Method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore

Abstract

The invention provides a calcium-magnesium composite roasting molybdenum extraction method for low-grade molybdenum ore. The method comprises the following steps: (1) fully grinding and uniformly mixing composite additives calcium oxide and magnesium oxide with the low-grade molybdenum ore; (2) roasting the mixed mineral to obtain a roasted clinker mainly comprising MgMoO4 and CaMoO4; and (3) a sulfuric acid solution is added into the roasted clinker for an acid leaching reaction, and molybdenum-containing leachate is obtained. According to the method, molybdenum is converted into molybdate through composite salt-adding roasting, ore phase conversion of molybdenum is promoted to the maximum extent, the recovery rate of molybdenum is increased, meanwhile, sulfur is converted into insoluble sulfate, sulfur fixation is achieved, the environmental risk is minimized, and the method has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the fields of chemical engineering and metallurgy, and particularly relates to a method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore. Background Art

[0002] In nature, molybdenum mostly exists in the form of sulfides (molybdenite), followed by oxide ores symbiotic with elements such as tungsten, copper, vanadium, rhenium, and niobium. China is the country with the richest molybdenum resources in the world and also the largest country in terms of molybdenum consumption and production. With the continuous increase in molybdenum demand and the continuous exploitation of molybdenum ore resources, the efficient comprehensive utilization of low-grade molybdenum concentrate is crucial for ensuring the healthy and vigorous development of the national economy and society. Although great progress has been made in China's mining and beneficiation technology, a large amount of low-grade molybdenum concentrate is still produced every year. Therefore, researching and developing the comprehensive recovery and utilization technology of low-grade molybdenum concentrate has great theoretical significance and application value.

[0003] At present, the main raw material for molybdenum extraction at home and abroad is molybdenite, and molybdenum can be extracted by oxidative roasting and wet decomposition. The oxidative roasting process has the advantages of high efficiency, high molybdenum extraction rate, and large processing capacity, but it has poor raw material adaptability, serious loss of associated rare and dispersed metals, and low product purity. The wet process has the advantages of strong raw material applicability, simple and flexible process, and high product purity, but it also has disadvantages such as large reagent consumption and long time consumption. Usually, molybdenum metallurgy uses a combined fire method-wet method process for molybdenum extraction. First, the high-efficiency mineral phase transformation of molybdenite is achieved by the fire method, and then molybdenum is flexibly extracted by the wet method. The combined method is especially suitable for low-grade molybdenum concentrate.

[0004] Oxidative roasting can be divided into direct roasting and salt roasting. High-grade molybdenum concentrate usually adopts direct roasting process, while direct roasting of low-grade molybdenum concentrate will generate more insoluble molybdates and produce low-concentration SO2 flue gas that is inconvenient to prepare sulfuric acid, resulting in waste of molybdenum resources and environmental pollution. Salt roasting can convert molybdenum concentrate into molybdates and sulfates, which is an effective means to achieve directional conversion of molybdenum and sulfur fixation. In recent years, some scholars have added calcium agents (lime, limestone, slaked lime) during roasting to oxidize MoS2 into CaMoO4 and CaSO4, significantly reducing the generation of sulfur-containing flue gas. Gan Min et al. added Ca(OH)2 in a ratio of 1:1 and roasted at 650℃ for 90 minutes. The molybdenum retention rate and sulfur fixation rate of low-grade molybdenum concentrate reached 100% and 92.92% respectively, and the molybdenum leaching rate in sulfuric acid leached roasted sand reached 99.12%. Mou Wenning and others used sodium carbonate to roast low-grade, high-gangue molybdenite at low temperature. The molybdate generated during the roasting process had a molybdenum conversion rate of 93.9%. It can be seen that salt roasting can achieve the conversion of molybdenum-rhenium ore while basically solving the problem of SO2 flue gas pollution. However, the impurity elements in low-grade molybdenum concentrate pose new challenges to salt roasting. The diversity of impurity types and volatility of content cause the incomplete mineral phase conversion of a single salt roasting system. Composite roasting is an optimization based on single salt roasting, which fully considers the effects of different salts on the conversion of molybdenum and sulfur, and improves the applicability of salt roasting to raw materials.

[0005] Therefore, the present invention proposes to use a calcium-magnesium composite roasting-acid leaching combined process to efficiently extract molybdenum from low-grade molybdenum ore and fix sulfur at the same time. The additives of this method are cheap and easy to obtain, the process is simple, and both economic and environmental benefits are taken into account. Summary of the invention

[0006] The present invention aims to solve the problems of low molybdenum extraction rate, generation of SO2 flue gas, waste of resources and environmental pollution in the process of molybdenum extraction from low-grade molybdenum ore, and provide a method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore.

