2022年08期目次

  • Research progress on controllable preparation of coal based graphene series materials and its application in CO2 reduction process

    ZHANG Yating;YAN Xin′e;LIU Guoyang;LI Keke;JIA Jia;College of Chemistry and Chemical Engineering,Xi′an University of Science and Technology;School of Civil Engineering,Xi′an Traffic Engineering Institute;

    As a two-dimensional carbon material with unique structure and properties, graphene shows a good application prospect in the process of CO_2 reduction and conversion. Searching for abundant carbonaceous precursors and controllable preparation methods of graphene is the basis for its large-scale application. As a promising mineral resource with rich carbon, coal contains abundant functional groups and high aromatic nano graphite microcrystalline structure. Using coal and its derivatives as carbon sources to prepare high value-added graphene materials has unique advantages, which is an important way to realize the clean utilization of coal and the low-cost practical application of graphene. Based on the chemical composition and structure of different rank coals, researchers have successfully achieved the controllable preparation of a series of multi-scale and multi-form coal-based graphene materials through appropriate molecular tailoring and chemical structure assembly. Common preparation strategies include: mechanical cleavage and exfoliation, chemical intercalation oxidation, electrochemical exfoliation, chemical vapor deposition, anodic arc discharge and liquid-phase self-assembly, etc. For example, zero dimensional graphene quantum dots are prepared by chemical oxidation or ultrasonic physical tailoring of coal macromolecular structure. Two dimensional graphene films are prepared by chemical vapor deposition(CVD) of carbon containing hydrocarbon small molecule gas obtained from coal pyrolysis. Two-dimensional graphene nanosheets are obtained by physical or chemical exfoliation after graphitization of coal at high temperature. Three dimensional graphene aeroneneneba gels are prepared by structural self-assembly of two-dimensional graphene. Because the composition and surface structure of coal-based graphene are easy to regulate and modify, the coal-based graphene shows good catalytic activity in the process of CO_2 reduction. By summarizing the latest research of coal-based graphene series materials in the process of CO_2 reduction using photocatalysis, electrocatalysis and photoelectrocatalysis, it is considered that coal-based graphene can effectively improve the efficiency and selectivity of CO_2 reduction process by increasing the reaction active sites and changing the surface structure of the catalyst. Finally, the control of the composition and structure of coal-based graphene and the structural design of CO_2 reduction catalyst were prospected.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 24447K]

  • Optimization of baffle structure of proton exchange membrane fuel cell

    SU Dandan;SUN Feng;ZHANG Zhiguo;YIN Yujie;PANG Bin;DONG Xiaoping;School of Quality and Technical Supervision,Hebei University;Hebei Technology Innovation Center for Lightweight of New Energy Vehicle Power System;CATARC (Tianjin) Automotive Engineering Research Institute Co.,Ltd.;

    The optimization of the flow channel structure of proton exchange membrane fuel cell(PEMFC) can improve the mass transfer efficiency of reaction gas and increase the current density, which is an effective method to improve the output performance of PEMFC. First, the geometric model of a single straight channel of PEMFC was established, and the influences of baffle inclinations on the transmission characteristics of reaction gas were studied by adding trapezoidal baffle in the flow channel. The results show that adding baffles in the flow channel can significantly increase the flow rate of reaction gas in the flow channel and promote the mass transmission of reaction gas from the flow channel to the diffusion layer. Increasing the front and rear of inclination angle of the symmetrical and asymmetric trapezoidal baffle can effectively increase the O_2 mass fraction under the baffles, improve the flux of reaction gas in the gas diffusion layer, and strengthen the mass transfer of reactive gases. Compared with the symmetric trapezoidal baffle, the asymmetric trapezoidal baffle with 75° front and 60° back or 60° front and 75° back angles has a better effect on enhancing the mass transfer of the reactant gas. The O_2 concentration in the diffusion layer and catalytic layer of PEMFC increases significantly with the increase of the number of baffles, and the peak of reaction gas mole fraction appears in the corresponding area of the baffles. The output performance of PEMFC increases with the number of baffles in the flow channel. The peak power density of PEMFC is 0.435 W/cm~2 when 11 asymmetric trapezoidal baffles with 60° front and 75° back inclination are added to the flow channel, which is 6.6% higher than that without baffles. In addition, when the working voltage U=0.1 V, the current density of the flow channel without baffle is 1.57 A/cm~2, and when the number of baffles in the flow channel is 11, the current density is 1.80 A/cm~2, which increases by about 14.6 %. The research results provide a theoretical basis and technical reserve for the subsequent PEMFC flow field optimization.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 26222K]

  • Review on combustion and emission characteristics of coal-fired utility boilers ammonia/coal co-firing

    WANG Xin;CHEN Jun;FAN Weidong;School of Mechanical and Power Engineering,Shanghai Jiao Tong University;

