Sulfate Aerosol Formation during Pyrolysis and Mining of High Sulfur Indian Coals

The sulphur deposition and atmospheric sulphates are detrimental to ecosystems, harming aquatic lives and plants, and damaging to a wide range of terrestrial plant life. This also results in creation of yellow clouds that reflect sunlight, reducing the atmospheric transparency which can be measured by Aerosol Optical Depth (AOD) index. The sulphate particles also influence the formation of clouds by acting as Cloud Condensation Nucleus (CNN). In the present study, investigation into SO₂ emission and sulfate aerosol formation during pyrolysis and mining of high sulfur NE coals has been discussed. The North Eastern Region (NER) of India has a substantial deposit of high sulfur (2-8%) coal with low ash, high volatile matter (35-45%) and high vitrinite maceral contents. During combustion and carbonization of these coals, sulfur is emitted to the atmosphere as SO₂ mainly in the temperature region 600-850°C which is further oxidized to SO₄^{2- and this process is catalyzed by the metal ions present in the environment. In the present investigation gas and particulate samples were collected from different environments viz, coke oven (pilot plant of 100kg/batch) and from coke industries and mine site in winter season in between January to February. The SO₂ concentrations was found in the range 0.29-97.83 μg/m3, 0.23-0.56 μg/m3 and 0.147-0.62 μg/m3 in coke oven, coke industries and mine site respectively. While the SO₄2- concentrations observed were 0.002-0.533 μg/m3, 0.029-0.21 μg/m3 and 0.06-0.14 μg/m3 in coke oven, coke industries and mine site respectively. In coke industries both SO₂ and SO₄2- concentrations lower than that of coke oven pilot plant because in coke industry, washed coal were used for coke production when in coke oven unwashed coals were used. Moreover, it has also been observed that in the mine site, SO₂ and SO₄2- concentration mainly contributes from the coal burning and nearby coke ovens. Hence, the present study on SO₂ emission and SO₄2- aerosol formation has made a significant contribution towards the national as well as global emission inventories.}