Process Bag Filters
Process Bag Filters are the Redecam’s core product and are used throughout various industrial sectors on a wide range of applications.
Technology still makes a difference in terms of bag filters efficiency and performance, particularly where large size units are required to perform under heavy-duty operation.
Although the big process bag houses show many different configurations, they belong to two classes only, characterized by the gas approach to the bags:
Mark DPM, in which the gas approach to bags is side-ward
Mark DPD in which the approach is up-ward

Bag Filter DPD Model
DPD bag filters are suited for medium inlet dust burden applications (up to 200 g/Nm3) such as those on 3-fan kiln circuits, clinker coolers or integrated systems equipped with one single filter to dedust kiln and cooler.
The DPD arrangement consists in compartments placed in pairs on either side of a central duct. The central duct contains both the inlet (dirty) gas and the outlet (clean) gas ducts.
The inlet duct diminishes from full height to nil as it extends from the inlet to outlet end of the bag filter. The outlet duct increases from nil to full height as it progresses from the inlet to outlet end of the bag filter.
For the respective ducts the gas velocity is constant along the length of the duct.
The baffles (pipes and perforated plates) convey the gas flow to ensure each progressive pair of compartments receives an equal volume of gas for treatment.
The gas enters the hopper through a distribution grid ensuring even distribution along the bag filter centreline to successive bag filter compartments. The gas passes into the hoppers through the isolation dampers.
The gas enters each hopper and is deflected by a set of perforated plates of suitable permeability and orientation in order to obtain a uniform gas velocity across the hopper width.

Bag Filter DPM Model
DPM bag filters are suited for heavy-duty service and for high inlet dust burden gases (up to 1000 g/Nm3) like in the 2-fan kiln systems or cement mill and separators.

In those cases there is a need for efficient dust pre-separation to reduce the dust burden reaching the bags. The wide central hopper is used to decrease the axial gas velocity so that a dust pre-dropping action takes place.
Suitable baffles between the gas inlet and the central hopper ensure a uniform gas flow and velocity across the hopper cross-section.

The central hopper feeds on its side vertical channels where the gas rises and then enters each bag chamber through a vertical slots screen. Baffle arrangements distribute the gas uniformly along the channels and consequently through the slots of the screen. The distribution channels also act as dropout chambers.

While the air to cloth value is of utmost importance DPM bag filter models, the can velocity has no impact in filter design since the gas flow to bags is horizontal. Access is made on one side of the bags in order to avoid the gas rising from counter-flowing with the dropping dust. The slot location between the bag rows prevents contact between the high dust burden gases and the cloth, improving bag life and reducing pressure drop.

Mechanical Design
Continuous laboratory tests and on site work experience inspired Redecam to develop the bag fixation SSP (Simple Pressure System) that is today the most advanced, user-friendly and efficient system available.
Because custom welded construction is standard for all Redecam’s filters, the tightness of the casing between the dusty and clean side is 100% effective.
To prevent dust leakage at the weak points, Redecam created a configuration whereby the dust seal is enhanced by:
- increasing the contact surface area of the bag against the tube-sheet. The bag hole in the tube-sheet is drawn and is not limited to a pure drilling of the steel plate. The contact surface between the two surfaces is not then limited to the pure thickness (typically 4 mm) of the plate; it is extended to the whole internal surface of the drawn hole (around 18 mm)
- increasing the pressure that the bag collar imprints on the bag's cloth against the drawn edge of the tube-sheet hole. The special shape of the collar also takes advantage of the temperature effect: the tube-sheet is carbon steel and the collar is aluminium, resulting in extra pressure being generated on the sealing surface.
In addition the bag fastening system is very simple and allows rapid installation/removal of each bag. It also avoids any risk of bags falling during installation or maintenance: the steel solid ring embedded in the top edge of the bag prevents any bag from dropping into the hopper.

Bag cleaning system
Redecam Bi-Jet system combines the use of a double Venturi arrangement; one is located on the air tube immediately downstream of the nozzle, and the other one above the bag inlet.
This system enhances the volume of air/gas that is entrained from the surrounding ambient to the bag inlet by the compressed air flow. The surrounding air/gas is entrained by the friction with the compressed air flow.
The quantity of air/gas is proportional to the friction, while the friction is proportional to the velocity of the compressed air.
A reduced consumption of compressed air is therefore achieved as more surrounding fluid is entrained.
The double Venturi system also minimizes the dispersion of compressed air during the injection phase; it reduces the quantity of air needed to pulse the bag and it achieves a flow velocity higher than in other systems equipped with one Venturi. The higher the velocity, the greater the quantity of entrained surrounding air.