2024年05期目次

  • Carbon footprint analysis of China′s ammonia energy production-storage-transportation-utilization full-chain for different application scenarios

    WANG Minghua;CHEN Zeyu;WANG Wen;REN Lei;LIU Jianzhe;OU Xunmin;CHN Energy Economic and Technological Research Institute Co.,Ltd.;Institute of Energy,Environment and Economy,Tsinghua University;

    Ammonia energy is a widely used, green and low-carbon new type of clean energy, which has outstanding advantages over hydrogen energy in terms of safety, energy intensity, easy-to-storage and transport, and many other aspects. The application of ammonia energy in transportation, power, chemical and other sectors in China is still in its infancy, but the related carbon footprint research has received much attention. This study conducted a step-by-step life cycle carbon footprint analysis of China′s ammonia energy′s full industrial chain under application scenarios such as hydrogen refueling stations, ammonia fuel supply stations, and power plants, and focus on analyzing the carbon emission level of ammonia energy used in the scenario of transportation fuel and power sector. The research results show that, from the perspective of different technology routs, in all scenarios, the carbon dioxide emissions of ammonia energy in the whole life cycle of the electrolyzed water hydrogen production HB(Haber Bosch process) synthetic ammonia liquid ammonia vehicle route are the highest, more than 600 g/MJ. Hydrogen production from renewable energy electrolyzed water-HB synthetic ammonia-pipeline transmission route has the lowest carbon dioxide emission in the whole life cycle of ammonia energy, which is lower than 40 g/MJ. For each stage, the fuel production stage accounts for the highest proportion of carbon footprint in all stages of production, storage and application of various ammonia production technology pathway, except for the renewable energy electrolysis ammonia production pathway. From the perspective of influencing factors, the power consumption level and its carbon emission factor in each stage of hydrogen production, ammonia generation and ammonia cracking for hydrogen production play an important role in the carbon footprint of the whole industrial chain of ammonia energy production, storage and utilization. From the perspective of application scenarios, in the scenarios of chemical plants, steel plants, and power plants, due to the short transportation distance and low energy consumption for storage and transportation, the carbon dioxide emissions throughout the full life cycle of 1 MJ ammonia energy are relatively low. From the perspective of application scenarios, in the field of transportation, the green ammonia and blue ammonia technology pathway has the advantage of significantly reducing the carbon footprint(more than 80%) compared with traditional petroleum fuels.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1880K]

  • Progress and prospects in the chemical looping ammonia synthesis

    WANG Runze;FENG Sheng;WANG Yawei;GAO Wenbo;GUO Jianping;CHEN Ping;Dalian Institute of Chemical Physics,Chinese Academy of Sciences;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences;

    Ammonia is mainly used as a raw material for the production of nitrogen fertilizers. In recent years, it also has been seen as a promising energy carrier. Industrial ammonia synthesis is mainly based on the Haber-Bosch(H-B) process requiring a significant energy input, so it relies severely on fossil energy and leads high CO_2 emissions. Therefore, there is an urgent need to develop "Green ammonia synthesis" process driven by renewable energy operating under mild conditions. Chemical looping ammonia synthesis(CLAS) is a process that decouples the ammonia synthesis reaction into multiple sub-reactions mediated by an intermediate N carrier material. It has the advantages of circumventing the ubiquity scaling relationships, avoiding the competitive adsorption between N_2 and H_2(or H_2O), and being able to operate at atmospheric pressure. In addition, this process is suitable to distributed and small-scale ammonia synthesis and is easy to couple with the utilize of renewable energy. Therefore, CLAS has received widely attention in recent years. This review was initiated by briefly defining chemical looping processes and summarizing the research of chemical looping in the area of fossil fuel conversion. The history of CLAS, the development of nitrogen carrier materials, and some recent progresses were then reviewed. The discussion was concluded with future perspectives on the design of nitrogen carrier materials and the prospective advancements in CLAS. The binary metal nitrides, multi-metallic nitrides, metal imides, and metal nitrides, which were used as nitrogen carrier materials in N_2-H_2 and/or N_2-H_2O CLAS, were presented. Additionally, the CLAS process assisted by external energy such as electricity, light, plasma, and microwaves was discussed. Strategies to enhance the thermodynamic and kinetic performance of nitrogen carrier materials were also detailed. Finally, the review addressed current challenges and emerging research directions in chemical looping ammonia synthesis.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1960K]

  • Characteristics and mechanism of chemical looping ammonia generation by chromium-doped aluminum-based N-carrier

