Estimation and control in the wet end using CO2

Abstract

A method for controlling the CO 2 addition in a wet end process utilizing CO 2 addition is disclosed. The method includes combining a papermaking composition and CO 2 to create a CO 2 -enriched papermaking composition, measuring or estimating at least one electrical property of either the papermaking composition or of the CO 2 -enriched papermaking composition, and controlling the rate of addition of CO 2 to maintain the at least one electrical property within a pre-selected range of values.

We claim:  
     
         1 . In a wet end process utilizing CO 2  addition, a method for controlling the CO 2  addition comprising, in combination: 
 combining a papermaking composition and CO2 to create a CO2-enriched papermaking composition;    measuring or estimating at least one electrical property of either the papermaking composition or of the CO2-enriched papermaking composition; and    controlling the rate of addition of CO2 to maintain the at least one electrical property within a preselected range of values.    
     
     
         2 . The method of  claim 1 , wherein the at least one electrical property is selected from the group consisting of ZP, CD and ion concentration.  
     
     
         3 . The method of  claim 2 , wherein the electrical property is estimated by measuring at least one property of either the papermaking composition or the CO 2  -enriched papermaking composition and estimating the ZP.  
     
     
         4 . The method of  claim 3 , the electrical property being ZP.  
     
     
         5 . The method of  claim 3 , the electrical property being CD.  
     
     
         6 . The method of  claim 3 , the electrical property being ion concentration.  
     
     
         7 . The method of  claim 3 , wherein the at least one property is selected from the group consisting of flowrate, CD, ZP, ion concentration, Cy, pH, conductivity and alkalinity.  
     
     
         8 . The method of  claim 4  wherein the at least one property is selected from the group consisting of flowrate, CD, ion concentration, Cy, pH, conductivity and alkalinity.  
     
     
         9 . The method of  claim 5  wherein the at least one property is selected from the group consisting of flowrate, ZP, ion concentration, Cy, pH, conductivity and alkalinity.  
     
     
         10 . The method of  claim 6  wherein the at least one property is selected from the group consisting of flowrate, CD, ZP, Cy, pH, conductivity and alkalinity.  
     
     
         11 . The method of  claim 3 , wherein the at least one electrical property is estimated in the papermaking composition.  
     
     
         12 . The method of  claim 3 , wherein the at least one electrical property is measured in the CO 2 -enriched papermaking composition.  
     
     
         13 . The method of  claim 11 , wherein the at least one electrical property is estimated in the papermaking composition.  
     
     
         14 . The method of  claim 12 , wherein the at least one electrical property is estimated in the papermaking composition.  
     
     
         15 . The method of  claim 11 , wherein the at least one electrical property is measured in the CO 2 -enriched papermaking composition.  
     
     
         16 . The method of  claim 12 , wherein the at least one electrical property is measured in the CO 2 -enriched papermaking composition.  
     
     
         17 . In a wet end process utilizing CO 2  addition, a method for controlling the CO 2  addition comprising, in combination: 
 combining a papermaking composition and CO 2  to create a CO 2 -enriched papermaking composition;    measuring or estimating at least one property of the papermaking composition and generating papermaking composition property data, and providing the papermaking composition property data to an advanced controller constructed and arranged to receive the papermaking composition property data and generate a papermaking composition output component;    measuring or estimating at least one property of the CO 2 -enriched papermaking composition, generating CO 2 -enriched papermaking composition property data and providing the CO 2 -enriched papermaking composition property data to a feedback controller constructed and arranged to receive the CO 2 -enriched papermaking composition property data and generate an outlet controller output component;    compensating the feedback controller by analyzing the inlet controller output component and the outlet controller output component; and    controlling the inlet flow of CO 2  to maintain at least one property of the CO 2 -enriched papermaking composition within a preselected range of values.    
     
     
         18 . The method of  claim 17 , wherein the at least one property of the papermaking composition is selected from the group consisting of flowrate, ZP, CD, ion concentration, Cy, pH, conductivity and alkalinity.  
     
     
         19 . The method of  claim 17 , wherein the at least one property of the CO 2 -enriched papermaking composition is selected from the group consisting of ZP, CD and ion concentration.  
     
     
         20 . The method of  claim 18 , wherein the at least one property of the CO 2 -enriched papermaking composition is selected from the group consisting of ZP, CD and ion concentration.  
     
     
         21 . The method of  claim 17 , wherein the advanced controller comprises a feed forward controller.  
     
     
         22 . The method of  claim 21 , wherein the at least one property of the papermaking composition is selected from the group consisting of flowrate, ZP, CD, ion concentration, Cy, pH, conductivity and alkalinity and the at least one property of the CO 2 -enriched papermaking composition is selected from the group consisting of ZP and CD.  
     
