KR100866473B1 - Zinc reproduction method of zinc dross - Google Patents

Abstract

A Zn reproduce method of the Zn dross is provided to reproduce the zinc of the high purity of the property which desires since effectively removing impurity remaining behind among the molten metal by using a sublimate material or 1iquid nitrogen gas. A Zn reproduce method of the Zn dross performing the first process of exhausting and removing the impurity in which dissolves the Zn dross and in which agitates and which rises to the top of the molten metal, the first process of injecting aluminum in the molten metal in which the first process is performed and agitating and exhausting and removing the impurity which rises to the upper part of molten metal and the second process of exhausting and removing the impurity in which injects the sublimate material for promoting the inter metallic compound generation of impurity less than the triple point temperature 500°C in the molten metal in which the second process is performed and in which agitates and in which rises among the molten metal or which is precipitated.

Description

Zinc Reproduction Method of Zinc Dross

The present invention relates to a zinc regeneration method of zinc dross, and more particularly, to a zinc regeneration method of zinc dross that regenerates zinc by removing impurities by forming an intermetallic compound using aluminum and a sublimable material. .

The galvanizing process is a process of plating zinc by passing a strip of a heating furnace through a plating bath. The zinc is plated on the surface of the steel sheet by passing the steel sheet in a state in which the plating bath always contains a predetermined amount of molten zinc. .

In this zinc plating process, the molten zinc adheres to the surface of the plated body and is formed as a by-product. The by-product is precipitated under the plating bath or floated to the top due to the specific gravity difference with zinc. Solidifies.

When the zinc dross adheres to the surface of the steel sheet, the appearance of the product is damaged. Therefore, the operation of periodically removing the zinc dross floating on the surface of the molten zinc of the plating bath is performed.

However, since a large amount of pure zinc is discarded in the process of removing the zinc dross, a method for recycling zinc contained in the zinc dross generated as a by-product to pure zinc has been studied.

In general, zinc dross contains impurities such as iron (Fe), aluminum (Al), and lead (Pb) that are higher than specified values drawn from a plated body or a molten zinc container in the galvanizing process. Zinc can be recycled.

In order to remove impurities in zinc dross, first, zinc dross is re-dissolved and separated into zinc oxide (ZnO) and pure zinc (Zn) by flux treatment. Second, the difference in specific gravity of the solution due to temperature difference is used. The third method is to remove impurities by removing specific impurities by heating the zinc dross described in Korean Patent Registration No. 324707, and the specific gravity difference.

However, the first method is not preferable in that the flux causes environmental problems such as gas formation, and the second method is difficult to expect effective separation of pure zinc because it is difficult to separate layers from pure zinc and impurities. Floating and precipitated impurities are removed using only the specific gravity difference between the molten zinc and the impurities due to the melt heating of the dross, there is a problem in that the efficiency of fine particles and flotation and precipitation separation is limited.

Therefore, there is an urgent need for a technique for recovering zinc contained in zinc dross in a more efficient and economical manner.

The present invention is to solve the conventional problems as described above, the object of the present invention is to efficiently separate the impurities contained in the zinc dross as a by-product generated during the zinc plating process to enable high purity zinc to be recovered It is to provide a method for regenerating zinc of dross.

According to a feature of the present invention for achieving the above object, the present invention comprises: a first step of dissolving and stirring zinc dross to discharge and remove impurities that float to the top of the molten metal; A second step of discharging and removing impurities floating in the upper part of the molten metal by stirring and adding aluminum to the molten metal in which the first step is performed; A third step of discharging and removing impurities impregnated or precipitated in the molten metal by adding and stirring a sublimable substance having a triple point temperature of 500 ° C. or less to promote the generation of intermetallic compounds of impurities in the molten metal in which the second step is performed; do.

The second step and the third step are carried out simultaneously.

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The sublimable material is any one of NH ₄ Cl, NH ₄ Br ₂ , NH ₄ I, NH ₂ SO ₄ , NH ₄ F and dry ice.

The sublimable material is contained in the range of 0.15 to 0.2% by weight.

After the third step, aluminum is re-injected so that the aluminum content is 0.45 to 0.50% by weight.

After the third step, the step of re-injecting aluminum into the molten metal further includes a step of controlling the iron content in the molten metal.

A first step of dissolving and stirring the zinc dross to discharge and remove the impurities floating on the upper portion of the molten metal; A second step of discharging and removing impurities floating in the upper part of the molten metal by stirring and adding aluminum to the molten metal in which the first step is performed; And a third step of injecting and stirring the liquefied nitrogen gas for promoting the generation of the intermetallic compound of the impurity into the molten metal in which the second step is performed to discharge and remove the impurities floating or precipitated in the molten metal.

The second step and the third step are carried out simultaneously.

The liquefied nitrogen gas is contained in the range of 0.15 to 0.2% by weight.

