2022年09期目次

  • Research on the prospect and development strategy of hydrogen energy in China

    XU Lianbing;National Energy Investment Group Co.,Ltd.;

    Under the trend of global energy development towards clean, low-carbon and intelligent development, the development of hydrogen energy has become an important direction of the current world energy technology transformation in the world, and it is of great significance for China to realize the energy transformation in the new era. Based on this, a systematic study was performed on the prospect and development strategy of hydrogen energy utilization in China. Firstly, combining the characteristics of China′s hydrogen energy industry chain, the development status of China′s hydrogen energy was described from the aspects of hydrogen production, hydrogen storage and hydrogen use. In terms of hydrogen production, China has an annual hydrogen production capacity of about 41 million tons and an output of about 33.42 million tons, making it the world′s largest hydrogen producer. In terms of hydrogen storage and transportation, due to the small application scale and low level of technical equipment, the construction of hydrogen energy transportation capacity in China lags behind that in foreign countries. In terms of the construction of hydrogenation stations, China has built and operated 127 hydrogenation stations, and the design, construction and three key equipments of hydrogenation stations have been localized. In terms of hydrogen industry, China has got a certain degree of commercial application in the field of transportation, power generation and other information fields, especially the hydrogen fuel cell industry has developed rapidly. Secondly, the paper deeply analyzed the main problems existing in China′s hydrogen energy utilization. At present, the development of China′s hydrogen energy industry cluster has achieved initial results, but compared with the international hydrogen energy development, China′s hydrogen energy development and utilization is facing severe challenges. Especially in terms of fuel cell technology development, hydrogen energy industry equipment manufacturing, etc., there is a lack of long-term national hydrogen energy development strategy and comprehensive planning. It urgently needs to be analyzed from the perspective of development strategy and planning comprehensive research and layout in basic research, application research, product development, specifications and standards, performance testing, technical demonstration, business innovation, etc. Finally, the prospect and application scenarios of hydrogen energy utilization in China were systematically analyzed, and strategic measures and suggestions to promote hydrogen energy utilization were put forward. In terms of strategic measures, firstly, it is necessary to conform to the national strategy, adhere to the planning guidance, and make a strategic plan for the development of hydrogen energy industry. Secondly, it should highlight the platform effect, coordinate innovation and development, and give full play to the role of various core hydrogen energy industrialization platforms. Thirdly, it is necessary to strengthen scientific and technological innovation, deepen industry university research cooperation, strengthen collaborative innovation, and give full play to the leading role of scientific and technological innovation in overall innovation. Fourth, it is necessary to improve the talent mechanism, create core advantages, and fully mobilize the enthusiasm and creativity of scientific and technological personnel. In terms of policy recommendations, it is necessary to further strengthen the important position of hydrogen energy in the national energy system, strengthen the independent research and development of core technologies and the construction of technical standard system, select the development route of hydrogen energy industry according to local conditions, and properly guide the optimal layout of state-owned capital in the hydrogen energy industry to ensure the healthy and sustainable development of China′s hydrogen energy industry.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 4341K]

  • Recent advances and trend of Li_4SiO_4-based CO_2 adsorbents

    HU Xixuan;PAN Deng;XUE Tianshan;HUANG Liang;WANG Qiang;School of Environmental Science and Engineering,Beijing Forestry University;Wuhan Kaidi Water Service Co.,Ltd.;Institute of Atmospheric Environment,Chinese Research Academy of Environmental Sciences;

    With the acceleration of human society industrialization, greenhouse gas emissions have been increasing, leading to the intensification of the greenhouse effect. Among all greenhouse gases, CO_2 accounts for the largest proportion and contributes the most, which is considered to be the main factor causing global warming. Anthropogenic CO_2 emissions mainly come from the combustion of fossil fuels during industrial production. In order to achieve the goal of carbon neutrality, CO_2 capture and storage of industrial waste gases is an essential technological measure in addition to measures such as promoting clean energy, improving energy use efficiency and increasing plant carbon sinks. Currently, the main factor limiting the application of CO_2 capture and separation processes is the high cost. To solve this problem, the development of the second generation of low energy consumption solid CO_2 adsorbent materials is of great significance to promote CO_2 emission reduction from industrial sources. Li_4SiO_4 shows good application prospects in the field of high temperature CO_2 cap-ture due to its high adsorption capacity, low regeneration energy consumption and cost. To promote the application of Li_4SiO_4 materials in carbon capture, utilization and sequestration(CCUS) technology, this paper reviewed the current research progress of Li_4SiO_4-based adsorbent materials, introduced the effects of different synthesis methods and synthesis conditions on Li_4SiO_4 materials, discussed the methods of performance modification of the materials and their influence mechanisms, and summarized the pelleting of Li_4SiO_4 materials and their application technologies in recent years. The adsorption process of CO_2 by Li_4SiO_4 in the double-shell model can be divided into chemical adsorption and pore diffusion, in which the diffusion process is the decisive step of CO_2 adsorption by Li_4SiO_4. Through the regulation of the synthesis process, adsorbent materials with smaller particle size and porous structure can be obtained, thereby promoting the diffusion process of CO_2. In addition, the active sites of the adsorbent can be improved by alkali metal salt loading, so as to improve its adsorption kinetics. For the material molding applications, the traditional extrusion granulation is likely to cause the destruction of Li_4SiO_4 particle channel structure and the reduction of specific surface area, which can be generally improved by template support and pore-forming agent. For the moulding materials, appropriate reactor and adsorption and desorption process matching are needed, and these aspects need to be further optimized. Finally, this paper summarized the current challenges in the development of Li_4SiO_4-adsorption materials and put forward the development trend of this field. Li_4SiO_4-based materials are undergoing a transition from basic research to engineering application. In addition to the demand for higher activity and stability of adsorption materials, their large-scale production and granulation, synthesis cost, energy consumption of adsorption and desorption, application scenarios and treatment and disposal of CO_2 after capture are also key directions to be urgently studied.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 32663K]

