Method for measuring the percent consistency of pulp leaving a blow tank

Abstract

The measurement and control of the percent consistency of pulp leaving a blow tank in a pulp operation is improved by using digester data and additional temperature measurements. The percent consistency of pulp is determined by using the following data: 1) the temperature and relative amounts of dry pulp, liquid and dissolved solids in a blown mixture entering the blow tank; 2) the temperature and amount of dissolved solids in a first stage filtrate liquor; and 3) the temperature of a diluted pulp mixture leaving the blow tank. Once the percent consistency of pulp is accurately measured, this value is then used to control the tonnage rate of pulp entering a first washer in a pulp washing operation.

What is claimed is:  
     
         1 . A process for measuring the consistency of pulp in a pulp operation, said pulp operation comprising at least a blow tank, a first washer, and a first stage filtrate tank, comprising 
 a) determining a percent dissolved solids in a first stage filtrate liquor entering said blow tank from said first stage filtrate tank;    b) measuring a filtrate temperature of said first stage filtrate liquor;    c) determining the relative amounts of dry pulp, liquid and dissolved solids in a blown mixture going into said blow tank;    d) determining a blown mixture temperature of said blown mixture going into said blow tank;    e) measuring a pulp mixture temperature from a diluted pulp mixture leaving said blow tank; and    e) calculating a percent consistency of pulp in said diluted pulp mixture using said percent dissolved solids in said first stage filtrate liquor, said filtrate temperature, said relative amounts of dry pulp, liquid and dissolved solids in said blown mixture, said blown mixture temperature, and said pulp mixture temperature;    f) calculating a calculated temperature of said diluted pulp mixture using said percent dissolved solids in said first stage filtrate liquor, said filtrate temperature, said relative amounts of dry pulp, liquid and dissolved solids in said blown mixture, said blown mixture temperature, and said pulp mixture temperature; and    g) adding an additional amount of said first stage filtrate liquor or said blown mixture to increase said percent consistency of pulp by an incremental amount; and    h) determining a percent consistency of pulp by repeating steps a)-g) until said calculated temperature is greater than said pulp mixture temperature.    
     
     
         2 . The method of  claim 1 , further comprising measuring a flow rate of said diluted pulp mixture.  
     
     
         3 . The method of  claim 2 , further comprising determining a tonnage rate of pulp in said diluted pulp mixture using said percent consistency of pulp and said flow rate of said diluted pulp mixture.  
     
     
         4 . The method of  claim 1 , wherein said filtrate temperature and said pulp mixture temperature are measured within 0.005 degrees centigrade.  
     
     
         5 . The method of  claim 1 , wherein said percent dissolved solids in said first stage filtrate liquor is constant.  
     
     
         6 . The method of  claim 1 , wherein said filtrate temperature is constant.  
     
     
         7 . The method of  claim 1 , further comprising measuring a second pulp mixture temperature after the introduction of a second diluting liquor to said diluted pulp mixture leaving said blow tank.  
     
     
         8 . The method of  claim 7 , wherein said second diluting liquor is said first stage filtrate liquor.  
     
     
         9 . The method of  claim 7 , further comprising determining a temperature and a percent solids in said second diluting liquor.  
     
     
         10 . The method of  claim 7 , further comprising measuring a flow rate of said diluted pulp mixture.  
     
     
         11 . The method of  claim 10 , further comprising determining a tonnage rate of pulp in said diluted pulp mixture using said percent consistency of pulp and said flow rate of said diluted pulp mixture.  
     
     
         12 . The method of  claim 7 , wherein said filtrate temperature, said pulp mixture temperature, and said second pulp mixture temperature are measured within 0.005 degrees centigrade.  
     
     
         13 . The method of  claim 7 , wherein said percent dissolved solids in said first stage filtrate liquor is constant.  
     
     
         14 . The method of  claim 7 , wherein said filtrate temperature is constant.