METHOD FOR HIGH-PURITY TIN RECOVERY AND HYDROGEN PRODUCTION USING METHANE REDUCTION

Abstract

The present invention relates to a method of using a methane gas to recover tin with high purity and to produce hydrogen at once, and the method uses the methane reduction technique that combines the two different processes of tin recovery and hydrogen production, thereby recovering tin with high purity from a methane gas and a tin oxide according to the methane reduction technique stably without emission of environmental pollutants, such as carbon dioxide, sulfur dioxide, nitrogen oxide, etc., and also producing hydrogen available as a new energy resource. Further, the present invention enables the recycling of waste materials containing tin oxides generated in all kinds of industries to prevent environmental contaminations and to offer solutions to the stable recovery of expensive tin with high purity and the dramatic reduction of hydrogen production costs at once, increasing economical efficiency and thus contributing to the efficient use of resources.

Claims

1. A method for recovering tin with high purity and producing hydrogen using methane gas, the method comprising: (S1) adding a methane gas (CH.sub.4) into a reaction furnace containing a tin oxide; (S2) activating a reduction reaction of a mixture of the tin oxide and the methane gas of step (S1); and (S3) collecting tin and hydrogen gas produced after the reduction reaction of the step (S2).

2. The method as claimed in claim 1, wherein the tin oxide includes an oxidized tin, a salt of tin oxide, or a waste containing the oxidized tin and the salt of tin oxide.

3. The method as claimed in claim 1, wherein a mixing molar ratio of the tin oxide and the methane gas is 1:1 to 6.

4. The method as claimed in claim 1, wherein the reduction reaction of the step (S2) is performed at 600 to 1,500 C.

5. The method as claimed in claim 1, wherein the methane gas contains 80 to 99% methane.

6. The method as claimed in claim 2, wherein the methane gas contains 80 to 99% methane.

7. The method as claimed in claim 3, wherein the methane gas contains 80 to 99% methane.

8. The method as claimed in claim 4, wherein the methane gas contains 80 to 99% methane.

Description

BRIEF DESCRIPTIONS OF DRAWINGS

[0026] FIG. 1 is an illustration showing the chemical reaction in the tin recovery and hydrogen production technique of the present invention combining the reforming reaction of a methane gas and the reduction reaction of a tin oxide together.

[0027] FIG. 2 is a schematic illustration of the method for recovering tin with high purity and producing hydrogen using the methane reduction technique according to one embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

[0028] Hereinafter, the present invention will be described in detail with reference to the following examples, which are given for the illustrations of the present invention only and not construed to limit the scope of the present invention. The examples of the present invention are subjected to various changes and modification and provided for those skilled in the art to understand the prevent invention more completely.

Example 1: High-Purity Tin Recovery and Hydrogen Production Using Methane Reduction

[0029] A lump of tin oxide was pulverized into powder. 25 g of the tin oxide powder was put in an alumina boat and placed in a quartz tube of a reduction furnace, as illustrated in FIG. 2. Both ends of the quartz tube were sealed with fixtures, the one capable of gas injection and the other gas collection. After the sealing, the temperature of the reduction furnace was raised up to 1,000 C. and a methane gas was injected from the one end of the quartz tube. In this process, the methane gas was controlled with a mass flow controller (MFC). In the Example 1, the methane gas was injected into the reduction furnace at a rate of 250 sccm (standard cubic centimeter per minute). Under the injection conditions of the methane gas at 250 sccm, the mixing ratio (molar ratio) of tin oxide (SnO.sub.2) and methane (CH.sub.4) amounts to 1:37. A gas-capturing was attached to the opposite side to the methane-injecting portion in the quartz tube in order to capture the potential emissions of carbon monoxide and carbon dioxide and the unreacted methane gas as well as the hydrogen gas produced from the reaction. The tin reduction reaction using the methane gas took place for one hour. After the completion of the reaction, the remaining methane gas in the reduction furnace was discharged out of the reduction furnace and combusted.