  • Strategies and prospect of photosynthesis mechanism intensification of microalgae CO_2 fixation

    MAO Weiwei;ZHANG Lei;YIN Qingrong;LI Pengcheng;HU Zhan;SONG Chunfeng;School of Environmental Science and Engineering,Tianjin University;Tianjin FAW Toyota Motor Co.,Ltd.;

    With the rapid development of industrial technology and the extensive use of fossil energy, the CO_2 emissions are increasing year by year, and the global warming it causes is one of the most concerned topics in the global environment and economy. CO_2 capture, utilization and storage(CCUS) is a key technology for China to achieve the goal of carbon peaking and carbon neutrality, which is of great significance for China to reduce CO_2 emissions and build ecological civilization. Microalgae have the advantages of fast growth rate, strong adaptability to extreme environments, and low production costs. Its mediated CCUS technology is able to absorb and fix CO_2 and convert it into high value-added products. In this process, the species of microalgae play a crucial role in determining CO_2 fixation efficiency and biomass production. At present, many review studies focus on the use of microalgae for carbon capture, utilization and storage, but there are few reviews on the latest strategies to improve the carbon capture efficiency of microalgae. Based on the development status of microalgae carbon fixation technology, the photosynthesis and carbon fixation mechanism in microalgae were systematically discussed. Then, this work reviewed recent advances in microalgal strains for CO_2 fixation, focusing on the improvement and modification of strains used in coal-fired flue gas. A further comprehensive summary of recent trends and strategies to improve photosynthetic efficiency in microalgae was presented. Several strategies to modify and improve microalgal strains, including random mutagenesis, adaptive laboratory evolution, and genetic engineering, can be used to generate the desirable microalgae strain. Among them, genetic engineering can not only truncate the antenna size of the light-harvesting complex(LHC) to improve photosynthetic efficiency, but also improve the velocity and selectivity of Rubisco. Strategies to intervene by adding nanomaterials(NMs) to microalgal cultures can enhance CO_2 diffusion/dissolution in solution, significantly increase the relative electron transport rate in photosynthetic system Ⅱ(PSII) as well as reactive oxygen species(ROS) levels in microalgae, thereby improving the general response to carotenoids photosynthesis. Finally, the current challenges and future development directions of this technology were clarified, and a high-efficiency microalgae carbon sequestration system that tolerates flue gas should continue to be developed. Finally, the current challenges and future development direction of this technology were clarified. Efficient microalgae carbon fixation systems should be researched and developd that can tolerate flue gas.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 4218K]

  • Research status and future development direction of CO_2 absorption technology for organic amine

    LU Shijian;GONG Yuping;LIU Ling;KANG Guojun;CHEN Xi;LIU Miaomiao;ZHANG Juanjuan;WANG Feng;Institute of Carbon Neutralization,China University of Mining and Technology;School of Chemical Engineering,China University of Mining and Technology;Sinopec Nanjing Research Institute of Chemical Industry Co.,Ltd.;

