• Research progress on sludge/biomass chemical looping gasification and ash-moisture influence on gasification characteristics

    SUN Guozhen;AN Zewen;CHEN Yanming;LIANG Wenzheng;WANG Kun;CHANG Guozhang;WANG Cuiping;YUE Guangxi;Clean Energy Laboratory,College of Civil Engineering and Architecture,Shandong University of Science and Technology;Chemical Engineering Institute,Qingdao University of Science and Technology;Department of Energy and Power Engineering,Tsinghua University;

    The development and application of high-wet sludge/biomass resource technology are recently promoted in China under the backdrop of the dual carbon target. Chemical looping technology, as an emerging method for energy utilization, has been widely applied in the treatment of organic solid waste. The research status of the commonly used disposal technologies of high-wet sludge and agroforestry waste and chemical looping gasification were summarized. The research progress on the influence of ash and moisture on gasification characteristics during chemical looping gasification process was emphasized and summarized. The oxygen carrier, as a crucial component in chemical looping technology, has been achieved abundant research results. Iron-based oxygen carrier is one of the most concerned oxygen carriers among various oxygen carriers in chemical looping gasification because of their low cost and high oxygen-carrying capacity. However, its reaction activity is relatively low, which needs to be modified by doping Ni, Ca, K and other elements. The ash and moisture in the sludge have bidirectional effects on the gasification products and gasification efficiency, and even affect the NO_x emission. The oxygen carrier activity can be improveddue to the K and Ca oxides contained in sludge/biomass ash, but the increase of reaction rate will lead to local sintering of oxygen carrier, thereby reducing the oxygen carrier activity. The circulating ash is in full contact with the gas phase, which has a certain catalytic effect on gas reforming, thus improving the quality of syngas. Although the release of moisture from sludge/biomass absorbs a large amount of heat into vapor, a moderate amount of water vapor and oxygen carrier co-participate in the reaction of carbon conversion into syngas of rich H_2, which promotes the quality of hydrogen-rich gas. When water vapor is excessively supplied as a gasification agent, CO_2 production increases greatly and the syngas quality is reduced. Therefore, the positive effects of ash and moisture should be used to improve the gasification efficiency of high wet sludge and biomass in the process of chemical looping gasification, in which the control of circulating ash amount and moisture release rate is the key way.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1389K]

  • Research progress on direct-fired biomass power generation in coal-fired units: Gas-solid two-phase dynamic model for large non-spherical biomass particles

    WANG Jingliang;FANG Qingyan;YIN Chungen;MA Lun;MA Qilei;QIAO Yu;ZHANG Cheng;CHEN Gang;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;AAU Energy Aalborg University;East China Electric Power Test & Research Institute,China Datang Corporation Science and Technology General Research Institute Co.,Ltd.;

    Co-firing biomass power generation in power plants is one of the feasible and realistic ways to make full use of biomass energy resources with near-zero carbon emissions in the context of dual carbon targets. Nowadyas, there are few demonstration projects of co-firing biomass power generation in power plants. The technical maturity needs to be improved. There are problems such as fuel crushing and transportation, combustion organization, and boiler heating surface corrosion. Computational Fluid Dynamics(CFD) provides an effective research method for the optimal design and operation of energy and power plants. The research status of the gas-solid two-phase dynamic model of biomass particles was mainly reviewed. The existing problems were summarized, and the research suggestions were proposed. Biomass particles are large and exhibit irregular non-spherical. In the absence of mature technology and relevant experience in China, the accurate simulation of the motion trajectory of irregular and large for non-spherical biomass particles is the basis and key to accurately simulate the combustion process, which is also a difficulty in this field. However, there is no general model of gas-solid two-phase dynamics for large non-spherical biomass particles under dilute phase flow conditions. It is suggested to strengthen the basic theoretical research on the gas-solid two-phase dynamic model for efficient combustion of biomass particles. A new correlation of drag-lift coefficient and moment coefficient of various typical non-spherical particles is obtained by particle-resolved direct numerical simulation(DNS), which couples the translational and rotational motion of non-spherical particles. A general gas-solid two-phase dynamic model for large non-spherical biomass particles is constructed. After further experimental verification, it is applied to multiphase flow simulation in industry, which provides support for revealing the particle transport and thermal conversion characteristics in the coupling process of co-firing biomass power generation in power plants.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1815K]

  • Coal-biomass preheating in circulating fluidized bed for cement precalciner

    LI Pengpeng;REN Qiangqiang;LYU Qinggang;WANG Chao;ZHANG Chi;HAN Shaobo;School of Energy Power and Mechanieal Engineering,China North China Electric Power University;Institute of Engineering Thermophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;University of Science and Technology;

