Sponge ball cleaning

More frequent manual cleaning of tubes was suggested as on-line sponge-ball cleaning did not appear effective. Higher concentrations of tolyltriazole were fed with no discernible effect. 

Figure 3.67 Effect of sponge ball cleaning on long term flux decay.

These modules are easy to clean. Typically, a sponge ball is shot down through the feed channel or tube to physically remove debris from the surface of the membrane. In most tubular applications, the membranes need to be cleaned on a daily basis. This is because the nature of the solution being treated by the membranes generally contains high concentrations of suspended solids and organics, which collect on the membrane. 

If the feed is preconditioned properly, the UF flux is often quite stable. One thousand hours of continuous operation between cleanings is common. When flux decay does occur, detergent washing is usually sufficient to restore flux. In some cases, polymer solvents may be required. Proper selection of a solvent resistant membrane and/or solvents which will dissolve the latex but not affect the membrane is crucial. For PVC latex, the solvents of choice are methyl isobutyl ketone (MIBK) and methyl ethyl ketone (MEK). Styrene butadiene rubber will swell in MIBK, MEK or toluene. Polyvinyl acetate will dissolve in the low MW alcohols such as propyl alcohol. Generally, the membranes are first washed with water, then detergent, followed by another water flush. The system is then drained of all water since it will affect polymer solubility in MEK. Finally, a solvent rinse is employed. If the module is tubular, sponge balls will enhance cleaning. 

Fig. 16.S is a simplified flow sheet of a power station equipment with a sponge rubber ball cleaning system (e.g. Taprogge system). The technique is described in some detail in Chapter IS. The technique reduces the problem of biofouling, scale formation and particulate deposition. The system requires suitable pumps, filter screens and storage for cleaning devices. In addition to the mechanical treatment (only applicable to the condenser tubes) chemical treatment is also required to combat fouling in other parts of the system.

FIGURE 16.13. Condenser pressure variation on a 500 MIF station over a 12 month period using a sponge rubber ball cleaning system... 

The tube-in-shell system (Figure 17-lB) is occasionally used. This configuration is very similar to a shell-and-tube heat exchanger. The membrane would be coated on a porous support. The main advantage of these systems is that they can be cleaned by passing sponge balls through the separators. The surface area per unit volume is more than for plate-and-frame but less than for spiral-wound. 

Mechanical cleaning can only be applied in tubular systems using oversized sponge balls, permeate... 

The skin is usually degreased with alcohol followed by a mild acetone scrub. After cleaning, Jessner s solution is appUed to the face with a sable brush, cotton tipped apphcators, cotton balls, or 2 X 2 gauze sponges. The author prefers the use of cotton tipped applicators. Typically, the cheeks are treated first, working from medial to lateral areas followed by application to the chin and forehead area. For superficial peeling, two coats are usually applied. Additional coats increase the depth of peeling. 

The tubular element Is the least susceptible to fouling and the easiest to clean. This element is widely used in ultrafiltration applications where the process streams contain suspended solids. The tubular element can be cleaned not only by chemical action but also by mechanical means. A sponge rubber ball is pumped through the tubular element with the chemical cleaning solution to scour the membrane surface. 

The sponge rubber ball system is only suitable for cleaning the inside of tubes and therefore its use is restricted to tubeside single pass or possibly U tube designs for two passes in shell and tube heat exchangers. The system cannot be used for the shell side or for plate heat exchangers and other non tubular designs. 

Fig. 16.11 compares the payback time for the installation of sponge rubber ball mechanical cleaning of heat exchangers [EPRI 1987]. Although these data were again published in 1987 and will therefore include historical costs, they do indicate economic advantage in respect of the system. 

Post-treatment Automatic cleaning of tubes heat exchangers by sponge rubber balls or brushes without operating interrupt of the plant. 

Posttreatment Automatic cleaning of heat-exchanger tubes by sponge rubber balls or... 

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