液相柴油加氢换热网络夹点技术利用

Application of pinch analysis in heat exchange train of a liquid-recycle diesel hydrotreating unit

某炼油厂2.0 Mt/a液相柴油加氢装置共设置2台圆筒炉、15台冷换设备和7片空冷器,总换热负荷超过100 MW。介绍了夹点技术在该装置基础设计换热网络上的应用情况,针对原设计换热网络存在问题进行了合理优化,即通过增加1台精制柴油/原料油（Ⅱ）换热器,使精制柴油蒸汽发生器与反应进料加热炉之间形成1条热负荷有效转移路径,从而达到同时减少反应炉热负荷（夹点上方）和低压蒸汽产量（夹点下方）的目的。结果表明：1装置共减少燃料气消耗6 239 t/a,效益超过2×10^8元/a;2装置生产1.0 MPa低压蒸汽由26.0 t/h降低至14.4 t/h,减少1.0 MPa蒸汽产量11.6 t/h,避免全厂低压蒸汽过剩;3装置换热面积增加742 m^2,投资增加（200-300）×10^4元,投资回收期不足2个月,可行性较好。

In a 2. 0 MM TPY liquid-phase diesel hydrotreating unit,2 cylindrical furnaces,15 heat exchangers and 7 air coolers were installed and the total heat exchange duty exceeded 100 MW. The pinch point analysis was applied in the basic design of the heat exchange train and the process of heat exchange train was optimized. In the optimized design,one hydrotreated diesel / feed（ Ⅱ） exchanger was added so that an effective thermal heat transfer rout was provided between hydrotreated diesel steam generator and reactor feed heater to reduce the thermal duty of reactor heater（ upstream of pinch point） and low-pressure steam production（ downstream of pinch point）. The results showed that（ 1） the fuel gas consumption of the unit was reduced by 6 239 t / yr and the annual saving is over 200 million Yuan RMB and（ 2） the 1. 0 MPa steam production was reduced to 14. 4 t / hr from 26. 0 t / hr which was a 11. 6 t / hr reduction. Although an additional capital investment of 2. 0 - 3. 0 million Yuan RMB investment was required due to the 742 m^2 expansion of heat exchange area,and the return of investment was less than 2 months. A good feasibility has been offered.