To selectively convert vacuum gasoils, paraffinic residual feedstocks and resulting blends of each into C2–C5 olefins, aromaticrich, high-octane gasoline and distillate using the Deep Catalytic Cracking (DCC) process.
The DCC process selectively cracks a wide variety of feedstocks into light olefins, with a reactor/regenerator configuration similar to traditional fluid catalytic cracking (FCC) units (see figure). Innovations in catalyst development and process variable selection lead to synergistic benefits and enable the DCC process to produce significantly more olefins than an FCC that is operated for maximum olefins production.
The DCC process was originally developed by the Research Institute of Petroleum Processing (RIPP) and Sinopec in the People’s Republic of China. Shaw’s Energy and Chemicals Group is the sole engineering contractor licensed to offer DCC technology outside of China.
DCC units may be operated in two modes: maximum propylene (Type I) or maximum iso-olefins (Type II). Each operational mode utilizes unique catalyst as well as specific reaction conditions. DCC-I uses both riser and bed cracking at more severe reactor conditions, while DCC-II utilizes only riser cracking like a modern FCC unit at milder conditions. The DCC process applies specially designed and patented zeolite catalysts. The reaction temperature in DCC is higher than that of conventional FCC but much lower than that of steam cracking. Propylene yields over 20 wt% are achievable with paraffinic feeds. Ethylene yield is much higher than the conventional FCC process. The DCC-mixed C4s stream also contains increased amounts of butylenes and iso-C4s as compared to an FCC. The high olefin yields are achieved by deeper cracking into the aliphatic components of the naphtha and LCO. The dry gas produced from the DCC process contains approximately 50% ethylene.
The cracking reactions are endothermic, and compared to FCC, a higher coke make is required to satisfy the heat balance. Table 1 summarizes typical olefins yields for DCC with FCC.
This technology is suitable for revamps as well as grassroots applications. The DCC process is very suitable for integration with an ethylene plant—refer to “HOFCC and Ethylene Plant Integration” for the benefits of capital reduction and production efficiency.
Licensor: The Shaw Group