removing NO_x and CO from low-temperature flue gas. The progress of Mn based catalyst in removing NO_x and CO was discussed, the effects of active components, preparation methods and supports on the catalytic activity of Mn based low-temperature catalyst were compared, and the effects of Cu、Ce and other metals on the modification of Mn based catalyst were introduced in detail, and the relationship between element doping and catalytic performance was analyzed. On this basis, the latest research results of no reduction technology by CO in recent years were systematically combed and summarized, and the reaction mechanism and the action mechanism of O_2 in the reaction were emphatically discussed. The results show that the rich extranuclear electron arrangement of Mn element is the fundamental reason for its excellent activity in removing NO_x and CO, but most of the current research results are only in the laboratory theoretical stage and lack of large-scale verification in the actual flue gas. Finally, the future development direction of Mn based catalyst was prospected, and the catalyst deactivation mechanism and the scheme to improve the anti poisoning of catalyst were put forward.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 11264K]

  • Migration mechanism of AAEM and the causes of slagging and contamination during pulverized coal combustion

    DI Yi;NIU Fang;WANG Naiji;ZHOU Jianming;China Coal Research Institute;Beijing Tiandi Rongchuang Technology Co.,Ltd.;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

    The fly ash leads to slagging and fouling in the furnace and flue, and the ash particle sticking behavior will be affected by Alkali and Alkaline Earth Metals(AAEM) rich in coal. In order to reduce the threat of molten, sticky ash particles adhering to heat exchanging surfaces, the occurrence form and transformation characteristics of AAEM in the combustion process were analyzed, the influence of AAEM steam condensation on the characteristics of fly ash was discussed, and the deposition mechanism of fly ash sticking on the heat exchange surface was analyzed. The results show that the difference of combustion temperature and occurrence form of AAEM leads to different released processes and amount. The increase of temperature will promote the release of AAEM. With the decrease of the solubility of AAEM in the extract, it will be more difficult to release AAEM during combustion.The AAEM released into the gas phase then heterogeneous condenses on the heat exchange surface or ash particles surface to form a sticky layer, which increases the capture efficiency of fly ash on the heat exchange surface, homogeneous condenses in the gas phase to form aerosols, and aerosols as precursors form sub-micron particles in the subsequent coalescence process. The deposition of fly ash is affected by many factors, such as molecular diffusion, Brownian motion, eddy impaction, thermophoresis, gravity sedimentation, inertial impaction and so on. Gravity sedimentation and inertial impaction mainly affect the trajectories of large ash particles, while other factors mainly affect the trajectories of small particles.The deposition layer have a layered structure. The formation of the inner layer is mainly caused by inorganic steam condensation and small particle impaction, and the outer deposition layer is mainly formed by large particle impaction. The fly ash adhered to the heat exchange surface affects the thermal efficiency of the boiler, corrodes metal at high temperature, and buries hidden dangers for the safe and stable operation of the boiler. Therefore, many scholars have proposed pulverized coal washing or mixed combustion, soot-blowing, coating of heat exchange surface and structural improvement of furnace to slow down the deposit formation. However, due to the changeable components in coal, it is difficult to predict the slagging and fouling behavior perfectly. It is necessary to strengthen the research on the elements with different occurrence forms, deposition of different forms of fly ash and the complex physical-chemistry reactions in the formation process of fly ash, so as to provide theoretical support for the prevention and control of slagging and contamination.

    2023 03 v.29;No.151 [Abstract][OnlineView][HTML全文][Download 15940K]