Main factors affecting filtration of water treatment equipment

According to the theoretical analysis and filtering practice, the main factors affecting filtering are as follows:

1. Temperature

When filtering, the suspension temperature is low, the viscosity is high, and the filtering speed is slow. The viscosity of the liquid is an exponential function of temperature, which decreases significantly with the increase of temperature Temperature rise is a simple and useful measure to reduce viscosity, but too high temperature will easily cause oil oxidation, and the filtration temperature of crude oil generally does not exceed 70 ℃

2. Operating pressure

The impurities in the crude oil are mostly incompressible impurities, with high operating pressure and filtration rate If the suspended solids in the oil are composed of colloidal substances, with the increase of pressure, the space in the filter cake becomes smaller, the filtering resistance gradually increases, and the filtering speed drops rapidly. Therefore, the pressure should be determined according to different situations

3. Suspension concentration

The high concentration and large amount of filter residue shorten the useful filtering time in each operation cycle of intermittent production and affect the output For the operation of continuous vacuum filter, the filter cake generated when the concentration is relatively high is uniform, easy to clean in time, and has little impact on the output

4. Filter media and filter aids

The selection of filter media affects the clarity of the filtered oil and whether the cake is discharged smoothly. The filter media used in the oil and fat industry are mostly woven media. Common cotton fabrics, such as canvas with 20 yarns and 5-8 strands, twill cloth and ordinary white muslin, are also commonly used. Chemical fiber products, such as 130 #, 240 #, 260 #, 261 # polyester filter cloth and 828 # vinylon filter cloth, are also commonly used The coarse oil filter with more warp and weft strands is used for crude oil filter, and the essential oil filter with less strands. For some filters with high requirements, a layer of white fine cloth or flannel cloth should be covered on the coarse filter cloth In addition, stainless steel wire woven filter screen is often used, 30-40 hole/cm filter screen is used for crude oil filtration, and 140-180 hole/cm filter screen is used for decolorization oil filtration

For suspensions containing more colloidal particles, adding filter aids can improve the filtration speed Especially, the application of filter aid is of great significance for some suspension systems that cannot be filtered by increasing temperature due to process limitations If you want to use the extracted oil to make edible phospholipids, diatomite should be added as a filter aid; In dewaxing and fractionation, filter at a lower temperature, and the effect of filter aid is more obvious.