Filtration Equipment – Filter Presses, Thickeners, and Sand Filters
Filtration equipment separates solid particles from a liquid. It also thickens or clarifies the resulting liquid solution. It’s commonly used to handle hydraulic and quench oil, diesel fuel, machine tool coolants and other industrial fluids.
Gravity filtration equipment uses the hydrostatic pressure of a false bottom to generate a flow of filtrate. This includes sand filters, gravity nutsche tanks and bag filters (felt or woven-fabric filters).
Filter presses separate liquids and solids using pressure filtration. During the fill cycle, slurry is pumped into the filter and distributes evenly between the plate chambers. The slurry deposits solids on the filter cloth and forms a filter cake. The filtrate then exits through the filter plates and into discharge ports while the slurry is pushed back into the plate chambers to repeat the process. This batch process is ideal for dewatering challenging sludges like mining tailings and lead-acid battery recycling sludge.
Each filter press is designed based on industry and application requirements to provide trouble-free, economical dewatering. A variety of slurry capacities are available for both manual overhead and automatic sidebar filter presses. There are also explosion-proof filter presses and sanitary models for use in harsh environments such as chemical processing plants.
During the operation of the press, the hydraulic closing cylinder locks the filter plates together to make a water-tight seal. The corner discharge eyes, or manifolds, connect the drain fields of each filter plate with the internal piping. The compression mechanism consists of a motor (equipped with advanced overload protector) filter-equipment reducer, gear pair and screw, which pushes the compaction plate to compress the filter pack. Depending on the type of filter press, additional components can be added to enhance functionality and operation including filter cloth washing frameworks and trickle plate systems.
A thickener separates solids from liquid in a wide range of industrial applications. The valuable product can be the thickened solids or the clarified liquid, depending on the application. Typical applications include densifying product for efficient processing, countercurrent decantation (CCD) washing, and clarifying wastewater streams and tailings management in mining and aggregate processing.
A slurry thickener is typically a large cylindrical tank with a top-center mounted rotating mechanism that gently spins rakes and paddles to agitate sludge and prevent bed mass accumulation. As sludge settles, the rakes and paddles move the solids to a central opening or discharge. PHOENIX HiFlo High Rate Thickeners clarify wash plant effluent water and thickens the slurry to 40-45% solids, greatly reducing the amount of slurry that is pumped to a slurry pond or tailings storage basin.
The thickened slurry can be pumped to a filter press or centrifuge for further dewatering. Or it can be sent directly to a dam, pond or river for disposal. Either way, the slurry is substantially reduced in volume which reduces the overall slurry pond size, pumping costs and energy consumption. The HiFlo thickener is available with several standard and custom configurations including bolt-together tanks, flat bottom tanks, a fabricated sag steel floor on larger diameter tanks and a rake lift or trough/discharge system. State-of-the-art feedwell design options and auto-dilution options allow for maximum density underflow, reduced needs for flocculants and higher throughput.
River strainers rank high on kayakers’ lists of river hazards, and for good reason. These obstructions allow water to pass through but catch and pin larger objects like boats and people to the bottom of the river. If you encounter one of these deadly blockages, your best bet is to exit the river and look for a safer path forward.
A strainer is a kitchen gadget with a more specific purpose than a colander or sifter. Both a strainer and a colander feature filter-equipment large perforated holes, but the mesh of a strainer is smaller to provide a higher level of filtration. In addition to rinsing rice, strainers are useful for skimming solids from hot oil and blanching pasta or vegetables. Strainers come in several sizes and shapes, including chinois and China cap strainers that have a conical basket for pushing foods like custard through finely woven mesh.
A basket-type strainer has a larger screening area than a Y-type strainer, which reduces the frequency of blowdown for cleaning. They are also available in a duplex configuration to facilitate system uptime during maintenance. They’re often fabricated from stainless steel, but in steam applications a monel screen is preferable to avoid the formation of slag. These types of strainers are also available in a variety of sizes, from small to industrial, with single- or multi-cartridge designs for any flow application.
In sand filters, the biological and physical processes are used to treat wastewater. The sand in the filter bed is home to a miniature ecosystem of organisms that consume organic matter, including bacteria and protozoa. The organisms also help prevent a thick layer of material from forming on the top surface of the sand, which would otherwise clog the filtration system. This balance between the various life forms in sand filters results in highly efficient treatment systems that require minimal operation and maintenance.
Sand filters are usually at least partially above ground. They consist of a liner, underdrain pipes and a graded layer of washed gravel or crushed stone that holds the sand filter media. The sand in the filtration system should have a uniformity coefficient (Cu) of between 1.3 and 1.5 to ensure that water can pass through it.
The sand in the filter is raked or rinsed as part of routine maintenance. When this process is interrupted, the sand in the sand filter becomes polluted and must be replaced. The sand in industrial sand filters is typically sourced from outside of the plant, although it can also be reclaimed from pool owners’ pools.
Recirculating sand filters have lower hydraulic loading rates than single-pass sand filters and can be more economical to operate. They also require less land area than centralized sewage treatment plants.