Alkite Synthesis

Alkite Synthesis

On 1/7, the Alky started to only process FCCU BB and no longer process Coker BB. Alkylation chemistry neither likes contaminants nor diluents. Contaminants are direct acid consumers. The more contaminants in the feed, the more often the unit will be at an acid constraint. Diluents do not reaction in alkylation chemistry but they take up space and decrease the effective area for isobutane and olefin to contact. With less contact, side reactions like polymerization are more likely to occur; polymerization reactions are a direct acid consumer.



Comparing the FCCU and Coker BB, Coker BB contains far more contaminants and diluents than FCCU BB (see Table 2, pg.4).



By lowering the amount of contaminants and diluents, acid consumption was reduced ... Show more content on Helpwriting.net ...The best way to decrease acid residence time is by lowering the level in the settlers. PAR has abnormally high settler levels (45–60% vs. typical 15–20%). The acid consumption impact of running at the appropriate levels in the settler is –0.15 lb/gal or 1.3 MM$/yr in savings (1.1 MM$/yr at cooling constraint and 1.3 MM$/yr at acid constraint). Process Support recommends maintaining a level of 15–20% in C and A settler and a level of 40% in B settler. B settler should be run higher than C or A because of risk of sending lighter hydrocarbons to the spent acid tank.



3. Emulsion recycle



Emulsion recycle minimizes undesirable side reactions, such as polymerization, in the acid settler by keeping the olefins and alkyl sulfates (esters) in contact with isobutane. This results in improved Alkylate quality with reduced acid consumption. Process Support recommends opening all emulsion recycle valves 100%.



In general, maximum acid recycle rates and minimum acid residence time promote better Alkylate product quality, and decrease the potential for polymerization. Net effect of implementing these steps is $5.3 MM$/yr due to reduced acid consumption and lower endpoint.



Operations began lowering settler levels and opening acid recycle valves in February. Progress on this effort will be reported in the next bi–monthly

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