Test Example 1: Qualitative Analysis on Reduced Tin

[0030] The reduced tin of Example 1 was subjected to a qualitative analysis according to the KS D 1720. The results are presented in Table 1.

TABLE-US-00001 TABLE 1 Element Composition (%) Test method Sn 99.34 KS D 1720: 1994 Pb Not detected KS D 1720: 1994 Sb 0.13 KS D 1720: 1994 As 0.001 KS D 1720: 1994 Cu 0.49 KS D 1720: 1994 Fe 0.04 KS D 1720: 1994

[0031] As can be seen from Table 1, the elements to detect were Sn, Pb, Sb, As, Cu, and Fe. The reduced tin contained 99.34% Sn and, as impurities, 0.13% Sb, 0.001% As, 0.49% Cu, and 0.04% Fe. Namely, it was possible to recover tin with high purity of 99.34% through the reduction of the tin oxide using the methane gas.

Test Example 2: Qualitative and Concentration Analysis on Emission Gas

[0032] The emission gas captured by the gas-sampling bag in Example 1 was analyzed in regards to composition and concentration by way of the gas chromatograph (GC-TCD) and the mass spectrometer (QMS). The results are presented in Table 2.

TABLE-US-00002 TABLE 2 Component Concentration (%) H.sub.2 83.5 CO 14.0 CH.sub.4 1.7 CO.sub.2 0.4

[0033] As can be seen from Table 2, the emission gas was composed of 83.9% hydrogen, 14.0% carbon monoxide, 1.7% methane, and 0.4% carbon dioxide. Namely, it was possible to obtain a hydrogen-mixed gas containing hydrogen at concentration of 83.9% from the reduction reaction of a tin oxide using methane.

Comparative Example 1: High-Purity Tin Recovery and Hydrogen Production Using Excess Methane

[0034] The procedures were performed in the same manner as described in Example 1 to reduce the tin oxide powder, excepting that the methane gas was injected at 416 sccm so that the mixing ratio (molar ratio) of tin oxide (SnO.sub.2) to methane (CH.sub.4) was 1:6.1.

Test Example 3: Qualitative Analysis on Reduced Tin

[0035] The reduced tin of Comparative Example 1 was subjected to a qualitative analysis according to the KS D 1720. The results are presented in Table 3.

TABLE-US-00003 TABLE 3 Element Composition (%) Test method Sn 99.88 KS D 1720: 1994 Pb 0.013 KS D 1720: 1994 Sb Not detected KS D 1720: 1994 As Not detected KS D 1720: 1994 Cu 0.11 KS D 1720: 1994 Fe Not detected KS D 1720: 1994

[0036] As can be seen from Table 3, the elements to detect were Sn, Pb, Sb, As, Cu, and Fe. The reduced tin contained 99.88% Sn and, as impurities, 0.013% Pb and 0.011% Cu. Namely, it was possible to recover tin with high purity of 99.88% through the reduction of the tin oxide using the methane gas.

Test Example 4: Qualitative and Concentration Analysis on Emission Gas

[0037] The emission gas captured by the gas-sampling bag in Comparative Example 1 was analyzed in regards to composition and concentration by way of the gas chromatograph (GC-TCD) and the mass spectrometer (QMS). The results are presented in Table 4.

TABLE-US-00004 TABLE 4 Component Concentration (%) H.sub.2 43.8 CO 6.7 CH.sub.4 0.2 CO.sub.2 46.4

[0038] As can be seen from Table 4, the emission gas was composed of 43.8% hydrogen, 6.7% carbon monoxide, 0.2% methane, and 46.4% carbon dioxide. When the injected amount of the methane gas was increased to 416 sccm so that the mixing ratio (molar ratio) of tin oxide (SnO.sub.2) to methane (CH.sub.4) was 1:6.1, it reduced the hydrogen concentration and increased the methane concentration in the emission gas. This result comes down to the supply of excess methane, which contributes to an increase in the amount of methane gas discharged while remaining unreacted rather than participating in the reduction of the tin oxide.