阅读说明：本技术 一种钼精矿除铁的方法 (Method for removing iron from molybdenum concentrate ) 是由 杨斌 李洋 王飞 徐宝强 田阳 熊恒 陈秀敏 吴鉴 曲涛 刘大春 戴永年 于 2021-06-02 设计创作，主要内容包括：本发明公开一种钼精矿除铁的方法,将钼精矿与氯化钙混合均匀后置于内热式真空炉内焙烧,真空氯化焙烧可除去钼精矿中的黄铁矿,冷凝盘内得到磁黄铁矿；焙烧残留物酸浸、过滤并干燥,除去剩余的铁的氧化物；本发明采用真空氯化焙烧和酸浸的方式有效去除钼精矿中杂质铁,该方法具有流程短、成本低、金属回收率高,对环境污染小的优点。(The invention discloses a method for removing iron from molybdenum concentrate, which comprises the steps of uniformly mixing the molybdenum concentrate with calcium chloride, placing the mixture into an internal heating type vacuum furnace for roasting, removing pyrite in the molybdenum concentrate through vacuum chlorination roasting, and obtaining pyrrhotite in a condensation disc; acid leaching, filtering and drying the roasting residue to remove the residual iron oxide; the method effectively removes the impurity iron in the molybdenum concentrate by adopting the modes of vacuum chlorination roasting and acid leaching, and has the advantages of short flow, low cost, high metal recovery rate and small environmental pollution.)

1. A method for removing iron from molybdenum concentrate is characterized by comprising the following specific steps:

(1) ball milling and uniformly mixing: carrying out ball milling on the molybdenum concentrate and calcium chloride for 2-3 hours and uniformly mixing;

(2) vacuum chloridizing roasting: placing the uniformly mixed material obtained in the step (1) in an internal heating type vacuum furnace, heating to 800-;

(3) and (3) acid-leaching the residue obtained in the step (2) for 5-8h by hydrochloric acid, washing by deionized water, filtering and drying.

2. The method for removing iron from molybdenum concentrate according to claim 1, wherein the content of Fe in the molybdenum concentrate is 0.4-4% by mass, and the Fe exists in the form of pyrite and iron oxide.

3. The method for removing iron from molybdenum concentrate according to claim 1, wherein the purity of calcium chloride is more than 98%.

4. The method for removing iron from molybdenum concentrate according to claim 1, wherein the mass ratio of the molybdenum concentrate to the calcium chloride is 1: 1-5.

5. The method for removing iron from molybdenum concentrate according to claim 1, wherein the mass fraction of hydrochloric acid is 8-12%.

6. The method for removing iron from molybdenum concentrate according to claim 1, wherein the solid-to-liquid ratio g: mL of the roasting residue to hydrochloric acid is 1: 5-6.

Technical Field

The invention relates to a method for removing iron from molybdenum concentrate, belonging to the field of vacuum metallurgy.

Background

Molybdenum disulfide is a high-grade solid lubricating material which is commonly used and indispensable in high and new technical fields such as aerospace, war industry, nuclear industry and the like and civil engineering. The industrial preparation of high-purity molybdenum disulfide from molybdenum concentrate by physical purification method contains high-content iron (FeS) in which about 80% of iron is present in the form of pyrite₂) The Mohs hardness is high, and is very unfavorable for the lubricating property of the molybdenum disulfide.

The traditional hydrochloric acid leaching only can leach calcite and galena in molybdenum concentrate, an oxidant is required to be added for oxidation leaching iron removal, and the traditional hydrochloric acid leaching method is high in medicine consumption and energy consumption. And a large amount of acidic wastewater is generated in the acid leaching process of the physical purification method, so that the environmental-friendly treatment cost is high, and the molybdenum loss can be caused by oxidation leaching.

