Refining method of crude tellurium

Abstract

The invention relates to a crude tellurium refining method which comprises the following steps: (1) physically and uniformly mixing 1-3 parts by mass of calcium chloride, 1-5 parts by mass of ammonium nitrate and 2-8 parts by mass of borax to form a refining agent; (2) fully mixing a refining agent and crude tellurium in proportion in a rod mill to obtain a mixture with the particle size of 0.07-0.2 mm; (3) heating, melting and smelting the mixture in a heating furnace to respectively obtain refined tellurium and smelting slag floating on the surface of the refined tellurium; and fishing out the smelting slag, introducing refined tellurium into a graphite ingot mold, and naturally cooling to room temperature to obtain a refined tellurium ingot with the purity of 99.99% or above. The method is short in technological process, easy to operate, small in environmental pollution, high in product yield and low in production cost.

Description

Technical Field

[0001] The present invention relates to the field of refining tellurium, and in particular to a method for refining crude tellurium. Background Art

[0002] Tellurium is known as the "vitamin of modern industry, national defense and cutting-edge technologies" and is widely used in fields such as metallurgy, chemical industry, glass, photovoltaic, and thermoelectric refrigeration. It is an important rare metal indispensable for modern industries. Due to the dispersed distribution of tellurium resources on the earth, it is mainly recovered through enrichment in the copper smelting process and then through the extraction process of copper smelting anode slime.

[0003] Restricted by the fluctuations in the control of the main process parameters for the treatment of copper smelting anode slime, the tellurium recovery processes are different. The mainstream processes are the electrolysis method and the chemical method. The tellurium produced by the electrolysis method is mainly 99% - 99.95%, and a small part can produce refined tellurium with a purity of 99.99%. The quality of the process products fluctuates greatly. The chemical method can produce refined tellurium with a purity of over 99.99%, but this method requires strict control of the process and the environment. The adjustment range of process parameters is small, resulting in high production costs and low product yield. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for refining crude tellurium with low cost and high yield.

[0005] To solve the above problems, a method for refining crude tellurium according to the present invention includes the following steps: (1) By mass, 1 - 3 parts of calcium chloride, 1 - 5 parts of ammonium nitrate, and 2 - 8 parts of borax are physically mixed evenly to form a refining agent; (2) The refining agent and the crude tellurium are fully mixed in a rod mill according to a mass ratio of 1:10 - 1:50 to obtain a mixture with a particle size of 0.07 - 0.2 mm; (3) The mixture is heated and melted in a heating furnace to obtain refined tellurium and melting slag floating on the surface of the refined tellurium respectively; the melting slag is fished out, and the refined tellurium is poured into a graphite ingot mold and naturally cooled to room temperature to obtain a refined tellurium ingot with a purity of over 99.99%.

[0006] The crude tellurium in step (2) refers to the crude tellurium produced by the chemical method and the electrolysis method, and its tellurium content is 99% - 99.95%.

[0007] The conditions for heating and melting in step (3) refer to a melting temperature of 500 - 650 °C, and after all melting, the melting temperature is stabilized at 550 - 600 °C for melting for 30 - 120 min.

[0008] The present invention has the following advantages compared with the prior art: 1. The refining agent based on borax of the present invention uses a slag-making smelting process to refine crude tellurium. Borax is a flux for the tellurium casting process and decomposes into boric anhydride (B 2 O 3 ) at high temperature, combines with the compounds (such as Na 2 O, CaO, etc.) mixed in tellurium to form a low-melting-point complex, reduces the melting point of molten tellurium or alloy, thereby improving the fluidity of the slag and enhancing the slag-making purification efficiency.

[0009] 2. The present invention adds calcium chloride and ammonium nitrate to the borax flux, so that impurities such as lead, iron, and copper in the crude tellurium form substances that are easy to volatilize at high temperature during the slag-making refining process, and quickly volatilize into the flue gas and slag under the agitation of nitrogen gas generated by the slag itself.

[0010] 3. The process flow of the present invention is short, the operation is simple, the environmental pollution is small, the product yield is high, and the production cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following further describes in detail the specific embodiments of the present invention with reference to the drawings.

[0012] Figure 1 It is the flow chart of the present invention. SPECIFIC EMBODIMENTS

[0013] As Figure 1 shown, a refining method for crude tellurium includes the following steps: ⑴ By mass (g), 1-3 parts of calcium chloride, 1-5 parts of ammonium nitrate and 2-8 parts of borax are physically mixed evenly to form a refining agent.

[0014] ⑵ The refining agent and the crude tellurium are fully mixed in a rod mill according to a mass ratio (g / g) of 1:10 - 1:50 to obtain a mixture with a particle size of 0.07 - 0.2 mm.

[0015] The crude tellurium refers to the crude tellurium produced by chemical methods and electrolytic methods, and its tellurium content is 99% - 99.95%.

[0016] ⑶ The mixture is heated and melted in a heating furnace, and the melting temperature is 500 - 650 °C. After all melting, the melting temperature is stabilized at 550 - 600 °C for 30 - 120 min. After the smelting is completed, refined tellurium and the smelting slag floating on the surface of the refined tellurium are obtained respectively. At this time, the impurities are basically smelted into the slag. The smelting slag is fished out, and the refined tellurium is poured into a graphite ingot mold and naturally cooled to room temperature to obtain a refined tellurium ingot with a purity of more than 99.99%.

