Heavier feedstock difficult to process by cat cracking or reforming can be converted by hydrocracking. By combining catalytic cracking and hydrogenation to crack feedstock in the presence of hydrogen, hydrocracking produces gasoline and distillate blending streams. About a dozen different hydrocracking process schemes are in current use.
Level controls for the catalyst stripper, separator liquid and flash drum liquid must contend with severe process conditions to maintain optimum operation of the hydrocracker. These conditions include elevated temperatures and pressures, the presence of steam and high pressure hydrogen, and aggressive corrosives.