• Emission control of unconventional pollutants during coal combustion

    ZHANG Junying;CUI Xiangzheng;WANG Zhikang;WANG Jianhao;XIAO Rihong;XIONG Zhuo;ZHAO Yongchun;National Key Laboratory of Coal Combustion and Low Carbon Utilization,Huazhong University of Science and Technology;National Environmental Protection Engineering Technology Center for Trace Elements Pollution Control and Low Carbon Utilization of Coal;Wuhan Branch of National Energy Group Science and Technology Research Institute Co.,Ld.;

    With the development of industry, people are increasingly concerned about environmental protection and health issues. Coal-fired power plants are one of the main anthropogenic sources of atmospheric pollutants. Currently, China′s control of conventional pollutants such as dust, SO_2, and NO_x has reached international leading levels. At the same time, the control of unconventional pollutants generated during the coal combustion process, such as PM_(2.5), heavy metals, mercury, SO_3, and VOCs, has become a hot and challenging research topic. Based on the characteristics of the generation and emission of unconventional pollutants in coal-fired power plants, the advantages, disadvantages, and challenges of current air pollutant control devices(APCDs) and various unconventional pollutant control technologies were analyzed. Specifically, the current situation of controlling the emission of five typical unconventional pollutants from coal-fired power was discussed. Firstly, the current status of PM_(2.5) emission control during coal combustion was analyzed from the perspective of various agglomeration technologies. Secondly, the current status of heavy metal emission control was analyzed from three perspectives: before combustion, during combustion, and after combustion, and the advantages of heterogeneous agglomeration technology in treating heavy metal pollution from coal-fired power were elaborated. Thirdly, the current status of mercury emission control was analyzed from the perspectives of carbon based and non carbon based adsorbents, and the demonstration effect of magnetospheres mercury removal technology in controlling mercury emissions from coal combustion was emphasized. Fourthly, the current status of SO_3 emission control was analyzed from the perspectives of alkaline adsorbents, chemical agglomeration, and non alkaline adsorbents, highlighting the innovation of high-temperature Sulfonation-based SO_3 removal. Fifthly, the current status of VOCs emission control was analyzed from the perspectives of tail gas purification devices and activated carbon injection technology. In addition, considering the current status of unconventional pollutant control in China, suitable methods for synergistic removal of pollutants were proposed, providing a reference for the future application of multi-pollutant synergistic removal technologies in coal-fired power plants.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 13470K]

  • Research progress on resource recycling technology of retired wind turbine blades in bulk wind power plants

    MA Wenjing;ZHANG Yutong;YANG Chunzhen;HU Zhongfa;WANG Zhongquan;SUN Jinyu;TAN Houzhang;WANG Xuebin;School of Energy and Power Engineering,Xi′an Jiaotong University;Southern Offshore Wind Power Joint Development Co.,Ltd.;Guoneng(Shandong)Energy & Environment Co.,Ltd.;College of Energy,Soochow University;Nan Dian Energy Comprehensive Utilization Co.,Ltd.;

    After putting forward the goal of "carbon neutrality" in 2020,wind power generation in China has shown explosive growth, with the increasing demand for fan blades. At the same time, large-scale wind turbines have gradually begun to retire. It is expected that the cumulative number of retired wind turbine blades in China will reach 2.88 million tons by 2040. Because of the complexity of the materials used in the blades, resource recovery and utilization remains a challenge. The manufacturing characteristics of blades, the source of waste, the necessity of treatment were introduced, and the treatment technologies from the aspects of environmental impact and product value were elaborated. The research results show that the current treatment methods for blades include mechanical treatment, landfill treatment, chemical dissolution treatment, incineration treatment and pyrolysis treatment, among which incineration treatment includes incineration power generation and collaborative disposal of cement kiln. Finally, according to the characteristics of retired wind turbine blades and the advantages and disadvantages of treatment methods, and combined with the current actual situation in China, it is recommended to give priority to the development of collaborative disposal of cement kiln. The combustion of combustible components in the wind turbine blades can provide energy for cement sintering, while solid residues such as glass fiber are used as clinker cement raw materials. This method can maximize the resource utilization of the retired wind turbine blades, but the mixing ratio should be reasonably controlled. In addition, the pyrolysis treatment method can be properly developed to completely treat retired wind turbine blades, with the advantages of capacity reduction, volume reduction and resource recovery. But treatment cost is high, and pyrolysis products are difficult to reuse. Therefore, the key to improving the economic benefits of pyrolysis treatment is to give full play to the value of pyrolysis products and reduce treatment costs.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 25811K]

