A method for recovering metallic tin by selectively oxidizing iron-tin alloy

Abstract

The present invention relates to the technical field of metal recycling, and particularly to a method for selectively recovering metallic tin from iron-tin alloy oxide. In view of the problem that in the roasting process of tin- and iron-containing materials, iron-tin alloy is easily formed, resulting in the hindrance of tin volatilization, the method for selectively recovering metallic tin from iron-tin alloy oxide provided by the present invention is to simultaneously introduce a sulfur-containing gas and a weakly oxidizing gas during the roasting process of tin- and iron-containing materials, so as to control the partial pressure of oxygen in the gas phase or the partial pressure of CO2 / CO in the gas phase, enabling the iron component in the iron-tin alloy to be selectively oxidized, while the tin component in the iron-tin alloy further reacts with the sulfur-containing gas and volatilizes into the soot, thus realizing the recovery of tin.

Description

Technical Field

[0001] The invention relates to the technical field of metal recovery and reuse, and in particular to a method for recovering metallic tin by selectively oxidizing an iron-tin alloy. Background Art

[0002] Tin is an important strategic resource in my country and is widely used in aerospace, electronic information, chemical industry and other fields. my country has rich tin reserves, but as high-quality tin resources are increasingly depleted, the grade of tin mining continues to decline and the mineral composition becomes more and more complex, the production technology requirements for tin are also getting higher and higher.

[0003] Tin ore often coexists with iron. The main occurrence forms of tin and iron are tin dioxide (SnO 2 ) and iron oxides. In the production process of tin, tin dioxide is preferentially reduced to metallic tin, which promotes the excessive reduction of iron oxides to iron, forming an iron-tin alloy (such as formulas (1) to (4)), in which the activity of the iron component in the formed iron-tin alloy (a [Fe] ) is smaller, the CO concentration required by equation (4) decreases (e.g. Figure 1 As shown). Therefore, the iron-tin alloy is inevitably produced, which limits the further volatilization and recovery of tin;

[0004] Fe 2 O 3 (s)+4CO(g)=3Fe 3 O 4 (s)+4CO 2 (g) Formula (1);

[0005] Fe 3 O 4 (s)+4CO(g)=3[Fe] Fe-Sn合金 +4CO 2 (g)(T<837K) Formula (2);

[0006] Fe 3 O 4 (s)+CO(g)=3FeO(s)+CO 2 (g)(T>837K) Formula (3);

[0007] FeO(s)+CO(g)=[Fe] Fe-Sn合金 +CO 2 (g) Formula (4).

[0008] Furthermore, as the content of iron in the iron-tin alloy increases, the iron activity increases (e.g. Figure 2 As shown), when a [Fe] =0.9, a [Sn]= 0.1, the Gibbs free mass of the sulfidation reaction of the iron component is more negative than that of the tin component, and the iron component undergoes sulfidation reaction before the tin component. As the activity of the iron component decreases, the activity of the tin component increases (a [Fe] =0.8, a [Sn] =0.2), although the sulfidation reaction trend of the iron component has decreased compared with the previous one, and the sulfidation reaction trend of the tin component has been enhanced, the iron component in the iron-tin alloy still undergoes sulfidation reaction before the tin component. In addition, under high iron activity, the FeS generated by the sulfidation reaction of the iron component will encapsulate [Sn] Fe-Sn合金 , making the volatilization of tin difficult. Therefore, the tin in the iron-tin alloy is difficult to be volatilized and recovered through a reducing sulfide atmosphere. Summary of the invention

[0009] The object of the present invention is to provide a method for recovering metallic tin by selectively oxidizing an iron-tin alloy. The recovery method can realize the recovery of metallic tin and has a high recovery rate.

[0010] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0011] The present invention provides a method for recovering metallic tin by selectively oxidizing an iron-tin alloy, comprising the following steps:

[0012] After heating the tin- and iron-containing materials, a mixed gas of sulfiding gas and weak oxidizing gas is introduced to carry out heat preservation roasting to obtain roasting slag and tin-containing smoke;

[0013] The oxidizing property of the weak oxidizing gas in the mixed gas is lower than the reducing property.

[0014] Preferably, the partial pressure ratio of the sulfiding gas and the weak oxidizing gas in the mixed gas is (0.01-0.20):1;

[0015] The flow rate of the mixed gas is 0.1-1.0 L / min.

