Vertical Pressure Leaf Filter Systems

Vertical pressure leaf filter systems consist of multiple vertically arranged filter leaves housed within a cylindrical pressure vessel. Each leaf is constructed around a rigid drainage core covered with fine filter media — typically stainless steel mesh, woven cloth, or synthetic fabric — and connected to a central manifold that collects the filtrate. The unfiltered slurry or liquid is pumped into the vessel under pressure, flows radially through the leaves from both sides, deposits solids as a filter cake, and exits as clear filtrate through the manifold. Precoating with filter aids is commonly applied to achieve finer clarification and protect the underlying media. Filtration continues until the accumulating cake causes the differential pressure to reach a predetermined limit, signaling the end of the cycle. Cake discharge is accomplished through pneumatic vibration, hydraulic sluicing, or a combination of methods, with designs supporting either dry cake removal (via vibration after drying) or wet discharge (reslurrying with wash jets).

These systems are prized for delivering a large filtration area within a relatively small footprint, exceptional filtrate clarity, and reliable performance with low-to-moderate solids slurries. Typical applications include edible oil clarification, sugar syrup polishing, catalyst and activated carbon recovery, molten sulphur filtration, and various chemical processes. Key advantages include space efficiency, uniform cake formation assisted by gravity in some phases, and dependable operation at pressures ranging from 2 to 6 bar or higher depending on design.

Industrial Candle Filters

Industrial candle filters — also referred to as tubular or cartridge pressure filters — comprise an array of cylindrical filter elements (candles) installed vertically or horizontally inside a pressure vessel. Each candle consists of a perforated support core wrapped with filter media such as sintered metal, woven wire mesh, pleated fabric, or depth-type cartridges, enabling filtration either from the outside inward or inside outward. In the most common outside-to-inside configuration, slurry surrounds the candles, liquid is forced through the media under pressure, solids accumulate as cake on the exterior surface, and filtrate flows through the core and out via collection headers. Cake discharge is typically achieved through automatic back-pulsing, reverse flow with gas or liquid, or mechanical aids, allowing the system to remain closed during cleaning.

These filters are capable of achieving sub-micron retention levels, offer substantial dirt-holding capacity, and are well-suited for polishing operations or controlled thickening. They are widely used in pharmaceutical clarification, polymer melt filtration, fine chemical processing, food and beverage polishing, amine and glycol treatment, and oil refining. Their principal strengths include enclosed operation for hazardous or toxic materials, no moving parts during the filtration phase, automated cake release, and straightforward element replacement or regeneration.

Horizontal Filtration Systems

Horizontal filtration systems, most commonly horizontal pressure leaf filters, feature a horizontally oriented cylindrical vessel with vertically mounted filter leaves attached to a central or side-mounted manifold. This configuration maximizes available filtration surface area by permitting a greater number of leaves within a wider vessel. The feed slurry enters under pressure, coats the precoated or bare leaves, forms a filter cake, and produces high-clarity filtrate collected from the leaves. The horizontal layout supports large-scale batch processing and simplifies maintenance through retractable shell designs or removable leaf bundles that provide full access to the filtration elements for inspection, cleaning, or media replacement. Discharge is achieved via pneumatic vibration for dry cake, sluice washing for wet discharge, or other mechanical methods.

Horizontal systems excel at handling high flow rates and moderate solids loads in batch operations. They are extensively applied in edible oil refining, sugar decolorization and polishing, cocoa butter and chocolate liquor filtration, gelatine processing, and various chemical separations. Compared to vertical counterparts, horizontal designs often facilitate easier cake discharge in certain configurations, accommodate larger total volumes, and allow visual verification of cake release and media condition, although they generally occupy more floor space.

Coalescer Filtration Systems

Coalescer filtration systems are specialized for separating immiscible liquids — most frequently removing dispersed water droplets or hydrocarbon aerosols from gases, or water from fuels and oils. The heart of the system is a multi-layered coalescing element made of fine glass fibers, synthetic media, or pleated cartridges. Small droplets are captured through mechanisms of direct impingement, interception, and Brownian diffusion as the contaminated stream passes through the media. Captured droplets coalesce on the fibers into larger ones, which then drain by gravity to a collection chamber or separate phase section at the bottom of the vessel. In gas applications the liquid is shed downward; in liquid-liquid systems the heavier phase settles out.

Coalescers routinely achieve removal efficiencies for droplets as small as 0.1–0.3 microns and are frequently installed in multi-stage arrangements with upstream pre-filters to remove particulates. Major applications include compressed air and instrument air drying, natural gas and fuel gas conditioning for turbines, jet fuel and diesel dehydration, hydraulic and lube oil purification, and petrochemical mist/vapor elimination. Their primary benefits are protection of downstream equipment from corrosion and erosion, consistent product quality, and reliable performance in high-humidity or aerosol-laden environments.

Comparison of Filtration Equipment Types