溴化锂制冷技术在低温热回收利用中的应用

Commercial Application of Lithium Bromide Refrigeration Technology in Low-temperature Heat Recovery

九江石化为了降低炼油能耗,实施了延迟焦化装置低温余热回收综合利用改造,将50℃热媒水分别进入常减压、1号催化、2号催化等6套热源装置,换热到128℃后,用于再沸器加热,为控制热媒水温度,在末端配有冷却循环水,控制热媒水返回温度在50℃左右。为了增加低温热系统的操作弹性,改造中引入了溴化锂制冷技术。溴化锂制冷机理为水在物体表面蒸发汽化,带走物体表面的热量,在真空条件下,物体表面温度会降到很低。溴化锂是一种吸水性极强的盐类物质,可以连续不断地将周围的水蒸气吸收过来,可创造和维持真空条件。溴化锂吸收式制冷机是利用溴化锂作吸收剂,用水作制冷剂,利用不同温度下溴化锂水溶液对水蒸气的吸收与释放来实现制冷的。应用溴化锂机组后,装置热平衡系统得到优化,循环热媒水末端温度下降到64℃(投用前为76℃),可节约冷却循环水600t/h;焦化装置干气吸收效果明显改善,C3+组分平均值为2.75%(体积分数),同比下降3.11个百分点。

In order to reduce its energy consumption in refining crude oil,SINOPEC Jiujiang Company launched a low-temperature residual heat recovery program for its delayed coking units.50℃ heat medium water was injected into six heat-source units including an atmospheric and vacuum distillation unit,No.1 catalytic unit and No.2 catalytic unit.The water was used to heat a reboiler after being heated to 128℃ through heat exchange.To control the temperature of the heat medium water,a circulating cooling water system is equipped at the end of the process to control the temperature of the returning heat medium water at around 50℃.In order to increase the flexibility of the low-temperature heat system,the company introduced lithium bromide cooling technology.The evaporation of water at the surface of an object will take away the heat at the sur- face of the object and under vacuum conditions,the temperature at the surface of the object will drop signif- icantly.This is why lithium bromide can be used as a refrigerant.Lithium bromide is a salt with strong water absorption.h can continuously adsorb vapor around it,creating and maintaining vacuum conditions.Adsorptive lithium bromide refrigerator uses lithium bromide as absorbent and water as refrigerant and makes use of lithium bromide aqueous solution＇s adsorption and release of vapor at different temperatures for refrigeration. After the lithium bromide unit was introduced,the heat balance system of the heat-source units was opti- mized.The temperature of the circulating heat medium water at the end of process dropped to 64℃from 76℃.As a result,600t of circulating cooling water can be saved per hour.In addition,the dry gas adsorption of the coking unit considerably improved.The average value of C3＋ components was 2.75%（mass fraction）, down 3.11% year-on-year.