Plate and Frame Filter Presses are the most basic and oldest type of Filter Press. A metal skeleton holds and locks the filter plates together to build a pressure chamber in the formation. Clamping is accomplished with either an old-fashioned wheel crank or, more recently, a hydraulic pump and cylinder (either manual or automatic). The plates are made of a variety of metals, including cast iron, aluminum, and polymers, the most popular of which is polypro. Before being filtered through the cloth, the slurry is pushed into one or more corner holes and then into each frame. The filtered clean water runs through the solid plate’s drainage system and into one or more corner holes that aren’t used for slurry feed. This clean solution makes its way to the customer’s tanks, drain, or process via discharge pipes. No more slurry can be fed into the filter press once these hollow frames are full with solids, so it’s time to open the press and knock out the solids.
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The slurry is poured into a corner hole and runs into each frame, collecting solid particles on the filter cloths. The filtered part is then passed to a drainage tunnel in the flush plate and toward a corner hole that is untouched by the slurry. The filtrate is then headed to the next phase in the process through the discharge pipe.
After some time, the frames load with solids, the slurry feed pump closes, and the filter press is set to unlock. Filter cakes should be present in each frame as a result of solids accumulating on the filter cloths. The filter cakes are scraped off the frames and dropped in a cake hopper beneath the press with a spatula.
The main advantages of plate and frame presses are the ability to swiftly change filter cloths and employ a wider choice of filtration medium materials, including paper, which is frequently used for fine filtration applications.
Filter paper, for example, may be required in a process where quick particle retention is critical, as fine particulates would either blind off the filter cloth or pass through it. The filter cloths are still in situ to keep the filter paper in place, and filter cloths can be reused. However, one must replace filter paper after each filtration cycle.
Plate and frame presses are appropriate for jobs that prioritise filter area over volume. As a result, plates and frames are most usually utilised in polishing (rather than dewatering) applications, where the feed solids concentration is often less than 1% by weight.
The process flow rate and the known flux rate are used to size polishing treatments for a specific filtration region (volume per area per unit of time). Polishing applications typically include a redundant filter press sized to accommodate 100 per cent of the desired process flow to minimise dips in achievable filtration flow as the press fills with solids.
When filter plates are pressed together in a recessed chamber filter press, they generate a series of cavities between them. Filter cloths capture suspended particles, which build up inside each cavity to form a filter cake. In contrast, solids are collected in the hollow frames of the plate and frame design.
The slurry is poured into the filter press through the feed (usually in the middle of the plate), and the solids are evenly dispersed across the media in each chamber (1). Solids begin to accumulate on the filter cloths, and the particles that accumulate on the cloths do the majority of the solid/liquid separation. Some fines slip through at first, but the solids soon build on the cloths (2). The fine particles are trapped in this layer, which is followed by a filter cake. As the dewatering process continues, the filter cake acts as a depth filter.
Usually, the filtrate (liquid) exits the filter pack (plates) via corner ports into a manifold. When the appropriate valves in the manifold are open, the filtrate moves out of the press by a single point, the filtrate outlet. The filtrate is then directed to the next phase in the process through the discharge pipe.
The solids build up within the chambers as the filter press gains pressure until the filter cake is full (3). The filling cycle is complete after the chambers are filled, and the filter press is ready to be emptied (4). After then, the press is opened, and the plates are separated. The filter cake drops from every chamber into a cake hopper or drum under the press as the plates are replaced. If necessary, scrape the cake from the cloths with a spatula.
One of the most significant advantages of the recessed chamber plate design is feeding a large central hole rather than a small opening in the plate’s corner. The big space in the centre of the plates helps the chambers to fill more quickly and evenly, reducing the risk of clogging and plate damage caused by uneven pressure. This is especially true in applications where the feed solids are considerable.
However, in large-scale polishing applications with high flux rates, a bigger feed intake (coupled with acquiring one extra filtrate outlet in a centre feed setup) is important (for example, a Merrill-Crowe process). The calculated press flow rate will not be feasible if the filter plate inlets, outlets, and internal ports are not large enough.
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Another benefit of the recessed chamber design is the potential to obtain higher feed pressure. The “frame,” or sealing surface, is attached to the centre web, preventing it from bending out under high pressure.
Designed for efficient solid/liquid separation, recessed chamber filter presses and filter plates are popular in a wide array of industries, from industrial and municipal wastewater to chemical processing. Learn how these types of filter presses and plates work and their advantages. Then, reach out to a member of our Sales and Service Team here at M.W. Watermark™ to see if a recessed chamber filter press is right for your application.
Like all filter presses, recessed chamber filter presses work by using a pressure filtration system. They have filter plates that hang on a steel frame. These plates – usually made from polypropylene – come in gasketed and non-gasketed designs.
Gasketed filter plates help eliminate leaks, while non-gasketed filter plates make filter cloth installation faster since the cloths do not need to be pounded in but may result in a bit of leakage. Regardless of which type is utilized, the filter plates are clamped together in a filter press using a hydraulic cylinder and pump. Since each plate features a recessed area, when the plates are pushed together, they form a chamber in which solids collect on the filter cloths.
During the filtration process, slurry is usually fed through a large center feed hole. Liquids will pass through the filter cloth and onto the drainage surface. The liquids will eventually make their way through the discharge piping and into a process tank or drain. Meanwhile, the solids will accumulate on the filter cloths in the cavity that was formed when the plates were clamped together. Depending on the nature of the slurry, recessed chamber filter presses and plates can produce filter cakes consisting of 20 to 85 percent solids.
Click below to watch our introductory video, which illustrates the role of filter plates, filter cloths and pressure filtration in forming a dewatered filter press cake in a recessed chamber filter press.
Recessed chamber filter presses and plates are used in various industries to effectively separate liquids and solids. Some common industrial applications for this type of filter press include:
One of the top benefits recessed chamber filter presses have to offer involves how they are fed. With a large feed hole in the center of the plate stack, the slurry is able to fill the cavities swiftly and more evenly. This helps rule out the possibility of clogging and blowing out, helping prolong the life of your plates. This is especially important in applications with high feed solids.
A second advantage comes courtesy of the plates they utilize. As previously mentioned, recessed filter plates are available in both gasketed and non-gasketed versions – and even in non-gasketed plates, there is an option for the addition of latex that runs along the edge of the filter cloth to help minimize wicking. No matter which type of recessed chamber filter plate works best for your particular application, liquids can generally be contained with proper operation.
Finally, recessed chamber filter plates make it relatively easy to empty the filter cakes. When the press is opened and the plates are shifted, the filter cakes will typically fall out from the chambers into a cake hopper or drum for simple removal. If the cakes remain in place, minor manipulation from a spatula will usually release them.
Interested in taking a deeper dive into how recessed chamber filter presses are designed and how they work? Learn more.
M.W. Watermark offers both stock and customized recessed chamber filter presses to accommodate your exact specifications. If you are in need of a recessed chamber filter press, replacement recessed chamber filter plates or other aftermarket parts and retrofits, contact us today.
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