System and method for controlling a processor including a digester utilizing time-based assessments

Abstract

A system for controlling a processor having at least one sampling port connected to a stage of the processor in order to sample a reactant product from the processor. The system includes a controller configured to control a processing parameter of the processor based on measurements of at least one property of the reactant product such that changes to the processing parameter maintain a target value for the at least one property of the reactant product. The system further includes a dead time compensator. The dead time compensator is configured, based upon a prescribed dead time related to a time before at least one effect of at least one change to the processing parameter is fully realized, to evaluate the reactant product to determine if the effect has been realized at a plurality of sequential times offset from the dead time.

1 . A method for controlling a processor, comprising:
 analyzing a reactant product from the processor;   determining based on at least one property of the reactant product a change to at least one processing parameter of the processor;   changing the at least one processing parameter of the processor; and   evaluating, following a prescribed process dead time related to a time before at least one effect of at least one of said change to the at least one processing parameter is fully realized in said at least one property of the reactant product, changes to the at least one property for subsequent reactant products sampled at a multiplicity of times offset about the prescribed process dead time.   
     
     
         2 . The method of  claim 1 , wherein the evaluating comprises:
 evaluating a reactor process susceptible to disturbances in plug flow conditions.   
     
     
         3 . The method of  claim 2 , wherein said evaluating a reactor process susceptible to disturbances in plug flow conditions evaluates disturbances due to channeling whereby said reactant product prematurely flows into subsequent stages of the processor. 
     
     
         4 . The method of  claim 1 , wherein the analyzing comprises:
 analyzing the reactant product from any of a pulp digester, an oxygen delignification processor, a bleaching processor, and a causticizer.   
     
     
         5 . The method of  claim 1 , wherein the analyzing comprises:
 analyzing the reactant product of said processor from at least one of several sequential stages of said processor.   
     
     
         6 . The method of  claim 5 , wherein the analyzing comprises:
 analyzing the reactant product of a pulp digester to determine at least one of a Kappa number and a residual alkali concentration.   
     
     
         7 . The method of  claim 1 , wherein the determining comprises:
 determining a prescribed change to the at least one processing parameter based on a rule base.   
     
     
         8 . The method of  claim 7 , wherein the determining comprises:
 evaluating error deviations from at least two properties of the reactor product; and   changing at least one of said processing parameters based on at least a bifurcated error state of the at least two properties of the reactant product.   
     
     
         9 . The method of  claim 1 , wherein the determining comprises:
 determining a prescribed change to the at least one processing parameter based on a model base.   
     
     
         10 . The method of  claim 1 , wherein the changing comprises:
 changing the at least one processing parameter in at least one of a step-change and a ramped change.   
     
     
         11 . The method of  claim 1 , wherein the changing comprises:
 changing the at least one processing parameter in a time less than the prescribed process dead time.   
     
     
         12 . The method of  claim 1 , further comprising:
 revising at least one of a rule-base or a model-base based on said changes to said at least one property evaluated by said dead-time compensator prior to repeating said determining step.   
     
     
         13 . A computer program product, comprising:
 a computer storage medium and a computer program code embedded in the computer storage medium for causing a computer to control a processor, said computer program code comprising,   a first computer program component configured to analyze a reactant product from the processor,   a second computer program component configured to determine based on at least one property of the reactant product a change to at least one processing parameter of the processor,   a third computer code program component configured to change the at least one processing parameter of the processor, and   a fourth computer code program component configured to evaluate, following a prescribed process dead time related to a time before at least one effect of at least one of said change to the at least one processing parameter is fully realized in said at least one property of the reactant product, changes to the at least one property for subsequent reactant products sampled at a multiplicity of times offset about the prescribed process dead time.   
     
     
         14 . A method for controlling a processor, comprising:
 analyzing a reactant product from the processor;   determining based on at least two properties of the reactant product a change to at least one processing parameter of the processor; and   changing said at least one processing parameter based on at least a bifurcated error state of the at least two properties of the reactant product.   
     
     
         15 . The method of  claim 14 , wherein the analyzing comprises:
 analyzing the reactant product from any of a pulp digester, an oxygen delignification processor, a bleaching processor, and a causticizer.   
     
     
         16 . The method of  claim 14 , wherein the analyzing comprises:
 analyzing the reactant product of said processor from at least one of several sequential stages of said processor.   
     
     
         17 . The method of  claim 16  wherein the analyzing comprises:
 analyzing the reactant product of a pulp digester to determine at least one of a Kappa number and a residual alkali concentration.   
     
