Selective conversion of heavy feedstocks into petrochemical products
Based on the R2R resid fluid catalytic cracking (RFCC) process using a riser and a double regenerator for gasoline production, this new petrochemical version is oriented toward light olefins, particularly propylene, and aromatics. The process is characterized by the utilization of two independent risers. The main riser cracks the resid feed under conditions to optimize fuels production; the second Petro-Riser riser is operated to selectively crack specific recycle streams to maximize propylene production.
The RFCC applies a short contact-time riser, proprietary injection system and severe cracking conditions for bottoms conversion. The temperature and catalyst circulation rates are higher than those used for a conventional gasoline mode operation. The main riser temperature profile can be optimized with a mixed temperature control (MTC) system. Reaction products are then rapidly separated from the catalyst through a high efficiency riser termination device (RS2).
Recycle feed is re-cracked in the PetroRiser under conditions, which are substantially more severe than in the main riser. A precise selection of recycle cuts combined with adapted commercial FCC catalysts and additives lead to high propylene yields with moderate dry-gas production.
Both the main riser and PetroRiser are equipped with a rapid separation system, and the deactivated catalysts are collected in to a single packed stripper, which enhances steam stripping efficiency of the catalyst. Catalyst regeneration is carried out in two, independent stages to minimize permanent hydrothermal activity loss. The first stage is operated in a mild partial-combustion mode that removes produced moisture and limits catalyst deactivation, while the second stage finishes the combustion at higher temperature to fully restore catalyst activity. The R2R system is able to process residue feed containing high metals and CCR using this regenerator configuration and even higher contents with the addition of
a catalyst cooler.
The recycle feeds that can be used in the PetroRiser are light and medium FCC gasoline as well as olefin streams coming from a butenes oligomerization unit. This last option is of particular interesting under market conditions that favor propylene over C4 olefins.
The reaction and regeneration sections use a cold-wall design that results in minimum capital investment and maximum mechanical reliability and safety. Units are tailored to fit the market needs (feedstock and product slate) and can include a wide range of turndown flexibility. Available options include power recovery, waste-heat recovery, flue-gas treatment and slurry filtration and light olefins recovery and purification.
Products: C3 – C4 olefins, in particular propylene; high-octane gasoline, aromatics
Licensor: Axens and Shaw.