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Pre-Coat/Acid Wash/Body Feed System for Filter Presses

A widely accepted remedy for cloth blinding is the use of a precoat material on the media prior to solution feed. Precoat materials that are commonly used are diatomaceous earth and bleached wood pulp. These materials are mixed with water in a slurry and recirculated back through the filter until the water is clear and the media has a precoat on it. The theory is to have these porous materials set up on the media allowing solution to pass through and build a cake. The many “nooks and crannies” of the precoat give the solids places to build while still allowing solution to pass. To precoat a filter some changes to the plumbing may be required as well or a tank and pump may need to be added. A rule of thumb for precoating is to use 10 pounds of material for every 100 sq. ft. of filtration area in the filter.  Met-Chem stocks filter aid for your immediate needs.

The precoat tank and pump can also be used for cloth cleaning with the acid washing procedure.  To acid wash your filter press cloths use a 25% solution of hydrochloric (muriatic) acid.  A lower concentration may be necessary due to solubility levels of entrapped particles.  (Note:  extreme care must be utilized when handling acid.)  Allow the pump to re-circulate through the press for 1-2 hours.  (For complete information on filter cloth washing see the link below).

Another strategy to use that has proven very successful is the use of a body feed. Either a diatomaceous earth or bleached wood pulp can be used here also, but the difference here is that it is mixed in with the solution downstream prior to entering the filter. This can be done by injecting it into the feed line or pre blending in the solution feed tanks. The idea is to have the body feed material become part of the product and set up on the cloth to stop it from blinding. This method has worked very well, but if the solids are your finished product, the body feed will become part of it and this may be unacceptable. A rule of thumb here is to start with 100 pounds of body feed to 1000 gallons of solution and then wean back the amount as much as possible with each filtration cycle until the minimum amount required is used. This method would require a separate feed pump, tank and/or mixer.

Met-Chem can provide a precoat/body feed system with your new filter press or to your existing system.  This consists of the mixer, tank, pump and plumbing.

Each filtration application is different and a careful study must be done to insure the correct method is used for your application. The filtration experts at Met-Chem can help you solve your filtration problems and improve your efficiencies. Contact the filtration specialists at Met-Chem to see if a consultation or lab test would be appropriate for any and all of your process needs.

Filter Cloth Washing Instructions >>

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