Sand and Aggregate Dryers/Coolers
Carrier vibrating fluid beds have been used for decades in the aggregate industry because of their reliability and low operating costs. The dramatic rise in fuel costs in recent years has made fluid bed technology far less costly to operate than rotary dryers. To meet the increasingly demanding requirements of today’s aggregate producers, Carrier has developed a line of fluid bed processors designed specifically for the aggregate industry.
The new sand and aggregate dryer operates at just one “G” of vibrational force. This is the minimum required to ensure a dry, uniform product at the discharge, and energy-efficient fluidization. The drive mechanism allows full adjustment of important parameters, such as amplitude, frequency, and angle of vibration. The entire machine is dynamically isolated to reduce the reaction to the supporting foundation. Insulation is attached with a steel skin and hot air is supplied to the machine through a flexible metal “bellow” in lieu of fabric flexible connectors. The result is the most reliable fluid bed available today.
The following variations in system design are available, each offering varying degrees of energy savings and capital cost.
- Dryer only – A single, high-temperature fluid bed that typically uses 30-40% less fuel than a rotary dryer.
- Dryer/Cooler with Recirculation – Warm exhaust air from the cooling section is recirculated to the drying zone air heater, providing an additional energy savings of 10-15% and reducing the amount of air exhausted to atmosphere by up to 50%.
- Dryer/Cooler with Multi-Point Predictive Controls – A PLC-based control system is used to precisely control the condition of the product as it moves from the drying zone to the cooling zone, allowing the system to take advantage of the evaporative cooling effect that occurs when warm, slightly-moist sand is exposed to cooling air. This system prevents the discharge of hot or wet sand during upset conditions and further improves the energy efficiency by approximately 10%.