Retrofit of Crude Distillation Unit Using Process Integration

Nowadays energy is a fundamental driver of economic growth and hence is essential to our well being and quality of life. Pinch technology and its recent extensions offer an effective and practical method for designing the HEN for new and retrofit projects. Crude distillation unit is the basic processing step in oil refinery and is a highly energy-intensive process and represents one of the most important areas for energy integration in a refinery. Frequently, the heat exchanger network (HEN) of this unit, one of the most complex in oil refinery, need retrofit. The HEN of the distillation unit considered here consists of a crude preheat-exchanger network and flashing section, atmospheric distillation section, and vacuum distillation section. Because some of the heat exchangers in this unit have a relation to the S.R.G. unit also was considered this unit. he case study to be considered is for a reasonably complex refinery of moderate capacity (Esfahan refinery). In this paper, the approach is to produce different acceptable scenarios of retrofit using an integrated instrument (process simulator and process integration software). In this case Aspen Plus environment integrated with Aspen Pinch software from Aspen Tech Company are used to illustrate the pinch methodology. The incremental area efficiency methodology was used for the targeting stage of the design and the design was carried out using the network pinch method consisting of both a diagnosis and optimization stages. In the diagnosis stage promising designs were generated using Aspen Pinch software. The generated design was then optimized to trade-off capital cost and energy savings. The design option were compared and evaluated and the retrofit design suggested. The stream data consists of 21 hot and 10 cold streams and cost and economic data required for the analysis were specified. The existing hot utility consumption of the process was 96962.09 kw. The area efficiency of existing design was 0.5895. The targeting stage using incremental area efficiency sets the minimum approach temperature at 33 °C, thereby establishing the scope for potential energy savings. To achieve a practical project, the numbers of modifications were limited. The modifications include re-sequencing (changing the order of exchangers on a stream), addition of new heat exchanger units, re-piping of existing exchanger and split of stream. Many options were analyzed for heat recovery and in the best options were saved about 9.2464% of overall energy consumption in furnace.