Worldwide demand for gasoline and middle distillate fuels is increasing at the expense of heavy fuels and the diesel fuel market is growing faster than that of gasoline. This situation is a problem in many regions for refiners with FCCs. They often have excess gasoline and heavy fuel capacity and yet must import diesel fuel to keep up with their customers’ demand at the pump.

Compounding the above product yield problems are the tightening product quality and environmental specifications; these constraints also affect FCC feed and effluent streams which are linked to the following quality issues:

• SOx and NOx emissions
• 95% of the sulfur in the gasoline pool is contributed by FCC gasoline
• low-cetane (20-25), high sulfur diesel cuts
• high-sulfur slurry and coke.

One approach would be to install a full hydrocracking unit but it is costly and its combined operation with an FCC might not yield the best answer. A more affordable solution exists. Costing but a third of a full hydrocracking unit, an Axens mild hydrocracking (MHDK) process goes far to solve the above problems.

More than 20 units have already been licensed for a combined capacity of 700 000 BPSD.