Page 367 - Chemical Process Equipment - Selection and Design

330 SOLID-LIQUID SEPARATION
TABLE 11.14. Design and Operating Factors for Continuous Vacuum Filters
(a) Typical Factors for Cycle Design

% of Cycle
Submergence" Total
underb Max' Max ford Required
Effective Active Vac for Dewatering for Cake
Filter type Apparent Maximum or Pressure Washing Only Discharge
Drum
Standard scraper 35 30 80 29 50-60 20
Roll discharge 35 30 80 29 50-60 20
Belt 35 30 75 29 45-50 25
Coil or string 35 30 75 29 45-50 25
Precoat 35, 55, 85 35, 55, 85 93 30 10 5
Horizontal belt as rea'd as req'd lengthen as req'd as reqd 0
as req'd
Horizontal table as req'd as req'd 80 as req'd as req'd 20
Tilting pan as req'd as req'd 75 as req'd as req'd 25
Disc 35 28 75 none 45-50 25
=Total available for effective subm.. cake washing, drying, etc.
bValue for bottom feed filters assume no trunnion stuffing boxes, except for precoat. Consult manufacturers for
availability of higher submergences.
cMaximum washing on a drum filter starts at horizontal centerline on rising side and extends to 15 past top dead
center.
Dewatering means drainage of liquor from cake formed during submergence.

(b) Typical Air Flow Rates (c) Minimum Cake Thickness for Effective Discharge
Air Flow at Minimum Design Thickness
500 Torr Vacuum
Type of Filter [m3/(h)(m2)1 Filter Type (in.) (mm)
Rotary drum 50-80 Drum
Precoat drum 100-1 50 Belt 1/8-3116 3-5
Nutsche 30-60 Roll discharge 1/32 1
Horizontal belt or pan 100-1 50 Std scrapter 114 6
Coil 118-311 6 3-5
String discharge 114 6
Precoat 0-118 max 0-3 max
Horizontal belt 118-3116 3-5
Horizontal table 314 20
Tilting pan 314-1 20-25
Disc 318-1 12 10-13
[(a, b) Purchas, 1981; (c) Purchas, 19771.

TABLE 11.15. Typical Performance Data for Horizontal Belt Filters

Filter Slurry feed Wash ratio Solubles Final cake
area, characteristics (wt/wt based recovery moisture
Application m2 % solids pH t/hr on dry solids) % %
Dewatering
metallic
concentrates 8 40 - 20 - - 7
Brine
precipitate
sludge 25 12 - I 8 90 50
Calcine leach 60 45 10 78 1 99.7 14
Uranium leach
Pulp 120 50 1-2 300 0.4 99.3 18
Cyanide leach
gold pulp 120 50 10-11 80 0.6 99.6 20
(Delfilt Ltd.; Purchas, 1981).