  • Research progress of sodium migration and transformation during combustion of Zhundong coals in China

    MA Rui;WEI Bo;FAN Weidong;YAO Qiang;TAN Houzhang;YAO Hong;ZHU Quan;WU Xiaojiang;KONG Chengdong;MA Xiaojing;School of Electrical Engineering,Xinjiang University;School of Mechanical and Power Engineering,Shanghai Jiao Tong University;State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources,Xinjiang University;Key Laboratory of Coal Clean Conversion & Chemical Engineering Process,Xinjiang Uygur Autonomous Region,School of Chemistry Engineering and Technology,Xinjiang Univ

    In recent years, the discovery of a large number of low-ranking Zhundong Coalfield in the Junggar Basin in western China has attracted extensive attention from scholars. The Zhundong Coalfield is the largest whole coal field discovered in China, with proven reserves of more than 390 billion tons, enough to supply China′s coal consumption for nearly 100 years. Zhundong coals, characterized by low ash, low sulfur, high reactivity, large reserves and easy exploitation, is a high-quality fuel for future coal chemical industry and coal power projects. However, the content of alkali metal sodium in Zhundong coals is relatively high, and sodium is easy to volatilize during combustion, resulting in a series of problems such as boiler fouling and slagging, especially sodium chloride and sodium sulfate migration will cause a series of ash-related problems, a serious constraint on the large-scale, efficient and clean utilization of Zhundong coal. Thus, the distribution and coal quality characteristics of Zhundong coals, as well as the occurrence and measurement methods of sodium content were reviewed in detail. The internal and external migration mechanism of sodium and the effects of inorganic elements such as aluminosilicate, chlorine, calcium and potassium in coal on sodium migration were highlighted. The effects of reaction conditions such as temperature, pressure, atmosphere, particle size and additives on sodium migration were comprehensively reviewed. Although a number of studies including experiments, heat balance calculation and simulation have been carried out, the ash-related problems caused by alkali metal release have not been solved, and the understanding of the causes is not comprehensive enough. Therefore, the focus of this study is to review the research progress and reveal the mechanism of sodium migration.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 51088K]

  • Application progress on biomass alternative fuel in cement industry

    WANG Junjie;YANG Huawei;ZHAN Yueping;CHAI Zhen;CAI Jun;ZHU Zhiping;State Key Laboratory of Coal Conversion,Institute of Engineering Thermophysics,Chinese Academy of Sciences;Shanxi Key Laboratory of Coal Flexible Combustion and Thermal Conversion;Shanxi Engineering Research Center of Coal Clean,Efficient Combustion and Gasification;University of Chinese Academy of Sciences;

    The cement industry is an important basic raw material industry, and also an industry with high energy consumption and high carbon emissions. China has abundant biomass resources. As alternative fuel, the application of biomass in the cement industry can help reduce the fossil energy consumption and carbon emissions, which is one of the main ways to achieve carbon neutrality for China′s cement industry. Progress and existing problems for biomass to be applied in the cement industry was analyzed, and solutions were gave. Compared with traditional fossil fuels, biomass fuel has such characteristics as high moisture content, low calorific value and large size. When it is used in cement production, these problems such as lower fuel burnout rate, higher flue gas volume, higher heat consumption, higher alkali content and larger fluctuation might be caused. A series of standards on solid recovered fuel(SRF) have been established abroad, laying a foundation for the standardized preparation and large-scale use of SRF including biomass in cement industry. According to the dataissued by the Global Cement and Concrete Association, the proportion of biomass fuel in the global cement industry accounted for 6.7% in 2020, among which agricultural, organic, diaper waste accounted for the largest proportion, i.e., 32%. The biomass fuel in Czech Republic, Germany, and Poland accounted for more than 22%. In contrast, the use of biomass and other alternative fuels in China′s cement industry started late. By 2021, the proportion of cement production lines using alternative fuels was less than 3%, and the thermal substitution ratio was about 2%. From the perspective of domestic application, biomass as alternative fuel can help reduce fossil fuel consumption, but there are still some problems such as incompatibility with the existing thermal system, low efficiency of thermal utilization, and certain influence on the production and quality of clinker. In order to reduce the negative impact of biomass fuel, it is necessary to pretreat it. Therefore, relevant technologies including mechanical pretreatment and high-temperature combustion pretreatment were introduced, and their advantages and disadvantages were compared. At the end of the paper, the main problems on the application of biomass fuels in cement industry were analyzed and the corresponding solutions were put forward. The solutions are to strengthen the pilot study and enhance its guidance to the actual production, improve relevant standards and establish an industry chain of alternative fuels including biomass, use the large amount of low-temperature waste gas from cement kiln to dry biomass fuel and reduce the water brought into the system, optimize the relative positions of biomass fuel fed to calciner by CFD simulation, popularize the high temperature combustion pretreatment technology such as circulating fluidized bed per to the type of biomass fuels, develop intelligent control system for alternative fuels and reduce the impact on clinker production quality. The cement industry is an important battleground for China′s carbon emission reduction. Biomass as alternative fuel will certainly show strong vitality and broad application prospects in the cement industry, and make important contributions to the realization of China′s dual-carbon strategic objectives.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 16836K]