    In recent years, as a carbon-free, hydrogen-rich fuel, ammonia is mostly used as a carbon-free fuel for internal combustion engines, gas turbines and other industrial applications. Ammonia/coal co-firing has also attracted a lot of attention in order to reduce CO_2 emissions from coal-fired power stations. The methods for reducing carbon emissions from existing coal-fired power plant boilers were introduced, and the latest progress in ammonia/coal co-firing research was briefly described, and the potential problems in the ammonia/coal co-firing combustion process were analyzed, and the combustion characteristics and pollutant emission rules of ammonia/coal co-firing were revealed. In view of the combustion characteristics of ammonia in coal-fired boilers and the high NO_x emission characteristics in the process of ammonia/coal co-firing, a test with 0-100% ammonia co-firing ratio was realized in a combustion furnace, and air-staged combustion technology was applied to ammonia/coal co-firing. The influence of different ammonia co-firing ratios and air-staged techniques(combustion ambient temperature, ammonia addition position) on ammonia/coal co-firing combustion products was examined further. The coal-fired boiler′s strong preheating conditions and high combustion ambient temperature in the furnace promote increase ammonia combustion. As a result, ammonia′s weak combustion properties will not be a significant barrier to ammonia/coal co-firing in coal-fired boilers. NO_x emission concentration can be greatly reduced by adjusting the co-firing approach and modifying the air-staged combustion strategies. The length of the reduction zone can be extended by delaying the addition position of the burnout air, which is conductive to the selective non-catalytic reduction reaction between NH_3 and NO in the reduction zone and the heterogeneous and homogeneous reduction reaction between coal pyrolysis products(volatile and char) and NO, effectively reducing NO_x emissions. With a medium and high burnout air addition position and a burnout air ratio of 30% or more of the total air volume, the NO_x emission concentration may be regulated at a level comparable to that of coal air-staged combustion if the ammonia co-firing ratio is managed at 20%-30%(calorific value). The peak concentration of H_2S in the reduction zone of ammonia/coal co-firing lowers with increasing ammonia co-firing ratio under air-staged combustion circumstances, which may have a moderating trend on the corrosion of water-cooled wall pipes. Ammonia/coal co-firing will also considerably increase the gasification reaction of CO_2/H_2O and coal char in the reduction zone under air-staged combustion circumstances, resulting in the creation of huge volumes of CO. The utilization of ammonia/coal co-firing technology is a very potential technological advancement path toward achieving low carbon and low nitrogen emissions in coal-fired power plants.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 17167K]

  • Review on raw meal and fuel substitution technology for low carbon cement under carbon neutrality

    LI Pengpeng;REN Qiangqiang;LYU Qinggang;CHEN Rui;School of Energy Power and Mechanical Engineering,North China Electric Power University;Institute of Engineering Thermophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;

    Under the background of carbon peak and carbon neutrality, cement and other building materials industry, as an industry with high energy consumption, high emissions, and overcapacity, face a great challenge. Starting from the existing CO_2 emission reduction technologies in the cement industry, the principle and current situation of low-carbon cement production mode were analyzed, and the current situation of raw meal substitution, fuel substitution and clinker substitution technology were summarized. Finally, combined with the domestic current situation and development plan, the low-carbon technology of the cement industry was prospected. The existing carbon dioxide emission reduction technologies in the cement industry include: the raw meal substitution technology that substitutes low-carbon raw meal or industrial wastes for a component in raw meal, the fuel substitution technology that applies low-carbon clean fuels to cement production and adds materials with partial cementation properties to concrete to reduce the use of clinker, the technologies to improve energy efficiency when using electricity and fuel, as well as promising but not yet large-scale application of carbon capture and carbon storage technology. The raw meal component substitution method is the most effective low-carbon production method. Portland cement raw meal contain a large amount of limestone, which will decompose and produce CaO and a large amount of CO_2 necessary for clinker firing in the process of cement production. Using calcium rich waste to replace limestone and other high carbon loaded raw meal can significantly reduce CO_2 emissions and provide the same amount of CaO. The raw meal to be replaced include calcium carbide slag, calcium silicate slag, steel slag, quartz sludge, papermaking sludge, etc. Different industrial wastes can not only replace limestone raw meal for cement production, but also provide additional benefits. For example, providing calcium silicate slag can provide silicon raw meal, and the application of steel slag may improve the burnability of raw meal. The fuel substitution method can serve multiple purposes, using agricultural and forestry wastes to provide heat for cement production can reduce carbon emissions. Substituting domestic waste or municipal sludge with high calorific value for coal for production can also be used for disposal of waste, the fuel preheating technology, which replaces the directly input fuel after preheating, has been proved to be an effective method to achieve low emissions and improve energy efficiency. Clinker substitution can effectively reduce carbon emissions. Adding slag, fly ash, pozzolan, limestone, burnt clay to concrete can replace clinker by using its own cementitious activity, which is conducive to CO_2 emission reduction, but China′s cement clinker coefficient is low. It is recommended that the domestic cement clinker coefficient be appropriately increased. The current technical determines that clinker replacement is still widely used, and the replacement rate of fuel and raw meal is expected to gradually increase. The medium-term goal is to maximize the application capacity of alternative fuels and alternative raw meal technologies. CCS technology is more mature, and backward production capacity is completely eliminated. The long-term goal is that cement enterprises can formulate reasonable, effective and economic emission reduction plans according to policies and production requirements, and the cement industry can achieve carbon neutrality.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 1151K]

