90-02: Designing a Cooling Water Program With the Aid of a Three-Dimensional

When managers of cooling water systems operations make decisions concerning a treatment approach for scale, corrosion, or deposit control, economics often play a very important role. A treatment program must be economically justified before it is implemented, and managers traditionally strive to optimize cost without sacrificing performance goals and unit reliability. Many factors affect the operations of a recirculating cooling water system and there are numerous components that comprise the total cost of a treatment program. However, when asked, "What is the cost?" of a given treatment program, the reply often centers on the cost of specialty chemicals used in the program. In fact, a closer look at the variables that affect the total treatment cost gives a more representative picture than specialty chemicals alone. Operating variable such as cycles of concentration and pH of recirculating cooling water and the acceptable level of corrosion inhibitors are important factors to be considered. "Cycles of concentration" of a recirculating cooling water system defines the material balance of a cooling water system and directly affects a variety of make-up and blowdown related costs. Targeted recirculating cooling water "pH" not only dictates the cost of pH adjustment chemicals, but also influences the concentration of specialty chemicals required for the achievement of scale and corrosion inhibition goals. The acceptable level of "corrosion inhibition" itself can have a great impact on the amount of chemicals needed and, therefore, the treatment costs. This paper describes how decision-makers can visually examine the impact of operating variables on various cost elements as well as total cost and quickly make an informed decision. Computer modeling of cost optimization and three-dimensional graphic display play a strong role in creating "pictures" of the relationship between cost and operating variables. Cases of practical application in real-world setting using the computer-aided methodology are presented.