2023年04期目次

  • Experiment of chemical looping water decomposition coupled with acetic acid pyrolysis using Fe-based oxygen carriers

    GAO Daoxing;DOU Binlin;ZHANG Hua;LUO Chuanqi;DU Jinbo;Energy and Power Engineering Institute,University of Shanghai for Science and Technology;

    It is of great significance to develop a new method for hydrogen production and syngas production that utilizes oxygen carrier catalysts to directly decompose water to produce pure hydrogen in one stepand couple it with biomass thermal conversion. Iron-based oxygen carriers doped with Ce-Ni were prepared by metal chelating sol-gel method. Pure hydrogen and hydrogen-rich synthesis gas were prepared by chemical looping water decomposition coupled with acetic acid thermal decomposition. Firstly, under the action of oxidized oxygen carriers, acetic acid catalyzed thermal decomposition to produce hydrogen-rich syngas. And the oxygen carrier was reduced to realize the migration of lattice oxygen in the oxygen carrier, and the thermal decomposition process was strengthened by in-situ CO_2 adsorption. Secondly, hydrogen production was achieved through the iron steam process using the reduced oxygen carrier with water. It is found that the in-situ CO_2 adsorption is enhanced during the catalytic thermal decomposition of acetic acid, which can improve the purity of H_2 in syngas and reduce carbon deposition. Compared with undoped pure iron oxide and blank quartz samples, the Fe-based oxygen carrier doped with appropriate amount of Ce and Ni has obvious hydrogen production effect. With the increase of Ce and Ni, the amount of CO_2 and CO produced in the acetic acid decomposition stage decrease, while H_2 increases firstly and then decreases during water decomposition. The optimum molar ratio of oxygen carrier Fe, Ce and Ni is 100∶10∶3.The addition of CO_2 adsorbent with different mass ratio of oxygen carrier can effectively reduce the amount of CO_2 and CO in syngas, and the best mass ratio is 1∶2.Under this condition, the syngas composition of H_2 is increased by 11.96%-26.17%, CO_2 is reduced by 22.85%-49.28%, CO is reduced by 29.18%-34.05%, and the oxygen carriers remain good stability after 15 cycles.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 55180K]

  • Policy incentives for the large-scale development of coal power+CCUS industry

    XU Dong;ZHANG Shuai;HAN Tao;ZHENG Xufan;CHANG Lin;FENG Baiyang;FENG Lei;New Energy Technology Research Institute,CHN Energy;

    Carbon capture, utilization and storage(CCUS) is an important strategic choice to achieve the goal of carbon neutrality. China′s energy and power structure is dominated by coal. The coal power+CCUS technology is an important guarantee to achieve deep decarburization of the power system and flexible and stable power supply. At present, the development of China′s CCUS industry has many problems, such as high barriers, high costs, imperfect policies and regulations, lack of incentive policies, and difficulties in financial financing channels, which limit the large-scale development of coal power CCUS technology. Focusing on the opportunities and challenges faced by the low carbon transformation of the coal power industry, the policies, regulations and successful cases in the field of CCUS in the United States, the European Union, the United Kingdom and other countries and regions were comprehensively analyzed, the successful experience in the construction of the CCUS policy system in developed countries and its enlightenment to China was summarized, the current situation and needs of China′s CCUS policy system were analyzed, the impact of different incentive policies on the transformation of coal-fired power CCUS was studied, and policy recommendations were proposed for the development of coal-fired power CCUS from the perspectives of CCUS positioning, policy incentives, standard specifications, publicity and guidance, etc. It can provide reference for promoting the development of CCUS industry and achieving the goal of carbon neutrality of coal power.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 2602K]

  • Development progress of liquid-liquid biphasic solvents for carbon dioxide chemical absorption capture from flue gas of coal-fired power plants

    LIN Haizhou;WU Dawei;FAN Yongchun;LUO Bixiong;PEI Aiguo;FANG Mengxiang;China Energy Engineering Group Guangdong Electric Power Design Institute Co.,Ltd.;China Power Engineering Consulting Group Co.,Ltd.;China Energy Engineering Co.,Ltd.;State Key Laboratory of Clean Energy Utilization,Zhejiang University;

