Abstract: A 4.20 Mt/a catalytic cracking (FCC) unit in a refinerywas modeled and forecasted by Aspen Plus. Based on the cold and heat material flow dataextracted from the model, pinch technologywas used to analyze the heat exchange network of the whole FCC unit.It was found that the absorption and stabilization system of the original FCC unit had high energy consumption, large thermal utility consumption, large temperature difference of the mixture feedstock, high quality and low use of light cycle oil, heavy cycle oil and slurry, low final temperature of desalted water,and large steam consumption of deaerator and so on. By optimizing the reflux ratio of the stabilizer and supplementing the absorption flow rate, the load of the absorption stabilization system was reduced, and the heat transfer network of the unit was optimized by using pinch technology. The results showed that the steam could be saved by 27.3 t/h, which wasequivalenting tosaving energy by 16603 tOE/a (1 tOE = 41.8 GJ) or 23757 tCE/a (1 tCE = 29.27 GJ), and reducedcarbon dioxide emission equivalent by76457 t/a. The retrofit also reduced the heat medium water delivered out of the FCC unit by 300 t/h, and the heat loss was reduced by using 10.27 MW of heat medium water in the unit.

Key words: catalytic cracking, process simulation, heat exchange network, pinching technique, low temperature hot water