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RSS2022 Vol. 9, No. 3
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2022, 9(3)
Abstract:
2022, 9(3): 1-8.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.001
Abstract:
Introduction The primary frequency modulation technology of thermal power units has been considered essential to ensure the power grid's safe and stable operation. Method The current primary frequency modulation technology, the auxiliary primary frequency modulation technology, the coupled frequency modulation control strategy, and the potential development direction of primary frequency modulation technology were reviewed. Result The results show that the primary frequency modulation technology for the unit mainly includes regulating valve pre-throttling, adjustable regenerative steam extraction frequency modulation, and condensate water throttling frequency modulation. Among them, the condensate water throttling frequency modulation technology should be the main mode. Auxiliary primary frequency modulation technology is mainly based on the fast-response rate characteristics of flywheel energy storage and battery to meet the unit input and output requirements. The focus and difficulty of coupled auxiliary frequency modulation technology are then analyzed. The system modeling and control strategy research based on frequency modulation technology can optimize the matching between unit parameters. Conclusion Thus, the application status of primary frequency modulation technology in recent years is compared, and it is considered that flywheel energy storage primary frequency modulation and sliding pressure operation optimization will be the key development direction.
2022, 9(3): 9-15.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.002
Abstract:
Introduction In order to adapt to the demand of the original thermal power units for new energy power consumption, improving its peak regulating capacity is one of the key factors. The heat storage system is an important way of "thermoelectric decoupling" of coal-fired thermal power units, so it has engineering reference value to evaluate its parameter matching. Method A method of coupling heat storage device was used to increase the depth peak regulation capacity of coal-fired unit. Combined with the power curve of heat load and electric load, the influence law of heat storage device parameters was systematically studied. Result The results show that with the regional load curve as a typical case, when the heat storage capacity and charging and releasing rate parameters of the heat storage tank increase, the heat load regulation capacity of the unit reaches 112.75 MW and 129 37 MW·min respectively, and the depth peak regulation parameter is about 110 MW. Besides, the heat storage capacity and the heat charging and discharge rate match, and the bottleneck factors will directly restrict the depth peak regulation performance of the system. Conclusion By integrating the boundary situation of heat storage and heat discharge, the role of the heat storage tank in the auxiliary peak regulation process is accurately demonstrated. Combined with the optimization design of its operation strategy, the parameter matching relationship of the heat storage auxiliary peak regulation system can be further analyzed to provide a reference for the parameter design of the coupled thermal storage system of thermal power units.
2022, 9(3): 16-28.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.003
Abstract:
Introduction With the establishment of China's "carbon peak and neutrality" goal and the urgent need to build a clean, low-carbon, safe, and efficient modern energy system, the proportion of renewable energy in the power grid will increase year by year. However, due to its randomness and intermittent characteristics, the contribution of renewable energy to power peak shaving is extremely limited. To improve its ability to absorb renewable energy, coal-fired power units with good peak-shaving potential are playing an important role in the basic regulation energy. Among them, the coal-fired boiler is the front-end core system of the coal-fired power unit, and its low (variable) load operation performance directly affects the overall peak-shaving capacity of the coal-fired power unit. Method Therefore, starting from the combustion stability, operating reliability, environmental protection, and economic requirements during low (variable) load operation of coal-fired boilers, this paper analyzed and summarized the current main research content and progress from four aspects, including combustion stability under low (variable) load operation, environmental protection and economy, adaptability and safety of main auxiliary equipment, and thermo-electrolytic coupling of the thermal power unit. Result On this basis, the research and development prospects of the technologies for deepening the peak shaving capacity of coal-fired boilers are put forward. Conclusion Through the analysis, it is concluded that to give full play to the first-mover advantage of coal-fired boilers in improving the power peak-shaving capacity, we should focus on the overall system of coal-fired boilers, comprehensively carry out monitoring and evaluation of the operation status of main auxiliary machinery, research on key influencing factors of combustion performance, conduct process intelligent optimization control and prediction. Thereby improving the overall performance of coal-fired boilers in low-load operation, rapid start-stop, and load-lifting.