    Post-combustion chemical absorption is one of the most mature technologies for CO_2 capture from coal-fired power plants. However, the high energy consumption for regeneration of traditional amine-based solvents is not conducive to the commercial application of chemical absorption technology. Liquid-liquid biphasic solvents, which can greatly reduce the regeneration energy consumption, have the prospect of replacing traditional solvents. The technical characteristics and solvents development of liquid-liquid biphasic solvents were reviewed in this paper. The liquid-liquid biphasic solvents can be divided into three types according to the composition, namely blending amine type(active amine + tertiary amine phase separation agent + water), organic solvent type(active amine + organic solvent phase separation agent + water) and water-free type(active amine + tertiary amine/organic solvent phase separation agent). The analysis focused on the phase separation behavior, energy consumption, viscosity and CO_2 absorption load of three different type biphasic solvents. Among them, organic solvent type biphasic solvents have more advantages in regeneration energy consumption(1.5-3.2 GJ/t), viscosity(can be controlled below 20 mPa·s), and cost(organic solvent phase separation agent + water shows better potential in cost). As a new type of solvent, liquid-liquid biphasic solvents still face many challenges in industrial application compared to traditional solvents, such as high viscosity of rich phase, high cost of solvents and difficult in phase separation control, etc. In order to accelerate the industrial application of biphasic solvents, it is necessary to carry out more in-depth research on optimizing the formula system with low energy consumption, reducing the rich phase viscosity and the loss of solvents, improving the phase separation control ability and carry out long cycle operation tests to improve process stability and reliability.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 11034K]

  • Research progress on hydrogen production technology from coke oven gas

    LI Zhiqiang;WANG Hua;LI Kongzhai;Faculty of Metallurgical and Energy Engineering,Kunming University of Science and Technology;

    Coke is used as reductant for blast furnace ironmaking, which is in great demand. The production process accompanies by a large number of coke oven gas(COG) generation, which has complex compositions, rich in hydrogen and high calorific value. However, about 20% gas is directly discharged or burned away in the way of "lighting the sky lamp", which conflicts with the current situation of hydrogen production capacity shortage and high price, and goes against the "double carbon" target. Realizing the clean and efficient utilization of coke oven gas is one of the key factors to promote the high-quality development of coking and metallurgical industries. At present, physical methods are the main technologies for producing hydrogen from coke oven gas, such as pressure swing adsorption(PSA), cryogenic process, membrane separation, etc. and the non-catalytic and catalytic reforming, oxygen transfer membrane(OTM) reforming, chemical looping reforming and other chemical producing hydrogen technologies are also focused, aiming at providing clean raw material gas for the downstream petrochemical, metal smelting and processing industries and others. The principle, characteristics, research and application progress of different hydrogen production technologies from coke oven gas were reviewed, and suggestions were given for the problems of the low exploitation level of coke oven gas and the low utilization rate of CH_4, CO_2, CO, tar and benzene. For physical purification and separation technology, the design and development of highly selective adsorbents, separation membranes and equipment intensification are the research keys. For chemical reforming technology, the construction of sulfur-resistant catalyst, oxygen transfer membrane, oxygen carrier and industrial exploration are the research focus. The combined hydrogen production process of chemical method and physical method includes purification, reforming, separation and other processes, which is an important path to realize clean, efficient and high-value utilization of coke oven gas, and an important direction of future development.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 17074K]

  • Research progress on catalytic hydrogenation of carbon dioxide to methanol

    GUO Jiayi;HE Yurong;MA Jingjing;HU Chenye;HE Shengzhong;ZHOU Zimiao;YANG Hui;HU Xiude;GUO Qingjie;State Key Laboratory of Coal Efficient Utilization and Green Chemical Engineering,Ningxia University;National Experimental Teaching Demonstration Center of Chemistry,College of Chemistry and Chemical Engineering,Ningxia University;

