Kinetics of the Reaction of Ca(OH)2/Fly ash Sorbents with SO2 at High Temperatures
Date Issued
2007
Date
2007
Author(s)
Lin, Cheng-Yue
DOI
zh-TW
Abstract
A differential fixed-bed reactor was employed to study the reaction between fly ash/Ca(OH)2 sorbents and SO2 at high temperatures(650~
950℃).Slurried and unslurried sorbents were used;the slurried sorbents were prepared by slurrying the solid in water at 65℃ for 16h with a
liquid/solid weight ratio of 10/1.Foil-like calcium silicate hydrates were
formed in the slurried sorbents. These sorbents have greater surface areas than that of Ca(OH)2or fly ash. But these sorbents tended to sinter at high temperatures, resulting in the decrease of sorbent reactivity,when the fly ash content was high.Also, the reactivity of calcium silicate decreased with increasing temperature due to chemical equilibrium limitation. The
utilizations of calcium for sorbents increased with increasing SO2
concentration and reaction time,but the effect of reaction temperature varied with the composition of sorbent and reaction time.The utilizations
of calcium at one hour for sorbents were higher than that of Ca(OH)2 alone when the fly ash/Ca(OH)2 weight ratio was less 4/6.However, the SO2 capture per unit weight of sorbent decreased with increasing fly ash content.The fly ash itself was unreactive.The utilizations of calcium for sorbents at 950℃ were higher than those at 750℃ when fly ash content was low(30wt%),but the utilizations of calcium were higher at 750℃ when the fly ash content was high(70wt%).The unslurried sorbents were more reactive than the slurried ones ,especially when the fly ash content was greater than 30wt%.For the two kinds of fly ashes used in this study, the one with a higher Fe content gave sorbents of higher The reactivities.
utilization of calciums and SO2 captures were raised when the sorbents were prepared with the addition of CaSO3 and/or CaSO4. Comparing
with the low temperature results (Ho and Shih,1992, 1993;Lin et al.
,2003), the utilizations of calcium and SO2 captures were higher for sorbents reacted at high temperatures when the fly ash content was less than 40%.Adding a proper amount of fly ash(<40wt%) to Ca(OH)2 without prior slurrying treatment can raise the utilization of Ca(OH)2 in the high-temperature desulfurization process.
Subjects
飛灰
氫氧化鈣
Ca(OH)2
fly ash
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-R94524079-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):b1476d5f36d39774ce2c782530158740