Automatic control system and method for air separation units

Abstract

A method for automatically setting a target production level for at least one air separation unit in a network of air separation units. Each air separation unit has a plurality of field elements and at least one regulatory controller associated with one of the field elements, and has an energy usage level corresponding to a level of production. The method includes receiving a production level requirement for the network of air separation units and generating a production target level for at least one of the air separation units which minimizes and/or optimizes the sum of the ASU energy usage levels. The ASUs then can automatically ramp the plant production to the appropriate production target levels via the use of advanced process control (multivariable process controllers and/or advanced feedforward controllers), advanced regulatory control, and regulatory control means. In another embodiment, the invention is a network of air separation units, including at least two air separation units in fluid communication with a pipeline and a control system in control communication with the air separation units for automatically setting the ASU target production levels. Each air separation unit has a plurality of field elements, at least one production level and an energy usage level corresponding to the production level. The control system includes a receiver for receiving inputs from the at least two air separation units, and a supervisory controller which generates production target levels for sending to each air separation unit, the production target levels being representative of a network production target level and a network energy usage level.

What is claimed is:  
     
         1 . A method of automatically setting a target production level for at least one air separation unit in a network of air separation units, each air separation unit including a plurality of field elements and at least one regulatory controller associated with one of the field elements, and having an energy usage level corresponding to a level of production, comprising: 
 receiving a production level requirement for the network of air separation units, and    generating a production target level for at least one of the air separation units which minimizes the sum of the energy usage levels.    
     
     
         2 . A method as in  claim 1 , further comprising: 
 changing the level of production for one of the at least one air separation units until it is about equal to the generated production target level for the air separation unit.    
     
     
         3 . A method as in  claim 2 , wherein the changing the production level comprises: 
 using an advanced process controller to set a setpoint associated with at least one of the plurality of field elements.    
     
     
         4 . A method as in  claim 3 , wherein the advanced process controller is an advanced feedforward controller.  
     
     
         5 . A method as in  claim 3 , wherein the advanced process controller controller is an multivariable predictive controller.  
     
     
         6 . A method as in  claim 3 , wherein the advanced process controller includes an advanced feedforward controller and a multivariable predictive controller.  
     
     
         7 . A method as in  claim 3 , further comprising: 
 monitoring the advanced process controller to determine whether said advanced process controller is operational.    
     
     
         8 . A method as in  claim 7 , further comprising: 
 identifying an advanced process controller if it is non-operational or partially-operational.    
     
     
         9 . A method as in  claim 8 , further comprising: 
 determining an advance process controller service factor.    
     
     
         10 . A method as in  claim 3 , further comprising: 
 controlling at least one of a plurality of field elements in an air separation unit.    
     
     
         11 . A method as in  claim 10 , wherein the controlling includes using a model based adaptive controller to control the field element.  
     
     
         12 . A method as in  claim 10 , wherein the controlling includes using a model free adaptive controller to control the field element.  
     
     
         13 . A method as in  claim 10 , wherein the controlling includes using a regulatory controller to control the field element.  
     
     
         14 . A control system for automatically setting the target production level for at least one air separation unit in a network of air separation units, each air separation unit including a plurality of field elements and having at least one production level and an energy usage level corresponding to the production level, comprising: 
 a receiver for receiving inputs from the air separation units; and    a supervisory controller for generating a production target level for at least one of the air separation units.    
     
     
         15 . A control system as in  claim 14 , wherein the inputs include the energy usage levels and the production levels of the air separation units.  
     
     
         16 . A control system as in  claim 14 , further comprising: 
 an advanced process controller for changing the production level of one of the at least one air separation units until it is about equal to the generated production target level for the air separation unit.    
     
     
         17 . A control system as in  claim 16 , wherein the advanced process controller generates a setpoint associated with at least one of the plurality of field elements.  
     
     
         18 . A control system as in  claim 17 , wherein the advanced process controller is an advanced feedforward controller.  
     
     
         19 . A control system as in  claim 17 , wherein the advanced process controller is an multivariable predictive controller.  
     
     
         20 . A control system as in  claim 17 , wherein the advanced process controller includes an advanced feedforward controller and a multivariable predictive controller.  
     
     
         21 . A control system as in  claim 17 , further comprising a monitoring system for monitoring the advanced process controller.  
     
     
         22 . A control system as in  claim 17 , further comprising: 
 an advanced regulatory controller for regulating at least one of the plurality of field elements in an air separation unit.    
     
     
         23 . A control system as in  claim 22 , wherein the advanced regulatory controller is a model-based adaptive controller.  
     
     
         24 . A control system as in  claim 22 , wherein the advanced regulatory controller is a model free adaptive controller.  
     
     
         25 . A control system as in  claim 22 , further comprising: 
 a regulatory controller for controlling a field element,    wherein said regulatory controller is a proportional plus integral plus derivative controller, a gap controller, a deadband controller, or a hand indicating controller.    
     
     
         26 . A network of air separation units, comprising: 
 at least two air separation units, each air separation unit including a plurality of field elements and having at least one production level and an energy usage level corresponding to the production level;    a pipeline in fluid communication with the at least two air separation units;    a control system for automatically setting the target production level for the at least two air separation units, the control system in control communication with the at least two air separation units and including    a receiver for receiving inputs from the at least two air separation units, and    a supervisory controller for generating data representative of a network production target level and a network energy usage level for the at least two air separation units.    
     
     
         27 . A network as in  claim 26 , further comprising: 
 an Operational Control Center for generating a network production level target, and wherein data includes a production target level for at least one of the air separation units.