Heat Integration of Processes and Pinch Technology Targeting - a Crude Oil Refinery Application

In many industrial complexes some processes generate excess heat which can be used elsewhere on the site. It is common practice to use a heat transfer medium such as steam to provide indirect thermal integration of the processes. This has the advantage that as steam will usually be raised elsewhere in fuel fired boilers, the propagation of disturbances from waste heat boilers can be minimized. Thus to use steam may alleviate control problems arising from thermal integration. However, there are disadvantages in that the surplus heat has to be transferred twice both in raising and using steam. Furthermore by using steam the quality [energy] of the surplus heat is degraded as the maximum temperature at which this energy can be used is reduced. Direct and indirect thermal integration are compared using the area targeting procedure of pinch technology. A comparison is made of the alternative ways of using surplus heat from the fractionator on a crude oil refinery catalytic cracking unit. The conventional method is to raise steam which is used elsewhere on the refinery including use on a crude oil distillation unit. However, alternative designs are investigated in which the hot oil slurry from the fractionator is used as a direct heat transfer medium to reduce the furnace load on the crude oil distillation unit. Such an arrangement requires substantially less heat transfer surface than that using indirect integration.