02 BOPs / Woods D.R 2008 rules-of-thumb-in-Engineering-practice (epdf.tips)

5.14 Filter 171

3 min, fill with wash, 2 min; wash with volume = 5 times the cake void volume; air blow; unload, 6 min.

The time required for constant flowrate filtration = double the time for constant pressure filtration to reach the same volume of filtrate.

Leaf, pressure vertical: cycle (for wet cake): filter 2–80 h; open, dump, close 0.4–4 h; cake volume/unit 0.1–2 m3 corresponding to 5–90 m2 filter area; leaves on 75 mm spacing. Dp 250–400 kPa. cake buildup flux: 0.001 kg/s m2. Precoat: 0.68 kg/m2 filter. solid flux for precoat 0.06–0.18 kg/s m2. Filtrate flux through precoat = 0.1–1.1 L/s m2.

Leaf, vacuum: cycle: precoat; filter 0.6–20 h; wash-clean. Cake formation rate 1.3 mm/s; solids flux 0.009–0.02 kg/s m2 filter area. Cake thickness I 10 cm. Area per unit 1.2–180 m2; Dp I 80 kPa. Cake volume per unit: 0.1–4.5 m3. Precoat: liquid filtrate flux for pharmaceuticals: 0.0003–0.0017 L/s m2.

Leaf, horizontal pressure: cycle: precoat; filter 8 h; wash-clean. Availability per cycle for filtration 65 to 85 %. Cake thickness I 10 cm; solids flux 0.001– 0.04 kg/s m2 of filter area; filtrate flux: 0.34–1 L/s m2. Area per unit I 280 m2; Dp 100–700 kPa. Cake volume per unit: 0.2–4.5 m3.

Plate, horizontal vacuum: cycle: precoat, filter, 70 h; wash-clean: 2–4 h. solids flux: 0.003 kg/s m2 of filter area; area per unit I 6 m2; Dp I 80 kPa. Cake volume per unit: 0.06 m3.

Plate and frame: cycle time: feed, wash, unload, clean; filtration: 10 min–24 h, usually 2–8 h; wash 10–25 min. Cake formation rate I 0.7 mm/s; solids flux 0.02–0.07 kg/s m2 of filter area; filtrate flux 0.004–0.8 L/s m2 of filter area. Area per unit I 500 m2; Dp 400–1600 kPa. Cake thickness 2.5–5 mm. Cake volume per unit: 0.012–2 m3 corresponding to 1 to 160 m2 filter area for 25 mm plates; 0.024–4 m3 for 50 mm plates.

Diaphragm plate and frame: cycle: fill, stop when about 80 % of the plate has been filled: 0.2–0.5 h; squeeze, 0.25–0.4 h; discharge, 0.33–0.4 h. Post squeeze volume/pre squeeze volume = 0.63–0.75. Cake volume 0.003–7.8 m3. Fill at 700 kPa; squeeze at 0.85–1.5 mPa.

Deep bed: cycle: load 8 h; backwash 15 min; 93 % availability. Cake formation rate 1 q 10–5 mm/s; solids flux 0.02–0.5 g/s m2 of filter area; filtrate flux 1.3– 16.7 L/s m2 of filter area with fluid loading decreasing as solids feed concentration increasing; the usual value is 2.7 L/s m2. Area per unit I 25 m2; maximum depth 4.5 m. Gravity upflow or downflow with single or multiple media; pressure upflow or downflow. Use pressure units for small to medium fluid capacities where high terminal headloss is expected. Backwash at 6 L/s m2.

Cartridge: cycle: days–months. Cake formation rate I 0.000 067 mm/s; area per unit 0.3-0.7 and 1.5–15 m2.

Continuous:

Drum, gravity: cake formation rate i 3 mm/s; solids flux 0.15–0.47 kg/s m2 of effective filter area. Actual filter area 0.7–15 m2.

Drum, rotary vacuum: cake formation rate 0.01–17 mm/s; solids flux 0.008– 0.16 kg/s m2 of submerged filter area; filtrate flux 0.08–1 L/s m2 of submerged

172 5 Heterogeneous Separations

filter area. Total drum area per unit 0.585 m2; Dp I 80 kPa; rpm 0.4–1. Variety of options to remove cake:

–belt: submerged 35 %; air required 13–22 dm3/s m2. Thickness of cake: i 3–5 mm.

–roll: submerged 35 %; air required 13–22 dm3/s m2. Thickness of cake: i 1 mm.

