Analysis Of Heat Storage And Release Process Of Spherical Heat Accumulator

Steam accumulator is a kind of energy saving equipment which is widely used.It uses water as heat storage medium to store heat energy,which can obtain steam with stable quality and improve energy utilization rate.At present,most steam accumulators are horizontal.In recent years,spherical accumulators have been gradually popularized by virtue of their advantages of less land area,more heat storage and less heat dissipation.The principle of heat storage and release is the same as that of the traditional accumulator,but the structural form will have a certain influence on the change of specific parameters.Most of the existing studies are aimed at analyzing the heat storage and release process of the horizontal heat accumulator.This paper mainly analyzes the heat storage and release situation of the spherical heat accumulator for a long time,and adjusts the steam flow by selecting appropriate regulating valves and control strategies,so as to achieve the purpose of stable output.In this paper,the spherical heat accumulator is taken as the research object,and the design data of a converter flue gas waste heat recovery system is taken as a case to analyze and calculate.Based on the theory of heat transfer,the heat dissipation and other properties of spherical and horizontal heat accumulators with the same volume and insulation effect were compared by using the method of hypothetical wall temperature check.The effects of static water pressure,output pressure of heat accumulator and temperature decrease on evaporation rate were analyzed,and evaporation was calculated according to the temperature drop method.Since there is a certain humidity in the output steam,the influence of steam with water is analyzed,and the starting power is calculated to get the coal saving amount.In addition,the thermodynamic analysis of the process of heat storage and release and power generation is carried out.Taking the calculation results of static heat storage and release process as the conditions for the selection of regulating valve,the change of valve opening,flow rate and other parameters with time under different control strategies was studied after determining the regulating valve,so as to obtain a more appropriate control strategy and more stable steam quality.The results show that compared with the horizontal heat accumulator and the spherical heat accumulator with the same volume,the heat dissipation of the spherical heat accumulator is about half of that of the horizontal heat accumulator,and the use of the spherical footprint,instruments,valves and other accessories is also less.The analysis results of heat release process show that with the increase of flash pressure drop,the influence of water level depth on flash evaporation rate decreases.With the decrease of pressure in the heat accumulator,the evaporation rate will increase under the same flash pressure drop,while with the decrease of temperature,the evaporation rate will decrease.With the decrease of saturated steam pressure,the constant entropy expansion work of steam in steam turbine decreases rapidly,and the influence of pressure reduction is greater than that of humidity increase.The ideal constant entropy expansion process of steam turbine is materialized with 75%efficiency,and it is concluded that 8563t-9134t of standard coal can be saved every year.When the two strategies of different time intervals and different temperature drop modes are used to control operation,it is shown that the valve opening gradually decreases in the process of heat storage,while the valve opening gradually increases in the process of heat release,and the adjustment range decreases first and then increases.The smaller the change of control time interval and temperature drop,the smaller the fluctuation of steam flow variation.Steam flow gradually increases in each time interval of heat storage process,while steam flow gradually decreases in each time interval of heat release process.Based on the above analysis results,the control strategy of variable step size in process is proposed.This study lays a foundation for subsequent research and provides theoretical support for further popularization and operation regulation of spherical heat accumulator.