2022, 9(3): 29-40.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.004
Abstract:
Introduction Low carbon emission technology of coal-fired power plant is an important strategy to alleviate energy crisis and environmental pollution in China. Method The low-carbon emission reduction path and potential development direction of low-carbon technology in fuel supply design stage and energy-saving operation and maintenance stage of current coal-fired power plants were reviewed. Result For the low-carbon technology in the design stage of power plant fuel supply, the ratio of biomass/ammonia and coal mixing should be optimized. A good ratio of biomass/ammonia mixing and burning should be fully burned in the furnace to reduce carbon emissions. Absorption technology, adsorption technology, and gas separation technology are common means of carbon particle capture in the energy-saving operation and maintenance stage of the power plant. At the same time, the important role of energy storage technology, deep peak regulating technology, and flexible DC power supply technology on the CO2 emission reduction path is expounded. Conclusion Finally, the development of low carbon technology in power plants is prospected. It is considered that the adoption of a comprehensive complementary and low carbon collaborative way, combined with the regulatory feedback control measures in the operation process of power plants. It will be an important development direction to promote the sustainable energy development of power plants.
2022, 9(3): 41-49.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.005
Abstract:
Introduction Integrated Gasification Combined Cycle (IGCC) power generation technology is a high-efficiency and low-carbon power generation technology. A waste heat boiler is one of the components of IGCC. This paper aims to study the off-design operating characteristics of waste heat boilers and improve the efficiency of integrated coal gasification combined cycle power generation technology. Method The working principle and heat and mass transfer principle of the waste heat boiler were mainly analyzed by MATLAB software to carry out programming calculations to explore the relationship between feed water temperature, feed water pressure, liquid-phase heat transfer coefficient, gas-phase heat transfer coefficient and heat absorption in waste heat boiler. Result The results show that when the liquid-phase heat transfer coefficient is in the range of 200～1 000 W/(m2·K) and the gas-phase heat transfer coefficient is in the range of 20～100 W/(m2·K), as if the feed water temperature increases from 30 ℃ to 100 ℃ or the feed water pressure increases, the heat absorption of the waste heat boiler decreases continuously. In case the feed water temperature is in the range of 30～100 ℃, when the liquid phase heat transfer coefficient increases from 200 W/(m2·K) to 1 000 W/(m2·K) or the gas phase heat transfer coefficient increases from 20 W/(m2·K) to 100 W/(m2·K), the heat absorption of the waste heat boiler increases continuously. Conclusion Under the condition that liquid-phase heat transfer coefficient and gas-phase heat transfer coefficient remain unchanged, the feed water temperature or pressure increases, and the heat absorption capacity of the waste heat boiler will decrease; While the feed water temperature and pressure remain unchanged, the liquid-phase heat transfer coefficient or gas-phase heat transfer coefficient increases, and the heat absorption capacity of the waste heat boiler will increase.
2022, 9(3): 50-61.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.006
Abstract:
Introduction With the gradual increase in the proportion of renewable energy generation in the power grid, the actual operating parameters of thermal power units deviate significantly from the design parameters, which will increase the amount of pollutants in the flue gas, and affect the regular operation of the flue gas treatment equipment, thus reducing the pollutant removal efficiency and the operating economy. Method The analysis of typical pollutant emission characteristics and corresponding control strategies during the peak shaving process of the unit was concerned. The current research results and progress of emission characteristics of NOx, sulfides, volatile organic compounds, heavy metals, and particulate matter were analyzed and summarized, including selective catalytic reduction technology, wet flue gas desulfurization technology, electrostatic precipitator technology, catalytic oxidation technology, gypsum absorption technology, adsorption control technology, etc. Result On this basis, the control technology and control strategy used in the current flexible peak shaving process is put forward, the economics of various pollutant control technologies are compared and analyzed, and the factors influencing the pollutant control performance and costs are obtained. Conclusion Under the actual demand for flexible peaking of coal-fired units, it is concluded that under the demand of flexible peak regulation, reasonable pollutant residence time, working temperature range, flow, and reaction process should be constructed based on the characteristics of various pollutants, and pollutant synergistic removal technology characterized by efficient, low-cost, adaptable and suitable for multi-pollutant removal should be developed. It is expected that this paper can provide some reference for the pollutant emission control measures in the flexible peak shaving process of thermal power units.
2022, 9(3): 62-71.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.007
Abstract:
Introduction With the increasing proportion of new energy power consumption, the development of energy systems with coal-fired units coupled with dual energy storage technology has received wide attention. Method Based on a systematic analysis method in terms of energy system composition, energy storage technology characteristics, applications, technical bottlenecks, etc., an operational control strategy study was carried out for coal-fired units coupled with dual energy storage technology under wind power and photovoltaic embedding to participate in power system peaking applications. Result It is found that a dual energy storage system coupled with the coal-fired unit can effectively solve the operation stability, efficient energy utilization, and technology economic issues of new energy systems through different structural compositions and optimization of operation strategies. However, this integration system has not reached the stage of large-scale commercial application. Conclusion The promotion and application of dual energy storage coupled with the coal-fired unit in new energy systems require continuous work on the strategic optimization of dual energy storage technology and the development of energy storage technology itself.