    In recent years, the frequent use of fossil fuels in many industrial sectors has led to massive greenhouse gas(GHG) emissions and a dramatic increase in CO_2 levels in atmosphere. The depletion of fossil fuels, global warming, climate change and sharp fluctuations in fuel prices have forced scientists to actively develop the new environmentally friendly fuels. The process of converting CO_2 into value-added products is considered to be a possible way to deal with the climate change and high energy consumption. Methanol is an important chemical raw material and energy, the demand in the industry is keeping increasing. In recent years, to comply with the carbon peaking and carbon neutrality goals, the thermal catalytic hydrogenation of CO_2 for methanol has been widely studied. There are many sources of CO_2 for the industrial production of methanol using, which can be separated from the flue gases emitted from oil refineries, coal refineries, manganese plants, etc. Hydrogen can be obtained from the electrolytic water route for green energy generation, such as solar, hydro or wind power generation. The research on catalytic hydrogenation of CO_2 to methanol using renewable energy sources cannot only reduce CO_2 emissions to a great extent, but also the carbon resources can be recycled and reused, which can effectively alleviate the current energy and chemical raw material shortage in China.In this paper, the characteristics of methanol and the global development of methanol technology in recent years were introduced. The catalysts, preparation process of methanol and the key problems that need to be solved were reviewed. Although there has been some progress in the research of CO_2 catalysts for methanol production, it is still difficult to realize the industrialization of CO_2 catalysts. The overall industrial cost of CO_2 catalytic hydrogenation to methanol is high, among which the cost of hydrogen production is the key factor affecting the process economy. Converting renewable energy such as solar, wind and water into electricity, and then using electrolysis of water to produce the green hydrogen, is currently the ideal research direction. Not only will it not emit carbon dioxide, but it will also consume carbon dioxide, which is in line with the carbon peaking and carbon neutrality goals.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 35652K]

  • Application progress of chemical percolation devolatilization model in thermochemical conversion of carbon-based solid raw materials

    GUO Wei;YANG Panxi;YU Zunyi;GAO Kun;WANG Jing;ZHANG Jie;DANG Minhui;YANG Bolun;WU Zhiqiang;Shanxi Key Laboratory of Energy Chemical Process Intensifcation,School of Chemical Engineering and Technology,Xi′an Jiaotong University;Shaanxi Coal and Chemical Industry Group Co.,Ltd.;

    The Chemicalpercolation devolatilization(CPD) model is used to simulate the devolatilization of coal under the condition of rapid heating, which can predict the real-time yield of tar, semi-coke and light gas. The model is based on a lattice model to construct the chemical structure of coal, and the structural parameters of coal are calculated by solid ~(13)C-NMR experiment. It has the characteristics of the wide applicability of coal types and a few input parameters, and has attracted the wide attention of researchers in the field of engineering thermochemistry. Firstly, the development history of the CPD model, the assumption of raw material structure and pyrolysis reaction path, and the calculation of structural and kinetic parameters were introduced. The application progress of the CPD model in the thermochemical conversion of carbon-based solid materials such as coal, oil shale, and biomass was summarized. To improve the accuracy and applicability of the CPD model in the field of coal thermochemical conversion, Chinese scholars have established a more accurate calculation method of lattice parameters according to the structural analysis of of Chinese coal species. By improving the pyrolysis reaction path and correcting the kinetic parameters in the CPD model, the model is closer to the real pyrolysis process. By correcting the temperature gradient distribution in coal particles makes the simulation results closer to the actual working condition. In terms of thermal conversion of oil shale, a CPD model of thermal conversion of oil shale was established based on the chemical structure characteristics and pyrolysis kinetic parameters of oil shale. The CPD model of biomass was established based on the analysis of biomass structure and reaction characteristics, and the applicability of the model was expanded by improving the chemical structure, pyrolysis reaction path, and kinetic parameters. Although the CPD model has been widely used, the fitting parameters obtained from coal elemental analysis and industrial analysis are narrow in the range of coal types, and the accuracy needs to be improved. Therefore, a more accurate structural model of carbon-based solid raw materials can be built through means of chemical structure characterization. The CPD model greatly simplifies the reaction process of coal and needs to be modified according to the actual pyrolysis reaction path of coal, including considering the secondary reaction, the coupling between tars, and the change of free radicals in the reaction. The existing CPD model does not consider the stress of coal in the underground thermal conversion process, so it needs to be improved from the high-pressure reaction conditions to improve the applicability of the model.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 15328K]

