- LI Zheng;CHEN Siyuan;DONG Wenjuan;LIU Pei;MA Linwei;HE Jiankun;Institute of Climate Change and Sustainable Development,Tsinghua University;Tsinghua-BP Clean Energy Research and Education Center,Tsinghua University;
Decarbonization of power sector is critical for the emission reduction target of Paris Agreement targets. However,it also faces enormous difficulties and challenges,with strong complexity and uncertainty. In order to explore feasible and affordable decarbonization pathways of China's power sector,a bottom-up energy system model with high spatiotemporal resolution and technical accuracy was built to simulate and optimize the development pathways. Three typical scenarios( Business as usual scenario,2 ℃ scenario and 1.5 ℃ scenario)were set to analyze the decarbonization pathways and the corresponding implementation plan. The results indicate that the 2 ℃/1.5 ℃ targets stipulated in Paris Agreement cannot be realized based on the current development trend,which can only be achieved with faster expansion of renewable energy,quicker phase-out of coal-fired power plants as well as the large-scale deployment of carbon capture technologies. In the next 30 years,wind and solar power should gradually become the majority of power supply. The annual incremental installed capacity should reach 2-4 times of the current level. The capacity of coal-fired power plants needs to shrink gradually and some of them even need to be prematurely decommissioned,which will reduce the average lifetime of coal-fired units by 0.42 to 1.93 years,translating to the stranded cost of 105 billion to 655 billion yuan. Carbon capture technologies need to be largely deployed,especially the coal-biomass co-firing power plants with carbon capture devices. By 2050,the annual captured carbon dioxide should reach 0.89 Gt to 1.08 Gt. In order to guarantee the low-carbon transition progress,some important issues should be dealt with,including power grid security and stability,orderly coal power phase-out,the deployment of carbon capture technologies and transition cost. These issues could be effectively solved by enhancing the research and development of advanced technologies such as energy storage,establishing an orderly phase-out mechanism for coal-fired power plants,accelerating the demonstration of carbon capture and storage technologies and establishing the green investment and financing mechanism. Tackling climate change is the common responsibility of all mankind. Measures and policies should be deployed ahead of time from now on so as to achieve the decarbonization of China's power sector under the 2 ℃/1.5 ℃ targets.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 5323K] - FANG Mengxiang;DI Wentao;YI Ningtong;WANG Tao;WANG Qinhui;State Key Laboratory of Clean Energy Utilization,Zhejiang University;
Due to its high capture efficiency,relatively mature technology and good adaptability,CO_2 chemical absorption technology is currently the most potential CO_2 capture technology for industrial application. However,in CO_2 chemical absorption system,absorbent is used to capture CO_2 in the flue gas,and part of the absorbent and its degradation products are discharged with the flue gas,which not only increases the loss of absorbent,and further reacts in the atmosphere to form strong carcinogen nitrate amine and nitrosamines. Therefore,it is necessary to effectively control the pollutant emission from CO_2 chemical absorption system. At present,pollutants are usually controlled by adjusting the operating parameters of the system and using pollutant control means,but there is no universal control method and the pollutant emission control target value has not been established. In this paper,three emission forms of pollutants in CO_2 chemical absorption system were introduced,including physical entrainment,gas and aerosol. The aerosol has high emission and is difficult to be controlled by traditional methods. According to the emissions measured by the research institutions,CO_2 chemical absorption systems of different scales generally have higher emissions. The mechanism of aerosol generation and growth was analyzed. The aerosol emission is mainly produced through heterogeneous nuclei,which depends on the existence of condensation nuclei and the supersaturated environment. Based on the experimental and simulation methods,the effects of condensation core of flue gas,inlet temperature of lean liquid,lean liquid load and CO_2 content of flue gas on the emission of organic amine dominated by aerosols were reviewed. The research on the emission of degradation products,including oxidative degradation and thermal degradation,was briefly introduced. Finally,the control effect,advantages and disadvantages of the current pollutant emission control methods were summarized. The traditional water washing method can effectively control the gaseous emission of organic amines. The traditional mist eliminator has a good control effect on large-size aerosol particles,but the removal efficiency of small particles is low. Although wet electric dust removal,steam injection,dry bed and other methods have certain removal effect,but the cost is high. Acid pickling can solve the problem of ammonia emission,but it is difficult to recover organic amines.Colloid gas foam method has high efficiency for aerosol removal,but there is a lack of industrial research. In the future,it is necessary to develop new control methods for pollutant emission,which can effectively reduce the emission of pollutants in the form of gas phase and aerosol,and control the industrial investment cost. This method will be the key link for the establishment of advanced carbon capture process system.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 4131K] - WANG Yueming;LIU Huimin;QIU Xinglei;DUAN Lunbo;Key Laboratory of Energy Thermal Conversion and Control,Ministry of Education,Southeast University;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
In recent years,with the continuous development of world economy and the increasing population,energy consumption is continuously increasing. The consumption of fossil energy has caused the increasing CO_2 emission. In order to alleviate the rising trend of global carbon emissions,China has pledged to reach CO_2 emission peak in 2030 and achieve CO_2 emission in 2050. In order to achieve this goal,it is necessary to develop the clean and efficient use of fossil energy. Oxy-fuel combustion is one of the most promising carbon capture technology for coal power plant. In this paper,the particulate matter and ash deposit formation in oxy-fuel combustion were systematically reviewed. The influence mechanism of oxygen concentration,pressure and fuel characteristics on the formation of particulate matter and ash deposition characteristics was introduced. Particulate matters generated from oxy-fuel combustion can be divided into submicron and micron particles. Submicron particles are formed through vaporization,nucleation and coagulation,while micron particles are formed through char fragmentation. Higher oxygen concentration can lead to the increase of flame temperature. On the one hand,more ash is vaporized at high temperature,which promotes the formation of submicron particles; on the other hand,. more alkali contents can be scavenged from submicron particles due to the enhanced interaction between alkali vapors and aluminosilicate particles. It is also found that elevated pressure can inhibit the formation of submicron particles. However,the effect of oxygen concentration and pressure on the yield or composition of micron particles is not obvious. Ash deposits are mainly formed through inertial impaction,thermophoresis,condensation and chemical reaction. More ash deposits are formed under oxy-fuel combustion with higher oxygen concentration,this can be explained from two reasons. Firstly,due to the increase of flue gas temperature,ash particles have lower viscosity and thus are easier to be captured on heat transfer surface. Secondly,more submicron particles can migrate to the surface of heat exchanger to form ash deposits through thermophoresis force. Although compositions of outside deposits are not significantly affected by oxygen concentration,compositions of inside deposits change along with submicron particles because submicron particles contribute the formation of inside deposits. When the pressure increases,the sulfur content in the ash increases and the chlorine content decreases,,but the effect of pressure on ash deposition rate is still unclear.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 21649K] - BAI Xinwei;LIU Jinchang;BAI Lei;Department of Chemical and Biomedical Engineering,West Virginia University;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;
