Limestone and FGD gypsum transport at a coal-fired power station in England
Transportation of limestone
At the Rugeley coal-fired power station in Staffordshire, England, the two existing coal-fired boilers 6 and 7 of 500 MW each were equipped with a flue gas cleaning plant. Plant and materials engineering firm Arthur Loibl GmbH supplied and installed the materials handling equipment for receiving limestone and the transportation of Flue Gas Desulfurization (FGD) gypsum. The required limestone, with a grain size of 20mm, is delivered by wagons and discharged into a hopper in an enclosed unloading station. For dust suppression and dust removal in the unloading area a de-dusting plant with a de-dusting air volume of approx. 60,000 Nm³/h is applied, with feeding of the cleaned dust to the adjacent materials handling equipment by means of screw conveyor. A supply of compressed air is provided by means of screw compressors. The reinforced concrete hopper is covered with an open grid of 110mm spacing, and lined with wear rubber plates 27+3mm to minimize wear.
Underneath the hopper in the basement area, discharging is made via two unbalanced vibratory conveyors, each with a width of 1,500mm, which in turn feed a vibratory cross-conveyor. The total discharge capacity is 600 tons/h = approx. 480m³/h max.
Sorting and refining conveyed material
For removing metallic parts an electric overbelt magnet is installed above the discharge of the vibratory cross-conveyor onto the adjacent troughing belt conveyor, which discharges the ferrous parts into a container.
In order to measure mass flow the conveyor belt, which has a belt width of 1,000mm and a conveying capacity of 600 tons/h, is equipped with weighing scale. On the discharge side, a hammer sampling station is integrated into the hood for quality inspection of the delivered limestone. Limestone is discharged on to a sidewall belt conveyor, which has a belt width of 1,400mm and a center distance of approx. 34,000mm, for the following transfer to a customer-supplied pipe conveyor.
Cleaning scrapers were applied underneath the horizontal sections of the sidewall belt conveyor. These scrapers collect the spillage and return it into the conveyed flow. After the customer-supplied pipe conveyor, the two limestone silos are fed via a reversible troughing belt conveyor with a belt width of 1,000mm, center distance of approx. 19,000mm and a conveying capacity of 600 tons/h.
Transportation of FGD gypsum
Inside the dewatering station the FGD gypsum is transported via a reversible belt conveyor, belt width 650mm, for both the main and auxiliary routes. Outside of the dewatering station, an enclosed, curve-negotiable Sicon® conveyor (S100/650 x 80,000mm) transports the FGD gypsum to the gypsum silo, with a conveying capacity of 25.0 tons/h.
The Sicon® conveyor begins on a platform +11.50m outside the dewatering building and runs around a limestone silo, ascending at about 17° and 12°, with concave and convex curves as well as two horizontal deflections. For this purpose the conveyor belt frame is designed as a self-supporting structure and is fastened to the limestone silo.
