Iron Blast Furnace Slag/Ca(OH)2 and Basic Oxygen Furnace Slag/Ca(OH)2 Sorbents for SO2 Removal at High Temperatures
Date Issued
2008
Date
2008
Author(s)
Liao, Kun-Hsiang
Abstract
A differential fixed-bed reactor was employed to measure the reactivities of iron blast furnace slag(BFS)/Ca(OH)2 (HL) and basic oxygen furnace slag(BOF)/Ca(OH)2(HL) sorbents towards SO2 at high temperatures(750oC -950oC) and medium SO2 concentration(3000ppm) of flue gas. The one hour utilization of Ca and SO2 capture of sorbent increased with increasing reaction temperature, whether the sorbent had been slurried or not. Slurried BFS/HL sorbents were more reactive than unslurried ones, mainly due to the formation of calcium silicate hydrates in the slurried sorbents. The sorbent reactivity reached the highest at a BFS/HL ratio of 10/90 and decreased with increasing BFS/HL ratio thereafter. While the BFS particles enhanced the dispersion of HL particles and thus raised the sorbent reactivity at low BFS/HL ratios, they were low in reactivity and caused the coherence of sorbent particles at temperatures>750oC and thus reduced the sorbent reactivity at high BFS/HL ratios. Slurried BOF/HL sorbents had higher reactivities than unslurried ones because the sorbent particles were smaller and better mixed. The sorbent reactivity reached the highest at a BOF/HL ratio of 10/90 and decreased with increasing BOF/HL ratio slightly thereafter. BOF/HL sorbents were more reactive than BFS/HL sorbents, because BOF particles didn’t sinter and had a high content of ferric oxide, which can catalyze the reaction with SO2 at high temperatures. For BFS/HL sorbents with a BFS/HL ratio<30/70, the high temperature reactivity was much higher than the low temperature reactivity, measured at 60oC, 70%RH, and 1000ppm SO2 in a previous study. For BOF/HL sorbents, the high temperature reactivity was significantly higher than the low temperature reactivity at each BOF/HL ratio. Comparing the high temperature reactivities of sorbents prepared from BFS/HL, BOF/HL, and fly ash(FA)/HL indicated that the SO2 capture of sorbent varied in the following order: BOF/HL > BFS/HL > FA/HL. Sorbents with reactivities higher than HL alone can be prepared by adding a suitable amount of BFS(less than 25-28wt%) or BOF(less than 28-44wt%) to HL.
Subjects
hydrated lime
Iron Blast Furnace Slag
Basic Oxygen Furnace Slag
SO2
air pollution control
Type
thesis
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