    WU Jin;JI Zhengang;WU Ye;LIU Dong;School of Energy and Power Engineering,Nanjing University of Science and Technology;

    Aluminum-based nitrogen carriers for chemical looping ammonia generation represent a novel technique with promising potential for the efficient production of ammonia and the clean utilization of carbon-based energy sources like coal. However, at the temperatures requisite for nitridation reactions, the aluminum-based nitrogen carriers inevitably transform into α-Al_2O_3, which possesses lower activity and adversely affects the efficiency of ammonia synthesis. To address this issue, a series of Cr-doped CA-x%(x=0, 2.5, 5.0, 7.5, 10.0) nitrogen carrier samples were prepared using the co-precipitation method for the study of their characteristics in chemical looping ammonia synthesis reactions. XRD and XPS analyses confirm that Cr atoms are uniformly doped into the Al_2O_3 lattice, enhancing its oxygen activity. When the five nitrogen carrier samples were tested in nitridation-ammoniation reactions, the CA-5% sample demonstrated superior ammonia synthesis performance, with an ammonia yield approximately 3 times higher than that of the undoped counterpart. The inclusion of Cr also facilitates both nitridation and ammoniation reactions. Utilizing Material Studio software to construct a model for the nitridation reaction of the nitrogen carrier, analysis of the computational results reveal that Cr doping significantly reduces the formation of CO during the nitridation process and the energy barrier for the dissociative adsorption of N_2. After Cr incorporation, the stability of lattice oxygen in Al_2O_3 decreases, rendering oxygen atoms more prone to dissociate from the surface of the nitrogen carrier and to react with N_2 to form aluminum nitride. Finally, repeated nitridation-ammoniation reaction experiments conducted with CA-5% nitrogen carrier affirm the cyclic stability of Cr-doped aluminum-based nitrogen carriers.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1910K]

  • Configuration analysis of renewable power to ammonia system

    GONG Siqi;YANG Yang;LI Chufu;BAI Zhuqia;SUN Haozhe;ZHANG Xiaofang;XU Ming;National Institute of Clean and Low-Carbon Energy,Beijing;Guohua (Ningxia) New Energy Co.,Ltd.;Guohua Energy Investment Co.,Ltd.;

    Combining hydrogen production from renewable energy with traditional chemical processes to achieve electric-hydrogen-chemical coupling can not only improve the utilization of renewable energy, but also facilitate the green and low-carbon transformation of chemical processes. Aiming at the contradiction between the fluctuation of renewable energy and the stability of chemical process in electric-hydrogen-chemical coupling system, an optimal configuration model was established, including large-scale wind-solar complementary power generation, hydrogen-storage, and ammonia synthesis system. The influence of key parameters such as wind-solar ratio, hydrogen production capacity, minimum hydrogen production load and hydrogen storage tank volume on system operation was studied, the instantaneous operation characteristics of the system throughout the year was analyzed. The results show that when the wind-solar ratio is around 8∶3 and the hydrogen production capacity is close to the wind-solar average output power, it is more likely to reduce the grid supply under the smallest storage tank volume. The decrease of the minimum load of hydrogen production and the increase of the volume of the storage tank are conducive to the increase of the stability of the system and the decrease of the grid power supply, which was expected to realize the pure green power operation of the system. When the system parameters are configured as the wind-solar ratio of 8∶3, the hydrogen production capacity of 400 MW, the minimum hydrogen production load of 20% and the hydrogen storage tank volume of 100 000 m~3, the annual average grid power supplement ratio is about 5%. The simulation results of 8 760 h system operation show that the regulation of hydrogen production load can slow down the system fluctuation. And then ammonia synthetic equipment can continuously operate in the range of 50%-110% with hydrogen storage tank buffer.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1697K]

  • Application and prospect of ammonia fuel in combustion facilities

    ZHANG Ruifang;ZHANG Yang;ZHANG Hai;Key Laboratory of Thermal Science and Power Engineering of Ministry of Education,Department of Energy and Power Engineering,Tsinghua University;