  • Effect of combustion temperature on pressurized combustion and C/N transformation characteristics of Shenhua bituminous coal

    ZHANG Yu;DU Shangbin;ZHANG Wenda;ZHAO Yijun;SUN Shaozeng;School of Energy Science and Engineering,Harbin Institute of Technology;

    Pressurized O_2/CO_2 combustion technology is a new combustion technology that can achieve efficient CO_2 capture. In order to explore the combustion and pollutant emissions characteristics of pulverized coal in a pressurized O_2/CO_2 atmosphere, the pressurized combustion(residence time is 0.3 s) and N transformation characteristics of Shenhua bituminous coal were investigated by a pressurized drop tube furnace(PDTF) experimental system at a pressure of 0.9 MPa. Effect of combustion temperature(1 073-1 273 K) on the formation rules of gaseous products(CO, N_2O and NO) in the O_2/CO_2 combustion process was analyzed by online measurement, and effect of combustion temperature on the physical and chemical structure of combustion residues was analyzed by off-line characterization. In the pressurized combustion process of pulverized coal, the increase of combustion temperature causes the conversion rate of fuel nitrogen to NO_x in coal to increase first and then decrease. In the combustion temperature range of 1 073-1 273 K, compared with N_2O, the increase of combustion temperature has less effect on NO release, and the conversion of fuel nitrogen in coal to gas-phase NO_x is mainly determined by the generation of N_2O. In the process of coal pressurized O_2/CO_2 combustion, the concentrations of CO and NO gradually decrease and increase with combustion temperature, while the release of N_2O increases first and then decreases with combustion temperature. At 1 273 K, the emission concentrations of CO, NO and N_2O reach 363.5×10~(-6), 10.2×10~(-6) and 6.8×10~(-6), respectively. The FTIR results show that the oxygen-containing groups of the ■ structure on the surface of pulverized coal particles have higher combustion reactivity than C—OH structure. As the combustion temperature increases from 1 073 K to 1 273 K, the relative content of C—O dose not change much, and the relative contents of ■ decrease by 1%, 1% and 7%, respectively, while the relative content of ■ increases by 7%. It shows that the increasing pressurized combustion temperature can promote the rapid consumption of the C—H structure, and increase the aromatization of the carbon residues. When the temperature is 1 273 K, the relative content of N elements in the form of N-5 and N-6 on the surface of pulverized coal combustion residues decreases and increases by 7% and 5%, respectively. The main source of NO_x nitrogen-containing precursors released during pressurized O_2/CO_2 combustion is the inherent N-Q structure in coke, and its relative content varies little.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 14925K]

  • Template-assisted hydrothermal synthesis of CuO catalysts for electrochemical CO2 reduction

    GUO Yafei;ZHAO Jiayi;YAO Xi;ZOU Yekun;GAO Yuxuan;LIU Bingqian;ZHAO Chuanwen;School of Energy and Mechanical Engineering,Nanjing Normal University;

    Electrochemical CO_2 reduction(ECR) to value-added products using renewable electricity enables artificial carbon cycle and clean energy storage, which represents an important strategy to realize carbon neutrality. Copper-based catalysts have been recognized as the only materials that can realize the electrochemical reduction of CO_2 to produce a variety of products. However, it faces the challenges of high overpotential and poor products selectivity in ECR. To promote the ECR performance of copper-based catalysts, template-assisted hydrothermal synthesis method was employed to synthesize CuO nanostructures, and the influence of the content of polyvinylpyrrolidone(PVP) template on the structure and ECR performance of CuO catalysts was demonstrated. The results indicate that the nucleation and growth of CuO crystals in hydrothermal synthesis can be affected due to the addition of PVP. The average particle size and ECR performance of the CuO catalysts depends on the content of the PVP template. The hydrophobic carbon chain in PVP endows the molecule with repulsive force, which has retarded the agglomeration of CuO nanostructures. With the increase in PVP content, the average particle size decreases first and then increases, while the ECR performance increases first and then declines. The desired CuO-PVP-25 catalyst with 25% PVP content shows the minimum average particle size of 29.53 nm. Under the given potential of-0.53 V,the CO selectivity and current density of CO_2 electrochemical reduction products can reach up to 48.2% and-5.8 mA/cm~2. The excellent ECR performance is associated with the particle size effect, as catalyst with minimized particle size offers more undercoordinated sites, which affects the binding energy of the catalyst surface towards the adsorption of the ~*CO intermediate, thus significantly affecting the catalytic activity and products selectivity.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 23170K]