    Carbon dioxide emissions are increasing rapidly, which is a serious threat to human survival and climate change, and how to reduce carbon emissions is a hot concern. The chemical absorption method is one of the main methods for capturing CO_2. The essence of CO_2 removal is the use of an alkaline absorber solution to contact and chemically react with the CO_2 in the flue gas reversely, forming unstable salts, which will decompose in the reverse direction to release CO_2 under certain conditions, thus achieving the separation and removal of CO_2 from the flue gas. The development of chemical absorption method technology using alcohol amine solution as absorbent has been relatively mature, and the separation effect is good and simple to operate, which is widely used in electric power, iron and steel, cement and chemical industries. Alcohol amine solutions are the core of the chemical absorption method, and the alcohol amine solutions currently used in industrial abatement include primary alcohol amine solutions, secondary alcohol amine solutions, tertiary alcohol amine solutions and steric hindered amines. Four typical alcohol amine solutions were listed in this paper, and the current status of domestic and international research on amine solutions for low concentration flue gas absorption was reviewed. The KM-CDR process of Mitsubishi Heavy Industries, the desulphurization and decarbonization process of Shell Consolv, the supporting process of Dow Chemical Ucarsol solvent, the supporting process of Siemens amino acid salt solution and the ECO_2 process of Powerspan were introduced, while the oxygen-enriched combustion technology of Alstom was summarized. The research on carbon capture in China is relatively short, under the promote of "carbon peaking and carbon neutrality goals",carbon emission reduction has become the focus and hotspot of domestic research in recent years, the research results of a number of universities and research institutes, such as Zhejiang University, North China University of Electric Power, Beijing University of Chemical Technology and China University of Mining and Technology, were listed in the paper. At present, the chemical absorption method has been applied in industry, and a number of carbon capture demonstration projects have been built in China. The 10 000 tons/year CO_2 capture demonstration project of Huadian Jurong Power Plant, the 150 000 tons/year CO_2 capture demonstration project of Guohua Jinjie Power Plant and the 40 000 tons/year coal-fired CO_2 capture and oil drive demonstration project of Shengli Oilfield were systematically introduced. The scale of CO_2 capture demonstration projects for coal-fired power plants at home and abroad is generally small, with only three million tons demonstration projects, among which Sinopec has built China′s first million tons carbon capture project, which is a milestone for the development of China′s carbon capture industry. In the field of CO_2 capture by organic amines, research should be focused on five aspects: energy consumption and degradability reduction of absorber regeneration, comprehensive use and recovery of thermal energy in the capture system, development of high flux CO_2 capture and absorption reactors, and control of absorber escape, to develop low energy consumption, low loss and low cost CO_2 capture technologies, promote multi-industry engineering demonstrations, and lay the foundation for the large-scale promotion of CO_2 capture technologies for coal-fired flue gas.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 24723K]

  • Progress on the reduction and utilization of CO_2 in flue gas from coal-fired power plant by microalgae photosynthesis

    HUANG Yun;PENG Hongyan;FU Jingwei;ZHU Xianqing;XIA Ao;ZHU Xun;LIAO Qiang;Key Laboratory of Low-grade Energy Utilization Technologies and Systems,Ministry of Education,Chongqing University;Institute of Engineering Thermophysics,School of Energy and Power Engineering,Chongqing University;

    Microalgae photosynthesis for fixing CO_2 in the flue gas of coal-fired power plants and its use for biomass energy has become an important core technology in the low carbon cycle, and it is one of the effective ways to achieve the "double carbon" goal in China. However, the high CO_2 concentration in flue gas(relative to the natural air atmosphere for algae growth) and the presence of easily soluble acidic gases such as SO_2 pose a great challenge to the photosynthetic growth of microalgae and the carbon conversion process, resulting in the limited engineering application of microalgae for flue gas CO_2 capture. In order to promote the development of microalgae for flue gas CO_2 fixation, this paper presented a comprehensive review from the construction of efficient algal species tolerant to flue gas atmosphere, the regulation of metabolism and conversion processes of microalgae for high carbon concentration to the transport and conversion processes of high CO_2 concentration from flue gas in photobioreactors. The results show that Chlorella is the most potential algae species to be used for the biological fixation of flue gas CO_2. Through screening and domestication, Chlorella can adapt to the high carbon concentration of flue gas and the stress of acidic gases at certain concentrations, while maintaining a high rate of carbon fixation. In addition, the dissolved transport and multiphase flow of flue gas in the photobioreactor are the key factors affecting the carbon fixation performance of microalgae. Enhancing CO_2 transport and inhibiting the dissolution of SO_2 acidic gas in the reactor are also effective means to improve the photosynthetic carbon sequestration of microalgae. The use of microalgae biomass is an effective means of carbon sequestration. The use of microalgae biomass can effectively increase the economics of microalgae to reduce flue gas CO_2 emissions. This paper presented a summary of the research progress on the use of microalgae biomass as an energy resource, including the process flow and related research progress of microalgae transesterification for biodiesel, microalgae pyrolysis for bio-oil and biogas, and microalgae fermentation for biosynthesis gas. In order to improve the economic efficiency of microalgae biomass resources utilization, the direction of utilization of microalgae as a raw material for the synthesis of high-value products, as well as the way of resource utilization of algal sludge as a carbon-based material were pointed out. The direction of high-value energy-based resourceful tertiary utilization of microalgae-based biofuels and biochar and other products in collaboration, which with the premise of developing high-value utilization was proposed as a way to improve the economics feasibility of microalgae bio-fixed flue gas CO_2 systems. While it can promote the research of new energy sources of microalgae biomass. This paper provids some guidance for the biological emission reduction and resourceful utilization of flue gas CO_2 in China, aimed at promoting the development of green carbon economy.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 16944K]