  • Research progress on prediction model of fluidity behavior parameters of molten slag in the entrained flow bed coal gasification

    ZHAO Chaoyue;BAI Yonghui;SONG Xudong;SU Weiguang;LYU Peng;WANG Jiaofei;YU Guangsuo;YAO Min;State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering,College of Chemistry and Chemical Engineering,Ningxia University;Institute of Clean Coal Technology,East China University of Science and Technology;

    The ash fusion characteristics and viscosity-temperature characteristics of coal are the two indexes parameters for the discharge of the molten slag in the entrained flow bed(EFB). The chemical reaction in EFB gasifier is under harsh conditions of high temperature, high pressure, and turbulent with multiple phase reactions, and it is difficult to obtain the molten slag fluidity behavior parameters by experience, and establishing a model that predicts these parameters is of vital importance. Based on the analysis of ash melting characteristic parameters(ash melting temperature, full liquid phase temperature), viscosity temperature characteristic parameters(viscosity, critical viscosity temperature) and influencing parameter factors, the prediction principles and steps of four methods: regression analysis, software prediction(FactSage, LAMMPS), mathematical modeling(backpropagation neural network, support vector machine) and ion potential prediction method were expounded, and the prediction model for the construction of ash fusion characteristic parameters and viscosity-temperature characteristic parameters was systematically reviewed. Finally, the advantages, disadvantages and application scope of the four methods for predicting coal ash flow behavior were summarized. Based on the composition of coal ash and its microstructure, combined with thermodynamic and kinetic simulation software, the mathematical model was used to optimize a the flow parameters. So as to establish the optimal prediction formula, which is of great significance to guide the accurate prediction of molten slag fluidity behavior in the EFB gasification process.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 12833K]

  • DFT investigation on H_2O_2 adsorption, decomposition and NO oxidation behaviors in H_2O_2/Fe_2(MoO_4)_3 system

    LIU Xuan;LYU Qiang;WANG Chang′an;CHE Defu;LI Caiting;College of Environmental Science and Engineering,Hunan University;Key Laboratory of Environmental Biology and Pollution Control (Hunan University),Ministry of Education;State Key Laboratory of Multiphase Flow in Power Engineering,Xi′an Jiaotong University;

    To elucidate the adsorption/decomposition behavior of H_2O_2 and oxidation behavior of NO in H_2O_2/Fe_2(MoO_4)_3 denitrification system, density functional theory(DFT) calculations were performed to investigate the individual adsorption and co-adsorption characteristics of H_2O_2 and NO on Fe_2(MoO_4)_3 surface for the first time. The adsorption energies, Mulliken population, and oxidation pathways were systematically analyzed to reveal the mechanism of catalytical decomposition of H_2O_2 and NO oxidation. The results show that H_2O_2 can be easily decomposed into reactive radicals on Fe_2(MoO_4)_3 surface, while NO is adsorbed in molecular form. In the case of co-adsorption, H_2O_2 preferentially adsorbs on the catalyst surface and undergoes decomposition process. NO is subsequently oxidized to HNO_2/NO_2 by the hydroxyl group/oxygen atom generated from H_2O_2 decomposition. The oxidation products HNO_2/NO_2 are only bonded to the catalyst surface via hydrogen bond and can easily enter the mainstream flue gas under flow disturbance, thus reducing the deposition possibility of nitrate on catalyst surface. This study unravels the micro mechanism of H_2O_2 adsorption/decomposition and NO oxidation on Fe_2(MoO_4)_3 surface, providing theoretical guidance for designing heterogeneous Fenton-like denitrification system with high catalytic activity and excellent stability.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 32458K]

