Selective conversion of gasoil and paraffinic residual feedstocks.
Deep catalytic cracking (DCC) is a fluidized process for selectively cracking a wide variety of feedstocks to light olefins. Propylene yields over 24 wt% are achievable with paraffinic feeds. DCC uses a conventional traditional reactor/regenerator unit design with a catalyst that has physical properties similar to traditional FCC catalyst. The DCC unit may be operated in two operational modes: maximum propylene (Type I) or maximum iso-olefins (Type II).
Each operational mode utilizes unique catalyst as well as reaction conditions. Maximum propylene DCC uses both riser and bed cracking at relatively severe reactor conditions while Type II DCC uses only riser cracking like a modern fluid catalytic cracking (FCC) unit at milder conditions.
The overall flow scheme of DCC is very similar to that of a conventional FCC. However, innovations in the areas of catalyst development, process variable selection and severity and gas plant design enables the DCC to produce significantly more olefins than FCC in a maximum-olefins mode of operation.
This technology is quite suitable for revamps as well as grassroots applications. Feed enters the unit through proprietary feed nozzles, as shown in the schematic. Integrating DCC technology into existing refineries as either a grassroots or revamp application can offer an attractive opportunity to produce large quantities of light olefins.
In a market requiring both propylene and ethylene, use of both thermal and catalytic processes is essential, due to the fundamental differences in the reaction mechanisms involved. The combination of thermal and catalytic cracking mechanisms is the only way to increase total olefins from light and heavy feedstocks while meeting the need for increased propylene to ethylene ratio. A benefit associated with DCC rather than steam cracking for propylene production is a direct consequence of relative cost differences between DCC heavy feeds and steam cracker’s light feeds. Additional capital and operating costsavings are achieved by the integration of the DCC unit and the adjacent steam cracker.
Licensor: Shaw and Research Institute of Petroleum Processing, Sinopec.