燃气-蒸汽联合循环热电联产机组供热特性分析

Analysis on heat supply performance of gas-steam combined cycle cogeneration units

以某460 MW燃气-蒸汽联合循环热电联产机组为对象,研究了利用Ebsilon仿真软件建立模型并进行变工况计算的过程,通过仿真结果与热平衡图上设计值的对比,验证了模型及该建模方法的准确性和可靠性,证明该方法适用于燃气-蒸汽联合循环热电联产机组的计算。此外,对不同供热抽汽流量、环境温度以及负荷率下机组供热特性进行分析。结果表明:在性能保证条件燃气轮机100%负荷率工况下,当高、中、低压抽汽流量分别从0增加到60 t/h时,机组联合循环效率分别提高4.24%、4.31%、4.08%,热耗率分别降低193.6、215.4、203.3kJ/(kW·h);环境温度低于15℃时,额定供热工况下联合循环热耗率与环境温度成负相关,环境温度高于15℃时成正相关;燃气轮机负荷降低会使汽轮机可运行功率范围减小,机组调峰能力减弱;当供热量大于300 GJ/h时,在相同供热量下75%负荷率下机组的联合循环效率高于100%负荷率。本文研究结果可为燃气-蒸汽联合循环热电系统的优化运行提供数据支撑和理论依据。

Taking a 460 MW gas-steam combined cycle cogeneration unit as the object, the process of modeling and calculating the variable conditions by using Ebsilon software was studied. The accuracy and reliability of the model and the method were verified by comparing the simulation results with the design values on the heat balance diagram. It proves that the modeling method is suitable for calculation of the gas-steam combined cycle cogeneration unit. Besides, the heat supply performances of different heating extractions, ambient temperatures and load rates conditions were analyzed. The results show that, as the mass flow of the high, medium and low pressure extraction steam increases from 0 t/h to 60 t/h, the combined cycle efficiency increases by 4.24%, 4.31% and 4.08%, respectively, and the heat consumption rate decreases by 193.6 kJ/(kW·h), 215.4 kJ/(kW·h) and 203.3 kJ/(kW·h). When the ambient temperature is lower than 15 ℃, the combined cycle heat rate is negatively correlated with the ambient temperature under rated heating conditions, and positively correlated when the ambient temperature is higher than 15 ℃. The reduction of the gas turbine load will shrink the operating power range of the steam turbine, and the peak shaving capacity of the unit will be weakened. When the heat supply is greater than 300 GJ/h, the combined cycle efficiency at 75% load rate will be higher than that of 100%. The results can provide data supports and theoretical guidance for the optimal operation of gas-steam combined cycle thermoelectric systems.