  • Naphthalene rings cleavage mechanism in supercritical water

    ZHAO Hao;ZHANG Yingjia;HUANG Zuohua;State Key Laboratory of Multiphase Flow in Power Engineering,Xi′an Jiaotong University;

    Supercritical water gasification technology is a new type of technology for efficient, clean, and low-carbon utilization of coal, which can directly convert coal into products such as hydrogen and carbon dioxide, and precipitate pollutants such as nitrogen, sulfur, and heavy metals in coal in the form of solid inorganic salts. The ring opening reaction of polycyclic aromatic hydrocarbons is one of the rate-determining steps in the supercritical water coal gasification process. The molecular dynamics simulation software(LAMMPS) were performed to study the ring opening reaction process of the simplest PAH naphthalene under supercritical water atmosphere, the different temperatures and equivalence ratios. Combined with self programming analysis of atomic bond level changes and extraction of elementary reactions, the quantitative reaction kinetics analysis was achieved. The simulation results indicate that the number of naphthalene molecules decreases exponentially at high temperatures, and the reaction rate is weakly correlated with the equivalence ratio. The reaction path analysis shows that the ring opening path of naphthalene mainly includes pyrolysis, H atom abstraction, and OH radical addition reactions. The channel branching ratio of dehydrogenation reaction and OH radical addition reaction increases linearly with the decrease in temperature. The species flux analysis indicates that OH radical is mainly from the reaction of ■,while the pyrolysis of naphthalene molecules is the main pathway for hydrogen atom generation. The reaction between hydrogen atoms generated by water molecule pyrolysis and OH radicals is close to equilibrium, rarely contributing to the source of OH radical. The quantitative analysis results of ring opening reactions can provide reference for the detailed reaction kinetics mechanism of aromatic hydrocarbons in supercritical water atmosphere.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 10772K]

  • Mechanism of synergistic adsorption of CO_2 by metal oxides and nitrogen-doped biomass

    WANG Huichun;WANG Ying;GU Mingyan;CHEN Ping;School of Energy and Environment,Anhui University of Technology;

    At present, there are many adsorption materials, such as zeolite, MOFs, polymers, etc, while biomass has the advantages of wide distribution, low cost, renewable and net zero emissions, which has become a research hotspot. Previous studies have shown that nitrogen doping is beneficial to improving the CO_2 adsorption performance of biocha, and biochar can be modified by metal minerals to increase the effective adsorption area of biochar surface. However, it is still not clear which nitrogen groups significantly affect the CO_2 adsorption performance on the surface of biochar. The adsorption characteristics of CO_2 on the surface of biochar under the synergistic effect of metallic minerals and nitrogen-rich modification are not yet clear. Based on this, quantum chemistry theory was used to calculate and study the adsorption mechanism of CO_2 on the surface of biochar with different nitrogen-containing groups, and the influence mechanism of different metal oxides(MgO,CaO) and their coupled nitrogen-doped biochar on CO_2 adsorption was systematically explored. The results show that biochar containing N-X has the strongest adsorption effect on CO_2 among the different adsorption methods of nitrogen-containing biochar. By analyzing the three different adsorption modes of CO_2 in MgO and CaO systems, namely O-Top, Hollow, and Bridge, it is concluded that the adsorption energy of CO_2 in O-Top mode on CaO system is the maximum, and the adsorption energy of CO_2 in O-Top mode is 92.22 kJ/mol higher than that in MgO under the same adsorption mode. Compared with MgO,O in CaO has a stronger effect on C in CO_2,with more overlapping electron clouds, more charge transfer, and stronger gravitational attraction between CaO and CO_2 molecules. Further study show that the coupling of N-X biochar and CaO has a certain synergistic promoting effect on the adsorption of CO_2. Compared with N-X biochar and CaO alone, the adsorption energy of CO_2 by the coupling of the two increases by 136.81 kJ/mol and 0.87 kJ/mol, respectively. This study provides theoretical support for the preparation of high quality carbonaceous chemicals.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 30122K]

