7.3.1 Condenser fouling
Various forms of fouling have already been covered in detail in Section 4 of this chapter, which looked at the erosion/corrosion of condenser tubes from impingement attack.
Basically there are three aspects of fouling which are beyond the scope of the CW screening plant installed:
- Blockage by debris.
- Biological slimes.
Blockage by debris of tube and tubeplates was extensively covered in Section 4 of this chapter.
Biological fouling refers to marine life which contribute to the formation of the slimy deposits on the heat transfer surfaces of condensers. These include bacteria, fungi and algae. The slimes formed by these micro-organisms adhere to the metallic surface, resist heat flow and form a layer to which other suspended matter can adhere to reduce condenser performance further. Some forms of marine life, such as mussels and barnacles, can cause problems by restricting flow and blocking tubes.
Scale formation is caused by the deposition or reaction of inorganic material on heat transfer surfaces. It usually occurs at inland river-cooled stations, using cooling tower systems. The scales are usually calcium carbonate or calcium phosphate, or mixtures of both, and arise from variations in their solubility products with temperature and pH changes (Fig 4.32). The temperature effect is due to the inverse solubility characteristics of calcium salts. The pH changes arise by carbon dioxide stripping in the cooling towers.