  • Analysis of the development of direct capture of carbon dioxide in the air from patent perspective

    XING Wei;XU Rulong;GAO Hetong;DUAN Lunbo;Patent Examination Cooperation Guangdong Center of the Patent Office,CNIPA;School of Energy and Environment,Southeast University;

    The proposal of carbon peak and carbon neutrality goals has provided a clear direction for reducing carbon emissions in China and set new standards for the advancement of carbon capture technology. Direct air capture(DAC) of carbon dioxide, a novel negative emissions technology, is crucial for achieving the carbon peak and carbon neutrality goals and has garnered significant attention. As an effective carrier of technological information, patent is an important tool for analyzing technological development. It have the characteristics of rich and complete information, long coverage time, authenticity and reliability, and is an important supplement to academic journal resources. The relevant keywords of direct air capture were searched, and based on domestic and foreign patent documents, the development process of direct capture CO_2 technology in the air was analyzed, the number of patent applications for direct air capture technology, the main technical forms and improvement measures were analyzed. The key patented technologies of the main research innovation subjects are highlighted, including the improvement of low-cost and high-efficiency adsorbents, the method of reducing the resistance of air circulation devices, and the coupling of direct air capture systems with other chemical systems. With the cost reduction and efficiency increase brought about by the development of technology, and the establishment of carbon trading market and carbon tariff, the air direct capture CO_2 technology with negative carbon potential will receive more extensive attention. Finally, the future development direction of air direct capture CO_2 technology in China was prospected.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 38005K]

  • Carbon dioxide capture, utilization and storage technology and engineering application for coal-fired power plants

    GU Yongzheng;WANG Tiankun;HUANG Yan;ZHAO Rui;XU Dong;GD Power Development Co.,Ltd.;CHN Energy Jinjie Energy Co.,Ltd.;CHN Energy New Energy Technology Research Institute Co.,Ltd.;

    China is the largest carbon dioxide(CO_2) emission country in the world. As the most important source of carbon emissions, coal-fired power generation is in urgent need of transition to green and low-carbon development. The development trend of carbon emission reduction and the research status of CO_2 capture, utilization, and storage(CCUS) at home and abroad were systematically sorted out. The engineering innovations and practices in coal-fired power plant CCUS were focused on. Furthermore, the 150 kt/a post-combustion CO_2 capture, utilization for enhanced oil recovery, and storage demonstration project based on 600 MW capacity grade coal-fired power unit was built and put into operation on June 25, 2021, which is the largest project of its kind in China to date. The results show that the CCUS demonstration project is consist of 6 units, including washing, capture, compression, drying, liquefying, storage and loading. The new organic composite amine-based absorption technology is innovated and developed, and many new devices such as modified polypropylene plastic packing, tube-type falling film stripper reboiler, and so forth are developed and applied. In addition, the high-efficiency and energy-saving technique coupling with absorber inter-cooling, rich-split staged desorption, and mechanical vapor recompression(MVR) flash evaporation is innovatively formed. During the 168 h trial operation period, each unit of the CCUS demonstration project can operate stably under different loads which are between 50% and 100%. The industrial grade products of liquid CO_2 with purity up to 99.5%, temperature ranging from-16 ℃ to-21 ℃, and pressure of about 2.0 MPa, are produced continuously. And the CO_2 yield more than 18.75 t per hour under the full load condition, achieving a major breakthrough of low concentration(volume fraction 11%-15%), high flow rate(about 100 000 m~3/h) coal-fired flue gas CO_2 capture rate >90%, regeneration energy consumption <2.4 GJ/t(in terms of CO_2), and overall performance index reaching international leading level, providing a guarantee for China′s coal power to cope with the 2060 carbon peak carbon neutral target. Therefore, it provides scientific and technological support for ensuring China′s coal-fired power to better achieve the 2060 goal of carbon peaking and carbon neutrality for the power system.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 18870K]

