Dust Collector Screw Conveyors to Convey Lime Kiln Dust Graymont in Superior, WI

General Description

Graymont is a global leader and one of the largest suppliers of lime and limestone products to markets in North American and Asia-Pacific. The Graymont plant in Superior, WI serves the midwestern US and central Canada. Three types of limestone are calcined at the Superior plant to produce high-calcium quicklime, high-calcium hydrated lime, and dolomitic quicklime.

Through the thermal decomposition process in a rotary kiln, limestone produces quicklime and carbon dioxide with dust, known as Lime Kiln Dust (LKD). Most often LKD is sent to landfills as it offers little beneficial use. Alternatively, the chemical makeup of LKD quicklime and inert materials is suitable for drying and modifying certain types of soils and for industrial waste stabilization. LKD is commonly stored in silos until it can be hauled away by truck or rail.

Graymont contracted The Jamar Company to oversee the procurement and installation of four new KWS screw conveyors located below dust collectors. The new screw conveyors bolted directly to dust collector hopper discharge flanges and collected fine dust particulate as it is removed from the air stream. LKD is collected and conveyed to collection hoppers for storage.

Design Parameters

1. Product Type: Lime Kiln Dust (LKD)
2. Material Density: 55 to 90 Lbs. per Cubic Foot
3. Conveyor System Capacity: 200 Cubic feet per Hour
4. Product Temperature: Up to 1,000-Degrees F
5. Duty: Continuous

KWS Advantages

The KWS engineering and sales teams transformed site photographs, hand sketches and minimal process information into replacement screw conveyors that fit perfectly into the existing system. The new screw conveyors needed to fit existing hoppers and match existing bolt patterns. KWS provided 3D parametric models with exact dimensions and verified the dimensions before building the new screw conveyors. The conveyor fitment and installation were flawless in the field.

Special Features

The new KWS screw conveyors were designed for the abrasive environment and temperatures up to 1,000-degrees F. The robust trough design allowed each conveyor to be supported by the hopper discharge flange without the need for additional reinforcements.

Each screw conveyor was approximately 40-feet in length and required intermediate hanger bearings to support multiple screw sections. KWS utilized Style 326 thermal expansion hanger bearing assemblies to account for elevated temperatures. Because the hanger bearings would otherwise be inaccessible for maintenance, KWS incorporated hanger bearing access ports on each side of the bearing to promote rapid replacement.

Each new KWS screw conveyor was designed with a special open-end discharge fitted with a hinged and weighted door that allowed the LKD to discharge directly into storage bins. The weighted doors keep the conveyors sealed when out of service and open as the material discharges, keeping “back pressure” on the system. The screw conveyor drive has an adjustable packing seal to prevent leakage of the fine dust at the shaft penetration.