FCC process and apparatus with automatic catalyst recycle control

An apparatus for the fluidized catalytic cracking of hydrocarbons, the apparatus comprising:

• a riser in which blended catalyst is contacted with a hydrocarbon feed;
• a separator vessel for receiving effluent from said riser and separating said effluent into a vapor product and spent catalyst;
• a recycle catalyst conduit communicative with said separator vessel for passing spent catalyst to a base of said riser, said recycle catalyst conduit including a recycle catalyst control valve for regulating spent catalyst circulation and instrumentation for determining the circulation rate of spent catalyst through said recycle catalyst conduit;
• a regenerator vessel for removing carbon from said spent catalyst to provide regenerated catalyst;
• a spent catalyst conduit communicative between said separator vessel and said regenerator vessel for passing spent catalyst to said regenerator vessel;
• a regenerated catalyst conduit communicative between said regenerator vessel and the base of said riser for passing regenerated catalyst from said regenerator vessel to the base of said riser, wherein said regenerated catalyst is blended with said spent catalyst to provide said blended catalyst, said regenerated catalyst conduit including instrumentation for determining the circulation rate of regenerated catalyst through said regenerated catalyst conduit;
• and
• a recycle catalyst controller for setting a position of the recycle catalyst control valve dependent on whether a relationship between the circulation rate of spent catalyst through said recycle catalyst conduit and the circulation rate of regenerated catalyst through said regenerated catalyst conduit meets a preset condition.

A process for the fluidized catalytic cracking of hydrocarbons, the process comprising:

• contacting blended catalyst with a hydrocarbon feed in a reaction zone;
• separating effluent from said reaction zone into vapor product and spent catalyst;
• recycling spent catalyst to said reaction zone;
• regulating circulation of said spent catalyst with a recycled catalyst control valve;
• determining a circulation rate of spent catalyst to said reaction zone;
• passing spent catalyst from said reaction zone to a regeneration zone;
• removing carbon from said spent catalyst in said regeneration zone to provide regenerated catalyst;
• passing regenerated catalyst from said regeneration zone to said reaction zone;
• determining a circulation rate of regenerated catalyst from said regeneration zone to said reaction zone;
• blending said regenerated catalyst with said spent catalyst in said reaction zone to provide said blended catalyst;
• determining whether a relationship between the circulation rate of spent catalyst to said reaction zone and the circulation rate of regenerated catalyst to said reaction zone meets a preset condition;
• and
• signaling an adjusted setting to the recycled catalyst control valve if said relationship between the circulation rate of spent catalyst and the circulation rate of regenerated catalyst does not meet the preset condition.