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[Objective]The clean and efficient utilization of coal resources is an essential requirement for constructingChina's new energy system. As an important component of clean coal technology, coal water slurry holds significantadvantages. Numerical simulation studies have been conducted on the combustion characteristics of ultra-fine coalwater slurry. [Methods] A three-dimensional model of the test platform was established, incorporating turbulence,radiation, combustion, and discrete phase models. The study analyzes how changes in operational parameters such asfuel concentration, particle size, atomization angle, total air volume, and the ratio of primary to secondary air affect thetemperature and velocity fields of the test platform.[Results] The results indicate that an increase in fuel concentrationraises the furnace temperature and accelerates combustion, leading to an earlier ignition point and shorter flames.changes in particle size have minimal impact on combustion. An increase in atomization angle significantly consolidatesthe high-temperature zones, showing a dispersal trend; an increase in total air volume gradually expands the ignitionrange of the flame and delays the ignition point. An increase in the ratio of primary to secondary air significantly skews the direction of the flame within the furnace. Thus, it is demonstrated that increasing fuel concentration and total air volume significantly enhances combustion efficiency, while appropriate adjustments to the atomization angle and air ratio help optimize the stability and efficiency of the combustion process. The numerical simulation has confirmed that the optimal combustion conditions should be selected with a fuel concentration of 50%, a fuel particle size of 30 μm, a atomization angle of 30°, a total air flow rate of 0.316 kg/s, and a primary-to-secondary air ratio of 3: 7. [Conclusion] These findings are significant for enhancing combustion efficiency and advancing the industrial application of ultra-fine coal water slurry.
[Objective] During the operation of lithium-ion energy storage batteries, a large amount of heat is generated,and high temperatures can lead to thermal runaway, affecting battery safety. The thermal management system is a keyfactor affecting the stability and efficiency of lithium-ion energy storage batteries. [Methods] Using numerical simulationmethods, the heat transfer characteristics of parallel air-cooled and liquid-cooled battery modules are quantitativelycompared and discussed, including heat transfer performance, flow resistance performance, overall flow heat transferperformance, and the influence of ambient temperature. [Results] The results show that when considering themaximum temperature and maximum temperature difference of the battery module, there is a threshold for thetemperature difference between the inlet and outlet of the cooling medium in the selection between air-cooled and liquid-cooled methods. The overall temperature uniformity of the liquid-cooled method is better than that of air-cooled, with atemperature difference of only 0.5 ℃ between each cell, while air-cooled shows 6.1 ℃. The heat transfer performance ofthe liquid-cooled method is better than that of air-cooled, while the flow resistance performance of the liquid-cooledmethod is inferior to that of air-cooled. However, overall, the comprehensive flow heat transfer performance of the liquid-cooled method is better than that of air-cooled, and the performance advantage gradually increases with the increase incooling medium flow rate. In the environment temperature range of 0 ℃ to 30 ℃, the liquid-cooled method has astronger ability to adapt to environmental temperature changes than air-cooled, with its heat transfer performance beingless affected by environmental temperature, resulting in a maximum temperature increase of only 1.1 ℃. [Conclusion] Theresearch methods and results described in this paper can provide references for related research, which is conducive to thefurther optimization of energy storage cooling methods.
[Objective] In order to study the characteristics of combustion instability and hydrodynamic changes caused by coal-fired boilers participating in deep peak shaving when the boiler is in a low-load state, and to improve the safety of boiler operation, [Methods] In this paper, a 670 MW supercritical boiler is taken as the research object. The internal combustion condition of the boiler is numerically simulated. At the same time, combined with the hydrodynamic characteristics calculation based on the component pressure method, the hydrodynamic characteristics of the water wall of the boiler under the maximum continuous evaporation condition of the 100% boiler and the low-load 40% heat consumption rate acceptance condition are analyzed. [Results] The results show that the mass flow rate distribution trend of each loop of the vertical water wall in the upper part of the boiler under the two working conditions is similar, and both show negative flow response characteristics. Under the condition of maximum continuous evaporation of 100% boiler, the maximum temperature of each loop of vertical water wall is 392.75 ℃, the maximum temperature difference is 8.75 ℃, the deviation of steam temperature is not large, and the operation of water wall is safe. Under the condition of low load 40% heat rate acceptance, the working medium at the outlet of the water wall is in the two-phase region, and the temperature of each loop is 330.55 ℃ under the corresponding pressure. There is no over-temperature phenomenon, and the water wall can operate safely. [Conclusion] According to the characteristics of negative flow conditions, it is suggested to adopt more refined flow control mode or optimize the layout of boiler water wall pipes. For the case of small mass flow rate of the back wall, special attention should be paid to the cooling effect of the back wall during operation.