Chemical looping combustion of coal is one of the most vital technologies for clean coal combustion. A metal-based oxygen carrier in chemical looping process is applied to avoid direct contact between the coal and air,which can eliminate the production NO_x pollutants and improve energy conversion efficiency. In general,there are two reaction pathways for chemical looping combustion of coal: in situ gasification chemical looping combustion(iG-CLC) and chemical looping with oxygen uncoupling(CLOU). The difference in combustion pathway will greatly affect the composition and structure design of oxygen carriers. The research progress of solid metal-based oxygen carriers in coal chemical looping combustion from 2015 to 2020 was discussed in detail,including iron-based,manganese-based,copper-based,nickel-based,calcium sulfate,and other composite oxygen carriers. The advantages and disadvantages of different metal oxygen carriers,reaction path,gas-solid and solid-solid reaction mechanism,interaction between metal and carrier and deactivation principle of oxygen carrier were summarized. Iron-based oxygen carriers are widely applied in iG-CLC system,but the reaction rate of single iron-based oxygen carrier is low. The addition of alkali and/or alkaline-earth metals can improve the reactivity of the iron-based oxygen carriers. on the one hand,manganese-based oxygen carrier can release gaseous oxygen in high temperature and anoxic atmosphere;and on the other hand,the manganese-based oxygen carrier can oxidize reducing gas such as CO and CH_4. By applying inert support materials and alkali metal promoters,the mechanic strength and oxygen decoupling ability can be further boosted. Copper-based oxygen carrier has attracted much attention due to good oxygen uncoupling behavior. However,the deactivation of oxygen carriers due to metal aggregation caused by low melting point of copper and its oxides needs to be overcome. Besides,several research works observed that using iron,manganese and/or copper ore as oxygen carriers can improve the reactivity. The reactivity of calcium sulfate oxygen carrier is excellent,but the possible side-products in coal chemical looping combustion such as sulfur dioxide and hydrogen sulfide need to be addressed.Nickel-based oxygen carrier has good reaction performance in chemical looping combustion of coal,but there are only a few recent studies because of the disadvantages of nickel-based oxygen carrier,such as sulfur poisoning,comparably higher cost,and environmental-unfriendly. Novel bimetallic and multi-metallic oxygen carriers can combine the reaction characteristics of the two metals at the same time,thus significantly improving the overall reactivity of the oxygen carriers. Based on the recent advances of oxygen carrier research,this review suggests four possible areas to explore in the future: 1,combining iG-CLC and CLOU pathways to design novel chemical looping assisted by oxygen uncoupling(CLOU) carriers; 2,developing oxygen carriers with novel support material and metal composition; 3,utilizing metallurgical waste as raw material to synthesize oxygen carriers; 4,designing oxygen carriers with special structures,including coreshell and skeleton structures.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 1641K] - CHENG Pengfei;LI Pengfei;HU Fan;LIU Lu;WANG Feifei;ZHANG Jianpeng;MI Jianchun;LIU Zhaohui;ZHENG Chuguang;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;School of Environmental Science and Engineering,Huazhong University of Science and Technology;School of Aerospace Science and Engineering,Sichuan University;College of Engineering,Peking University;
Flameless oxy-fuel combustion of pulverized coal is one of the development directions of clean coal combustion technology,which can obtain high concentration of CO_2,significantly reduce NO_x emissions,and improve the combustion stability and thermal performance. Computational fluid dynamics( CFD),as one of the important means of combustion research,has the advantages of fast running,low cost,and rich data,which effectively promotes the development of flameless oxy-fuel combustion technology. Based on our long-term research experience on oxy-fuel and flameless combustion of pulverized coal,the CFD simulation method and research progress of flameless oxy-fuel combustion of pulverized coal were summarized. The experimental and mathematical definitions of coal flameless combustion were firstly introduced,which were different from the flameless combustion of gaseous fuels due to the heterogeneous reaction. Then the progress of the CFD methods for flameless oxy-fuel combustion of pulverized coal was discussed in detail,including the sub-models and mechanisms of flow,heat transfer,combustion and pollutant formation. The simulation accuracy and calculation efficiency of flameless oxy-fuel combustion of pulverized coal can be significantly improved by using the realizable k-ε turbulence model considering strong flue gas entrainment,P1 or DO radiation model,WSGG gaseous radiation model modified for oxy-fuel condition,CPD devolatilization model,finite-rate EDC homogeneous combustion model considering turbulence-chemistry interaction,homogeneous reaction mechanisms developed for flameless and oxy-fuel combustion,multi-step surface heterogeneous char burnout model,detailed reaction mechanisms for nitrogen conversion and dynamic adaptive chemistry for calculation acceleration. Next,the numerical studies on flameless oxy-fuel combustion of pulverized coal were reviewed in the aspects of benchmark experiments,micro reaction zone analysis,macro reaction characteristics,pollutant formation and conceptual designs of large-scale boiler. Finally,the development direction of CFD research on flameless oxy-coal combustion were proposed,such as large eddy simulation,combustion models,high-precision detailed reaction mechanisms,dynamic adaptive chemistry modeling,and industrial application optimization.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 7854K] - ZHANG Jie;GUO Wei;ZHANG Bo;ZHANG Rongjiang;YANG Bolun;WU Zhiqiang;Shaanxi Key Laboratory of Energy Chemical Process Intensification,School of Chemical Engineering and Technology,Xi'an Jiaotong University;
Reducing carbon emissions and promoting carbon neutralization is one of the critical ways to deal with climate change and encourage the green transformation of economy and society. Carbon neutralization technology has become the focus of industry and academia.At present,carbon capture and storage technology(CCS) is mainly used to treat and capture CO_2 emitted from industrial fixed sources,while the distributed sources,accounting for nearly 50% of total CO_2 emissions are not highly concerned. Direct air capture(DAC) technology can not only capture CO_2 emitted by millions of small-scale fossil fuel combustion devices and hundreds of millions of vehicles,but also effectively reduce the concentration of CO_2 in the atmosphere. The development history,research status,and development trend of DAC were introduced. The existing DAC technology process flow and reaction equipment were summarized. The air capture module,absorbent or adsorbent regeneration module and CO_2 storage module involved in DAC current process were described. The advantages and disadvantages of several processes,adsorbent types and regeneration methods were compared. It was pointed out that the key to the development of DAC technology lied in developing high-efficiency and low-cost absorption and adsorption materials and equipment. The functional principle and adsorption effect of DAC absorption/adsorption material was analyzed. The raw material cost of alkaline solution is relatively low,but the energy consumption is high in the regeneration process of alkaline solution. Although the regeneration energy consumption of molecular sieve and metal-organic framework adsorbent is low,the adsorption capacity and adsorption selectivity of CO_2 in air are average. However,amine adsorbents show good