    In the dry cement production technology, fuel combustion and raw material decomposition in the calciner have important effects on cement quality and pollutant emission. Compared with the combustion of fuel directly injected into the calciner, the combustion performance of the fuel in the calciner can be improved and the emission of harmful gases can be reduced by the preheating treatment, and the fuel adaptability of the cement calciner can be increased. The preheating characteristics of coal and biomass mixed fuel preheated by circulating fluidized bed before entering the calciner was studied, that was, the influence of different factors on solid preheated fuel and gas. The results show that the increase of oxygen-carbon ratio(molar mass ratio of O_2 to C per unit time) will lead to more intense reaction and particle collision in preheating furnace, resulting in a decrease in the particle size of preheated fuel. At the same time, the ash content of coke produced by coupling preheating of coal and rice husk increases and other components decrease with the increase of oxygen-carbon ratio. The heating of external heat source can significantly increase the generation of effective combustion components of gas such as CO, CH_4 and H_2, and improve the conversion rate of each component in solid phase fuel.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1468K]

  • Characterization of NO_x and greenhouse gas emissions in a 15 MW biomass circulating fluidized bed

    SUN Jinyu;LIU Xiaowei;DAI Gaofeng;ZHAO Xiaojun;ZHENG Shijie;XUE Dongfa;RAHMAN Ur Zia;WANG Xuebin;Nandian Synthesis Energy Utilization Co.,Ltd.;School of Energy and Power Engineering,Xi′an Jiaotong University;China Nuclear Power Technology Research Institute Co.,Ltd.;

    Biomass is a "zero carbon" renewable energy source and is of great importance to China in achieving the goal of "peak carbon emission and achieve carbon neutrality". Although it is considered as a clean energy source, biomass combustion still emits NO_x(NO, N_2O) and greenhouse gases(CH_4, N_2O, CO_2). Therefore, it is necessary to investigate the NO_x and greenhouse gas emissions characteristics of direct biomass combustion. NO_x and greenhouse gas emissions from a 15 MW biomass circulating fluidized bed were measured, and the effects of bed pressure, primary and secondary air ratio, front and back wall secondary air ratio, waste wood blending ratio on NO_x and greenhouse gas emission characteristics were investigated. The combustion adjustment experiments show that the increase in bed pressure is beneficial to reduce NO and CO_2 emissions, but the reduction is small and causes an increase in the volume fraction of CO and CH_4, and a decrease in CO_2 volume fraction. With an increase in the primary to secondary air ratio, NO emissions are slightly reduced with a low CO and CH_4 emission, which means that the secondary air can be reduced appropriately to reduce NO emissions. When the ratio of secondary air from front and back walls is small or large, it is beneficial to reduce NO with a low CO and CH_4 emission. When the mixing ratio of waste wood with high content of N is increased from 20% to 50%, NO and CO_2 emissions first emissions increases and then decreases, while the CO and CH_4 show a reverse trend. This study shows that when low excess air co-efficient combustion method is employed to control NO_x emissions of the biomass circulating fluidized bed boiler, the concentration of CO and CH_4 emission is significantly increased, which reduces combustion efficiency. In addition, as a greenhouse gas emission, CH_4 must be considered. Combustion adjustments method is not sufficient enough to control NO_x, while high amount of NH_3 and HCN are emitted when some certain high nitrogen-containing fuels are burned with low oxygen combustion.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1367K]

  • Performance analysis of a biomass gasification power generation system integrated with coal-fired power plant and S-CO_2 cycle

    YU Zhiyong;WANG Xingang;WU Gaolei;ZHU Zimin;LU Di;CHEN Heng;State Grid Xinjiang Economic Research Institute;China National Grid Xinjiang Electric Power Co.,Ltd.;Electric Power Research Institute of State Grid Xinjiang Electric Power Co.,Ltd.;School of Energy,Power and Mechanical Engineering,North China Electric Power University;

    In order to fully utilize the biomass resources, a concept of biomass gasification system with coal-fired power plant and supercritical CO_2 cycle was presented. The biomass gasification utilization process of this system is highly coupled with coal-fired power plant and supercritical CO_2 cycle. After being cooled by carbon dioxide, the syngas is purified and fed to the gas turbine for combustion. The heat in the flue gas is gradually recovered through the gas turbine, supercritical CO_2 cycle and coal-fired power plant feedwater, enhancing the utilization and thus improving the efficiency. Taking a 660 MW coal-fired unit and a 16 t/h biomass gasification furnace as examples, thermodynamic and economic analysis was conducted through system simulation. The results show that the proposed coupled system introduces 46.66 MW of biomass energy and generates an additional 21.09 MW of power, and the efficiency of biomass-to-electric energy can reach up to 45.20% and the exergy efficiency can reach 41.67%, which fully utilizes the energy in the biomass. The net present value of the system is about 404.68 million yuan, and it only takes about 2.94 years to recover the investment, which shows the good economic performance of the system.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1656K]