2022, 9(3): 72-79.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.008
Abstract:
Introduction In order to meet the demand for new energy power grid connection, the deep peak-shaving heat supply transformation of the original extraction and condensing cogeneration unit has become one of the important ways. Existing thermoelectric conversion devices, including thermoelectric pumps and electric boilers, provide a possible way to assist thermal power units in peak shaving. Method Taking a 350 MW extraction condensing unit as an example, an optimization model for peak shaving parameters assisted by a thermoelectric conversion device was established, and the influence of thermoelectric conversion equipment parameters on the deep peak shaving performance was analyzed. Secondly, the peak shaving depths of two typical thermoelectric conversion systems of electric heat pump and thermal storage electric boiler under different device capacities and different heat release rates were compared, respectively. Finally, the coal consumption rate and pollutant emission level of the 300 MW coal-fired unit were introduced, the energy-saving benefit of the system was pointed out, and the optimal parameters of the thermoelectric conversion device were given. Result The results show that when the thermal power of the electric heat pump is 100 MW and the heat release rate is also 100 MW, the peak shaving depth of the unit reaches the maximum value, which is about 73 MW. When the electric power of the regenerative electric boiler is 45 MW, and the heat release rate is 100 MW, the peak-shaving depth of the unit reaches the maximum value of 70.05 MW. The heat storage capacity of the regenerative electric boiler increases slightly within 24 h, and the net heat storage value is 967.5 kWh. Conclusion Power and heat release rate are important parameters to measure the peak shaving capacity of auxiliary units of thermoelectric conversion devices, and there must be a certain degree of matching between the two. Flexible matching of the type and parameters of the thermoelectric conversion device for different scenarios can greatly improve the peak shaving depth of the unit.
Research Progress of Coupled Waste Heat Utilization Technology for Coal-Fired Power Generating Units
2022, 9(3): 80-87.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.009
Abstract:
Introduction To realize the demand of further expanding the thermal power ratio of coal-fired power generating units, coupled waste heat utilization technology combined with the characteristics of the original units has become one of the effective ways. There are great differences in the adaptive characteristics and regulation capacity of the existing waste heat utilization technology. Method Several waste heat recovery and utilization methods were comprehensively reviewed and their principles, advantages and disadvantages were compared. Then the current focus of waste heat recovery technology was further reviewed by introducing common evaluation indicators. Result For waste heat recovery and utilization technology, there are mainly flue gas waste heat recovery, recycling water waste heat recovery, air source waste heat recovery, industrial waste gas recovery, and so on. The temperature ranges are 120～150 ℃, 15～35 ℃, 0～60 ℃, and below 300 ℃, respectively. The evaluation methods of coupled waste heat utilization technology mainly include performance evaluation, economic evaluation, and system parameter correlation evaluation, among which the evaluation parameters such as heat consumption and thermal efficiency are the main ones. Conclusion The development direction and relevant suggestions of waste heat recovery and utilization technology are pointed out. At present, coupled waste heat recovery and utilization technology is mainly used in the heat pump system. Under the demand for a higher thermal power ratio in the future, the low-pressure cylinder transformation technology using cold end waste heat heating will become a major development focus.
2022, 9(3): 88-93.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.010
Abstract:
Introduction In order to solve the prominent contradiction between electric load and heat load faced by coal-fired units and ensure the heat source supply of units in winter, it is necessary to study the heating transformation scheme to break its thermoelectric coupling relationship. Method This paper made a model analysis of two heating transformation modes of a type of 300 MW coal-fired unit, compared the heating capacity and other data before and after the unit transformation, and studied the thermoelectric decoupling heating transformation scheme in line with the production conditions. And the economic effect of heating transformation of cogeneration units was summarized. Conclusion Through the analysis of the heating model in this paper, it can be seen that the coal-fired unit only relies on steam extraction for heating, which is greatly restricted by the power load. The heating capacity at high power load is 2～3 times that at low power load. When the electric load is severely limited, its heating capacity cannot meet the heating demand in winter. But after retrofit of high back pressure and modification of the cylinder, the capacity of peak shaving increases, and the heating capacity increases to 3～4 times under the same electric load, which effectively solved the problem. Result The research result can be used as a reference for the heating transformation of the same type of coal-fired units in the future.
