Industrial rotary drum vacuum filter

01

Size the drum, its cells, speed and loading

In ANDRITZ's Krauss-Maffei TSF vacuum drum filter, the drum shell is divided into cells and covered by a filter cloth; approximately 37% of the filtration area is submerged in the suspension and the drum rotates at up to 4 rpm. A liquid seal pump builds the vacuum and is connected to the drum cells via separators, control head and filtrate pipes, so each point of the drum passes through cake formation, washing, drying and discharge zones in turn. The range runs from the TSF 9.2 — 920 mm drum, 250–2,000 mm wide, 14 cells, 0.72–5.80 m², 1.5 kW drive — to the TSF 41.8 — 4,180 mm drum, 7,500–9,000 mm wide, 32 cells, 100.00–118.00 m², 11.0 kW, 68–70 t operating weight. ANDRITZ lists particle sizes of 1–300 μm, filtration capacity of 100–2,000 l/m²h, solids throughput up to 1,500 kg/m²h and operating temperature up to 95 °C. [1]

The ANDRITZ YU drum uses a single cell instead: up to 93% of its filtration area is under vacuum, it rotates at up to 30 rpm to form a thin cake discharged by a gas pulse (blow-off), and it is listed for 50–300 μm particles, 0.1–35 m², up to 4,500 l/m²h and up to 3,500 kg/m²h of solids. Its 3’ × 3’ size has a 900 mm drum, 915 mm wide, 2.8 m² and a 4 kW drum drive excluding the vacuum and filtrate pumps. [2]

Filtration Services, a drum filter maker, says rotary drum vacuum filters range from 1 m² to 60 m² of filtration area, with smaller and larger units available, and that “In general, rotary drum vacuum filters operate within the range of 0.1 and 1.0 rpm”, with exceptions. It sizes the area from the filtration flux rate — mass or volume per unit area per unit time, such as kg/m²/hr — combined with a mass balance, and states that the flux rate and cake moisture can only be determined by test work. Komline's rotary drum vacuum filter leaflet quotes a filter rate up to 160 lb/ft²/hr. [4] [3]

Editorial calculation: the drum's filter area is close to π × diameter × width, so the TSF 9.2 at 0.92 m × 2.0 m gives π × 0.92 × 2.0 ≈ 5.78 m², against 5.80 m² listed; and 160 lb/ft²/hr × 4.882 (kg/m² per lb/ft²) ≈ 781 kg/m²·h. [1] [3]

Give the supplier the slurry (solids, particle size, solids concentration, temperature, liquid and its vapour pressure), required solids or filtrate rate, target cake moisture and wash requirement, results of leaf or pilot tests if available, gas-tight or ATEX need, materials of construction, discharge preference, and site utilities. Ask for the drum diameter and width, filter area, number of cells, speed range, submergence, drive power excluding vacuum and filtrate pumps, vacuum pump size and operating weight.

02

Choose the discharge, cake thickness and vacuum

Komline lists five discharge designs. Precoat discharge applies a powder precoat to prevent blinding the filter media and suits slimy, sticky, oily and blinding solids, clear filtrates and very thin cakes. Scraper discharge uses air blowback to release the cake above the scraper and suits fast-filtering, granular or crystalline solids and cakes in excess of 1/4″ thick. String discharge lifts and releases cohesive or gelatinous cakes on parallel strings; roll and Flexibelt belt discharge are the other two designs. [3]

Filtration Services states that, except on precoat filters, the cake should be at least 5 mm thick to discharge from the drum, and that a precoat filter's cake is around 1 mm thick. Its precoat bed of perlite, diatomaceous earth, wood flour, cellulose or starch is up to 150 mm thick when first applied, and a knife that advances in increments of 5 microns per revolution shaves off the blinded layer; because the bed is used up over hours or days and must be recoated, it describes precoat units as batch in that sense, and unsuitable where the solid is the product. [4]

Meckey's MKPF pre-coating rotary-drum vacuum filter table lists vacuum of 0.04–0.06 MPa, capacity of 0.32–0.56 m³/m²·h and drive power of 1.5–7.5 kW across the MKPF4 to MKPF70 sizes. [5] Editorial calculation: 0.04–0.06 MPa equals 0.4–0.6 bar of vacuum.

Filtration Services adds that the maximum temperature is limited by the polymeric parts and the liquid's vapour pressure: an aqueous liquid limits it to around 65 °C because vacuum can make it boil, while polypropylene and polyethylene parts are stable up to about 85 °C. ANDRITZ rates its TSF to 95 °C and for gas-tight operation up to 70 mbar. [4] [1]

03

Scraper, precoat, folding-belt and starch-dewatering drum filters on supplier sites

Listings include scraper, precoat and folding-belt vacuum drum filters, precoat and belt vacuum drum filters for food processing, and vacuum drum filters for starch dewatering. Gravity drum screens for aquaculture and wastewater and pressure drum filters are different products and are not linked here.

04

Drum cells, control head, cloth or precoat, trough, vacuum pump, washing and discharge

The control head is what turns the cells into zones: ANDRITZ connects each cell through it to the separators and filtrate pipes, so a point on the drum passes cake formation, washing, drying and discharge in one turn. [1]

05

Drum size, filter area, speed, vacuum, solids rate and temperature limit for a drum filter

Cake moisture and the solids rate for your slurry come only from test work, as Filtration Services states; the ranges in the other rows are makers' published spans to check an offer against. [4]

06

Send the slurry data and the target together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Slurry: [solids; particle size; concentration; temperature; liquid]
Target: [solids or filtrate rate; cake moisture; wash]
Tests: [leaf or pilot test results]
Filter: [area; drum diameter x width; cells; speed]
Discharge: [scraper; precoat; string; roll; belt]
Vacuum: [level; pump; gas-tight or ATEX]
Materials and quantity: [wetted parts; units]

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