Excessive refinery fuel gas production can be attributed to a variety of factors. One that
stands out is related to Fluid Catalytic Cracking Unit (FCCU) and reformer operation
changes over the last 35 years. When the shift was made from leaded to unleaded
gasoline, higher octane naphtha was required. The higher octane demand was met in a
couple of ways that resulted in higher fuel gas production. First, FCCU severity increased
through higher reactor temperatures. The side effect of this was an increase in LPG and
fuel gas production from the FCCU. Second, reformer severity was increased to make
higher octane reformate. As was the case on the FCCU, this more severe operation on the
reformer resulted in additional fuel gas production due to cracking brought on by higher