  • Research progress on mercury removal in chemical looping combustion of coal

    LIU Zhuang;ZHOU Jinsong;ZHOU Qixin;ZHOU Lingtao;LU Yang;LI Bohao;State Key Laboratory of Clean Energy Utilization,Zhejiang University;

    Chemical looping combustion(CLC) of coal can effectively realize the capture and storage of CO_2, which is of great significance for China to achieve the goal of carbon peaking and carbon neutral. Mercury(Hg) pollution during CLC of coal needs to be effectively solved because of its high toxicity to human and corrosion to aluminum CO_2 compression equipment. In order to promote the effective treatment on Hg pollution from CLC, the effects and mechanisms of gasification medium, gasification products, oxygen carrier(OC), and reaction temperature on Hg release, conversion and migration during the process of CLC were summarized, and the development suggestions were proposed aiming at the problems. CO_2 cannot directly oxidize Hg~0 homogeneously, but it can inhibit the promoting effect of HCl on Hg removal by the OC. H_2O vapor can not only enhances the release of Hg by promoting the precipitation of volatiles in coal, inhibiting the melting of pore structure, and improving coal combustion efficiency, but also reacts with Hg to generate Hg(OH)_2 which is then decomposed into HgO and Hg~0, and inhibits the conversion of HCl to Cl thereby inhibiting the oxidation of Hg~0 to Hg~(2+). Strong reductive gasification products such as CO, H_2 and NH_3 inhibit the oxidation of Hg~0 by consuming the surface oxygen of the OC. H_2S will react with the surface active oxygen of the OC to form surface active sulfur and then promote the removal of Hg~0 by the OC. However, the too much high concentration of H_2S will lead to the formation of cyclic sulfur or chains sulfur on the surface of the OC that are not active in the oxidation of Hg~0. HCl can enhance the performance of the OC on Hg removal. The promotion effect of HCl at low temperature(80-280 ℃) is attributed to the Eley-Rideal mechanism of HCl pre-adsorption, and the promotion effect at medium temperature(280-580 ℃) is ascribed to the Langmuir-Hinshelwood mechanism, and its promotion effect at high temperature(above 580 ℃) is mainly attributed to the homogeneous oxidation of Hg~0 by HCl. The promotion of OC on Hg~0 oxidation is mainly attributed to the direct oxidation of Hg~0 to HgO by reactive oxygen species in the OC, the oxidation of H_2S to reactive S, and the oxidation of HCl to reactive Cl and Cl_2. The increase of temperature in fuel reactor enhances the release of Hg from coal, but also promotes Hg~0 oxidation by promoting the production of Cl and inhibiting the production of CO. The increase of temperature in air reactor not only benefits to the oxidation of Hg~0 in the air reactor, but also inhibits the release of Hg~0 from the outlet of the air reactor by enhancing the full combustion of coal and weakening the adsorption of Hg by coke. Considering the influence of H_2O vapor content on gasification rate, Hg release and Hg~0 oxidation, it is proposed to determine the appropriate H_2O vapor content to achieve the synergistic effect on enhancing gasification rate, reducing the release of Hg, and promoting Hg~0 oxidation. Aiming at the synergistic effect of OC in achieving efficient oxygen transfer and enhancing Hg~0 oxidation in fuel reactors, it is proposed to determine an appropriate OC to realize the "one-body dual-purpose" of OC in oxygen transfer and Hg~0 oxidation. In view of the influence of fuel reactor temperature on Hg release and Hg~0 oxidation in coal, it is proposed to determine the appropriate fuel reactor temperature to minimize the release of Hg in coal in the fuel reactor and enhance the oxidation of Hg~0 thereby promoting the enrichment and purification of CO_2. In view of the influence of air reactor temperature on Hg~0 oxidation, it is proposed to determine the appropriate fuel reactor temperature to enhance the oxidation of Hg in the air reactor as much as possible, thereby reducing the release of Hg from the outlet of air reactor.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 12757K]

  • Research progress on Hg removal performance of Ce-containing materials

    LYU Qiang;GUAN Yu;LIU Yinhe;School of Energy and Power Engineering,Xi′an Jiaotong University;