[0017] Reaction principle of the present invention: CaCl 2 + NH 4 NO3 = 2NH 4 Cl + CaNO 3 Na 2 B 4 O 7 ·10H 2 O + CaNO 3 = CaO·Na 2 O·B 4 O 6 + NO 2 (g) + 10H 2 O(g) Pb(OH) 2 + 2NH 4 Cl = 2NH 3 (g) + PbCl 2 (g) + 2H 2 O(g) Cu(OH)2 + 2NH4Cl = 2NH 3 (g) + CuCl 2 (g) + 2H 2 O(g) Fe(OH) 3 + 3NH 4 Cl = 3NH 3 (g) + FeCl 3 (g) + 3H 2 O(g) NO 2 + NH 3 = N 2 (g) + H 2 O(g) In the present invention, borax decomposes into boric anhydride (B 2 O 3 ) at high temperature, and combines with the compounds (such as Na 2 O, CaO, etc.) mixed in tellurium to form a low-melting-point complex; the added calcium chloride and ammonium nitrate make the impurities such as lead, iron, and copper in crude tellurium form substances that are easy to volatilize at high temperature during the slag-making refining process, and quickly volatilize into the flue gas and slag under the agitation of nitrogen generated by the slag itself.

[0018] Example 1 A refining method for crude tellurium, comprising the following steps: ⑴ Physically mix 1 g of calcium chloride, 1 g of ammonium nitrate, and 8 g of borax evenly to form a refining agent.

[0019] ⑵ Thoroughly mix 10 g of the refining agent with 100 g of crude tellurium in a rod mill to obtain a mixture with a particle size of 0.07 mm.

[0020] The composition table of crude tellurium is shown in Table 1.

[0021] Table 1 Composition Table of Crude Tellurium ⑶ Heat and melt the mixture in a heating furnace. The melting temperature is 650 °C. After complete melting, keep the melting temperature stable at 550 °C and melt for 120 min. After the melting is completed, use a graphite ladle to scoop out the melting slag in the crucible. The material obtained at the lower part of the crucible is refined tellurium. Scoop out the refined tellurium with a graphite spoon and pour it into a graphite ingot mold. After natural cooling to room temperature, a refined tellurium ingot with a purity of 99.9918% is obtained. The composition table of the refined tellurium is shown in Table 2.

[0022] Table 2 Composition Table of Refined Tellurium Example 2 A method for refining crude tellurium, comprising the following steps: ⑴ Physically mix 3 g of calcium chloride, 5 g of ammonium nitrate, and 2 g of borax evenly to form a refining agent.

[0023] ⑵ Thoroughly mix 10 g of the refining agent with 500 g of crude tellurium in a rod mill to obtain a mixture with a particle size of 0.2 mm.

[0024] The composition table of crude tellurium is shown in Table 3.

[0025] Table 3 Composition Table of Crude Tellurium ⑶ Heat and melt the mixture in a heating furnace. The melting temperature is 500 °C. After complete melting, keep the melting temperature stable at 600 °C and melt for 30 min. After the melting is completed, use a graphite ladle to scoop out the melting slag in the crucible. The material obtained at the lower part of the crucible is refined tellurium. Scoop out the refined tellurium with a graphite spoon and pour it into a graphite ingot mold. After natural cooling to room temperature, a refined tellurium ingot with a purity of 99.9912% is obtained. The composition table of the refined tellurium is shown in Table 4.

[0026] Table 4 Composition Table of Refined Tellurium Example 3 A method for refining crude tellurium, comprising the following steps: ⑴ Physically mix 2 g of calcium chloride, 3 g of ammonium nitrate, and 5 g of borax evenly to form a refining agent.

[0027] ⑵ Thoroughly mix 10 g of the refining agent with 300 g of crude tellurium in a rod mill to obtain a mixture with a particle size of 0.12 mm.

[0028] The composition table of crude tellurium is shown in Table 5.

[0029] Table 5 Composition Table of Crude Tellurium (3) Heat and melt the mixture in a heating furnace. The melting temperature is 550 °C. After complete melting, keep the melting temperature stable at 575 °C and melt for 60 min. After the melting is completed, use a graphite ladle to scoop out the melting slag in the crucible. The material obtained at the lower part of the crucible is refined tellurium. Use a graphite spoon to scoop out the refined tellurium and pour it into a graphite ingot mold. After natural cooling to room temperature, a tellurium ingot with a purity of 99.9910% is obtained. The composition table of the refined tellurium is shown in Table 6.

[0030] Table 6 Composition Table of Refined Tellurium

Claims

1. A method for refining crude tellurium, comprising the following steps: (1) By mass, 1-3 parts of calcium chloride, 1-5 parts of ammonium nitrate and 2-8 parts of borax are physically mixed and uniformly formed into a refining agent; (2) the refining agent and crude tellurium are fully mixed in a rod mill at a mass ratio of 1:10 to 1:50 to obtain a mixture with a particle size of 0.07 to 0.2 mm; ⑶ The mixture is heated and melted in a heating furnace to obtain refined tellurium and smelting slag floating on the surface of the refined tellurium; the smelting slag is removed, and the refined tellurium is introduced into a graphite ingot mold and naturally cooled to room temperature to obtain a refined tellurium ingot with a purity of more than 99.99%.

2. A method for refining crude tellurium as claimed in claim 1, characterized in that: The crude tellurium in step (2) refers to the crude tellurium produced by chemical method and electrolytic method, and its tellurium content is 99%~99.95%.

3. The method for refining crude tellurium according to claim 1, characterized in that: The heating and melting conditions in step (3) refer to a melting temperature of 500-650° C., and after all the materials are melted, the melting temperature is stabilized at 550-600° C. for 30-120 minutes.

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