초록 ▼

Two control methods and systems for automatically achieving and maintaining a desired sodium/phosphate ratio and phosphate concentration of the boiler waters in a plurality of parallel industrial boilers linked by a common feedwater line for minimizing corrosion. The first control system uses an ada

Two control methods and systems for automatically achieving and maintaining a desired sodium/phosphate ratio and phosphate concentration of the boiler waters in a plurality of parallel industrial boilers linked by a common feedwater line for minimizing corrosion. The first control system uses an adaptive controller that models the boilers which enables the system to predict boiler pH and phosphate concentrations at any future time given the feed rates, feed concentrations of high and low sodium/phosphate stocks, blowdown rate, mass of the boiler water, initial boiler phosphate concentration and initial pH. Once these future concentrations are determined, the controller then determines a common normalized control (target) region among all the boilers and feed rates that will drive at least one of the boilers into that region in the least amount of time. Subsequent iterations of feed rates are made based on updated boiler water concentrations to drive all of the boiler waters into that target region. The second control system monitors a maximum cycle boiler ratio to keep the boiler waters within the phosphate control range of the system. This arrangement allows for the control of sodium by switching between the high and low ratio sodium/phosphate stocks based on the average sodium-to-phosphate ratio among all the boilers with respect to a desired average predetermined sodium-to-phosphate ratio.

대표청구항 ▼

[ We claim:] [1.] A method for controlling at least two interdependent chemicals in the fluids of at least two continuously stirred tank reactors (CSTRs) having respective blowdown flows and steam rate flows defining respective cycles for each of said CSTRs, said at least two interdependent chemical

[ We claim:] [1.] A method for controlling at least two interdependent chemicals in the fluids of at least two continuously stirred tank reactors (CSTRs) having respective blowdown flows and steam rate flows defining respective cycles for each of said CSTRs, said at least two interdependent chemicals being fed to said fluids through a common feedwater to each of said at least two CSTRs, said method comprising the steps of:(a) establishing a respective mathematical model of each of said CSTRs;(b) monitoring the concentration of one of said at least two interdependent chemicals in each of the fluids, the temperature at which the pH is measured in each of the fluids, the respective blowdown flow and the respective steam rate flow;(c) updating the models based on the concentration of said one of said at least two interdependent chemicals in each of the fluids, the pH of each of the fluids, the temperature at which the pH is measured in each of the fluids, the respective blowdown flow and the respective steam rate flow;(d) defining a respective target region of said at least two interdependent chemicals in said respective continuously stirred tank reactors and wherein said respective target regions are scaled according to the respective cycles, said respective target regions establishing a state of congruency for each of the fluids;(e) providing a feedstream of a high-pH fluid treatment material comprising a mixture of said at least two interdependent chemicals and a feedstream of a low-pH fluid treatment material comprising a mixture of said at least two interdependent chemicals for feeding, at respective feed rates, to the fluids; and(f) developing an optimum feed rate program for controlling said feedstreams to automatically minimize the time that said at least two interdependent chemicals in the fluids spend outside of a common normalized target region formed by the intersection of said respective target regions.