  • Experiment on the co-burning characteristics of municipal sludge blending with coal(grinding)

    JIA Zixiu;WANG Zhichao;TU Jingyi;DU Zhihua;LI Yuhang;ZHOU Guangqin;ZHANG Xilai;YAO Wei;TAN Houzhang;Department of Thermal Engineering,School of Energy and Power Engineering,Xi′an Jiaotong University;Thermal Power Research Institute Co.,Ltd.;Shaanxi Engineering Research Center of Coal-fired Boiler Environmental Protection;

    In order to explore the impact of co-disposal of municipal sludge in coal-fired power stations on the existing equipment system and operation status of the unit, laboratory co-combustion test and on-site co-combustion test was carried out. The test results show that when dry sludge with 13% water content is mixed with 20% sludge in the laboratory, the ignition temperature of the mixed fuel is increased by 36 ℃ and the burnout rate is decreased by 1.5%. With the increase of sludge proportion, the grindability of fuel decreases and the tendency for slagging increases. In the field test, the sludge with 40% water content is mixed with 10% or less, the coal handling and pulverizing system operates normally, the boiler coking condition, steam and water parameters, air and smoke parameters are within the normal range; The maximum toxic equivalent value of dioxin in flue gas is 0.038 ng/m~3(11% O_2), the maximum values of HCL and HF are 2.50 and 0.23 mg/m~3.The mass concentration of smoke and dust is≤ 10 mg/m~3, the mass concentration of SO_2 is≤ 35 mg/m~3, the mass concentration of NO_x is≤ 50 mg/m~3, all of which can meet the national emission standards. The emission of cyanide ion, alkyl mercury, heavy metal and fluorine ion in fly ash, large slag and gypsum meet the requirements of national standards. The results shows that when the sludge blending ratio is 10% or less, the auxiliary equipment of the unit such as the coal handling system, the pulverizing system, the combustion system, the forced draft fan and the induced draft fan can adapt, and will not affect the quality and utilization of fly ash, large slag and gypsum, in addition the NO_x, SO_2, soot, dioxin, HCl and HF in the flue gas can be discharged up to standard. When further increasing the sludge blending ratio, it is still necessary to pay attention to the calculation of drying output and grinding output of the pulverizing system, and monitor the change of furnace flue gas temperature, slagging on the pipe wall and pollutant discharge, so as to reasonably and safely solve the sludge disposal problem.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1624K]

  • Engineering application of coal & sludge co-fired power generation on a 700 MW coal-fired boiler

    YE Ji;CHEN Chuangting;ZOU Xiangbo;RAO Mumin;WEI Shuai;MAO Tieying;QIN Shiwei;KUANG Cao;CHEN Gongda;HU Zhihui;CHEN Tianchi;JIANG Yuan;WANG Qun;Guangdong Energy Group Science and Technology Research Institute Co.,Ltd.;Guangdong Energy Group Co.,Ltd.;Guangdong Yudean Zhanjiang Biomass Power Co.,Ltd.;State Key Laboratory for Clean Energy Utilization,Institute for Thermal Power Engineering,Zhejiang University;

    In the past 10 years, domestic scholars and engineers have carried out a large number of academic research and engineering applications related to coal-fired coupled sludge power generation technology, but most of the research and application are carried out at more than 70% load of the unit, and there are few rele-vant studies on the carbon emission reduction effect of coal-fired coupled sludge power generation. In order to understand the full range of effects of coal-fired coupled sludge power generation technology on boilers under medium and low load conditions, field engineering tests of coal-fired coupled domestic sludge power generation under 50% load were carried out on a 700 MW quadrangle tangential pulverized coal boiler. The effects of coal-fired coupled sludge power generation on boiler thermal efficiency, pollutant emission, dioxin emission, heavy metal content of by-product and CO_2 emission were systematically studied. The results show that under 50% rated load, the boiler thermal efficiency decreases by 0.52% with 3% sludge and 1.03% with 6% sludge, compared with that without sludge. With the increase of sludge ratio, the carbon content of slag also increases correspondingly, which directly leads to the increase of heat loss in physical incomplete combustion. The incineration sludge has no significant effect on the discharge of dust, SO_2, NO_x and other conventional pollutants in coal-fired power plants, and the treatment capacity of the environmental protection facilities of the power plant units can fully ensure that the regulated pollutant discharge during the incineration sludge is in line with ultra-low emission standards. The higher the proportion of mixed sludge, the higher the removal rate of dioxins in flue gas purification plant, and the dioxins toxicity equivalent of all operating conditions are lower than 0.01 ng/m~3 stipulated in DB 31/1291—2021 "Emission Standard of Air Pollutants in coal-fired coupled Sludge Power Plant". Cr, Cu, Zn in fly ash, Cr, As, Ba, Ni, Zn in slag, and Cu in desulfurized gypsum are relatively sensitive to sludge blending ratio. Considering the use of by-products for soil improvement, the heavy metal content of by-products in power plant under sludge blending condition still meets relevant agricultural standards. According to theoretical calculation, 3% sludge will emit 0.15% more CO_2, 6% sludge will emit 0.3% more CO_2, the application of coupled sludge power generation technology needs to be optimized in sludge type, sludge pretreatment, combustion load, combustion adjustment and other aspects, in order to achieve the synergistic effect of pollution reduction and carbon reduction.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1595K]

