CN102251126A - Method for removing arsenic impurities from tin - Google Patents

Abstract

The invention relates to a method for removing arsenic impurities from tin. The method comprises the following steps of: adding an arsenic-containing tin alloy into a vacuum furnace, wherein arsenic elements in the tin are volatilized under the conditions that pressure in the furnace is in the range of 0.1-50Pa, the temperature in the furnace is between 1000 DEG C and 1500 DEG C, and the volatilization time of the arsenic-containing tin alloy is more than 0.25h; condensing the arsenic elements to obtain a metal arsenic; and separating the arsenic from the tin to obtain crude arsenic containing more than 90% of arsenic, wherein the removal rate of arsenic is greater than 90%. The invention provides a novel process for removing the arsenic from tin; the whole process is safe and controllable; and the method has the advantages of convenience for operation, high recovery rate of tin and arsenic, no need of adding chemical reagents and no pollution on the environment.

Description

A method for removing impurity arsenic from tin

technical field

The invention provides a method for treating arsenic-containing tin alloy by vacuum volatilization so as to realize high-efficiency separation of tin and arsenic, and belongs to the technical field of nonferrous metal pyrometallurgy.

technical background

The crude tin produced by reduction smelting of tin ore contains various impurities, and even the tin produced from tin-rich concentrate usually has a purity that cannot meet the requirements of users. Arsenic is a common toxic impurity in crude tin. The content of arsenic will directly affect the quality, performance and use of tin products. For example, tin foil for food packaging and tin for tin-plated sheets are required to contain less than 0.015% arsenic. Arsenic can also cause the appearance and plasticity of tin to deteriorate, and increase the viscosity of tin. The hardness of tin with arsenic content of 0.055% will increase to Brinell hardness 8.7, making the section of tin granular and increasing the brittleness of tin.

The composition of crude tin mainly depends on the composition of the tin concentrate, the pre-smelting treatment of the concentrate and the process flow of the treatment. At present, the composition of crude tin produced by various smelters fluctuates widely, but the content of arsenic in it is usually between 0.5% and 6%, and the content of crude tin in some metal production enterprises is higher.

At present, in the refining of crude tin, it usually needs to go through three processes of centrifugation to remove arsenic, condensate to remove arsenic, and aluminum to remove arsenic, in order to successively remove the arsenic in it, so that it can meet the arsenic content requirement of national standard tin ingots. This method requires high-temperature operation, a large amount of smoke and slag are produced during the treatment process, the labor intensity of the workers is high, and the working environment is harsh; moreover, aluminum slag containing AlAs is produced in the process of adding aluminum and removing arsenic, and AlAs encounters water, water vapor or humidity The air is prone to produce highly toxic AsH ₃ gas, which brings huge safety hazards to the environment. In addition, the centrifugal slag, smelting slag, carbon slag, and aluminum slag produced in the arsenic removal process will entrain a large amount of metallic tin, which directly affects the direct recovery rate of tin and reduces the economic benefits of the enterprise.

Contents of the invention

The purpose of the present invention is to provide a method for removing impurity arsenic in tin alloy by vacuum volatilization, so as to realize efficient separation of tin and arsenic and improve the performance of tin products.

The technical solution of the present invention is: send arsenic-containing tin alloy with arsenic content of 0.5-10% (mass ratio) into the vacuum furnace, control the temperature in the furnace to 1000-1500°C, and the pressure (vacuum degree in the vacuum furnace) to be 0.1 ~50Pa, the volatilization time is more than 0.25h, so that the impurity element arsenic volatilizes from the tin alloy melt, volatilizes into the condenser in a gaseous state, condenses to obtain metal arsenic and recovers it, and separates arsenic from tin. As in the recovered crude arsenic is more than 90%, and the removal rate of arsenic is more than 90%.

The invention provides a new treatment process for the arsenic-containing tin alloy, the whole process is safe and controllable, the operation is convenient, the recovery rate of tin and arsenic is high, no chemical reagents need to be added, and there is no pollution to the environment.

