Abstract: DCC (Deep Catalytic Cracking) is a catalytic conversion process derived from the FCC (Fluid Catalytic Cracking) process, using heavy feedstocks for producing more propylene. The absorption-stabilization system of DCC unit and the gas separation unit followed requires more low-grade heat, compared with the conventional FCC unit. Hence, the heat integration schemes of DCC and gas separation unit have significant impacts on the low-grade waste heat recovery, steam balance and cooling duty. In this paper, exergy analyses with two heat integration schemes of DCC and gas separation units, including the direct heat integration scheme based on circulating hot water, and the scheme based on the heat pump process, are presented using process simulation software and ε-Q diagram. The analysis results show that the heat integration scheme based on the heat pump process can reduce 13.1% exergy loss of heat exchange process and the consumption of 1.0 MPa steam 20 t/h, but needs higher equipment investment costs. According to the study, the optimal matching of low-grade heat sources and sinks in DCC and gas separation units is a vital factor of increasing the energy efficiency.

Key words: DCC, gas separation, heat integration, heat pump