  • Simulation of energy consumption in municipal sewage sludge hydrothermal coupled drying system

    FENG Yuheng;HAN Mengxi;YU Tianchi;JIN Zechen;HU Weijie;ZHANG Pengfei;LU Liye;WU Naixin;School of Mechanical and Energy Engineering,Tongji University;Neogene Intelligent Technology Co.,Ltd.,Shanghai;Shanghai Municipal Engineering Design Institute(Group) Co.,Ltd.;Huaneng Taicang;Shanghai Boiler Factory Co.,Ltd.;

    Drying and incineration technology has gradually become an important disposal method for sludge in the central urban areas of large and medium-sized cities in China. Hydrothermal carbonization can improve the dewatering property of sludge, thereby reducing the energy consumption of the system. However, there are few reports on the energy consumption analysis of hydrothermal and drying sludge pre-disposal process. In this article, the distribution of three-phase products and the organic components of hydrothermal liquid at hydrothermal temperatures from 200 ℃ to 260 ℃ were studied. Based on this, the energy-mass flow model of the hydrothermal and air-drying system was established, and the impact of different hydrothermal conditions on system energy consumption was analyzed. Finally, the energy consumption with air-drying system, and the anaerobic fermentation as well as the air drying system was compared. It is found that when the pressure inside the kettle is 8 MPa, the temperature of hydrothermal reaction is increased from 200 ℃ to 240 ℃.The energy consumption of the hydrothermal reactor decreases from 184 kJ/kg(sludge, the same below) to 161 kJ/kg, mainly due to a significant decrease in the proportions of aromatic hydrocarbons and nitrogen-containing heterocyclic rings in the hydrothermal liquid. When the temperature rises to 260 ℃, the energy consumption increases to 278 kJ/kg due to the significant increase in the vapor phase fraction and the recovery of aromatic hydrocarbon mass. It is found that the energy consumption of hydrothermal reaction at 240 ℃ decreases with the increase of pressure due to the influence of the vapor phase fraction. The decreasing trend slows down rapidly after the pressure increases to 4 MPa. The total energy consumption of the direct air drying system is 1 942 kJ/kg when the drying air temperature is 110 ℃. In the anaerobic digestion and drying system, due to the efficient heat recovery of biogas, the heat consumption is as low as 212 kJ/kg at 10 days′ digestion time, and the total energy consumption is 984 kJ/kg. As for the hydrothermal carbonization and drying system, due to the significant enhancement of the dewatering performance, the total energy consumption can be further reduced, and the energy consumption is 597 kJ/kg at a hydrothermal temperature of 240 ℃. This paper provides basic data and theoretical basis for the selection and optimization of pretreatment methods before sludge incineration independently or coupled combustion in coal-fired power stations.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1499K]

  • Influence of the added solid recovered fuel on the combustion characteristics of sewage sludge

    SUN Feifan;YUAN Shizhen;LU Rufei;CHEN Yingquan;QIAO Shixuan;HU Yanjun;WANG Shurong;Institute of Energy and Power Engineering,Zhejiang University of Technology;Jinhua Ningneng Thermal Power Co.,Ltd.;State Key Laboratory of Clean Energy Utilization,Zhejiang University;

    In order to understand the effects of Solid Recovered Fuel(SRF) blending on the thermal reaction characteristics and flue gas environmental characteristics of sludge incineration disposal. The thermogravimetric law, comprehensive burning characteristic index, slagging characteristic and NO_x emission characteristic of SRF and sludge mixed combustion process under different mixing ratio were analyzed by using thermal synthesis analyzer, SEM, XRD and GA-21plus flue gas analyzer. The results show that there are obvious multi-peak weight loss phenomena in the mixed firing process, mainly concentrated at 192.3-645.3 ℃. At 11% blending ratio, the maximum weight loss rate reaches 0.14%/min, which is significantly higher than that of sludge incineration alone. With the increase of SRF blending ratio, the ignition temperature and burnout temperature of the fuel decrease, and the full combustion stage shifts to the low temperature region. When the SRF mixing ratio is 11%, the stable combustion performance index and comprehensive combustion performance index are increased by 1.38 times and 1.17 times, respectively, which improves the ignition characteristics of sludge incineration alone. In addition, after SRF mixing, the melting temperature of fuel ash increases, the adhesion degree of ash decreases, and the agglomeration strength of particles decreases, thus weakening the slagging situation when the sludge is incinerated alone. However, the mixed combustion leads to an increase in NO_x emission in the flue gas.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1458K]

