Published September 2006
Fina Research S.A. was recently granted a series of US patents covering the production of propylene from an olefinic feedstock containing at least one olefin of C4 or greater via a cracking reaction over a de-aluminated (Si/Al ratio 180-1000) MFI-type catalyst (e.g., ZSM-5). This review provides a technical and economic evaluation of the technology applied to the production of propylene from an FCN feedstock derived from a fuel mode FCCU. Based on information in the patents and a process simulation, a design was developed for a 60,000 bbl/day plant fed with a typical FCN stream. The plant is projected to produce approximately 680 MM lb/yr propylene, 220 MM lb/yr ethylene, 380 MM lb/yr butylenes, and 1304 MM lb/yr mogas blending stock. Estimated capital cost for the plant is approximately 143 MM$ (2006 Gulf Coast location; addition to an existing refinery). Propylene cash cost is 31.1 cents/lb using 2005 unit values for the ethylene, butylenes and mogas products and the natural gas fuel consumed by the process. Propylene product value is 36.5 cents/lb including a 25% before tax ROI. This value compares with the 2005 unit price for propylene of 36 cents/lb.
According to the above results, incremental propylene can be produced competitively via LCN cracking at least under the base design assumptions and conditions. Scaling down capacity will shave some of the margin but not drastically. Most important will be the propylene yield relative to the other products since there is a substantial difference in the value of the propylene vs the other products. For example, at the olefin conversion of the base case, a 1% reduction in propylene yield and a corresponding increase in butylenes yield (~2%) adds ~ 1 cent/lb to the cash cost of the propylene. On the other hand, examples in the patent do suggest that ethylene and butylene yields can be minimized by recycle of these components to the cracking reactor.