  • Effect of batch addition of NH_4HCO_3 on chemical absorption and microalgae conversion hybrid system

    LI Pengcheng;LI Meidi;YIN Qingrong;MAO Weiwei;SONG Chunfeng;School of Environmental Science and Engineering,Tianjin University;

    Carbon capture and resource utilization are of great significance to alleviate environmental problems such as global warming and glacier melting, and it is one of the effective ways to achieve carbon neutrality. The conventional CO_2 capture way by chemical absorption has the problem of high energy consumption. Due to the low solubility of CO_2 in the medium, CO_2 escape is often caused when fixed by microalgae, then resulting in low carbon fixation efficiency and secondary CO_2 emissions. Chemical absorption and microalgae conversion hybrid system has the potential advantages of reducing renewable energy consumption and improving CO_2 resource utilization.Ammonia was used as a chemical absorber, and NH_4HCO_3 generated after fully absorbing CO_2 partially replaced NaNO_3 in the process of traditional microalgae culture. In order to reduce the toxicity of high concentration NH_4~+-N to Spirulina and further reduce the nitrogen source cost of the coupling system, the nitrogen source composition was optimized by batch addition of NH_4HCO_3. Results shows that batch addition of NH_4HCO_3 can reduce the required total nitrogen content and promote the synthesis of lipid without affecting the growth of Spirulina. When 50 mg/L NH_4HCO_3 is added every 6 days, the nitrogen fixation rate and carbon fixation capacity are the highest, which are 32.33% and 149.24 mg/(L·d), respectively, and the maximum biomass is 1.30 g/L on the 12 th day. In addition, the components of Spirulina in the coupling system are affected by different feding-batch modes. Supplementation of 50 mg/L NH_4HCO_3 every 6 days is beneficial to the production of protein, which reaches 889.17 mg/L. Adding 75 mg/L NH_4HCO_3 every 6 days is conducive to the accumulation of carbohydrates in Spirulina, reaching 1 632.86 mg/L. This study provides guidance for the further application of the chemical absorption and microalgae conversion hybrid system by batch feeding mode, and has the potential and application prospects.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 11302K]

  • Research progress on photocatalytic or electrocatalytic coupling of carbon dioxide with organic compounds

    WANG Ruoyu;LI Jinhao;NING Chenjun;TIAN Qiang;ZHAO Yufei;State Key Laboratory of Chemical Resource Engineering,Beijing University of Chemical Technology;College of Chemistry,Beijing University of Chemical Technology;Shandong Vansivena Material Technology Co.,Ltd.;

    CO_2 resource utilization is an important way to reduce CO_2 emissions and achieve carbon neutrality. Among them, the coupled catalytic conversion of CO_2 with organic compounds has been considered as an effective and promising way to the resource utilization of CO_2.The classical thermal catalytic coupling reaction are limited in their application due to the high energy consumption and increased carbon emissions caused by the more violent reaction conditions. Recent research shows that photocatalytic and electrocatalytic carbon dioxide coupled with organic compounds can directly utilize clean energy, which not only realizes the CO_2 emission reduction and promotes sustainable development, but also can obtain high value-added chemicals such as carbonate and carboxylic acid, thus creating more economic value. The catalysis of this kind of reaction is usually based on the activation of organic molecules, supplemented by the activation of CO_2 molecules. The substrate molecules are activated by light or electricity to generate high-energy active intermediates, so that the reaction can overcome thermodynamic obstacles. In this review, we summarized the recent advances of photocatalytic and electrocatalytic carbon dioxide coupled with organic compounds from the advantages of photocatalytic and electrocatalysis, reaction efficiency and reaction conditions. The activation strategies for different types of organic compounds and the reaction mechanisms of various reactions were discussed in detail. Finally, the current challenges in this field and the future development prospects were proposed. Photocatalysis is mainly used for CO_2 insertion of C—O bond and C—H bond, and the main products are esters and carboxylic acids, respectively. The reactions are mostly carried out at ambient temperature and pressure. The cycloaddition reaction of CO_2 and epoxide has been widely studied, and its heterogeneous catalytic reaction has an ideal conversion rate and selectivity. The reaction of CO_2 with hydrocarbons can achieve ideal carboxylic acid yield with suitable substrates, but it needs the catalysis of homogeneous catalyst. In addition, the common problems in photocatalytic reactions, such as low reaction rate and difficult use of visible light, need to be solved. Electrocatalysis is mainly used for CO_2 insertion into C—X bond and ■ bond at the cathode. The main products are carboxylic acid and dicarboxylic acid, respectively. The reactions are mostly carried out at ambient temperature and pressure. Among them, C—X bond reduction carboxylation can be carried out efficiently on the electrode surface or in the presence of catalyst in solution, but the reaction often generates alkanes and other by-products. Reductive carboxylation of ■ bond does not require catalyst, but there is competition between monocarboxylic and dicarboxylic acids, and the product is more complex when the substrate is conjugated diene. In the study of this system, active metals are often used as sacrificial anodes. Therefore, in addition to improving the selectivity of a certain product, the efficient utilization of anodes should also be considered in the future study of this type of electrocatalytic reaction.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 23844K]