  • Optimization of starch kitchen waste smoldering disposal parameters and analysis of flue gas release characteristics

    YAN Chao;ZHANG Yu;HUANG Jingchun;XU Minghou;QIAO Yu;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

    Smoldering is a low-energy disposal technology for high-water organic solid waste, and self-sustaining smoldering experiments are carried out for leftover rice to provide technical parameter support for the industrial application of food waste smoldering disposal and the development of related tail gas purification devices. The effects of parameters such as abrasive ratio, ignition temperature and Darcy flow rate on the weight loss effect of leftover rice and the concentration of components of smoldering flue gas were experimentally studied. The results show that the oxidation reaction can only occur when the pyrolysis coke of starch based kitchens is above 500 ℃. In order to ensure that starchy kitchens can achieve self-sustaining smoldering disposal under low energy consumption conditions, it is necessary to ensure that the low calorific value of the smoldering system is greater than 0.72 MJ/kg. For mixed materials with a low calorific value of the system slightly below this value, self-sustaining smoldering can be achieved through combustion support measures such as increasing the ignition temperature and the Darcy flow rate. Due to the high volatile content characteristics of rice, the volatiles of the bottom material in the smoldering system will partially condense in the area of the low-temperature sand cover layer, so the sand cover layer that originally does not contain combustible organic matter will be violatively oxidized and exothermic at the end of smoldering disposal. Too high or too low abrasive ratio will be detrimental to the smoldering disposal of leftover rice. The soldering disposal effect of rice will be enhanced by increasing the ignition temperature and Darcy flow rate. For wet rice with a moisture content of 60%, the disposal effect is best when the Darcy flow rate is 4 cm/s and the ignition temperature is 350 ℃, the mass ratio of rice to quartz sand is 4. During the entire process of smoldering reaction, the concentrations of CO_2, CO and VOCs in flue gas show a trend of first increasing, then stabilizing, and then decreasing. The CO_2 concentration in the self-sustaining propagation section fluctuates between 6.75%-9.41%, CO changes in the range of 1.37%-2.51%, and VOCs changes between 109×10~(-6)-251×10~(-6) by adjusting the experimental parameters of smoldering. The higher the moisture content of wet rice is, the higher the minimum Darcy flow rate required to achieve self-sustaining smoldering is. The Darcy flow rate is increased to 8 cm/s, which can achieve up to 75% moisture content starch kitchen disposal.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1835K]

  • Numerical simulation of municipal domestic waste blending with combustion of high calorific value industrial solid waste in waste incineration furnace

    YANG Xu;YU Zhaosheng;HE Yurong;BIN Yanhui;MA Xiaoqian;School of Energy Science and Engineering,Harbin Institute of Technology;Huizhou Branch,Guangdong Institute of Special Equipment Inspection and Research;School of Electric Power,South China University of Technology;

    The efficient and stable operation of waste incinerators and the reduction of NO_x(nitrogen oxides) emissions are the currently challenges faced in the process of municipal solid waste(MSW) incineration. Taking a 500 t/d waste incinerator as an object, the effects of different air distribution schemes on the combustion process, flow field distribution and the optimal selective non-catalytic reduction(SNCR) process parameters were investigated for MSW mixed with high calorific value waste(ISW). The results show that the maximum temperature corresponding to the bed layer of different levels of primary air ratios remains basically unchanged. However, the maximum rate of volatilization analysis out increases, and the combustion of volatile and fixed carbon is advanced by increasing the air distribution in the first and second air chambers of the grate. A good secondary air injection angle can effectively organize the airflow in the furnace.Under condition 7, the phenomenon of high temperature sticking to the wall in the furnace is the lightest, and the distribution of flow lines is also more reasonable, so the secondary air angle setting in this working condition is the most reasonable. After SNCR reductant injection, NO_x emissions are significantly reduced, and the denitrification efficiency is highest when the injection speed is 50 m/s, up to 33.96%. Therefore, it is recommended to use suitable air distribution and secondary air injection angles and to combine with SNCR technology for NO_x reductionin actual operation.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1792K]

