One. Process Overview of Lime Stone-Gypsum Method (abbreviated as FGD) Desulfurization System
Limestone-Gypsum desulfurization technology boasts a long history of development, having matured with continuous research and improvements in recent years. It is known for its high desulfurization efficiency, stable operation, strong adaptability to coal types, abundant and inexpensive desulfurizing agent sources, and the convenience of utilizing by-products. These features have made it a mainstream choice in the desulfurization industry worldwide. The desulfurization process involves flue gas from the furnace or kiln being drawn into the desulfurization absorption tower reaction zone by an induced draft fan. The gas then comes into contact with the droplets of the suspended liquid sprayed downward from the tower's spray pipes, where mass transfer and absorption reactions occur, removing SO2, SO3, HCl, and HF from the flue gas. After the desulfurization, the flue gas is passed through a demister to remove any liquid droplets, exits the absorption tower from the top, and is then discharged through the chimney.
S02 and S03 react with limestone in the slurry, forming calcium sulfite and calcium sulfate. Air is introduced into the slurry pool of the absorption tower to oxidize the calcium sulfite into calcium sulfate, which crystallizes into gypsum (CaSO4·2H2O). The byproduct gypsum is obtained after dewatering through a filter press.
II. Reaction Mechanism:
SO2 + H2O → H2SO3 Absorption
CaCO3 + H2SO3 → CaSO3 + CO2 + H2O Neutralization
CaSO3 + 1/2 O2 → CaSO4 oxidation
CaSO3 + 1/2 H2O → CaSO3•1/2 H2O crystalline
CaSO4 + 2H2O → Crystalline CaSO4•2H2O
CaSO3 + H2SO3 → Ca(HSO3)2 pH Control
III. Performance Guarantee:
FGD desulfurization efficiency ≥95%
Calcium-sulfur ratio Ca/S (molar ratio) not greater than 1.03
The desulfurization system has an availability rate of not less than 98%.
Pressure Drop: 800-1200 Pa
Dew point after demister: Less than 75 mg/Nm³
Load range: 30-130%
Power Consumption: Approximately 1.0% - 1.2% of the unit's capacity