  • "Enzyme + X" coupled catalytic conversion of CO_2

    LIU Shusong;ZHANG Boyu;WU Zhenhua;ZHAO Xiyao;SHI Jiafu;School of Environmental Science and Engineering,Tianjin University;

    "Carbon peaking and carbon neutrality" is a major strategic decision made by our country to coordinate domestic and international situations. It is a solemn commitment to address prominent resource and environmental constraints and to build a community of human destiny. Carbon capture and storage(CCS), as a traditional carbon dioxide(CO_2) control method, has potential leakage risk and a huge economic burden. In recent years, carbon capture, utilization and storage(CCUS) has been regarded as an effective alternative and supplement to CCS because it can convert the captured CO_2 into value-added products for resource utilization. The development of efficient CO_2 utilization technologies is the key to CCUS. Enzyme-catalyzed technology, as a typical green biomanufacturing technology, has received extensive attention in the field of CO_2 utilization. The coupled catalytic systems based on enzyme catalysis open a rich pathway network for the resourceful conversion of CO_2 into high-value chemicals or fuels. In this review, the "Enzyme +X" coupled catalytic systems for CO_2 conversion in recent years was summarized and highlighted, including "Enzyme + Enzyme" coupled catalytic system, "Enzyme + Chemo" coupled catalytic system, "Enzyme + Photo" coupled catalytic system and "Enzyme + Electro" coupled catalytic system. The structures of different coupled catalytic systems were analyzed, and their system characteristics and catalytic processes were clarified. On the basis of structural analysis, the key to system module design and performance enhancement was discussed. The advantages and disadvantages of the "Enzyme + X" coupled catalytic system in CO_2 resource conversion were expounded, and suggestions for its future development were provided. In an "Enzyme + Enzyme" coupled catalytic system, the pathway designability of CO_2 conversion to target products is enriched, which can ensure the final products with higher value through the cascade reactions, thus greatly improving the economic efficiency. In an "Enzyme + Chemo" coupled catalytic system, the chemical catalytic process is usually applied to pre-convert CO_2, after which the enzyme catalytic process directly uses C_1 compounds as the starting materials, showing unique advantages in catalyzing the conversion of CO_2 into C_2/C_(2+) and other multi-carbon compounds. In an "Enzyme + Photo" coupled catalytic system, light energy is utilized by semiconducting materials to trigger the catalytic regeneration of coenzyme, avoiding the consumption of exogenous reduction equivalents in coenzyme-dependent enzymatic catalytic reactions. In an "Enzyme + Electro" coupled catalytic system, the electron transfer between the electrode and the enzyme can be regulated by altering the external bias voltage, which is rather crucial for driving the enzymatic hydrogenation in a high efficiency manner. The "Enzyme +X" coupled catalytic system can compensate for the drawbacks of the sole or single enzyme catalytic system to convert CO_2 into energy-carrying compounds, which shows unique advantages and broad application prospects. However, the coupling of different catalytic systems increases the complexity of the system and requires precise construction of the coupled system. Meanwhile, the enzyme as a typical protein molecule may also affect the application of the "Enzyme +X" coupled system in some extreme external conditions. Although CO_2 capture and storage is still the major strategy to achieve the goal of "carbon peaking and carbon neutrality" in near future, CO_2 utilization technologies, including "Enzyme +X" coupled catalytic CO_2 conversion technology, will gradually become a trend, which is expected to truly achieve the carbon neutralization goal the future.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 69672K]

  • Research progress on carbon dioxide catalytic hydrogenation to methanol based on low-temperature plasma

    HAN Fenglei;LIU Xiaolin;SI Peizhuang;JIA Jilei;JI Chunjie;ZHU Yifan;ZHANG Yupeng;School of Chemical Engineering,China University of Petroleum;Shenzhen Branch,CNOOC (China) Co., Ltd.;

