2024年09期目次

  • A review on solar methane reforming for hydrogen production

    WANG Bin;GUO Ke;SHAO Yu;SUN Mengzhu;HAO Yong;LIU Mingkai;School of Energy,Power and Mechanical Engineering,North China Electric Power University;Institute of Engineering Thermophysics,Chinese Academy of Sciences;Department of Thermal Science and Energy Engineering,University of Science and Technology of China;University of Chinese Academy of Sciences;

    Hydrogen energy is a zero-carbon, high-density energy carrier, predominantly derived from fossil fuels such as natural gas or coal. As the global push toward achieving "carbon peak and neutrality" goals intensifies and the transition to low-carbon energy accelerates, the importance of sustainable hydrogen energy is becoming increasingly evident. However, the mismatch between current hydrogen production technologies and the growing energy demand is becoming more pronounced. Single solar-driven hydrogen production technologies remain limited by factors such as high production costs, technological immaturity, and inadequate infrastructure, preventing them from replacing fossil fuel-based methods on a large scale in the near term. The highly endothermic nature of the methane reforming reaction enables solar-driven methane reforming to absorb solar thermal energy up to 23% of the higher heating value of methane, by which solar energy can also be stored and converted to chemical energy, increasing the proportion of solar energy in hydrogen energy while simultaneously reducing carbon emissions in hydrogen production. Therefore, solar-driven natural gas reforming technology for hydrogen production is expected to play a pivotal role in the near-to mid-term. However, the simple integration of traditional SMR with concentrating solar technology still requires reaction temperatures of 800 to 1 000 ℃ and high concentration ratios exceeding 1 000. These requirements result in large radiative and convective heat losses, and fail to address critical technical challenges, such as the complexity and high carbon emissions of traditional SMR system. Lowering the reaction temperature of methane reforming through product separation by Le Chatelier's principle has the potential to overcoming the bottleneck in integrating with solar concentrating technologies. Furthermore, the synergistic hydrogen production and decarbonization at the origin of methane conversion could effectively address the challenges of high temperature, high energy consumption and high carbon emissions associated with traditional methane reforming. The advancements in solar methane reforming technology for hydrogen production and decarbonization from both thermodynamic and kinetic perspectives were reviewed. The trends of development of conventional solar methane reforming from concentrating solar technologies, reforming reactors and hydrogen production systems were analyzed. The fundamental reasons underlying critical challenges of conventional solar methane reforming technologies were also analyzed, such as high reaction temperatures, high irreversible losses in solar concentration and high energy consumption. Furthermore, new principles and methods from the perspective of reaction process design was focused on that can simultaneously reduce reaction temperature, improve product selectivity, and promote the synergistic conversion of hydrogen and carbon constituents. Methane reforming with single-product separation of CO_2 or hydrogen using sorbent or membrane can reduce reaction temperatures to 500-600 ℃. A further reduction to 400 ℃ or below can be achieved by sequentially separating two or more target products, reaching near-complete methane conversion and H_2 & CO_2 product selectivity under isothermal and atmospheric pressure conditions with solar trough concentrators, significantly reducing reaction temperature and energy consumption for hydrogen production and decarbonization while greatly simplifying and consolidating the hydrogen production system with a high level of integration. Under the new circumstances of vigorously developing renewable energy and promoting low-carbon energy transition, innovations in thermodynamic approaches, process design, and hydrogen production methods offer the potential for traditional methane reforming to achieving deep integration with solar thermal technologies. Such integration is expected to open up broader prospects for breakthroughs in sustainable hydrogen technologies in the near-to mid-term.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 9047K]

  • Standard system construction for flexible coal-fired power generation

    HAN Hengda;LONG Yan;XU Jun;XU Kai;JIANG Long;WANG Yi;SU Sheng;HU Song;XIANG Jun;State Key Laboratory of Coal Combustion,School of Energy and Engineering Power,Huazhong University of Science and Technology;

    Enhancing the flexibility of coal-fired power generation is a crucial for promoting clean energy consumption, green-oriented transition of energy and energy security guarantee. The construction of a comprehensive standard system for the flexible coal-fired power generation is a key step for promoting flexible coal-fired power generation development. Based on the essence of flexible coal-fired power generation, the current reconstruction and construction of flexible coal-fired power generation face four main challenges were proposed, such as difficulties in breaking through on flexibility indicators, prominent safety issues under flexibility, a significant decline in economic indicators under flexibility, and difficulties in ensuring cleanliness under flexibility. In response to four key challenges, a preliminary framework for a comprehensive coal-fired power plant flexibility standard system has been established, taking into account goals, specialized categories, and functional sequences. This framework covers processes including general use, design, manufacturing, installation, testing, measurement, operation, and evaluation. Based on the current state of flexibility development in coal-fired power generation and related standards, it is proposed to focus on several key areas for standard development: terminology and evaluation of flexibility standards, safe operation and life assessment of flexible units, efficiency evaluation under flexible operation of coal-fired units, carbon dioxide detection and pollutant emission control, and online monitoring of coal-fired power generation units. The efficiency evaluation methods will particularly address non-steady-state and deep load-following abnormal conditions, with special emphasis on online monitoring technologies for fuel quality and coal flow, as well as the establishment of flexible control standards for fuel-burning-working fluid interactions. The proposed framework and suggestions can be served as revision and establishment references for the standards related to flexibility of coal-fired power generation.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 1567K]

