Turndown thermocompressor design for continuous catalyst recovery

Abstract

Systems and processes for regenerating catalyst are provided herein that include a catalyst regeneration tower having a cooling zone that receives a catalyst cooling stream generated by a cooling gas loop. The systems and processes include a first thermocompressor that utilizes a first motive vapor and a second thermocompressor that utilizes a second motive vapor in order to provide the catalyst cooling stream to the regeneration tower. The second thermocompressor operates in parallel with the first thermocompressor. The first thermocompressor can utilize combustion air as the motive vapor. The second thermocompressor can utilize nitrogen as the motive vapor.

1 . A catalyst regeneration system, the system comprising:
 a catalyst regeneration tower including a cooling zone that receives a catalyst cooling stream;
 a first thermocompressor that utilizes a first motive vapor; and 
 a second thermocompressor in parallel with the first thermocompressor that utilizes nitrogen as a motive vapor; and 
 one or more valves that selectively direct a cooled stream to at least one of the first thermocompressor or the second thermocompressor to produce the catalyst cooling stream. 
   
     
     
         2 . The catalyst regeneration system of  claim 1 , further comprising:
 an air heater that receives a first gas stream removed from the regeneration tower and produces a heated first gas stream; and   a cooling zone cooler that receives at least a portion of the heated first gas stream and produces the cooled stream.   
     
     
         3 . The catalyst regeneration system of  claim 2 , wherein the catalyst regeneration tower includes a combustion zone, a halogenation zone, a drying zone, and a cooling zone. 
     
     
         4 . The catalyst regeneration system of  claim 3 , wherein the first gas stream is removed from the cooling zone  112  of the regeneration tower. 
     
     
         5 . The catalyst regeneration system of  claim 1 , wherein the first motive vapor is supplied to the first thermocompressor through a dryer. 
     
     
         6 . The catalyst regeneration system of  claim 5 , wherein the first motive vapor contains oxygen and nitrogen. 
     
     
         7 . The catalyst regeneration system of  claim 1 , wherein the nitrogen is provided to the second thermocompressor at a higher pressure than the first motive vapor is provided to the first thermocompressor. 
     
     
         8 . The catalyst regeneration system of  claim 7 , wherein the pressure of the nitrogen is about 30 psi to about 300 psi higher than the pressure of the first motive vapor. 
     
     
         9 . The catalyst regeneration system of  claim 1 , wherein the second thermocompressor operates at a higher ratio of load gas to motive gas than the first thermocompressor. 
     
     
         10 . The catalyst regeneration system of  claim 1 , wherein the nitrogen has a flow rate that is controlled to maintain the oxygen content in the halogenation zone at a level of above about 18%.