adsorption capacity,and industrial waste heat or a small amount of heat energy is used to supply energy for the system because of its low regeneration temperature. In addition,when amine adsorbents are used,adsorption and desorption gradually occur in one unit,which has higher efficiency and operation time,and is expected to reduce the cost of DAC system. The cost of DAC and other carbon capture technologies are compared,and the technical and economic analysis is carried out. The cost of DAC mainly includes operation and maintenance costs(N_(Q&M)),adsorbent material costs(N_S) and net cost of factory equipment(N_(bop)). One of the main factors limiting the industrial application of DAC is the high cost of absorption/adsorption materials and related processes. With the emergence of new adsorbents such as anion exchange resin and the development of technology,the cost of DAC will decrease year by year. It is the current development directions and urgent needs of the DAC field: to comprehensively explore the comprehensive properties of absorption/adsorption materials such as stability,kinetics,adsorption capacity,selectivity,regeneration energy loss,and develop related devices that facilitate rapid loading and unloading of adsorbents,and develop low-cost process systems. DAC technology will provide important technical support for reducing global carbon emissions and achieving carbon neutrality.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 5579K] - YU Yang;LIU Qi;LYU Jing;LUO Dan;PENG Bo;Beijing Key Laboratory for Greenhouse Gas Storage and CO2-EOR,The Unconventional Petroleum Research Institute,China University of Petroleum-Beijing;College of New Energy and Materials,China University of Petroleum-Beijing;
The use of fossil fuels is the main cause of global warming. The technology of carbon capture,utilization and storage(CCUS) can effectively reduce carbon emissions and alleviate the pressure of climate change. Chemical absorption is one of the important methods of CO_2 capture,which has the advantages of high separation efficiency and low cost. But there are some problems,such as high energy consumption in the desorption process,long-term use of equipment corrosion and so on. The enhanced chemical absorption of CO_2 by carbonic anhydrase( CA) can improve the absorption efficiency and effectively solve the heat loss in the traditional process,which has gradually become a hot spot in the research of CCUS. However,CA has some disadvantages such as low thermal stability and poor repeatability,so it needs to be immobilized to improve its stability and activity. he immobilization methods and common carrier materials of CA were mainly introduced,the mechanism of CA in strengthening CO_2 capture was summarized,its application in CO_2 capture was discussed,and the development of this technology was looked forward to. The carrier and method of immobilization will affect the properties of immobilized enzyme,so the appropriate carrier and method should be selected during the immobilization of CA. CA immobilization methods include adsorption,embedding,covalent binding and cross-linking,and each method has its own advantages and disadvantages. The appropriate immobilization method should be selected according to the field of enzyme application. The commonly used immobilized carriers are natural polymers,inorganic carrier materials and so on. The physical and chemical properties and industrial application ability of the carriers should be taken into account when selecting them. In the process of CO_2 capture,CA enhances the capture efficiency mainly by promoting the absorption of CO_2 by chemical solvents and inducing CO_2 mineralization to form calcium carbonate. The future research direction should focus on the development of novel CA with higher activity and stability,the preparation of cheap and high-performance carrier materials,and further explore the obstacles to the industrial application of CA caused by internal factors and external conditions.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 7517K] - LIU Dunyu;CAI Yuyang;JIN Jing;XU Kailong;School of Energy and Power Engineering,University of Shanghai for Science and Technology;Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering;
With the rapid development of industry,the consumption of fossil fuels is increasing with each passing day,resulting in a large amount of greenhouse gas CO_2 emissions.The situation for global climate change is not optimistic.In order to reduce the emission of CO_2,it is necessary to capture,utilize and store the high concentration of CO_2.Oxy-fuel combustion technology can effectively achieve carbon capture,which is considered as one of the most potential carbon emission reduction technologies.In the process of oxy-fuel combustion,the existence of pollutants(including SO_x,NO_xand Hg) and inert gas is not conducive to carbon capture and storage.Since the concentration of various components in flue gas will affect pipeline transportation,geological storage,and enhanced oil recovery(EOR),the different standards of CO_2 and various impurities concentration in flue gas were introduced firstly,and the research progress of desulfurization,denitrification,mercury removal,inert gas removal,and combined removal technologies at home and abroad was systematically reviewed.In addition to the introduction of traditional desulfurization technology,the influence of CO_2 atmosphere in oxy-fuel combustion flue gas on SO_x removal and the conversion and removal of SO_2 under pressure were mainly described.It is found that the absorption rate of SO_2 in CO_2 atmosphere is lower than that in N_2 atmosphere,and the critical pH changes during the absorption process.In the denitration section,the denitration technology by oxidation absorption method and the oxidation mechanism of NO under high pressure were mainly described,and the oxidation kinetics of NO under high pressure was described.With the increase of pressure,the NO oxidation rate constant first decreases and then increases,which is proved that the effect of reactor pressure on liquid entrainment rate is significant.The effects of different flue gas components on Hg oxidation in Hg removal technology were summarized.HCl and Cl_2 play a significant role in promoting Hg oxidation.The activated carbon is modified to increase the specific surface area of pore structure and the active sites on the surface of adsorbent,so as to improve the removal efficiency of Hg.In this paper,the purification technology of inert gas was introduced.Pressure swing adsorption method is mainly used to adsorb and desorb,which reduces the cost of inert gas removal in CO_2 gas flow,realizes a part of inert gas recycling back to the boiler,and improves CO_2 capture.The combined removal technology in the flue gas compression liquefaction system is mainly discussed,which effectively uses the compression process conditions to remove SO_x,NO_x and Hg in the form of sulfuric acid,nitric acid and Hg(NO_3)_2.With the increase of pressure,the removal efficiency of SO_x and NO_x increases,which is conducive to the formation of SO_4~(2-),NO_3~-,HADS and HAMS(N-S compounds),and also leads to the increase of N_2O production.It is proved that the reaction of Hg with NO_2 is a gas phase reaction,and the uncertainty of the product of the reaction of NO_2 with Hg under high pressure is proposed.The low temperature carbon capture technology is briefly introduced,which has the potential to replace the scrubber and other flue gas treatment methods,but there is still a lack of feasibility research.In the future,it is necessary to explain the change trend of NO oxidation rate constant under different pressures,analyze the products of NO_x and SO_x combined removal and the reaction products of NO_2 and Hg under high pressure.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 10425K] - WU Ye;FENG Mingqian;FANG Jing;LIU Dong;ZHANG Rui;YING Yaoyao;XU Lei;School of Energy and Power Engineering,Nanjing University of Science and Technology;