  • Analysis of real furnace test and calculation of hydrodynamic power for low load deep peaking of 350 MW supercritical boiler

    SONG Yuanyuan;GUO Zerui;AN Ning;YANG Dong;State Key Laboratory of Multiphase Flow in Power Engineering,Xi′an Jiaotong University;

    The sustainable development of energy makes deep peaking a crucial part of thermal power generation technology. In order to analyze the flexibility modification capability of the boiler of supercritical coal-fired unit and the hydrodynamic safety characteristics of water wall system during deep peaking, for the structural characteristics of a 350 MW supercritical spiral coil boiler, the complex water wall system was divided into flow loops and pressure nodes based on the flow mesh system method, and a nonlinear calculation model for solving the hydrodynamic characteristics of a supercritical boiler was established by combining the three major conservation laws and the heat transfer equation. On the basis of the real furnace test, the actual heat absorption deviation distribution along the width of the furnace at 26.3% BMCR(92 MW) load was backpropagated, and the vapor temperature and pressure drop of the upper furnace exit calculated by the program were compared with the measured data of the real furnace to verify the reliability of the model. On the basis of the real furnace test study, the nodal pressure and loop mass flow rate distributions of the water wall, the trends of the outlet vapor temperature deviation and the wall temperature along the direction of the furnace height were studied and analyzed under 20% BMCR(70 MW) deep peaking load condition, and the calibration calculations were performed for the flow instability. Calculation results show that the supercritical spiral coil boiler in 20% BMCR deep peaking load operation, the total system pressure drop is 0.603 7 MPa, the maximum outlet steam temperature deviation of the upper hearth is 29.4 ℃, the maximum outer wall temperature is 381.1 ℃, and the maximum fin end temperature is 383.4 ℃, and the wall temperature and fin temperatures are all in the permissible temperature range of the material, which ensures safe and reliable hydrodynamics for 20% BMCR deep peaking load operation, and the flow stability is good.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 4846K]

  • Optimization of air distribution of high concentration pulverized coal pre-combustion strong stable combustion low nitrogen burner

    ZHOU Xu;ZHANG Hanlin;ZHANG Feng;TAN Houzhang;ZHENG Haiguo;LIU Yi;LIN Shanhu;WANG Xuebin;MOE Key Laboratory of Thermo-Fluid Science and Engineering,Xi′an Jiaotong University;Key Laboratory for Clean Combustion and Flue Gas Purification of Sichuan Province;Shandong Shunye pressure vessel Co.,Ltd;

    The low nitrogen combustion technology of pulverized coal pre-combustion can balance stable combustion and NO_x emission control, which has great application potential in the field of flexible peak shaving and stable combustion of coal-fired boilers. Based on the 5 MW combustion test rig, the operation performance of a high-concentration pulverized coal pre-combustion low-nitrogen burner with a small pre-combustion chamber developed by the authors′ team was studied. The effects of primary air rate, internal and external secondary air distribution and separate over-fire air(SOFA) on the combustion performance and pollutant emission of the burner were systematically studied by CFD numerical simulation. The combustion model was verified by the test results of the 5 MW combustion test rig. The maximum deviation between the actual temperature and the numerical calculation results is 44 ℃,and the error range is ±3.3%,which proves the accuracy of the selected combustion model. The results show that the primary air rate is the key factor affecting the backflow zone of the pre-combustion chamber, and too low or too high primary air rate will affect the combustion stability and nitrogen reduction ability respectively. Under the condition of 8.8% primary air rate, sufficient backflow can be guaranteed, which is conducive to the ignition and emission control of pulverized coal. Increasing the internal secondary air rate can entrain more high-temperature flue gas in the furnace, which is conducive to the burning of pulverized coal. However, the increase of the high-temperature oxidizing atmosphere area in the furnace will lead to the increase of pollutant emission. The internal secondary air rate of about 43.5% can both stabilize combustion and reduce nitrogen. Replacing the external secondary air with an appropriate proportion of SOFA can make the nitrogen-containing compounds in the combustion area more easily reduced, thus reducing emissions. At 23% SOFA rate, a significant nitrogen reduction effect was observed, with NO_x emissions of 72 mg/m~3(6% O_2),a reduction of about 67% compared to 0% SOFA rate.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 3806K]