Disclosure of Invention

Aiming at the problems, the invention provides a method for removing impurity iron in molybdenum concentrate by vacuum chlorination roasting, which comprises the steps of uniformly mixing the molybdenum concentrate with calcium chloride, then putting the mixture into a vacuum furnace for roasting, directly removing pyrite in the molybdenum concentrate, then removing a small amount of residual iron oxide by hydrochloric acid leaching, and analyzing from an iron removal principle.

The technical scheme of the invention is as follows:

a method for removing impurity iron in molybdenum concentrate by vacuum chlorination roasting comprises the following specific steps:

(1) ball milling and uniformly mixing: adding the molybdenum concentrate and calcium chloride into a ball milling tank, and ball milling for 2-3 hours and uniformly mixing;

(2) vacuum chloridizing roasting: placing the uniformly mixed material in the step (1) in an internal heating type vacuum furnace, heating to 800-850 ℃ under the pressure of less than 5Pa, preserving the heat for 40-60min, and taking out the roasting residue after cooling; obtaining pyrrhotite in a condensation plate of the internal heating type vacuum furnace;

(3) and (3) carrying out hydrochloric acid leaching on the roasting residue in the step (2), washing with deionized water, filtering and drying.

The content of Fe in the molybdenum concentrate is 0.4-4% by mass, and the molybdenum concentrate exists in the form of pyrite and iron oxide, wherein 70-80% of the molybdenum concentrate is pyrite, and the rest is iron oxide.

The purity of the calcium chloride is more than 98 percent.

The mass ratio of the molybdenum concentrate to the calcium chloride is 1: 1-5.

The mass fraction of the hydrochloric acid is 8-12%; the solid-to-liquid ratio (g: mL) of the roasting residue to hydrochloric acid is 1: 5-6.

The principle of the invention is as follows:

metal sulfide impurity and CaCl in molybdenum concentrate₂Reacting under vacuum condition to generate chloride and CaCl₂The possible reactions with the components in the molybdenum concentrate are shown in the following (1), (2), (3), (4), (5) and (6):

MoS₂+2CaCl₂＝MoCl₄(g)+2CaS (1)

FeS+CaCl₂＝FeCl₂(g)+CaS (2)

Cu₂S+CaCl₂＝2CuCl(g)+CaS (3)

CuS+CaCl₂＝CuCl₂(g)+CaS (4)

ZnS+CaCl₂＝ZnCl₂(g)+CaS (5)

PbS+CaCl₂＝PbCl₂(g)+CaS (6)

the vapor pressure of the chloride is large, and the chloride can be volatilized and removed under vacuum condition, the relationship between the saturated vapor pressure of the metal chloride involved in the reactions (1), (2), (3), (4), (5) and (6) and the temperature is shown in FIG. 1, when the pressure is 10Pa, the temperature is 710 ℃ enough to make FeCl₂、PbCl₂、BiCl₃、CuCl、ZnCl₂And (6) volatilizing.

The standard gibbs free energy at different temperatures of the reactions (1) to (6) under normal pressure was calculated, as shown in fig. 2(a), the reaction of each sulfide with calcium chloride under normal pressure did not occur until 1100 ℃, and the gibbs free energy at a pressure of 1Pa was calculated according to the "gibbs free energy function method", as shown in fig. 2(b), the reaction of ferrous sulfide with calcium chloride under 1Pa was theoretically possible, the initial temperature of the reaction was about 810 ℃, and the reaction was more likely to occur with an increase in temperature, because the product had a gas, and the reaction was more likely to proceed with a decrease in pressure. The iron is converted into corresponding chloride gas to be volatilized and removed, the product calcium sulfide is left in the molybdenum concentrate, and the CaS is an inorganic substance, is dissolved in ammonium salt, is easy to react with acid and can be removed in a subsequent process.

