苯乙烯装置蒸汽过热炉节能改造案例分析

Case Analysis of Energy-saving Retrofit for Steam Superheater in Styrene Plant

随着国家节能减排政策的推进,燃料气脱硫措施日益普及,使得进一步降低加热炉排烟温度、提升整体热效率成为可能。文章提出的苯乙烯装置蒸汽过热炉节能改造方案,利用原装置蒸汽过热炉对流段的预留空间,结合装置工艺流程,通过在蒸汽过热炉锅炉水预热段增加炉管,增大给锅炉水和烟气的传热面积,同时降低锅炉水进料温度,来降低蒸汽过热炉排烟温度,进一步回收烟气中的余热;降低锅炉水进料温度则通过设置第二预热器实现,即利用锅炉水加热凝液汽提塔的工艺凝液进料,工艺凝液温度的提高还可以降低混合器的注入蒸汽消耗。以某30万吨/年苯乙烯装置为例,与常规烟气余热回收方法比较,本节能改造方案投资可降低约2/3,静态投资回收期约22.5个月,对同类苯乙烯装置具有重要的参考意义。

With the advancement of the national energy conservation and emission reduction policies,the desulfurization measures for fuel gas are becoming increasingly popular,making it possible to further reduce the exhaust gas temperature of the heating furnace and improve the overall thermal efficiency.The energy-saving retrofit scheme for the steam superheater in the styrene plant proposed in this paper utilizes the reserved space in the convection section of the original steam superheater.Combining with the plant process flow,by adding furnace tubes to the boiler water preheating section of the steam superheater,the heat transfer area between the boiler water and the flue gas is increased,while the feed temperature of the boiler water is reduced,thereby reducing the exhaust gas temperature of the steam superheater and further recovering the waste heat in the flue gas.The reduction of the feed temperature of the boiler water is achieved by installing a second preheater,which uses the boiler water to heat the process condensate feed of the condensate stripping tower.The increase in the temperature of the process condensate can also reduce the steam consumption injecting to the mixer.Taking a 300,000 tons/year styrene plant as an example,compared with the conventional waste heat recovery method for flue gas,the investment in this energy-saving retrofit scheme can be reduced by approximately two-thirds,with a static investment payback period of about 22.5 months.This retrofit scheme has important reference for similar styrene plants.