  • Optimisation analysis of carbon capture and storage coupled with cooling in coal-fired power plants

    CHEN Yang;WU Ye;LIU Xing;LIU Dong;School of Energy and Power Engineering,Nanjing University of Science and Technology;Jiangsu Whale Energy Zero Carbon Technology Co.,Ltd.;

    The use of carbon capture and storage(CCS) system to reduce CO_2 in coal-fired power plants is one of the necessary paths to carbon neutrality, but the current high cost of CCS has limited the development and application of this technology. For a 300 MW coal-fired unit, an alkali metal-based dry carbon capture and storage coupled cooling system was proposed and built using Aspen Plus simulation software, which used condensate circulation for deep coupling to achieve the purpose of recovering the cold volume in the CO_2 compression and storage process and effectively reduce the carbon capture cost. Without coupling the cooling process, the unit power consumption of the carbon capture system is reduced to 413.79 kWh/t(in terms of CO_2, the same below) by recovering the reaction heat released from the CO_2 adsorption process. The energy consumption of the CO_2 compression and storage process is still significant at this point. For this reason, the carbon capture and storage system described above was further coupled to a refrigeration unit. The simulation calculation shows that the new integrated system reduces the degree of CO_2 compression and the unit power consumption of the compression storage process is reduced to 247.54 kWh/t, a reduction of 2.3%, resulting in a further 33.77% reduction in the total operating cost of CO_2 capture and storage. In addition, the introduction of cooling units can reduce additional investment cost reductions, such as reducing the amount of heated surface arrangement and adsorbent loading by increasing the heat transfer temperature difference within the CO_2 adsorption bed, and thus reducing the adsorption bed size with obvious optimization effects. Therefore, the above work provides an important support for the promotion and application of CO_2 capture and storage technology, and also broadens the way of CO_2 utilization.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 25972K]

  • Coupling optimization of carbon capture system with MVR heat pump energy- saving process

    HAN Bing;WANG Ziyang;TIAN Xiangfeng;ZHANG Kefang;GONG Liang;LIU Haoxuan;Longyuan (Beijing) Carbon Asset Management Technology Co.,Ltd.,China Energy Investment;New Energy Institute,China University of Petroleum (East China);

    Chemical absorption method is an important way to capture carbon dioxide in coal-fired power plants, but the high energy consumption in the process restricts its development.The carbon capture process integrated MVR pump is an important means to reduce energy consumption. The main drawbacks of current researches, which mainly use software for simulation optimization, are inflexible selection of constraint conditions, the local optimization of parameters for the MVR part and complicated simulation process. In order to address the lack of researches, based on the data of the carbon capture system that captures 2 million tons of carbon dioxide annually, the overall modeling optimization of the desorption unit integrated with MVR pump was carried out with flexible constraint selection and simple and intuitive optimization process. Firstly, the thermodynamic model of CO_2 absorption by MEA and the mathematical model of MVR heat pump equipment were established, and the design parameters of the MVR heat pump process flow were obtained. On this basis, taking the minimum desorption energy consumption as the objective function, the small terminal difference and the final pressure of secondary steam compression of the lean and rich liquid heat exchanger were optimized. Then, based on the optimization results, the flash pressure of MVR system was optimized when the final pressure of secondary steam compression was 140 kPa and the small end difference of lean and rich liquid heat exchanger was 5 ℃. The optimization results show that the optimal flash pressure is 109.2 kPa, and the minimum equivalent desorption energy consumption of the capture system is 2.82 GJ/t(in terms of CO_2). Compared with the conventional carbon capture system, the energy saving is 5.61%,with obvious energy saving effect. The economic analysis results show that the investment of energy saving optimization scheme of integrating MVR pump is 7.082 8 million yuan, the annual net income is 5.235 5 million yuan, the net present value is 34.492 million yuan, and the dynamic payback period of the investment is 1.5 years.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 12982K]

  • Reaction characteristics of carbon dioxide fixation by direct wet carbonation of carbide slag

    KONG Xiao;ZHAO Chuanwen;SUN Jian;GUO Yafei;QI Haoyue;LU Ping;School of Energy and Mechanical Engineering,Nanjing Normal University;