[0016] Preferably, the sulfiding gas in the mixed gas includes H 2 S. SO 2 or COS.

[0017] Preferably, the weak oxidizing gas in the mixed gas is CO 2 and CO mixture, CO 2 , CO and N 2 The mixed gas, CO 2 , CO and O 2 The mixed gas, CO 2 ,CO,O 2 and N 2 The mixed gas, O 2 and CO mixed gas or O 2 , CO and N2 of mixed gas.

[0018] Preferably, the weak oxidizing gas is CO 2 and CO, the CO 2 CO in a mixture of CO and 2 The partial pressure ratio of CO is (0.80~0.40):(0.20~0.60).

[0019] Preferably, the weak oxidizing gas is O 2 and CO, the O 2 O in a mixture of CO 2 The partial pressure of CO is (0.03~0.15):(0.97~0.85).

[0020] Preferably, the material containing tin and iron is tin-containing iron ore, iron-containing tin medium ore, lean tin concentrate, iron-tin alloy or tin slag.

[0021] Preferably, the temperature of the heat preservation calcination is 1173-1573K, and the heat preservation time is 30-180min.

[0022] The present invention provides a method for selectively oxidizing an iron-tin alloy to recover metallic tin, comprising the following steps: heating a material containing tin and iron, introducing a mixed gas of a sulfiding gas and a weak oxidizing gas, and performing heat preservation roasting to obtain roasting slag and tin-containing smoke; the oxidizing property of the weak oxidizing gas in the mixed gas is lower than the reducing property. The weak oxidizing gas of the present invention can oxidize the iron in the material containing tin and iron into ferrous oxide, and reduce the activity of Fe atoms in the material containing tin and iron to ferrous oxide. [Fe] The activity of Sn atoms decreases. [Sn] Increase, promote the sulfidation reaction of tin, and finally realize the effective recovery of tin; in industrial practice, iron-tin materials are very easy to form iron-tin alloys during the roasting process, making it difficult for tin to be collected as smoke. If the iron in the alloy is oxidized, the activity of tin in the alloy will decrease. At this time, the sulfidation gas exists, and the tin will generate stannous sulfide, which will be collected in the smoke (such as Figure 2 shown). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the thermodynamic equilibrium diagram of the Fe-CO system;

[0024] Figure 2 The Gibbs free energy of the sulfidation reaction of iron and tin phases in the iron-tin alloy varies with the ratio of iron and tin phases at different temperatures;

[0025] Figure 3 At different temperatures, CO 2 and the effect of CO gas phase partial pressure on the Gibbs free energy of the reaction described in Equation 5;

[0026] Figure 4 The present invention is a schematic diagram of the process of recovering metallic tin. DETAILED DESCRIPTION

[0027] The present invention provides a method for recovering metallic tin by selectively oxidizing an iron-tin alloy, comprising the following steps:

[0028] After heating the tin- and iron-containing materials, a mixed gas of sulfiding gas and weak oxidizing gas is introduced to carry out heat preservation roasting to obtain roasting slag and tin-containing smoke;

[0029] The oxidizing property of the weak oxidizing gas in the mixed gas is lower than the reducing property.

[0030] In the present invention, the partial pressure ratio of the sulfiding gas and the weak oxidizing gas in the mixed gas is preferably (0.01-0.20):1, more preferably (0.05-0.15):1, and most preferably 0.1:1.

[0031] In the present invention, the sulfiding gas in the mixed gas preferably includes H 2 S. SO 2 or COS, more preferably SO 2 or COS.

[0032] In the present invention, the weak oxidizing gas in the mixed gas preferably includes CO 2 and CO mixture (CO 2 +CO), CO 2 , CO and N 2 Mixed gas (CO 2 +CO+N 2 ), CO 2 , CO and O 2 Mixed gas (CO 2 +CO+O 2 ), CO 2 ,CO,O 2 and N 2 Mixed gas (CO 2 +CO+O 2 +N 2 ), O 2 and CO mixture (O 2 +CO), O 2 , CO and N 2 Mixed gas (O 2 +CO+N 2 ) or CO 2 , CO and N 2 Mixed gas (CO 2 +CO+N 2 ), most preferably including CO2 and CO mixed gas or O 2 and CO. In the present invention, the CO 2 CO in a mixture of CO and 2 The partial pressure ratio of O and CO is preferably (0.80-0.40):(0.20-0.60), more preferably 0.55:0.45; 2 O in a mixture of CO 2 The partial pressure ratio of CO is preferably (0.03-0.15):(0.97-0.85), more preferably (0.06-0.10):(0.94-0.90), and most preferably 0.08:0.92; the CO 2 , CO and N 2 N in the mixed gas 2 , CO 2 The partial pressure ratio of CO and CO is preferably 1:0.6:0.4 or 1:0.4:0.6.