  • Characteristics of single-coal-particle ignition in ammonia-coal cofiring process

    WU Ziqiu;HUANG Qian;MA Peng;YANG Yuanping;SI Tong;LI Shuiqing;Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,Department of Energy and Power Engineering,Tsinghua University;

    The development of mixed combustion of green ammonia and coal in coal-fired power plants is beneficial to the carbon reduction of thermal power towards the goal of carbon neutrality. The ignition characteristics of coal particle is the key factor affecting the flexible operation of the units in the process of gradually increasing the ammonia mixing ratio in the furnace with the technology of mixed combustion. Based on the path of blended combustion technology for ammonia and coal powder mixed feed, a new two-stage flat flame burner was used to study the ignition characteristics of single particle coal powder during ammonia coal mixed combustion process. The ignition mode and ignition delay time of the pulverized Zhundong coal particles under different operating conditions(ammonia volume fraction of the carrier gas and the ambient oxygen concentration) were obtained from the image analyses with the high-speed photography and the backlight method. It is found that the ignition process of particles is dominated by the heterogeneous ignition mode dominates at the absence of ammonia, while ammonia cofiring increases the proportion of coal particles undergoing homogeneous ignition. Meanwhile, with an increase in the ammonia cofiring ration, the proportion of fragmented coal particles during the devolatilization stage increases. At the same time, by constructing a one-dimensional transient coal powder ignition model containing ammonia combustion reaction, the influence of ammonia on the ignition characteristics of coal powder particles can be well reproduced. The effect is relatively small under the central reducing atmosphere.When the central oxygen volume fraction is 0.1 or 0.2,the addition of ammonia significantly reduces the ignition delay time of a single particle, mainly due to the ammonia flame increasing the heating rate of coal powder particles.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 17110K]

  • Pyrolysis behavior of typical medical waste and its product characteristics

    LEI Su;LI Aijun;WU Yangwei;YAO Hong;ZHANG Tong;HU Hongyun;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;School of Energy and Power Engineering,Huazhong University of Science and Technology;

    Fast pyrolysis has obvious advantages in producing energy products and reducing environmental pollution, so it is regarded as an excellent medical waste treatment technology. The characterization method of GC-MS coupled with LC-HRMS was used to supplement the detection blank of components with high boiling point in pyrolysis oil of medical waste, and the component characteristics and variation rules of pyrolysis products of typical medical waste were accurately revealed. It is found that the pyrolysis of cotton sticks mainly produces pyrolysis oil and char, with yields of about 40%. The pyrolysis gas is mainly composed of CO and CO_2,and the main components of oil are aldehydes, ketones, acids and phenols. The characteristic components of oil are sorbic acid and 3-(4-hydroxy-3-methoxyphenyl) propionic acid. With the increase of temperature, the components such as CO,H_2,CH_4,aldehydes, ketones and acids gradually increase, while phenols gradually decrease. The surface functional groups or structures of cotton sticks pyrolysis char include —OH,—CH_x,■,aromatic skeleton and C—O. The pyrolysis oil in the pyrolysis products of masks accounts for more than 65%,with almost no pyrolysis carbon generated. The pyrolysis degree of medical masks at 400 ℃ is very low. The yield of pyrolysis oil is as high as 92.56% at 500 ℃,and about 30% of pyrolysis oil is converted into pyrolysis gas at 600 ℃. The pyrolysis products of medical masks are mainly C_2H_2 and 2,4-dimethyl-1-heptene, and some olefins will be cyclized into toluene at higher temperatures. The pyrolysis oil yield of rubber gloves is more than 60%,and the yield of char is about 20%. The pyrolysis gas of rubber gloves is mainly C_1-C_2 hydrocarbons. The pyrolysis oil of rubber gloves is mainly composed of olefins and aromatic hydrocarbons, accounting for more than 70% of the total, and D-limonene is its characteristic component. At 600 ℃,aliphatic hydrocarbons are easily cyclized to aromatic hydrocarbons. The surface structures of rubber gloves pyrolysis char are mainly aromatic ring skeleton, and some —OH.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 27272K]

  • Technical economic prospect on hydrogen production and storage strategy: A critical analysis

    DING Ning;CHEN Qianhui;LIU Danhe;QI Wenyi;Sinopec Engineering Group Luoyang R&D Center of Technologies;