[0007] The method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore of the present invention comprises the following process steps:

[0008] Step 1: Grind and mix the composite additives calcium oxide, magnesium oxide and low-grade molybdenum ore in a certain molar ratio;

[0009] Step 2: roasting the mixed minerals at 550-650° C. for 50-90 min in an air atmosphere to obtain roasted clinker mainly composed of MgMoO4 and CaMoO4;

[0010] Step 3: Add 60-80 g / L sulfuric acid solution to the roasted clinker in step 2 at a solid-liquid ratio of 4-6:1 for acid leaching at a temperature of 80-90° C. for 100-150 min to obtain a molybdenum-containing leaching solution.

[0011] Furthermore, the molar ratio of the calcium-magnesium composite additive to molybdenum in the low-grade molybdenum concentrate is 3.0 - 3.6:1, and the molar ratio of calcium oxide to magnesium oxide in the composite additive is 1:0.5 - 1.

[0012] Furthermore, the chemical components of the low-grade molybdenum ore include: by mass percentage, 16 - 18% MoS₂, 14 - 15% FeS₂, 15 - 17% MgCO₃, 3 - 4% CaSO₄, 1 - 2% ZnS, and <1% CuO.

[0013] Furthermore, the roasting temperature is 550 - 650 °C, and the roasting time is 50 - 90 min.

[0014] Furthermore, the concentration of the sulfuric acid solution is 60 - 80 g / L, and the liquid-solid ratio is 4 - 6:1.

[0015] Furthermore, the acid leaching temperature is 80 - 90 °C, and the acid leaching time is 100 - 150 min.

[0016] In the present invention, the concentration of molybdenum in the leachate is determined by inductively coupled plasma optical emission spectrometry (ICP-OES) for the finally obtained leachate to obtain the extraction rate of molybdenum.

[0017] The beneficial effects of the present invention are as follows: The present invention provides a method for extracting molybdenum from low-grade molybdenum ore by calcium-magnesium composite roasting. During the roasting process, calcium oxide and magnesium oxide, non-alkali metals, are used as additives to oxidize molybdenum sulfide into CaMoO₄, MgMoO₄, CaSO₄, and MgSO₄, which improves the conversion rate of molybdenum while reducing the generation of sulfur-containing flue gas. In the combined process of calcium-magnesium composite roasting-acid leaching, the extraction rate of molybdenum can reach over 98%. Compared with the direct roasting-acid leaching process, the extraction rate of molybdenum is increased by more than 1 time, achieving remarkable effects. The molybdenum extraction method of the present invention is particularly suitable for low-grade molybdenum ore, with simple operation, short process, energy conservation and environmental protection, and is suitable for popularization and application. Specific Embodiments

[0018] The present invention will be described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0019] Example 1 Extraction of Molybdenum from Low-Grade Molybdenum Ore by Calcium-Magnesium Composite Roasting

[0020] (1) The composite additives calcium oxide and magnesium oxide are thoroughly ground and mixed with the low-grade molybdenum ore; the molar ratio of the calcium-magnesium composite additive to molybdenum sulfide in the low-grade molybdenum ore is controlled to be 3.6:1, and the molar ratio of calcium oxide to magnesium oxide is 1:1;

[0021] (2) Under an air atmosphere, the mixed minerals are calcined at 600 °C for 60 min to obtain calcined clinker mainly composed of MgMoO4 and CaMoO4;

[0022] (3) The calcined clinker from step 2 is added to a 70 g / L sulfuric acid solution at a solid-liquid ratio of 5:1 for acid leaching. Acid leaching is carried out at a temperature of 90 °C for 120 min to obtain a molybdenum-containing leaching solution.

[0023] The results show that: after treating low-grade molybdenum ore by the combined process of composite salt addition roasting - acid leaching under this system, the extraction rate of molybdenum reaches 99.5%.

[0024] Example 2 Extraction of molybdenum from low-grade molybdenum ore by calcium-magnesium composite roasting

[0025] (1) The composite additives calcium oxide and magnesium oxide are fully ground and mixed with low-grade molybdenum ore; the molar ratio of the calcium-magnesium composite additive to molybdenum sulfide in the low-grade molybdenum ore is controlled to be 3.3:1, and the molar ratio of calcium oxide to magnesium oxide is 1:0.5;

[0026] (2) Under an air atmosphere, the mixed minerals are calcined at 650 °C for 90 min to obtain calcined clinker mainly composed of MgMoO4 and CaMoO4;

[0027] (3) The calcined clinker from step 2 is added to an 80 g / L sulfuric acid solution at a solid-liquid ratio of 6:1 for acid leaching. Acid leaching is carried out at a temperature of 80 °C for 150 min to obtain a molybdenum-containing leaching solution.

[0028] The results show that: after treating low-grade molybdenum ore by the combined process of composite salt addition roasting - acid leaching under this system, the extraction rate of molybdenum reaches 98.6%.