    While the rapid development of society has brought people a prosperous life, it also brings people a series of negative impacts such as the greenhouse effect and environmental degradation. As one of the eight key tasks, "carbon neutralization and carbon peaking" is constantly being mentioned, which puts forward higher requirements for environmental protection. Therefore, the control of CO_2 emissions, its recovery, fixation, utilization and recycle, as well as the reduction of the concentration of CO_2 in the atmosphere, has become the issues of great concern for all countries in the world. However, the CO_2 molecule is very stable, and its decomposition and activation usually requires the input of high temperature, catalyst and energy such as light and electricity, and high temperature can easily lead to the deactivation of the catalyst. Current CO_2 conversion technologies, such as catalytic conversion and biochemical processes, have disadvantages of catalyst deactivation and high energy input. Compared with the above technologies, plasma technology has the advantages of simple operating conditions, easy upgrading, and low energy cost. Using plasma technology, CO_2 can be converted into fuels and chemicals with high added value at room temperature and atmospheric pressure. When the plasma technology is combined with the catalyst, the CO_2 conversion rate is further improved. Among many CO_2 utilization technologies, the hydrogenation of CO_2 is conducive to the generation of high-energy-efficiency value-added products, which has practical significance and broad prospects. By investigating and reviewing the influence of catalyst type, reactor structure and operating conditions in the process of plasma catalytic CO_2 hydrogenation to methanol, it can provide a better reference for CO_2 resource utilization. Studies have shown that when plasma is combined with catalysts, it is more conducive to methanol synthesis, so more attention should be paid to catalysts with higher activity, lower cost, and simpler preparation methods in the future. At the same time, the structure of the reactor will also affect the CO_2 conversion rate. Further innovation of the reactor can be considered. At present, the low-temperature plasma reactor with a cooler catalyst bed is more suitable for CO_2 hydrogenation to methanol. However, the low-temperature plasma catalytic CO_2 hydrogenation to methanol reaction process is relatively complex, and the exploration of the CO_2 conversion mechanism requires more modeling.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 7009K]

  • Improvement of control strategy of CO_2 capture from biomass CHP plant by chemical absorption

    LIU Shengchun;HU Changzheng;DONG Beibei;Tianjin Key Lab of Refrigeration Technology,Tianjin University of Commerce;School of Business,Society and Technology,M?lardalen University;

    When capturing CO_2 from biomass fired combined heat and power(CHP) plants, the changes in the feedstock and the heat and electricity demands affect the performance of chemical absorption CO_2 capture system. To handle such impact, this paper proposed an improved reboiler duty control strategy(control strategy B) based on the evaluation of the control performance of the traditional feedback control strategy(control strategy A) to achieve a constant capture rate. Control strategy B is based on control strategy A, and introduces feedforward compensation based on rich solution flow rate to form a feedforward plus feedback control strategy. This work aimed to find a control strategy suitable for chemical absorption CO_2 capture from biomass CHP, by comparing the control performance, capture system performance and flexible operation performance of both control strategies. Based on the dynamic simulations of CO_2 capture from actual biomass fired CHP plant, it is found that compared with the control strategy A, the feedforward compensation of the control strategy B can reduce the response time of the reboiler duty to external disturbances, and improve the timeliness and accuracy of the regulation of reboiler duty. The settling time of capture rate is reduced by 54 mins with the control strategy B. Facing the flexible change of capture rate setpoint, the time required for the stabilization of capture rate is reduced by 57.9% with control strategy B. Under the continuous external disturbance, the capture rate is maintained at ±3% of the setpoint with control strategy B. At the same time, the energy penalty is reduced by 0.14%, and the total captured CO_2 is increased by 0.35%. In addition, the results of dynamic simulation and traditional steady-state simulation show that the dynamic simulation can reflect the impact of external disturbances on the capture system more accurately, and provide a reference for the integration and optimization of related processes.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 24349K]

  • Research progress on carbon dioxide capture using solid-liquid phase-change absorbents

    TU Zhifang;WEI Jianwen;ZHOU Xiaobin;College of Environmental Science and Engineering,Guilin University of Technology;Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology,Guilin University of Technology;

    Chemical absorption based on organic amine is one of the effective technologies for post-combustion CO_2 capture. However, the high regeneration energy consumption of the traditional organic amine process restricts its industrial application. To reduce the energy consumption of CO_2 capture, phase-change absorbents came into being. This new class of absorbent can change from homogeneous phase to two immiscible phases after absorbing CO_2, and CO_2 is enriched in one phase. Since only the CO_2-rich phase is separated for regeneration, the regeneration volume can be greatly reduced and the regeneration energy consumption of CO_2 captured can be significantly reduced. Phase-change absorbents include liquid-liquid phase-change absorbents and solid-liquid phase-change absorbents. The latter absorbs CO_2 to form solid precipitate that can be rapidly separated from the solution, which has become the research focus of new absorbents in recent years. According to the composition analysis, solid-liquid phase-change absorbents can be classified into three categories: organic amine non-aqueous solutions, aqueous salt solutions and ionic liquid-based solutions. Organic amine nonaqueous solution uses organic amine as the absorption active component and organic solvent as the phase separation agent, which has the advantages of fast absorption rate and low corrosiveness. However, after absorbing CO_2, their solid products are prone to form sticky gel and difficult to decompose. The salt solutions, which include amino acid salt and carbonate aqueous solution or water-lean solution, have the advantages of low cost and easy availability of raw materials. However, the solid-liquid phase-change characteristics and phase separation efficiency of existing salt phase-change absorbents need to be further improved. The ionic liquid-based solutions include two kinds of systems of conventional ionic liquids(act as solvents)/organic amines(act as active components) and functionalized ionic liquids(act as active components)/organic reagents(act as solvents), which have the properties of good thermal stability and high regeneration efficiency, but ionic liquids are complex to synthesize and their cost is relatively high. In a word, compared with traditional aqueous organic amine absorbents, solid-liquid phase-change absorbents have a greater energy saving potential and can be expected to be a promising alternative for CO_2 capture with high efficiency and low-energy consumption. At present, the development of solid-liquid phase-change absorbents is still in the stage of experimental research. To promote its practical application, the future work should focus on the design principle of absorbents, phase-change mechanism, thermodynamics, kinetics, and the optimization of CO_2 capture process.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 15483K]

