Method for preparing lead at low temperature and recycling alkali through collaborative smelting of alkaline hydroxide and galena

Abstract

The invention provides a method for preparing lead at low temperature and recycling alkali through collaborative smelting of basic hydroxide and galena, and relates to the technical field of metallurgy. According to the technology, a large amount of heat can be released in the melting process of hydroxide, the temperature of a reaction system is promoted to be increased violently, galena is promoted to be decomposed into metal lead and sulfur, after galena and alkaline hydroxide are evenly mixed, vacuum distillation is carried out for 30-60 min under the condition that the heating temperature is 450-650 DEG C, and the galena absorbs a large amount of heat, the temperature is increased, and the metal lead and sulfur are obtained. The method comprises the following steps: decomposing galena to obtain simple substance lead and condensed alkaline hydroxide, leaching alkali by using an aqueous solution at 50-80 DEG C to obtain simple substance lead and an alkaline hydroxide solution, carrying out evaporative crystallization on the alkaline hydroxide solution to obtain solid alkali, and recycling the solid alkaline hydroxide to be continuously used for mixed decomposition with galena. The method is simple in technological process, low in energy consumption, low in preparation temperature, low in carbon emission in the vacuum decomposition process, clean, free of pollution and wide in application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a method for preparing lead at low temperature by co-smelting alkaline hydroxide and galena and recycling the alkali. Background Art

[0002] At present, lead is mainly prepared from galena as raw material, and metallic lead is obtained through traditional pyrometallurgical processes such as "blast furnace smelting-reverberatory furnace blowing-electrolytic refining". The process is long and energy-intensive. The smelting process can produce SO2 flue gas, dust, etc., and there are many problems such as high environmental pollution risk, high equipment requirements, and poor operating environment. It does not meet the sustainable development concept of low-carbon green development.

[0003] The applicant previously proposed a method for preparing metallic lead by directly decomposing galena, using vacuum distillation technology to decompose galena (PbS) directly at a temperature of 950-1400°C to produce metallic lead and elemental sulfur. However, this method has a low lead sulfide decomposition rate, and some lead sulfide evaporates into the condensate before it can decompose in a vacuum environment. In addition, the decomposition reaction requires a heating chamber of about 1000°C, which consumes a lot of energy. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing lead at low temperature by co-smelting alkaline hydroxide and galena and recycling the alkali, which solves the problem of high energy consumption in the prior art.

[0005] To achieve the above object, the present invention is implemented by the following technical scheme: a method for preparing lead at low temperature by smelting alkaline hydroxide and galena in coordination and recycling alkali, comprising the following steps:

[0006] (1) uniformly mixing galena and alkaline hydroxide to obtain a mixture;

[0007] (2) Pressing the mixture of step (1) into small pieces to ensure that it is not sucked away by the vacuum pump during the vacuum distillation process:

[0008] (3) subjecting the mixture after briquetting in step (2) to vacuum distillation to obtain elemental lead and alkaline hydroxide residues, and condensing the decomposed S element above the distillation furnace;

[0009] (4) leaching the residue from step (3) using high temperature distilled water;

[0010] (5) separating the leaching solution from step (4) from lead to obtain metallic lead and an alkaline hydroxide aqueous solution;

[0011] (6) The aqueous solution in step (5) is evaporated and crystallized to obtain an alkaline hydroxide which can be reused.

[0012] Preferably, the temperature rising procedure of the vacuum distillation includes: placing the required materials in a graphite crucible, placing the graphite crucible in a vacuum furnace, first turning on the circulating cooling water, then turning on the vacuum pump, and when the vacuum degree drops to 5-30 Pa, starting to heat up at a heating rate of 5-10°C / min; when the temperature rises to 450-700°C, keeping it warm for 30min-60min.

[0013] Preferably, the briquetting method in step (1) can be unidirectional pressing or cold isostatic pressing, as long as the mixture is in block shape, and the hydroxide can be sodium hydroxide, potassium hydroxide, or calcium hydroxide.

[0014] Preferably, the mixing ratio of galena and alkaline hydroxide in step (2) is 1:0.5-0.8 by mass.