    Controlling mercury emission from coal-fired boilers is the top priority of mercury reduction in China. It is of great significance to develop efficient and low-cost mercury removal materials for mercury pollution control from coal-fired flue gas. Ce is the most abundant rare earth element, and cerium oxide has the virtues of non-toxicity and relatively inexpensive. More importantly, excellent oxygen storage capacity and redox reaction activity of cerium oxide make it have great application potential in the field of mercury removal. The latest research progress of cerium-containing materials in removing mercury from flue gas was reviewed. The various preparation methods of cerium-containing materials were analyzed, and the key points for building the molecular model of cerium-containing catalysts or adsorbents were emphasized. The mercury removal performance of cerium-containing materials was introduced, and the direction for future study on carbon-based materials and non-carbon-based materials were discussed. The influences of the main flue gas components on the mercury removal performance of cerium-containing materials were discussed in detail. The promotion or inhibition mechanisms of SO_2、H_2O、NO、HCl、NH_3 and O_2 on the elemental mercury removal were summarized. Finally, the prospects of the research on cerium-containing mercury removal materials were proposed. The results show that the preparation of cerium containing materials by impregnation is simple, but the uniformity of the active components is hard to achieve. The coprecipitation method is unsuitable for low loading samples. The sol-gel method can ensure uniform mixing at the molecular level. The materials prepared through template method, hydrothermal method and solvothermal method have good dispersion characteristics, while the flame synthesized catalysts still need further development. The content of cerium and the cerium dispersion state should be considered in the construction of cerium-containing materials molecular model. Physisorption, chemisorption and catalytic oxidation all contribute to the mercury removal from cerium-containing materials. Low concentration SO_2 is favorable for Hg oxidation, but high concentration SO_2 will compete with Hg for the adsorption sites on cerium oxide surface. Cerium-containing materials have better resistance to H_2O compared with other materials. NO can react with oxygen in cerium containing materials to produce NO_2 and promote the oxidation of Hg. Adding CuO to cerium-containing materials can alleviate the adverse effect of NH_3 on mercury removal. The promotion degree of HCl and O_2 on mercury removal efficiency is affected by cerium oxide content. Based on the existing research, the following problems are still to be solved before the commercial application of cerium-containing mercury removal materials: competition or synergistic removal mechanisms of mercury and flue gas components on the surface of cerium-containing polymetallic materials; environmental impact of cerium-containing materials; mercury removal performance of cerium-containing materials in practical flue gas, design and optimization of mercury removal reactor and mercury removal unit, techno-economic study of cerium-containing materials. Based on the experimental and simulation investigations from the literature, the mercury removal performance of cerium-containing materials and the influence mechanisms of flue gas components on the adsorption and oxidation of elemental mercury were summarized. The focus of future work was proposed, in order to lay a foundation for the development and application of cerium-containing materials in the field of flue gas mercury removal.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 31011K]

  • Trans-dimensional analysis on trace elements in coal combustion products based on single particle analytical technique

    HU Yuanquan;GONG Bengen;TIAN Chong;School of Power and Mechanical Engineering,Wuhan University;Energy and Power Engineering,Huazhong University of Science and Technology;

    For obtaining a deep understanding of typical hazardous elements distributions in coal combustion products(CCPs) from micro to nano size, the products of a coal-fired power plant(slag BA, fly ash FA, gypsum SG) were selected as the research objects. After the sample was divided into particle sizes by ultrasonic dispersion and centrifugation, the distribution of As, Pb and Cr was analyzed by single particle plasma time of flight mass spectrometry(spICP-TOF-MS). The data extracted by machine learning integration were used to analyze the three elements in the whole sample of coal-fired products, 1-10 μm and <500 nm particles. The results indicate that the As, Pb, and Cr are obviously enriched in FA. Particle size from 1 μm to 10 μm will affect the distributions of As and Pb in FA and SG samples. Distributions of Cr in particles from all the samples are not affected by the particle size. There are 3 426, 18 386, and 3 787 particles can be measurement(<500 nm). Pb and Cr bearing single nano-size particles are abundant in comparison with As bearing single particles both in FA and SG samples. As, Pb and Cr bearing particles in SG samples are more abundant than that in FA samples, and the proportions of particle numbers are 1.1%, 3.6% and 7.6% respectively. As, Pb and Cr show strong associations with Fe, Ti, Mg and Al in the BA, FA and SG samples. As also shows a high association frequency with Cr, Rb, Mn and Pb in FA. Pb has high associations with Ba, Ce, Ga, Zr and Cr in FA. While in the SG samples, As, Cr and Pb have very strong associations. In addition, Cr is also found to be associated with Sn, Ni and Rb in SG samples. The enrichment of As, Pb and Cr in coal-fired products with different particle sizes is closely related to the process of coal-fired multicomponent nucleation and particle growth. The multicomponent in coal has varying degrees of influence on the morphological transformation and distribution of these three elements. The research results lay a foundation for further revealing the mechanism of large-scale migration and transformation of heavy metals in coal-fired particles.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 19417K]

  • Hg removal by MnOx sorbent supported on MgO-Al2O3 composite oxides

    GUI Ben;XU Jie;HU Yuqing;CHEN Mu;LIU Yu;ZHOU Zijian;LIU Xiaowei;Central Southern China Electric Power Design Institute Co.,Ltd.,China Power Engineering Consulting Group;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

