Deep-catalytic cracking (DCC) is a catalytic conversion technology that uses heavy hydrocarbon feedstocks, such as vacuum gasoil (VGO), vacuum resid (VR) or VGO blended with deasphalted oil (DAO) to produce light olefins (ethylene, propylene and butylenes), LPG, gasoline, middle distillates, etc. The technology targets maximizing propylene production (DCC-I) and maximizing iso-olefins production (DCC-II).
The DCC process overcame the limitations of conventional fluid catalytic cracking (FCC) processes. The propylene yield of DCC is 3–5 times that of conventional FCC processes. The processing scheme of DCC is similar to that of a conventional FCC unit consisting of reaction-regeneration, fractionation and gas concentration sections. The feedstock, dispersed with steam, is fed to the system and contacted with the hot regenerated catalyst either in a riser-plus fluidized densebed reactor (for DCC-I) or in a riser reactor (for DCC-II). The feed is catalytically cracked. Reactor effluent proceeds to the fractionation and gas concentration sections for stream separation and further recovery. The coke-deposited catalyst is stripped with steam and transferred to a regenerator where air is introduced and coke on the catalyst is removed by combustion. The hot regenerated catalyst is returned to the reactor at a controlled circulation rate to achieve the heat balance for the system.
The DCC has two reactor operating modes: DCC-I (Riser-plus fluidized dense-bed reactor, maximum propylene mode) and DCC-II (Riser reactor, maximum iso-olefins mode). The DCC can process different heavy feeds—VGO, DAO, coker gasoil, atmospheric residue, VR, etc. Paraffinic feedstocks are the best feeds for DCC. In DCC maximum propylene operation mode, over 20 wt% propylene yield can be obtained from paraffinic feedstocks. The naphtha and middle distillates streams from the DCC unit can be used as blending components for high-octane, commercial gasoline and fuel oil, respectively.
Using a specially designed and patented zeolite catalysts, the reaction temperature in the DCC process is higher than that of conventional FCC, but much lower than that of steam cracking. Other processing benefits include:
• Flexibility of process operation. Easy to obtain the shift of DCC operation modes by regulating the operating conditions and catalyst formulations.
• Easy separation and recovery of product streams through a similar absorption/fractionation of conventional FCC.
Cryogenic separation for separating and recovering DCC product stream is not necessary.
• Contaminants found in the hydrocarbons are at trace levels in DCC lighter olefin products; thus, hydrotreating is not needed.
Licensor: China Petrochemical Technology Co., Ltd.