     
         23 . In a wet end process utilizing CO 2  addition, a method for controlling the CO 2  addition comprising, in combination: 
 combining a papermaking composition and CO 2  to create a CO 2 -enriched papermaking composition;    measuring or estimating at least one property of the papermaking composition selected from the group consisting of flowrate, ZP, CD, Cy, pH, conductivity, ion concentration and alkalinity, generating papermaking composition property data and providing the papermaking composition property data to an advanced controller constructed and arranged to receive the papermaking composition property data and generate an inlet controller output component;    measuring or estimating at least one property of the CO 2 -enriched papermaking composition selected from the group consisting of ZP, CD and salt ion concentration and generating CO 2 -enriched papermaking composition property data, providing the CO 2 -enriched papermaking composition property data to a feedback controller constructed and arranged to receive the CO 2 -enriched papermaking composition property data and generate an outlet controller output component;    compensating the feedback controller by analyzing the inlet controller output component and the outlet controller output component; and    controlling the inlet flow of CO 2  to maintain at least one property of the CO 2 -enriched papermaking composition within a preselected range of values.    
     
     
         24 . The method of  claim 23 , wherein the advanced controller comprises a feed forward controller.  
     
     
         25 . The method of  claim 24  wherein the feed forward controller uses predictive control.  
     
     
         26 . The method of  claim 24  wherein the feed forward controller uses inferential control.  
     
     
         27 . In a wet end process utilizing CO 2  addition, a method for controlling the CO 2  addition comprising, in combination: 
 combining a papermaking composition and CO 2  to create a CO 2 -enriched papermaking composition;    on-line measuring at least one property of the papermaking composition selected from the group consisting of flowrate, ZP, CD, ion concentration, Cy, pH, conductivity and alkalinity, generating papermaking composition property data and providing the papermaking composition property data to an observer;    on-line measuring at least one property of the CO 2 -enriched papermaking composition selected from the group consisting of flowrate, ZP, CD, ion concentration, Cy, pH, conductivity and alkalinity, generating CO 2 -enriched papermaking composition property data and providing the CO 2 -enriched papermaking composition property data to the observer;    the observer receiving the papermaking composition property data and the CO 2 -enriched papermaking composition property data and generating at least one estimated electrical property of the CO 2 -enriched papermaking composition selected from the group consisting of ZP, CD and ion concentration, the observer generating estimated electrical property data for the at least one electrical property and transmitting the papermaking composition property data, the CO 2 -enriched papermaking composition property data and the estimated electrical property data to a controller; and    the controller controlling the inlet flow of CO 2  to maintain at least one electrical property of the CO 2 -enriched papermaking composition within a preselected range of values.    
     
     
         28 . The method of  claim 27 , the observer comprising a model.  
     
     
         29 . The method of  claim 27 , the papermaking composition property data, the CO 2 -enriched papermaking composition property data and the estimated electrical property data being incorporated into a software sensor.  
     
     
         30 . The method of  claim 28 , the papermaking, composition property data, the CO 2 -enriched papermaking composition property data and the estimated electrical property data being incorporated into a software sensor.  
     
     
         31 . The method of  claim 28 , the observer further refining the estimated electrical property data by analyzing inaccuracies presented by the model.  
     
     
         32 . The method of  claim 28 , the observer further refining the estimated electrical property data by analyzing expected errors in measurement.  
     
     
         33 . The method of  claim 28 , the observer further refining the estimated electrical property data by analyzing inaccuracies presented by the model and by analyzing expected errors in measurement.  
     
     
         34 . The method of  claim 30 , the observer further refining the estimated electrical property data by analyzing inaccuracies presented by the model.  
     
     
         35 . The method of  claim 30 , the observer further refining the estimated electrical property data by analyzing expected errors in measurement.  
     
     
         36 . The method of  claim 30 , the observer further refining the estimated electrical property data by analyzing inaccuracies presented by the model and by analyzing expected errors in measurement.  
     
     
         37 . The method of  claim 28  further comprising using the estimated electrical property data to evaluate a set point and implement a real time closed loop control.  
     
     
         38 . The method of  claim 30  further comprising using the estimated electrical property data to evaluate a set point and implement a real time closed loop control.  
     
     
         39 . The method of  claim 36  further comprising using the estimated electrical property data to evaluate a set point and implement a real time closed loop control.  
     
     
         40 . In a wet end process utilizing CO addition, a method for controlling the CO 2  addition comprising, in combination: 
 combining a papermaking composition and CO 2  to create a CO 2 -enriched papermaking composition;    on-line measuring at least one property of the papermaking composition selected from the group consisting of flowrate, ZP, CD, ion concentration, Cy, pH, conductivity and alkalinity, generating papermaking composition property data and providing the papermaking composition property data to an observer;    on-line measuring at least one property of the CO 2 -enriched papermaking composition selected from the group consisting of flowrate, ZP, CD, ion concentration, Cy, pH, conductivity and alkalinity, generating CO 2 -enriched papermaking composition property data and providing the CO 2 -enriched papermaking composition property data to the observer;    the observer receiving the papermaking composition property data and the CO 2 -enriched papermaking composition property data and using a model to generate at least one estimated electrical property of the CO 2 -enriched papermaking composition selected from the group consisting of ZP, CD and ion concentration;    the observer refining the estimate for the at least one electrical property by analyzing inaccuracies presented by the model and by analyzing expected errors in measurement;    the observer transmitting the papermaking composition property data, the CO 2 -enriched papermaking composition property data and the refined estimated electrical property data to a controller; and    the controller controlling the inlet flow of CO 2  to maintain at least one electrical property of the CO 2 -enriched papermaking composition within a preselected range of values.