    Direct liquid-phase carbonation of alkaline solid waste is an effective way to fix CO_2. In this paper, the reaction characteristics of direct liquid phase carbonation of carbide slag waste to fix CO_2 were studied. Based on a high-pressure reactor at room temperature, the effects of liquid-solid ratio(5-20), carbonation time(0-4 h) and reaction pressure(0.1-1.0 MPa) on carbonation rate and CO_2 fixation capacity of carbide slag were studied. The results show that carbide slag has good CO_2 fixation ability, and the whole carbonation reaction is basically completed within 1 h. The CO_2 fixation ability increases with the increase of liquid-solid ratio and reaction pressure. The CO_2 fixation amount of calcium carbide slag is 9.26 mmol/g under the optimal operating condition(1 MPa, liquid-solid ratio 20) for 4 h reaction time, while the CO_2 fixation amount of calcium carbide slag is only 3.58 mmol/g under the condition of 0.1 MPa and liquid-solid ratio 5. It is proved by SEM and TGA that a large amount of CaCO_3 is formed after carbonation of carbide slag, and the particle size of the carbonated product is significantly reduced. Therefore, the direct liquid phase carbonation of carbide slag has better CO_2 fixation ability and higher carbonation efficiency under the condition of normal temperature and pressure in the reactor. The results of this study can provide basic theoretical support for the application of calcium carbide slag accelerated mineralization to fix CO_2.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 18789K]

  • Experiment and molecular simulation of cellulose during chemical looping depolymerization with iron-based oxygen carriers

    GUO Wenqian;MENG Liangliang;GENG Chang;LI Na;WU Ge;ZHANG Hui;GUO Qingjie;BAI Hongcun;State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University;College of Chemistry and Chemical Engineering,Ningxia University;

    To explore the mechanism and process of chemical looping depolymerization for cellulose in the presence of iron-based oxygen carriers, the characteristics of chemical looping combustion for cellulose at different heating rates were investigated by thermogravimetric analysis tests. The activation energy of cellulose during chemical looping combustion was calculated using chemical reaction kinetics and its kinetic mechanism was revealed. The microscopic reaction network of cellulose during chemical looping combustion was elucidated from the microscopic atomic scale by using ReaxFF MD simulation synthesis technique.The thermal analysis results show that the addition of iron-based oxygen carriers can reduce the onset temperature of cellulose chemical looping depolymerization and that the lattice oxygen released by iron-based oxygen carriers can help promote the chemical looping depolymerization of cellulose. Chemical looping combustion process of cellulose are divided into three different stages: volatile analysis out combustion, semi-coke conversion combustion and coke combustion stages.The kinetic model shows that the activation energy of cellulose in the thermal conversion process at different conversion rates is about 220-405 kJ/mol, with the highest activation energy of the reaction occurring at stage 3. Finally, ReaxFF MD simulations show that the overall chemical looping combustion process of cellulose follows the free radical chain reaction theory. The reactive radicals generated by cellulose cleavage reacted with the lattice oxygen releasing the oxygen carrier form intermediates such as 2-hydroxyacetone, which then under go further radical reactions to produce CO_2. A complex reaction network for the release of CO_2 production during the chemical looping depolymerization of cellulose in the presence of oxygen carriers is finally obtained.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 26680K]

  • Study on formulation of aerated concrete by CO_2 mineralization using coal ash

    HU Daqing;LUO Kuang;ZHANG Wei;LI Hedong;WANG Tao;CHEN Biao;ZHANG Li;FANG Mengxiang;Zhejiang Tiandi Environmental Protection Technology Co.,Ltd.;State Key Laboratory of Clean Energy Utilization,Zhejiang University;School of Civil Engineering and Architecture,Zhejiang Sci-Tech University;