    Natural mineral(MgO) is considered to be an excellent support for loading MnO_x to remove Hg~0 from coal-fired flue gas. However, the restricted specific surface area of MgO limits its utilization efficiency for Mn species, and the amount of Mn species is always quite high. In order to improve the utilization of Mn active species by MgO support in the reaction of removing Hg~0 from flue gas, MnO_x sorbents supported by MgO-Al_2O_3 composite oxides were synthesized by partially replacing MgO with Al_2O_3. With the aid of the large specific surface area and the high proportion of chemically adsorbed oxygen(O_(ad)) on the surface of Al_2O_3, the adsorption and oxidation capacity of Mn species for Hg~0 was improved, and a sorbent with higher Hg~0 removal efficiency was obtained. The activity test results show that when only 5% Mn species is loaded, adding 30% Al_2O_3 into the support can improve the Hg~0 removal efficiency by 27.7% compared with the sorbent without Al_2O_3 in the N_2+10% O_2 atmosphere at 150 ℃. The mechanism of the sorbent for Hg~0 removal was revealed by H_2-TPR and XPS. H_2-TPR shows that Al_2O_3 will interact with MgO to form a more stable carrier species after the addition of Al_2O_3. XPS shows that the proportion of Mn~(4+) species on the sorbent surface has an important influence on the Hg~0 removal activity. When adding 30% Al_2O_3, the proportion of Mn~(4+) species on the sorbent surface is the highest, so the Hg~0 removal activity is the highest. In view of the limitation of Mn active components by MgO support, the method of adding Al_2O_3 can improve the utilization of the active species, which has a guiding significance for the application of natural mineral support in the field of Hg~0 removal.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 39511K]

  • Nitrogen conversion research of flameless combustion based on In-Situ Adaptive Tabulation and dynamic adaptive chemistry

    CHENG Pengfei;LI Pengfei;LIU Lu;HU Fan;LIU Zhaohui;ZHENG Chuguang;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

    Based on the finite-rate numerical simulation coupled with detailed reaction mechanisms of nitrogen, the strong turbulence-chemistry interaction in flameless combustion can be considered, and the prediction accuracy of key combustion parameters and NO formation can be improved. A reasonable fast calculation method was builded that can greatly accelerate the calculation without significantly sacrificing the simulation accuracy. A coupled calculation method of In-Situ Adaptive Tabulation and Dynamic Adaptive Chemistry was developed based on the high-fidelity numerical simulations of CH_4/H_2 flameless combustion with a hot co-flow, then the nitrogen conversion mechanisms of flameless combustion was further analyzed. It is found that the coupled calculation method can ensure the higher accuracy required for the simulations and double the calculation speed compared with a single method. It can be further optimized with a reasonable error threshold and the Dynamic Adaptive Chemistry threshold 10~(-2) performs best overall. The coupled calculation method has a larger simplification space for high-complexity mechanisms, and a nearly 10.8 times calculation acceleration is obtained with one detailed reaction mechanism of nitrogen containing 151 species and 1 397 reactions. Based on the experimental validation and the nitrogen conversion path analysis, the NO formation of CH_4/H_2 flameless combustion with a hot co-flow mainly depends on the NNH path and the N_2O intermediate path, while thermal-NO and prompt-NO can be ignored.Compared with the In-Situ Adaptive Tabulation, the nitrogen conversion path analysis can be properly simplified and the main NO paths can be retained with the coupled calculation method.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 32156K]

  • Carbon emission and reliability analysis of multi-energy complementary power system

    DONG Rui;LI Xing;GAO Lin;Wu Zhonghua College,North China Electric Power University;Institute of Engineering Thermophysics,Chinese Academy of Sciences;Huadian Heavy Industry Co.,Ltd.;

    With the proposal of the dual carbon goal, it is necessary to accelerate the construction of a safe, economical and low-carbon power system in China. However, a high proportion of thermal power installed capacity has high CO_2 emissions, and large-scale renewable energy installations will lead to poor reliability of the power system. The integration of energy storage and carbon capture equipment can take into account the issues of carbon emissions and system reliability to a certain extent, but at the same time, it will also lead to an increase in the cost of power generation. Based on an energy base, the carbon emission intensity and reliability indicators of the system under different renewable energy installed proportions were analyzed, and the carbon capture amount and the required amount of carbon capture were given when the system met the carbon emission and reliability constraints under different technical routes. The system economy after unified carbon emission and reliability indicators was compared. The results show that through biomass coupled carbon capture technology, zero carbon emission or even negative carbon emission can be achieved in the power system. Energy storage can effectively improve system reliability. For a system with a total installed capacity of 5 000 MW, for every 20% increase in the proportion of installed renewable energy, energy storage equipment with a power of 850-875 MW needs to be connected to meet the reliability requirements of the system. As carbon emission requirements increase, the cost of system power generation continues to rise, and the system has the highest economy at 60% of installed renewable energy under the premise of meeting carbon emission and reliability constraints.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 7561K]

  • CFD optimization of multilayer gas distributor in slurry bed reactor for Fischer-Tropsch synthesis

    BU Yifeng;PAN Teng;MEN Zhuowu;CHENG Youwei;National Institute of Clean-and-Low-Carbon Energy;College of Chemical and Biological Engineering,Zhejiang University;

