Conveyors, Transfers, Chutes, Equipment & Technology, Mining and Heavy Industries

Arched plate conveyors replace 16 coal feeders at German plant

Aumund arched plate conveyors replace coal feeders at RWE power plant in Germany (photo Aumund).

Bulk handling specialist Aumund says it helped the performance of utility giant RWE’s Neurath power plant by replacing 16 coal feeders with arched plate conveyors ranging in length from 12 to 32 metres.

At the coal fired power plant, the first power plant block unit was put into operation in 1972. By 1976 three 300-megawatt-block units and two 600-megawatt-block units were in operation.

The power plant uses lignite from the open pit mines at Garzweiler and Hambach (both in Germany) to produce base load power. With more than 4,200 megawatts, the seven block units cover more than ten percent of the installed output of giant German power utility, RWE Power AG.

According to Aumund, coal feeders for the coal mills of the block units F and G were delivered by one of its competitors in 2012 but did not work satisfactorily and caused high costs for downtime and maintenance. The two boilers are each 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.

In 2012 – two years after the initial start of operation – Aumund engineers conducted an inspection together with the customer. In doing so they notice 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. In addition, they displayed substantial mechanical defects and did not fulfil the customer’s demands concerning pressure tightness.

During a rotational downtime of the plant, the existing conveyors were retrofitted by Aumund specialists, in part as 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 tons per hour. During peak times, the conveyors can transport 200 tons per hour 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 says it decided upon welded pan conveyors, which had to be adapted individually for the connection to the hopper.

According to Aumund’s publicity: “The Aumund conveyors, with a standard width of 200 to 300 millimetres, 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 air leaks.

“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. A smaller sprocket wheel was used.

“While equipping the pan conveyors, design engineers selected the Aumund chain AU6052. With a significantly higher safety than normally chosen for comparable uses, 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.”

Aumund Group is active worldwide as a conveying and storage specialist. Its units include Schade and Samson.

Contact: www.aumund.com

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