–standard scraper: submerged 35 %; air required 13–22 dm3/s m2. Thickness of cake: i 6 mm.

–coil: submerged 35 %; air required 13–22 dm3/s m2. Thickness of cake: i 3–5 mm.

–string: submerged 35 %; air required 13–22 dm3/s m2. Thickness of cake: i 6 mm.

Wash ratio 1.5 water/solid. Agitate the feed pan to keep the feed solids in suspension but not interfere with cake formation. Solid flux for fine diameter minerals 0.09 kg/s m2 of total drum area at pressure drop across the cake = 60 kPa; coarse diameter minerals 0.35 kg/s m2 of total area at pressure drop across the cake = 10–20 kPa.

Drum, precoat rotary vacuum: submerged 35, 55, 85 %. Usually 85 %; air required 28–42 dm3/s m2. Thickness of cake: I 3 mm. Need low viscosity liquid. Filtrate flux: 0.004–0.07 L/s m2. Procedure to form the precoat: use maximum drum speed. gradually increase the submergence from 5–85 %.

Disk, rotary vacuum: cake formation rate 0.01–1.6 mm/s; solids flux 0.01– 0.55 kg/s m2 of submerged filter area. Total disk area per unit 0.4–300 m2; Dp I 80 kPa. Submergence 35 %; cake thickness i 13 mm. Air/vacuum: 8–25 dm3/s m2.

Table/pan gravity: cake formation rate 0.5–16 mm/s; solids flux 0.02–0.25 kg/s m2. Total table area per unit 8–200 m2; Dp I 80 kPa. Cake thickness i 20–25 mm. Air vacuum needed: 10–40 dm3/s m2.

Belt, gravity: dilute sludges with 0.5–8 % solids typically dewater in 20–80 s. Length 2.4 m. (Often combined with downstream belt press.)

Belt, vacuum: solids flux 0.08–2.2 kg/s m2; filtrate flux 0.038–1 L/sm2 area: for particles I 0.3 mm, 0.08–2 L/s m2; for particles i 0.3 mm, 2–12 L/s m2 . Area per unit 1–120 m2; Dp I 80 kPa; cake thickness 5–100 mm, usually 12 mm. Size on the filtrate flux. Vacuum air 25 dm3/s m2. Velocity I 0.75 m/s. Wash ratio 1.1–1.2 water/solids; width I 3 m. 22 h continuous operation plus 2 h routine maintenance. 1 L/s of sludge/m width.

Belt press: belt width 0.5–2.6 m with areas from 6.9–35.7 m2; belt speed 04–0.15 m/s. For feed concentrations I 5 %, usually liquid dewatering controls: liquid load 2.5–3.5 L/s m of belt width. For feed concentrations i 5 % solids throughput limiting: 0.15–0.275 kg/s m of belt width. Dp I 80 kPa.

Revolving drum: (microscreen). For waste water application with 6.7 L/s m2 loading. Rotary press: I 3 rpm; dewatering area: 1.25–5 m2. Solids flux 0.003– 0.127 kg/s m2 depending on the feed solids concentration in range 0.1–6 % solids. Product 20–75 % solids. See also Sections 5.17 and 9.11.

Ultrafiltration: see Section 4.22.

5.15 Leacher 173

Microfiltration: see Section 4.23.

Dissolved air flotation, DAF: see Section 5.16.

x Good Practice

Precoat: 0.75 kg/m2 to give a precoat thickness of 1.6 mm. Rate for precoat: concentration between 0.3 and 5 % w/w and at a rate of 0.7–1.4 L/s m2. This should give a Dp = 14 kPa. For leaf or rotary filters, maintain consistent pressure differential across cake once the cake is formed.

Consider adding body feed continuously when filtering gelatinous species.

x Trouble Shooting

“Poor clarity”: leak/cracks in cake/partially blinded septa/cake washing too fast/ flashing of filtrate/air in filter of feed liquid/changes in liquid properties/incorrect filter aid/change in temperature of pH/small diameter particles in feed than design/process upset.

“Short cycle/high pressure/low flow”: flow lines too small/obstruction in outlet line/ pump sucking air/pressure differential too low/wide fluctuations in feedrate/air trapped in filter/too high a filtration rate.

