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When time is a concern with regard to filter press cycle time, you might want to consider a membrane filter press.
Generally speaking, a filter press takes 4 hours to fill. (Actual time depends upon solids loading capacity and the type of slurry being fed through the press). However, a membrane press can reduce cycle time by approximately, 50% on average and, in some cases, even as much as by 75% depending upon the application.
A standard filter press application for metal hydroxide sludge, for example, with plates that provide a 32mm cake thickness generally takes about 4 hours to fill. The unit is usually 80% full at about the 2-hour mark. Due to the high pressure (100 psi from the diaphragm pump being counteracted by the 4,000 psi of hydraulic pressure), resistance builds and the diaphragm pump begins to slow down considerably.
If you need a quicker turnaround time to get your press back up and running, it might be wise to consider a membrane press. A membrane press is identical to a standard filter press except that the chambers (area between the plates) have membranes to squeeze out excess water from the slurry. A press with all membrane plates can be costly, however, the mixed pack is a more cost-effective alternative. In a mixed pack, each chamber has one side with a membrane that will inflate, thereby causing the squeezing action against a solid recessed plate. When the press is filled to about 80% capacity (this is determined by historical information and/or by the timing of the diaphragm pump), this is the ideal time to inflate the membrane diaphragms to provide the extra squeeze.
The safest way to inflate the membranes is to use water instead of air. If you are using air to inflate the membrane and you experience a tear, you run the risk of plastic breaking which can be extremely hazardous. However, if you use water and experience a rupture, you may end up with a water leak, which is much safer and easier to contain. A tank and pump are used to fill the membranes with water via the manifold piping which would be stainless, PVC or steel (depending on the application) and flexible tubing to connect the manifold to the plates. The water pumps into the membranes during the squeeze process and once that is complete, it is drawn back to the water tank for reuse.
There are two types of membrane filter plates: Polypropylene membrane plate with a welded membrane or a polypropylene plate with a removable rubber diaphragm. In both instances, the plates are polypropylene. The welded membrane plates are a more expensive option. If the membrane should break, the entire plate would need to be replaced. The second option, polypro plate with removable rubber diaphragm is more cost effective. In the event that one of these diaphragms should break, it is not necessary to replace the entire plate. If there is a rupture in plates with the removable rubber diaphragm, only the diaphragm needs to be replaced. Not only is this a cheaper but it’s a quicker fix than waiting to order new plates since these diaphragms are usually in stock or have minimal lead times compared to weeks or in many cases, months for the welded plates.
Membrane plates are also either center feed, gasketed or corner feed, non-gasketed. The corner feed, non-gasketed is the most popular membrane option because it allows the whole area of the plate/cloth to be used for the membrane squeeze whereas the center feed design puts more pressure on the center hole and can cause tears in the cloth or in the membrane itself.
Membrane plates have proven successful in a number of applications. Including but not limited to:
In some instances where the solids are waste and the press is under no strain to operate quickly, the standard non-membrane filter press plates are sufficient; but when time and turnaround are critical, the membrane plate is the solution.
Filling Stage: The Mash enters the chambers through a feed pump.
Filtration Stage: Once the chambers are full, the Mash that is being pushed by the feed pump will force the Wort out from the chambers. The Filter Plates and Filter Cloths will capture the Mash Grains.
Compression Stage: Once the feed pressure has cycled out, the system will be closed and the membrane squeeze will begin. Water or Air is pumped behind the membrane bladders. This compress the mash grains inside the chambers and forces out more Wort.
Draining Stage: Once the compression stage is complete. The Water or Air will drain from the Mash Filter.
Grain / Cake Discharge Stage: Each chamber is opened up for cleaning and the grain is discharged.
Air operated diaphragm pumps are used with filter presses to pump sludge from the bottom of the sludge holding tank into the filter press. These pumps are ideal because they can handle the slurry which is generally about the consistency of a milkshake.
The diaphragm pump usually starts out slowly and gradually ramps up. Once the pump starts to slow back down, (30-60 seconds between thrusts), it is usually an indicator that the filter press is full. At this point, the feed pump should be turned off and the valves on the filter press closed as the operator prepares to operate the air-blow-down process.
The diaphragm pump can be manually turned up or an Automatic Pump Control system may be added. This starts the pump at 25 psi, then moves up to 50, 75 and finally 100 psi which is standard operating pressure for the pump.
Met-Chem provides diaphragm pumps in the following sizes: 1”, 1.5”, 2” and 3”. The material of construction ranges from cast iron, aluminum, polypro or stainless steel.
With the purchase of a new Met-Chem filter press, Met-Chem can mount your air operated diaphragm pump to the legs of your filter press. This option also includes a flex hose that connects the outlet of the diaphragm pump to the center feed pipe, an air filter, a regulator, and an oiler. We can also provide a mounted diaphragm pump for your existing press.
Automatic Pump System Control Panel gradually increases the pump pressure up to 100 PSI for standard units. This allows for even filling of the filter chambers.The Met-Chem Automatic Pump Control System is used in conjunction with an air operated diaphragm pump to automatically increase the feed pump pressure at predetermined intervals during the filter press filling cycle. If the pump runs at a higher initial pressure, the filter cake will become a packed layer of solids on the filter cloth. This will restrict the flow of the slurry thereby creating a very dense coating of the filter cake. This can cause the cloths to blind off and not allow further filtration. Starting at a lower feed pressure allows a soft layer of slurry particles to be deposited on the filter cloth. This initial layer becomes the filtering media which will enhance the filterability of the incoming slurry.
