MD, Propel Industries.
The purposes of washing are: (i) Removal of undesirable materials: clay, soft stone, roots, etc., (ii) Classification, and (iii) Dewatering.
Washing is usually accomplished through the following processes:
- Coarse material – direct washing on vibrating screens or scrubbers, when the clay content is very high or its plasticity is high.
- Materials extremely difficult to disaggregate may be treated in log washers before screening
- Fine materials – in sand washers
WASHING ON-SCREEN (Wet Screening)Washing on-screen is used to remove undesirable material, mostly clay and extremely fine particles. It is also employed for the classification of fines and/or moist materials whose screening is very difficult without washing.
Washing is performed by applying water jets through spray nozzles directed at a water curtain and under pressure at the material being classified, aiming to remove the impure particles adhering to the material.
The nozzles are installed in metallic pipes placed cross-sectionally in relation to the material flow.
For recovering fines (smaller than 3/8" or 10mm) and dewatering screens, sand washer, screw washers / spiral classifiers, one may use cyclones, filters, collectors, thickeners and so on.
Propel Sand Washer – Construction & ProcessPropel Sand washers are the classic machines for recovery of sand from the discharge water with the assistance of dewatering screens.
Propel Sand Washer produces high sand recovery (from 100 to 120) to increase production with a low running cost. Sand Washers require only low drive power and are distinguished by operation with a minimum maintenance and wear.
Design & Construction: Propel Sand Washers are of robust and firm design. The tank / trough is made of formed steel and completely welded with bolted wear buckets at the feed end. The spiral / screw is bolted adjacent to bucket wheel as mechanical safety device and for easy maintenance. This increases the machine lifetime. The machine is driven by low power one electric motor with a planetary gear box. The synchronous running of both bucket wheel & spiral shaft is controlled by VFD (variable frequency drive) system.
The horizontal shafts have spherical roller bearings, which are mounted in generously dimensioned bearing housings. The blades are arranged in a spiral to avoid impacts or power peaks in the transmission system. To achieve a long lifetime of replaceable blades & buckets, which are made of special wear-resistant steel, shafts are run at low speed.
Process: Crushed sand along with water (evenly mixture) is fed into the Sand Washer through a tubular pipe. The feed material enters the equipment in a non turbulent section on the dewatering wheel / bucket.
Sand gets settled on bottom of the tank. A slow moving spiral / screw transports the material towards the dewatering wheel just in opposite direction of water flow. The waste water flows over a weir at the opposite end of the machine. During this process clay (contaminates should be less than 10%) will be washed from the material and dissolved in the water. The dirt/clay dissolved in the water leaves the trough at the discharge end along with water outlet. The cleaned material segregated at the upper portion of the trough, is dredged by dewatering rotating wheel and then dropped from the buckets into the discharge chute / dewatering screen (optional) for getting a washed product at outlet.
For recycling of process water for recirculation, which has become of growing importance, Propel is able to integrate water clarification through sedimentation tank.
- Substantial trough design with wear plates at buckets & spirals.
- Rigid horizontal shaft with heavy duty spherical roller bearings.
- Replaceable blades made of wear resistant steel.
- Individually replaceable shaft journals.
- Reliable Planetary Gears with pin bush coupling.
- Transversal beam which support the drive assembly and bucket wheels.
- Extremely economical running costs.
- Large trough for clay free sediment of crushed sand.
- Heavy dewatering wheel.
- Screw conveyor which runs extremely slowly.
- Reduced slotted wear even for abrasive material.
- Electronic load dependant frequency controller which controls the speed according to the feed capacity, for optimal sand discharge with efficient dewatering effect.
- Low Wear
- Low energy consumption