Barkın MİNEZ
Dr. (Mech. Eng.) / Asel Teknik
According to Darcy law, filtration capacity in dust collection units depends on the following factors;
1) Thickness of dust cake (mm.),
2) Dust (average) particle size (micron),
3) Dust load (gram/m3),
4) The coefficient that depends on the physical properties of gas and dust,
5) Experimental coefficient that depends on the design value of the dust collector,
6) Filter element permeability coefficient,
7) Filtration rate (m3/m2/min).
While dust collection units have been preferred by companies, only the filtration rate has been considered without the first 6 substances in most cases. However, with other parameters, the effects of filtration rate on capacity are mathematically equal.
All of these 7 titles are shown in detail as the following;
1. Powder Cake Thickness
The deposition occurs on the filter bags of the de-dusting unit and as a result, this cake layer enables the filtering of this powder from the rear. The layer of cake naturally creates a resistance and after a certain thickness, it should be shaken and re-cake formation should be initiated. For this process to be good, it is very important that the pulse air should be at sufficient pressure, flow and dryness.
2. Average particle size of dust
This is average particle size of the dust that is coming into the dust collector unit. As the grain size smaller, the resistance of the cake increases, consequently total system pressure drop rises up.
3. Dust load
Dust load can be defined that the amount of solid particles in 1 m3 of polluted air. More and more the dust load, the cake formation time becomes shorter than. In some improper practices, very big amount of dust that creates maximum cake thickness in a very short time is given to the dust filter element. In this way, as a result of the excessive resistance, suction can be performed at a very low flow rate; sometimes even almost no suction can be made.
4. The coefficient that depends on the physical properties of gas and dust
Parameters (as the temperature of sucked gas) are selected coefficients that also depend on the adhesion of dust, moisture. These features can be dramatically reduced the filtration capacity and must be meticulously involved in the calculation.
5. Experimental coefficient that depends on the design value of the dust collector
The “inlet / outlet” velocities of the dust collection unit are the coefficients which are determined by actual tests that depend on issues such as dispersion characteristics within the unit.
6. Filter sieve permeability coefficient
It is the ability value of permeability that depends on the material and fabric of the filter element.
7. Filtration rate
It is the air flow rate that the unit filter bag area should filter in per unit time. If velocity increases, resistance increases.
Considering that the parameters of particle properties of dust and physical properties of dust and gas cannot be changed from these 6 parameters, in order to increase the filtration capacity by decreasing the total filtration resistance;
Either we need enlarge the filtration (bag) area, or reduce the dust load.
CycloJet dedusting systems reduce the dust load of the filter element by creating both cyclone and jet pulse filtration unit on the same construction. Thus the system work with
• Less filter bags,
• Less compressed pulse air,
• Lower fan pressure,
• Less electricity consumption.
In extreme conditions, engineers have reached these goals for many kinds of minerals.