Fouling potential

One way to decrease your reliability and cause problems is to not men tion fouling potential in centrifugal compressor specifications if proce.s.s experience exists. The experience may exist but not be recognized... 

Although EDI may be used as a process for the production of basic pure water, in practice it suffers from the organic fouling potential of resins and the scale fouling potential of ED when higher TDS water sources are utilized. Appropriate pretreatment is therefore required. As a consequence, EDI is best suited for the production of very pure and ultrapure water by acting as a polisher to follow bulk water deionization by RO. Under these circumstances, it competes with both doublepass RO and MB units. 

Effluent pretreatment is necessary when RO is used as tertiary treatment in order to prevent membranes filters form being blocked or abraded. UF offers a powerful tool for the reduction of fouling potential of RO/NF membranes [57]. A typical pretreatment consist of a MF allowing the removal of the large suspended solids form the WWTP effluent followed by UF unit which removes thoroughly suspended solids, colloidal material, bacteria, viruses and organic compounds from the filtrated water. The UF product is sent to the RO unit where dissolved salts are removed. 

Sheppard, J.D., Thomas, D.G., and Channabasappa, K.C., "Membrane Fouling Part IV Parallel Operation of Four Tubular Hyperfiltration Modules at Different Velocities with Feeds of High Fouling Potential," Desalination 11, 385-398 (1972). 

Design of the membrane module system involves selection of the membrane material the module geometry, eg, spiral-wound or hollow-fiber product flow rate and concentration solvent recovery operating pressure and the minimum tolerable flux (9,11). The effects of these variables can be obtained from laboratory or pilot experiments using different membranes and modules. The membrane module as well as the solvent recovery can be chosen to minimize fouling. Spiral-wound modules are widely used because these offer both high surface area as well as a lower fouling potential. 

Liquid to grids is usually supplied by spray nozzles, and thess may plug. As with other distributors, adequate measures are required to prevent plugging, and the grid manufacturer must be supplied with good data on the fouling potential of the service. 

Include all data, constraints, or requirements arising from step 1 above. If uncertain about how fouling, potential for pressure surges, startup and shutdown constraints, etc., affect the packing design, discuss these with the suppliers. 

There are many reasons why in some cases the feed stream needs to be pietreated prior to entering the membrane system. When the membrane has great fouling potential with respect to the feed components, or when the membrane pore size is close to or significantly larger than the size of the species to be retained, both the permselectivity and permeability may be compromised. 

It has been proven over the years that the effect of fouling can be lessened to some extent for the application of whey concentration by pretreating the feed streams for the ultrafilters. Whey contains many insoluble solids such as casein fines, lipoprotein complex, mineral precipitates, free fats and microorganisms. Clarification of these debris helps reduce fouling potential during ultrafiltration. In addition, it is quite evident that calcium phosphate minerals in whey are not stable and their precipitation in the membrane pores often results in flux decline. Demineralization of whey before ultrafiltration helps maintain high permeate flux considerably [Muir and Banks, 1985]. 

Sintering strength tests have been used as an indication of fouling potential. Assuming that correct ash compositions have been represented (which is less of a problem in the convection section than in the radiant section) worthwhile information may be obtained relative to a time/temperature vs. bonding strength relationship. 

Fouling Potential Severe High High Moderate Moderate Low Low... 

Prediction of ash deposit characteristics based solely on bench-scale fuel properties always requires substantial judgement and allows only a certain level of confidence. As discussed, the ash deposition process is so complex that detailed modelling of commercial systems based on fundamental data is presently unrealistic. However, current techniques can provide relative data which in most cases is sufficient to make accurate assessment of slagging and fouling potentials relative to other fuels. 

R. W. Borio, R. R. Narciso, Jr., The Use of Gravity Fractionation Techniques for Assessing Slagging and Fouling Potential... 

Packed-bed towers can achieve removal efficiencies of over 99% and have relatively lower water consumption requirements. They also offer design and retrofit flexibility. Disadvantages include high system pressure drops, relatively high clogging and fouling potential, potentially high maintenance costs, and waste water disposal requirements. Packed-bed scrubbers are also more expensive to install and operate than spray towers. 

In hydroids the body wall is not calcified, so that their fouling potential is not so great as with barnacles, mussels and serpulids. Large accumulations of hydroids however, can give rise to severe water flow restriction. 

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