The phase of condensate collected after vacuum chlorination roasting is mainly iron sulfide, while the vapor pressure of iron-sulfur compound is very small, and the condensate can not volatilize at experimental temperature, the impurity ferrous sulfide is chloridized to generate ferrous chloride, the ferrous chloride is presumed to react with certain gas phase in the volatilization process to further generate iron sulfide and condense on a condensation plate, and gas phase S possibly existing in the system₂The possible reactions of PbS, ZnS and ferrous chloride are as follows:

S₂(g)+2FeCl₂(g)＝2FeS+2Cl₂(g) (7)

PbS(g)+FeCl₂(g)＝FeS+PbCl₂(g) (8)

ZnS(g)+FeCl₂(g)＝FeS+ZnCl₂(g) (9)

gibbs free energy at 10Pa for the above reaction was calculated and plotted as shown in FIG. 3, where PbS, ZnS and FeCl₂The reaction of (A) is theoretically spontaneous, and it can be seen from the relationship between Gibbs free energy and temperature that FeCl increases with increasing temperature₂The less readily resulfurized, it is inferred that the iron sulfide in the raw material is chlorinated into FeCl₂Then, the volatile sulfides such as PbS and ZnS in the molybdenum concentrate volatilize together, and when the molybdenum concentrate meets a condensation disc with lower temperature, iron sulfide is regenerated through reaction and condensed on the condensation disc.

The invention has the advantages thatThe method has the advantages that the process flow is simple, the operation is convenient, the chlorination process is carried out in vacuum, the direct yield of molybdenum is high, impurities can be collected and recovered by a condensation method, the environment is not polluted, the use amount of acid is greatly reduced, and the treatment amount of wastewater is also reduced; by the method, other impurities such as Bi in the molybdenum concentrate can be removed₂S₃、PbS、ZnS。

Drawings

FIG. 1 is a graph of vapor pressure versus temperature for metal chlorides;

FIG. 2 is Gibbs free energy of reaction of sulfide with calcium chloride ((a) 10)⁵Pa，(b)1Pa)；

FIG. 3 is the Gibbs free energies of reactions (7), (8) and (9) at 10 Pa;

FIG. 4 is an XRD pattern of the condensate of example 1.

Detailed Description

The invention will be further illustrated with reference to specific examples, but the scope of the invention is not limited thereto.

Example 1

A method for removing impurity iron in molybdenum concentrate by vacuum chlorination roasting comprises the following specific steps:

(1) ball milling and uniformly mixing: adding the molybdenum concentrate and calcium chloride into a ball milling tank for ball milling for 2 hours; the content of Fe in the molybdenum concentrate is 1.42 percent by mass, the molybdenum concentrate exists in the form of pyrite and ferric oxide, the purity of calcium chloride is more than 98 percent, and the mass ratio of the molybdenum concentrate to the calcium chloride is 1: 1.5;

(2) vacuum chloridizing roasting: placing the uniformly mixed material in the step (1) in an internal heating type vacuum furnace, heating to 850 ℃ under the pressure of less than 5Pa, preserving the heat for 40min, and taking out the roasting residue after cooling; obtaining a by-product pyrrhotite in a condensation disc of the internal heating type vacuum furnace;

(3) and (3) carrying out hydrochloric acid leaching on the roasting residue obtained in the step (2) for 5h, wherein the mass fraction of hydrochloric acid is 10%, the solid-to-liquid ratio (g: mL) of the roasting residue to the hydrochloric acid is 1:6, washing the roasting residue to be neutral by deionized water, filtering and drying the roasting residue at 90 ℃ for 15h, and detecting that the mass percentage content of iron in the product is 0.082%, and the iron removal rate is about 94.23%.

FIG. 4 is an XRD pattern of the condensate from the vacuum distillation in step (2) of this example, from which it can be seen that the condensate has a main component of Fe_0.94S, the fact that iron is recovered in the form of pyrrhotite in the vacuum chlorination process is shown, and the pyrrhotite is mainly used as a raw material for producing sulfuric acid, sulfur, carbon disulfide and the like and is widely applied to industries such as petrochemical industry, metallurgy, rubber, papermaking, military and the like.

