(130b) Optimization of Seawater Cooling Systems with Dynamic Dosage of Biocides | AIChE

(130b) Optimization of Seawater Cooling Systems with Dynamic Dosage of Biocides


El-Shoubary, Y. - Presenter, Qatar University
El-Halwagi, M. - Presenter, Texas A&M University
Alfadala, H. - Presenter, Qatar University
Bin Mahfouz, A. - Presenter, Texas A&M University

The use of seawater in industrial cooling is a common practice in many parts of the world that have limited fresh-water resources. One of the primary operational problems of using seawater in cooling is biofouling. Because of the biological activities of micro-organisms in seawater, biofilms are formed. These biofilms tend to stick to heat-exchange surfaces, thereby significantly reducing heat-transfer coefficients. Biocides may be used to limit the extent of biofouling. Chlorine is one of the most commonly-used biocides. The use of chlorine results in various environmental problems upon the discharge of the cooling seawater. Therefore, it is important to optimize the dosage of chlorine so as to insure proper technical operation while minimizing the negative environmental impact. There are several methods for dosing seawater with chlorine. One of the most effective methods for dosing is the dynamic technique. It involves either ?pulsed? or ?shock? dosing of cooling water. This paper is aimed at developing a cost-effective and practical method for optimizing the dynamic dosing of cooling systems employing seawater. Mass and heat integration techniques are used to optimize the quantity and schedule of chlorine dosage, the optimal flowrate of cooling water, the temperature profile, and the use of dechlorination units before environmental discharge. The key chemical pathways and the effect of dynamics were incorporated in a mathematical model. This model accounts for the various parameters that affect the distribution of all oxidant species in chlorinated seawater throughout the cooling system. This model is also used to dechlorinate the treated seawater before discharge back to the sea in order to meet the regulations. A case study is solved to illustrate the merits of the developed procedure.