Analysis And Operation Optimization Study On The Waste Heat Power Generation Systems Of Coke Dry Quenching

Energy conservation is one of the most important policies to transform the extensive economic growth mode and ease the pressure on resources and environment. Steel is a energy-intensive and high-polluting industry, and it is a key industry of the national energy saving. With the increasing pressures of the external resources, energy and environment, recycling the waste heat energy produced in the steel production process efficiently is the main direction and breakthrough in the steel industry energy conservation of the future. The Coke Dry Quenching(CDQ) is an important technology of recycling coke sensible heat in the steel production process, in this dissertation, the CDQ process is taken as the research object. According to the porous media heat transfer and collaborative field theory, the theoretical study of efficient recycle of CDQ waste heat and thermodynamic analysis on the Qian’an Zhonghua CDQ power plant system were taken, and on its basis, system operation optimization and parameters regulation research were taken. The main contents in the dissertation were as follows:1. Establish CDQ waste heat power generation system model; Establish CDQ coke cooling heat transfer model, and using the porous media heat transfer and collaborative field theory to analyze cooling mechanism of coke;2. On the basis of the design conditions and combining with the operating conditions of Qian’an Zhonghua Coal Chemical Co., Ltd. CDQ waste heat power plant, comparative analysis is made from the perspective of thermal balance and exergy balance. The results show that the largest part of heat loss in CDQ system is the condensation process in the condenser 58.47% and the heat loss of discharging coke in the chamber 18.57%; however the largest part of exergy loss is the chamber 13.64%, the recovery boiler 21.90% and the turbine 18.74%. On the basis of the energy balance calculations, using the “Energy Utilization Diagram methodology” to make exergy loss analysis on the chamber, recovery boiler and turbine respectively, point out that the exergy loss in the chamber can be divided into 2 parts: the cooling section and annular flue. The percentage of the convection heat exchange exergy loss between coke and circulation gas in cooling section is 55.7%, and the percentage of the heat exchange exergy loss caused by the combustion of coke powder and gas in annular flue is 44.3%. The exergy loss in the recovery boiler can be divided into 3 parts: economizer, evaporator and superheater, the largest part of the exergy loss is in the evaporator, accounting for 60.98% of the boiler heat exchange exergy loss.3. Establish CDQ waste heat power generation system optimization model, taking the maximum net generating capacity per ton coke as objective function, and making the cooling ventilation rate and recovery boiler main steam parameters as controllable variables, then optimize them separately, then combining with “Energy Utilization Diagram methodology” to analyze the relation between exergy loss variation of the major equipment in CDQ waste heat power generation plant and the operating parameters. On the basis of operating parameters optimization, the main parameters control of chamber system and recovery boiler system were analyzed. In actual production, on the basis of the design conditions, improving the main steam parameters appropriately and controlling the wind coke rate in the range of 1600Nm3 / t-1700Nm3/t, In this case, the exergy loss in chamber and recovery boiler is relatively small, system efficiency is relatively high, net generating capacity per ton coke of CDQ waste heat power generation plant can reach the maximum and the economic benefit is more significant.