1. Introduction of Flue-gas Desulfurization
Flue-gas desulfurization (FGD) is a set of technologies used to remove sulfur dioxide (SO
2) from exhaust flue gases of fossil-fuel power plants, steel company etc, and from the emissions of other sulfur oxide emitting processes. Limestone-gypsum desulfurization process is one of the most widely used desulfurization technologies in the world. About 90% thermal power plants in Japan, Germany, and the United States adopted this technology for the flue gas desulfurization .

Part2
2. Working Principle
Limestone is used as the desulfurization absorbent. Limestone is crushed and ground into powder. Limestone powder is mixed with water to form the absorption slurry. In the absorption tower, the absorption slurry is mixed with the flue gas. The sulfur dioxide in the flue gas is oxidized with calcium carbonate in the slurry and air blasted from the lower part of the tower to form calcium sulfate and calcium sulfate. After reaching a certain degree of saturation, the crystal forms dihydrate gypsum.
The limestone-gypsum wet desulfurization system includes the following systems: limestone feeding and slurry preparation system, flue gas system, absorption tower system and oxidizing air system, gypsum dehydration and wastewater system, process water system, electrical and thermal control system

Part3
3. Technological Advantages
1) It is the mature technology and has wide application range with high desulfurization efficiency which is up to 95%.
2) Limestone is cheap and easy to get.
3) The system runs reliably and has excellent load-changing operation characteristics.
4) By-products can be fully utilized. Gypsum is a kind of good building materials.

Part4
4. Limestone
Limestone is a sedimentary rock. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). In order to ensure good performance and high desulfurization absorption capacity, limestone powder as a desulfurization absorbent should have the following main qualities:

Technical Parameter of Limestone powder:

Content of Calcium Oxide(CaO)	≥50%
Particle Size	250 Mesh D95 -325 Mesh D90 (45Micron D95-60 Micron D90)
Content of Silicon Dioxide (SiO2)	≤1.50%
Content of Magnesium Oxide (MgO)	≤4.00%
Content of Aluminium Oxide(Al2O3)	≤0.10%
Content of Ferric Oxide (Fe2O3)	≤0.20%
Others	≤0.60%
Loss on ignition (LOI)	≥43.60%
HCl Insoluble	≤3.00%

Part5
5. ZENITH’s Mills for Limestone Grinding
1) MTW Trapezium Grinding Mill

 

Limestone Grinding Projects Which Use MTW Grinding Mills

CASE1
Model: 3 Sets of MTW175Z Trapezium Grinding Mills
Raw Material: Limestone
Final Product: Desulfurization Agent
Output Size: 325 mesh D90
Location: China


CASE2
Model: 1 Set of MTW175Z Trapezium Grinding Mill
Raw Material: Limestone
Output Size: 250 Mesh D95
Location: Colombia


2）LM Vertical Roller Mill

1 Raw Material Silo 2 Belt scale conveyor 3 Magnetic separator 4 Bucket Elevator
5 Air-lock feeder 6 LM vertical roller mill 7 Pulse Bag Filter 8 Blower
9 Belt Conveyor 10 Magnetic Separator

Schematic Diagram of LM Vertical Milling System:

 Limestone Grinding Projects Which Use MTW Grinding Mills

CASE1
Model: 1 Set of LM130K Vertical Roller Grinding Mill
Raw Material: Limestone
Output Size: 325 Mesh D90

CASE2
Model: 1 Set of LM190K Vertical Roller Grinding Mill
Raw Material: Limestone
Output Size: 200 Mesh D80
Location: Russia