Method for regulating particle transfer rates

A hydrocarbon conversion process for contacting a hydrocarbon-containing feedstream with a particulate catalyst at hydrocarbon conversion conditions in a reaction zone, deactivating said catalyst in said reaction zone, passing said catalyst from a first bottom location in said reaction zone and to a first top location in a regeneration zone, reactivating said catalyst in said regeneration zone, and passing said catalyst from a second bottom location in said regeneration zone to a second top location in said reaction zone, said process comprising controlling the transport rate of said catalyst from said second bottom location to said second top location at a rate that does not exceed a maximum change rate for said hydrocarbon conversion process, said method comprising:

• a) passing said catalyst downwardly from said second bottom location to a surge zone;
• b) passing said catalyst downwardly from said surge zone to a fluid-controlled valve;
• c) regulating the flow of a fluid to said fluid-controlled valve to deliver said catalyst to a lift conduit;
• d) conveying said catalyst upwardly through said lift conduit with said fluid and discharging said catalyst to said second top location at a transport rate of said catalyst and measuring an actual value of the pressure difference across at least a portion of said lift conduit;
• e) decreasing the actual volume of said catalyst in said surge zone to below a control volume of said catalyst in said surge zone by said passing of said catalyst from said surge zone;
• f) when the actual volume of said catalyst in said surge zone is below said control volume in Step (e), adding said catalyst to said surge zone, thereby increasing the actual volume of said catalyst in said surge zone to more than said control volume;
• g) after adding said catalyst to said surge zone in Step (f), allowing the actual volume of said catalyst in said surge zone to decrease below said control volume by said passing of said catalyst from said surge zone;
• h) determining a first average value of said pressure difference during a first time period from the time when the actual volume of said catalyst in said surge zone decreased below said control volume of said catalyst in said surge zone in Step (e) until the time when the actual volume of said catalyst in said surge zone decreased below said control volume of said catalyst in said surge zone in Step (g);
• i) determining a first average addition rate of said catalyst to said surge zone during said first time period by dividing the amount of catalyst added to said surge zone in Step (f) by said first time period;
• j) establishing a first final value of said pressure difference as a function of a target addition rate of said catalyst, said first average addition rate of said catalyst, and said first average value of said pressure difference;
• k) increasing or decreasing said desired value of said pressure difference at a change rate that does not exceed 20 percent of the maximum value of said pressure difference per minute;
• l) comparing said desired value of said pressure difference after said increasing or decreasing with the actual value of said pressure difference and updating a control signal in response to the difference between said desired value after said increasing or decreasing and said actual value to generate an updated control signal;
• m) employing said updated control signal to actuate a valve operably located so as to control the flow of said transport stream to said fluid-controlled valve;
• and
• n) repeating Steps (k), (l), and (m) until said desired value equals said first final value of said pressure difference.