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A filter plant at the Scunthorpe Corus steelworks is using Brevini hybrid design gearboxes, which combine planetary and helical gears, to open and close doors on the iron desulphurisation process.

The installation is being used to capture the fumes created during the desulphurisation process and has been built in order to improve the plant’s environmental performance.

The door drives needed to be compact yet able to provide high torque output and low energy input, combined with strength and durability.

Brevini supplied four Posiplan gearboxes for the filter plant project, each of which have a reduction ratio 2813.5:1 and are fitted with a tiny 1.5 kW motor.

This provides a huge output torque of 22,000Nm and a low speed of 0.5rev/min.

The gearboxes are shaft mounted, which means they are tougher than exposed transmission alternatives such as belts, chains and pulleys.

Brevini said this is ideal for applications that require 90-deg operation or survival in harsh environments.

The gearboxes use the latest labyrinth sealing technology and high-performance bearings, extending operating life in the toughest environments.

As well as reducing dust emissions, the technology aimed to create a more pleasant working environment for employees and speed up the steelmaking process.

Previously, the plant used two wet scrubber systems to remove the fumes generated by the iron preparation and desulphurisation processes; however, these were becoming outdated and inefficient.

To replace the two wet scrubber systems, one new bag filter was commissioned.

The desulphurisation process involves co-injecting lime and magnesium into a ladle of molten iron – the sulphur in the iron reacts to this and rises to the surface in the form of a slag.

Once the injection treatment has been completed, the slag is skimmed off the ladle.

The desulphurised iron can then be taken into the BOS vessels to be converted into steel.

It is during the desulphurisation process that the fumes generated must be extracted and cleaned efficiently.

Doors have been designed that close to contain the fumes during the process while the extraction system draws them away.

The gearboxes required to drive the doors needed to be compact in order to fit into the available space while providing the strength and torque needed to close the heavy doors.

Brevini was able to design a solution that met all the application requirements using its Posiplan range of planetary/helical hybrid gearboxes.

The Posiplan hybrid gearboxes are said to combine the efficiency of low-weight, high-reduction ratios of planetary gear stages on the input side with the higher capacity, strength and durability of bevel helical gears on the output; this is ideal for medium to large industrial applications.

The input end employs planetary stages where higher speed and compactness are an advantage, while the output uses a helical stage as it is slower and has higher torque.

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