SO_2和H_2O(g)对新疆高钠煤中钠挥发和形态迁移的研究

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%。

Effect of H2O(g) and SO2(g) on the volatilization and transformation of sodium during Xinjiang high-sodium coal combustion

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) at 700℃ 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%.