Recovery of iron from steel metallurgical slag

In some contain small amounts of niobium and iron ore country in the former Soviet Union. China's Baotou Bayan Obo iron ore mine contains Nb ₂ O ₅ 0.1%～0.15%, TFe 30%～38%, TRE5%～6%, and the comprehensive utilization value is high. However header niobium mineral iron are scattered distributed in the body, embedded in fine particle size (mean 0.02mm), is not yet effective method niobium mineral enrichment, recovery process mainly by the steel, i.e., iron ore and iron ore concentrate depleted In the blast furnace (1800m ³ ) iron smelting is reduced into molten iron (including Nb 0.06% ~ 0.1%), rare earth is into the blast furnace slag (including REO13% ~ 15%), blast furnace hot metal in the open hearth or converter steelmaking é“ŒIt is oxidized into the steelmaking slag. In the early open slag, Nb ₂ O ₅ can reach 0.5% to 0.7%. Then, using the flat slag as raw material, the second iron making is carried out in a small blast furnace (55 m ³ ), and the obtained molten iron containing Nb is 0.5% to 1.3%, and then the converter is blown to slag. The chemical composition of the converter slag is: Nb ₂ O ₅ 7% to 9%, MnO 50% to 60%, TiO ₂ 1.8% to 2.3%, TFeO 5% to 10%, SiO ₂ 15% to 25%, P ₂ O ₅ 4% ~10%. There are several treatment methods for this converter slag, two of which are listed here.

First, electric furnace reduction production of low grade ferroniobium

In order to separate the free iron in the slag and reduce the phosphorus content, a step-by-step smelting method is adopted. The first step is to control the amount of the reducing agent ( coke ) and lower the furnace temperature according to the principle that P ₂ O ₅ and FeO are reduced prior to Nb ₂ O ₅ . And dephosphorization and dephosphorization are carried out under the conditions of adding a dephosphorization agent (NaCl:Na ₂ CO ₃ =1:1); the slag after de-ironing is added to the coke in the second step of melting the coltan in the electric furnace. The composition of the obtained low-grade ferroniobium is: Nb 14% to 16%, Si < 2%, MnO 40% to 60%, P1% to 2%, and C6% to 8%. The cerium iron is finely ground and then oxidized, and the resulting cerium oxide-containing concentrate is further leached with an acid, followed by solvent extraction of the cerium oxide product.

Second, the manganese extraction process

The slag contains 50% to 60% Mn , and manganese can be enriched in cerium. To this end, the manganese in the slag is characterized by the presence of low-cost Mn ^{2 +} , and the converter slag is calcined with ammonium sulfate at 200-230 ° C, and the reaction is:

MnO+(NH ₄ ) ₂ SO ₄ =MnSO ₄ +2NH ₃ ↑+H ₂ O

Calcining the clinker and then leaching the manganese with water, the manganese leaching solution has a manganese content of 80-100 g/L, the manganese recovery rate is 95%, and the bismuth grade in the leaching slag is more than doubled, and can be used for preparing intermediate ferroniobium containing cerium >30% or The extraction process is followed by extraction of cerium oxide. The method has the advantages that although FeO in the slag can react with ammonium sulfate to form FeSO ₄ during calcination, the pH of the leachate is 5-6 due to water immersion, and hydrolysis precipitation occurs when Fe ^{2 + is} at pH=2. Therefore, the purity of the manganese leaching solution is high, and the removal of the impurity iron with the greatest interference greatly facilitates the extraction of the electrolytic manganese; since the silicon is not leached, the filtration is smooth.