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Bag filters for coal dust extraction

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In our catalog we have included filter units that are by design directly made for use in explosive dust extraction applications. This specific dust is emerging when working with coal. Our catalog includes 18 basic baghouse units for coal dust that forms an explosive atmosphere with air. The bag filter units are graded according to the required volumetric airflow.

Parameters of coal dust

When handling coal, dust particles are released into the air and these can easily form an explosive atmosphere when mixed with air. This dust is very important to extract efficiently, as even the dust sediments in the working environment are undesirable. Explosive dusts are specific by their values of Kst (bar.m/s) and Pmax (bar). The baghouse units included in the catalog are designed for the fine coal dust normally found in enviroments such as power plants or coking plants.

Coal dust extraction

Dedusting of coal unloading pits

In the operation of the coal pits or coal dumps, wagons are unloaded into the underground reservoirs from where the coal is transported to further processing. Upon unloading, coal from the wagon drains off within seconds and dust leaks into the operator area. An efficient dedusting system ensures dust extraction before the dust rises to the operator’s work area. We recommend to place suction fittings in the space between the grates and the wagon operator ramps.  We recommend to extract circa 40 000 m3/h per one unloaded coal wagon.

Coaling space dust extraction

Coaling is the path from the coal dump to the bunkers in the boiler room. Part of the coaling path is an hourglass station, where conveyors of conveyor belts can change the way of conveyed coal and other belt conveyors. Part of the coaling path is an drift station, where different conveyor belts can change the way of conveyed coal to other belt conveyors. At the end of the conveying route, coal is filled into one of the bunkers. Dust extraction is always divided into individual dedusted areas that can dedust one central bunker. The Overp (drift) stations extract dust by a separate central extraction technology and the top over area with bunker filling station also by a separate dedusting system. The dust from the filter device is always returned to the conveyor belt conveyor so as to avoid any losses of coal.  The extraction flow rate for drifts is always set down to at least Q= 2500 – 3500 m3/h and Q= 6000 – 8000 m3/h for bunker dedusting.

Parameters for extraction of explosive coal dust

The design and implementation of extracting explosive dust must adhere to at least these basic rules. The suction line must be properly electrically connected between the components from the suction device to the baghouse unit. The whole system must be properly grounded. The baghouse must be equiped with proper explosion vents directed into a safe location. The filter housing must be pressure resistant, the bag medium must be antistatic. The exhaust duct must be fitted with a non-return backflap valve to prevent baghouse explosion spreading into the suction line, and the suction ducting flow rate must not fall below 20 meters per second.

Parameters of baghouse units for extracting coal dust

Baghouse units in the GIDLY catalog are fabric filter units equipped with automatic regeneration of bags by a reverse pulse jet technology. From our experience of individual extraction applications, the lifetime of the filter media lasts for more than 20,000 hours without the need of any manual refinement. The filter media are flat smooth fabric sleeves made of non-woven fabric with an antistatic coating and an area mass of 600 grams per square meter. The filter medium does not contain folds where the dust be sedimented and is very mechanically resistant to tearing or scraping. The amount of residual dust particles ranges from 0,25 mg/m3 to 1 mg/m3, which allows for cleaned air to be recirculated back into the plant for heating and save costs.  When returning the filtered air, it is necessary to place a residual dust sensor in the exhaust pipe so that the purity of the filtered air can be continuously monitored. If the set dust limit should be exceeded, the system must shut down immediately or switch the exhaust to the outdoor environment without delay. The filtering device must be positioned so that the explosion vents are directed into a safe space.

Recommended ducting solution for coal dust extraction

For aluminum dust extraction applications, we recommend to design the ducting with a combination of straight sections in spirally wound piping (a.k.a. SPIRO) with flanged joints and fittings (tapping, knees, flaps) in Group II welded flanged finish. We recommend this combination because of the extraction of the slightly abrasive dust, which usually abrades the places of  air direction change = branches and knees. We do not recommend using riveted joints so that the inside of the pipeline remains smooth throughout its length. The part of the ducting, ie between the baghouse unit and the backflap valve must be made of a pressure resistant pipe Group II or Group III.

Baghouse units for coal dust extraction in the GIDLY catalog

To find a specific assembly of the baghouse and fan, please go to the catalog and price list page. Select Baghouse units. From the list select „Coal dust extraction – EX“. In the next step, select the required volumetric airflow of the bag filter unit. The result will be a set of items – baghouse unit+ explosion dust design parameters + fan +  silencer box, all of which form a dedusting system. You can then insert the items into the costing.


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