Ammonia is not only an important chemical raw material and a good hydrogen carrier,but also its properties as a carbon-free fuel has attracted widespread attention. A synthetic ammonia process with low energy consumption and high efficiency is the key to realize the application of ammonia as fuel. In this paper,the development of ammonia synthesis process was described,and the new development of ammonia synthesis process driven by heterogeneous catalysis and external field forces such as light and electricity based on Haber Bosch process was summarized. The latest research results of chemical looping ammonia synthesis were mainly introduced,and the research direction was prospected. Due to the harsh reaction conditions of the traditional Haber-Bosch process and the contradiction between thermodynamics and kinetics,researchers have been trying to explore sustainable and environmental-friendly ammonia synthesis technology. With the progress of catalytic science and surface science,people have a deeper understanding of the reaction mechanism of ammonia synthesis and the physicochemical properties of catalyst,which provides valuable reference information for the development of " green" ammonia synthesis process. For example,in order to improve the performance of transition metal catalytic ammonia synthesis,it is necessary to avoid the linear rela-tionship between surface species adsorption energy. In addition,the reaction rate and mechanism of light and electro-catalytic synthesis of ammonia using renewable energy as an energy source can be effectively affected by the help of external field effects. The development of chemical looping technology provides a new idea for ammonia synthesis process. The process of ammonia synthesis can be decoupled into two or more step-by-step reactions of nitrogen absorption and nitrogen desorption,which can better alleviate the contradiction between thermodynamics and kinetics of ammonia synthesis and avoid competitive adsorption of reactants. At the same time,each step-bystep reaction can be optimized respectively to achieve the best reaction effect of the whole chemical looping ammonia synthesis process. In the future,the cost and energy consumption of carbon-based chemical looping ammonia synthesis process can be reduced by using solar energy for energy gathering,biomass carbon as carbon source,and analyzing the economic feedback of the chemical looping ammonia process to guide the optimization of the process flow.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 15862K] - YE Hang;LIU Qi;PENG Bo;The Unconventional Petroleum Research Institute,Beijing Key Laboratory for Greenhouse Gas Storage and CO2-EOR,China University of Petroleum-Beijing;
CO_2 is one of the main greenhouse gases emitted by human production and living activities,which is recognized as the main cause of global climate change. CCUS technology is an important way to achieve deep emission reduction of CO_2 and mitigation of climate change. Among them,CO_2-EOR technology has broad prospects. As an ideal place for carbon storage,oil reservoirs can not only achieve long-term effective storage of CO_2,but also enhance oil recovery and achieve win-win of economic and social benefits. Determining the carbon sequestration potential of the target reservoir is of great significance for the large-scale implementation of CO_2-EOR technology. Nowadays,there are many methods to evaluate the storage potential of CO_2-EOR,but they can only be used for specific reservoirs and lack of standard universal methods. The mechanism of CO_2-EOR and sequestration was discussed,and the evaluation formula of CO_2-EOR storage potential proposed by domestic and foreign authoritative institutions was summarized in this paper. The universality of the method was demonstrated in detail through the analysis of examples,and the next step of accurately evaluating the carbon sequestration potential in the process of CO_2-EOR was prospected. During CO_2 flooding,oil recovery is enhanced by expanding oil volume,reducing crude oil viscosity,improving oil-water mobility ratio,extracting light components and miscible effect,while CO_2 storage depends on four mechanisms: structural trapping,residual trapping,solubility trapping and mineral trapping. The two concepts are different. At present,there are four authoritative and widely used evaluation methods of CO_2 storage potential: US-DOE,CSLF,USGS and RIPED & CUP method. Among them,US-DOE and USGS methods are estimation methods based on volume balance theory,which rely on storage efficiency and estimate the capacity of CO_2 storage through the combination of a variety of storage mechanisms. The CSLF method is based on the material balance theory,and the estimated results are consistent with the resource reserve pyramid,but the mechanism of solubility storage is not taken into account. RIPED & CUP method is actually an improved version of CSLF method,the dissolution of CO_2 in formation fluid is considered in this method,which makes the calculation formula more suitable for the reality of reservoirs in China,but it is difficult to determine the oil recovery in each stage. Therefore,in order to ensure the accuracy of the estimated results,the most appropriate evaluation method should be selected according to the geological characteristics of the reservoirs. Besides,for evaluating carbon sequestration potential more accurately,the next step should be carried out from the aspects of defining the reservoir development strategy,considering the lag effect,using field data for correction and strengthening safety risk assessment.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 2969K] - BAI Yu;LIANG Jie;WANG Liguo;CAO Yan;HE Peng;LI Huiquan;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;CAS Key Laboratory of Green Process and Engineering,Institute of Process Engineering,Chinese Academy of Sciences;School of Chemical Engineering,University of Chinese Academy of Sciences;Dalian National Laboratory for Clean Energy;
As a country rich in coal,a lot of CO_2 is produced by burning fossil fuels. CO_2 can be transformed into energy products,chemicals or polymer materials through chemical utilization,which is favorable for realizing its resource utilization. From the perspective of direct and indirect utilization of CO_2,the research progress of CO_2 resource utilization was reviewed.. In terms of direct utilization,the direct hydrogenation of CO_2 to methanol and ethanol was emphasized. l Meanwhile,the syntheses of organic carbonates,such as diethyl carbonate,as well as polymerization of CO_2 with epoxide to synthesize degradable polycarbonate were emphasized. In addition,in the aspect of indirect utilization,the research progress of synthesis of dimethyl carbonate from CO_2 via transesterification of ethylene carbonate and hydrogenation of ethylene carbonate to methanol and ethylene glycol was reviewed. Catalysts for direct methanol synthesis from CO_2 hydrogenation mainly include copper-based catalysts and noble metal catalysts. Because of the high cost of noble metals,inexpensive Cu-based catalysts have been studied extensively. The noble metal(Rh,Pd,Ru)-based catalyst system is widely used in the direct synthesis of ethanol from CO_2 hydrogenation,while,inexpensive,active and stable catalysts are needed to be further studied. Cerium-based heterogeneous catalyst is the most widely studied catalyst for the direct synthesis of diethyl carbonate from CO_2 and ethanol,but the yield of DEC is low due to the water produced in the product. No water is produced in the process of coupling reaction between epoxides and CO_2,which can effectively overcome the limitation of thermodynamics. Therefore,the coupling reaction of epoxide and CO_2 is an effective way to prepare DEC. Rare earth ternary catalyst system is mostly used in the copolymerization of CO_2 and epoxides to prepare polycarbonate materials. The conversion of epoxides and the selectivity of polycarbonate are relatively high,and the industrial applications have been realized. Basic catalysts and ion exchange resins with basic groups are used for the transesterification of CO_2 via ethylene carbonate with methanol to synthesize DMC.In addition,copper-based catalysts are the most studied in the hydrogenation of CO_2 via ethylene carbonate to methanol and ethylene glycol,. In summary,the chemical conversion and utilization of CO_2 is an important way for the comprehensive utilization of carbon and oxygen resources of CO_2,which will effectively support China's goal of carbon neutral in the future.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 8507K] - ZHAO Jiangting;XIONG Zhuo;ZHAO Yongchun;ZHANG Junying;State Key Laboratory of Coal Combustion,School of Energy and Power Engineering,Huazhong University of Science and Technology;
