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.