Abstract

The zinc content of basic oxygen furnace (BOF) sludges is too high for direct recycling into the blast furnace via the sinter plant, as excessive zinc concentrations are detrimental for the refractory lining of the blast furnace. However, by partial and selective removal of zinc from the BOF sludge, the residual sludge can be used as a secondary iron resource in the blast furnace. In this paper, BOF sludge was leached with aqueous ammonia, aqueous solutions of ammonium salts (chloride, carbonate, and sulfate), and aqueous mixtures of ammonia and ammonium salt. The mixtures of ammonia and ammonium salt could leach more zinc with respect to either the aqueous ammonia or the aqueous ammonium salt solution. The ammonia–ammonium carbonate (AAC) mixture was selected as the most suitable lixiviant due to the high zinc leaching efficiency in combination with a high selectivity towards iron; furthermore, this combination does not introduce unwanted chloride or sulfate impurities in the residue. The leaching process was optimized in terms of the liquid-to-solid ratio, total ammonia concentration, ammonium:ammonia molar ratio, temperature, and leaching time. The co-dissolved iron was precipitated as a hydroxide after oxidation of ferrous to ferric ions by an air stream, without co-precipitation of zinc, while the dissolved zinc could be easily recovered as zinc sulfide by precipitation with ammonium sulfide. The (almost) closed-loop process was successfully up-scaled from 10 mL to 1 L scale.

Graphical Abstract

中文翻译：

---

氨水和碳酸铵混合淋洗法选择性去除转炉污泥中的锌。

摘要

碱性氧气炉（BOF）污泥中的锌含量过高，无法通过烧结厂直接循环回高炉，因为过量的锌浓度对高炉的耐火衬里有害。但是，通过从BOF污泥中部分选择性地去除锌，可以将残留的污泥用作高炉中的二次铁资源。在本文中，BOF污泥用氨水，铵盐（氯化物，碳酸盐和硫酸盐）的水溶液以及氨水和铵盐的含水混合物浸出。相对于氨水或铵盐水溶液，氨和铵盐的混合物可以浸出更多的锌。氨-碳酸铵（AAC）混合物被选为最合适的浸滤剂，因为它具有高的锌浸出效率和对铁的高选择性。此外，这种结合不会在残留物中引入不需要的氯化物或硫酸盐杂质。根据液固比，总氨浓度，铵：氨摩尔比，温度和浸出时间对浸出过程进行了优化。通过气流将亚铁氧化为三价铁离子后，共溶解的铁以氢氧化物的形式沉淀出来，而没有锌的共沉淀，而溶解的锌则可以通过与硫化铵的沉淀而容易地以硫化锌的形式回收。（几乎）闭环过程已成功地从10 mL放大到1 L规模。这种结合不会在残留物中引入不需要的氯化物或硫酸盐杂质。根据液固比，总氨浓度，铵：氨摩尔比，温度和浸出时间对浸出过程进行了优化。通过气流将亚铁氧化为三价铁离子后，共溶解的铁以氢氧化物的形式沉淀出来，而没有锌的共沉淀，而溶解的锌则可以通过与硫化铵的沉淀而容易地以硫化锌的形式回收。（几乎）闭环过程已成功地从10 mL放大到1 L规模。这种结合不会在残留物中引入不需要的氯化物或硫酸盐杂质。根据液固比，总氨浓度，铵：氨摩尔比，温度和浸出时间对浸出过程进行了优化。通过气流将亚铁氧化为三价铁离子后，共溶解的铁以氢氧化物的形式沉淀出来，而没有锌的共沉淀，而溶解的锌则可以通过与硫化铵的沉淀而容易地以硫化锌的形式回收。（几乎）闭环过程已成功地从10 mL放大到1 L规模。通过气流将亚铁氧化为三价铁离子后，共溶解的铁以氢氧化物的形式沉淀出来，而没有锌的共沉淀，而溶解的锌则可以通过与硫化铵的沉淀而容易地以硫化锌的形式回收。（几乎）闭环过程已成功地从10 mL放大到1 L规模。通过气流将亚铁氧化为三价铁离子后，共溶解的铁以氢氧化物的形式沉淀出来，而没有锌的共沉淀，而溶解的锌则可以通过与硫化铵的沉淀而容易地以硫化锌的形式回收。（几乎）闭环过程已成功地从10 mL放大到1 L规模。

图形概要