Photothermal catalysis is a promising strategy for CO_2 reduction,which can use the broad absorption of solar spectrum to stimulate the combination of thermochemical and photochemical processes,so as to promote the catalytic reaction and realize the efficient conversion of CO_2 under mild conditions. As a kind of photothermal catalysis,the introduction of heat energy into photocatalysis can improve the utilization of sunlight,promote the excitation and separation of carriers,and accelerate the diffusion of reaction molecules,and improve the reverse lift performance. In this paper,the concept and principle of photocatalytic CO_2 reduction were classified,and the research status of thermally assisted photocatalytic reduction of CO_2 was summarized. Based on the difference of reaction products,the selection of catalyst,reaction conditions and reaction mechanism of thermally assisted photocatalytic reaction were introduced. In addition,the key technology of local temperature measurement in photothermal reaction experiment was also introduced. Finally,the development of photocatalytic CO_2 reduction technology was prospected. The focus of future research should improve CO_2 conversion and product selectivity,and explore the reaction mechanism by using advanced in-situ characterization technology and theoretical calculation.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 4298K] - MA Shuangchen;WU Kai;LIU Chang;BIE Xuan;WANG Zhi;WANG Yufei;LI Jiayu;Hebei Key Lab of Power Plant Flue Gas Multi-Pollutants Control,Department of Environmental Science and Engineering,North China Electric Power University;
The current pressure and trend of CO_2 emission reduction were analyzed,and using electrocatalytic reduction as the technical core,combined with characteristics of coal-fired emissions,the selection of the electrochemical system was optimized,and the emission reduction strategies for coal-fired power plants under the background of carbon limitation was put forward. In order to alleviate the increasingly serious problems of CO_2 emission reduction and greenhouse effect,it is the inevitable choice for carbon capture and utilization to transform the large volume of discarded CO_2 into usable products. In this paper,the process principle of CO_2 catalytic reduction technology was briefly clarified,and the electrode,electrolyte,solubility of CO_2 and reactor form were discussed. Combined with the characteristics of electrochemical catalytic reduction technology and the structural characteristics of coal-fired power plants,the electrochemical catalytic reduction conditions of large volume and low concentration CO_2 were filtered,the basic electrochemical system with Cu based gas diffusion electrode-ionic liquid-continuous reactor as the core was determined. Furthermore,the countermeasures for the electrochemical catalytic reduction of CO_2 in the flue gas of coal-fired power plants were proposed. However,in the process of transforming the technology into practical application,the technology still faces obstacles,such as the influence of impurities in non-ideal gas source,slow product generation rate caused by low reduction current density,short electrode life,and difficult separation and purification associated with product diversity,which points out the research direction for the development of application-oriented technology.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 9229K] - WU Xiaofeng;FAN Weidong;School of Mechanical and Power Engineering,Shanghai Jiao Tong University;
In oxy-fuel combustion,flue gas is mainly composed of CO_2 and H_2O because the recycled flue gas is used as diluent instead of N_2 in the air. CO_2 and H_2O have an intensive radiation ability as non-polar triatomic molecule while N_2 has no radiation ability,which leads to the change of gas radiation characteristics in oxy-fuel combustion. In the numerical simulation,gas radiation model is an important sub model. Several modified gas radiation models have been proposed for applying to oxy-fuel combustion,but the effect of different gas radiation model on the numerical simulation of oxy-fuel combustion in different conditions has not been unified. In order to research the effect of gas radiation model on the simulation results of combustion heat transfer in different sizes of furnace with gas or coal combustion,one new gas radiation model considering the effect of CO and other six typical models in the literatures were coupled into the numerical simulation by user defined function programming. The results show that: in the oxy-gas combustion,the flame structure is affected by gas radiation models. Meanwhile,the combustion temperature distribution changes and the difference between the results of different models can reach 500 K. Radiation heat transfer between gas and wall is also controlled by gas radiation models. The effect of gas radiation models on flame zone is rather large while it is ignored in the non-flame zone. In the oxy-coal combustion,when the effective radiation layer thickness is around 0.3 m such as in a 100 kW_(th) down-fired furnace,gas radiation models almost have no effect on the coal combustion numerical simulation results. This may be because particle radiation plays a dominant role in the radiation heat transfer calculation.When the path length is around 16 m such as in a 1 000 MW tower type boiler,gas radiation models have a large effect on the combustion temperature and species concentration. The temperature difference can reach 100 K. However,the gas radiation model has no effect on the simulation results in the non-flame zone in middle of furnace.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 23729K] - CHENG Sizhe;ZOU Chun;YAO Qing;LOU Chun;WANG Shusen;JING Huixiang;MEI Mei;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;Key Laboratory of Healthy &Intelligent Kitchen System Integration of Zhejiang Province;Ningbo Fotile Kitchen Ware Company;
The oxy-fuel combustion of biomass technology combines the advantages of oxy-fuel combustion and biomass combustion,which can not only reduce the consumption of fossil fuels,but also easily achieve CO_2 capture. The most significant feature of oxy-fuel combustion is that the oxygen concentration in the atmosphere is more than 21%,which has a significant effect on the ignition behavior of biomass. Cellulose,hemicellulose,and lignin are the three main components of biomass. Therefore,studying the ignition and combustion behavior of these three components under oxy-fuel conditions is the basis for the study of biomass ignition and combustion. In this work,a drop tube furnace combined with a high-speed camera were utilized to study the ignition behaviors of cellulose,hemicellulose,and lignin particles of 74-154 μm at the temperature of 1 273 K under O_2/CO_2 atmosphere with oxygen concentration of 21%,30%,50%,70%,and100%. The radiant energy analysis technology was used to calculate the temperature of particles in the ignition picture. The results show that cellulose and hemicellulose change from hetero-homogeneous ignition to homogeneous ignition and lignin changes from homogeneous ignition to heterogeneous ignition with the increase of O_2 concentration. The ignition mechanisms of cellulose,hemicellulose,and lignin change at 30%,70%,and 50% oxygen concentration,respectively. The ignition of cellulose is sensitive to the change of O_2 concentration. When the _2 concentration exceeds 30%,the cellulose char ignites firstly. The heating rates of hemicellulose and lignin increase with the increase of O_2 concentration. For hemicellulose,it can be attributed to that the burning proportion of hemicellulose volatiles decreases and the burning proportion of hemicellulose char increases with the increase of O_2 concentration during the combustion process. For lignin,it is because the combustion of lignin char is enhanced with the increase of oxygen volume fraction. Moreover,the combustion time of hemicellulose and lignin decreases with the increase of O_2 concentration,both of which are due to the enhancement of their char combustion with the increase of oxygen content. Furthermore,the lignin char will melt and expand under higher oxygen concentration,forming an obvious expanding flame.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 11221K] - XING Chenjian;WANG Ruilin;ZHAO Chuanwen;School of Energy and Mechanical Engineering,Nanjing Normal University;
