Fouling operating strategies

Such sources of waste must be systematically identified and avoided by appropriate design and operation strategies. For example, in distillation, selection of operating temperature and pressure in the distillation column can sometimes minimize fouling in gas absorption, careful attention to liquid distributor and packing... 

The effects of various operating strategies against different types of fouling are summarized in Table 6.4. As indicated in Table 6.4, chemical cleaning is an effective control strategy for a majority of membrane fouling. 

TABLE 6.4 Effects of Operating Strategies on Membrane Fouling"... 

Fouling organisms attach themselves to the underwater portions of ships and have a severe impact on operating costs. They can increase fuel consumption and decrease ship speed by more than 20%. Warships are particularly concerned about the loss of speed and maneuverabiHty caused by fouling. Because fouling is controUed best by use of antifouHng paints, it is important that these paints be compatible with the system used for corrosion control and become a part of the total corrosion control strategy. 

From this work, the analysis developed clearly shows how to optimize the catalyst to feed ratio to minimize catalyst inventory but maximize the feed conversion as well as the product selectivity. Although at the present stage, this cannot be directly applied to the commercial operation without further pilot plant substantiation. Since this is a continuous research program, further work will be undertaken using the typical FCC feed contmning metal and sulphur fouling precursors to refine the developed strategy. This will be, finally adopted to run in a MAT for FCC catalyst evaluation. 

During operation it is vital that the equipment operator is aware of the potential fouling problems and accordingly devise strategies that minimise the risk of increased fouling. 

A range of membrane processes are used to separate fine particles and colloids, macromolecules such as proteins, low-molecular-weight organics, and dissolved salts. These processes include the pressure-driven liquid-phase processes, microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO), and the thermal processes, pervaporation (PV) and membrane distillation (MD), all of which operate with solvent (usually water) transmission. Processes that are solute transport are electrodialysis (ED) and dialysis (D), as well as applications of PV where the trace species is transmitted. In all of these applications, the conditions in the liquid boundary layer have a strong influence on membrane performance. For example, for the pressure-driven processes, the separation of solutes takes place at the membrane surface where the solvent passes through the membrane and the retained solutes cause the local concentration to increase. Membrane performance is usually compromised by concentration polarization and fouling. This section discusses the process limitations caused by the concentration polarization and the strategies available to limit their impact. 

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