INTEGRATED DESIGN OF A CONVENTIONAL CRUDE-OIL DISTILLATION TOWER USING PINCH ANALYSIS

The substantial energy requirement of crude oil distillation columns i s met partly by costly utilities, such as steam and fuel for fired hea ters, and partly by heat recovered from the process, using process-to- process heat exchange. Energy savings, therefore, demand not only a di stillation column that is energy-efficient, but also a heat exchanger network (HEN) which minimizes utility costs by maximizing heat recover y. A new crude oil distillation design procedure is presented which co nsiders the column, the HEN and their interactions simultaneously, to minimize utility costs. Pinch analysis is used to determine minimum ut ility costs prior to the design of the KEN. In this method, the column is decomposed into a sequence of simple columns, which enables approp riate distribution of stages and simplifies analysis. Modifications, w hich further increase the efficiency of the process, are proposed: the se are the installation of reboilers, rather than stripping steam, and the thermal coupling of column sections. The detrimental effects of t hese modifications on the heat recovery opportunities of the process a re analysed for a distillation tower with side-strippers. A new step-b y-step design procedure is derived from this analysis, and is applied to a case study. In the case study, the resulting design offers nearly 20% savings in utility costs over the base case design. The vapour fl ow in the column is reduced by a similar amount, offering capital savi ngs, additional flexibility or the opportunity to increase throughput. The new integrated design procedure considers the column and its asso ciated HEN simultaneously, aiming to minimize operating costs by obtai ning the best fit between the process and the available utilities.