In order to deal with the problem of global warming,it is imperative to transform the carbon capture of existing coal-fired power plants and vigorously develop clean energy. Chemical absorption method is the most mature in carbon capture technology,but its high energy consumption seriously affects the power generation efficiency of coal-fired power stations. Therefore,some scholars have proposed the use of clean energy-assisted carbon capture,in which photo-thermal-assisted carbon capture is the most widely used,but this use method does not play the potential of single photo-thermal utilization. By using a large amount of low-grade waste heat generated in the process of concentrating photovoltaic power generation to assist carbon capture,the efficiency of the photovoltaic system can be improved while the low-grade waste heat is effectively used. Based on this research,a new system of concentrating photovoltaics-photovoltaic waste heat directly assisted carbon capture was conceived,and an energy conversion model of concentrating gallium arsenide-waste heat assisted amine decarbonization was established to verify the potential of concentrated photovoltaic waste heat directly assisted amine decarbonization in quality and quantity. According to the sensitivity analysis of heat consumption,the key parameters of the amine decarburization system were optimized. The minimum heat consumption could reach 3.7 GJ/t. The influence of battery working temperature and radiation intensity on the carbon capture performance and photoelectric efficiency of the system was analyzed,and the optimal working temperature of the battery was determined as 140 ℃ . By integrating the new system into a typical 600 MW coal-fired power station and comparing it with the reference system,it can be obtained that compared with a single coal-fired carbon capture,the power generation efficiency of the power station is increased by 6.01%,and the photovoltaic power generation is increased by 185.2 MW; compared with a single photovoltaic,the photovoltaic power generation is reduced by 15.79 MW,but the waste heat accounting for 60% of the received solar energy is effectively used,which can achieve 461. 75 t/h CO_2 capture. The average daily photovoltaic power generation of the new system on a typical day is 61.8 MW,and the average daily carbon capture capacity is 155.6 t/h. In order to achieve an annual carbon capture guarantee rate of more than 80%,the Concentrating photovoltaic area above about 4 km~2 is required. The new system uses photovoltaic waste heat instead of the original low-pressure cylinder extraction steam from the power station,eliminating the energy penalty of carbon capture on the power station,while converting high-grade solar energy into electricity,and using photvoltaic waste heat in a grade-matched manner. The system finally realizes the efficient use of solar energy and the parallel clean use of fossil energy.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 7894K] - SUN Feng;SHEN Cheng;LUO Cong;LUO Tong;China Ship Development and Design Center;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;
The carbonation conversion of the calcium-based sorbent decreases significantly after multiple CO_2 capture cycles,whether the sorbent can be further used efficiently in desulfurization reaction is important issue which deserves concerns. In order to delve into this issue,the high performance calcium-based sorbent and natural limestone sorbent were selected,the carbonation and sulfation reaction performance after multiple CO_2 capture cycles were analyzed and compared by thermal gravimetric analyzer,and the sulfation kinetics characteristics were studied by particle model. The results showed that the rate of carbonation reaction and CO_2 adsorption capacity of the high performance calcium-based sorbents are much higher than those of limestone adsorbent. After multiple cycles of CO_2 capture test,the CO_2 adsorption capacity of high performance calcium-based sorbents is over 10 times higher than that of limestone,and its SO_2 adsorption capacities was improved by 40% than that of limestone. After multiple CO_2 capture reactions,their sulfation abilities are both improved. The improvement of limestone is greater,the sulfation conversion is increased from 26% to 35%,while the sulfation conversion of high performance calcium-based sorbent is increased from 38% to 43%. It is found through particle model calculation that the sulfation process of both sorbents is a first-order reaction related to the concentration of SO_2. After the multiple CO_2 capture cycles,the activation energy of sulfation reaction of limestone decreases by nearly 30%,while that of high performance calcium-based sorbent only decreases by 5%. The results indicate that the desulphurization capacity of two different calcium-based sorbents can be improved to different degrees after multiple CO_2 capture cycles,and both of them can be better used for SO_2 removal.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 7997K] - SUN Haojia;TONG Haichuan;WANG Chang'an;WANG Chaowei;TANG Guantao;CHE Defu;State Key Laboratory of Multiphase Flow in Power Engineering,Xi'an Jiaotong University;Black Dragon New Double Stock Co.,Ltd.;
In China' s current energy structure,the proportion of fossil energy,especially coal resources,is relatively high,which causes great environmental pressure. As a solid waste with rapidly increasing yield in recent years,antibiotic filter residue is also a kind of biomass fuel resource,but research on the energy utilization of residue is insufficient at present. In this paper,CH_4 and other gases were used to simulate the combustible components of the residue,and the PFR reactor in Chemkin software was used to construct the model of oxygen staged combustion and unstaged combustion of residue in O_2/CO_2 atmosphere. NO_x production characteristics under the two conditions were simulated to study the influences of various factors in oxygen staged combustion and unstaged combustion,and the reaction mechanism of the results were analyzed by production rate analysis and sensitivity analysis. The results show that under the oxygen unstaged combustion,the conversion rate of NO_x first increases and then decreases with the increase of combustion temperature,reaching the peak at about 1 500 ℃; the conversion rate of NO_x increases with the increase of excess air coefficient,and increases significantly when the excess oxygen coefficient increases from 0.9 to 1.1. Under the oxygen staged combustion,the combustion temperature of primary combustion area has a complicated effect on the conversion rate of NO_x; the conversion rate of NO_x first decreases and then increases with the increase of rate of overfire air; the conversion rate of NO_x decreases as the position of over fire air is pushed back. Under the oxygen staged combustion,the reducing atmosphere promotes the transformation of N in NO_x to other components,which can significantly reduce the NO_x production. The NO_x conversion rate is the lowest when the combustion temperature is lower than 1 500 ℃ and the rate of overfire air is about 0.35. In this paper,the reaction kinetics simulation study of the combustion of antibiotic filter residue in O_2/CO_2 atmosphere is carried out for the first time,and the influences of various factors is explored,which has a guiding significance for the energy utilization of residue.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 17172K] - LEI Yu;NIU Yanqing;WANG Hengtong;WEN Liping;WANG Guangyao;HUI Shien;State Key Laboratory of Multiphase Flow in Power Engineering,School of Energy and Power Engineering,Xi'an Jiaotong University;
