Engineered Sands Production
Experience with Dry Engineered Sand
A New Direction
During a market lull, with decreased demand for an asphalt sand, the intensity of this investigation was somewhat abated as Luck Stone turned to other pressing issues. During this time they began a serious study of the in-process screening’s moisture content. The study was conducted over a six month period and found an average moisture level of 1.5 %.This was due primarily to water added at the crusher for dust control.
Also noteworthy during this period was the installation of dust collectors on the circuit, minimizing the need for water addition at the crushers. These results encouraged Mr. Stansell to investigate a type of air classifier he had installed some 20 years prior. He had not seriously considered this air classifier since his previous experience had shown it to wear rapidly, even in limestone. Other concerns were sensitivity to feed moisture, similar to other fine separation equipment.
Continuing his investigation, Mr. Stansell discovered that the company responsible for this particular classifier – the gravitational inertial classifier – was actively marketing this process for dry engineered sands. He also discovered that they had overcome his concern with wear by the utilization of ceramic liners.
Static Classifier Solutions
The technology that Luck Stone investigated has recently been purchased by Metso. It is one of three separate static (no moving parts) classifier types offered dependant on the separation required by the process.
Gravitational classifiers produce 0.15 to 1.65 mm (12/100 mesh) separations and are suitable for coarse industrial mineral solutions. Centrifugal classifiers produce 0.02 to 0.15 mm (100/600 mesh) separations and are suitable for industrial mineral, mining, fly ash and cement applications. These classifiers exploit centrifugal forces to produce very fine separations.
Gravitational inertial classifiers produce 0.063 to 0.3 mm (50/23 mesh) separations and are highly suitable for precise engineered sand applications. Adjustable airflow controls the amount of ultrafines retained as product and recirculating air scrubs the coarse product before it exits.
The gravitational inertial classifier’s main applications are in the production of quality engineered sands from quarried rock. The classifier utilizes air flow, gravity, and directional changes to achieve very accurate and adjustable material separations.
The ultrafine retention is controlled by the adjustment of the primary to secondary air ratio. Tailoring the amount of ultrafines in the product offers quality sand production with minimum waste.
Static Yet Accurate
The gravitational inertial classifier offers a versatile option that can fit into multiple quarrying solutions. It is highly accurate and adjustable and has the ability to remove just the ultrafines that need to be removed, which maximizes both productivity and sand quality.
These classifiers also have exceptionally low operating costs as they have no moving parts and ceramic lining throughout. This means that no adjustment for wear is required and abrasive feeds have little influence on operating costs with ceramic liners lasting for years, even in highly abrasive applications.
The intelligent design of the classifier also effectively utilizes the air movement which in turn minimizes the power requirement.