     
         18 . The method of  claim 14 , wherein the determining comprises:
 determining a prescribed change to the at least one processing parameter based on a rule base.   
     
     
         19 . The method of  claim 14 , wherein the determining comprises:
 determining a prescribed change to the at least one processing parameter based on a model base.   
     
     
         20 . The method of  claim 14 , wherein the changing comprises:
 changing the at least one processing parameter in at least one of a step-change and a ramped change.   
     
     
         21 . The method of  claim 14 , wherein the changing comprises:
 changing the at least one processing parameter in a time less than a prescribed process dead time.   
     
     
         22 . The method of  claim 15 , wherein the changing comprises:
 maintaining at least one of a Kappa number representative of a cellulose fiber concentration and an alkalinity of the digested pulp product within said target values.   
     
     
         23 . The method of  claim 22  wherein the changing comprises:
 controlling an H-factor of the digester and at least one of an input alkali dosage concentration and an alkali/wood-input ratio to the digester, said H-factor derived from a time-integrated rate constant for the pulp or paper product in the digester based on a temperature and a throughput of the digester.   
     
     
         24 . The method of  claim 23 , wherein said controlling comprises:
 increasing at least one of said H-factor, said input alkali dosage concentration, and said alkali/wood-input ratio when said Kappa number is above a target value.   
     
     
         25 . The method of  claim 23 , wherein said controlling comprises:
 decreasing at least one of said H-factor, said input alkali dosage concentration, and said alkali/wood-input ratio when said Kappa number of the digested pulp product is below a target value.   
     
     
         26 . The method of  claim 23 , wherein said controlling, when a residual alkalinity of the digested pulp product is below a target value, increases said input alkali dosage concentration or said alkali/wood-input ratio or decreases said H-factor. 
     
     
         27 . The method of  claim 23 , wherein said controlling, when a residual alkalinity of the digested pulp product is above a target value, decreases said input alkali dosage concentration or said alkali/wood-input ratio or increases said H-factor. 
     
     
         28 . The method of  claim 15 , wherein said changing controls said pulp digester based on the following bifurcated relationship: 
       
         
           
                 
                 
                 
                 
                 
               
                     
                     
                 
                     
                   Blow Kappa 
                   Residual Alkali 
                   H-factor 
                   Alkali Dosage 
                 
                     
                   Error 
                   Error 
                   Correction 
                   Correction 
                 
                     
                     
                 
                     
                   High 
                   High 
                   ++ 
                   OK 
                 
                     
                   High 
                   OK 
                   + 
                   + 
                 
                     
                   High 
                   Low 
                   OK 
                   ++ 
                 
                     
                   OK 
                   High 
                   + 
                   − 
                 
                     
                   OK 
                   OK 
                   OK 
                   OK 
                 
                     
                   OK 
                   Low 
                   − 
                   + 
                 
                     
                   Low 
                   High 
                   OK 
                   −− 
                 
                     
                   Low 
                   OK 
                   − 
                   − 
                 
                     
                   Low 
                   Low 
                   −− 
                   OK 
                 
                     
                     
                 
             
                
                
                
                
               
               
                
                
                
                
                
                
                
                
                
                
               
            
           
         
         where blow Kappa error is representative of an error from an expected cellulose fiber concentration in a discharge section of the digester, residual alkali error is representative of an error from an expected residual alkali concentration, H-factor correction is based on a time-integrated rate constant for the pulp or paper product in the digester based on a temperature and a throughput of the digester, alkali dosage correction is based on a measured addition of alkali to be added to the digester, “+” and “++” indicate an increase and a stronger increase to the corrections, “−” and “−−” indicate a decrease and a stronger decrease to the corrections, “OK” refers to an expected value of the residual alkali concentration or the expected cellulose fiber concentration, “High” refers to deviations above the expected values which are predetermined to exceed process tolerances, and “Low” refers to deviations below the expected values which are predetermined to be below process tolerances. 
       
     
     
         29 . A computer program product, comprising:
 a computer storage medium and a computer program code embedded in the computer storage medium for causing a computer to control a processor, said computer program code comprising,   a first computer program component configured to analyze a reactant product from the processor;   
       a second computer program product configured to determine based on at least two properties of the reactant product a change to at least one processing parameter of the processor; and a third computer program product configured to change said at least one processing parameter based on at least a bifurcated error state of the at least two properties of the reactant product.