Thermodynamic Analysis And Optimization On Cement Kiln Low Temperature Waste Heat Power Generation System Under The Condition Of The Plateau Climate

Cement industry is energy intensive industries, in recent years, although the production technology for cement clinker has made great progress, but the energy consumption of the cement industry is still high. It is one of the best ways to reduce energy consumption of the cement industry by the way of low temperature waste heat power generation technology. Qinghai province is located in the high altitude, annual average temperature is low, day and night temperature difference is big, low atmospheric pressure. The efficiency of the low temperature waste heat power generation system is low by the influence of plateau climate. This paper based on the project of the plateau adaptability research and demonstration on low temperature waste heat power generation system of cement industry. Take thermodynamic analysis on low temperature waste heat power generation system of typical cement production enterprises in Qinghai province, and optimize the low-temperature waste heat power generation system, achieve the purpose of improving the efficiency of power generation.Make material flow and energy flow analysis on the waste heat power generation system by the law of conservation of mass and the first law of thermodynamics. It founds that the energy losses are mainly concentrated in the steam turbine, the steam exhaust, waste gas, boiler and steam pipe cooling and circulating water after analysis. Circulating water and the AQC furnace exit flue gas contains energy were114.10 GJ /h and 30 GJ/h, the loss of energy is large from the number. But combining the first law and second law of thermodynamics, it founds that the exergy out from AQC furnace is relatively small, only 3.46 GJ/h through the exergy analysis. And the temperature of the gas is below 85℃, has little recycling value. The exergy was taken from the condenser by the circulating water is 4501.2 MJ/h, It is only accounts for 4.5% of the whole system, so it’s difficult to reduce the exergy losses of the whole system by reducing the number of circulating water. The steam turbine, the AQC furnace and SP furnace is the keys to improve the efficiency of exergy, Their exergy losses of the system exergy loss are respectively 40.67%, 20.33% and 21.31%. Take parameter optimization on steam turbine and waste heat boiler, reduce the exergy losses can effectively improve the exergy efficiency of the total waste heat power generation system.The influence the main steam temperature, main steam pressure, pinch temperature point and approach temperature point exert upon AQC furnace, SP furnace, steam turbine and associated exergy efficiency was studied. And through the study of the influence of various parameters on the joint energy efficiency, found that the influence of parameters on the joint exergy efficiency from big to small order is the main steam temperature, main steam pressure, pinch temperature point and approach temperature point which belongs the node temperature difference. The main steam temperature and main steam pressure is chosen as the final optimized parameters, take combined optimization to boiler and steam turbine. After optimized, the loss exergy of AQC furnace is 8.5906×106 k J/h, the loss of SP furnace is 6.8362×106 k J/h and the loss of steam turbine is 1.3615×106 k J/h, reduced by 1.38%, 2.52% and 1.38% respectively compared to that before optimization, the system capacity can be increased from 7.12 Mw to 7.65 Mw after optimization. The exergy of the steam exhaust out of the steam turbine is 11478 MJ/h, the size of the steam exhaust exergy is not only related to the parameters of steam into steam turbine and the performance of steam turbine, also associated with the vacuum of the condenser. Studied the relation of condenser vacuum degree and capacity, improve the vacuum of the condenser is given. By increasing the circulation of water, add spray device, replacing efficient vacuum extraction system and measures to increase the heat transfer coefficient, the vacuum of condenser is improved 0.006 Mpa, Power generation is increased 640 kwh per hour, the effect is remarkable.