A. Fouling control measures

(a) Physical Mitigation Techniques
(by T. R. Bott)

The removal of deposits from heat exchanger surfaces may be achieved by the application of suitable forces that dislodge the accumulation of unwanted material. In many instances the removal forces are applied through a fluid medium, often it is the process fluid itself that provides the means of applying the removal force. In other situations, deposits are prevented from forming or are knocked from the surface, by a solid agent. Some of the techniques lend themselves to on line cleaning i.e. the process is continued while the mitigation takes place. Other techniques may require that the plant is shut down, or at any rate the particular heat exchanger in question is taken out of service for cleaning. Many of the techniques are not universal and have been developed to meet particular requirements and processes.

I. Circulation of Sponge Rubber Balls

In the power industry the maintenance of steam condenser performance is essential to maintain generation efficiency and competitiveness. In order to maximize the output from the turbine generation set, it is necessary to ensure that the lowest possible pressure in the steam condenser is retained. Condensation is achieved by the circulation of cooling water through the tubes of very large shell and tube exchangers. The system may be once through or recirculating. Since in general, the water system is open to the atmosphere it is likely to become contaminated with microorganisms and particulate matter that accumulate in the condensers where the conditions favor the formation of biofilms (see Section 358). In addition, scale formation is possible, where the concentration of dissolved solids reaches saturation levels (due to evaporative cooling of the water). In addition particulate products of corrosion may also accumulate on the surface, or the surface itself may become corroded. The consequence, if mitigation techniques are not applied, is the formation of slime layer (due to microbial colonization) in conjunction with particulate deposition, products of corrosion and crystal formation where conditions are suitable.