The automatic pump control system automatically and gradually increases the feed pressure in four stages during the filling cycle. These stages are adjustable to suit your slurry and solids concentration. However, it is commonly set at increments of 25 psi. (25, 50, 75, 100). By monitoring the feed pump flow sensor, during the final pressure stage, the operator will be able to determine the cycle completion.
The Automatic Pump Control System also incorporates a low hydraulic pressure safety shut down the device. If there is not enough hydraulic clamping pressure present, the system will completely shut down, eliminating any possible leaking from between the filter plates.
The pump control system allows your filter press to run at its optimum efficiency creating dryer filter cakes, reducing disposal costs, reducing operator time and increasing the life of your filter cloths and feed pumps.
This system can be incorporated with a new filter press from Met-Chem, a used unit or even your own existing press.
Met-Chem is pleased to offer our spare parts kit which includes our 5 piece center feed pipe assembly, a head, tail, and 2 intermediate filter press cloths, and 100 foot of gasketing material. These are essential items for the operation of the filter press. A cracked pipe, ripped cloth, or torn gasket can happen anytime and having these items in your stock will ensure you will be back up and running in no time.
A center feed pipe assembly on a filter press should be able to last many years the same way any other type of plumbing will. However, if the material of the center feed pipe assembly is not strong enough to handle the corrosiveness of the solution running through the press then the center feed pipe assembly can corrode.
For cases of corrosive material or high temperatures, Met-Chem is pleased to offer upgrades from our standard center feed pipe and manifold. We are able to upgrade to CPVC, Carbon Steel, 304 or 316SS Stainless Steel, and Titanium. Met-Chem can also provide additional manifold upgrades such as automatic valves
The center feed pipe is what connects the filter press to the product that needs to be filtered. The center feed pipe assembly consists of five different parts. The first part is the lock nut which fastens on the center feed pipe and connects to the outside of the press. The pipe, which is the second part, goes through the head of the filter and all the way through the head plate of the filter press. The third part of the center feed pipe assembly is a gasket which ensures the assembly is watertight. Next, is the clip nut seat which fastens the assembly to the head plate. This part of the assembly will always stay in place unless you are replacing the assembly or one of its parts. The final part, the cloth clip nut, will be removed often as it is screwed into the cloth clip nut seat after the head cloth is put on the head plate. The cloth clip nut needs to be tightened in order to keep the cloth in place. Met-Chem provides a tool to make this process easier. The Met-Chem Spanner Wrench is a specially designed tool that can be used to loosen and tighten the cloth clip nut when changing the head cloth on a filter press. This tool can be very helpful as the cloth clip, but it has a design that requires a unique tool to tighten and loosen it.
Met-Chem can provide longer legs and a disposal chute on your new filter press. This is especially useful if you are releasing the sludge from the press into a sludge bag or a drum. The chute will direct the sludge directly into your container. If you plan to use a sludge disposal bag, we can add hooks to the chute so that the sludge bag can be hung from the frame of the press.
For some larger presses, we can build a catwalk along with the disposal chute in order to accommodate a roll-off container.
Sludge Dumpsters are used directly under the filter press to catch the sludge that is released from the filter press during cleaning. The dumpster is on casters for easy mobility. They are also equipped with forklift slats for convenient use with a tow motor. The operator can move the dumpster to a roll-off container with the forklift and then pull the release pin for easy emptying. The dumpster can then be snapped back to the upright position and put back under the filter press.
If you produce varying size batches of wastewater and subsequently less sludge, or if the overall volume of waste that is generated at your facility has been reduced, you can still utilize your existing filter press. With the purchase of a backer plate, you can alter the holding capacity of your press to meet your individual batch needs.
A backer plate provides support to the tail plate so that it can be moved anywhere in the plate pack in order to isolate the chambers between the feed end and the tail plate. If you try to use the tail plate in a different position in the plate pack without the backer plate, you run the risk of damaging the chamber of the tail plate.
There are different kinds of backing plates. Some are made of plastic and look much like a standard plate; we prefer to use ~3/8” thick flat stock steel and cut an outline of a plate. This is clearly visible when placed in the stack so that all around know that the filter press is not at full capacity. This steel backing plate is then painted with the same two-part epoxy coating as the frame of the filter press.
Our standard filter presses can be operated manually. However, Met-Chem manufactures four types of filter press plate shifters to make operating your filter press easier, safer and more efficient. Manual filter presses require more time and attention than the same filter press with an automatic plate shifter.
For some larger presses, we can build a catwalk along with the disposal chute in order to accommodate a roll-off container.
The start-up and installation options are available with all Met-Chem waste treatment equipment. We can provide full support as you get your system up and running. We have installation technicians and technical representatives that we can send to your facility to make sure the system is running as it should based on the engineering and design.
Our services include but are not limited to:
All units and systems are complete with manuals and telephone support. However, if you need someone to come to your facility, we will be happy to quote you on that as well.
Met-Chem, Inc.
837 East 79th St.
Cleveland, OH 44103
Phone: (216) 881-7900
Email: info@metchem.com
A Senney Enterprise Company
Copyright © Met-Chem, Inc
