Drytech - Flash Dryers

Flash drying uses a heated gas to pneumatically convey the feed up a flash tube and into a primary air separation device; most commonly a cyclone. Air is induced or forced into the feed area through a hot gas generator where it entrains the feed and flashes off the moisture as it conveys. The product is fed into the throat of the feed area in a controlled fashion. The particles attain a velocity in the order of 80% of the conveying velocity. Secondary dust collection such as multi clones, baghouses, scrubbers and electrostatic precipitators are required for fine products.

• Flash Dryers are designed for numerous processing applications but are highly suitable for temperature sensitive material as well as fine materials.
• Flash dryers are highly flexible in terms of layout and configuration and can be designed to suit the available space in an existing plant. Suitable for filter cake drying.
• Materials of construction can range from painted mild steel, through to various grades of stainless steel to special alloys depending on the processing environments and conditions.
• Heat sources range from steam, thermic oil, electric, gas, liquid fuel burner systems and coal-fired fluid bed combustors.
• Flash dryers have very high thermal efficiencies with very short residences times.
• Drytech has flash dryers in operation drying material with feed moistures in excess of 60% moisture.
• All equipment is tailor designed to suit the processing requirements.
• A unique aspect of a Drytech flash dryer is our unique feed management system which guarantees a steady homogenous flow of the feed material to the dryer resulting in a smooth and reliable operation.
• Materials processed: copper and nickel concentrates, platinum concentrate, chrome sands, tin concentrate, cobalt hydroxide, kaolin, calcium hypochlorite, lime, gold tailings, ammonium metavanadate, REE concentrates, graphite to name a few.

Feeding/discharge:

Automatic and continuous. Vibrators, screw feeders, rotary airlocks, double flap valves, gravity chutes. Backmixing is most effective on sludges. Feed introduced into airstream via venturi or use of disintegrator technology.

Feed Characteristics:

Slurries, pastes, and sludges (all with back mixing), friable filter cakes, powders, granules. Feed needs relatively consistent particle size. Very large particles present challenges. Low to high feed rates

Heat Source:

Steam, electrical, coal, liquid fuels, or gas

Exposure:

Mostly Direct. Flow is co-current.

Residence time:

Extremely short (seconds). Residence time can be altered by increasing hold up times in cyclone.

Extraction:

Normally induced. Systems can have combustion, forced and induced draft fans for operation.

Dust Collection:

Cyclones, baghouses, scrubbers, Electrostatic precipitators. Systems require significant dust collection since this is the product collection mechanism.

Control:

PLC, infrequently solid-state controllers. System controls on discharge temperature. Can modulate energy and feed.

• Very intimate contact with air/gas stream
• Excellent transfer of energy
• Ideal for heat sensitive, explosive or reactive products
• Small real estate requirements
• Flash tube is flexible, can be routed within plant constraints
• Low maintenance - few moving parts
• High-temperature operation

• Loss of power will cause the product to fall into the dryer base
• May cause size reduction due to attrition and impact
• High energy costs for fans and dust collection
• Products displaying a high degree of bound moisture may not be suitable for this technology
• May be susceptible to high wear if improperly accounted for