Cleaning filter press cloths

A. I would suggest that you not use nitric acid for filter cloth cleaning because it is dangerous, destructive of the cloth and, as an oxidizing agent, it may adversely affect the process.

2 percent HCl does sound okay, but weak, for cleaning filter cloths.

Good luck.

A. Acid cleaning your press extends the life of the cloths. We clean our press about every 6 months with a spent hydrochloric acid solution and then flush it with water. This restores the plates to almost new condition. The cost of the cloths is not as much an issue as the downtime and the labor of pulling those old cloths off and installing new ones.

A. I have been cleaning my plates for years. Over a period of time the weave becomes blinded over with polymer. When I pull the plates to clean them I use a 20% HCl solution, maybe 10-15 minutes, spinning the plate to make sure I do not trap air. Rinse well and wash any residue that remains on the surface off with a hose. Take care, the plates are in the press in series, make sure to replace them in the proper order. I also wash the plates while they are still in the press, I dump the press, circulate HCl through while restricting the discharge to assure the plate is full of acid, flush with H2O, blow down, open press, rinse surfaces with a hose and I am done. I have had the same cloth in the press for 8 years, I acid wash at least four times a year. I get a filter cake that is 35-45% solids. I generate 30000# of WWT sludge monthly.

A. ` If the cloths on the plates are a typical polypropylene weave you can effectively clean them with hydrochloric acid, 30% + or - 10%. Don't remove the cloths, soak the plate and all in a tank of the acid solution for a couple of hours. Be careful, rinse thoroughly before reusing. You'll find that the plates in the acid solution have to be oriented just right so that gases formed during the cleaning can escape. Otherwise the trapped gas can pull the cloth away from the plate. This procedure made an enormous long-lasting difference for me. I'll probably do it yearly now.

Good luck.

A. Yes, use a solution of: 1 cup liquid detergent, 3 cups of 5% bleach ⇦ bleach/sodium hypochlorite in bulk on eBay or Amazon [affil links] to 5 gallons of water. Apply with a pressure washer and you should see immediate results. Good luck

A. Generally, yes. But pack a lunch. 2% is going to take a long time. We found by accident that you can get nearly the same result (if filtering metal hydroxides from waste treatment) by thoroughly drying the cloth. Separate the plates and leave a fan blowing over a weekend. Works like new on Monday. If the cloth is old and fuzzy it should be replaced.

  Good Idea! I will definitely try this trick this weekend.. Makes perfect sense.

A. Larry

For what it's worth...

We have been experiencing problems with our filter press. We precipitate chrome and zinc and run it through our filter press. The cloths are 2+ years old. Previously, they were replaced after a year when 'problems' arose. Our symptoms included- the press not filling completely before our diaphragm pump stalled out; and after blowing down, there was still considerable moisture in the cake.

We had tried mechanically cleaning the cloth with a siphon gun/aspirator and had minimal success. Then we tried a high pressure washer (car wash style). Our unit had a max output of 1300 psi and we throttled the nozzle back to achieve a 3-4" spray pattern at a distance of 3-4" from the nozzle tip. We started with a gun distance of about 8-10" from the cloth and continuously moved the spray across the cloth. After several paths across the surface we could see the white of the cloth. We continued until most visible signs of residue were removed.

Upon re-install, they worked like brand new.

We left the clothes in the plate while cleaning, and would advise starting at a conservative distance when spraying and work closer as needed.

As mentioned earlier, drying the clothes out between uses helps a lot.

A. Hi Raphael. Sorry, my filterpress experience is with metal finishing sludges, and I'm not picturing your situation. So the first question I would ask is whether you are sure a filter press is the proper equipment for the process? There are also vacuum filters, centrifuges, cartridge filters, automatic paper filters, etc. When you are filtering contaminants rather than badly in need of concentrating and drying large volumes of sludge, a chain-driven automatic paper filter may do the job with no cleaning labor at all.

Luck & Regards,

A. Muriatic isn't going to do anything to polypro.

You might try a DE precoat, makes life much easier.

A. With metal hydroxides, rather dilute acid, say 5-10% works well, especially if it is pumped through the press in the reverse direction. 10-15 minutes is usually a sufficient time for recirculating the acid.

The same acid can be used multiple times as long as it doesn't lose all of its strength. You just need to use compressed air to return it to the acid cleaning tank.

A. We have used a 6 to 10 percent Hydrochloric acid solution recirculating the acid through the press for about 4 hours and have had positive results. I hate using acid because of the fumes.

We have a 250 degree hot water power washer that cleans the cloths like new. We clean the cloths on the press plate in the press. The hot water cleans organics off the cloth like butter. We also run a high lime process and generate calcium hydroxide and calcium chlorite sludge that blinds the cloths. The hot water power washer slakes the lime buildup right off the cloths. The hot water power washer is the best piece of equipment I have ever used for deep cleaning press cloths.

A. I prefer dilute sulfuric acid at 1-5%, but, importantly, flowing in the reverse direction from filtration service. Hydrochloric works faster but has fumes.

A. Hi Dey. Almost surely your customer is exposing the filter cloth to solvents which are attacking it. But myself and most of our readers are from the metal finishing industry rather than pigments manufacturing, and you probably must tell us what chemicals are used in those "certain cycles" before any reasonable suggestions can be offered. Thanks,

Regards,

A. Hi Hediye. More words please; I have no idea what you're talking about :-(

Is this filter cake your product rather than your waste? If so, why do you want to wash it -- what might be there? Whatever it is would run throughout the whole thickness, but that you want it washed off of the surface of the cake? Or is the calcium chloride being used as some sort of filter aid or media and you're hoping to be able to dissolve everything you captured without dissolving the filter aid? If so, what have you captured on it? Thanks.

Regards,

A. Hi Jovana. As you see, this topic has been discussed in depth for 14 years here. Surely the answers are above, but feel free to post additional questions or requests for clarification.

Luck & Regards,