The air pollutants from cement production and the relevant solutions.
The air pollutants from cement production mainly are dust and flue gas.
The dust mainly comes from the following procedures:
1. the raw materials preparation
A.CaCO3 crush.
B.Clay drying
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 a lower temperature, but the raw material preparation B, dust air exhausting from the head and tail of the kiln always with a higher temperature.
The particles content in dust air mainly are CaCO3， CaO， SiO2， Fe2O3， Al2O3， MgO， Na2O， K2O, etc.
For the flue gas from cement production mainly is SO2, NOx, CO2, HF, and so on which come from the decomposition of CaCO3 and the fuel burning.
SO2 comes from the raw meals (black or half black raw meal powder for vertical kiln), fuel burning;
NOx which comes from the reaction between the N2 and Oxygen in high temperatures;
HF comes from the fluorine composition decomposed from the raw meal in the incineration process, such as mixed with fluorite as the mineralizer in the vertical kiln.
CO2 mainly comes from the decomposition of CaCO3, the fuel burning, etc.
Solutions:
1. For the dust air control
Zonel Filtech can offer a filter bag dust collector to purify the air and also can offer the relevant accessories according to the client’s requirements.
The bag filters from Zonel Filtech 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 maintain.
Zonel brand bag filter house can collect dust that can’t be caught by the Cottrell, such as 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 developing some mixing materials on the basis of the same properties of cement, using some green cement replacement to reduce the cement consumption; develop 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.
SO2:
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 is as follows:
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 to 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， and K2O at the surface of the dust filter bags will react with the SO2 and NO2, and the content of the acid air can be reduced 30~60%.
NOx:
Keep a suitable temperature, control the volume of the air;
Use the reducing gas, such as CO, H2, etc, and mix some Fe2O3, and Al2O3 in 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 to the action, so at the kiln have to control the O2 content carefully.
The selective catalytic reduction also can help to reduce the NOx exhausting, this solution is to insert some selective reducers, such as hydrogen nitride or Urea:
8NH3 + 6NO2 -> 7N2 + 12H2O
6NO + 4NH3 -> 5N2 + 6H2O
4NH3 + 3O2 -> 2N2 + 6H2O
Edited by ZONEL FILTECH