    Gas distributor is one of the most important internals in Fischer-Tropsch slurry bed reactor, which can affect the hydrodynamics behavior and reaction performance of the reactor. In order to fully use the bottom head space of the slurry bed reactor, a muti-layer turbular slurry bed gas distributor was designed based on existing engineering experience. Under the given size and benchmark design conditions of the 5-layer gas distributor, computational fluid dynamics(CFD) was used to simulate and optimize the distributor structure. Firstly, the gas in the distributor could be treated as three-dimensional steady incompressible fluid. Since the outlet gas of the distributor was in turbulent state, the single-phase turbulence model SST-kω was selected to match the condition of curvature flow in the distributor. Then, the modeling was established based on the controling equations such as fluid continuity equation and momentum equation, the computational fluid dynamics software STAR-CCM+ was used to solve the above equations and the three-dimensional flow field of multi-layer gas distributor was numerically simulated. The results show that the benchmark design has the problems of bias and uneven flow distribution for a given 5-layer gas distributor. Finally, the nozzle parameters(length, radius and number) in each layer of the distributor were taken as the design variables, the gas distribution uniformity was taken as the objective function, and under the restrictive condition that the gas velocity at the outlet of the distributor nozzle was not higher than 75 m/s, the SHERPA algorithm was used to iterate 120 times for 15 design parameters, the range of 15 design parameters was covered in the optimization process. The results show that the optimization range of nozzle number is 9-15,the nozzle radius ranges from 9 mm to 14 mm, and the nozzle length is close to the upper limit of 150 mm to adjust the pressure drop through the fluid, overcome the static pressure difference of each layer of the distributor and make the gas evenly distributed among the annular distribution pipes of each layer. Moreover, the nozzle radius of the distributor should increase with the increase of layers, the number of nozzles must be coordinated with the radius and length of nozzles to achieve the optimal gas distribution performance. The final optimized distributor can obtain uniform and reasonable flow distribution without short circuit, the streamline is smooth without local vortex and other non ideal flow field.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 17538K]

  • Effect of halogen elements on the mercury emission from wet flue gas desulfurization system

    CHANG Lin;ZHANG Yi;LIU Yi;LIAO Haiyan;YU Xuehai;HAN Tao;ZHAO Rui;ZHANG Shuai;WANG Jing;ZHAO Yongchun;Guoneng Guohua (Beijing) Electric Research Institute Co.,Ltd.;National Energy Investment Group Co.,Ltd.;Sanhe Power Generation Co., Ltd.;State Key Laboratory of Coal Combustion,HuaZhong University of Science and Technology;

    The composition of desulfurization slurry is complex due to the recycling utilization of the slurry, in particular the halogen elements are easy to accumulate in the slurry and difficult to be removed. Oxidated mercury is water soluble and is easy to be removed by wet flue gas desulfurization(WFGD) system, however, the absorbed mercury in the desulfurization slurry has the problem of secondary release. Therefore, the influence of halogen elements on Hg emission in WFGD system was systematically studied in the lab-scale by on-line monitoring and the influence of reaction temperature, halogen species, halogen concentrations, and reaction pH on mercury release were investigated. The mechanism of mercury emission behavior was also simulated. The results indicate that the mercury emission is inhibited by halogen elements in the increasing order of Cl<Br<I. Increasing the reaction temperature is conducive to reducing the release intensity of mercury where the over 20% decrease is achieved with the temperature increasing from 40 ℃ to 60 ℃. Increasing the concentrations of halogen elements results in a remarkable inhibition of mercury emission. When the concentrations of Cl, Br, and I increase from 5 mmol/L to 50 mmol/L, mercury emission are reduced by 23.5%,53.8%,and 62.8%, respectively. After increasing the reaction pH, the reduction potential of the reaction system decreases, which can weaken the protonation of the intermediate products, and is conducive to reducing the intensity of mercury release. The addition of halogen element can alter the pathway of mercury emission and mercury and halogen will form a series of complexes, reducing the contact between mercury and reducing substances in the system to form unstable intermediate HgSO_3, thus reducing the release intensity of mercury.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 8644K]

  • Research progress on preparation and strength of high reactivity ferro coke

    ZHANG Shengfu;YIN Cheng;QIU Shuxing;WEN Liangying;BAI Chenguang;College of Materials Science and Engineering,Chongging University;Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and Advanced Materials,Chongging University;Pangang Group Research Institute Co.,Ltd.,PanGang Group;