[0033] In the present invention, the tin- and iron-containing materials are tin-containing iron ore, iron-containing tin medium ore, lean tin concentrate, iron-tin alloy or tin slag. In an embodiment of the present invention, the tin- and iron-containing materials are specifically lean tin concentrate (Fe24.03wt.%, Sn10.72wt.%), iron-tin alloy (Fe79.66wt.%, Sn19.31wt.%), iron-containing tin medium ore (Fe49.06wt.%, Sn4.12wt.%) or tin-containing iron ore (Fe64.85wt.%, Sn0.56wt.%). In the present invention, the tin- and iron-containing materials are preferably pretreated, and the pretreatment is preferably grinding; the present invention does not have any special limitation on the grinding process, and the process well known to those skilled in the art can be used.

[0034] In the present invention, the temperature of the heat preservation calcination is preferably 1173-1573K, more preferably 1200-1500K, most preferably 1300-1400K; the heat preservation time is preferably 30-180min, more preferably 50-150min, most preferably 60-120min.

[0035] Taking the case where the oxidizing gas includes carbon dioxide and the material containing tin and iron is an iron-tin alloy as an example, during the roasting process, the oxidation reaction occurring is as shown in Formula 5:

[0036] [Fe] Fe-Sn合金 +CO 2 =FeO+CO+[Sn] Formula 5;

[0037] Figure 3 is the effect of the partial pressure of carbon monoxide and carbon dioxide on the Gibbs free energy of the reaction shown in equation 5 at different temperatures, Figure 3It can be seen that as the partial pressure of carbon dioxide increases, the partial pressure of carbon monoxide decreases, and the Gibbs free energy shown in Equation 5 tends to be negative, indicating that by controlling the partial pressure of gas phase oxygen or CO 2 / CO partial pressure ratio, the iron component in the iron-tin alloy can be selectively oxidized to make the a [Fe] Decline, a [Sn] Increase, promote the sulfidation reaction of tin.

[0038] The method for recovering metallic tin provided by the present invention is described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0039] Example 1

[0040] Treatment object: tin-containing iron ore (Fe64.85wt.%, Sn0.56wt.%);

[0041] like Figure 4 As shown, the tin-containing iron ore is ground and heated to a roasting temperature of 1423 K, and then COS and N are introduced. 2 +CO+CO 2 The mixed gas has a flow rate of 0.6 L / min, and the COS and N 2 +CO+CO 2 The partial pressure ratio is 0.15:1; the N 2 +CO+CO 2 Medium 2 , CO and CO 2 The partial pressure ratio is 1:0.6:0.4; the temperature is kept for 90 minutes to obtain roasted slag and tin-containing smoke;

[0042] Chemical analysis showed that the tin content in the calcined slag was 0.024 wt.%, and the calculated tin recovery rate was 96.4%.

[0043] Comparative Example 1

[0044] Referring to Example 1, the difference is that COS and N 2 +CO+CO 2 The mixed gas is replaced by COS+N 2 +CO(COS+N 2 + COS, N 2 The partial pressure ratio of CO and CO is 0.3:1:1); the tin content in the obtained roasted slag is 0.19wt.%, and the tin recovery rate is 70.8%;

[0045] By comparing Example 1 with Comparative Example 1, it can be seen that the introduction of oxidizing gas can further volatilize and recover tin.

[0046] Example 2

[0047] Treatment object: iron-containing tin ore (Fe49.06wt.%, Sn4.12wt.%);

[0048] like Figure 4 As shown in the figure, the iron-containing tin ore is ground and heated to a roasting temperature of 1473K, and then COS and CO+CO are introduced. 2 The mixed gas has a flow rate of 0.6 L / min, and the COS and CO+CO 2 The partial pressure ratio of CO+CO is 0.1:1; 2 Medium CO 2 The partial pressure ratio of CO is 0.8:0.2; the temperature is kept for 120 minutes to obtain roasted slag and tin-containing smoke;

[0049] The tin content in the calcined slag is 0.084wt.%, and the recovery rate of tin is 98.3%.

