Heat Integration Retrofit Analysis of A Heat Exchanger Network of A Distillation Plant

The impact of a process system on environmental pollution has both a local and global effect. The performance of the heat exchanger network (HEN) in a plant is an important aspect of energy conservation. Pinch technology and its recent extensions offer an effective and practical method for designing the HEN for new and retrofit projects. The Distillation unit is first process in oil refineries and there has been a sustained effort to improve the efficiency and yield of the unit over the years. Nevertheless, benefits and scope for effort to improvement can still be found. 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. Appropriate data were extracted from the existing network, using flow-sheeting simulation. The stream data consists of 21 hot and 10 cold streams and cost and economic data required for the analysis were specified. 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 stage. 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 existing hot utility consumption of the process was 78.4 MW with a 5T 40°C. The area efficiency of existing design was 0.7254. The targeting stage using incremental area efficiency sets the minimum approach temperature at 18.96 °C, thereby establishing the scope for potential energy savings. To achieve a practical project, the number of modifications is limited. The modifications include addition of new heat exchanger units and repiping of existing exchanger.

Keywords:

heat integration , crude oil , retrofit , heat exchanger network