  • Application of plasma ignition technology in 660 MW high moisture lignite unit

    LI Ming;ZOU Peng;LI Bingbing;CAI Wei;CHENG Zhongjie;LIU Xin;Yantai Longyuan Power Technology Co.,Ltd.;

    Plasma ignition technology has good flexibility in load variation, short ignition/start-up time, low emission, and high economic efficiency. It is widely used in the deep peak shaving transformation of coal-fired power units and is one of the main measures to achieve low load stable combustion in power plant boilers. In recent years, the promotion of medium speed coal mills in high moisture lignite units has provided convenient conditions for the application of high moisture lignite plasma oil-free ignition technology. However, traditional plasma ignition technology is mostly suitable for coal of high-quality such as bituminous coal. There are problems with insufficient ignition energy, the need for oil gun to assist ignition, and poor fuel economy when burning high moisture and low calorific value lignite. A bias concentration slit type multi-stage cylinder structure plasma ignition burner for pulverized coal was developed. Tests under different operating conditions using plasma oil-free ignition were conducted on a 660 MW lignite unit with a total moisture content of 35%-40% of the raw coal. The effects of coal quality and unit operating parameters on the oil-free ignition characteristics of high moisture lignite were analyzed. An improvement plan for the plasma burner was proposed based on the test results. A numerical simulation was conducted on the high moisture lignite plasma burner under the benchmark operating conditions. The effectiveness of the burner modification was compared and discussed. The ignition test results show that the new plasma ignition system can ignite high moisture lignite with a heat generation of 10 900-13 400 kJ/kg and achieve oil-free start-up of the unit. The burner has a small adaptability range to coal quality. Excessive ignition energy, small gap between the central and the secondary cylinder of the burner, and poor cooling effect is prone to overheating of the secondary cylinder, causing coke formation and burning damage. Putting the plasma generator into operation has little effect on NO_x emission when the units are under steady operation. The numerical simulation results show that the burner used in the ignition test burns prematurely due to the excessive concentration of plasma heat absorbed by the coal powder in the first stage combustion tube, resulting in overheating of wall of the combustion tube and coke formation on the inner wall. The central flame temperature inside the first and second stage combustion tubes of the burner significantly decreases after being improved. The flame temperature at the end of the third stage combustion tube tend to be consistent. The highest wall temperature of the burner is 376 ℃,which is about 74 ℃ lower than that before improvement. The improvement plan reduces the erosion of concentrated pulverized coal on the end face of the inlet of the first stage combustion cylinder. The amount of coal in the first stage combustion cylinder is increased and the ignition process is optimized. In short, the development and optimization of new plasma burners can achieve stable and efficient ignition of high moisture lignite units with a wide range of coal quality. It can provide technical support for the construction of the first high moisture lignite oil-free power plant in China.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 2232K]

  • 5 MW pilot test study of rapid peaking burner based on pre-gasification strong stable combustion of pulverized coal

    ZHANG Hanlin;ZHOU Xu;SHU Yixiang;ZHENG Haiguo;LIN Shanhu;LI Jie;LIU Shuchang;YAN Weijie;TAN Houzhang;WANG Xuebin;MOE Key Laboratory of Thermo-Fluid Science and Engineering,Xi′an Jiaotong University;Key Laboratory for Clean Combustion and Flue Gas Purification of Sichuan Province;School of Energy and Power Engineering, Nanjing University of Science and Technology;

    The strong stable combustion technology of pulverized coal pre-gasification can balance stable combustion and NO_x emission control. Based on this principle, a rapid peaking burner for flexible peaking of power plant boilers had been developed, and the operation performance under different loads, the minimum stable combustion load and rapid load variation capacity of the burner were studied on a 5 MW combustion test rig. The results showed that, after entering the small pre-gasification chamber attached to the burner, the pulverized coal would undergo gasification reaction and transform into preheated fuel composed of high temperature gas and hot carbon particles. Under low load, the preheated fuel would burn rapidly after entering the furnace, forming a high temperature zone at the root to ensure the steady combustion of the furnace. With the increase of load, the gasification reaction in the pre-gasification chamber was more complete, and reducing atmosphere was formed with the return flue gas to achieve effective nitrogen reduction. The NO_x emission at full load was 159 mg/m~3(6% O_2) without any auxiliary means, and the carbon content of fly ash was 3.4%, meaning combustion efficiency was 99.71%. The rapid peaking burner could still maintain the stable combustion of the furnace under the ultra-low load of 9%, and the outlet oxygen remains stable during the long-term continuous operation of more than one hour. In the range of 15% to 100% load, the rapid load reduction and load rise processes were completed in 8 min and 9 min, and the load ramp rates reached 10.63%/min and 9.44%/min respectively. During the process of load change, the combustion in the furnace remained stable, and the temperature distribution had a fast response to the load change, which verified the excellent performance of the burner in the process of rapid peak regulating.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 5313K]

