Abstract
Heat Integration of process plants leads to better energy conservation. This energy conservation can be utilized for increasing the capacity. In many plants the energy supply is the bottleneck for expansion. In such cases better heat integration can be used to overcome this bottleneck. In this paper we will talk about a case study that was done for debottlenecking a Refinery Crude Distillation Unit (CDU) through heat integration. The energy sources in this case are the furnaces. The maximum heat duty of the furnaces is limited by its design. The conventional solution for such a case is addition of another furnace or replacement by other furnaces of higher capacity.
The unit consists of the crude preheat train Heat Exchanger Network (HEN) in which the heat recovery shall be increased through better integration. The better integration is achieved at two levels, namely the network level and the exchanger level. For retrofit projects the modifications shall be minimal in order to achieve economic feasibility. For this reason the preheat train was divided in three sections depending on the plant layout. The analysis was first done for each section individually followed by the analysis for the whole preheat train, the three sections collectively.
The outcome of this study was a heat-integration-based retrofit design that will give a 20% increase in throughput utilizing the same existing furnaces and hence same energy consumption. This means a 20% more energy-efficient design yielding the saving of about 100 million Btu/hour of fuel gas and an estimated CO2 emissions reduction of 40,000 tons/year. Moreover the capital cost of this proposal is estimated to be 40% less than the traditional solution of adding a new train. Other components of the CDU including columns, vessels, furnace, piping and pumping systems were also analyzed and modified in accordance to the proposed new design.
