When selecting the best Dewatering Technology, it can be a challenging and confusing process considering the capital costs, effectiveness, and maintenance requirements. Met-Chem has the expertise with various dewatering technologies used in numerous Dewatering Applications. Please contact Met-Chem to see which dewatering technology is best for your specific application.
A Filter Press and Screw Press (Decanter Centrifuge) are two pieces of dewatering equipment that are used in various industrial applications. While the end result of each equipment is to separate liquid from solids, they use different methods to dewater sludge. Some of the most common questions Met-Chem’s customers ask:
A screw press operates first, having a feed slurry enter the center of the unit. The decanter centrifuge contains a horizontal cylindrical bowl, and it is equipped with an internal scroll conveyor, which rotates at a high rate of feed. The bowl and conveyor rotate at different speeds, this allows the conveyors to push solids up the incline of the bowl and out the end of the centrifuge, while the filtered liquid exits out the other end of the centrifuge.
A Filter Press operates by having the feed slurry enter the center feed pipe and fill all of the chambers of the filter press. As the feed pump continues to push more pressure, and more slurry into these chambers, the solids begin to build on the filter press cloth. As these solids are forced into the chambers by the feed pump, they displace or push the water through the filters. The filters have a very tight weave, often 2-3 micron, so the solids cannot pass through and instead continue to pack themselves onto the cloth and push the water through the filter. The filter press is full when the chambers are full of solids.
The Filter Press has several features that make it the better choice for most applications. The first is that the filter press will get a much dryer solids cake. A typical screw press discharge is 10% solids where a filter press can be as dry as 50% solids. A second benefit to the filter press is the technology is simpler. Because of this, there are fewer moving parts. This means there is less maintenance, less downtime, and less manpower. Finally, and perhaps the most important, due to the simple operation of a filter press the cost to purchase one is significantly less money when compared to a similar screw press.
Screw Presses are useful in two main applications when being compared to a filter press. The first is when the solids are being filtered from the solution cause the filter press cloths to blind. This may be caused by slimy solids which blanket the cloth and no longer allow water to pass through. However, this blinding can be remedied by different Filter Press Cloths and/or Filter Aid. Met-Chem offers lab testing which allows us to prove the feasibility of the filter press and also try out different filter media and filter aids, to pick the ones best suited for your application. The second is for applications where the final dryness of the cake is less important, and where the dewatering material is soggy but not a slurry form, such as manure. If this is the case, then a screw press might be the better option. A Filter Press is recommended for applications that require cleaner water, dryer solids for transportation and disposal.
Please contact Met-Chem to see if a Filter Press can be used in your application.
Met-Chem’s Filter Press Feasibility Test is our most popular and common test conducted in our lab. This test is performed to ensure that a filter press is able to filter solids properly with your specific application. The test will allow us to determine cloth sizing and if any Filter Aid will be required for your slurry. With less than a gallon of your typical wastewater, we can see if a filter press will provide the desired result. We will then send you the filtrate (liquid) as well as the solids that we are able to separate from your waste stream. The filter press test will also provide information to estimate the percentage of solids in order to properly size a filter press unit.
In the diagram below, Met-Chem was able to take a sample slurry and filter the liquid from the solids.
A Filter Press is easier to operate and maintain than a screw press. A filter press has fewer moving parts, and therefore, parts don’t need to be replaced as often. As with a Screw Press, the bearings are under constant pressure and eventually will wear over time. In addition, parts to the filter press, such as pumps and the plumbing are more economical and earlier to replace.
In addition, a screw press usually requires an operator to constantly oversee the process to ensure there isn’t clogging and that the dewatering process is running smoothly. With a filter press, an operator doesn’t always need to be present. In addition, a Met-Chem Filter Presses can be fully automated with an Automated Pump Control System and Automatic Plate Shifters.
A filter press uses a diaphragm pump for pressure filtration, which consumes a lot less energy than the large motors on a screw press. Therefore, a filter press is much cheaper to operate than a screw press. Unlike a screw press, a filter press can be scaled and expanded with the use of a backer plate and an extension piece.
The Met-Chem Fully Automatic Plate Shifter allows you to empty the filter press with little to no operator presence. With large filter press plates, it would take two employees to move each plate and empty the filter press. The plate shifter reduces labor costs, improves efficiency, and it is safer than other shifters. As a result, the fully automatic plate shifter will Save You Money.
For added safety, a light curtain can be added. If a person or an object breaks the plane of the curtain, the shifter will automatically stop.
Met-Chem can add-on, rebuild and retrofit your existing filter press with a Fully Automatic Plate Shifter.
The Fully Automatic Plate Shifter uses a PLC control panel to automatically empty the filter press. The load sensing carriage will grab and shift each plate, and it will allow the sludge to fall. This is a great time saver for companies that want their employees doing more productive work than emptying the filter press. Watch the video to see the fully automatic plate shifter in action.
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, Inc.
837 East 79th St.
Cleveland, OH 44103
Phone: (216) 881-7900
Email: info@metchem.com
A Senney Enterprise Company
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