    Hydrogen, which has been seen as a kind of significant industrial source, has been increasingly focused as the clean energy in a net-zero carbon emission future, with broad application prospects in the fields of transportation, energy supply, metallurgy and chemical industry. Nevertheless, the development and application of hydrogen, especially green hydrogen, have been restricted with technologies and costs in its production, storage and transport process. It should be confirmed that quite a bit of the energy will be lost in the transformation and transportation process whether in high-pressure compressed form, liquid form or other Power-to-X strategies. Furthermore, it was easy to understand more reliable life cycle economic analysis of hydrogen would be estimated while energy efficiency was considered. By comparison, liquid hydrogen and ammonia were regard as the better methods for large-scale power or heat supply under different periods. Herein, based on the consideration of the energy efficiency of hydrogen, technologies and costs of its production, storage and transport were summarized in this work, together with the large-scale power supply by green hydrogen and ammonia. Comprehending the worldwide green hydrogen outlook would make benefits for China′s transition towards a future where hydrogen will be a major energy player.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 49980K]

  • Low load combustion characteristics of supercritical wall type tangentially fired boiler

    YOU Mo;CHEN Lei;SHANG Yong;GAO Aiguo;SU Sheng;XIANG Jun;North China Electric Power Research Institute Co.,Ltd.,State Grid Jibei Electric Power Co.,Ltd.;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

    With the increasing demand for new energy consumption and the national target of double carbon reduction, the stable combustion of boilers under low load conditions is of great significance for the deep and flexible peaking operation of thermal power generating units. The numerical simulation and experimental verification of the combustion characteristics of a 660 MW supercritical wall type tangentially combustion pulverized coal boiler under multiple operating conditions at low load were conducted. The impact of different combustion structures on the distribution characteristics of velocity, temperature, and oxygen concentration in the furnace were studied. By discretizing the combustion zone with a refined mesh, the accuracy of the simulation results is improved. The deviation between the numerical simulation results and the experimental results is small, indicating that the simulation results are reliable. The results show that a good circular flow field of coal powder can be established and the residence time can be increased by opening the bottom burners and adjusting the air distribution under 30% ultra-low load. Additionally, by properly increasing the distance between operating burners, the uniform distribution of heat load inside the furnace can be achieved, providing favorable conditions for the safe combustion of boiler under low load. The experimental results verify that the proposed combustion structure and operation strategy for the wall type tangentially fired boiler are reasonable, which can ensure stable combustion and meet various main steam parameters at 30% low load. The results can provide a basis and reference for the deep flexiblity operation of this type of ultra-supercritical unit.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 41083K]

  • Mechanistic study of nitrogen migration and transformation during sludge combustion process

    ZHAO Liang;WANG Xin;HUANG Baocheng;SUN Yu;XUE Yongming;ZHANG Hai;Shanghai Power Equipment Research Institute Co.,Ltd.;School of Mechanical and Power Engineering,Shanghai Jiao Tong University;Suzhou Wuzhong Comprehensive Energy Co.,Ltd.;

    Incineration is the most promising method of sludge treatment at present. However, a large amount of NO_x, SO_x and other polluting gases are generated during the burning process, which increases the load on the flue gas desulphurization and denitrification. There are many studies on the mechanism of nitrogen oxide emissions during the combustion of fuels such as coal and biomass, but studies on the combustion reactions and pollution emissions of elemental nitrogen from sludge are rarely carried out. Four common amino acid model compounds(glycine, glutamic acid, phenylalanine and tryptophan) in sludge were selected and chemical calculations were conducted by the density functional theory DFT/B3LYP method with 6-31G basis groups. The different bond lengths and Mulliken Boujou numbers of the amino acids were analyzed and compared, using relatively easy to break bonds as initiating bonds for pyrolysis. Weaker chemical bonds were selected for breaking at each step of the reaction pathway, gradually optimizing the calculations until all the nitric oxide(NO) was isolated. Three nitrogen migration reaction paths were designed for glycine, and five nitrogen migration reaction paths were selected for glutamic acid, two nitrogen migration reaction paths were selected for phenylalanine, and with total of seven reaction paths were considered for tryptophan. The products of each path contain NO, and the path with the least thermal absorption from the outside world is chosen as the best reaction path for amino acids by comparing the calculated thermodynamic parameters. The best nitrogen migration path for glycine requires 339.21 kJ/mol of heat absorption from outside, 304.92 kJ/mol of heat absorption from outside for glutamic acid, 324.27 kJ/mol of heat absorption from outside for phenylalanine, and the best reaction path for tryptophan nitrogen migration does not require heat absorption from outside. A multi-channel reaction network for the migration and transformation of nitrogen-containing components during sludge combustion is constructed based on the reaction pathways of four amino acids, and the migration and transformation reaction mechanism of typical nitrogen-containing compounds in sludge are clarified, providing necessary basic data and theoretical basis for sludge recycling and harmless utilization.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 37891K]

