New Strategy toward Household Coal Combustion by Remarkably Reducing SO₂ Emission

A large amount of sulfur dioxide (SO₂) will be released during rural household coal combustion, causing serious environmental pollution. Therefore, it is very urgent to develop a clean and efficient fuel to substitute rural household coal controlling SO₂ emission. In this paper, a new strategy toward scattered coal combustion with remarkably reducing SO₂ emission was proposed. Coal and compound additive of Al₂O₃ and CaCO₃ were blended and then copyrolysis at 1050 °C was performed to produce clean coke. First, the sulfur content of clean coke was reduced, meanwhile, generating sulfur fixation precursor during pyrolysis. Then, clean coke is used for efficient sulfur fixation during the subsequent combustion process to reduce SO₂ emissions. The effects of combustion temperature, Al/S molar ratio, and the mechanism of sulfur retention during clean coke combustion were studied in the tube furnace and muffle furnace. The mechanism can be attributed the following reason: (a) CaS produced during pyrolysis and CaO decomposed by complex additives were oxidized during combustion, and CaO captured the SO₂ released from clean coke combustion, which formed CaSO₄. (b) CaSO₄ reacts with Al₂O₃ to produce calcium sulfoaluminate at high temperatures, which improves the sulfur fixation efficiency of clean coke combustion at high temperatures. In a word, this new strategy can greatly reduce the emission of SO₂, thus helping to solve rural household coal pollution problems.