[0015] Preferably, the vacuum distillation in step (3) is carried out at a temperature of 450 to 700° C., for a time of 30 to 60 min, and at a vacuum degree of 5 to 30 Pa.

[0016] Preferably, the temperature of the pure water used for leaching in step (4) is 50-100°C.

[0017] Preferably, the liquid-solid separation in step (5) can be carried out by filtering with a conventional suction flask.

[0018] Preferably, the evaporation crystallization temperature in step (6) is 80-100° C. and the time is 120 min to 300 min.

[0019] The present invention provides a method for preparing lead at low temperature by smelting alkaline hydroxide and galena in coordination and recycling the alkali. The method has the following beneficial effects:

[0020] The invention provides a method for preparing lead at low temperature by co-smelting alkaline hydroxide and galena and recycling alkali. The invention adopts the technology of preparing lead by co-smelting alkaline hydroxide and galena in vacuum, the direct recovery rate of lead is greater than 80%, the recovery rate of alkaline hydroxide is greater than 90%, the purity of lead is greater than 98%, the smelting temperature is lower than 700°C, metallic lead is prepared from galena at low temperature, based on the problems of large pollution in traditional lead metallurgy and low efficiency and high energy consumption in preparing lead by direct vacuum decomposition, this paper proposes a new technology of preparing metallic lead by co-smelting alkaline hydroxide and galena in vacuum and recycling alkali, elemental lead can be prepared at a temperature of 450-650°C, the alkaline hydroxide can be dissolved, crystallized and recycled, the method has simple process flow, low energy consumption, low preparation temperature, low carbon emission in vacuum decomposition process, clean and pollution-free, and broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process of the present invention;

[0022] Figure 2 It is a schematic diagram of the residue of the cooperative vacuum smelting of alkaline hydroxide and galena of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] like Figure 1-2 As shown, the embodiment of the present invention provides a method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation and recycling the alkali, and the process flow is as follows Figure 1 As shown, the specific steps are as follows: (1) 40g of dried galena with a lead sulfide content of 99% and 30g of sodium hydroxide powder with a purity of 99% are mixed evenly, and then pressed into blocks by a press to obtain a mixed block of galena and sodium hydroxide; (2) The above block is placed in a vacuum furnace, and after the pressure in the furnace is reduced to 10Pa, the temperature is increased at a heating rate of 8℃ / min, and after the displayed temperature reaches 600℃, it is kept warm for 1h; (3) After the insulation is completed, the displayed temperature is reduced to 30℃, the vacuum furnace is opened, and the mixed residue of metal lead and sodium hydroxide is taken out; (4) 1 liter of 60℃ hot water is used to dissolve the residue to obtain metal lead and sodium hydroxide aqueous solution; (5) The solid lead is filtered to obtain a pure sodium hydroxide solution; (6) The sodium hydroxide aqueous solution is placed on a resistance wire furnace for evaporation and crystallization to obtain solid sodium hydroxide. The lead direct yield is 85%, the sodium hydroxide direct yield is 98%, and the purity of the crude lead product is 99.23%.

[0026] Example 2

[0027] like Figure 1-2 As shown, the embodiment of the present invention provides a method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation and recycling the alkali, and the process flow is as follows Figure 1As shown, the specific steps are as follows: (1) Mix 30g of dried galena with a lead sulfide content of 95% and 20g of potassium hydroxide powder with a purity of 99% evenly, and use a press to press them into blocks to obtain mixed briquettes of galena and sodium hydroxide; (2) Put the above briquettes into a vacuum furnace, and after the pressure in the furnace drops to 5Pa, start heating at a heating rate of 10℃ / min, and keep warm for 30 minutes after the displayed temperature reaches 650℃; (3) After the insulation is completed, the displayed temperature drops to 30℃, open the vacuum furnace, and take out the mixed residue of metallic lead and sodium hydroxide; (4) Use 600ml of 90℃ hot water to dissolve the residue to obtain metallic lead and sodium hydroxide aqueous solution; (5) Filter the solid lead to obtain a pure sodium hydroxide solution; (6) Place the sodium hydroxide aqueous solution on a resistance wire furnace for evaporation and crystallization to obtain solid sodium hydroxide. The direct yield of lead is 90%, the direct yield of potassium hydroxide is 99%, the purity of the crude lead product is 95.62%, and the actual picture of the prepared lead is as follows Figure 2 shown.