2022, 9(3): 94-101.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.011
Abstract:
Introduction With the development of artificial intelligence technology, combustion optimization schemes based on intelligent optimization algorithms emerge endlessly, such as GA, PSO, FPA, and so on. When developing the real-time combustion optimization system based on the intelligent power plant platform, it is necessary to weigh and choose the best technical scheme. Method Aiming at the problem that the weight assignment of the traditional TOPSIS method is highly subjective, an optimal weight fusion method was proposed to improve it, and the improved TOPSIS method was used to establish an evaluation system for the intelligent combustion optimization scheme of thermal power units. The six schemes of GA, AGA, PSO, FPA, CSO, and GSA were evaluated comprehensively from three aspects: optimization effect, optimization period, and reliability. Result The results show that through the double verification of the MCD index analysis system and the comparison with the traditional method, the weight of the improved TOPSIS method is consistent with the importance order of the MCD index, and compared with the traditional TOPSIS method, the pros and cons of each scheme can be distinguished better. The results are more in line with the requirements of the actual production process and have the advantages of strong objectivity and good accuracy. Conclusion The research can provide a valuable reference for the selection of combustion optimization schemes for thermal power units.
2022, 9(3): 102-110.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.012
Abstract:
Introduction The goal of "carbon peak and neutrality" will require profound changes in the existing energy structure. Improving the flexible adjustment capabilities of the original coal-fired cogeneration units is one of the essential elements in ensuring the safe grid connection of new energy power. Method This paper reviewed the flexible adjustment requirements of the coal-fired cogeneration system, the current status of potential energy storage applications, and the development direction of coupled energy storage technology. Result It is concluded that the deep "thermoelectric decoupling" is still the key to improving the coal-burning cogeneration system. Secondly, to meet the "source-charge" matching, energy storage technology will play an essential role in the coal-fired cogeneration system, among which energy storage technology with potential application mainly includes heat storage, electricity storage, and flywheel energy storage. Conclusion Finally, according to the application characteristics of coupled energy storage technology for coal-fired cogeneration units, the paper puts forward suggestions on the aging of energy storage performance, absorption of new energy, long-term change of thermal power load in the expansion area, economic analysis of initial investment, and payback period and relevant issues needing attention.
2022, 9(3): 111-118.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.013
Abstract:
Introduction To effectively improve the cycle efficiency, the Integrated Gasification Combined Cycle (IGCC) power generation system has received extensive attention due to its advantages of high thermal efficiency, low pollution, and flexible operation. The waste heat boiler and the steam turbine together constitute the bottom cycle of the system. Method Mainly combined with energy balance and thermodynamic calculation formula, using MATLAB for modeling operations, the effect of changes in steam flow, feed water temperature, superheated steam temperature, and reheat steam temperature on the steam turbine output power, thermal efficiency, and the total steam endothermic load was studied. At the same time, under the condition of steady-state operation, the working principle of the bottom cycle and the mass transfer and heat transfer process were analyzed. Result The results show that increasing the high-pressure steam flow and reducing the low-pressure steam flow can make the steam turbine output higher power under the premise of higher thermal efficiency. Under the optimized operating parameters, the endothermic load is reduced by 45.7 kW compared with the reference operating condition, and the thermal efficiency is increased from 23.82% to 26.92%. Conclusion The higher the temperature of high-pressure superheated steam and reheated steam, the higher the thermal efficiency of the steam turbine system, but the change range of heat absorption load and output power is very small. It can appropriately increase the temperature of high-pressure superheated steam and reheated steam, which is conducive to improving the thermal efficiency of the steam turbine.
2022, 9(3): 119-126.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.014
Abstract:
Introduction The proposal of the "carbon peak and neutrality" goal increases the necessity of new energy power embedding. To study the method to improve the flexibility of the unit, this paper introduces the flywheel energy storage technology and the related research of the coupled generator set in detail. Method The working principle, research status, and achievements of flywheel energy storage as well as application difficulties and measures were summarized, and the specific methods of studying the system modeling and operation strategy of flywheel energy storage were analyzed, and the principle and application characteristics of flywheel energy storage coupled with thermal power generation, wind power generation and solar power generation were analyzed emphatically. Result This paper shows that the research on flywheel energy storage systems in China has achieved relatively advanced results and formed a set of effective research methods, and some research has been done on the coupling of flywheel energy storage technology with multi-energy generator set. Conclusion In today's environment, flywheel energy storage technology coupled with multi-energy generators has become a research trend and focus, the summary of this paper provides a reference for the subsequent application of flywheel energy storage technology.