Example 2

A method for removing impurity iron in molybdenum concentrate by vacuum chlorination roasting comprises the following specific steps:

(1) ball milling and uniformly mixing: adding the molybdenum concentrate and calcium chloride into a ball milling tank for ball milling for 2.5 hours; the mass percent of Fe in the molybdenum concentrate is 0.76%, the molybdenum concentrate exists in the form of pyrite and ferric oxide, the purity of calcium chloride is more than 98%, and the mass ratio of the molybdenum concentrate to the calcium chloride is 1: 1;

(2) vacuum chloridizing roasting: placing the uniformly mixed material in the step (1) in an internal heating type vacuum furnace, heating to 820 ℃ under the pressure of less than 5Pa, preserving the heat for 50min, cooling, and taking out the roasting residue; obtaining a by-product pyrrhotite in a condensation disc of the internal heating type vacuum furnace;

(3) and (3) carrying out hydrochloric acid leaching on the roasting residue obtained in the step (2) for 8h, wherein the mass fraction of hydrochloric acid is 12%, the solid-to-liquid ratio (g: mL) of the roasting residue to the hydrochloric acid is 1:5, washing the roasting residue to be neutral by deionized water, filtering the roasting residue, drying the roasting residue for 16h at the temperature of 80 ℃, and detecting that the mass percentage content of iron in the product is 0.045% and the iron removal rate is about 94.08%.

Example 3

A method for removing impurity iron in molybdenum concentrate by vacuum chlorination roasting comprises the following specific steps:

(1) ball milling and uniformly mixing: adding the molybdenum concentrate and calcium chloride into a ball milling tank for ball milling for 3 hours; the mass percent of Fe in the molybdenum concentrate is 1.42%, the molybdenum concentrate exists in the form of pyrite and ferric oxide, the purity of calcium chloride is more than 98%, and the mass ratio of the molybdenum concentrate to the calcium chloride is 1: 5;

(2) vacuum chloridizing roasting: placing the uniformly mixed material in the step (1) in an internal heating type vacuum furnace, heating to 800 ℃ under the pressure of less than 5Pa, preserving the heat for 60min, cooling, and taking out the roasting residue; obtaining a by-product pyrrhotite in a condensation disc of the internal heating type vacuum furnace;

(3) and (3) carrying out hydrochloric acid leaching on the roasting residue obtained in the step (2) for 6h, wherein the mass fraction of hydrochloric acid is 8%, the solid-to-liquid ratio of the roasting residue to the hydrochloric acid is (g: mL)1:6, washing the roasting residue to be neutral by deionized water, filtering the obtained product, and drying the obtained product at 100 ℃ for 12h, wherein the detected mass percentage content of iron in the product is 0.061%, and the iron removal rate is about 95.70%.

Comparative example 1

In the existing research of a first-stage acid leaching iron reduction test of molybdenum disulfide, nitric acid is added in a hydrochloric acid leaching process for oxidation iron removal, the nitric acid is 140kg/t, the solid-to-liquid ratio is 1:2, the leaching temperature is 80 ℃, the leaching time is 3 hours, the content of iron in raw material molybdenum concentrate is reduced from 0.67% to 0.12%, and the iron removal rate is 83.52%.

Comparative example 2

The traditional process for reducing iron is to adopt acid leaching (HCl: HF is 1:1), the mass concentration of hydrochloric acid is 10%, the mass concentration of hydrofluoric acid is 20%, the leaching temperature is 80 ℃, the leaching time is 16h, the iron content of molybdenum concentrate is reduced from 0.65% to 0.35%, and the iron removal rate is 46.15%.

In conclusion, the iron removal rates of the embodiments 1 to 3 are higher than those of the comparative examples 1 and 2, the molybdenum concentrate and the calcium chloride are uniformly mixed and then are placed into a vacuum furnace for roasting, pyrite in the molybdenum concentrate is removed firstly, and then the residual small amount of iron oxide is removed through hydrochloric acid leaching, so that the iron removal effect is good.