    In the strategical context of carbon neutrality, ammonia(NH_3), as a carbon-free fuel, has attracted great attention by the academic communities and industries. In recent year, extensive studies are conducted on the associated combustion fundamentals. In the same time, several application researches and engineering demonstrations to burn NH_3 in various industrial devices were carried out. Research progress of NH_3 fuel utilization in coal-fired boiler and other combustion facilities were reviewed, and measures taken to resolve the two issues for NH_3 combustion, i.e., the weak stability and high NO_x emission were focused on. In addition, some prospects in future research were given. Strategical analyses show that for carbon neutrality, NH_3 has certain economic advantages over hydrocarbon fuels such as natural gas. NH_3 can be mixed with existing fuel or active fuels such as H_2 and methane to increase combustion intensity, and can even be solely burned through preheating, catalytic decomposition, and oxygen enrichment measures. The most common and effective method to reduce NO_x in industrial devices is air-staged combustion. NH_3 combustion in IC engines is prone to stable, but NO_x emissions are relatively high. Therefore, NO_x emission reduction is a key focus of future work. The application research of NH_3 fuel in gas turbines mainly focus on numerical simulation and a few small-scale gas turbine tests. Stable and low NO_x emission have been achieved, but research on large-scale gas turbines is still lacked. The application research on NH_3 fuel utilization in boilers focus on the co-combustion of NH_3 with pulverized coals. China is active in NH_3-coal combustion research, has recently conducted industrial tests on a 300 MW coal-fired boiler with a maximum NH_3 to coal calorific ratio of 35%. More research with larger NH_3 co-firing ratio are needed. Circulating fluidized bed(CFB) boilers are ideal NH_3 combustion device over the pulverized coal fired boiler, and attention should be paid in the future.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1417K]

  • Characteristics analysis of ammonia/coal co-firing with air staged combustion in one-dimensional self-sustained combustion experimental furnace

    WANG Xin;WEI Geng;WANG Yong;LI Weicheng;CHEN Jun;FAN Weidong;School of Mechanical Engineering,Shanghai Jiao Tong University;Clean Combustion and Flue Gas Purification Key Laboratory of Sichuan Province;Dongfang Electric Corporation Dongfang Boiler Co.,Ltd.;

    Previous studies on ammonia/coal co-firing have focused on numerical simulations and small-scale test furnaces, while large-scale test furnaces are mostly used for point-case tests of technical feasibility. In this paper, a detailed study of the emission and process distribution characteristics of ammonia/coal co-firing was carried out in a 50 kW one-dimensional self-sustained combustion experimental furnace under different operating conditions. In order to fully understand the contribution of ammonia and coal to NO production during the combustion process, a series of experimental studies were carried out for pure ammonia combustion. Air-staged combustion greatly reduces NO emissions from ammonia/coal co-firing combustion. With ammonia co-firing ratios ranging from 10% to 90%, NO concentrations varie from 170 to 215 mg/m~3, which are at the same level with pure coal combustion. The optimal burnout air ratio is maintained near 38%. Further increasing the burnout air ratio will not further reduce NO emissions, but will lead to negative effects such as inadequate combustion. Pure ammonia combustion employing air-staged combustion technology can manage the exported NO concentration, but its stability is significantly worse than that of ammonia/coal co-firing, and ammonia is prone to escape when the oxygen concentration in the operation is low. Ammonia/coal co-firing may not only solve the problems of ammonia combustion difficulties and excessive NO emissions, but it can also minimize CO_2 emissions from coal combustion, making it a very attractive technology route for future energy growth.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1558K]

  • Effects of high-alkali coal ash on NOx formation characteristics during ammonia and coal co-firing process

    ZHU Shenggang;YAO Xin;CUI Liming;LI Ming;ZHANG Su;JIANG Heqing;NIU Tao;TAN Houzhang;WANG Xuebin;Guodian Technology & Environment Group Cor.,Ltd.;MOE Key Laboratory of Thermo-Fluid Science and Engineering,Xi′an Jiaotong University;China Shenhua Energy Co.,Ltd.;Yantai Longyuan Power Technology Co.,Ltd.;

