FCCU Revamp Costs Controlled by Logic- Based Approach

Description:

Best Practices governing project execution of a unit revamp differ significantly from Best Practices followed in carrying out a grass-roots project. In the latter, workflow normally follows a linear path. In the former, to control scope and minimize capital expenditure, Best Practices dictate a work flow which compresses process design, equipment specification and preliminary estimating into a unified whole. These activities influence up to 60% of total project costs, yet themselves account for less than 5% of total outlay. In undertaking a revamp of the product recovery section of the FCCU at their Edmonton refinery Petro-Canada adopted this logic-based Best Practices approach. Small increases in feed rate and conversion had previously caused upsets which resulted in off-specification products, stressed the downstream LPG treating system and contributed to operating instabilities. Goals of the revamp were increased capacity, improved selectivity and recovery, and making modifications to meet future gasoline sulfur specifications. Major modifications had to be made only to the main column. By following logic-based Best Practices only minor modifications to other equipment were required. One innovative change was a dual LCO product draw that let the existing LCO pumparound pump be reused, required no additional surface area for gas plant reboiler heat input, and made possible higher LCO pumparound duty. Small changes to the depentanizer reboiler feed raised column feed rate and reboiler duty by increasing exchanger LMTD. This permitted production of lower RVP gasoline with minimum C5’s in the LPG. All objectives of the revamp were met or exceeded.