Automation and Control of Energy Efficient Fluid Catalytic Cracking Processes for Maximizing Value Added Products

Abstract

With an aim to optimize propylene production, petroleum oil is catalytically cracked by contacting the oil with catalyst mixture consisting of a base cracking catalyst containing an stable Y-type zeolite and small amounts of rare-earth metal oxide, and an additive containing a shape-selective zeolite, in an up-flow type fluid catalytic cracking apparatus having a regeneration zone, a separation zone, and a stripping zone. According to this fluid catalytic cracking process, the production of light-fraction olefins such as propylene is maximized by applying appropriate process control, monitoring, and optimizing systems. The present invention provides mathematical process models, including: neural networks, statistical models and finite impulse models. These various mathematical process models are used in conjunction with advanced controllers and optimizing routines to calculate optimal settings for various process parameters. A microwave based system can also be employed for optimizing the performance of a stripping zone, which further optimizes catalyst regeneration. Process model and historical data to test a predictive system can provide early warning of potential performance degradation and equipment failure in the FCC unit, which decreases overall operating costs and increases plant safety.

1 . A process for the fluid catalytic cracking of a hydrocarbon feedstock comprising the steps of:
 (a) reacting the hydrocarbon feedstock with a catalyst mixture in a continuous fashion in a reaction zone under reaction conditions to form a produced mixture, the produced mixture comprising a product stream and a spent stream, the catalyst mixture comprising a base cracking catalyst, an ultra stable Y-type zeolite, an unreacted catalyst stream, and a regenerated catalyst stream, the catalyst mixture having a catalyst feed rate, the hydrocarbon feedstock having a hydrocarbon feedstock feed rate, the produced mixture having a produced mixture flow rate, wherein the reaction zone comprises:
 (i) flow rate sensors that are operable to monitor the hydrocarbon feedstock feed rate, the catalyst mixture feed rate, and the produced mixture flow rate; 
 (ii) temperature sensors that are operable to measure temperature within the reaction zone; 
 (iii) control valves that are integrated with a process control system such that the process control system is operable to modify an amount of closure of the control valves such that the hydrocarbon feedstock feed rate, the catalyst mixture feed rate and the produced mixture flow rate are subject to manipulation; and 
 (iv) a reactor; 
 wherein the reaction conditions comprise: 
 (i) an operating temperature; and 
 (ii) a contact time of approximately 0.5 to 3 seconds; 
   (b) separating the produced mixture into the product stream and the spent stream, the spent stream comprising spent catalyst and unreacted hydrocarbon;   (c) separating the spent stream into spent catalysts and unreacted hydrocarbon;   (d) transferring the spent catalysts to a regeneration zone, wherein the regeneration zone comprises a catalyst regenerator;   (e) regenerating the spent catalyst in the regeneration zone using an oxidation treatment to produce the regenerated catalyst stream, the regenerated catalyst stream having decreased amounts of adsorbed material as compared to the spent catalyst, the spent catalyst having a flow rate, and the spent catalyst having a residence time within the regeneration zone;   (f) recycling in a continuous fashion the regenerated catalyst stream into the reaction zone, the regenerated catalyst stream having a flow rate;   wherein the process has operating conditions, the operating conditions are operable to be controlled by the process control system, wherein the process control system has control parameters, the control parameters comprising the steps of:
 (i) obtaining predetermined process models that are operable to simulate operating conditions and produce simulated propylene production and simulated energy usage for the fluid catalytic cracking unit, wherein each predetermined process model is developed to simulate the fluid catalytic cracking unit for a specific range of the operating conditions; 
 (ii) monitoring feed data, products characterization data, and operating conditions; 
 (iii) selecting one of the predetermined process models based on the monitored feed data, monitored products characterization data and monitored operating conditions; 
 (iv) calculating simulated-optimized-operating conditions using the selected predetermined process model; 
 (v) adjusting the operating conditions to correspond with the simulated-optimized-operating-conditions; 
 (vi) measuring a propylene concentration in the product stream; 
 (vii) measuring energy usage of the fluid catalytic cracking unit; 
 (viii) comparing the propylene concentration with a predetermined propylene concentration range to determine whether the propylene concentration falls within the predetermined propylene concentration range; 
 (ix) comparing the energy usage of the fluid catalytic cracking unit with a predetermined energy usage range to determine whether the energy usage falls within the predetermined energy usage range; and 
 (x) adjusting the operating conditions until propylene concentration falls within the predetermined minimum propylene specification to yield optimized propylene production, wherein optimized propylene production is determined by maximizing a ratio of propylene production over energy usage, wherein energy usage is the energy consumed by the fluid catalytic cracking unit. 
   
   
   
       2 . The process of  claim 1 , wherein the operating conditions comprise the reaction zone temperature, the catalyst mixture feed rate, the hydrocarbon feedstock feed rate, the regeneration zone temperature, the recycled regenerated catalyst stream flow rate, the contact time within the reaction zone, the residence time within the regeneration zone, catalyst design, and a microwave frequency. 
   
   
       3 . The process of  claim 1 , further comprising a stripping, zone, wherein a majority of adsorbed material covering the spent catalysts is removed prior to transferring the spent catalysts to the regeneration zone. 
   
   
       4 . The process of  claim 3 , wherein the majority of adsorbed material covering the spent catalysts is removed using microwaves and/or sonic radiation. 
   
   
       5 . The process of  claim 1 , wherein the catalyst mixture is maintained in a fluidized state. 
   
   
       6 . The process of  claim 1 , wherein step (e) is performed using heat. 
   
   
       7 . The process of  claim 1 , wherein step (e) is performed using microwaves. 
   
   
       8 . The process of  claim 1 , wherein step (e) is performed using sonications. 
   
   
       9 . The process of  claim 1 , further comprising recycling the unreacted hydrocarbon to the reaction zone. 
   
   
       10 . The process of  claim 1 , wherein the hydrocarbon feedstock comprises a heavy fraction oil, such that the heavy fraction oil is characterized by having a boiling point, at atmospheric pressure, of about 250° C. and higher. 
   
   
       11 . The process of  claim 1 , wherein the hydrocarbon feedstock is selected from the group consisting of straight-run gas oil, vacuum gas oil, atmospheric residue, coker gas oil, petroleum oils obtained by hydrofining or hydrotreating atmospheric residue and gas oil, and combinations thereof. 
   
   
       12 . The process of  claim 1 , further comprising a cracker riser and a medium pore zeolite catalytic component. 
   
   
       13 . The process of  claim 1 , wherein the reactor within the reaction zone is an up flow-type reactor.