脱硫废水添加对煤燃烧时汞析出特性的影响

EFFECT OF DESULFURIZATION WASTEWATER ADDITION ON MERCURY RELEASE CHARACTERISTICS DURING COAL COMBUSTION

为探究含氯脱硫废水溶液添加对煤燃烧时汞析出特性的影响,分别利用沉降炉和管式炉实验装置进行了3种煤在1200℃下的燃烧实验。实验时通过改变模拟脱硫废水溶液的添加量来控制燃煤中氯的质量分数分别为0.00%、0.02%、0.04%和0.06%。分析煤燃烧后烟气中汞浓度、吸收液、飞灰和煤灰中汞含量的变化情况发现:随着加氯量的增加,烟气中Hg~0浓度逐渐降低,Hg^(2+)浓度则逐渐升高,但对Hg^(t)(气态总汞)浓度的提升效果相对较差。当加氯量为0.06%时,煤种B在沉降炉中燃烧后烟气中Hg~0浓度下降约2.3μg/m^(3),而Hg^(2+)浓度提高约2.6μg/m^(3),但Hg^(t)浓度仅提高了0.3μg/m^(3)。氯的添加也会使飞灰中汞含量增加,煤灰中汞含量降低。通过综合对比分析沉降炉和管式炉实验结果发现:无论是否添加氯,煤在沉降炉中燃烧后烟气中Hg~0比例均小于管式炉实验结果。当煤种B加氯量为0.06%时,在沉降炉和管式炉中燃烧后烟气中Hg~0含量占比分别为50.6%和67.8%。此外,还发现3种煤粉在管式炉中加氯燃烧后汞的析出率提高趋势均较沉降炉明显。故含氯脱硫废水溶液的添加可以改变煤燃烧时汞的析出特性,且有利于促进烟气中Hg~0的氧化,对燃煤烟气脱汞具有重要作用。

In this study,the combustion experiments of three kinds of coal at 1200 ℃ were implemented by using a drop-tube furnace and tubular furnace experimental devices respectively,to explore the effect of cchlorine-containing desulfurization wastewater addition on mercury release characteristics during coal combustion.In the experiment,the content of chlorine in coal was controlled by changing the mass fraction of simulated desulfurization wastewater solution to 0.00%,0.02%,0.04% and 0.06% respectively.Then by analysing the change of mercury concentration in flue gas,absorption solution,fly ash and coal ash after coal combustion,it was found that with the increase of chlorine dosage,the concentration of Hg~0 in flue gas gradually decreased,while the concentrations of Hg^(2+) gradually increased.However,the effect of Hg^(t) concentration was subtle.When the chlorine dosage was 0.06%,the Hg~0 concentration in the flue gas after coal type B was burned in the drop-tube furnace decreased by about 2.3 μg/m^(3),but the concentrations of Hg^(2+) increased by about 2.6 μg/m^(3),but the concentration of Hg^(t) only increased by 0.3 μg/m^(3).The addition of chlorine not only increased the mercury content in fly ash but also decreased the mercury content in coal ash.Through a comprehensive comparative analysis of the experimental results of drop-tube furnace and tubular furnace,it was found that the Hg~0 ratio in the flue gas after coal combustion in drop-tube furnace was less than in tubular furnace,whether chlorine was added or not.When the chlorination amount of coal type B was 0.06%,the proportion of Hg~0 after combustion in drop-tube furnace and tubular furnace was 50.6% and 67.8% respectively.In addition,it was also found that the mercury release rate of the three kinds of coal combustion after added chlorine in the tubular furnace was more obvious than that in drop-tube furnace.Therefore,the addition of chlorine-containing desulfurization wastewater solution could not only change the release characteristics of mercury during coal combustion,but also promoted the oxidation of Hg~0 in flue gas,which played an important role in mercury removal from coal-fired flue gas.