    Ammonia can be used as a zero-carbon fuel to replace part of coal for co-firing process, which can effectively reduce the original pollutant emissions of power plants and promote the transformation of coal-fired power plants to coal and ammonia co-firing power plants. However, due to the high nitrogen content in ammonia, the problem of NO_x emission has attracted much attention. In the complex coal and ammonia co-firing process, the correlation between NO_x emissions and coal ash is also worthy of further exploration and analysis. High-alkali coal in coal-fired power plants is a kind of coal with broad development prospects, but the emission characteristics of high-content metal oxides on ammonia oxidation reaction are rarely studied. In order to explore the influence of different kinds of high-alkali coal ash on the emission characteristics of ammonia oxidation reaction during the coal and ammonia co-firing process, an ammonia oxidation reaction test platform was built to analyze the variable working conditions, and the two indexes of NH_3 conversion rate and NO generation rate on the surface of various types of coal ash at different temperatures were compared. The specific influence of various metal oxides in coal ash on the emission characteristics of ammonia oxidation reaction was expounded from two aspects of test results and reaction mechanism. The results show that the main metal oxides CaO, MgO and Al_2O_3 in coal ash can promote the gas-solid ammonia oxidation reaction on the surface of coal ash during the coal and ammonia co-firing process, and improve the NH_3 conversion rate. At 400-600 ℃, the promoting effect of coal ash on the conversion rate of NH_3 is as follows: HM-2>HM-1>CJ>AKS>EERDS, which corresponds to the order of CaO content in coal ash from high to low, which is basically consistent with the order of MgO. In addition, the above three kinds of metal oxides can promote the directional conversion of NH_3 to NO, and the catalytic effect of CaO is the most significant. Among them, the selectivity of HM-2 with the highest Ca content to NO formation can be increased by 67.86% compared with the pure gas phase ammonia oxidation reaction. CaO and MgO can promote the oxidation of NH_3 and NO on the catalyst surface, which is conducive to the rapid production of N_2O the advance of N_2O formation temperature. However, the presence of Na_2O and Fe_2O_3 has an inhibitory effect on the oxidation reaction of NH_3, and it has excellent performance in promoting the reduction of NO by NH_3. Among them, the mechanism of Na_2O and Fe_2O_3 promoting NO reduction is not the same.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1251K]

  • Effect of staged air with a high-speed jet on ammonia pyrolysis and NOx formation in an ammonia-coal co-firing flame

    YU Ronghao;XU Yishu;WANG Huakun;HAN Jinke;XIE Zhicheng;ZHANG Kai;LIU Xiaowei;State Key Laboratory of Coal Combustion and Low Carbon Utilization,Huazhong University of Science and Technology;Jxic Energy Tech Research Institute Co.,Ltd.;

    As a zero-carbon clean fuel, ammonia plays an important role in carbon emission reduction, but its tendency of NO_x generation during combustion is large. To control NO_x formation during ammonia-coal co-firing, an improved ammonia doped cyclone burner structure with a built-in high-speed air jet array structure was proposed using a cyclone burner used in a 50 kW one-dimensional test furnace system as a prototype, in order to realize ammonia pyrolysis before combustion and air-staged combustion in the furnace. CFD combustion numerical simulation was further used to investigate the effects of air staged ratio, excess air coefficient and ammonia fuel nozzle size on the flame structure and NO_x emission of ammonia-coal co-firing, and to optimize the structure and operating parameters of the new combustor. The results show that compared with the prototype burner, the use of spatially dispersed high-speed tertiary air jets leads to lagging in the combustion zone, deepens the air staging, reduces the local excess air coefficient in the main combustion zone, and inhibits the excessive oxidation of ammonia to form NO_x, and also reduces the peak flame temperature, which is conducive to the inhibition of the formation of thermal NO_x. At the same time, by regulating the total excess air coefficient so that the ammonia pyrolysis occurs along the axial extension of the furnace, the high-temperature under-oxygenized zone in front of the flame increases, to promote the pyrolysis of ammonia into N_2 and H_2, and further reduce the ammonia direct conversion to form NO_x. At the air staged ratio of 20∶22∶58, the volume fraction of NO_x formed by the prototype burner of 3 309×10~(-6) decreases to 1 069×10~(-6) of the improved burner, a reduction of 67.69%. Increasing the excess air coefficient, or keeping the excess air coefficient constant and controlling the primary air ratio constant while increasing the tertiary air ratio will promote the above effect and further reduce NO formation. The variation range of the inner diameter of the ammonia tube is only 5-9 mm, and the synergistic effect of the ammonia injection rate and the dispersed high-speed tertiary air need to be further investigated.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1968K]

  • Influence of air jet characteristics on the pure ammonia-fuelled swirl diffusion flame

    XIE Zhicheng;XU Yishu;ZHANG Kai;YU Ronghao;HAN Jinke;LIU Xiaowei;State Key Laboratory of Coal Combustion and Low Carbon Utilization,Huazhong University of Science and Technology;Energy Technical Research Institute,Jiangxi Provincial Investment Group Co.,Ltd.;

