A circulating
fluidized bed (CFB) reactor composed of a pyrolyzer
and combustor was developed to observe tar emission during pyrolysis
of low rank coal. Tar emission in the CFB pyrolyzer was examined under
a wide range of operating conditions. Emissions of light tar substances
(e.g., benzene, toluene, naphthalene, etc.) could be suppressed at
973 K by enhancement of contact between tar and resultant char in
the pyrolyzer (i.e., enhancement of the volatile–char interaction
(VCI)). It was also confirmed that about 50% of the heavy tar fraction
emissions could be suppressed by the enhancement of VCI at 973 K.
These trends were also observed at higher temperature (1173 K). A
certain amount of heavy tar was emitted even after enhancement of
VCI, so the mechanism of tar elimination was qualitatively determined
using Spiral-type TOF-MS. The heavy tar was homogeneously deposited
on the char and then was cracked to form lighter fractions by enhanced
contact between tar and resultant char during pyrolysis.
Abstract. In this study, a method is presented to decrease halogen compounds in the product oil from thermolysis of polystyrene and polypropylene mixed plastic spiked with tetrabromobisphenol A. A mixture of hydrotalcite and plastic was pyrolyzed in a glass reactor at 400 °C under a nitrogen atmosphere. Bromine compounds in the residual substances were measured. The yield of product oil increased using hydrotalcite as an additive. The bromine compounds that were the major ingredients in the oil after thermolysis at 400 °C from the mixed plastic, which also included toluene, ethyl benzene, styrene, and 1-methylethyl benzene, were 2-bromohexane, 3-bromo-1-propenyl benzene, 4,5-dibromodecane, 1-bromomethylbenzene, 3-bromophenol, and 4-bromo-2,6-dimethylbenzaniline. However, bromine compounds were not detected in the product oil, residue, or gas when hydrotalcite was added. After the thermolysis of the plastic, bromine compounds in the product oil may decrease because bromine was captured by the added hydrotalcite.
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