环己酮装置低品位能的回收利用

Recovery and utilization of low-grade energy in cyclohexanone plant

以100 kt/a环己酮装置为例,分析了装置的用能现状、低品位能分布状况,提出低品位能回收利用方案,并实施技术改造。结果表明:环己酮装置用能主要是低压蒸汽、电、中压蒸汽、循环水,占总能源消耗的98%;在原工艺设计上环己酮装置存在大量未被利用的低品位能,主要来自旧加氢反应器尾气、新加氢反应器尾气、轻塔尾气、醇塔尾气、烷三塔尾气、废碱塔尾气、烷四塔尾气、氧化釜反应液及脱氢反应器尾气中的余热,总计达到208050 MJ/h;通过回收利用技术分析,选择回收利用氧化釜反应液和脱氢反应器尾气的余热,节能效果显著;在氧化工序,增加氧化釜反应液与洗涤塔釜液的换热器,可回收利用余热达26472 MJ/h,可减少低压蒸汽用量26.136 kt/a、循环水用量5110 kt/a;在脱氢反应系统,新增脱氢反应器尾气第二级换热器,可回收利用余热达980 MJ/h,可减少液态烃用量84.8 t/a、循环水用量312 kt/a。

Taking a 100 kt/a cyclohexanone unit as an example,the energy consumption and low-grade energy distribution status of the unit were analyzed.The low-grade energy recovery and utilization plan was proposed and the technical transformation was implemented.The results showed that the main energy consumption of cyclohexanone unit was low-pressure steam,electricity,medium-pressure steam and circulating water,accounting for 98%of the total energy consumption;there were a lot of unused low-grade energy in the original process design of cyclohexanone unit,which mainly came from the waste heat of old hydrogenation reactor tail gas,new hydrogenation reactor tail gas,light tower tail gas,alcohol tower tail gas,the third alkane tower tail gas,waste alkali tower tail gas,the fourth alkane tower tail gas,oxidation kettle reaction liquid and dehydrogenation reactor tail gas,with a total of 208050 MJ/h;the waste heat of oxidation kettle reaction liquid and dehydrogenation reactor tail gas was decided to be recycled through the analysis of recovery and utilization technology,which generated a remarkable energy saving effect;the waste heat of 26472 MJ/h can be recovered and the consumption of low-pressure steam and circulating water can be reduced by 26.136 kt/a and 5110 kt/a,respectively,by adding a heat exchanger of oxidation kettle reaction liquid and washing tower bottom liquid in the oxidation process;and the addition of the second-stage heat exchanger of dehydrogenation reactor tail gas can recycle the waste heat up to 980 MJ/h and decrease the consumption of liquid hydrocarbon and circulating water by 84.8 t/a and 312 kt/a,respectively,in the dehydrogenation reaction system.