Mobile Coke Handling System – MCHS

For the production of steel in Electric Arc Furnaces (EAF) graphitized electrodes are required.

To produce these graphitized electrodes, a number of steps are required; among which baking electrodes in a ring pit furnace (so-called 1^st bake).

Basis for this technical description is Ukrgrafit specification “Technical Requirements for the design and manufacturing of a complete mobile pneumatic unit for handling of the packing material in baking furnaces for carbon products”.

The mobile coke handling station (MCHS) is designed to extract packing coke from the electrode furnace pits and to discharge it into a removable hopper. The conveying air flow is generated by a building-mounted stationary suction system consisting of a central duct between the furnace sections, a cyclone, a fine dust filter and a blower/exhauster. Note: a cooler is not considered.

The MCHS consists of a base frame with central joint and piping connected to the building-mounted central duct, and a rotating platform with fixed boom, supporting the vertical telescopic pipe, ball joint, reversal head, horizontal telescopic pipe on a carriage and pipe-to-hopper connection, a removable hopper, a hopper-to-pipe connection and piping to the central joint between the rotating platform and base frame.

To empty a section of pits, the MCHS  is positioned on a neighboring or opposite open section. Packing coke is then extracted via a vertical, telescopic pipe which can be raised and lowered by 2 electric chain hoists. A ball joint enables the vertical telescopic pipe to swivel (somewhat; to reduce the chance of damage). The reversal head diverts the conveying air stream into the horizontal telescopic pipe. The end of the horizontal telescopic pipe is mounted on a carriage and can be moved by an electric (rack and pinion)  gear. The carriage carries the end of the horizontal telescopic pipe, reversal head, ball joint and vertical telescopic pipe, and supports the horizontal pipe in the middle.

The pipe to hopper connection on the one end and the hopper to pipe connection on the other hand is based on gravity with the hopper resting on both pipe ends.

The extracted packing coke is discharged into the removable hopper. The hopper will be provided with a maximum level sensor, which will activate an acoustic and optic signal when activated. After the hopper, the dust laden, conveying air, is directed to the side of the base frame via a joint in the center of the rotating platform and base frame (the central joint). The side of the base frame is then connected to one of the central duct connections, so that the dust laden air can be conveyed to the filter. The base frame-to-central duct pipe consists of a pipe and sliding sleeve joint with expansion bellows and hand lever at the central duct end.

The rotating platform rotates on a  rotary bearing with standard mounted gear. With the platform rotation and horizontal telescopic pipe, the suction nozzle can be positioned at any position within the section. The platform rotation is limited to approx. +- 135 degrees, enough to reach all corners of the neighboring or opposite section to be emptied.

Before relocating the MCHS, an empty hopper shall be placed and the rotating platform shall be secured by a locking device, while at the same time preventing the operation of the suction pipe chain hoists, horizontal pipe carriage gear and rotary bearing gear. When prepared for lifting, the MCHS is lifted by the building mounted crane hook with a dedicated lifting ring.

When the removable hopper is full, it is lifted from the station for emptying into pits of another section. The slide gate valve at the bottom of the hopper is operated via radio remote control. The slide gate valve is connected to the rechargeable battery on the hopper. When installed, the battery charger is connected to the main supply on the base frame via an electric panel on the rotating frame.

Guides on the rotating platform ascertain the proper positioning of the removable hopper when lowered onto it.

The MCHS is controlled by a wireless remote control.

The building-mounted stationary suction system consists of a cyclone, a fine dust filter with pneumatic pulsair cleaning mechanism, and fluidization base and slide gate valve to empty into big bags, a blower/exhauster mounted in a soundproof enclosure with cooling fan, and interconnecting piping. The blower generates the conveying air stream required to suck and transport the packing coke. It is driven by an electric motor via V-belts. The soundproof enclosure reduces the noise from the blower core, whereas the resonance silencer and the absorption silencer(s) reduce air and exhaust noise. The pressostat in front of the blower opens a butterfly valve and if necessary switches off the blower automatically when the vacuum exceeds 0,35 bar. If the vacuum still exceeds the given value, then a spring-loaded safety valve opens. The thermostat in front of the blower switches off the blower automatically when the temperature at the inlet of the blower exceeds 90°C.

The separated dust is collected in the filter bin until its full as detected by the filter bin full level sensor, after which it can be discharged (into big bags) via the electric-operated  rotary valve. As the dust in the filter may become too compact it may not flow while discharging. The filter is therefore provided with a fluidization base, which is pressurized when the rotary valve is activated.

The building-mounted stationary suction system is electrically controlled by a switch cabinet.

The mobile coke handling station is connected to the building-mounted stationary suction system at each section via the central duct with 8 inlets in the middle of the furnace.