轉爐爐石/氫氧化鈣吸收劑高溫硫酸化與碳酸化反應之研究

Abstract

本研究以微分固定床反應器探討燃煤廢氣成分(SO2、CO2、O2、H2O和NOx)對氫氧化鈣(HL)、轉爐爐石(BOFS)以及HL/BOFS(9/1)吸收劑在高溫下的硫酸化與碳酸化反應之影響。 各吸收劑硫酸化反應轉化率隨反應溫度(750-950℃)和SO2(1000-5000ppm)上升而上升。Ca(OH)2和HL/BOFS(9/1)吸收劑之轉化率大約相同，皆高於BOFS。與Ca(OH)2或BOFS在二氧化硫/氧氣/氮氣中反應的結果比較，水氣單獨加入反應氣體中、水氣與氮氧化物同時加入，以及在氮氧化物存在時增加氧氣濃度，皆明顯促進氫氧化鈣之硫酸化反應，其餘氣體組成條件則無影響；對BOFS而言，單獨加入氮氧化物，以及高濃度水氣(20%)與二氧化碳同時存在時，會明顯降低其硫酸化反應，但其餘氣體組成條件則有助益。 氫氧化鈣最佳碳酸化溫度為600℃。提高二氧化碳濃度(13%~80%)能促進碳酸化反應。在600℃、13%CO2和5%O2反應1分鐘與1小時的轉化率分別為0.88和0.93；BOFS在相同條件下反應1小時轉化率為0.24。NOx會輕微抑制氫氧化鈣碳酸化反應，但當氮氧化物與水氣同時加入時，或單獨加入水氣時則無影響。添加氮氧化物對BOFS碳酸化無影響，而水氣存在時有輕微促進作用。二氧化硫與二氧化碳同時存在下，降低反應溫度(600~750℃)、降低SO2濃度和提高CO2濃度，明顯降低硫酸化轉化率、提升碳酸化轉化率。在600℃、13%CO2、5%O2和1000ppmSO2下反應10分鐘後，Ca(OH)2的碳酸化和硫酸化轉化率分別為0.91和0.07，BOFS為0.24和0.07，HL/BOFS為0.78和0.03。

The effects of compoments of flue gas generated from coal combustion on the sulfation and carbonation reactions of Ca(OH)2(HL), basic oxygen furnace slag(BOFS), and HL/BOFS(9/1) sorbents at high temperatures were studied using a differential fixed-bed reactor. The sulfation rate for each sorbent increased with increasing reaction temperature(750-950℃) and SO2 concentration(1000-3000ppm). The conversions for Ca(OH)2 and HL/BOFS(9/1) were about the same and higher than that for BOFS.For Ca(OH)2, compared to the case of reaction under SO2/O2/N2 mixture, adding H2O alone, or adding H2O and NOx simultaneously, or increasing the O2 concentration(from 5% to 20%) when NOx was added enhanced the sulfation reaction, while the other gas compositions had little effect. For BOFS, adding NOx alone, or increasing H2O concentration(from 10% to 20%) when both H2O and CO2 were added inhibited the sulfation reaction, while the other gas compositions had enhancing effects. The optimum carbonation temperature was 600℃for Ca(OH)2. The carbonation conversion increased as CO2 concentration (13%-80%) increased. Conversions of 0.88 and 0.93 were achieved when Ca(OH)2 reacted at 600℃,13% CO2, 5% O2 for 1min and 1h, respectively. An 1h conversion of 0.24 was achieved when BOFS was carbonated at same conditions. The presence of NOx slightly inhibited the carbonation of Ca(OH)2, while the precence of H2O or H2O/NOx had little effect. For the carbonation of BOFS, the presence of NOx had little effect and the presence of H2O had a slight enhancement effect. When both SO2 and CO2 were present, the carbonation conversion increased and the sulfation conversion decreased significantly with decreasing reaction temperature (600-750℃) or SO2 concentration (1000-5000ppm) and with increasing the CO2 concentration. The carbonation and sulfation conversions achieved for a sorbent reacted at 600℃,13% CO2, 5% O2 and 1000ppm SO2 for 10min were 0.91 and 0.07 for Ca(OH)2, 0.24 and 0.07 for BOFS, and 0.78 and 0.03 for HL/BOFS, respectively.