Temperature and pressure reducers are widely used in the steam power system of petrochemical plants, which can transfer higher pressure steam to lower pressure steam for different grades of heat demands. Otherwise, generally in summer there is abundant low pressure steam in plants. Using backpressure turbines to replace temperature and pressure reducer, as well as condensing steam turbines to recover the energy of the abundant low pressure steam are effective energy-saving methods. In this paper, an economic evaluation model is proposed for determining the critical economic point for back-pressure and condensing steam turbines. The effect of steam price or the price ratio of electricity to heat on the critical point is discussed. The results for an industrial case show that the critical powers of steam turbine are relatively low, which means that in most industrial cases, using steam turbines to save energy is beneficial. This paper provides guidance in selection of suitable steam turbine for energy saving in petrochemical plants.%在石化企业蒸汽动力系统中存在大量的减温减压器,将较高压力蒸汽转化为较低压力蒸汽以适用于不同品位热量的需求.此外在夏季企业可能存在低压蒸汽过剩现象.采用背压汽轮机替代减温减压器和凝汽汽轮机回收过剩低压蒸汽能量是节能的有效方法.为了确定采用汽轮机的经济合理的范围,通过经济评价方程,获得了背压汽轮机和凝汽汽轮机的经济出力分界点,并讨论了在不同蒸汽价格或电热比价下该分界点的变化.案例结果表明,该临界值所对应的功率较小,表明在企业多数情况采用汽轮机的节能方案是经济可行的.本文可为在石化企业的节能减排中采用工业汽轮机提供指导和依据.
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