Combination hydrocracking process for the production of ultra low sulfur diesel

A hydrocracking process for the production of ultra low sulfur diesel from a hydrocarbonaceous feedstock wherein the process comprises the steps of:

• (a) reacting the hydrocarbonaceous feedstock and hydrogen in a hydrocracking zone containing hydrocracking catalyst to produce diesel boiling range hydrocarbons;
• (b) stripping a hydrocracking zone effluent in a hot, high pressure stripping zone maintained at essentially the same pressure as the hydrocracking zone and a temperature in the range from about 232° C. (450° F.) to about 468° C. (875° F.) with a first hydrogen-rich gaseous stream to produce a first gaseous hydrocarbonaceous stream comprising diesel boiling range hydrocarbons and a first liquid hydrocarbonaceous stream;
• (c) passing the first gaseous hydrocarbonaceous stream comprising diesel boiling range hydrocarbons to a desulfurization zone containing desulfurization catalyst and producing a desulfurization zone effluent stream;
• (d) condensing at least a portion of the desulfurization zone effluent stream to produce a second hydrogen-rich gaseous stream and a second liquid hydrocarbonaceous stream comprising diesel boiling range hydrocarbons;
• (e) passing the first liquid hydrocarbonaceous stream to a hot flash zone maintained at a pressure from about 445 kPa (50 psig) to about 2858 kPa (400 psig) and a temperature from about 232° C. (450° F.) to about 468° C. (875° F.) to produce a third liquid hydrocarbonaceous stream comprising unconverted hydrocarbons and diesel boiling range hydrocarbons;
• (f) reacting the third liquid hydrocarbonaceous stream in a non-catalytic thermal cracking zone to produce an effluent stream containing additional diesel boiling range hydrocarbons;
• (g) separating the effluent stream produced in step (f) to produce a fourth liquid hydrocarbonaceous stream comprising diesel boiling range hydrocarbons;
• and
• (h) recovering an ultra low sulfur diesel product stream.