Inclined Screw Conveyor for Conveying Wood Ash West Fraser Lumber Mill in Leola, AR

General Description

West Fraser is a diversified wood products company that operates 40 mills across Western Canada and the southern United States. The Company’s main product is lumber produced from spruce, pine, fir and southern yellow pine. West Fraser also produces plywood and medium-density fiberboard. The plant located in Leola, AR is a dimensional lumber mill that produces structural lumber such as two-by-fours and two-by-sixes that are used for commercial and residential construction.

Wood waste in the form of wood chips, shavings and sawdust is a byproduct of the lumber making process. West Fraser utilizes the wood waste to fuel boilers for generation of electricity to power plant operations. After the fuel is burned, wood ash is produced and must be conveyed to a collection area where it is sold as an additive to be used in road construction.

West Fraser had a screw conveyor that was a constant source of problems and excessive maintenance. The conveyor was supplied as part of the original ash handling system. Various components of the screw conveyor were wearing out every 6 to 9 months due to the abrasiveness of the ash being conveyed. Working to understand the needs of the plant, KWS provided a rugged, long-term solution.

Design Parameters

1. Product Type – Wood Ash
2. Material Density – 40 to 50 Lbs. per Cubic Foot
3. Conveyor Capacity – 645 Cubic Feet per Hour
4. Moisture Content – 60 to 70-Percent Solids
5. Duty – 24 Hours per Day, 7 Days per Week

KWS Advantages

An engineer from KWS visited the facility and met with the Boiler Room Superintendent to determine the root cause of the problems and determine a solution. Dimensional information from the existing screw conveyor was taken and documented so a drawing could be produced. Failed components from the existing conveyor were examined and recommendations made to improve the life of the new screw conveyor.

Special Features

The existing screw conveyor was not built to handle the abrasive environment. The new KWS screw conveyor was designed to eliminate all the previous problems. The screw was mounted on extra-heavy pipe with 3/8-inch thick flights. The flights were continuously welded on both sides of the pipe to provide maximum strength. KWS replaced the non-split tubular housing with a U-trough with carbon steel liner. The liner could easily be replaced if there is noticeable wear. Since the ash was being conveyed at an elevated temperature, special bearings, seals and paint were required. An inspection door was added over the discharge for monitoring the conveyor in operation. A port for flushing with water was added at the request of the maintenance department for cleaning out the conveyor when needed.