    In order to realize the utilization of coal-fired solid waste and captured carbon dioxide, the effects of ratio of solid waste, mineralized curing pressure and mineralized curing temperature on the compressive strength and carbon fixation rate of aerated concrete were studied, with the coal-based waste, coal ash and desulfurization gypsum as the main raw materials and slag as the supplementary cementitious material. The crystal phase structure and micro morphology under different mineralized curing conditions were analyzed by XRD and SEM, and the effect of different mineralized curing conditions on the pore structure of aerated concrete was studied by MIP. The experimental results show that the appropriate residual water/slag ratio is helpful to improve the CO_2 fixation rate and early compressive strength of aerated concrete. When the CO_2 curing pressure increases from 0.05 MPa to 1.00 MPa, the carbon fixation rate increases by 24.8%, and the compressive strength increases first and then decreases. When the curing pressure is 0.1 MPa, the maximum compressive strength is reached. With the CO_2 curing temperature rising from 25 ℃ to 105 ℃, the carbon fixation rate and compressive strength increases first and then decreases. The carbon fixation rate reaches maximum of 7.21% at 45 ℃, and the compressive strength reaches maximum of 3.53 MPa at 65 ℃. According to analysis of XRD and SEM, the major mineralized products are CaCO_3, which mainly exist in the form of calcite and vaterite. Higher curing pressure(≥0.2 MPa) is likely to cause micro-cracks at the product interface. With the increase of curing temperature, the mineralized products and hydrated products appear simultaneously. According to MIP analysis, the influence of mineralized curing on the pores of aerated concrete can be divided into two aspects: on the one hand, CaCO_3 and other products with small particle size can fill the pores of 10-50 nm, on the other hand, reaction heat of mineralization and volumetric expansion of products can cause the increase of 30-60 μm pores. The microstructure can be optimized by increasing the curing temperature, which can make the distribution of pores more uniform.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 52638K]

  • Effect of reduction temperature on the integrated CO_2 capture and methanation performance of NaNO_3 modified Ni-MgO dual function materials

    SONG Jing;GUO Benshuai;GUO Yafei;ZHAO Chuanwen;China Petroleum Engineering & Construction Co.,Ltd.;Sinopec Nanjing Research Institute of Chemical Industry Co.,Ltd.;School of Energy and Mechanical Engineering,Nanjing Normal University;

    The integration of CO_2 capture and utilization(ICCU) is an important strategy to realize CO_2 emissions reduction and clean energy storage. It has been also recognized as a key negative emission technology(NET) to accelerate the realization of carbon neutrality. Dual function materials(DFMs) with both high CO_2 uptakes and excellent catalytic activity are the key to realizing the ICCU scheme. The integrated CO_2 capture and in-situ methanation(ICCU-M) process based on Ni/MgO DFMs promoted by alkali metal salt(AMS) has attracted broad attention. The stability of AMS and the reduction of NiO active components are critically important for improving the CO_2 adsorption methanation performance of Ni/MgO bifunctional materials modified with molten salts. In this work, NaNO_3-promoted Ni/MgO DFMs were prepared and the influence of reduction temperature on ICCU-M performance was investigated. The results indicate that the doped AMS can promote the dissolution and diffusion of CO_2 and MgO at low temperatures(～300 ℃), and improve the CO_2 adsorption performance. Due to the high temperature(>340 ℃), the dissolution and diffusion of CO_2 and MgO are blocked, and the migration of molten salt components covers the active site, resulting in the accumulation and sintering of materials and the decomposition of molten salt, and the attenuation of their adsorption performance. Increasing reduction temperature favors NiO reduction, which can increase CH_4 yield, CO_2 conversion and CH_4 selectivity. After reduction at 450 ℃, the CO_2 adsorption capacity and conversion rate of the 10NaNO_3-Ni/MgO DFMs(NaNO_3 loading of 10%) are 6.46 mmol/g and 79.37%, and the CH_4 yield and selectivity are 0.85 mmol/g and 96.27%, respectively. Given the impact of reduction temperature on CO_2 capture capacity and methanation activity, a compensatory strategy of catalyst reduction under low temperature and high H_2 concentration was put forward, to boost the methanation activity of the DFMs while maintaining the stability of AMS and CO_2 adsorption performance.

    2023 04 v.29;No.152 [Abstract][OnlineView][HTML全文][Download 36068K]



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