5.15 Leacher

x Area of Application

Percolation leach: particle diameter i 700 mm; liquid concentration 0.8 to 20 %; relatively fragile solid (e.g. seeds)

Immersion leach: particle diameter I 700 mm; liquid concentration I 20 %; relatively robust solids (e.g. minerals)

Combo leach: high feed concentration of solute, relatively robust solid. Supercritical solvent: usually CO2 for small capacity of high value products

especially for temperature sensitive foods, cosmetics and pharmaceuticals.

x Guidelines

– Percolation leach:

High solute leach rate; solvent percolation through the bed i 3 mm/s; 3–10 L/s m2; bed permeability i 200 mm2; low feed concentration of solute; 0.5–0.7 kg liquid solvent carryover from stage to stage/kg inert solid; solute diffusivities of essential oils 10–7–10–14 cm2/s; of sugar in sugar beets 10–5 cm2/s. Tend to use series of countercurrent contactors with time for diffusion and separation in each stage.

Rotating cells/baskets: capacity: 30 kg/s flaked soybeans in 10 m diameter unit; prepressed cottonseed q 0.66; unpressed cottonseed q 0.33; sugar cane q 0.33; canola q 0.33.

Buckets: 10 kg/s flaked soybeans with 40 buckets.

174 5 Heterogeneous Separations

Belt: 10 kg/s flaked soybeans with belt 20 m long q 0.3 m wide; 2–5 kg solvent makeup/Mg oil seed feed.

Drag-chain: 10 kg/s flaked soybeans with belt 20 m long.

–Immersion leach:

Low solute leach rate. Product of residence time q concentration of leachant for

acid leach = constant for a given particles diameter. Tend to have a separate leacher followed by system to separate and wash solids.

Pachuca: plus CCD, settler; particle diameter I 70 mm; solids 30–60 % w/w; agitator 0.07–0.2 kW/m3; for CCD 1.5–2 kg liquid solvent carryover/kg inert solid. Autoclaves: plus CCD: particle diameter I 70 mm; solids 30–60 % w/w; 0.7–1.3 kW/m3.

– Combo leach:

Tend to use countercurrent contactors with time for diffusion and separation in each stage.

Sloped diffuser with rotating screw: 10 kg/s sugar beets in 2 m diameter.

Column with rotating screw: 10 kg/s sugar beets in 0.3 m diameter unit. Trough-scroll: 10 kg/s sugar beets in 3 troughs.

Rotary diffuser: 10 kg/s sugar beets in 5 m diam. unit.

–Supercritical solvents:

Batch process operating at T i 31 hC and pressures i 7.3 MPa. Solvency is

intermediate between nonpolar and weakly polar solvents. Contact times 0.1 q usual leach times.

x Good Practice

Rate of dissolution of solid minerals increases by factor 1.5–2 with 10 hC increase. Supercritical carbon dioxide: manage aqueous contamination or use alloys.

5.16

Liquid–Solid: Dissolved Air Flotation, DAF

x Area of Application

Particle diameter 0.1 to 50 mm with typical target diameter 2 mm; feed solid concentration 0.002 to 0.08 % w/w; i 80 % removal efficiency.

x Guidelines

Bubble size 70 to 90 mm; air: solids 0.005 to 0.1 kg/kg; liquid loading 0.5 to 2 L/s m2. liquid residence time 20 to 200 min with a minimum depth of 1.8 m. If feed concentration is I 400 mg/L use about 50 % recycle.

5.18 Solid–Solid: General Selection 175

5.17

Liquid–Solid: Expeller and Hydraulic Press

x Area of Application

Particle diameter i 1 cm; liquid concentration 10 to 60 %.

x Guidelines

Batch:

Hydraulic press: 30–60 MPa. Cycle: load, press, discharge.

Continuous:

Expeller:

– expelling essential oils: Fullpress capacity 0.02–5 kg/s; prepress capacity (which will be followed by leaching, Section 5.15) = 2 q full press capacity (where only expelling is used to remove the essential oils); prepressing 2.2 Mg/d cottonseed/ rpm; relative capacities depend on the seed being processed: cottonseed and soybean q 1; copra, wet corn germ, canola q 0.75–0.82; flax seed, safflower q 0.62; power 100–200 kJ/kg cottonseed prepress with the value increasing with feed capacity.

– dewatering polymers; capacity 1–1.5 kg/s; power 200 increasing to 450 kJ/kg as capacity increases. Related topics: dryer, Section 5.6, screens, Section 5.7, and centrifugal filters, Section 5.13.

5.18

Solid–Solid: General Selection

To separate solids having about the same density and particle size, use flotation, electrostatic and magnetic separators. Particle diameter must be i 20 mm.

