Saving money with the Ventilex Fluid Bed Sand Dryer

The first step in the processing of sand, gravel and aggregates after mining is a washing and classification process. The material may be screened and stored but at some point moisture content needs to be reduced to meet a specification required for sale or further processing. Operating a sand dryer to dry your mineral product is frequently the greatest operating expense in your process and therefore with proper planning can be your greatest cost-saving opportunity.

Commonly used drying technologies in industry today for minerals and aggregates:

Rotary drum dryers

Rotary drum dryers are large rotating drums where the material cascades through a steam of hot air. Rotary dryers are often presented to have a “low initial cost advantage” but may require additional equipment and manpower to operate successfully. The main disadvantages are high operating costs due to unnecessary fuel consumption, elevated maintenance costs and additional manpower to operate. Rotary dryer systems often include basic controls that require frequent monitoring by an operator to regulate for changing conditions.

Static fluid bed dryers

Static fluid bed dryers utilize large volumes of heated air to fluidize the product. In practice, these dryers have thicker product layers that require larger blowers to keep the product suspended in the air stream. This process offers improved fuel efficient because the increased product layer retains heat and thermal heat transfer is maximized. This dryer may offer the advantages of low initial cost and simplicity of operation but product flexibility will suffer. Its main disadvantage is that the dryer is designed for and requires a consistent and uniform material size. If oversized, out-of-spec material is introduced into the dryer, it will not exit, but remain inside and will eventually prevent operation. At some point in time, the dryer will have to be shut down and cleaned out. Static fluid bed dryers are most suitable for processes that have little process variation. If the input mix/size varies, use of a static fluid bed dryer is not advisable. Static dryer systems often include basic controls that require frequent monitoring by an operator to regulate for changing conditions.

Vibrating fluid bed dryers

Vibrating fluid bed dryers use a large drive mechanism with the bed mounted on springs like a vibrating conveyor to move product through the dryer. They have the advantage that they can process a wider range of products. The main disadvantage is that the dryer and the product is subjected to significant g-forces. These high forces typically cause friable product to break apart creating unnecessary and often unwanted fines and waste. In addition, the high g-forces will be transferred to the surrounding structures resulting in additional installation requirements, premature equipment wear, premature instrument wear and elevated noise concerns. case the bed case to fracture and the drive mechanisms are subject to periodic refurbishment. Instrumentation takes a beating too, so the control systems are typically very basic. Vibratory dryer systems often include improved controls that require less monitoring by an operator to regulate for changing conditions.

Shaking fluid bed dryers

Shaking fluid bed dryers solve the high g-force issue by eliminating the need for vibration and includes a more advanced control systems that eliminates the need for continuous operator involvement. Product is moved through the dryer by a gentle shaking motion, Low Frequency / High Amplitude, that moves it forward in a step by step, uniform manner referred to as plug flow. The g-force issue is eliminated allowing for smallest possible product deterioration, reduced foundation requirements and minimal noise output. A shaking fluid bed dryer system typically has a greater initial cost but the lowest life cycle cost due to substantial savings in fuel consumption and maintenance costs.