Calcium Carbonate Scale Control in Industrial Water Systems
Fouling in water-intensive industrial applications is one of the most severe problem-causing situations as it often leads to shorter or longer shutdowns of the units with concomitant increase in process cost. Several types of fouling have been identi ed, depending on the respective cause of development. Despite the fact that all these types deserve special attention, crystallization fouling is considered to be most detrimental to the industrial processes worldwide. This type of fouling is de ned as the process in which dissolved ionic components of salts crystallize and eventually deposit at the water/solid interface involved in the process. Salts with inverse solubility tend to cause fouling of heated metallic surfaces, while more soluble salts crystallize on cold or cooled surfaces. Waterformed scale deposits, even in cases in which their composition is not complex, depend on a number of factors, including the ion speciation in the aqueous medium, the properties and the characteristics of the surfaces in contact with the aqueous phase, the uid dynamics, and the heat-transfer parameters of the process. Calcium carbonate deposits have been identi ed in water-carrying pipes from antiquity, as may be seen from outdoor exhibits at the archeological museum of Naxos, Greece, as shown in Figure 3.1.