To separate solids having about the same density but with a range of particle size, separate based on cut diameter and use air or liquid classifiers such as cyclones, hydrocyclones or spiral classifiers: Particle size 25–2000 mm; feed solids concentration 5 to 40 %. Cut diameter is the particle diameter that has equal chance to report to either the overflow or the underflow streams.

To separate solids having about the same particle size but with a different density, separate based on cut density and use Concentrators such as jigs, tables, sluices or Dense Media Separators, DMS. Particle diameter must be i 40 mm. Concentrate before flotation if the feed assay of mineral is I 0.3 %.

To separate solids having different densities and particles sizes, then use combinations, such as a screen to provide narrow size range followed by concentrators.

For minerals, the liberation size is 0.01 of the diameter of the mineral crystal.

1765 Heterogeneous Separations

5.19

Froth Flotation

x Area of Application

For systems with a narrow range of both density differences and particle size. Density ratio 1–1.3; particle diameter usually 20–50 mm although occasionally the diameter could be as large as 200 mm. Feed concentration of target solid i 0.5 %.

x Guidelines

Condition the solids to alter the wettability of the mineral and the gangue. The fundamental surface wettability for sulfide ores is different from oxides, silicates and salt-type minerals. pH is a critical variable.

Typical conditioning chemical additions include collector about 0.01–0.1 kg/Mg solids, frother about 0.01–0.05 kg/Mg solids, activator about 1–4 kg/Mg solids, depressant about 0.02–2 kg/Mg solids.

Allow 6 min contact for conditioning. Air: 1–1.5 m3/m3. Bubble size about 1000 mm. Flotation rate constant is 0.2–1 min–1; sink rate constant is 0.005 min–1.

Flotation cells: working volume = 80 % of nominal cell volume.

Mechanical cell: for fast float, sequential separation and relatively coarse particle diameter; 1.6–6 kW/m3 cell volume with usual 2.6–6 kW/m3 cell volume. Larger values used for smaller sized cells.

Pneumatic cell for relatively dilute feed concentrations and smaller particle diameters. Air blower 0.5 kW/m3 cell volume. Typical solids throughput 0.4–0.8 kg/s m3; feed concentration 10–40 % w/w; air escape velocity 0.02 m/s. Float times 6–20 min.

Typically three units: the rougher, cleaner and scavenger.

Rougher: feed concentration: 30 % w/w; modest amount of flotation agent; moderate agitation; relative flotation constant: 1. Usually 1–2.5 m3 cell volume/kg; 0.8 kg/s m3.

Cleaner: feed concentration: 10 % w/w; more flotation agent; gentle agitation; relative flotation constant: 0.5. Tails are often reground, sometimes thickened. More flotation time is required. Usually 2–6 m3 cell volume/kg; 0.4 kg/s m3.

Scavenger: feed concentration: 30 % w/w; much more flotation agent; intense agitation; relative flotation constant: 2. Float is often reground.

Rougher + cleaner: for single mineral that is easy to float and grade is important.

Rougher + scavenger: for single mineral that is not easy to float and both grade and recovery are important.

Rougher + scavenger + cleaner + scavenger: for highly concentrated feed that is easy to float.

5.20 Electrostatic 177

x Good Practice

Fresh grinds are easier to float. Conditioning time is critical. Fluctuations in flowrate and solids concentration affect mainly the conditioning and not the flotation. Consider softening the water. Deslime the feed to remove particles of diameter I 20 mm.

5.20 Electrostatic

x Area of Application

For systems with dry particles, no slimes or organic coatings, a narrow range of both density differences and particle size and a difference in conductivity. Particle diameter 40–3000 mm: usually 80 to 1000 mm; feed concentration of target species 5 to 75 %. Good conductors have relative permittivity i 11; poor or nonconductors have relative permittivity I 10; threshold voltage to make species conducting is 1–10 kV/cm.

x Guidelines

Select voltage where one species conducts and the other does not. Corona-active electrode rotary drum: handles wide range of particle diameters from 75–1000 mm; high capacity I 0.75 kg/s m of drum width; high efficiency 95 %; separates good from poor conductors. 0–40 kV DC, 0.5–1 mA/electrode; insensitive to humidity and temperature; often can recycle the middlings with recycling 10–30 % OK.

Active electrode rotary drum: trouble handling fines; capacity I 0.5 kg/s m of drum width, moderate efficiency; separates good from poor conductors or two semiconductors. 0–30 kV DC, 0.04 mA/electrode. The voltage gradient must be sufficient to charge target particles. operates best in a controlled environment.

For roughers and scavengers: set the active polarity so that the valuable minerals become conductors.