    The increasing China′s steel output is at odds with the shortage of high-quality coking coal resources and environmental problems. Therefore, it is urgent to optimize ironmaking process, realize energy saving and emission reduction of blast furnace. Improving the carbon utilization rate is an effective measure to reduce the coke ratio of blast furnace and CO_2 emission. As a kind of iron-carbon composite burden that is expected to realize industrial application, ferro coke has been extensively studied. Its high reactivity can effectively reduce the temperature of the thermal reserve zone in blast furnace, improve the smelting efficiency, thus reduce coke ratio and carbon emission. In this work, the development history and current research status of ferro coke were reviewed and the characteristics of different ferro coke preparation processes and the properties of ferro coke were compared. The investment cost of preparing ferro coke by directly adding iron ore powder to coal is small, which can be realized by using existing coke oven facilities. However, the temperature of coke oven should be strictly controlled, otherwise the life of coke oven will be reduced. Hot pressing ferro coke preparation process can use a large amount of weakly bonded coal or non-bonded coal, the prepared ferro coke has high reactivity and post-reaction strength, has realized industrial production and application. Cold pressing ferro coke preparation process can further reduce the energy consumption of coking, but the strength of ferro coke needs to be optimized. In coking process, the iron-bearing minerals added to coal are reduced to metal iron, and its oxidation reaction catalyzes the gasification of ferro coke in the blast furnace. In view of the strength deterioration of ferro coke, a solution is proposed to add additives containing metaplast such as toluene, ethylbenzene, oxylene and long branched alkanes during the coking process, which gives a feasible way for preparing high strength and high reactivity ferro coke that meets the requirements of blast furnace. The results show that the mixed charging mode of ferro coke and iron bearing burden can not only reduce carbon emission, but also does not affect the permeability of blast furnace. The synergistic optimization of reactivity and strength of ferro coke, the behavior of ferro coke in blast furnace and the effect of ferro coke on energy consumption of blast furnace are the key research directions in the future.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 32694K]

  • Research progress on characteristic analysis and resource utilization of coal gasification slag

    FAN Ning;ZHANG Yiqun;FAN Panpan;FAN Xiaoting;WANG Jie;WANG Jiancheng;DONG Lianping;FAN Minqiang;BAO Weiren;Shanxi Coal Import and Export Group Co.,Ltd.;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;College of Mining Engineering,Taiyuan University of Technology;

    In China, the energy structure is characterized by rich coal, poor oil and less gas, and the development of coal chemical industry is full of opportunities and challenges. Coal gasification technology is the front-end process of modern coal chemical industry. It is an effective way to realize clean, efficient, green and low-carbon utilization of coal, and has important national strategic significance. However, the disposal of a large amount of solid waste(coal gasification slag) produced by the large-scale application of coal gasification technology is a pain point that coal chemical bases urgently need to solve. Starting from the particle size composition, mineral composition, micro morphology, surface properties, water holding properties and other physical and chemical properties of gasification ash of representative coal chemical industry bases in China, the characteristics of ash under different furnace types, different places of origin, different gasification processes and other conditions were compared, analyzed and summarized. The difference of physical properties of ash and slag is related to gasification process, furnace type, coal type and other factors. The main components of ash are silicon and aluminum minerals. The particle size of coarse slag is generally too large. The residual carbon content of fine slag is generally about 20%, and its surface is rich in oxygen-containing functional groups. In addition, the water content of fine slag is high due to its high porosity. Based on the physical and chemical properties of gasification ash, the reported methods for improving the quality of gasification slag were systematically summarized. It is proposed that carbon-ash separation is an important prerequisite for realizing the reduction and resource utilization of gasification slag. From the perspective of efficient recovery of micro fine minerals, flotation is the most suitable carbon-ash separation method. However, due to the developed pore structure of carbon residue and the existence of oxygen-containing hydrophilic groups, the floatability is poor, and the current production cost is high. From the point of reducing production cost and increasing treatment capacity, gravity separation method is the first choice, but there is a problem of higher separation size limit. Magnetic separation is more targeted for ash with high content of ferromagnetic minerals and is not generally applicable. Based on the characteristics of the above separation methods, the development of large-scale separation equipment, new high-efficiency flotation reagents and flotation methods, and high efficiency and low consumption combined separation process of gasification slag are the research focus in the follow-up field of carbon-ash separation. In addition, the research progress of resource utilization of gasification ash was systematically summarized. Application fields such as building materials can realize the large-scale consumption of gasified slag, which is the primary utilization direction to improve the comprehensive utilization rate of solid waste. It is necessary to further study the follow-up problems such as drying and dehydration of gasified slag and precipitation of heavy metals. In the fields of ecological restoration, boiler mixed combustion, carbon material preparation, adsorption/catalyst preparation, etc., the high-value utilization of gasification slag can be realized, and the market capacity should also be fully considered. Taking the downstream market as the guide, comprehensively considering the technical status, cost accounting, market consumption and other factors, and combined with the concept of efficient separation and quality utilization, it is an effective way to realize the resource utilization of gasification slag, where the enterprise benefits and environmental protection benefits can be achieved. At the same time, it is also an important supplement to realize the high-end, diversified and low-carbon development of coal chemical industry.

    2022 08 v.28;No.144 [Abstract][OnlineView][HTML全文][Download 19555K]
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