Fluid bed dryer delivers for dolomite quarry

A Ventilex fluid bed dryer/cooler at a dolomite quarry has increased sand production, reduced fuel and power consumption and improved environmental and working condition benefits

A Ventilex fluid bed dryer/cooler installed at WBB Minerals Warmsworth dolomite quarry as part of a GBP4.5m investment has proven to successfully help meet the new plant objectives of increased sand production, reduced fuel and power consumption and improved environmental and working condition benefits.

Supplied by the Dutch company Ventilex the dryer unit is totally sealed and sound insulated to eliminate dust emission and greatly reduce noise levels.

Fuel consumption has been reduced by 30% for a given output thanks to extensive thermal insulation, a high drying air temperature of 400 to 450C, easier burner/dryer control and more efficient use of air flows within the dryer/cooler.

A further benefit is that the fluid bed unit is smaller than a rotary kiln dryer of the same capacity so that the building to house the dryer is smaller and less expensive.

A noisy and dusty rotary kiln dryer was used in the previous plant.

The Ventilex dryer/cooler is of unique design, being fully mounted on adjustable pneumatic dampers and shaken at low speed by an eccentric crank-shaft mechanism that induces both a forward conveying action and a lift giving the particles a degree of aeration.

This reduces the flow of air needed to achieve and maintain fluidisation, which in turn reduces power consumption.

Controlling forward movement by varying the crank-shaft rotation speed guarantees a near-perfect plug flow of product through the dryer, with residence time very tightly controlled to ensure highly consistent product quality.

Pneumatic suspension isolates support structures from dynamic forces and the low-speed shaking action eliminates the fatigue and cracking problems often associated with vibratory equipment.

The dryer/cooler was supplied complete with the air supply/fuel/burner system, the exhaust air system including dust extraction, control software and instrumentation, platforms, ladders and stairways, and erection and start-up services.

With a 10m2 perforated bed dryer area and 8m2 cooling area, the machine is designed to process up to 110 tonnes per hour of minus 3.5mm dolomite normally of about 7% moisture content and to deliver a product below 3% moisture and a temperature not greater than 35C.

Fines are removed during the drying process, which are collected by the filtration system and conditioned with water for disposal in paste form, to eliminate a potential problem with dust.

Exhaust air temperature is kept at 5% above dew point to avoid condensation and consequent blockage problems.

The quarry near Doncaster produces finely-ground dolomite sand mainly used as a flux in window glass manufacturing, which demands consistency in quality and iron content, so that carefully controlled blending is critical in the production process.

The new plant delivers some 3500 tonnes of 2mm and 3mm finished product per week.

Ventilex dryer/coolers available from Orthos in the UK and Ireland bring benefits to the processing of various minerals, notably including sands for the dry silo mortar sector.

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