A bag filter is made up of some main parts such as filter housing, inlet part, bags mounted on a hollow plate, filter media cleaning equipment and scraper bottom.

The fan is placed after the filter to achieve negative pressure in the filter. The dust air is fed into the filter and spread to the entire filter area. Some pre-separation of large particles occurs when the dust air is supplied. The dust-laden air passes through the filter bag (see filter bag tab) so that the separated dust adheres to the outside of the bag. The cleaned air flows out. The air flows through the opening in the top end of the filter bag and is discharged by the fan.

The cleaning system handles flushing air from the compressed air reservoir on the filter. The electronic unit activates each valve so that compressed air from the container is pushed through valves to the nozzle tube and on to the filter bag. The compressed and secondary air continues into the filter bag, interrupting normal filtration and causing the dust cake on the outside of the filter bag to crack, loosen and fall. The valve closes and the filter media returns to the filtration phase.

The cleaning intervals are adjustable to adapt to different dust types and concentrations. The scraper base is made of a strong plate with an outlet, a geared motor and an agitator with scraper blades that loosen the dust and direct it to the outlet of the filter. The scraper base is designed for mounting the auger. If there is a fault situation that causes e.g. too high flue gas temperature, the by-pass dampers can direct the flue gas around the bag filter. This function is controlled by three flue gas dampers. The control system is designed so that the flue gas is by-passed when the following fault situations are met.

– Flue gas temp. after the convection part is above Max. flue gas temp.

– Errors have been detected in the filter.

– Faults have been detected on flue gas dampers.

– There is a lack of compressed air for flushing air.

– The pressure drop is too high.


Setpoints are set in SCADA.