[Objective] In order to accurately simulate the wear of the heating surface of the low-temperature reheaterand the economizer at the tail of the coal-fired boiler, prolong the life of the boiler, improve the level of safe operation ofthe boiler, [Methods] in this paper, a supercritical boiler of a 600 MW unit is taken as the research object, and a one-waycoupling of the thermal combustion simulation of the boiler body and the wear simulation of the tail heating surface isproposed. The former is used as the calculation boundary condition of the latter, aiming to simulate a new numericalcalculation method for the wear of the heating surface at the tail of the boiler. [Results] The results showed that theaverage wear rate of the low-temperature reheater was 3.05×10~(-8) kg/(m~2·s), while the local maximum wear rate was1.54×10~(-6) kg/(m~2·s). The wear rate of the economizer is higher, with an average value of 6.65×10~(-8) kg/(m~2·s) and a localmaximum wear rate of 3.93×10~(-6) kg/(m~2·s). The windward surface wear of the first row of low temperature reheater andeconomizer is more serious and evenly distributed. The wear of the second to fourth rows of tubes is the slightest. Afterthe fifth row, the irregular wear of the side of the tube is distributed in a point shape, and the local wear rate exceeds thefirst row, mainly cutting wear. When the boiler load increases, the flue gas velocity increases, and the wear rate of theheating surface increases exponentially. When the load is reduced to 50%, the wear rate is only about 1/10 of that at fullload. When the ash content of coal increases from 10% to 20%, the wear rate increases linearly, but when the ashcontent further increases, the rate of increase in wear rate slows down. The thicker the pulverized coal particles, thelarger the particle size of fly ash produced by combustion, and the greater the impact wear on the pipe wall.[Conclusion] It is recommended to focus on the protection of the first row of heat exchange tubes on the heatingsurface of the boiler tail. When the coal ash content is high, the long-term high load operation of the boiler should beavoided, and the fineness of the pulverized coal should be appropriately increased.
[Objective] Ammonia-coal co-firing is of great significance in promoting the clean and low-carbon transformation of energy structure. To study the influence of ammonia co-firing ratio on combustion characteristics, [Methods] a thermal calculation model of a 300 MW coal-fired boiler was set up based on the energy balance method. The changes in fuel consumption, boiler efficiency, and flue gas characteristics with ammonia ratios were investigated in this paper. Furthermore, the analysis of the variation of furnace radiation attenuation coefficient and blackness with ammonia ratios were also conducted. [Results] The results show that the ammonia ratio increases from 0 to 40%, the heat loss of exhaust gas increases by 5.3%, the boiler efficiency decreases by 0.21%, the flue gas volume increases by 6.2%, the water content in the flue gas increased by 64.2%, and the triatomic gas content decreased by 41.4%,the water dew point increases by 11.9%, the theoretical combustion temperature decreases by 46 ℃, and the furnace outlet temperature increases by 8 ℃. The acid dew point reaches a maximum value of 135 ℃ at 40% ammonia ratio. The flame radiation attenuation coefficient and flame radiation absorption rate, the flame and furnace blackness, gradually decrease with the increase of ammonia ratio in fuel. When the ammonia blending amount of coal-fired generating units is 43%, the carbon emission is consistent with the carbon emission of gas-fired generating units with the same capacity. [Conclusion] The results can provide important support for the development of ammonia-coal co-firing technology, the design of boiler heating surface, and the selection of operating parameters of pollutant control equipment.
[Objective] In this paper, a new type of refractory brick solid heat storage system is designed to optimize thepeaking performance of gas-fired combined cycle units, to solve the problem of nighttime industrial steam supply underthe mode of daytime on/nighttime off of the units, and to realize the energy laddering utilization and cogeneration.[Methods] By establishing a numerical simulation model of steam-coupled refractory bricks thermal storage, the phasechange heat transfer are analyzed, convective heat transfer and thermal conductivity characteristics of the preheat,evaporation and superheat sections. Computational fluid dynamics simulation is combined with experimental validationto investigate the trends and differences of thermal diffusion in the heat storage/exothermic process of the heat storagebody. The mesh-independence validation is applied to ensure the accuracy of the simulation. [Results] The heatstorage system unit reaches more than 80% of heat storage and heat release within 4 h. The maximum average heatstorage rate and heat release rate are 15.9 kW/m3 and 22.0 kW/m3, respectively. It can quickly and efficiently store theheat of the steam and release the heat to the steam, and the experimental and simulation results are in good agreementwith the simulation results, which verifies the feasibility of the technology. The heat transfer temperature and pressure inthe energy release stage is significantly higher than that in the energy storage stage, indicating that the system is moreefficient in releasing energy. [Conclusion] The device can efficiently store and release steam heat, enhance the peakshifting capability of gas-fired units, reduce the dependence on gas boilers, and at the same time realize deep peakshifting and stable supply of thermal energy through heat storage, which can effectively solve the impact of low load ofcoal-fired boilers on the operational safety of the units, and it has significant economic benefits and popularization value.
[Objective]The energy storage policy system is relatively complex and a scientific and comprehensiveevaluation is an effective means to promote the development of the energy storage industry. [Methods]This paper usesthe entropy weight and Topsis method along with the analytic hierarchy process to conduct comprehensive evaluations ofenergy storage policies under various provinces and reflect the level of promotion of energy storage projects by policies.Firstly, considering the effectiveness of policy implementation and combined with the actual application scenarios of energystorage power plants, a comprehensive evaluation system of seven indicators covering economic, technical andenvironmental indicators has been established. Then, the representative policies from Qinghai, Zhejiang, Inner Mongolia,and Henan provinces are selecting and the results of multi-index scenario analysis based on policy content has beenevaluated with entropy weight and Topsis method. Besides, the Analytic Hierarchy Process is used to comprehensivelyevaluate energy storage policies under thinking of different focuses of multiple objectives. [Results]The results indicatethat the entropy weight and Topsis method has the optimal energy storage policy in Zhejiang Province, reflecting therelative maximization of operational efficiency of energy storage power stations under the policy support of ZhejiangProvince. Under the subjective intentions of considering economic, technical, and environmental goals separately, theenergy storage policies in Zhejiang, Henan, and Zhejiang are the most optimal which reflects the level of support fordifferent goals in the three provinces, [Conclusion] indicating the demand to establish a priority order for subjectiveevaluation of policies.