    Ammonia is an ideal energy source, in order to make better use of pure ammonia fuel and develop a burner suitable for pure ammonia fuel, this study conducted 3D modelling of a 10 kWth natural gas swirl burner by numerical simulation, and simulated the combustion and NO emission performance of pure ammonia in it. The influence of air jet characteristics on the flame morphology, temperature distribution, NO generation and emission was explored, in order to optimize the pure ammonia combustion capability of the burner. In the early stage of combustion, the influence of swirl on the mixing of fuel and air is more significant, while in the late stage of combustion the turbulence intensity has a greater influence on the process. It was found that the swirl intensity could be enhanced by increasing the air jet hole area(from 12.8 mm~2 to 19.2 mm~2) and the air jet angle(from 15° to 30°), which could promote the mixing of fuel and air, and thus promote the rapid and stable combustion of ammonia fuel and shorten the ignition distance. However, too large jet angle may lead to a short separation of air and fuel, delaying the mixing process and prolonging the ignition distance. In addition, it was also found that decreasing the jet hole area and increasing the jet angle would also enhance the intensity of nearby turbulence near the combustor nozzle, which would promote the mixing and combustion of ammonia fuel and air, thus generating a localized high-temperature zone and leading to an increase in the concentration of NO generation. Through comparative optimization, the pure ammonia burner achieved stable low-NO combustion with air jet orifice area 19.2 mm~2, jet angle 15°, jet velocity 19.83 m/s, ignition distance 0.024 m, flame length 0.446 m, and the peak NO generation concentration and emission concentration were reduced to 443×10~(-6) and 37.7×10~(-6), respectively.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 2432K]

  • Preparation and electrochemical energy storage application of coal-based carbon materials

    LI Zhen;SHANG Yingze;ZHU Zhanglei;CHANG Jing;ZHAO Kai;School of Chemistry and Chemical Engineering,Xi′an University of Science and Technology;Key Laboratory of Coal Resources Exploration and Comprehensive Utilization,Ministry of Natural Resources;

    As an important coal-derived carbon material, coal-based carbon materials have the advantages of high specific surface area, good conductivity, abundant resources and low price, and have broad application prospects in the field of energy storage.The preparation methods of coal-based carbon materials mainly include activation method, template method and heteroatom doping method. The activation method is a commonly used method for preparing coal-based carbon materials. By activating coal with gas or chemical reagents at high temperatures, coal-based carbon materials with high specific surface area and rich pore structure can be obtained. The template method can prepare carbon materials with special pore structure by selecting appropriate template materials, with uniform pore diameter and orderly structure. The heteroatom doping method is a method that introduces heteroatoms into coal-based carbon materials to regulate their electronic structure and electrochemical properties. This method can not only form functional groups on the surface of carbon materials and improve the reaction efficiency of the materials, but also generates pseudocapacitance through redox reactions to improve the electrochemical properties of the material. There are many types of coal-based electrode materials prepared with coal as precursor, including coal-based amorphous carbon, coal-based porous carbon, coal-based graphite, coal-based carbon nanofibers, coal-based graphene and coal-based graphene quantum dots. Compared with traditional carbon electrode material precursors(natural graphite, petroleum coke, pitch coke, etc.), the aromatic lamellar structure and alkyl branches of coal-based carbon materials have special properties. The aromatic lamellae are graphitized at high temperature to form laterally extended graphite crystal layers, and alkyl branches form carbon intermediates or small molecule clusters with active groups, further constructing new carbon materials, giving coal-based carbon materials the advantage of manufacturing electrode materials. In the field of electrochemical energy storage, coal-based electrode materials have been widely used. Researchers have successfully applied coal-based carbon materials into energy storage devices such as supercapacitors, lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries, and achieved good performance. In summary, coal-based carbon materials, as a new energy material with great potential, have broad application prospects and important research significance. However, there are still many difficulties and challenges in the current research on coal-based electrode materials in the field of energy storage. For example, in the processing of raw coal, the use of strong oxidants, the need for high-temperature, high-pressure environments and special protective atmospheres will cause environmental pollution waste and by-products. Therefore, looking forward to future research directions, it is not only necessary to optimize the preparation process of coal-based carbon materials, improve the electrochemical properties of the materials, and expand the application of coal-based carbon materials in the field of energy storage, but also to use green, safe and economical methods to prepare high-quality materials on a large scale, in order to provide support for the clean, efficient and low-carbon utilization of coal, and provide a reference for the development of advanced coal-derived carbon materials.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1734K]

  • Research status and advances of mobile solid oxide fuel cell system integration technology

