1.1. Pinch Analysis of the Crude Oil Distillation Process
Pinch analysis is applied to the crude oil distillation system to determine the minimum utility requirements and to find any applicable modifications to the process. The petroleum refining industry ranks third, after the chemical and the primary metal industry, in its energy consumption [2]. In addition, in any refinery, there is a wide range of temperatures where heat must be supplied or removed. Therefore, applying pinch analysis to the crude oil distillation system is necessary to reduce the energy consumption as far as possible.
Figure 1: Base case configuration of the case study
Pinch analysis is a thermodynamically based method for the design of heat and power systems. The method of pinch analysis groups the heat sources and sinks of the process streams into temperature intervals, where it is possible to transfer heat in each interval from heat sources to heat sinks [3]. The grand composite curve can be used to provide an interface between the distillation column and the utility system. If a number of different utilities are available, the grand composite curve can be used to determine the relative amount of each utility needed.
If there are mismatches between the process streams profiles and the utility profile, then process modifications are needed to remove these mismatches as far as possible. Process modifications may change the heating or cooling requirements of the streams which will be reflected on the grand composite curve. The modifications, which increase the heat recovery, will increase energy savings. Pinch analysis, in particular the grand composite curve, provides valuable information about each modification to the crude oil distillation system with respect to the utility costs. The main objective of using pinch analysis is to maximize the use of the least expensive utilities and minimize the use of the most expensive utilities.