Skid-Mounted Precoat Stations are custom built to work with any Filter Press (minor changes in the plumbing may be required). The basic precoating system includes a skid-mounted platform with a holding tank, mixer, controls, and a diaphragm pump. The precoat station can also be used as an Acid Wash System to clean filter cloths and maintain high levels of filtration.
The basic precoating operation involves mixing a slurry of filter aid, usually a combination of water and Diatomaceous Earth. The slurry is then pumped into the Filter Press and then recirculated into the holding tank. This process is run until the liquid appears to be clear or until the appropriate depth of precoat is achieved.
Skid-Mounted Precoat Stations can be customized and operated differently depending on the process of your specific application. Contact us for advice on the benefits of these portable skid-mounted systems.
Build to Your Specifications
All sizing and Material of Construction are Customized to Fit Your Specific Application
The Skid-Mounted Precoat Station also be used for filter cloth cleaning with the acid washing procedure. In order 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 recirculate through the press for 1-2 hours. Read more on Filter Cloth Washing.
Before using Acid to clean your filter cloths, Please Consult Met-Chem.
Variations in applications, plumbing material, and filter presses will vary.
A widely accepted remedy for filter press 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 press 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 the 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 the solution to pass. To precoat a filter press some changes to the plumbing may be required. 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.
Lab or pilot tests can be done to see if a tighter or looser filter cloth will help build a cake prior to blinding. The secret to filtering with just the filter cloth is to get the solids building on each other before the cloths blind.
The next 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 the 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 the solution to pass.
In order to precoat a filter press, some changes to the plumbing may be required. A rule of thumb for precoating is to use 10 pounds of material for every 100 sq. ft. of filtration area in the filter.
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 preblending 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 System or body feed system with your new Filter Press or to your existing system.
Each filtration application is different and a careful study must be done to ensure 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.
Met-Chem, Inc.
837 East 79th St.
Cleveland, OH 44103
Phone: (216) 881-7900
Email: info@metchem.com
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