[0050] Comparative Example 2

[0051] Referring to Example 2, the difference is that COS and CO+CO 2 The mixed gas was replaced by COS+CO (the partial pressure ratio of COS to CO in the COS+CO was 0.1:1); the tin content in the obtained roasted slag was 1.63wt.%, and the tin recovery rate was 66.0%.

[0052] Example 3

[0053] Processing object: lean tin concentrate (Fe24.03wt.%, Sn10.72wt.%);

[0054] like Figure 4 As shown, the depleted tin concentrate is ground and heated to a roasting temperature of 1423 K, and then SO 2 and O 2 +CO mixed gas, the flow rate of the mixed gas is 0.6L / min, the SO 2 and O 2 The partial pressure ratio of +CO is 0.12:1; the O 2 +CO in O 2 The partial pressure ratio of CO is 0.06:0.94; the temperature is kept for 180 minutes to obtain roasted slag and tin-containing smoke;

[0055] The tin content in the calcined slag is 0.22wt.%, and the recovery rate of tin is 98.4%.

[0056] Comparative Example 3

[0057] Referring to Example 3, the difference is that SO 2 and O 2 +CO mixed gas replaced by SO2 +CO(the SO 2 +SO in CO 2 The partial pressure ratio of CO to CO is 0.12:1); the tin content in the obtained roasted slag is 2.74wt.%, and the tin recovery rate is 78.3%.

[0058] Example 4

[0059] Processing object: iron-tin alloy (Fe79.66wt.%, Sn19.31wt.%);

[0060] like Figure 4 As shown, the iron-tin alloy is ground and heated to a roasting temperature of 1523 K, and then SO 2 and N 2 +CO 2 +CO mixed gas, the flow rate of the mixed gas is 0.8L / min, the SO 2 and N 2 +CO 2 The partial pressure ratio of +CO is 0.15:1; the N 2 +CO 2 +CO in N 2 , CO 2 The partial pressure ratio of CO is 1:0.6:0.4; the temperature is kept for 120 minutes to obtain roasted slag and tin-containing smoke;

[0061] The tin content in the calcined slag is 0.98wt.%, and the recovery rate of tin is 95.9%.

[0062] Comparative Example 4

[0063] Referring to Example 4, the difference is that SO 2 and N 2 +CO 2 +CO mixed gas replaced by SO 2 +N 2 +CO(the SO 2 +N 2 +SO in CO 2 、N 2 The partial pressure ratio of CO and CO is 0.3:1:1); the tin content in the obtained roasted slag is 3.78wt.%, and the tin recovery rate is 83.6%.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for selectively oxidizing an iron-tin alloy to recover metallic tin, characterized in that: The following steps are involved: After heating the tin- and iron-containing materials, a mixed gas of sulfiding gas and weak oxidizing gas is introduced to carry out heat preservation roasting to obtain roasting slag and tin-containing smoke; The oxidizing property of the weak oxidizing gas in the mixed gas is less than the reducing property; The weak oxidizing gas in the mixed gas is a mixed gas of CO2 and CO or a mixed gas of O2 and CO; The partial pressure ratio of CO2 and CO in the mixed gas of CO2 and CO is (0.80~0.40): (0.20~0.60); The partial pressure ratio of O2 and CO in the mixed gas of O2 and CO is (0.03~0.15): (0.97~0.85); The partial pressure ratio of the sulfide gas and the weak oxidizing gas in the mixed gas is (0.01-0.20):1; The sulfide gas in the mixed gas includes H2S, SO2 or COS.

2. The method according to claim 1, characterized in that The flow rate of the mixed gas is 0.1~1.0L / min.

3. The method according to claim 1, characterized in that The material containing tin and iron is tin-containing iron ore, iron-containing tin medium ore, poor tin concentrate, iron-tin alloy or tin slag.

4. The method according to claim 1, characterized in that The temperature of the heat preservation calcination is 1173-1573K, and the heat preservation time is 30-180min.

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