  • Process simulation and evaluation of the coal coupled with waste incineration power generation system

    ZHANG Lijuan;ZHANG Rui;LIU Dong;School of Energy and Power Engineering,Nanjing University of Science and Technology;

    Traditional waste incineration power plants have the disadvantages of low energy efficiency, large investment and high cost of environmental protection, making it difficult to operate in market and depending on financial subsidies for long-term survival. At the same time, there are large number of coal-fired generating units exist in China, which have large scale, high parameters, new age, and environmental protection facilities.Due to the limitations of the dual-carbon policy, a huge waste of fixed assets has been caused because of the inability to operate at full capacity for a long time. Therefore, the development of coal-fired coupled waste incineration power generation technology can make full use of the existing coal-fired units to cooperatively treat waste, improve the efficiency of waste power generation, reduce the cost of waste power generation, reduce the investment in engineering equipment, and reduce the carbon emissions of coal-fired units. The process of the coal power plant coupled with waste incineration system was simulated to compare with the coal-fired power generation system, and the power generation efficiency, economy and environmental performances as well as the carbon emission throughout the entire power production process were calculated and evaluated.The results show that the power generation efficiency of the coal-fired generating unit only decreases by 0.95% after the waste coupling transformation. The economic performance is better, the internal rate of return increases from 18.72% to 21.89%, and the investment return period decreases from 9.72 years to 9.12 years, while the environmental loss cost increases after coupling transformation. But the carbon emission of the power production in the system is reduced by 14.02 g/kWh(calculated by CO_2)after the renovation. The results show that the coal-fired coupled waste incineration power system is technically and economically feasible.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1313K]

  • Process simulation and exergy and techno-economic analysis of hydrogen production from kitchen waste by gasification integrated with torrefaction

    ZHAO Changxi;XIE Di;HUANG Jingchun;QIAO Yu;XU Minghou;State Key Laboratory of Coal Combustion and Low Carbon Utilization,Huazhong University of Science of Technology;

    Torrefaction is a promising pretreatment means for kitchen waste upgrading, which can significantly improve the quality of subsequent gasification syngas, but its economic feasibility is yet to be evaluated. Based on this, a process of hydrogen production from kitchen waste by steam gasification integrated with torrefaction(TG) was proposed in this study, compared to hydrogen production from food waste by steam direct gasification(DG), and thermodynamic and techno-economic assessments were fully conducted to assess the feasibility of the two processes. The effects of gasification temperature and steam to carbon ratio(η) on the hydrogen production capacity of two processes were investigated by using Aspen Plus. It is found that the hydrogen capacity of DG and TG is improved by increasing the temperature and η, and the optimal operating parameters are observed at temperature of 950 ℃ and η of 1.5-2.0. Based on the simulation results, a comprehensive evaluation of the hydrogen production process was conducted by analysing exergy efficiency and economic benefits to explore the feasibility of the process at a plant size of 55 000 wet tonnes/year with 55% water content. The energy and exergy results show that the introduction of torrefaction pretreatment results in an increase of 813.2 kW in total exergy loss, accounting for 10.5% of the overall process. The exergy efficiency of the DG is 56.7%. The exergy efficiency of TG is 2.8% higher than that of the DG. The economic analysis is suggested the total equipment cost is $5.12 million, the total annual production cost is $2.97 million and the minimum hydrogen selling price(M_(HSP)) is $2.94/kg, while MHSP of DG is 9.5% higher. Therefore, TG has more advantages than DG in terms of thermal efficiency and economic cost.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1585K]

  • Experiment of ammonia-coal co-firing in a drop tube furnace and the kinetic modeling of ammonia oxidation

    YAN Weidong;QIN Shitai;YANG Kai;LI Guangbin;LI Ming;WANG Xuebin;TAN Houzhang;ZHANG Jiaye;Beijing Guodian Electric Power Co.,Ltd.;National Energy Penglai Power Generation Co.,Ltd.;Sanhe Power Generation Co.,Ltd.;Hebei Coal-fired Power Station Pollution Prevention and Control Technology Innovation Center;Yantai Longyuan Power Technology Co.,Ltd.;School of Energy and Power Engineering,Xi′an Jiaotong University;

