脱硫废水烟道蒸发工艺对烟气酸露点影响分析

为研究脱硫废水烟道蒸发工艺对烟气酸露点的影响,在某600 MW机组上进行烟道蒸发中间试验(中试),实测废水蒸发前后烟气中H_2O和SO_3浓度,并采用不同计算公式计算酸露点。中试结果表明:在空气预热器后1/4烟道中(烟气量为4×10~5～5×10~5 m^3/h)喷入900～1 400 L/h的废水时,烟气中的水蒸气质量分数增加了0.7～0.9个百分点,而烟气中的SO_3浓度却降低30%～50%,说明废水烟道蒸发促进了SO_3向硫酸雾的转化并促进了其在飞灰颗粒上的吸附;废水喷入烟道蒸发后,烟气酸露点反而有所降低,虽然烟气平均温度降低了9～14℃,但废水喷入后的烟温仍基本高于废水喷入后的酸露点,因而脱硫废水烟道蒸发不会造成下游烟道和设备的低温腐蚀。

Analysis on the Influence of the Wastewater Evaporation in Flue Duct to the Flue Gas Dew Point

The effect of the wastewater evaporation in flue duct to the flue gas dew point was studied in this article. Pilot test of the wastewater evaporation was conducted on a 600 MW unit. The H₂O and SO₃ contents in the flue gas were detected and the dew point was calculated using different formulas. The results showed that, when 900~1 400 L/h wastewater was injected in 1/4 flue duct of the 600 MW unit (the amount of flue gas was 4×10⁵~5×10⁵ m³/h), the water vapor in the flue gas increased 0.7%~0.9%, whereas the SO₃ decreased by 30%~50%, which indicated that the transformation from SO₃ to sulfuric acid mist and their adsorption on fly ash particles were improved after the wastewater evaporation. The flue gas dew point decreased by 9~14 ℃ after the evaporation, and the flue gas temperature could be higher than the dew point. Thus, wastewater evaporation in flue duct could not lead to low-temperature corrosion of the downstream ducts and equipments under the condition of pilot test.