| As the most important way of power generation in China,thermal power generation will still occupy the dominant position in the power industry for a long time.With the development and progress of the country,the requirements for energy conservation and emission reduction in all walks of life are constantly increasing,and the energy-saving transformation of thermal power units is also imminent.Double reheat technology and waste heat utilization technology greatly improve the efficiency of thermal power unit,and the double reheat power plant more and more widely,the regulation of reheating temperature control becomes one of the research,and waste heat utilization of double reheat million units using simulation modeling and hot economic analysis also has the profound significance.Based on the double reheat millions unit as the research object,using Ebsilon simulation software,without using the waste heat utilization of excised bypass system,using waste heat utilization of the standard system and optimized system,three systems to establish coupling model of boiler system and steam turbine system in detail,and the analysis of the variable condition,model validation results maximum error in 4%.In this paper,flue gas recirculation was mainly used to regulate the temperature of the double reheat unit.When the intermediate temperature was not controlled,taking the standard system as an example,the flue gas recirculation rate under different loads increased with the temperature of the intermediate point.When the intermediate temperature was control,the influence of four factors on the flue gas recirculation rate,such as load,excess air coefficient,coal quality and feed water temperature,was studied in three systems.The flue gas recirculation rate of the excised bypass system and the optimized system decreases gradually with the increase of load,and the low load of the reference system decreases with the increase of load.The recycling rate of flue gas is inversely proportional to the excess air coefficient.When the excess air coefficient changes,the recycling rate of the cut bypass system changes around 0.07,which has the greatest influence on it.The flue gas recirculation rate of the coal with high moisture content was lower,and the influence of coal with low volatile content and high ash content on the temperature of reheat steam was greater than that of coal with high volatile content and low ash content.The feed water temperature is in direct proportion to the flue gas recirculation rate.The comparative analysis of the thermal economy of the three systems with the changes of three factors,the load,the air temperature at the entrance of the coal mill and the temperature at the middle point of the flue gas bypass is made:With the increase of load,the coal consumption rate of the three systems decreases,and the coal saving rate of the optimized system increases greatly,reaching 5.464g/kWh when the load is 100%.The thermal economy of the optimized system is the best.The coal consumption rate of the standard system and the optimized system increases with the air temperature rise at the coal mill inlet,and the thermal economy decreases.Compared with the standard system,the higher the air temperature at the coal mill inlet within a certain range,the higher the coal saving rate,and the better the thermal economy of the optimized system.When the air temperature at the inlet of the coal mill is 225?,the coal saving rate is 2.942g/kWh compared with that of the standard system.For the standard system and the optimized system,the coal consumption rate increases with the increase of the temperature of the middle point of the bypass,and the thermal economy of the system also decreases.When the temperature changes by 120?,the quantity of coal saving of the excised bypass system is 3.09g/kWh,and the quantity of coal saving of the optimized system is 4.83g/kWh.The hot primary air bypass of the optimized system is cut off,the hot primary air temperature is used to heat part of the feed water,and to construct the optimized transformation system.The thermal economy parameters of the optimized system and the optimized transformation system were compared and analyzed under the condition of load and the distribution ratio of flue gas cooler.The coal consumption rate of the optimized transformation system was lower and the thermal economy performance was higher.When the load is 100%,the maximum coal saving amount of the optimized transformation system reaches 1.14g/kWh by comparing with the optimized system.The distribution ratio of flue gas cooler has little effect on system economy. |
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