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

    Solid oxide fuel cells(SOFCs) are energy conversion devices that can convert the chemical energy in fuels into electricity through electrochemical reactions. At present, SOFC is mostly regarded as a stationary power generation technology. However, due to its fuel flexibility, high efficiency, and high energy density, it also has broad application prospects in the field of mobile power generation, such as auxiliary power, drone power, remote power supply, etc. Compared to the stationary applications of SOFCs, the progress toward the mobile applications of SOFCs starts relatively late and the technology is relatively incomplete. Mobile SOFC systems typically consist of SOFC stacks, fuel supply systems, oxygen supply systems, thermal management systems, and power management systems. When developing SOFC mobile systems, system robustness, ease of use, and power generation capacity should be considered. However, the components of mobile SOFC systems are relatively complex, and the coupling and matching characteristics of these components will significantly affect the system compactness, startup characteristics, and volume/mass power density of the system. This paper provided a review of the domestic and international research progress on the integration technologies of mobile SOFC systems, covering aspects such as thermal characteristics, startup strategies, and the integration of high-power density hybrid systems. Finally, based on a summary of existing research findings, the challenges in the future integration of mobile SOFC systems were identified, along with such directions for development as improvements in materials and processes, the exploration of novel startup strategies, and the design and optimization of hybrid systems.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1577K]

  • Kinetics of Co-Ca catalyzed coal char hydrogasification in a pressurized fluidized bed

    LIU Jiamin;GU Sumin;ZHANG Rong;LI Weiwei;QU Xuan;School of Chemistry and Chemical Engineering,North University of China;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences;

    The coal catalytic hydrogasification is a highly promising technology for converting coal to natural gas. It consists of coal catalytic hydropyrolysis and char catalytic hydrogasification. The char catalytic hydrogasification is the rate-controlling step of the whole process because its rate is much less than that of coal catalytic hydropyrolysis. Therefore, it is critical to establish a reasonable kinetic model of Co-Ca catalyzed char hydrogasification in pressurized fluidized bed for the technology′s future development. The variations of particle density and pore characteristics with carbon conversion were investigated during Co-Ca catalyzed char hydrogasification in a lab-scale pressurized fluidized bed. The results show that the char particle density decrease as the carbon conversion, and there is linear correlation between the total pores specific surface area and reaction rate. These phenomena confirm that the conversion of char should follow the random pore model during Co-Ca catalyzed char hydrogasification. The effects of reaction temperature, hydrogen pressure, and Co loading on the carbon conversion were researched. It is found that the reaction is controlled by dynamics in the range of 650-850 ℃. The reaction rate is dramatically increased when the temperature is over 750 ℃, and the carbon conversion increase from 16.32% to 95.32% when reaction temperature is elevated from 650 ℃ to 850 ℃. The carbon conversion is elevated to 94.11% with increasing the hydrogen partial pressure from 0.6 MPa to 2.5 MPa. Raising the Co loading from 1% to 3% resultes in the continous increase in carbon conversion, but it has little change when the Co loading is furtherly increased to 5%. The experiment data was analyzed adopting an extended random pore model with the introduction of empirical parameters c and p. The results indicate that the activation energy of coal char catalytic hydrogasification is 122.7 kJ/mol, and the reaction order is 1.54. The average deviation between the predicted and experimental reaction rate is 4.81%.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1588K]

  • Measuring temperature of methanol-to-olefins catalyst bed by use of electrical capacitance tomography

    CHEN Xiyue;MENG Shuanghe;ZHANG Tao;YE Mao;Dalian Institute of Chemical Physics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;

    As a key step in the production of olefins from coal, the methanol-to-olefins(MTO) process is of significant importance in coal chemical industry. Since MTO is an exothermic reaction, it is necessary to monitor the temperature distribution in the bed to improve the conversion of methanol and selectivity of products. In this study, a method was proposed for online monitoring of the catalyst bed temperature(DMTO industrial catalyst, ZSM-5 zeolites) using high-temperature electrical capacitance tomography(ECT) imaging. By comparing the measurement results with different bed materials such as quartz sand and alumina, which have a minimal change in relative permittivity with temperature, It is found that the relative permittivities of catalyst and zeolites vary with temperature, and thus the measured capacitance between electrodes are sensitive to temperature in the catalyst bed. Therefore, the temperature of the bed can be measured by averaging the normalized capacitance of the bed with uniform temperature distribution through the high—temperature ECT. This method was veritied by an online temperature measurement for DMTO catalyst and ZSM-5 zeolites in a thin-walled quartz fixed bed reactor, and further showed that the ECT images reconstructed using the linear back projection algorithm might be used to obtain the temperature distribution in the bed. Therefore, the fixed bed bed tempe rature can be measured by high-temperatur ECT.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1730K]