For cleaners and recleaners: set the active polarity so that the gangue and middlings become the conductors.

Collect middlings if the valuable target is trapped in the gangue; if the density of the nonconducting is heavier than the conducting and if the feed has a wide range of particle diameters.

x Good Practice

Consider increasing the temperature because for every 50 hC increase the conductivity often increases by a factor of 10.

1785 Heterogeneous Separations

5.21 Magnetic

x Area of Application

For systems with a narrow range of both density differences and particle size; particle diameter i 50 mm; feed concentration of target species 0.4 to 40 %.

Magnetization = product of the mass magnetic susceptibility and the magnetic field, T m3/kg

Ferromagnetic species: magnetization i 10–4 T m3/kg. Paramagnetic species: magnetization 10–8 I value I 10–5 T m3/kg.

Batch: cycle: load, clean.

Plate: batch: magnetization i 10–4 T m3/kg; particle diameter i 6 mm; feed concentration of magnetic I 0.01 % w/w. Primarily to remove tramp ferrous metal. Grate: batch: magnetization i 10–4 T m3/kg; particle diameter I 1.8 mm; feed concentration of magnetic I 0.01 % w/w. Primarily to remove tramp ferrous metal.

WHGMS (wire, Kolm-Marston): batch: magnetization i 2 q 10–9 T m3/kg; particle diameter 1–30 mm; feed concentration of magnetic I 0.05 % w/w. Solids concentration in water 20 %.

WHGMS (grooves, Jones): batch: magnetization i 2 q 10–9 T m3/kg; particle diameter 200–1000 mm; feed concentration of magnetic I 50 % w/w; solids concentration in water I 50 %.

Continuous:

Pulley: magnetization i 10–4 T m3/kg; particle diameter i 6 mm; feed concentration of magnetic I 0.01 % w/w. Primarily to remove tramp ferrous metal. Belts/cross or in-line: magnetization i 10–4 T m3/kg; particle diameter i 6 mm; feed concentration of magnetic 0.01–10 % w/w. Primarily to remove tramp ferrous metal.

Belts/cross HGMS: magnetization i 10–4 T m3/kg; particle diameter 150–1500 mm; feed concentration of magnetic 0.5–2 % w/w. Primarily to remove tramp ferrous metal.

Wet belt: magnetization i 10–4 T m3/kg; particle diameter 100–2500 mm; feed concentration of magnetic 0.3–2 % w/w.

Dry drum/LGMS: magnetization i 2 q 10–5 T m3/kg; particle diameter 0.1–100 mm; feed concentration of magnetic 1.5–75 % w/w.

Dry drum high speed/MGMS: magnetization i 2 q 10–5 T m3/kg; particle diameter 100 mm–30 mm; feed concentration of magnetic I 10 % w/w.

Dry rotor HGMS (induction): magnetization i 4 q 10–8 T m3/kg; particle diameter 70–2000 mm; feed concentration of magnetic I 0.05 w/w.

Wet drum/LGMS: magnetization i 10–4 T m3/kg; particle diameter 70 mm–6 mm; feed concentration of magnetic i 25 % w/w.

WHGMS (carousel, BoxMag, Frantz): magnetization i 2 q 10–9 T m3/kg; particle diameter 200–1000 mm; feed concentration of magnetic I 50 % w/w; solids concentration in water I 50 %.

5.21 Magnetic 179

x Guidelines

Consider wet processing for particle diameter I 6 mm to minimize dusting and electrostatics.

For particle diameter i 150 mm prefer wet belt; I 150 mm prefer wet drum. Match magnetic gradient to the diameter of the particles. Match the machine to the liberation size (liberation size is 0.01 of the diameter of the mineral crystal,

Section 5.18).

For wet machines pump 4 Mg water/Mg solids although 90 % of the water can be recirculated.

Batch:

Plate: batch, remove tramp metal from solids moving in ducts or on conveying belt. Usually keep burden depth I 20 cm; magnetic field 0.3 T; gradient 0.04 T/cm.

Grate: batch, magnetic field 0.05 T; gradient 0.02–0.5 T/cm.

WHGMS (wires, Kolm-Marsden): batch; 100 mm wires; 10–80 kg/s per pole; 10–160 L/s m2 gap cross sectional area; solids concentration in water 20–25 % w/w; induced magnetic field 1–2 T; gradient 1000 T/cm; 35–42 kW/pole; 1–18 kJ/kg solids for magnet and 4.5 kJ/kg pumping; solids loading before unload 0.1–0.5 Mg/m3 of matrix.

