Why Electro Chlorination is the Preferred Method for Power Plant Biofouling Control?

Sep 07, 2022

Why Electro Chlorination is the Preferred Method for Power Plant Biofouling Control?

Many power plants are built near coastal areas since they can use seawater as a coolant. However, these plants frequently encounter the problem of biofouling or biofilm formation in their inlet pipes and cooling systems. Biofouling is defined as the attachment of micro-/macroorganisms to the inner surface of pipes and the subsequent growth of the organisms. It is caused by a variety of organisms ranging from microorganisms (bacteria, algae) to macroorganisms (mussels, barnacles, etc.), depending on the conditions such as flow regimes of seawater in the pipe, the presence of substrate(s), and so on. Biofouling is a huge concern as it blocks seawater flow, which results in the reduced efficiency of heat exchangers, increased loads on pumps, and eventually the failure of power generation.

Among all the methods used to control biofouling, chlorination remains the most popular and preferred, because of its proven effectiveness and relatively low cost. Chlorine not only exerts toxic effects on adult organisms but also inhibits the growth of larvae and their attachment to the substratum. There are various methods to make chlorine in water, such as:
(i)dissolution of chlorine gas;
(ii) addition of hypochlorite;
(iii) electrolysis of electrolytes containing salt or seawater (i.e., electro chlorination).

Recently, electro chlorination has been widely applied for power plant biofouling control. Electrochlorination enables the production of sodium hypochlorite, which is produced through the application of electric potential differences between electrodes with NaCl as an electrolyte. Particularly, under direct current (DC)voltage, negatively charged ions such as chloride, hydroxyl, and oxygen ions donate electrons at the anode to form chlorine gas, oxygen gas, hypochlorite ion, hypochlorous acid, and hydrochloric acid. On the other hand, positively charged ions such as hydrogen, sodium, magnesium, calcium, and potassium ions gain electrons at the cathode to form hydrogen gas and hydroxide.

Compared with ex-situ electro chlorination, in situ electro chlorination in seawater has a few advantages. This does not require a supply of NaCl since it uses Na+ and Cl− in seawater as electrolytes. In addition, it does not require any space for hypochlorite generation and storage. Therefore, in situ electro chlorination is more economical.