    At present, the development of advanced carbon emission reduction technologies and the realization of the dual-carbon goals have become the most urgent problems in the energy field. Carbon emissions from coal-fired power plants in China still account for a major proportion. Ammonia, as a zero-carbon fuel, has significant advantages in heating value, synthesis, transportation and other aspects. Co-firing ammonia in coal-fired boilers is one of the important ways to achieve large-scale utilization, however, the control of nitrogen oxide emissions during large-scale co-firing will be a major challenge in the future. In this paper, the co-firing experiment of ammonia with coal was carried out in a lab-scale furnace, and the effects of temperature(1 000-1 300 ℃), air/fuel ratio(0.65-1.50), and co-firing ratio(0-30%) on nitrogen oxide emissions were discussed. The results show that the lower combustion temperature and air/fuel ratio is essential to inhibit the conversion of ammonia to nitrogen oxides. Under the operating conditions of 1.5 air/fuel ratio and 20% co-firing ratio, the NO_x emissions reach to 780×10~(-6) and 1 870×10~(-6) at 1 200 and 1 300 ℃ respectively. With the increase of ammonia ratio, the NO_x emissionsincrease linearly, but the overall conversion of fuel nitrogen to NO decreases significantly. The calculations by detailed chemical reaction mechanisms(e.g. Glarborg 2018, Mendiara 2009, Konnov) show that the prediction results derived by Konnov mechanism are closer to the experimental results. The Konnov mechanism is further used to evaluate the influence of air/fuel ratio, temperature and other variables on the NO emissions by ammonia combustion. The results show that the temperature and nitrogen oxide emission concentrations increase with exponential rate, while the total NO_x emissions change abruptly when the air/fuel ratio increases from 1.0 to 1.1. A mixing factor is defined to study the effect of the mixing level of oxidant and ammonia on nitrogen oxide emissions, and it is found that prolonging the mixing distance of ammonia and oxidant can significantly reduce the intensity of nitrogen oxide emissions.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1360K]

  • Effect of ammonia injection location in the pulverized-coal flame zone on combustion and NO formation characteristics under large proportion of ammonia blending conditions

    XU Lianbing;CHEN Jing;WEI Shuzhou;YANG Kai;ZHANG Chaoqun;ZHANG Wenzhen;LIU Xin;WANG Xuebin;MA Lun;National Energy Group Shandong Electric Power Co.,Ltd.;GD Power Development Co.,Ltd.;Sanhe Power Generation Co.,Ltd.;Hebei Innovation Center for Coal-fired Power Station Pollution Control;Yantai Longyuan Power Technology Co.,Ltd.;School of Energy and Power Engineering,Xi′an Jiaotong University;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

    Co-firing zero-carbon fuel ammonia is a practical and feasible carbon reduction technology for coal-fired power generation. Taking a 40 MW_(th) pulverized-coal combustion test furnace as the research object, the combustion and NO generation characteristics were investigated numerically under the condition of firing the large proportion of ammonia and without adopting air stagingwhen pure ammonia and ammonia/air were injected into the furnace from different locations(flame-root zone, flame-middle zone and flame-tail zone) in the pulverized-coal flame zone. The results show that whether pure ammonia or ammonia/air mixed gas is injected into the furnace, the carbon content in fly ash increases slightly. Due to the relatively sufficient oxygen content in the main combustion region, the significant NO generation is observed and the NO_x concentration at the furnace outlet is higher than that of pure coal combustion. Under the pure ammonia injection method, as the ammonia injection location moves from the flame-root region to the flame-tail region, the carbon content in fly ash and the NO_x concentration at the furnace outlet gradually decreases. However, under the ammonia/air mixture injection method, as the ammonia injection location moves from the flame-root region to the flame-tail region, the carbon content in the fly ash and the NO_x concentration at the furnace outlet gradually increases. Considering the burnout and NO_x formation characteristics, it is recommended to feed pure ammonia into the furnace from the tail area of the coal powder flame, and the ammonia/air mixture is fed into the furnace from the flame-root region, which not only can effectively reduce the effect of co-firing ammonia on the burnout characteristics of pulverized-coa, but also inhibit the NO_x generation.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 2024K]

  • Modeling co-firing ammonia with coal in different air staging modes

    NIU Tao;ZHANG Wenzhen;WEI Shuzhou;ZHANG Chaoqun;LI Ming;CHU Wei;LIU Ping;MA Lun;WANG Xuebin;Yantai Longyuan Power Station Technology Co.,Ltd.;Sanhe Power Plant Ltd.;Hebei Innovation Center for Coal-fired Power Station Pollution Control;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;School of Energy and Power Engineering,Xi′an Jiaotong University;