WHGMS (grooves): batch, 0.03–0.04 kg/s; 8–12 kg/s.pole; solids in water I 40 % w/w; induced magnetic field 1–2 T; gradient 0.1–1000 T/cm, usually 10–200 T/cm; 16 kW/pole; 1.8 kJ/kg solids collected for magnet; feed I 50 %w/w solids in water.

Continuous:

Pulley: remove tramp metal from solids exiting from a conveyor belt. Usually keep burden depth I 20 cm; magnetic field 0.1–0.3; gradient 0.04 T/cm.

Belts/cross or in-line: I 1 kg/s.m width; gradient 0.1–1 T/cm; belt speed 1 to 2 m/s. Belt with rotating disk: 0.2 kg/s m width; magnetic field 0.04–0.1 T; gradient 0.1–1000 T/cm.

Wet belt: 3 kg/s.m width; magnetic field 0.3 T; gradient 0.1–1 T/cm.

Dry drum/LGMS: 80–200 kg/s m width of drum, 60–90 dm3/s.m width for drum diameter I 1.2 m; 25–35 rpm, peripheral speed 1–1.5 m/s; magnetic field 0.04–0.1 T; gradient 0.001–0.5 T/cm; drive power 2–5 kW/m width.

Dry drum high speed/MGMS: 0.5–20 kg/s m width, 0.8–20 dm3/s m width with capacity decreasing as magnetization decreasing; 2.5–7 m/s with peripheral speed increasing as the number of poles increases from 6 to 44; 50–200 rpm; as particle diameter decreases, the number of poles and the rpm increases; for highest recovery operate at lower rpm; for higher incoming concentration of mags and more efficient recovery of middlings operate at higher speeds; magnetic field 0.04–0.1 T; gradient 0.001–0.5 T/cm; drive power 10 kW/m width.

Dry rotor HGMS (induction): 0.8–1 kg/s m width; induced magnetic field 1–2 T; gradient 0.001–1000 T/cm, usually 10 T/cm.

Wet drum/LGMS: 1–5 kg/s m width; 4–25 L/s m width; water velocity 0.5 m/s; drum peripheral speed 2 m/s; 20 rpm; diameter 0.75 m; magnetic field 0.04–0.1 T; gradient 0.001–0.5 T/cm; constraint is the amount of magnetic mate-

180 5 Heterogeneous Separations

rial discharged from the drum; feed I 25 % w/w solids in water; drive power 1–2 kW/m width.

WHGMS (carousel, BoxMag, Frantz): continuous 1–5 kg/s pole, 10–50 L/s m2 gap cross sectional area; usual canister cross sectional area 0.5–3 m2; induced magnetic field 0.1–2 T; 1–6 MJ/Mg solids collected; feed solids concentration in water 30–50 %.

x Good Practice

For compounds containing ferric species, consider roasting particles at 55 hC to increase magnetism.

For dry machines, keep the moisture in the feed I 0.5 %.

For high speed dry drum particle diameter in the feed I 3.2 mm use a star feeder; particle diameter i 3.2 mm use vibrator.

5.22 Hydrocyclones

For solid–solid separations; see Sections 5.5 and 5.9 for separation of liquid–solid for Guidelines.

x Area of Application

Cut diameter 5 to 1000 mm; capacities up to 50 kg/s per unit.

5.23

Air Classifiers

x Area of Application

Separate solids with similar densities based on cut diameter. Conveying fluid is a gas such as air. Contrast with hydrocylcones and spiral classifiers where the conveying fluid is liquid such as water. Particle cut diameter 30 to 1000 mm. Particle diameter i 1.5 mm. Feed concentration of target solid 4 to 60 % w/w.

x Guidelines

Zig-zag: cut diameter 100 to 10 000 mm; capacity 0.01 to 0.08 kg/s. Gas centrifugal separator: cut diameter i 20 mm; capacity I 15 kg/s. Gas cyclone: cut diameter 10 to 50 mm; capacity I 15 kg/s.

Gas gravitational inertial classifier, GIC: cut diameter 50 to 200 mm; capacity

I 300 kg/s.

Gas Mikroplex spiral: cut diameter 2 to 20 mm; capacity 0.01 to 1 kg/s. Gas Nauta-Kosakawa: cut diameter 3 to 300 mm; capacity 0.01 to 1 kg/s.

Gas classifiers for MSW: cut diameter i 100 mm with capacities up to 20 kg/s. Solids to gas ratio 2 to 8 w/w. Solids loading 2 to 4 kg/s m2.