2022, 9(3): 127-133.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.015
Abstract:
Introduction Under the background of "carbon peak and neutrality," IGCC power generation system with CO2 pre-combustion capture technology is of great application potential. Method In this paper, the research status of the IGCC power generation system in recent years and the key directions of further research were summarized, the characteristics of existing research and related optimization suggestions were reviewed from three aspects: diversity of fuel, optimization design of system form, and software application of system simulation. Finally, the potential advantages of deep optimization of IGCC power generation system under the background of "carbon peak and neutrality" were emphatically introduced, and then the prospect of IGCC power generation system was discussed, especially the application prospect of multi-energy coupling and energy storage technology. Result The results show that the novel IGCC power generation system combining multi-energy coupling and energy storage technology has great development potential in the future. Conclusion This work provides some guidance for further study on the subsequent theoretical research of IGCC power generation system.
2022, 9(3): 134-139.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.016
Abstract:
Introduction The popularity of centralized steam supply has prompted many large coal-fired power plants to carry out a series of heating transformation. How to choose the heating transformation technology economically and reasonably is the focus of the industry and enterprises. Method In this paper, a 350 MW extraction-condensing unit in a power plant was used to implement medium-pressure steam heating renovation as an example, and the technical route of the renovation was determined through the comparison and selection of heating renovation technical schemes and hydraulic calculation and analysis. Result The analysis results show that the injection efficiency of the pressure matcher scheme is too low at low load due to the limitations of steam extraction parameters and operating conditions of the unit; The hydraulic calculation results show that under extreme conditions, the steam supply temperature of the unit is low, and the method of reducing heat loss by setting double steam supply header still cannot meet the requirements. Therefore, the method of temperature and pressure reducer and setting mixed steam is used for heating. Conclusion The technical scheme for heating transformation shall be determined after comparing the energy-saving effect, investment size, system complexity, and other factors according to the operating conditions of the unit and the characteristics of various technologies. In case of failure to meet the requirements of steam supply temperature, a double header system can be set. When the flow was low, only one header was used for the steam supply, which can reduce the heat dissipation loss by about 30%. If it still cannot meet the temperature requirements, the high-temperature steam mixing scheme can be adopted to improve the initial temperature of the steam supply to ensure the reliability and safety of the heating.
2022, 9(3): 140-147.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.017
Abstract:
Introduction With the vigorous development of renewable energy, clean and efficient utilization of low-rank coal not only improves resource utilization and economic value but also has great social significance. Low-rank coals such as lignite and weathered coal are the main sources of coal-based humic acid, humic acid is widely used because of its weak acidity, redox, and physiological activity, however, direct extraction is difficult to achieve efficient extraction of humic acid in coal, which usually requires oxidation pretreatment to improve the yield of humic acid. Method Firstly, the properties and applications of humic acid were introduced; then, the process, principle, and characteristics of traditional chemical oxidation were introduced, and the new low-rank coal electrochemical oxidation methods and advantages were summarized. Finally, the prospect of electro-chemical humic acid production from low-rank coal was prospected to provide a reference for the preparation of humic acid from low-rank coal. Result Electrochemical oxidation method has the advantages of mild conditions, easy control of reaction, high yield, and reduction of environmental pollution. It is a relatively promising method for the preparation of humic acid. Conclusion The efficient extraction of humic acid from low-rank coal by electrochemical oxidation driven by renewable power is one of the ways to achieve high value-added utilization of non-fuel in low-rank coal.
2022, 9(3): 148-152.
doi: 10.16516/j.gedi.issn2095-8676.2022.03.018
Abstract:
Introduction In order to solve the problems of poor stable combustion, unstable hydrodynamics, and too low SCR inlet flue gas temperature during the deep peak shaving process of power station boilers, it is imperative to reform the boiler to stabilize combustion. Method In this paper, taking the flexibility transformation of a 660 MW thermal power unit boiler as an example, two effective stable combustion transformation schemes were proposed, and the effects of the combustion and pulverizing system transformation on the furnace and NOx emissions were analyzed. Result Both retrofit schemes can improve the ultra-low load and stable combustion characteristics of the boiler. The retrofit of the combustion and pulverizing system has little impact on the furnace and NOx emissions and is comparable in terms of technical reliability, construction difficulty, and workload. In contrast, scheme 1 is slightly better. Conclusion The two transformation schemes have been theoretically verified and feasible, and can provide technical reference for flexible transformation of the same type of units.
