The Vacuum Disk Filter consists essentially of a slowly revolving drum, the lower half of whose circumference is submerged in the pulp to be filtered. The filtering medium is applied all around the periphery, which is divided up into a number of separate segments, more or less isolated from one another.
The vacuum is applied through the axle bearing by means of a header valve which is so arranged that at a certain point in the revolution of the drum the vacuum connection is severed and compressed air admitted under the ceramic filter medium which serves to detach the cake and allow it to drop onto a metal deflector or scraper, whence it slides down to the residue discharge launder. As the newly formed and adherent cake rises from the bath of slime pulp it comes under the action of a number of atomising spray nozzles by means of which the wash liquor is distributed over the surface and is at once absorbed, tending to act as a wash for displacing the value-bearing solution.
Disk Filters consists of a number of parallel, individual, cloth-covered disks mounted on a hollow shaft through which suction and compressed air may be applied. The lower halves of the disks are submerged in the slime tank. The disks are divided into independent and removable sectors. Wash water may be applied from spray nozzles. The assembled disk and shaft section is shown in Fig. 32 (see also Fig. 33).
The American disk filter is a continuous machine of mechanical simplicity. It occupies small floor space and presents a larger filter area or surface in proportion to space filled than any other filter. Inflation of the filter bags during each discharge period keeps the cloth in good condition, and the cake discharged has low moisture content. The changing of filter cloths and the sectors is done easily and quickly. No pulp agitator is needed in the tank. This filter is made by the Oliver United Filters in four sizes: 4, 6, 8½, and 12½ ft. in diameter with 1 to 12 disks.
Product gallery
DISK ROTARY VACUUM FILTER OPERATING VARIABLES
Rotary Vacuum Filter production depends up
on balancing four operating variables, DENSITY of the feed, SPEED of the DISC, condition of the FILTER SECTORS and the INCHES OF VACUUM. (Vacuum is measured in inches that a vacuum can lift a column of mercury) the density of the feed is controlled by the source it comes from (thickener or holding tank).
As the operation of a thickener was discussed a little earlier you already know how to operate it. The holding tank is another story. What is there to operating a tank? It’s only function is to provide storage room for the filter feed! Unfortunately that depends upon the type of equipment
available and how easy the concentrate is to filter.
The problem, that is encountered, is too much wat
er trapped in the circuit without a means of escape. This situation stems from either having a pump, which has uncontrolled gland water, in the circuit, or the feed to the tan
k having too low of density. This may mean that there is more water in the concentrate than the filter can remove. If you have difficulty filtering the concentrate the circuit will have to run longer to filter the same amount of mineral. The extra gland water and the lowered density to the filter boot will mean that filter will not be effective in removin
g the water or the concentrate. The concentrate that is returned to the tank by way of the overflow, line will reduce the storage tank’s capacity.
The correction of these problems require balancing the four operating variables to the problem. To know how to balance the variables it is a good idea to look at the method that the filter uses to filter the material. When the concentrate is pumped into the boot it has a density. A determined percentage of concentrate with in a set volume of slurry. The filter sectors as they enter the slurry subject the slurry to a vacuum, this vacuum only effects the concentrate particles within a set distance from the filter sectors. The effects of the vacuum become less the farther away from the sectors you get. When you filter the material the density quickly drops to start with, this is due to a lot of mineral close to the sector and-easily picked up. The size of the particle will also dictate the spee
d that it is filtered. The larger material presents a larger mass for the vacuum to act on. Considering both the large particle and the smaller particle are in suspension in water
the resistance to movement is small. This makes the larger particles move easier as the vacuum effects them the greatest.
The capacity of a filter depends largely on the nature of the material to be filtered, particularly the amount of fine material and slimes and the percent solids. The following are Disk Filter capacities, on average:
Copper flotation concentrates:
150 to 300 lbs. per sq. ft. per 24 hrs.
Lead and zinc flotation concentrates:
300 to 630 lbs. per sq. ft. per 24 hrs.
Cyanide tails:
300 to 600 lbs. per sq. ft. per 24 hrs.
Coal flotation concentrates:
1500 lbs. per sq. ft. per 24 hrs.