The invention adopts the vacuum volatilization process, after volatilizing the arsenic in the tin, it is collected in the condenser in the form of metal arsenic, which not only can effectively remove the arsenic in the tin, but also greatly improves the production environment, reduces the labor intensity of workers, and reduces the The processing capacity of the process of adding aluminum and removing arsenic is reduced, the amount of AlAs produced is reduced, and the amount of tin taken away by aluminum slag is greatly reduced, which has huge environmental protection benefits, economic benefits, and safety benefits for tin production enterprises.

The whole process of the invention is safe and controllable, easy to operate, no need to add any other additives, no three wastes are discharged, the volatilization process is carried out in a vacuum, has no impact on personnel and the environment, and has high universality for raw materials, tin with different arsenic components All alloys can be effectively treated, continuous industrial production can be realized, harmless removal of arsenic in the arsenic-containing tin alloy can be realized, and the invention has the characteristics of environmental friendliness, safety and practicability, and the like.

Description of drawings

Fig. 1 is process flow chart of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the content of the present invention is not limited to the stated scope.

Embodiment 1: Referring to Fig. 1, 10t crude tin raw material (Sn 81.54%; Pb 9.14%; Sb0.094%; Bi 0.184%; As3.30%) is sent into the vacuum furnace, and the pressure in the vacuum furnace is controlled to 0.5~ 6Pa range, 1500°C, vacuum volatilization for 1.5h, so that the impurity element arsenic volatilizes from the tin alloy melt, volatilizes into the condenser in a gaseous state, condenses to obtain crude arsenic with a content of 98%, and recovers, so that arsenic and tin are separated. The removal rate of arsenic is 95%.

Example 2: Referring to Figure 1, 10t of crude tin raw material (Sn 86.88%; Pb 6.16%; Sb 6.77%; Bi 0.23%; As 1.27%) is sent into a vacuum furnace, and the pressure in the furnace is controlled to 45~50Pa, The temperature is 1300°C, and continuous vacuum volatilization is carried out for 1 hour to volatilize the impurity element arsenic from the tin alloy melt and volatilize into the condenser in a gaseous state, condense to obtain crude arsenic with a content of 99%, and recover it to separate arsenic from tin. A total of 116.7kg of crude arsenic was collected, and the removal rate of arsenic was 91%.

Example 3: Referring to Figure 1, 20t of crude tin raw material (Sn84.68%; Pb 7.37%; Sb3.93%; Bi 2.61%; As 0.51%) is sent into a vacuum furnace, and the pressure in the furnace is 20~24Pa , 1200°C, continuous vacuum volatilization for 2 hours, so that the impurity element arsenic volatilizes from the tin alloy melt, volatilizes into the condenser in a gaseous state, condenses and recovers crude arsenic with a content of 96%, and separates arsenic from tin. A total of 95.6 kg of crude arsenic was collected, and the removal rate of arsenic was 90%.

Example 4: See Figure 1, put 15t of crude tin raw material (Sn88.41%; Pb 7.17%; Sb3.03%; Bi 0.57%; As 0.58%) into the vacuum furnace, the pressure in the furnace is 46~50Pa , 1000°C, continuous vacuum volatilization for 0.25h, so that the impurity element arsenic volatilizes from the tin alloy melt, volatilizes into the condenser in a gaseous state, condenses and recovers crude arsenic with a content of 98.8%, and separates arsenic from tin. A total of 81 kg of crude arsenic was collected, and the removal rate of arsenic was 92%.

Claims (3)

1. method of from tin, removing impurity arsenic, it is characterized in that: will contain the arsenic tin alloy and send in the vacuum oven, by temperature, vacuum tightness and volatilization time in the control stove, impurity elements arsenic is volatilized from molten tin alloy, being gaseous state evaporates in the condenser, condensation obtains metallic arsenic, and arsenic is separated with tin.

2. the method for removing impurity arsenic from tin according to claim 1, it is characterized in that: in the arsenic volatilization process, the vacuum oven internal pressure is 0.1 ~ 50Pa, and volatilization temperature is 1000 ~ 1500 ℃, and the volatilization time is more than the 0.25h.

3. the method for removing impurity arsenic from tin according to claim 1 and 2, it is characterized in that: described containing in the arsenic tin alloy raw material, arsenic content is 0.5 ~ 10%.

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