  • Influence of flue gas recirculation on deep peak regulation operation characteristics of 350 MW CFB boiler

    WANG Jiaxing;PENG Jiansheng;LI Fan;HE Jianping;YANG Tianliang;DONG Yongsheng;WANG Shuai;Yantai Longyuan Power Technology Co.,Ltd.;School of Energy Science and Engineering,Harbin Institute of Technology;Shenhua Shendong Electric Power Shanxi Hequ Power Generation Co.,Ltd.;

    To solve the problems of fluidization safety and ultra-low NO_x emission of supercritical CFB boiler under ultra-low load, flue gas recirculation technology was introduced. Taking a supercritical 350 MW CFB boiler as the research object, a flue gas recirculation auxiliary peak-shaving system after semi-dry desulfurization was built. Based on the data of field operation, the effects of operating parameters such as the average bed temperature, separator inlet temperature, exhaust temperature, NO_x,CO mass concentration of outlet flue gas, combustible content of fly ash and bottom ash, steam-water parameter at 30%-60% load were studied under the flue gas recirculation. The results show that under the coordination of flue gas recirculation, the final emission of NO_x at 30%-60% load is less than 50 mg/m~3 after SNCR,the original NO_x emission is less than 50 mg/m~3 at 30% load; the bed temperature is reduced by 15-22 ℃,the boiler exit flue temperature increases 10-13 ℃,and the primary and reheat steam temperature is above 558 ℃. With the decrease of boiler load, the carbon content of fly ash and bottom slag increases, and the mass concentration of CO does not increase significantly. The NO_x is reduced about 15 mg/m~3 by SNCR arranged at secondary air; the minimum change rate of load rise/fall is 1.23% Pe; the boiler keeps dry operation above 30% load, the maximum deviation of water wall temperature is 55 ℃ at 30% load, the maximum deviation of overheated and reheated heating surfaces is 55 and 47 ℃ respectively, and no over-temperature appears.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 2266K]

  • Calculation and practice of near-zero depth peak regulation, heat storage and release in subcritical circulating fluidized bed unit

    YANG Fengling;ZHANG Pusen;ZHANG Yuanyuan;ZHAO Ming;JIA Yangjie;ZHANG Peihua;Institute of Resources and Environment Engineering,Shanxi University;State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources,Shanxi University;Shanxi Guojin Coal and Electricity Co.,Ltd.;

    With the rapid development of renewable energy, higher requirements are put forward for deep peak regulation of thermal power units. On the basis of subcritical circulating fluidized bed boiler(CFB) furnace fire pressure participating in near-zero depth peak regulation, a set of calculation method of near-zero depth peak regulation storage and release heat was established, which provided operation guidance for subsequent near-zero depth peak regulation. Based on the concrete analysis of each part of the boiler with heat storage capacity in the process of near-zero depth peak regulation of subcritical CFB unit, a set of calculation method of heat storage and release in the process of near-zero depth peak regulation of CFB was proposed, and this method was applied to the near-zero depth peak regulation operation practice of a 300 MW subcritical CFB unit in Shanxi Province. By using the calculation method, it is concluded that the total apparent heat storage of boiler is 415.5 GJ,and the apparent heat storage of casting layer, metal wall, bed material carrier, soda and flue gas are 205.6,140.4,32.7,11.1 and 36.8 GJ respectively. The total heat consumption of effective work done by steam turbine is 65.2 GJ,and the heat dissipation of boiler body is 6.1 GJ. The data show the downward trend of each heat storage part with the process of near-zero depth peak regulation. This method realizes the quantitative calculation of the heat storage and release of the subcritical circulating fluidized bed, guides the near-zero depth peak regulation time for the follow-up prediction, and studies the tightness and heat transfer characteristics of the boiler. it also provides data support for finding out how to obtain more heat storage to improve the heat storage efficiency and improve the performance of the boiler.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 2986K]

  • Prediction of NOx emissions from deep peaking circulating fluidized bed boilers based on a hybrid modelling approach

    ZHANG Pengxin;GAO Mingming;GUO Jiongnan;YU Haoyang;HUANG Zhong;ZHOU Tuo;State Key Laboratory of Alternate Electrical Power System With Renewable Energy Sources,North China Electric Power University;Department of Energy and Power Engineering,Tsinghua University;