  • Influence mechanism of Na-K synergism on the evolution of NO_x in wet NO reduction

    SHAO Ranlei;HAN Shiwang;XUAN Chengbo;WANG Luyuan;ZHANG Xingyu;CHENG Xingxing;WANG Zhiqiang;School of Energy and Power Engineering,Qilu University of Technology(Shandong Academy of Sciences);School of Energy and Power Engineering,Shandong University;

    The flue gas absorption test was simulated using KMnO_4 and NaClO_2 as oxidants, and the effects of single alkaline absorption solutions and Na-K synergistic absorption solutions on the removal of NO_x from flue gas were investigated. Trace amounts of SO_3~(2-) ions were introduced during the process to further optimize the absorption efficiency. The results indicate that the performance of KOH alkaline solution is significantly higher than that of NaOH. The average absorption rate of KOH within 30 minutes of absorption is as high as 99.4%, while NaOH only achieves an average absorption rate of 86.9%. This difference can be attributed to the larger ionic radius of K~+ ions, which facilitates the dissociation of OH~- ions. When using 0.1 mol/L KMnO_4 as the oxidant and a two-component absorption solution(n(Na)∶n(K)=1∶2), the efficiency is higher and more stable, reaching 86% even after 30 minutes. It is due to the charge transfer effect of bimetallic ions, which results in the rapid rupture of the gas film when gas-phase reactants transfer to the liquid phase, reducing the diffusion time between the gas and liquid phases. This phenomenon has been thoroughly confirmed through density functional theory(DFT) simulation calculations. The average absorption rate is increased by 3% by introducing trace amounts of SO_3~(2-) ions into the absorption solution, demonstrating that SO_3~(2-) ions further promote the absorption and conversion of nitrate species.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 28598K]

  • Factors affecting release and capture of fluorine in coal during oxygen bomb combustion

    CHEN Sihan;SUI Yan;PI Zhongyuan;FANG Quanguo;National Coal Quality Inspection and Test Center;Coal science and Technology Research Institute Co.,Ltd.;State Key Laboratory of Coal Mining and Clean Utilization;

    In order to explore the release and capture laws of fluorine in coal during oxygen bomb combustion, the key factors that lead to the low determination results of high-ash and high-fluorine samples were revealed. Selecting coal samples with different ash and fluorine contents as the research object, the the influence of coal quality characteristics on the maximum flame temperature and the vapor/fluorine ratio at this temperature in the oxygen bomb was analyzed by using the thermodynamic state function method. The effect on the release and capture rate of fluorine was also analyzed. The results show that the maximum flame temperature and the vapor/fluorine ratio of the combustion environment is directly affected by the calorific value of the sample, and the effective heat obtained in the fluorine decomposition process is the key factor affecting the release and capture of fluorine. The release and capture rate of fluorine in high-ash and high-fluorine samples can be improved by adding benzoic acid to increase the calorific value and reduce the fluorine content of the sample. The fluorine release and capture rate of high-ash and high-fluorine samples can be increased from 52%-70% to 85%-100% by raising the theoretical maximum temperature to 2 800 K, achieving the full release and capture of fluorine. This study can provide a basis for expanding the scope of application of oxygen bomb combustion method to determine fluorine content, and also provide a basis for fluorine fixation in the application of high fluorine coal.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 11863K]

  • Review on treatment technologies of coal gasification wastewater

    ZHANG Botao;CHEN Guifeng;PENG Wanwang;China Coal Research Institute,China Coal Technology Engineering Group;China Coal Research Institute Co.,Ltd.;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;Beijing Key Laboratory of Coal Based Carbon Materials;