To extend the oxygen enriched combustion technology in a large scale,it is necessary to study the emission characteristics of particulate matter in oxy-fuel combustion of pulverized coal. In this paper,the effect of H_2O(g) volume fraction(0,5%,10%,20%,30%) on the formation of ultrafine particulate matter(PM) under oxy-fuel combustion atmosphere was studied in a 1800 K drop tube furnace(DTF). Furthermore,the mass-based and number-based particle size distribution(PSD) were obtained and analyzed by a 14-stage electrical low pressure impactor(ELPI+). The results indicate that the mass-based and number-based PSD of ultrafine PMs remains almost unchanged in various H_2O(g) contents(0,5%,10%,20%,30%),while the peak of ultrafine particles fluctuates. The total number of ultrafine PM is determined by the number of ultrafine PM with the smallest particle size. The number fractions of the ultrafine PMs collected by the first impactor of ELPI + are all higher than 65% under all H_2O(g) contents. The total mass of ultrafine PM is determined by the mass of ultrafine with the largest particle size and the mass fractions of the ultrafine PMs collected by the seventh impactor of ELPI+are all higher than 94%. Low concentration of H_2O(g) can inhibit the formation of ultrafine particles,and the inhibition effect is the most significant when the volume fraction of H_2O(g) is 5%; high concentration of H_2O(g) can promote the formation of ultrafine particles. Because the gasification reaction of H_2O(g) with coal char produces a reducing atmosphere around the coal char particles,which promotes the reduction of minerals to elemental matter and further promotes the evaporation of minerals. On the other hand,the gasification reaction is endothermic reaction,which will reduce the combustion temperature of coal char particles. At the same time,the addition of H_2O(g) also leads to the increase of heat capacity of flue gas. The combustion temperature of coal char inhibits the evaporation of minerals in coal,resulting in the reduction of ultrafine particles,which is the result of the competition between the two kinds of interaction. In addition,the addition of H_2O(g) makes the average particle size of ultrafine particles increase,and the average particle size of ultrafine particles increases the most rapidly when 0-5% H_2O(g) is added.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 11575K] - XU Mingxin;WU Yachang;WANG Hanxiao;OUYANG Haodong;LU Qiang;National Engineering Laboratory for Biomass Power Generation Equipment,North China Electric Power University;
Oxy-fuel combustion is one of the most potential CO_2 capture and storage technologies for large-scale promotion and commercial application,and the flue gas compression purification and CO_2 purification is the core unit in the whole oxy-fuel combustion system. However,the current studies focused on the process verification of flue gas compression purification after oxygen enriched combustion,and the operating characteristics of flue gas compression unit,especially the migration and transformation of impurities in the process of flue gas compression and its relationship between the operating parameters and the removal efficiencies of impurities,were still unclear. Besides,little attentions have been paid to the purification and production of CO_2 liquid with high purities,which can significantly affect the economic efficiency of the whole oxy-fuel combustion system. Therefore,in order to meet the needs of oxygen enriched combustion flue gas purification and CO_2 purification,the fundamental operating characteristics of the SO_2 and NO_x absorption removal as well as the purification of CO_2 in the compression and purification process of oxy-fuel combustion were systematically studied in the present work,in which the removal of SO_2/NO_x were achieved by pressurized acid adsorption and the purification of CO_2 was achieved by cryogenic distillation.The results indicate that the removal of SO_2 and NO by flue gas purification can reach 100% and 99% respectively. Meanwhile,the purity of food grade liquid CO_2 can reach 99.99%. In the process of flue gas cleaning,the gaseous reaction is dominant,and the residence time for the adsorption of both SO_2 and NO can be shortened by the increase of reaction pressures. As the operating pressures of the SO_2 adsorption column increase to more than 0.8 MPa,the removal efficiency of SO_2 can be 100%,and when the operating pressure of NO adsorption column is more than 3.0 MPa,the emission of NO can meet the demands for the state ultra-low emission. The purity of liquid CO_2 decreases with the increase of operating pressure in the column of CO_2 purification. Furthermore,the energy consumption of CO_2 recovery can be as low as 0.37 MJ/kg CO_2,when the operating pressures for SO_2 removal,NO_x removal,and CO_2 purification are 1.6 MPa,3.0 MPa,and 3.8 MPa.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 8476K] - WANG Jiuzhan;WEI Zehua;JING Jieying;LI Wenying;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;Key Laboratory of Coal Science and Technology,Ministry of Education,Taiyuan University of Technology;
Fe-based oxygen carrier is regarded as a promising industrial oxygen carrier,but there are some problems of low oxygen utilization rate and easy sintering at high temperatures.Although the performance of Fe-based oxygen carriers can be improved by preparing bimetallic composite oxygen carriers or adding inert components,there are certain defects.If the active components and inert materials can be integrated into a crystal structure to prepare oxygen carrier with spinel structure,the synergistic effect of bimetal can be used to improve the activity performance of oxygen carrier while Al~(3+) is employed to improve the stability of oxygen carrier.The NiFeAlO_4 oxygen carrier with spinel structure were synthesized via co-precipitation method and sol-gel method.The effects of preparation method and mass ratio(oxygen carrier to coal) on the coal chemical looping combustion reaction and cycling stability of the NiFeAlO_4 oxygen carrier were experimentally investigated.The function of oxygen carrier in coal conversion was also studied.The results show that NiFeAlO_4 oxygen carrier synthesized by sol-gel method possesses superior reactivity.When the mass ratio between oxygen carrier and coal was 20∶1,the carbon conversion is 86.7%,which is higher than that of coal pyrolysis(34%),and the CO_2 relative concentration is 93.6%.The analysis of the crystal structure and morphology of NiFeAlO_4 oxygen carrier before and after the reaction shows that the Ni O detected after 10th redox cycle and the grain agglomeration are the main reason for the decrease of its cyclic stability.Compared to its heating supply function,NiFeAlO_4 oxygen carrier mainly plays the role of oxygen supply in coal chemical looping combustion,which not only promotes the conversion of volatile matter to coal gas,but also has solid-solid reaction between NiFeAlO_4 oxygen carrier and coke,and is conducive to the generation of more CO_2.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 12492K] - YAN Yongliang;ZHA Jianrui;DUAN Lunbo;CLOUGH Peter;School of Water,Energy and Environment,Cranfield University;Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education,Southeast University;
Developing high-performance and low-cost oxygen carrying materials is the key to the future commercial application of chemical-looping processes. Over 1 000 materials have been tested as the oxygen carriers for chemical-looping processes. Among them,ores and industrial by-products as oxygen carriers have recently attracted much attention recently due to their low cost and availability,especially the sufficient reactivity with the solid fuels. However,these materials have highly variable compositions,which strongly influences the performance in chemical-looping. It costs a lot to test one by one. Taking natural manganese ore as the object,and taking the existing experimental data as the training set,the new machine learning algorithm was used to predict the performance of manganese bearing minerals in chemical chain reaction,and compare the performance of support vector machine and artificial neural network in the prediction process.The results show that the two algorithms have good accuracy for the data in the training set,but there are differences in the accuracy and robustness of the new input value prediction. Support vector machine can avoid the over fitting phenomenon of neural network in small sample training set. The sensitivity analysis shows that the change of manganese content in oxygen carrier has a great influence on the reaction characteristics,while the effect of specific surface area is small.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 3713K] - KONG Runjuan;LI Wei;REN Qiangqiang;LIU Zhicheng;Institute of Engineering Thermophysics,Chinese Academy of Science;University of Chinese Academy of Science;