  • Numerical simulation of carbon deposition in direct methane solid oxide fuel cells

    XIAO Yao;LIU Zhijun;WEI Wei;XU Xiaofei;LIU Fengxia;Research & Design Institute of Fluid and Powder Engineering,School of Chemical Engineering,Dalian University of Technology;

    The direct utilization of hydrocarbon fuel leads to the significant issue of carbon deposition and performance deterioration in solid oxide fuel cells(SOFC). It is imperative to expedite the commercialization of solid oxide fuel cells by analyzing the causes of carbon deposition and implementing measures to mitigate it. This paper presented a three-dimensional transient multi-physics coupled model for carbon deposition. The impact of various conditions and parametered on the performance of solid oxide fuel cells was investigated through simulation model calculations, aiming to assess the long-term performance of the cells. The calculated results demonstrate good agreement with experimental findings in terms of operating voltage and carbon deposition rate. The findings indicate that an increase in carbon deposition results in decreased porosity of anode electrode material and catalyst activity. Moreover, an upward trend in carbon deposition is observed with reduced prereforming degree, increased inlet speed, elevated operating temperature, decreased operating voltage, and higher hydrogen content in the fuel. Notably, while an increase in operating temperature, decrease in operating voltage, and higher proportion of hydrogen lead to increased carbon deposition and severe decline in electrical performance, overall battery performance improves. These results suggest a close relationship between this phenomenon and methane cracking reaction.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 2237K]

  • Breakthrough behavior and numerical inversion of UCG organic pollutant phenol through PRB

    WANG Fan;XU Bing;CHEN Lunjian;LI Congqiang;XING Baolin;SU Faqiang;Henan Key Laboratory of Coal Green Conversion,School of Chemistry and Chemical Engineering, Henan Polytechnic University;Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization;School of Energy Science and Engineering,Henan Polytechnic University;

    Underground coal gasification(UCG) is a coal utilization technique that combines coal extraction and conversion. However, the potential for groundwater pollution has emerged as a significant obstacle to its widespread acceptance and implementation. With the background of the UCG with shaft, phenol solution was used as the simulated UCG-contaminated water. Sand, a mixture of sand and organic bentonite, a mixture of sand and activated carbon were used respectively to construct the permeation reactive barrier(PRB). The finite element method and the Python scientific computing libraries, NumPy and SciPy were adopted to develop numerical inversion programs to study the breakthrough process of phenol in different PRB. The results show that:(1) When the PRB was filled with sand and organic bentonite, the diffusion coefficient D and seepage velocity q increased, while the dispersion λ and retardation R decreased as the mass ratio of sand and organic bentonite increased. Conversely, when the PRB was filled with sand and activated carbon, the diffusion coefficient D, seepage velocity q, and retardation R decreased, while the dispersion λ increased with an increase in the mass ratio of sand and activated carbon.(2) The mass ratio of the mixed materials controls their porosity and adsorption capability, which significantly impacts the blockage and purification of phenol. When the PRB is constructed from sand and organic bentonite, increasing the mass ratio leads to an increase in porosity and a shorter initial detection time for phenol. On the other hand, when the PRB is constructed from sand and activated carbon, increasing the mass ratio results in a decrease in porosity, and the initial detection time for phenol increases at first and then decreases.(3) The adsorption and purification effect of a PRB on phenol and its mechanism can be explained as follows: in the case of a PRB material made up of sand and organic bentonite, there exists a threshold mass ratio(2∶1 in this experiment). When the mass ratio is below this threshold, the PRB effectively purifies phenol. However, when the mass ratio exceeds the threshold, the purification effect significantly decreases. On the other hand, in the case of a PRB material made up of sand and activated carbon, the dominant factor influencing the purification process is the seepage speed of the solution when the mass ratio of sand and activated carbon is below 2∶1. Conversely, when the mass ratio exceeds 2∶1, the adsorption performance of activated carbon becomes the dominant factor.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1207K]

  • Adsorption behavior of water vapor in lignite pores: Experimental study and molecular dynamics simulation

    WANG Chengyong;XING Yaowen;WANG Shiwei;CHEN Peng;LI Jihui;GUI Xiahui;School of Mining and Mechanical Engineering,Liupanshui Normal University;Chinese National Engineering Research Center of Coal Preparation and Purification,China University of Mining and Technology;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;