    Recently, ammonia has garnered significant attentionaround the world as an effective zero-carbon fuel and hydrogen storage medium. To reduce carbon emissions in coal-fired power plants, the use of zero-carbon fuel blends shows great promise. Investigates the combustion behavior of ammonia coal co-firing under the deep-air staging mode. Specifically, the temperature field, component concentration field, and nitrogen oxide emission in the furnace at varying α coefficient conditions are investigated, while maintaining the total excess air coefficient at 1.2. The study analyzes four cases with α coefficients equal to 0.696, 0.840, 0.912, and 0.996 respectively. The temperature field reveals that as the α coefficient decreases, the ignition position of the first stage of pulverized coal combustion advances. However, the length of the high-temperature flame formed is shortened, and the temperature near the ammonia injection port is notably lower. When α =0.696, the pulverized coal flame and ammonia combustion flame are distinctly separate, but as α improves, the boundary between the two gradually becomes blurred. Decreasing the α coefficient forms a longer reduction zone upstream of ammonia fuel injection, leading to a lower oxygen concentration of ammonia fuel at the moment of injection, hence reducing the probability of ammonia oxidation path. However, as the α decreases, there is a corresponding decrease in burnout in the furnace, which includes CO emissions concentration, fly ash carbon content, and ammonia escape. However, the influence is very limited in this simulation. Statistical analysis of NO_x concentration in the furnace showed that NO_x emissions significantly decreased as α decreased. Furthermore, the highest H_2 concentration in the furnace reached 2% under α =0.696, led to a significant enhancement of ammonia decomposition reaction. Since the consumption reaction of ammonia depends on three global reactions, improved decomposition reaction can reduce the direct participation in oxidation for ammonia. Increased H_2 production also enhances the possibility of nitrogen oxide reduction, leading to further decreases in NO_x emissions. Ultimately, utilizing the air depth classification method can optimize the temperature and oxygen concentration within the ammonia combustion area, contributing to achieve the low NO_x emissions in the furnace.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1423K]

  • Effect of moisture contents on self-heating characteristics of corn straw fuel in power plant

    YAN Hongchi;CHEN Xinke;MA Lun;SU Xianqiang;FANG Qingyan;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

    In the process of biomass storage and transportation, there exists the phenomenon of self-heating caused by microbial growth and metabolism heat production, which may cause spontaneous combustion of biomass. Water content is an important factor affecting microbial growth, metabolism and heat production. In this paper, a 120 L self-heating insulation test chamber was designed and built. The effects of water content on self-heating characteristics of corn straw were studied in the range of 20%-95% water content. Temperature and oxygen consumption rate were used to characterize the degree of self-heating and microbial metabolic activity, respectively. The results show that the maximum temperature and peak heat production of corn straw in the process of self-heating increases firstly, and then decreases with the increase of moisture content. The maximum temperature is 41.1 ℃ under 50% moisture content, and the maximum peak heat production is 157 J/(s·m~3) under 80% moisture content. The peak heat production of corn straw is affected by moisture content. When the water content is lower than 35%, the difference of peak heat production is small. When the water content is between 35% and 80%, the peak heat production shows a linear relationship with the water content, and the average increase of peak heat production is 33.43 J/(s·m~3) when the water content increases by 15%. When the water content exceeds 80%, the peak heat production decreases.The specific growth rate of microorganisms is directly proportional to the oxygen consumption rate, and both of them increase firstly, and then decrease with the increase of water content. The oxygen consumption rate reaches the maximum value of 0.056%/min under 80% water content, indicating the strongest metabolic activity of microorganisms. The research results provide reference for analyzing the self-heating characteristics of corn straw and proposing the safe storage and transportation measures of biomass.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1720K]

  • Preparation of sulfur-doped needle coke-based porous carbon for robust sodium-ion storage

    XIAO Xue;LI Jianchun;MENG Xiangtong;QIU Jieshan;College of Chemical Engineering,Beijing University of Chemical Technology;

    The development of cheap, efficient and stable carbon anode materials for sodium ion batteries is one of the important research directions in the field of electrochemical energy storage. Sulfur doped needle coke based polyporous carbon(S-NC) was prepared by a two-step process of mechanical ball milling combined with sulfur doping using needle coke as carbon source and sublimed sulfur as sulfur source, and was applied to the negative electrode of sodium ion batteries. The results of SEM, TEM and XPS indicate that the sulfur doping strategy can effectively reduce the particle size of carbon materials, increase the layer spacing of carbon materials, and increase the defect density of carbon skeleton. The results of nitrogen adsorption and desorption test show that compared with undoped carbon, the pore volume of S-NC is significantly increased, and it is rich in mesoporous. The electrochemical test results show that the prepared sulfur doped carbon(S-NC-600) exhibits excellent sodium storage properties when the doping temperature is 600 ℃. When the current density is 0.05 A/g, the specific capacity of S-NC-600 is 487.3 mAh/g. At 2 A/g high current density, the specific capacity is 275.5 mAh/g, and after 1 000 cycles of charge and discharge, the capacity retention rate is 90.7%, showing good rate performance and cycle stability, which can provide theoretical support for the preparation of carbon anode for high efficiency sodium-ion batteries.

    2023 09 v.29;No.157 [Abstract][OnlineView][Download 1941K]