    In response to the goal of Carbon peak Carbon neutral, China′s circulating fluidized bed boilers participate in deep peaking operation on a large scale, resulting in large fluctuation ranges of NO_x emission concentration in boilers, poor control effect, and difficulty in meeting the demand for ultra-low emission of pollutants, so it is important to accurately model and predict the NO_x emission concentration in deep peaking. Based on the instantaneous carbon model, the NO_x generation and reduction mechanism in the furnace was deeply analyzed, and the instantaneous carbon combustion model, O_2 dynamic balance model, CO soft measurement model, NO_x generation and reduction model were established to complete the calculation of the mechanism of the NO_x concentration at the entrance of the SNCR. The amount of coal feed, bed temperature, flue gas temperature and oxygen content, the first and second airflow, and the flow rate of the urea solution were selected as the input variables for the NO_x emission concentration, and the NO_xemission concentration was predicted by the SNCR inlet model. The SNCR inlet NO_x concentration was used as an extended input variable, and the data set was reconstructed by correlation analysis and delay compensation between all input variables and NO_x emission concentration. The reconstructed data set was trained and predicted by using long and short-term memory neural network, and whale optimization algorithm was used for the optimization of parameters of the long and short-term memory neural network to establish a NO_x emission concentration model, the mechanism-data hybrid prediction model, for deep peaking of circulating fluidized bed boilers. The simulation validation shows that the hybrid prediction model has good prediction performance and generalization ability under different working conditions, and is able to realize real-time prediction of NO_x emission concentration in circulating fluidized bed boilers at variable loads, and significantly improves all the error performance indexes compared with other prediction models, with an average absolute error δ_(MAE) up to 2.14 mg/m~3,an average relative percentage error δ_(MAPE) up to 5.68%,and a coefficient of determination R~2 up to 0.902 1. The hybrid prediction model can accurately predict the NO_x emission concentration under deep peaking in circulating fluidized bed boilers, which provides a reference for the design of the ultra-low emission intelligent control system of circulating fluidized bed boilers.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 1831K]

  • Power distribution strategy of energy storage system auxiliary secondary frequency regulation considering battery life

    WANG Sheng;YAN Han;LI Jian;ZHANG Yumeng;MA Hao;HAN Zhezhe;XU Chuanlong;State Key Laboratory of Low-carbon Smart Coal-fired Power Generation and Ultra-clean Emission,China Energy Science and Technology Research Institute Co.,Ltd.;National Engineering Research Center of Power Generation Control and Safety,School of Energy and Environment,Southeast University;School of Electric Power Engineering,Nanjing Institute of Technology;

    Secondary frequency regulation of thermal power units assisted by energy storage systems has the advantages of fast response speed and high tracking accuracy. However, improper power allocation can accelerate battery life degradation, resulting in increased operating cost and reduced economic benefit. Therefore, how to formulate a reasonable energy storage power allocation strategy to ensure frequency regulation performance while extending battery life and improving economic benefits has become a key issue that needs to be solved urgently. A mathematical model of energy storage lithium battery based on the second-order RC equivalent circuit was established firstly, and the limited memory least squares recursive algorithm to identify the model parameters was then employed. Subsequently, three power allocation strategies such as proportion, difference and frequency were simulated and analyzed based on the joint frequency regulation model of thermal storage. Finally, with the actual operational data from a 660 MW thermal power unit in Jiangsu, the effects of different strategies on system frequency regulation performance, battery life and economy were analyzed. The obtained results indicate that the proportion allocation strategy has the worst frequency regulation effect and accelerates the battery life decay. The difference allocation strategy performs well in frequency regulation performance but has limited effect on improving battery life. The frequency allocation strategy can effectively reduce the battery replacement frequency and thus improve the overall economic benefit. Generally, the frequency allocation strategy can not only improve the frequency regulation capability, but also maximize the battery life with optimized economic benefit, demonstrating significant application advantages in the secondary frequency regulation assisted by the energy storage systems.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 2530K]

  • Load response characteristics of 350 MW cogeneration CFB unit

    WANG Weihua;GAO Mingming;WANG Yongquan;ZHANG Shuaining;CHENG Yongqiang;State Key Laboratory of Renewable Energy Power System, North China Electric Power University;School of Control and Computer Engineering, North China Electric Power University;

