Semi portal scraper reclaimer for RWE Westfalen and RWE Eemshaven
Until the end of 2009, SCHADE Lagertechnik GmbH which is based in Herne and forms part of the AUMUND Group will have delivered one semi portal scraper reclaimer (26.3 m gauge) with a conveying capacity of 200–400 t/h to RWE Westfalen in Hamm, Germany. The trial run start is scheduled for May 2011. At present, a hard coal-fired dual block system with an installed power of 2x800 megawatt is being erected in Hamm. The completion is scheduled for 2011.
A further order was received at SCHADE Lagertechnik GmbH in July 2009 from RWE Eemshaven in the Netherlands. The machine planned to be used at this location from 2011 is practically a twin of the scraper reclaimer that will be delivered to Hamm. The difference: The machine is designed for a conveying capacity of 50 to 400 t/h.
The envisaged hard coal power station in Eemshaven with its staff of 320 employees will be connected to the grid with a gross power capacity of 1,600 megawatt, producing electric power for about 3.2 million households per year as from 2012/2013.
For years now, SCHADE Lagertechnik GmbH has been one of the worldwide leading manufacturers of equipment for bulk material stockyards and blending beds. As a member of the AUMUND Group with its subsidiaries and branch offices all over the world, SCHADE successfully utilizes the benefits of the global network.
Already in 1978 the SCHADE engineers designed and built a portal scraper reclaimer for an open cast coal mine in South Africa with a span of 50.5 m for reclaiming 2,125 t/h of coal which at that time represented the worldwide largest portal scraper reclaimer ever built. Shortly afterwards a portal scraper reclaimer for reclaiming 1,000 t/h of limestone was supplied to a cement plant in the USA, followed by another portal scraper reclaimer with a span of 50 m for a cement plant in Canada.
As a standard, the SCHADE portal scraper reclaimers for large spans, whether for indoor or outdoor operation, are equipped with a boom guide. This allows the scraper reclaimers to withstand horizontal forces and to avoid unstable movements of the free end of the scraper boom. The boom guide was first introduced and patented by SCHADE. The portal structure, as a further standard feature is designed and built as a welded box girder.
Automatic reclaiming of the stockpile
In the meantime, semi portal scraper reclaimers and portal scraper reclaimers from Herne have gained an excellent reputation on the coal stockyards in the power station industry. A semi portal reclaimer which travels back and forth along the pile in longitudinal direction spans the stockpiled bulk material. The scraper chain with its blades removes the bulk material layerwise from the side slope, feeding it onto a belt conveyor via a concrete ramp. This belt conveyor is located beside the stockpile in longitudinal direction.
At the end of the stockpile, the scraper boom is lowered by an amount equivalent to the cutting depth. Then the machine starts to travel to the opposite end of the stockpile where it will lower the boom again by the amount of one cutting depth and change its travel direction. This process is repeated continuously until the stockpile is completely reclaimed.
The reclaiming of the stockpile is an automatic process, whereas normally, the initial cutting and the levelling of the stockpile is carried out manually by the operators. The semi portal scraper reclaimer fully reclaims the stockpile in a layerwise process, the bulk material is removed by the blades of the scraper chain and fed to the funnel-shaped feeding chute. During the reclaiming operation, scraper chain and travel drive are running continuously, and the angle of repose of the stockpile and at the stockyard front walls is monitored automatically. This monitoring of the front walls allows the semi portal scraper reclaimer to travel close to the front wall, up to a preset minimum safety distance. The simultaneous monitoring of the angle of repose of the stockpile prevents the caving in of the stockpile side face.
Variable conveying capacity between 200 and 400 t/h
The portal scraper reclaimer for the power station Westfalen in Hamm will transport FGD gypsum with a bulk density of 0.9 to 1.3 t/m³ and a particle size of 0 to 10 mm. The stockpile length is about 90 m, the stockpile height can reach up to 12 m at the front walls and 10 m at the other sides. The conveying capacity can vary from 200 to 400 t/h, depending on the change of the scraper cutting depth and the travel speed (about 2.86 m/min. on average).
The scraper reclaimer travels on four wheels, with two of them fitted with a drive. The axle loads are supported by roller bearings which are sealed by rotary shaft seals. A drive unit supported by a torque support is mounted on each drive shaft. Thus, the travel drive is not susceptible at all to any later distorsions which among other things an unwanted settling of the rail might cause. The scraper boom is a weldment and equipped with exchangeable chain guideways. The boom suspension consists of a pivotably connected yoke with rope pulleys fitted with roller bearings.
Chain in special SCHADE design
The heavy special scraper chain (bush chain) comes in link chain design; thanks to hardened bolts and bushes, its wear is kept at a low level. Each chain link of the scraper chain is additionally equipped with roller bearings and outboard rolls which travel in the chain guide. The rolls are provided with roller bearings and special seals. The scraper chain in the special SCHADE design has proven its worth for many years now in practical use with abrasive bulk materials and excels in particular in applications where chain lubrication is not acceptable. Under the aspect of low maintenance requirements and low operating cost, the chain is fitted with an automatic tensioning device that ensures the uniform tensioning of both chain strands.
The drive shaft of the scraper chain is accommodated in robust, sealed roller bearings and carries two welded chain wheels with exchangeable toothed rims made from special steel.