A typical flue gas from the combustion of fossil fuels (coals) contains amounts of nitrogen oxides (NOx), sulfur dioxide (SO2) and particulate matter. The nitrogen oxides are derived from the nitrogen in the ambient air as well as from any nitrogen-containing compounds in the fossil fuel. The sulfur dioxide is derived from any sulfur-containing compounds in the fuels. The particulate matter is composed of very small particles of solid materials and very small liquid droplets which give flue gases their smoky appearance.
The combination of pollution abatement technologies applied at Tanjung Jati B 3&4 to ensure the plant’s compliance with the more stringent Indonesian legislative limits. Sulfur dioxide (SO2) emissions removed before the flue gas is discharged to the atmosphere by a process called Flue Gas Desulphurization (FGD). There are two kinds of FGD, dry FGD system and wet system. FGD dry system use venturi scrubber and FGD wet system typically using limestone slurry.
Tanjung Jati B 3&4 using wet FGD system using limestone slurry to remove SO2. The absorber module converts or absorbs the Sulfur Dioxide (SO2) in the flue gas by chemical reactions with the limestone slurry. Calcium carbonate (CaCO3) in the limestone slurry is converted to Calcium Sulfite (CaSO3). Oxidation air is introduced in the reaction tank of the absorber module where calcium sulfite (CaSO3) is converted to Calcium Sulfate (CaSO4).
- Gas to sorbent (limestone slurry) reaction
CaCO3 + SO2 + H2O à CaSO3 –> ½H2O + CO2
Calcium Carbonate in limestone + flue gas –> Calcium Sulfite
- Forced Oxidation reaction
CaSO3 • ½H2O + O2 + H2O à CaSO4 • 2H2O
Calcium Carbonate (in limestone) + flue gas –> Calcium Sulfate
The FGD plant on Tanjung Jati B 3&4 is designed to remove approximately 95% of the SO2 contained within the flue gases, ensuring the ability to meet the EPC contract specified limits ≤ 300mg/Nm3 (Indonesian legislative limit regulation is 750 mg/Nm3). And also by-product “gypsum” cake from dewatering process by design has solids content of 90% (moisture ≤ 10%).