Heat integration retrofit analysis of a heat exchanger network of a fluid catalytic cracking 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 fluid catalytic cracking (FCC) is a dominant process in oil refineries and there has been a sustained effort to improve the efficiency and yield o f the unit over the years. Nevertheless, benefits and scope for improvement can still be found. The HEN of the FCC process considered here consists of a main column and a gas concentration section. Appropriate data were extra cted from the existing network, using flowsheeting simulation. The stream d ata consists of 23 hot and 11 cold streams and cost and economic data requi red for the analysis were specified. The incremental area efficiency method ology was used for the targeting stage of the design and the design was car ried out using the network pinch method consisting of both a diagnosis and optimisation stage. In the diagnosis stage promising designs were generated using UMIST developed SPRINT software. The generated design was then optim ised to trade-off capital cost and energy savings. The design options were compared and evaluated and the retrofit design suggested. The existing hot utility consumption of the process was 46.055 MW with a De ltaT(min) of 24 degreesC. The area efficiency of existing design was 0.805. The targeting stage using incremental area efficiency sets the minimum app roach temperature at 11.5 degreesC, thereby establishing the scope for pote ntial energy savings. To achieve a practical project, the number of modific ations is limited. The selected retrofit design has 8.955 MW saving - 74% o f the whole scope. This corresponds to 27% utility cost savings with a payb ack period of 1.5 years. The modifications include addition of four heat ex changer units and repiping of one existing exchanger. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.