  • Research progress and prospects of mild oxidative depolymerization of low-rank coals

    CHEN Jie;WANG Yugao;WANG Zhilei;SHEN Jun;NIU Yanxia;LIU Gang;SHENG Qingtao;College of Chemical Engineering and Technology,Taiyuan University of Technology;

    The implementation of "carbon peak and carbon neutral" policies will greatly limit the fuel-use of coals. The low-rank coal is abundant in China, and it is not only inefficient to use it directly as energy, but also causes greater pollution. It is expected to develop a new process for production of carboxylic acid chemicals as well as expand the utilization of coal resources through the preparation of carboxylic acid chemicals by mild oxidative depolymerization of low rank coal. According to the difference of the methods, mild oxidative depolymerization of low-rank coals can be classified into non-catalytic oxidation(including chemical reagent oxidation and pretreatment oxidation), catalytic oxidation and in-situ oxidation. The development and characteristics of different oxidation methods for producing carboxylic acid chemicals from low-rank coals were mainly summarized. In non-catalytic oxidation, chemical reagent oxidation is easy to be carried out. Whereas it will cost a large consumption of chemical agents and the oxidation process is not easy to be controlled. At the same time, heteroatoms will be introduced into the resulting products for some oxidizing reagents such as nitric acid and sodium hypochlorite resulting in increasing difficulties of product separation. Pretreatment oxidation can improve the yield of products and utilization rate of low-rank coals, while the pretreatment process is relatively complicated. Catalytic oxidation method can speed up the reaction rate, and reduce investment and energy consumption. The stability, selectivity and efficiency of the catalyst need to be further studied, and the catalyst recovery should also be paid more attention. In-situ oxidation is flexible and controllable, which is expected to regulate the oxygen depolymerization process of low-rank coals. In the end, the current problems and future development direction of mild oxidative depolymerization of low-rank coals were discussed.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 20189K]

  • Adsorption characteristics of coal-based briquetted activated carbon for water deep purification process

    LU Xiaodong;MA Rongfu;XIE Wei;DU Huihui;MEI Shengquan;Activated Carbon Branch, Xinjiang Energy Co., Ltd.,CHN Energy;Beijing Research Institute of Coal Chemistry, CTEG China Coal Research Institute;State Key Laboratory of Coal Mining and Clean Utilization;

    Activated carbon as a key material applied to the deep purification treatment process of water is mature and reliable. The municipal water production in most cities in China adopts the activated carbon water deep purification process. The activated carbon was used as an adsorbent to purify the typical pollutants in water. The adsorption characteristics of activated carbon in the advance purification process of drinking water was researched to provide a basis for the selection of activated carbon in drinking water treatment. High-efficiency briquetted activated carbon prepared from Xinjiang coal was used as the adsorbent to treat the raw water of the Huangpu River. The UV_(254) and COD(Mn) of the water were used as the evaluation indexes of the advance purification effect. The data of static adsorption test were fitted by adsorption isothermal model and quasi-secondary kinetic model to evaluate the adsorption properties of pollutant in water samples by activated carbon. The removal effect of pollutant by activated carbon at different water fluxes was studied. The raw water of Huangpu River was treated by upper flow aeration biosorbent device, and the service period was calculated. Optimal regeneration conditions of activated carbon were analyzed. The results indicate that the equilibrium adsorption capacity of activated carbon for substances represented by UV_(254) and COD(Mn) index in the water is 0.481(cm·g)~(-1) and 13.889 mg/g, respectively. Compared with the substances represented by COD(Mn), activated carbon absorbed substances represented by UV_(254) faster. Dynamic experiment was used to study the treatment effect of activated carbon. When water fluxes ratio reaches 6 990, the adsorption of activated carbon to substances represented by UV_(254) and COD(Mn) basically reaches equilibrium. At this time, the removal rate of UV_(254) is reduced to 50%, and the removal rate of COD(Mn) is reduced to 5.9%. Comparing the physico-chemical parameters of adsorption of saturated activated carbon with new activated carbon, it is found that the particle size of saturated carbon becomes smaller and the loading density and strength increases under the action of long-term water flow scour and water flow shear force. The service life of activated carbon is mainly reflected through its physical life. According to the loss degree of activated carbon layer and particle size in the process of aeration and backwashing, the service life is estimated to be about 9.2 years. After comprehensive analysis of the regeneration rate of activated carbon, recovery of adsorption properties and regeneration cost, the optimal time of regeneration is 3 hours, and the activated carbon is regenerated 3 times when the regeneration temperature is 850 ℃ and the water vapor flow rate is 80 m~3/min.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 15074K]