    In recent years, the proportion of cogeneration units in coal-fired units has increased, and thermal power generation has gradually assumed the heavy responsibility of peak regulation, and the demand for flexibility has increased. Combined heat and power circulating fluidized bed(CFB) units can use boiler steam-water side and heat network heat storage to improve the rapid variable load capacity of the unit, so a quantitative calculation method for steam-water side heat storage and heat network heat storage of supercritical cogeneration CFB units was proposed. Taking a 350 MW cogeneration CFB unit as an example, the working fluid flow on the steam-water side of the unit and the steam extraction and circulating water of the heat network were analyzed. The heat storage coefficient C_(sw) and the heat network heat storage coefficient C_h were calculated under different load conditions(35%～90%) by combining the design parameters and historical operation data of the unit, and the load response characteristics of the unit and the sustainable time of heat storage utilization were further analyzed. The results show that with the increase of the load of the unit, the heat storage coefficient C_(sw) of the steam-water side increases, and the C_(sw) of the steam-water working fluid changes greatly in the high load stage of the unit, while the heat storage coefficient C_h of the heat network is almost unchanged. The sustainable time of heat storage utilization of the unit is directly proportional to the load of the unit and inversely proportional to the variable load rate of the unit. The sustainable time of heat storage utilization of heat network is greater than that of steam and water side, and the heat storage capacity of heat network almost does not change with random group load changes. At the variable load rate of 4%/min, the heat storage utilization of the heat network can last for about 285 s, while the heat storage utilization on the steam side can last for 161.5-249.7 s. The above calculation results can provide theoretical guidance for the deep peak regulation and rapid variable load operation of supercritical cogeneration CFB units.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 1505K]

  • Combustion modification of expanded coal adaptability in ultra-small section circle-fired boiler

    LIU Ping;ZHANG Wenzhen;CHU Wei;ZHOU Mo;Yantai Longyuan Power Technology Co.,Ltd;

    Ultra-small section circle lean coal boiler has problems such as serious slagging and high temperature corrosion. In order to adapt to the current coal market diversification and boiler flexibility operation and other needs, it is urgent to improve its adaptability to complex coal blending. Taking the 300 MW ultra-small section of a power plant as the research object, the coal adaptive combustion modification was carried out. Firstly, CFD numerical simulation was used to evaluate the combustion problems of the original combustion system of the boiler when mixed with bituminous coal, then the modification scheme of the combustion system was put forward accordingly: by increasing the burner distance to reduce the heat load of the burner area, reducing the imaginary circle to solve the flame brush wall, increasing the burn out air rate to achieve deep air classification and other measures, the coal type adaptability of the boiler could be expanded. Then CFD numerical simulation was used to determine the best performance parameters of the combustion modification scheme, and predict the combustion state of the boiler under 67% and 100% low ash bituminous coal after combustion modification. The effectiveness of the combustion modification was verified through the engineering test. The results show that the 300 MW ultra-small section circle-fired boiler can be mixed with 20% bituminous coal to adapt to burn 67%-100% low ash melting point bituminous coal, so the adaptability of coal species can be effectively enhanced. According to the official assessment and test, the efficiency of the boiler in the designed coal condition is improved by 2.25%,NO_x emission rate is reduced by 40%-48%,and there is no obvious slagging and high temperature corrosion problems in the furnace. The combustion modification scheme provides guidance for the adaptability of bituminous coal.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 8581K]

  • Predicting the electricity coal ratio using the wind coal ratio and water coal ratio and its application in coal-fired generating unit operation optimization

    GAO Fei;ZHANG Qiang;ZHEN Zhiguang;WANG Jian;MO Qingfeng;ZHOU Yuanke;WANG Zhi;YANG Hao;JING Zhuoran;ZHOU Huaichun;Shijiazhuang Liangcun Thermal Power Co.,Ltd.;Jiangsu Hanguang Intelligent Technology Co.,Ltd.;School of Low-carbon Energy and Power Engineering,China University of Mining and Technology;

    In the context of intelligent power generation, it is necessary to explore in-depth methods for analyzing and utilizing the operational data of coal-fired power generation units. The economic performance of unit operation is usually characterized by the coal consumption of power generation(power supply),which is essentially the ratio of fuel consumption to power generation. This article proposes to use the ratio of electricity to coal-the ratio of power generation to fuel to calculate the operating economy of a coal-fired boiler, forming a main conceptual system where the air coal ratio, water coal ratio, and electricity coal ratio are all measured based on unit fuel quantity. Contrary to the lower coal consumption and better economy, the higher the ratio of electricity to coal and the better the economy, indicating that the effective output generated by unit fuel consumption is the highest. Based on the actual operating data of a 600 MW coal-fired generating unit with a down-fired boiler, the electricity coal ratio, air coal ratio, and water coal ratio were calculated, and the air coal ratio and water coal ratio were used to predict(fit) the changes in the electricity coal ratio through a quadratic function, with good prediction results. The variation law of the quadratic function and the range of values for the current air coal ratio and water coal ratio of the unit can provide quantitative basis for optimizing and adjusting the air coal ratio and water coal ratio of the unit operation. The experimental results of the online monitoring of three-dimensional combustion in the furnace and the closed-loop optimization control system of the boiler indicate that the improvement direction of the air coal ratio and water coal ratio obtained from the prediction model based on this method is consistent with the changes in the actual parameters of the optimized operation. The increase in the electricity coal ratio of the unit before and after the experiment reached 2.42%,achieving practical results in improving the economic efficiency of the unit operation, and proving the practicality of the analysis method in this paper.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 3678K]

