Method and system for controlling corrosion inhibitor feed

Abstract

A method for applying a corrosion inhibitor composition to a water stream in a water system includes determining a calcium phosphate saturation index of the water stream, determining at least one other parameter of the water stream, determining a dosage of the corrosion inhibitor composition based on a relationship between the dosage and the calcium phosphate saturation index including the at least one other parameter, and controlling administration of the corrosion inhibitor composition to the water stream based on the determined dosage.

What is claimed is: 
     
         1 . A method for applying a corrosion inhibitor composition to a water stream in a water system, the method comprising:
 determining a calcium phosphate saturation index of the water stream;   determining at least one other parameter of the water stream;   determining a dosage of the corrosion inhibitor composition based on a relationship between: (i) the dosage and (ii) the calcium phosphate saturation index and the at least one other parameter; and   controlling administration of the corrosion inhibitor composition to the water stream based on the determined dosage.   
     
     
         2 . The method according to  claim 1 , wherein the at least one other parameter is at least one of: temperature, pH, flow velocity, alkalinity, chloride concentration, and sulfate concentration. 
     
     
         3 . The method according to  claim 1 , wherein the corrosion inhibitor composition includes phosphate in an amount of less than 100 ppm. 
     
     
         4 . The method according to  claim 1 , wherein the corrosion inhibitor composition does not include phosphate. 
     
     
         5 . The method according to  claim 1 , wherein the corrosion inhibitor composition includes tin. 
     
     
         6 . The method according to  claim 1 , wherein the corrosion inhibitor composition includes a stannous salt selected from the group consisting of stannous sulfate, stannous bromide, stannous chloride, stannous oxide, stannous phosphate, stannous pyrophosphate, and stannous tetrafluroborate. 
     
     
         7 . The method according to  claim 1 , wherein the calcium phosphate saturation index is determined based on a calcium concentration and a phosphate concentration of the water stream and activity coefficients. 
     
     
         8 . The method according to  claim 7 , further comprising measuring alkalinity, chloride concentration, and sulfate concentration of the water stream. 
     
     
         9 . The method according to  claim 1 , further comprising calculating the relationship based on the calcium phosphate saturation index and the at least one other parameter of the water stream. 
     
     
         10 . The method according to  claim 1 , wherein the relationship is a saturation-dosage curve. 
     
     
         11 . The method according to  claim 1 , wherein the calcium phosphate saturation index and the at least one other parameter of the water stream are measured continuously. 
     
     
         12 . The method according to  claim 1 , wherein the calcium phosphate saturation index and the at least one other parameter of the water stream are measured in intervals. 
     
     
         13 . The method according to  claim 1 , wherein controlling administration of the corrosion inhibitor composition to the water stream includes controlling an amount of the corrosion inhibitor composition applied. 
     
     
         14 . The method according to  claim 1 , wherein controlling administration of the corrosion inhibitor composition to the water stream includes controlling a rate of application of the corrosion inhibitor composition. 
     
     
         15 . A water system comprising:
 at least one conduit through which a water stream flows;   an injection apparatus configured to inject corrosion inhibitor into the water stream, and   one or more processors configured to:
 determine a calcium phosphate saturation index of the water stream; 
 determine at least one other parameter of the water stream; 
 determine a dosage of a corrosion inhibitor composition based on a relationship between: (i) the dosage and (ii) the calcium phosphate saturation index and the at least one other parameter; and 
 send control signals to the injection apparatus to administer the determined dosage of corrosion inhibitor composition to the water stream. 
   
     
     
         16 . The water system of  claim 15 , wherein the at least one other parameter at least one of: temperature, pH, flow velocity, alkalinity, chloride concentration, and sulfate concentration. 
     
     
         17 . The water system of  claim 15 , wherein the calcium phosphate saturation index is determined based on a calcium concentration and a phosphate concentration of the water stream and activity coefficients. 
     
     
         18 . The water system of  claim 15 , wherein the relationship is a saturation-dosage curve.