镍烟灰水洗脱盐工艺研究

    Research on nickel soot desalination by washing

    • 摘要: 镍烟灰是镍高温冶炼过程中,从尾气收集的烟尘,富含铅等重金属和钠等可溶性盐。镍烟灰成分复杂、盐含量高等因素制约其资源化利用。如何高效分离可溶性盐是镍烟灰资源回收的技术关键。以甘肃金川硫化镍矿冶炼烟灰(主要物相有PbSO4、Na2S2O8、CdSO4等,呈致密团聚形态)为研究对象,系统考察单级水洗过程液固比、时间、温度对可溶性盐洗脱率的影响,研究发现,单级水洗过程中液固比为20 mL/g时,25 ℃下水洗15 min,Na、K、Cd、Zn的洗脱率分别达到85.39%、56.77%、51.21%、37.17%;而铅的洗脱率极低(<0.14%),Ni、Fe、Al、Cu的洗脱率分别为22.73%、3.85%、17.73%、22.56%;水洗后烟灰质量因盐分溶出而减少,Pb含量从20.70%提升至37.63%(富集约2倍),Fe、Cu、Sn、Si、Bi、Ca等不溶性金属组分升高,分别由9.87%、2.58%、4.49%、3.65%、2.23%、3.57%提升至16.00%、3.44%、5.21%、5.88%、2.92%、3.87%。研究结果揭示了单级水洗过程水资源消耗大。基于此,提出镍烟灰三级逆流水洗工艺,通过梯次循环操作,同步实现可溶性盐高效洗脱、金属铅的富集和水资源循环利用。研究结果表明:三级逆流水洗液固比降至3 mL/g时,仍保持Na、Cd的洗脱率>80%,Zn、K的洗脱率为65.80%、42.41%。物相及形貌分析表明,水洗主要溶解可溶性钠、镉盐导致非晶态增加,但未改变晶体结构及团聚形貌;Pb等金属元素富集而Na、Cd降低。本研究表明水洗能高效协同脱盐与重金属富集,所构建的三级逆流工艺显著提升Na、Cd的洗脱率,大幅降低洗脱过程水资源消耗(较单级节水85%),为镍烟灰资源化利用预处理提供技术支撑。

       

      Abstract: Nickel soot is the soot collected from the tail gas during the nickel high-temperature smelting process, which is rich in heavy metals such as lead and soluble salts such as sodium. The complex composition of nickel soot and the high salt content constrain its resource utilization. How to efficiently separate soluble salts is the technical key to nickel soot resource recovery. Taking the smelting soot of Gansu Jinchuan Nickel Sulfide Mine(the main phases of which are PbSO4, Na2S2O8, CdSO4, etc., which are in the form of dense agglomeration) as the research object, it systematically investigates the effects of liquid-solid ratio, time and temperature on the elution rate of soluble salts in the process of single-stage washing, and finds that, in the process of single-stage washing when the liquid-solid ratio is 20 mL/g, and the washing is carried out in water under 25 ℃ for 15 min, the elution rates of Na, K, Cd, and Zn reach 85.39%, 56.77%, 51.21%, and 37.17%, respectively; while the elution rate of Pb is extremely low(<0.14%), and that of Ni, Fe, Al, and Cu are 22.73%, 3.85%, 17.73%, and 22.56%, respectively; the ash quality decreases due to the dissolution of the salts after the aqueous washing, and the Pb content is elevated from 20.70% to 37.63% (about 2-fold enrichment), and insoluble metal fractions such as Fe, Cu, Sn, Si, Bi, and Ca are elevated from 9.87%, 2.58%, 4.49%, 3.65%, 2.23%, and 3.57% to 16.00%, 3.44%, 5.21%, 5.88%, 2.92%, and 3.87%, respectively. The results of the study reveal the high water consumption of the single-stage washing process. Based on this, a three-stage counter-flow washing process for nickel soot is proposed, which simultaneously achieves efficient elution of soluble salts, enrichment of metallic lead, and recycling of water resources through a graded cycle operation. The results show that when the liquid-solid ratio of the three-stage counter-flow washing is reduced to 3 mL/g, the elution rate of Na and Cd is still maintained at >80%, and the elution rates of Zn and K are 65.80% and 42.41%. Physical and morphological analyses show that washing mainly dissolves soluble sodium and cadmium salts leading to an increase in amorphous state, but do not change the crystal structure and agglomerate morphology; Pb and other metal elements are enriched while Na and Cd decrease. This study shows that washing can efficiently synergise desalination and heavy metal enrichment, and the constructs three-stage counter-flow washing process significantly improves the elution rate of Na and Cd, significantly reduces the water consumption of the elution process (85% water saving compared with the single-stage), and provides technological support for the pre-treatment of nickel fume ash resource utilization.

       

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