[0029] Example 3 Extraction of molybdenum from low-grade molybdenum ore by calcium-magnesium composite roasting

[0030] (1) The composite additives calcium oxide and magnesium oxide are fully ground and mixed with low-grade molybdenum ore; the molar ratio of the calcium-magnesium composite additive to molybdenum sulfide in the low-grade molybdenum ore is controlled to be 3:1, and the molar ratio of calcium oxide to magnesium oxide is 1:1;

[0031] (2) Under an air atmosphere, the mixed minerals are calcined at 550 °C for 50 min to obtain calcined clinker mainly composed of MgMoO4 and CaMoO4;

[0032] (3) The calcined clinker from step 2 is added to a 60 g / L sulfuric acid solution at a solid-liquid ratio of 4:1 for acid leaching. Acid leaching is carried out at a temperature of 85 °C for 100 min to obtain a molybdenum-containing leaching solution.

[0033] The results show that: after treating low-grade molybdenum ore by the combined process of composite salt addition roasting - acid leaching under this system, the extraction rate of molybdenum reaches 98.1%.

[0034] Comparative Example 1: Extraction of Molybdenum from Low-Grade Molybdenum Ore by Calcination Roasting

[0035] (1) Thoroughly grind and mix the single additive calcium oxide with the low-grade molybdenum ore; control the molar ratio of calcium oxide to molybdenum sulfide in the low-grade molybdenum ore to be 3.6:1;

[0036] (2) Under an air atmosphere, roast the mixed minerals at 600 °C for 60 min to obtain roasted clinker mainly composed of CaMoO4;

[0037] (3) Add the roasted clinker from step 2 to a 70 g / L sulfuric acid solution according to a solid-liquid ratio of 5:1, and perform acid leaching at a temperature of 90 °C for 120 min to obtain a molybdenum-containing leaching solution.

[0038] The results show that: after treating the low-grade molybdenum ore by the single-salt roasting-acid leaching combined process in this system, the extraction rate of molybdenum reaches 79.7%.

[0039] Comparative Example 2: Extraction of Molybdenum from Low-Grade Molybdenum Ore by Direct Roasting

[0040] (1) Thoroughly grind the low-grade molybdenum ore;

[0041] (2) Under an air atmosphere, roast the minerals at 600 °C for 60 min to obtain roasted clinker mainly composed of MoO3;

[0042] (3) Add the roasted clinker from step 2 to a 70 g / L sulfuric acid solution according to a solid-liquid ratio of 5:1, and perform acid leaching at a temperature of 90 °C for 120 min to obtain a molybdenum-containing leaching solution.

[0043] The results show that: after treating the low-grade molybdenum ore by the single-salt roasting-acid leaching combined process in this system, the extraction rate of molybdenum reaches 48.7%.

[0044] It can be seen from the examples and comparative examples that the present invention significantly improves the extraction rate of molybdenum from low-grade molybdenum ore.

Claims

1. A method for extracting molybdenum from low-grade molybdenum ore by calcium-magnesium composite roasting, characterized in that: The steps include: Step 1: Grind and mix the composite additives calcium oxide, magnesium oxide and low-grade molybdenum ore in a certain molar ratio; Step 2: roasting the mixed minerals at 550-650° C. for 50-90 min in an air atmosphere to obtain roasted clinker mainly composed of MgMoO4 and CaMoO4; Step 3: Add 60-80 g / L sulfuric acid solution to the roasted clinker in step 2 at a solid-liquid ratio of 4-6:1 for acid leaching at a temperature of 80-90° C. for 100-150 min to obtain a molybdenum-containing leaching solution.

2. The method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore according to claim 1, characterized in that In step 1, the molar ratio of the sum of calcium and magnesium in the calcium-magnesium composite additive to molybdenum in the low-grade molybdenum concentrate is 3.0-3.6:1, and the molar ratio of calcium oxide to magnesium oxide in the composite additive is 1:0.5-1.

3. The method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore according to claim 1, characterized in that The chemical components of the low-grade molybdenum ore in step 1 include, by mass percentage, MoS2 16-18%, FeS2 14-15%, MgCO3 15-17%, CaSO4 3-4%, ZnS 1-2%, and CuO<1%.

4. The method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore according to claim 1, characterized in that The calcination temperature in step 2 is 550-650° C., and the calcination time is 50-90 min.

5. The method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore according to claim 1, characterized in that The concentration of the sulfuric acid solution in step 3 is 60-80 g / L, and the liquid-to-solid ratio is 4-6:

1.

6. The method for extracting molybdenum by calcium-magnesium composite roasting of low-grade molybdenum ore according to claim 1, characterized in that The acid leaching temperature in step 3 is 80-90° C., and the acid leaching time is 100-150 min.