  • Optimization control of pulverized coal mill outlet air temperature based on anti disturbance Smith predictive compensation

    CHEN Gang;YIN Ruilin;FAN Changhao;HUA Shan;SUN Li;State Key Laboratory of Low-carbon Smart Coal-fired Power Generation and Ultra-clean Emission,China Energy Science and Technology Research Institute Co.,Ltd.;Guoneng Nanjing Electric Power Test and Research Limited;School of Energy and Environment,Southeast University;

    Towards the goals of carbon peaking and carbon neutrality, as a thermal power unit with high energy consumption and high emission, its combustion performance directly affects the power generation efficiency and carbon emission. Optimal control of boiler combustion is important for operation optimization and flexible peak shifting. The outlet air powder temperature control of the coal mill in a power station boiler is subject to significant delays and multiple disturbances, which have a profound impact on the safety and stable operation of thermal power units. This paper proposed a feedback link in the compensation loop based on the Smith prognostic controller to enhance the anti-interference capabilities and performance of the air powder temperature control of the coal mill. The first-order inertia pure hysteresis model was obtained by Taylor series expansion and the method of coefficients to be determined to obtain the model approximation conversion parameters. The anti-disturbance Smith prediction compensation controller was then designed. A comparison with the single-loop PID control experiment reveals that the Smith prediction compensation control algorithm can effectively compensate for the pure delay lag link of the control object. The overshoot of the unit step response is reduced by 36.5% and regulation time is reduced by 65.8%. In comparison to the classical Smith prediction compensation control algorithm, the anti-disturbance Smith prediction compensation control algorithm demonstrates enhanced anti-disturbance performance and notable improvements in the dynamic characteristics of the control object. The overshoot of the unit step response is reduced by 44.7%,and the regulation time is shortened by 15.7%. At the same time, a reduction in the maximum deviation of the perturbation and the convergence time is achieved. The method of this paper was applied to a 660 MW supercritical primary reheat thermal power unit to realize the smooth tracking of the actual value of the air powder temperature at the outlet of the coal mill to the set value. The effectiveness of this paper′s method was further verified.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 2799K]

  • Development and application of an intelligent control system for wall temperature of high-temperature heating surfaces

    LIU Yi;ZHANG Xiuchang;CHEN Hong;ZHANG Zhongcai;RAN Shenming;ZHOU Xu;Clean Combustion and Flue Gas Purification Key Laboratory of Sichuan Province;Dongfang Boiler Co.,Ltd.,Dongfang Electric Group Corporation;

    Large capacity and high parameter opposite firing boilers are often affected by uneven wall temperature distribution on high-temperature heating surfaces, which affects their operational safety and economy. To solve this problem, it is usually necessary to carry out optimization of the pulverization system or over-fire air. However, due to the variation of wall temperature distribution with boiler operating conditions, the conclusion of a certain optimization cannot adapt to all operating conditions. Based on the principle of wall temperature regulation, an intelligent control strategy for over-fire air was designed, and the inlet structure of the over-fire air device was optimized and equipped with an electric actuator. A high-temperature heating surface wall temperature intelligent control system was developed, aiming to achieve automation and intelligence of over-fire optimization. Experimental research was conducted on a 1 000 MW unit for the intelligent control system. The wall temperature distribution at the outlet of the high-temperature superheater and the variation trend of the deviation between the outlet steam temperature and the highest wall temperature of the high-temperature superheater and screen superheater were compared under different loads before and after the system was put into use. The average deviation between the outlet steam temperature and the highest wall temperature of the high-temperature superheater and screen superheater in different load stages was statistically analyzed. The results show that under different loads, the system can automatically adjust the opening and swing angle of each over-fire air based on the real-time wall temperature distribution of the heating surface, so that the wall temperature distribution of the heating surface along the furnace width direction tends to be average. Under different loads, the system can significantly reduce wall temperature deviation. The wall temperature deviation at the outlet of the screen superheater is reduced from 50 ℃ to 20-30 ℃,and the wall temperature deviation at the outlet of the high-temperature superheater is reduced from 20 ℃ to 12 ℃. The system can significantly reduce the wall temperature deviation that increases due to load changes. The system can leveling O_2 concentration while leveling wall temperature.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 4019K]