  • Process design for desulfurization wastewater by flue evaporation treatment

    LI Hengfan;JIAO Shiquan;HAN Zhonghe;Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology,North China Electric Power University;

    Desulfurization wastewater has special water quality and high water pollution. Flue evaporation technology of desulfurization wastewater has engineering practical value for the treatment of desulfurization wastewater. Aiming at the application of flue evaporation technology of desulfurization wastewater in engineering practice, the heat and mass transfer model of atomized droplets in the tail flue was established, and the evaporation characteristics of a large number of desulfurization wastewater in the tail flue of a 300 MW boiler were calculated by numerical simulation. The safe distance between the nozzle and the flue wall was calculated under different nozzle flow rates to determine the layout area of the nozzle in the flue section.Combined with the total amount of desulfurization wastewater, the number and location of the nozzle were determined, and the effects of flue gas temperature, velocity and droplet size on the droplet evaporation time and distance were analyzed. The results show that the safe distance increases with the increase of the spray flow rate and the droplet size, the decrease of the flue gas temperature and velocity and the increase of droplet size, so that the safe area gradually decreases. Due to the action of gravity, the safe distance between the nozzle and the lower wall is the largest. When the total amount of desulfurization wastewater is fixed, with the increase of the number of nozzles and the decreases of the spray flow of a single nozzle, the evaporation time and distance of the atomized droplets shorten, so that more wastewater can be treated within a certain distance. When the total amount of desulfurization waste water increases, the more the number of nozzles is, the smaller the increase value of the flow of a single nozzle is, and the smaller the increase of evaporation distance is, making the maximum treatment capacity stronger. With the same number of nozzles, the increase of flue gas temperature, flue gas velocity and droplet size will reduce the evaporation time and shorten the evaporation distance. In practical application, the actual situation of the unit should be combined to choose the appropriate nozzle layout and design the waste water flue evaporation system reasonably.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 16512K]

  • Effect of magnetite on the sedimentation characteristics of coal slurry

    WU Shanshan;JIANG Peng;LI Kanzheng;WANG Ruotong;WAN Siming;HUANG Gen;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;

    The content of fine mud in the raw coal of coal preparation plant is getting higher and higher with the increase in the mechanization of coal mining. Problems such as poor settlement effect and high overflow concentration often appear when the traditional slime water treatment technology is used to treat high ash and fine coal slurry. As an efficient flocculation method, magnetic flocculation has been widely used in water treatment, but there is less research on the difficult to settle coal slurry water produced by coal preparation plant. Fine coal slurry from a coal preparation plant in Inner Mongolia was used in this study. The effects of magnetite alone and together with polyaluminum chloride and cationic polyacrylamide on the sedimentation characteristics of coal slurry were studied. The stability of the coal slurry system with different magnetite dosages was studied by the Turbiscan analyzer, and the influence of the amount of magnetite powder on the zeta potential of particle surface was studied by Zeta potential analyzer. The results show that when the magnetite is used alone, the turbidity of the supernatant decreases with the increase in magnetite dosages, and then increases, while the sedimentation velocity increases with increasing magnetite dosages, and then decreases. When the magnetite dosage is 48.00 kg/t, the turbidity of the supernatant reaches the lowest value(53.50 NTU), while the sedimentation velocity reaches the maximum value(3.89×10~(-3) mm/s). When magnetite and PAC is used, the change of the turbidity of supernatant and the sedimentation velocity shows the same trend as the magnetite used alone with the increase of the amount of magnetite powder, and the stability index(ITS) value first increases and then decreases, indicating that with the increase of the amount of magnetite powder, the sedimentation effect of slime water gradually improves. The results of the Turbiscan analyzer shows the coal slurry became steady when excessive magnetite is used, which is not conducive to the settlement of coal slurry. When magnetite, PAC and CPAM are added into coal slurry with the dosages of 10.00 kg/t, 2.00 g/t, and 1.00 g/t, respectively, the initial sedimentation velocity and the turbidity of the supernatant are reached 3.09 mm/s and 64.30 NTU, respectively. The sedimentation effect of the coal slurry improves significantly. The Zeta potential value reduces with the increase of magnetite. The flocs with magnetite as the core are formed by the electrostatic adsorption between the particles and the magnetite in the coal slurry. Moreover, magnetite increases the density and sedimentation velocity of the flocs.

    2022 09 v.28;No.145 [Abstract][OnlineView][HTML全文][Download 22429K]
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