[0028] Example 3

[0029] like Figure 1-2 As shown, the embodiment of the present invention provides a method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation and recycling the alkali, and the process flow is as follows Figure 1 As shown, the specific steps are as follows: (1) 100g of dried galena with a lead sulfide content of 90% and 60g of calcium hydroxide powder with a purity of 99% are mixed evenly, and then pressed into blocks by a press to obtain a mixed block of galena and sodium hydroxide; (2) The above block is placed in a vacuum furnace, and after the pressure in the furnace is reduced to 20Pa, the temperature is increased at a heating rate of 5℃ / min, and the temperature is kept for 1h after the displayed temperature reaches 650℃; (3) After the insulation is completed, the displayed temperature is reduced to 30℃, the vacuum furnace is opened, and the mixed residue of metal lead and sodium hydroxide is taken out; (4) 2 liters of 90℃ hot water are used to dissolve the residue to obtain metal lead and calcium hydroxide aqueous solution; (5) The solid lead is filtered to obtain a pure calcium hydroxide solution; (6) The calcium hydroxide aqueous solution is placed on a resistance wire furnace for evaporation and crystallization to obtain solid calcium hydroxide. The lead direct yield is 90%, the calcium hydroxide direct yield is 98%, and the purity of the crude lead product is 88.15%. Figure 2 The residue from vacuum smelting of alkaline hydroxide and galena (the bright metallic form is the prepared metallic lead).

[0030] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation and recycling the alkali, characterized in that: The following steps are involved: (1) uniformly mixing galena and alkaline hydroxide to obtain a mixture; (2) Pressing the mixture of step (1) into small pieces to ensure that it is not sucked away by the vacuum pump during the vacuum distillation process: (3) subjecting the mixture after briquetting in step (2) to vacuum distillation to obtain elemental lead and alkaline hydroxide residues, and condensing the decomposed S element above the distillation furnace; (4) leaching the residue from step (3) using high temperature distilled water; (5) separating the leaching solution from step (4) from lead to obtain metallic lead and an alkaline hydroxide aqueous solution; (6) The aqueous solution in step (5) is evaporated and crystallized to obtain an alkaline hydroxide which can be reused.

2. The method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation with each other and recycling alkali according to claim 1, characterized in that: The temperature rising procedure of the vacuum distillation comprises: placing the required materials in a graphite crucible, placing the graphite crucible in a vacuum furnace, first turning on the circulating cooling water, then turning on the vacuum pump, and starting to heat up after the vacuum degree drops to 5-30 Pa, with a heating rate of 5-10° C. / min; and keeping the temperature for 30 min to 60 min after the temperature rises to 450-700° C.

3. The method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation with each other and recycling alkali according to claim 1, characterized in that: The briquetting method in step (1) can be unidirectional pressing or cold isostatic pressing, as long as the mixture is in block shape. The hydroxide can be sodium hydroxide, potassium hydroxide or calcium hydroxide.

4. The method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation with each other and recycling alkali according to claim 1, characterized in that: The mixing ratio of galena and alkaline hydroxide in step (2) is 1:0.5-0.8 by mass.

5. The method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation with each other and recycling alkali according to claim 1, characterized in that: The vacuum distillation in step (3) is carried out at a temperature of 450 to 700° C., for a time of 30 to 60 minutes, and at a vacuum degree of 5 to 30 Pa.

6. The method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation with each other and recycling alkali according to claim 1, characterized in that: The temperature of the pure water used for leaching in step (4) is 50-100°C.

7. The method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation with each other and recycling alkali according to claim 1, characterized in that: The liquid-solid separation in step (5) can be carried out by filtering with a conventional suction bottle.

8. The method for preparing lead at low temperature by smelting alkaline hydroxide and galena in cooperation with each other and recycling alkali according to claim 1, characterized in that: The evaporation crystallization temperature in step (6) is 80-100° C. and the time is 120 min-300 min.

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