    Coal plays an important role in meeting global energy demand, and is also an important part of China′s primary energy structure. With the transformation of China′s economy to a high-quality development stage, the construction of ecological civilization has entered a critical period to promote the coordinated development of pollution reduction, carbon reduction and efficiency improvement, promote the comprehensive green transformation of economic and social development, and realize the improvement of the quality of the ecological environment. Clean and efficient use of coal has become the focus of national work. Coal gasification wastewater is the main waste stream generated by the low-temperature/medium-temperature gasification units. It is characterized by high content of phenol and ammonia, and contains various toxic and difficult-to-degrade organic and inorganic pollutants. It is a typical industrial wastewater with high concentration and biological resistance, which has obvious negative impacts on the environment. The reverse distribution of water resources and coal resources in China makes wastewater treatment and recycling not only a response to energy conservation and emission reduction policies but also an important measure for optimizing the allocation of water and coal resources. At present, various technologies have been applied to the treatment of coal gasification wastewater. After balancing factors such as treatment effect and economy, a consensus has been reached that the physical-chemical and biological treatment processes combining anaerobic and aerobic processes should be adopted. The technical route of this treatment is mainly composed of pretreatment, biological treatment and advanced treatment, and the treated wastewater can meet national sewage discharge standards. This article introduces the relevant technologies, treatment effectiveness, and advantages and disadvantages of the pretreatment, biological treatment, and advanced treatment of coal gasification wastewater. It analyzes the technical bottlenecks in production, and introduces other new treatment processes, such as freezing concentration, steam-water integration with near zero emission and microbial fuel cell methods. From the analysis of relevant literature, most of the research on coal gasification wastewater treatment still focuses on specific methods, while ignoring the comprehensive engineering system of the treatment process. It is necessary to focus on optimizing the integration of physical-chemical, advanced oxidation, and biological treatment technologies, improving treatment efficiency, reducing construction and operation costs, and strengthening the development of new processes. Better combination of the coal gasification wastewater treatment process and gasification process can improve the potential for water reuse and reduce energy consumption and pollutant production. Finally, it is important to pay attention to the resource utilization of coal gasification wastewater, explore its potential resource value, develop utilization methods, and truly tap into the resource potential of gasification wastewater, thus turning waste into treasure.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 18476K]

  • Influence of magnetic field on the medium stability of dense medium cyclone

    DU Pengtao;ZHAO Shiyong;XIAO Yuchen;YANG Zhenni;School of Chemistry and Chemical Engineering,Xi′an University of Science and Technology;

    The dense-medium suspension has heterogeneity, which can easily reduce the stability of the suspension under the centrifugal concentration, thereby directly affecting the sorting accuracy of the dense-medium cyclone. In order to reduce the concentration of the suspension and improve its stability, and according to the paramagnetism characteristic of the dense medium magnetite powder, the radial inward magnetic field force was introduced to adjust the distribution state of the dense medium particles in the cyclone. Herein, the motion laws of particles in magnetic composite fields were explained using the theoretical calculations, single factor experiment and Box-Behnken orthogonal experiment design with three factors and three levels. The influence of the feed pressure, the intensity of the excitation current and the number of coil turns on the distribution of the dense medium and the stability of the suspension was analyzed. The influence of various factors on the concentration efficiency E_(th) of the suspension was explored; the mathematical model and and its minimum values of response value E_(th) were provided. The results show that the introduction of radially inward magnetic field force into the centrifugal field makes the dense medium particles have a lower centrifugal sedimentation velocity and changes the distribution of the dense medium, which increases the density of the overflow and decreases the density of the underflow. With the increase of feed pressure, the concentration C_1, clarity C_2, stratification C_3 and concentration efficiency E_(th) of the suspension show a similar increasing trend, and a similar decreasing trend with the increase of the excitation current intensity and the number of turns of the coil. In the orthogonal interval, the concentration efficiency E_(th) is positively linearly correlated with the feed pressure, and negatively linearly correlated with the current intensity and the number of coil turns. The degree of influence is sorted in order of magnitude: feed pressure> coil turns> current intensity. Finally, the linear mathematical model minimum value of E_(th) is given. When the feed pressure is 0.03 MPa, the current intensity is 3 A, and the number of coil turns is 1 000 turns, the concentration efficiency E_(th) is 0.067. Compared with the concentration efficiency of 0.37 in the absence of a magnetic field, the stability of the suspension is increased by 81.89%.

    2023 10 v.29;No.158 [Abstract][OnlineView][HTML全文][Download 10504K]
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