大型纯凝汽轮机供热改造节能研究

Energy Saving Research of Heating Retrofitting for Large Scale Condensing Turbine

大型纯凝汽轮机供热改造过程中,由于中压缸级数相对于设计的供热机组少,导致中低压缸联通管打孔抽汽压力远远高于所需求的供热压力,造成可用能的节流损失。该文针对此问题提出了解决措施,即增加背压机,将较高压力的抽汽先做功发电后再进行供热。分别针对单机型和双机型大型纯凝汽轮机的供热改造建立了理论分析模型,结合实际300 MW机组的案例分析发现,采用增加背压机做功的模式,对单机型改造,可以在不影响供热效果的前提下,回收供热抽汽的动力,同时由于不与另外机组耦合,设备结构简单,运行控制简便;对双机型改造,设备连接虽相对复杂,但采用热网加热器的串联模式,能量的梯级利用更加合理,保证供热的条件下,回收了更多的供热抽汽动力。结果表明,新型的供热改造模式可以收到较好的综合经济效益。

During the process of heating retrofitting, the pressure of steam extracted from the communicating pipe between intermediate pressure（IP） and low pressure（LP） cylinders is much higher than required heating pressure, because the IP cylinder of pure condensing turbine has fewer stages than cogeneration turbine. Heating with such high pressure steam leads to the waste of energy grade. To solve this problem, this paper proposed a measure that using a back pressure turbine to bring high pressure of extracted steam down and generate power, after that the steam with reasonable pressure transferred heat with water in heat-supply network. Viewing of single and double retrofitted unit, the analytical models were set up respectively. Based on theoretical calculation of 300MW retrofitted unit, it can be found that much power is recovered with no impact on heating. The improvement proposal for single retrofitted unit has the advantage of simple structure and convenient maintain and operation. While to the improvement proposal for double retrofitted units we can recover more power as a result of series thermal-system heater and the effect of cascade utilization of energy is more apparent, though the structure of this system is more complex. In conclusion, the new retrofitted mode to pure condensing unit not only has no impact on heating, but also can gain more economic returns.