Carbon dioxide capture,utilization and storage(CCUS) is an effective technology to reduce greenhouse gas emissions and achieve sustainable development of the global environment. Pressurized oxy-fuel combustion technology is a low-cost CCUS technology.Circulating fluidized bed combustion technology( CFB) is one of the most commercialized clean coal combustion technologies. The pressurized CFB oxy-fuel combustion combines many advantages of pressurized oxy-fuel combustion and CFB combustion,which has a strong industrial application prospect. However,the complex structure,the switching of combustion conditions and the flue gas recirculation lead to the great challenges in the start-up,control and operation of the pressurized CFB oxy-fuel combustion system. At present,most of the researches on pressurized CFB oxy-fuel combustion are in the stage of theoretical modeling,mechanism research and bench-scale test. In order to further explore the start-up and operation methods of pressurized CFB oxy-fuel combustion,the pilot-scale experiment was carried out in a pilot test platform of MW pressurized CFB oxy-fuel combustion by Institute of Engineering Thermophysics,Chinese Academy of Sciences. The stable operation of pressurized oxy-fuel combustion was realized,and a pilot-scale pressurized oxy-fuel combustion operation mode and the variation curves of temperature,pressure,coal feed rate and air volume during start-up and operation were obtained.During the pressurized oxy-fuel combustion,the overall oxygen volume fraction reaches 29%,the operation pressure is 0. 30 MPa,the power is 0.84 MW,and the CO_2 volume fraction of the tail gas reaches 91%,which is benefit to the capture and compression purification of CO_2 product. The main process of the pilot-scale pressurized oxy-fuel combustion operation mode is as follows: start-up stage-atmospheric O_2/N_2 combustion stage-atmospheric oxy-fuel combustion-pressurized oxy-fuel combustion stage,and each stage switches stably.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 4516K] - ZHAO Ziqi;ZHANG Zhongxiao;JIANG Yanchi;JIA Mengchuan;MU Aiwei;School of Energy and Power Engineering,University of Shanghai for Science and Technology;School of Mechanical and Power Engineering,Shanghai Jiao Tong University;
In order to explore the influence of nanoparticles on the absorption of CO_2 by TETA solution and the promotion effect of dispersants on the absorption of CO_2 by nanofluids,two-step method was used to prepare nanofluids with different oscillation time,different TETA concentration,different particle size,different solid content and type of nanoparticles and dispersant.The TETA solution bubbling experiment platform was built to absorb CO_2. The absorption of CO_2 by nanofluids prepared under different working conditions was tested and compared with the blank solution.The experimental results show that,the enhancement coefficient of the removal rate of the nanofluids appears to increase first and then decrease with the increase of the mass fraction of the nanoparticles. The larger nanoparticles have better mass transfer performance,and the larger size can reduce the relative surface area and energy,the surface and quantum scale effects of nanoparticles are weakened.The CO_2 absorption rate increases with the increase of ultrasonic crushing time in the initial stage.However,the absorption rate slows down when the ultrasonic crushing time exceeds 1.0 h.During the experiment of TETA concentration and solid content of nanoparticles,the enhancement coefficient of removal rate increases first and then decreases with the increase of concentration and solid content.To sum up,1.0 mol/L TETA added with 60 nm TiO_2 with 0.1 wt.% has the most obvious promotion effect on CO_2 after 1.0 h ultrasonic shock.The removal rate enhancement coefficient can be up to 1.9. When dispersants of C-Na,SDBS and X-100 are added into TiO_2-TETA-H_2O nanofluids,the surface of TiO_2 particles is positively charged,so the influence of dispersants on the stability of TiO_2-TETA-H_2O nanofluids is generally as follows: anionic > non-ionic > cationic.When the mass fraction of anionic dispersant C-Na is 0.1%,the stability of cationic nanofluid TiO_2-TETA-H_2O is the best based on the theory of double electron layer.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 6315K] - SUN Yifu;LI Fengjun;HE Wen;WANG Tao;GAO Li;LI Yan;GAO Jun;ZHAO Rui;FANG Mengxiang;College of Energy Engineering,Zhejiang University;Shaanxi Guohua Jinjie Energy Co.,Ltd.;Shenhua Guohua( Beijing) Electric Power Research Institute Co.,Ltd.;
CO_2 mineralization curing concrete technology makes concrete rapid forming and improve mechanical properties in a short time,greatly shorten the curing cycle,improve production efficiency,is a large-scale industrial application prospect of carbon dioxide utilization. In this paper,the CO_2 curing of aerated concrete based on industrial solid waste raw materials was mainly studied,and the effects of raw material ratio,curing pressure and curing method on the CO_2 mineralization reaction were mainly studied. The formula of carbon dioxide curing aerated concrete is mainly determined by the compressive strength and carbon fixation performance of the specimen. The change characteristics of the reaction products under different curing conditions were characterized by SEM and XRD,and the pore distribution before and after CO_2 curing was measured by mercury intrusion method. The results show that the carbon fixation ratio of the specimens increases with the increase of the curing pressure when the aerated concrete after natural curing for 4 days is cured for 2 hours. Low pressure curing and stepped curing are beneficial to reduce the mechanical strength loss of the specimens. The higher the CO_2 concentration/partial pressure of the second stage of cascade curing is,the higher the apparent carbon fixation rate of the specimens is; Under the same CO_2 curing condition,SEM observes that the products of mineralization reaction has different morphology,such as spherical and spindle shape,XRD analysis shows that there are three different crystal forms of calcium carbonate; after CO_2 curing,the micropores with pore diameter in the range of 0.01-0.10 μm decrease significantly,and the higher the apparent carbon fixation ratio is,the more significant the filling effect on the aerated concrete is.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 14144K] - ZHANG Chunxiao;LI Yingjie;School of Energy and Power Engineering,Shandong University;
The desulfurization and denitrification systems face sever challenges due to the ultra-low emission rules of coal-fired boilers.CaO-based sorbents can effectively remove SO_2 from flue gas of circulating fluidized bed boilers. Char can be used as a reducing agent to reduce NO directly,and CaO plays a catalytic role in the reduction reaction of NO by char. which can realize the simultaneous SO_2 and NO removal in flue gas. Based on calcium looping technology for CO_2 capture,the simultaneous SO_2/NO removal performance of CaO/bio-char was investigated under fluidization at constant heating rate in this study to explain the effect of continuous temperature change on the simultaneous SO_2 and NO removal by CaO/bio-char. The influences of O_2 and CO_2 in flue gas on the simultaneous SO_2/NO removal performance of CaO/coconut shell char were discussed. The results indicate that O_2 can reduce the temperature of heterogeneous reduction of NO by activating carbon atoms on the surface of coconut shell char. The NO removal efficiency increases gradually with constant rate heating from 300 ℃ to 950 ℃,reaching 100% at above 780 ℃ . The SO_2 removal efficiency of CaO/coconut shell char is also promoted by O_2. The simultaneous SO_2/NO removal is inhibited by the carbonation reaction between CaO and CO_2 as well as CO_2 gasification of coconut shell char. In the presence of both O_2 and CO_2,the NO removal efficiency increases as temperature increases from 500 ℃ to 800 ℃,while the SO_2 removal efficiency firstly decreases and then increases. SO_2 inhibits the NO removal of CaO/coconut shell char,while NO can promote the SO_2 removal performance. The simultaneous SO_2 and NO removal efficiencies of CaO/coconut shell char at 800 ℃ are 97.7% and94%,respectively.
2021 02 v.27;No.132 [Abstract][OnlineView][HTML全文][Download 7095K] 下载本期数据