How to purify the dust air in cement plants?
The air pollutant from cement production mainly are dust and flue gas.
The dust mainly comes from the following procedures:
1.the raw materials preparation
C.Coal grinding and feeding.
D.Raw meals grinding.
2.Clinker burning system will exhaust much dust air.
3.The finish production processing:
A.The cement mills
B.The cement packing
C.The bulk cement transportation.
For the raw material preparation A, C, D and the finish production process the dust air comes with the lower temperature, but the raw material preparation B, dust air exhausting from head and tail of the kiln always with the higher temperature.
The particles content in dust air mainly are CaCO3，CaO，SiO2，Fe2O3，Al2O3，MgO，Na2O，K2O, etc.
For the flue gas from the cement production mainly are SO2, NOx, CO2, HF, and so on which is comes from the decompose of CaCO3 and the fuel burning.
SO2 is comes from the raw meals (black or half black raw meal powder for vertical kiln), fuel burning;
NOx which is comes from the reaction between the N2 and Oxygen in high temperature;
HF is comes from the fluorine composition decompose from the raw meal when incineration process, such as mix with fluorite as the mineralizer in vertical kiln.
CO2 mainly comes from the decomposition of CaCO3, the fuel burning, etc.
1.For the dust air control
Zonel filtech can offer the filter bag dust collector to purify the air, also can offer the relevant accessories according to the clients’ requirements.
The bag filters from Zonel filtech with the high filter efficiency, even for the 0.5 micron particles, the filter efficiency can up to 99.99%, and the filters always with stable performance, very easy to maintenance.
Zonel brand bag filter house can collect the dusts which can’t be caught by the cottrell, such as the dust with very good or very bad conductivity.
2.For the flue gas control
CO2: improve the quality of clinker; reduce the clinker consumption, such as develop some mixing materials on the basis of the same properties of cement, use some green cement replacement to reduce the cement consumption; develop the better systems to use the waste heat, such as use the waste heat to dry the raw materials, use the waste heat to generate electricity, etc.
Change the better raw material, reduce the Sulphur content;
Absorbed at raw mills: lead the dust air from the tail of the kiln to raw mills, the reaction as following:
CaCO3 + SO2 = CaSO3 + CO2
2 CaCO3 + 2 SO2 + O2 = 2 CaSo4 + 2 CO2
Mix some Ca(OH)2;
Equip the shower tower;
And the most effective solution is choose a suitable Sulphur and alkali proportion;
At the same time, at the tail of the kiln, equip the filter bags dust collector, the Na2O，K2O at the surface of the dust filter bags will reaction with the SO2 and NO2, the content of the acid air can reduce 30~60%.
Keep a suitable temperature, control the volume of the air;
Use the reducing gas, such as CO, H2, etc, mix some Fe2O3, Al2O3 at the raw meals, which can reduce the NOx to N2.
2NO + 2CO = N2 + CO2;
2NO + 2H2 = N2 + 2H2O
2NO2 + 4CO = N2 + 4 CO2
2NO2 + 4H2 = N2 + 4H2O
According the action, so at the kiln have to control the O2 content carefully.
Selective catalytic reduction also can help to reduce the NOx exhausting, this solution is insert some selective reducer, such as hydrogen nitride or Urea:
8NH3 + 6NO2 -> 7N2 + 12H2O
6NO + 4NH3 -> 5N2 + 6H2O
4NH3 + 3O2 -> 2N2 + 6H2O