Plate Conveyors replace Coal Feeders

Coal Feeder

Plate Conveyors replace Coal Feeders

Aumund replace 16 Coal Feeders with Arched Plate Conveyors at RWE Power Plant
With the conversion of 16 arched plate conveyors, Aumund Fördertechnik contributed to the improvement of the operating procedures at the RWE power plant in Neurath, Germany. The conveyors with a length between 12 and 32 metres are used as coal feeders in the block units F and G. During peak times, the conveyors can transport 200 tons per hour since one pan conveyor loads one megawatt.
(ed. WoMaMarcel - 06/10/2015)
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The Aumund conveyors with a standard width of 200 to 300 mm had to be built into the extremely cramped constructive space.

In Grevenbroich-Neurath, the first power plant block unit was put into operation in 1972. Until 1976 three 300-MW-block units and two 600-megawatt-block units were put into operation in total. The power plant uses lignite from the open pit mines at Garzweiler and Hambach (both in Germany) to produce the electricity base load demanded by private households and industry. With more than 4200 MW, the seven block units cover more than ten percent of the installed output by RWE Power AG owned power plants.

In August 2012 after investing EUR 2.6 billion, RWE Power AG put the two additional lignite power block units F and G into operation with a performance of 1100 MW each and improved systems technology BoA.

The coal feeders for the coal mills of the block units F and G delivered by a competitor in 2012 did not work satisfactorily and caused high costs for downtime and maintenance. The two boilers each are fed by eight coal feeders.

Due to the structural situation and the high costs for new machines, Aumund was contracted to improve the existing pan conveyors that were only two years old. The casings of the machines were conserved as far as possible and received additional reinforcements. On the outside sections of the machines gear unit, engine and bearings were re-used. On the inside however, all components including the drive shafts were replaced by Aumund-machine parts of the BPB 250 line. In carrying out the contract, Aumund undertook construction, production and installation supervision. The existing cleaning conveyors were converted from three strand- to two strand conveyors. The drive units remained, but their positions were optimized during the retrofit, while the drive- and tensioning stations were renewed.

Replacement without simultaneous Downtime

In 2012 — two years after the initial start of operation — the Aumund engineers conducted an inspection together with the customer. In doing so they noticed, that the existing pan conveyors based on round link chains of a third-party manufacturer were heavily worn after only a rather short life span. Besides, they displayed substantial mechanical defects and did not fulfill the customer’s demands concerning pressure tightness. During a rotational downtime of the plant, the existing conveyors were retrofitted by Aumund specialists partially while the furnace kept working. Thus, a general overhaul could be executed with the heavily worn conveyors while avoiding a simultaneous boiler downtime, which would have been necessary under the given circumstances in the medium term.

For the retrofit, RWE selected light pan conveyors with an average performance of 150 t/h. During peak times, the conveyors can transport 200 t/h since one pan conveyor loads one megawatt. While designing the new machines within the existing casings, some constructive tricks became necessary to achieve the conveying performance needed. Aumund decided upon welded pan conveyors, which had to be adapted very individually for the connection to the hopper.

Extremely cramped Constructive Space

The Aumund conveyors with a standard width of 200 to 300 mm had to be built into the extremely cramped constructive space. Simultaneously with an adaption and a complete exchange of the former material feed, the conveyors were equipped with a new surface. Due to the limited space available between material feed, side plate and rollers on one side and the outer edge of the casing - pressure tight up to one bar — on the other side, a special construction had to be realized. Because of the negative pressure loading of the coal mills, special attention was given to a better sealing of the entire casing to avoid leak air.

The arising material loads underneath the bunker chutes were brought under control by installing a baffle beam. With an increased board height, the feedback conveyor had to be lowered. Besides, a smaller sprocket wheel was used.

While equipping the pan conveyors, the designing engineers selected the Aumund chain AU6052. With a significantly higher safety than normally chosen for comparable uses, notably higher service life can be achieved. The use of new flights between the chain strands, the lowering of the tensioning axis and the installation of a new sprocket wheel completed the retrofit.

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