Paste Thickening Makes Inroads in Coal Industry
Several new paste thickening projects are in progress in the United States and are drawing attention to new applications for this useful technology. Two of these projects are in the coal industry in Virginia and West Virginia and are the first of their kind in the world.
With coal prices up, the coal industry is investing in improving their plants and operating efficiency. Beard Technologies of Pittsburgh, PA has developed a proprietary flow sheet to reclaim fine coal values from existing retention ponds, thicken the remaining solids along with refuse from the prep plant and redeposit this as paste in the pond. As paste is deposited at the back of the pond, it displaces the water and fines forward in the pond so they can be processed. Beard Technologies is implementing this technology at the Pinnacle Coal plant in West Virginia. Beard selected WesTech Engineering of Salt Lake City, Utah with the assistance of Learco Equipment Co. of Pittsburgh, Pennsylvania to supply the 18-meter diameter x 13-meter sidewall Deep Bed™ Paste Thickener needed for their project. The scope of supply for this project included the paste thickener mechanism, drive, elevated steel tank and instrumentation for controlling thickener operation. The thickener has been erected and is expected to start-up in November 2006.
A second coal project is the Arch Coal, Lone Mountain Plant in Virginia and is supplied by the same collaboration of Learco Equipment Co, WesTech Engineering and Paste Thick Associates. This plant had earlier experienced a release of refuse from their impoundment pond into a nearby creek. This mishap resulted in the plant changing operations from a slurry discharge into a pond to a paste process, produced by belt presses. However, The Lone Mountain plant was dissatisfied with the operating and maintenance expense associated with their belt presses. A plant expansion brought the issue to a head and they decided to look for alternate ways of making paste. This resulted in an order for a 15-meter diameter x 14-meter sidewall paste thickener. WesTech is supplying the paste thickener mechanism, drive, tank, tank erection, instruments & controls and PLC. This package is currently being fabricated and is expected to start up in January or February. The paste thickener is expected to produce about the same solids concentration underflow as was achieved with belt presses while using considerably less polymer.
These are the first two paste thickeners in the coal industry anywhere in the world. The industry is watching these projects closely and they will become subjects for several papers to professional societies as they demonstrate the advantages of this technology over current practices. These advantages include improved water recovery, lower polymer consumption, lower maintenance costs, less chance of accidental discharges from the impoundment, increased capacity for existing impoundments, faster and less expensive reclamation of the impoundment at the end of its utility life. Advantages are both in cost savings for the mine and improved environmental stewardship at the same time.