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锌在金属消耗排行中占第5位,仅次于铁、铝、铜、锰。锌的用途广泛,锌能与多种有色金属形成合金,是经济建设不可或缺的有色金属[1]。目前,我国的锌合金生产主要采用火法冶炼,在冶炼过程中,为了除去高温状态下锌合金表面生成的氧化物,提高纯度,采用加入大量氯化铵晶体的方法[2]。但是,氯化铵在高温下产生大量白色烟雾,造成严重的环境污染。
氯化铵在100 ℃开始挥发,在328 ℃分解成NH3和HCI,而NH3和HCI在空气中遇冷又重新化合成氯化铵,形成白烟。在氯化铵白烟中既含有颗粒物又含有气态污染物,且烟气中的氯化铵微粒多属于微细颗粒物。何益波等[3-4]采样并测出白烟中的颗粒物平均粒径分布在1 μm以下,重量轻,不易下沉,也不易溶于水。在烟气处理设备中,只有湿式洗涤器能够同时去除烟气中的微细颗粒物和气态污染物[5-7],而作为湿式洗涤器的填料塔具有结构简单、气液接触面积大、运行可靠等明显优势,在烟气脱硫、脱黑等工业废气净化方面发挥了重要作用[8-10]。
通常,传统的填料塔采用顶部喷淋方式,这存在较严重的水雾排放问题[11-15],须在喷淋上部另加除雾器,进而增加了设备投资和能耗。为此,在研究氯化铵微粒净化中,提出了一种底喷式填料塔。烟气先与喷淋液滴接触,进行初净化,较大水滴落入底部水箱,气流携带细水雾,经过填料层过滤,不仅增强了颗粒物净化效果,而且减少水雾排放。同时,润湿的填料表面有利于增强填料的吸附作用,提高二次净化效果。所以,底喷式填料塔既可去除微细颗粒物,又能有效控制水雾排放。
虽然使用纯水作为洗涤液的成本较低,但对微细颗粒物降尘效果较差[16]。为了降低水的表面张力,增加颗粒物的润湿性,有研究[17-18]表明,化学抑尘是一种新颖且效率高的粉尘防治办法。而大部分的抑尘剂均添加了阴离子表面活性剂和非离子表面活性剂[19],表面活性剂的添加会进一步提升对微细颗粒物的脱除效率。
本研究分别选用SDBS(阴离子型)、AEO-9(非离子型)、A-7(非离子型)配制成洗涤液,采用底喷填料塔净化氯化铵微粒,通过对比研究,筛选出较为理想的表面活性剂,不仅提高了微细颗粒物的脱除效率,且废水的生物降解性好,对环境没有二次污染,为细颗粒物的高效净化提供参考。
Enhancement effect of ammonium chloride particles removal efficiency of bottom spray packed tower based on surfactant
- Received Date: 30/08/2019
- Available Online: 01/06/2020
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Key words:
- ammonium chloride particles /
- surfactant /
- bottom spray /
- packed tower /
- removal efficiency
Abstract: In order to efficiently remove fine particles and reduce water mist emissions, a bottom spray type packed tower was designed. According to the principle of reducing water surface tension with the surfactant, the purification effects of drinking water, SDBS, AEO-9, A-7 on ammonium chloride particles with particle size less than 1 μm were compared and analyzed. The results showed that when the mass concentration of ammonium chloride particles at the inlet of the bottom spray packed column was 124.9~194.3 mg·m−3, the particle removal efficiency by the drinking water washing liquid was only about 40%, and the mass concentration of the ammonium chloride particles at the outlet was higher than 70 mg·m−3. When SDBS or AEO-9 surfactant washing liquid was used, the particle removal efficiency was greatly improved. The enhancement effect of efficiency by AEO-9 was more obvious. When the concentration of AEO-9 increased up to 0.004%, the removal efficiency reached 74.8%, and the concentration of the ammonium chloride particles at the outlet was 26.5 mg·m−3. When A-7 washing liquid with concentration 0.3% was used, the removal efficiency was 89%, and the concentration of the ammonium chloride particles at the outlet was only 15 mg·m−3. Through above analysis, the surfactant washing liquid had an enhancement effect on the removal of fine particles.