  • Mechanism of enhanced SO2 and NO adsorption of CaO by red mud doping

    CHEN Yanming;LI Jialu;YANG Meiling;WANG Cuiping;Clean Energy Laboratory,College of Civil Engineering and Architecture,Shandong University of Science and Technology;

    The rich iron oxide in red mud possesses catalytic properties, and blending a certain proportion of red mud can be used to modify Ca-based desulfurization and denitrification adsorbents. To explore the mechanism by which red mud doping enhances the desulfurization and denitrification performance of calcium-based adsorbents, red mud/CaO adsorbents with varying doping ratios were prepared using the extrusion molding method. Utilizing a fixed-bed reactor system to simulate actual flue gas conditions, adsorption performance and DFT simulation studies were conducted. Based on density functional theory, CaO(001) surface models and Fe-CaO(001) surface models were constructed, and the impact of red mud doping on the adsorption performance of CaO for SO_2 and NO was revealed through calculations and analyses at the microscopic atomic level. The experimental results show that when the addition of red mud is 5%,the red mud/CaO adsorbent significantly extended the efficient adsorption time for SO_2 and markedly improve the adsorption efficiency for NO,increasing from 62.5% to 84.0%,confirming the effectiveness of red mud doping in enhancing adsorbent performance. The simulation calculation results indicate that red mud doping reduced the adsorption energy of SO_2 and NO from-1.181 eV to-2.247 eV and from-0.601 eV to-0.977 eV,respectively. Furthermore, after doping with red mud, the interactions between Fe atoms, O atoms, and S atoms(or N atoms) produces three atomic orbital resonance peaks with high state density, indicating that red mud doping enhances the stability of the CaO structure and intensifies the interactions between Fe and O atoms, thereby increasing the reactivity of O atoms. Consequently, red mud doping improves the chemical adsorption performance of CaO for SO_2 and NO.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 3439K]

  • Gasification of synthetic waste in circulating fluidized bed

    HE Shouqi;LIU Zhicheng;WANG Xiaofang;CAI Jun;Datong Institute of Coal Clean and Efficient Utilization;Shanxi Key Laboratory of Coal Flexible Combustion and Thermal Conversion;Institute of Engineering Thermophilic,Chinese Academy of Sciences;Shanxi Engineering Research Center of Coal Clean,Efficient Combustion and Gasification;School of Engineering Science,University of Chinese Academy of Sciences;

    To provide basic data for the development of industrial circulating fluidized bed(CFB) synthetic waste gasification technology, the effect of excess air coefficient and O_2 volume fraction on the gasification characteristics of synthetic waste were studied in a pilot-scale CFB gasifier. The synthetic waste used in the experiment is a material made of single-component waste, which consists of paper, fabric, sawdust, ash and water, respectively, according to the mass fraction of 60%,10%,10%,10% and 10%. The problem of poor feeding of block material in the pilot test was solved by using synthetic waste and boiler bottom slag alternately. The gasification temperature increased from 850 ℃ to 950 ℃ when the excess air coefficient increased from 0.31 to 0.50. The calorific value of the generated gas is 3 976-2 590 kJ/m~3. CO yields increases, H_2 yields increases first and then decreases, and CH_4 yields decreases.The gas production rate is 2.28-3.08 m~3/kg, the cold gas efficiency is 42.97%-51.01%,and the carbon conversion rate is 83.11%-92.45%. As O_2 concentration increased from 30% to 50% at around 900 ℃,the water-gas shift reaction was enhanced. The overall yields of CO、H_2 and CH_4 improves and calorific value of the generated gas improves(5 274-7 294 kJ/m~3). The gas production rate is 1.37-1.93 m~3/kg, the carbon conversion rate is 83.32%-81.11%,and th e cold gas efficiency is 55.39%-53.77%.The steady operation of synthetic waste gasification is realized in a pilot-scale CFB gasifier for 108 hours. The temperature at the bottom of gasifier is relatively low and the temperature distribution from the bottom of gasifier to the top is relatively uniform. The temperature difference within 19.7 ℃ indicates that stable material circulation inside the pilot-scale CFB.

    2024 09 v.30;No.169 [Abstract][OnlineView][Download 1669K]
    • 下载本期数据


Clean Coal Technology            京ICP备05086979号-19

Website  Copyright © 2019 Clean Coal Technology 
Coal Tower, Hepingli, Chaoyang District, Beijing, China. 100013
Tel:  86-10-87986452 / 010-87986451           E-mail:  jjmjs@263.net