    Deeply understanding the adsorption of water on lignite is one of the theoretical foundations of lignite drying and upgrading technology. The oxygen-containing functional groups and pore structure of lignite were analyzed using Fourier Transform Infrared Spectroscopy(FTIR), Scanning Electron Microscopy(SEM), and low-temperature nitrogen adsorption/desorption experiments. The adsorption behavior of water vapor in the pores of lignite was investigated using water vapor adsorption/desorption experiments and Molecular Dynamics(MD) simulations. Results show that the rich oxygen-containing functional groups and numerous micropores and mesopores(with the pore size mainly around 2 nm) in lignite samples provide adsorption sites and places for water vapor. The adsorption process of water vapor on the coal sample can be divided into three stages. In the first stage, with the relative vapor pressure(P/P_0)<0.21, water molecules directly adsorbe on oxygen-containing functional groups, and the adsorption speed is the highest. In the second stage(P/P_0=0.21-<0.71), water molecules interact with adsorbed water molecules, promoting the gradual growth of water clusters. In the third stage(P/P_0≥0.71), water clusters fill the pores and the capillary condensation appeared, the adsorption speed in this stage is slightly higher than in the second stage. According to the fitting results of the Dent model on the water vapor adsorption isotherm, the adsorption type belonged to multi-stage adsorption, including primary adsorption(first stage) and secondary adsorption(second and third stages). The primary adsorption energy(-48.77 kJ/mol) is significantly greater than the liquefaction heat of water(E_L=-43.99 kJ/mol), while the secondary adsorption energy(-42.28 kJ/mol) is only slightly less than E_L, indicating that the water adsorbed on lignite is liquid. There is a significant desorption hysteresis phenomenon during the water vapor desorption process, indicating that the water vapor adsorbes stably and is difficult to remove. High pressure hysteresis occurr in the range of P/P_0≈0.4-0.9, mainly caused by capillary condensation and the "ink bottle" effect. Low pressure hysteresis occurr in the range of P/P_0<0.4, caused by strong interactions between water molecules and oxygen-containing functional groups. The MD simulation results are consistent with the analysis of water vapor adsorption/desorption isotherm. Water molecules preferentially adsorb in the pore and form hydrogen bonds with oxygen-containing functional groups on the pore walls, with a diffusion coefficient(2.98×10~(-5) cm~2/s) similar to that of liquid water.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1632K]

  • Mechanistic study of the effect of air bubbles on the press pressure and dewatering performance of flotation concentrate coal

    YANG Zhanghua;DONG Xianshu;CHEN Ruxia;FAN Yuping;MA Xiaomin;FENG Zeyu;College of Mining Engineering,Taiyuan University of Technology;College of Engineering for Safety and Emergency Management,Taiyuan University of Technology;

    The addition of frothing agent makes the coal slurry flotation process produce stable, large viscosity value and difficult to break bubbles, and the accumulation of large amount of bubbles seriously restricts the pressurization and dewatering effect of flotation concentrate coal. In order to investigate the influence mechanism of bubbles on the filtering pressure and dewatering performance of flotation concentrate, the influence law of bubbles on the filtering pressure, cake displacement, filtrate quality and cake moisture of flotation concentrate using a new pressurized dewatering device was investigated, the dewatering mechanism by a series of methods such as ImageJ image processing, rheological characteristics test, FBRM test and SEM characterization was explored. The results show that the pressure required to press filter the flotation concentrate increase from 451.2 kg to 540.7 kg at an aeration rate of 0.3 m~3/h, and the filter cake moisture increas by 10.7 percentage points. ImageJ image processing shows that the distribution proportion of small diameter bubbles increases with the increase of air volume, rheological test shows that with the increase of air volume, and the viscosity of flotation cleaned coal increases and the dynamic shear τ_0 increases from 0.994 7 mPa to 1.170 3 mPa, indicating that the directional rearrangement of particles is enhanced.The FBRM test show that the presence of air bubbles increase the particle size of flotation concentrate, coalescence occurred, and the interaction force between particles increase. SEM results show that air bubbles make the flotation concentrate particles agglomerate. The presence of air bubbles make the flotation concentrate particles more closely arranged, the inter-particle capillary radius decrease, the pressure required for filtration increase, and the pore space of the filter cake become smaller, the water migration path is more complicated, which is not conducive to the removal of water.

    2024 05 v.30;No.165 [Abstract][OnlineView][HTML全文][Download 1610K]



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