SO_2和H_2O(g)对新疆高钠煤中钠挥发和形态迁移的研究

Effect of H_2O(g) and SO_2(g) on the volatilization and transformation of sodium during Xinjiang high-sodium coal combustion

在水平管式炉上进行了400-1 100℃新疆高钠煤恒温燃烧实验,并利用逐级提取的方法分析煤及煤灰中钠的赋存形态,研究煤中钠的释放和形态迁移特性。重点考察700和1100℃下H_2O(g)和SO_2(g)单因素及双因素对煤中无机钠挥发和形态迁移的影响。结果表明,随着温度的升高,煤中钠的释放比例逐渐增大,其中,有机态钠最先析出,其次是水溶态无机钠,硅铝酸盐形式的无机钠则由于高热稳定性不易分解或挥发。低温下(700℃)H_2O(g)的存在降低了钠的挥发,而较高温度下(1 100℃)焦炭与水蒸气反应生成的局部还原性气氛促进煤中钠的挥发,但当入口气氛中H_2O(g)浓度高于20%时,促进作用减小。SO_2的存在抑制了煤中钠的挥发,随着燃烧温度升高,SO_2对钠的抑制作用减弱。H_2O和SO_2双因素作用下,低温下(700℃)抑制了煤中钠的挥发,而较高温度下(1 100℃)钠的挥发特性取决于两者在入口气氛中的浓度。对于选取的高钠煤,20%H2O和2.0×10-3SO_2入口气氛下,1 100℃煤燃烧钠的挥发比例由86%提高到了87.1%。

Combustion experiment of Xinjiang coal with high sodium content was carried out in a horizontal tube furnace at 400-1 100 ℃. The occurrence of sodium in coal and ash was analyzed by sequential extraction method to study the release and transformation characteristics of sodium,especially the effect of H2O（ g） and SO2（ g） at700 ℃ and 1 100 ℃. The results show that,the release ratio of sodium in coal increases gradually with the increase of temperature. The sodium in organic form vaporizes first,followed by water-soluble inorganic sodium,while the inorganic sodium in the form of aluminosilicate is difficult to vaporize due to high thermal stability. At lower temperature（ 700 ℃）,H2O（ g） has a negative effect on the volatilization of sodium,while at higher temperature（ 1 100 ℃）,the reductive atmosphere formed by the reaction of char and H2O（ g） promotes the volatilization of sodium. When the proportion of H2O（ g） is larger than 20% in inlet gas,the promotion effect of H2O（ g） is weakened. SO2 can inhibit sodium volatilization,while the inhibiting effect of SO2 becomes less significant as the temperature increases from 700 ℃ to 1 100 ℃. In the presence of both H2O（ g） and SO2,the sodium volatilization at 700 ℃ is inhibited. The combination effect of H2O（ g） and SO2 at 1 100 ℃ depends on its concentration. Under the atmosphere containing 20%H2O and 2.0 × 10-3 SO2 the total volatilization ratio of sodium increases from 86% to 87.1%.