Automatic control of a multiple-effect evaporator

Claim 1

Apparatus comprising: a multiple-effect evaporator having at least a first effect and a second effect for concentrating a dilute solution, said multiple-effect evaporator having a steam chest associated with each effect; means for supplying steam from an external source to said steam chest of said first-effect for use as a heating fluid; means for passing a feed mixture comprising a dilute solution of at least one dissolved solid into said multiple-effect evaporator; means for withdrawing a liquid product stream from said multiple-effect evaporator, said liquid product stream having an increased concentration of said at least one dissolved solid with respect to said feed mixture; means for establishing a first signal representative of the actual boiling point rise of the liquid in said first-effect; means for establishing a second signal representative of the actual temperature of the liquid in said first-effect; means for establishing a third signal representative of the concentration of said at least one dissolved solid in the liquid in said first-effect based on the value of said first signal, and the value of said second signal; means for establishing a fourth signal representative of the steam flow to said steam chest of said first-effect; means for establishing a fifth signal representative of the boiling point rise of the liquid in said second-effect; means for establishing a sixth signal representative of the actual temperature of the liquid in said second-effect; means for establishing a seventh signal representative of the concentration of said at least one dissolved solid in the liquid in said second-effect based on the value of said fifth signal and said sixth signal; means for establishing an eighth signal representative of the feed flow to said first-effect based on the value of said third signal, said fourth signal, and said seventh signal; and means for manipulating the feed flow to said first-effect in response to said eighth signal wherein the manipulation of the feed flow to said first-effect in response to said eighth signal results in the feed flow to said first-effect being proportional to the concentration represented by said third signal, the steam flow represented by said fourth signal and the concentration represented by said seventh signal, to thereby maintain a solute balance for said first-effect.

Claim 9

A method for controlling a multiple effect evaporator having at least a first-effect and a second-effect, which increases the concentration of a dilute solution of at least one dissolved solid by heating said dilute solution in multiple evaporation zones, wherein said dilute solution is continuously introduced into said multiple-effect evaporator and a concentrated solution with respect to said dilute solution is continuously withdrawn from said mulitple effect evaporator, said method comprising the steps of: establishing a first signal representative of the actual boiling point rise of the liquid in said first-effect; establishing a second signal representative of the actual temperature of the liquid in said first-effect; establishing a third signal representative of the concentration of said at least one dissolved solid in the liquid in said first-effect based on the value of said first signal and the value of said second signal; establishing a fourth signal representative of the steam flow to said steam chest of said first-effect; establishing a fifth signal representative of the boiling point rise of the liquid in said second-effect; establishing a sixth signal representative of the actual temperature of the liquid in said second effect; establishing a seventh signal representative of the concentration of said at least one dissolved solid in the liquid in said second-effect based on the value of said fifth signal, and said sixth signal; establishing an eighth signal representative of the feed flow to said first-effect based on the value of said third signal, said fourth signal and said seventh signal; and manipulating the feed flow to said first-effect in response to said eighth signal wherein the manipulation of feed flow to said first-effect in response to said eighth signal results in the feed flow to said first effect being proportional to the concentration represented by said third signal, the steam flow represented by said fourth signal, and the concentration represented by said seventh signal to thereby maintain a solute balance for the first-effect.

Claim 10

A method for controlling a multiple effect evaporator having at least a first-effect and a second-effect, which increases the concentration of a dilute solution of at least one dissolved solid by heating said dilute solution in multiple evaporation zones, wherein said dilute solution is continuously introduced into said multiple-effect evaporator and a concentrated solution with respect to said dilute solution is continuously withdrawn from said mulitple effect evaporator, said method comprising the steps of: establishing a first signal representative of the actual boiling point rise of the liquid in said first-effect; establishing a second signal representative of the actual temperature of the liquid in said first-effect; establishing a third signal representative of the concentration of said at least one dissolved solid in the liquid in said first-effect based on the value of said first signal and the value of said second signal; establishing a fourth signal representative of the steam flow to said steam chest of said first-effect; establishing a fifth signal representative of the boiling point rise of the liquid in said second-effect; establishing a sixth signal representative of the actual temperature of the liquid in said second effect; establishing a seventh signal representative of the concentration of said at least one dissolved solid in the liquid in said second-effect based on the value of said fifth signal, and said sixth signal; establishing an eighth signal representative of the feed flow to said first-effect based on the value of said third signal, said fourth signal and said seventh signal; and manipulating the feed flow to said first-effect in response to said eighth signal wherein the manipulation of feed flow to said first-effect in response to said eighth signal results in the feed flow to said first effect being proportional to the concentration represented by said third signal, the steam flow represented by said fourth signal, and the concentration represented by said seventh signal to thereby maintain a solute balance for the first-effect.