System and method to improve control of conductivity, free residual chlorine, level, andpH in large cooling towers

摘要

A system and method are disclosed which significantly improves the control of conductivity, concentration of free residual chlorine, basin level, and pH in forced-draft open recirculating cooling towers, with a basin capacity of 750,000 gallons of water or more. Conductivity, free residual chlorine, basin level, and pH are each controlled by a programmable PID controller operating in a sampled-data environment where the set point is a continuously updated rate-of-change set value for conductivity, free residual chlorine, basin level, and pH based on a near-time prior manipulated value. Programmable PID controller outputs to each control element a manipulated value to bring the rate-of-change of the process value equal to the rate-of-change of the set value.