After the third step, aluminum is re-injected so that the aluminum content is 0.45 to 0.50% by weight.

After the third step, the step of re-injecting aluminum into the molten metal further includes a step of controlling the iron content in the molten metal.

In the present invention, in regenerating zinc by reprocessing zinc dross generated during the galvanizing process, unlike the prior art, a sublimable material or a liquid nitrogen gas having a triple point temperature of 500 ° C. or less is used. These sublimable substances and liquefied nitrogen gas increase the unsoluble impurities (Fe, Al, Pb) through local cooling of the molten metal, and impart a molten metal stirring function to promote the formation of intermetallic compounds, thereby remaining Fe, Al, Impurities such as Pb can be effectively separated and removed.

In addition, the present invention can adjust the Al content in the treated molten metal by injecting Al in the molten metal so as to meet the demand level of the demand. Therefore, the present invention has an effect that can be effectively applied to each type of regeneration process for regenerating zinc.

Hereinafter, a preferred embodiment of the zinc regeneration method of zinc dross according to the present invention will be described in detail with reference to the accompanying drawings.

The present invention has a problem that the method of separating impurities contained in the zinc dross by the conventional simple specific gravity difference is limited to the floating and sedimentation of fine impurity particles, and has been proposed to improve the problem.

As a result, it was confirmed that when sublimable substance such as ammonium chloride (NH ₄ Cl) having vaporization capacity was added to the regeneration process of zinc dross, the substance evaporated by causing endothermic reaction in the molten metal.

Ammonium chloride causes an endothermic reaction and is vaporized as follows.

NH ₄ Cl → HCl + NH ₃

When the sublimable substance is added to the molten metal, the molten metal is locally cooled to promote a flat reaction of impurities such as iron, aluminum, and lead. Unbiased reactions are reactions that simultaneously produce separate liquid and solid solutions in a solution.

When the flat reaction is promoted in the molten metal, the molten metal is locally unbalanced and the amount of impurities (Fe, Al, Pb) in the non-employed state is increased. The increase of impurities in the non-employed state in the molten metal promotes the generation of the intermetallic compound, and the vaporization gas formed by the decomposition has the effect of promoting the stirring of the molten metal.

Here, an intermetallic compound is a compound having two or more metal elements combined in a simple atomic ratio when the affinity between the metal and the metal is large to make an independent compound having different properties from that of the component metal. Is displayed.

Based on the above-mentioned fact, the zinc regeneration method of zinc dross of the present invention dissolves zinc dross and stirs, and adds an appropriate amount of aluminum and a separate sublimable material to remove the floating and precipitated impurities in the molten metal. It is characterized by regenerating zinc.

In general, zinc dross collected in the galvanizing process includes iron (Fe): 1.0 to 2.0%, aluminum (Al): 1.0 to 2.5%, lead (Pb): 0.08 to 0.012%, and other unavoidable impurities. , The remaining zinc (Zn). And the melting temperature of zinc dross is about 550 ~ 600 ℃. This corresponds to a temperature at which zinc evaporation can be prevented while the fluidity of zinc dross is secured.

In order to dissolve zinc dross having such a composition and effectively regenerate zinc, removal of iron in the molten metal is preferentially performed. Iron is mostly removed by the stirring of the molten metal and the addition of aluminum, but it is not easy to separate and remove it in the solid solution in zinc.

However, according to the Zn-Fe binary diagram, it can be seen that if the molten zinc is kept at the lowest possible temperature in the allowable range, the content of unsolubilized iron in the molten zinc increases. In addition, since the unemployed iron has a greater affinity for aluminum than zinc, it reacts with aluminum present in the molten metal to form a Fe-Al intermetallic compound.

In consideration of this, a sublimable substance such as ammonium chloride (NH ₄ Cl) is added to the molten metal during the dissolution of zinc dross. Sublimable material is added to the molten metal to locally cool the molten metal. This local cooling promotes the partial reaction of Zn, Fe, Al, Pb and other impurities.

As a result, Zn, Fe, Al, Pb, and other impurities in the phase equilibrium in the molten state become a local non-equilibrium state, and the amount of Fe, Al, Pb, and other impurities that are not employed in the molten metal increases. These unemployed impurities are combined with impurities having a high affinity, thereby promoting the generation of intermetallic compounds.

The intermetallic compound is mainly composed of Fe-Al-based intermetallic compounds, but may also include Fe-Pb-based and other Fe-other impurities. The Fe-Al-based intermetallic compound may form a FeAl ₃ or FeAl ₂ compound, which has a specific gravity smaller than that of zinc to rise above the molten metal. Then, the compound floating in the upper part of the melt, that is, impurities may be removed.

The sublimable material preferably has a triple point temperature of 500 ° C. or less so as to locally cool the molten metal. As the sublimable material, various kinds of materials satisfying the triple point temperature may be used, but preferably, NH ₄ Cl, NH ₄ Br ₂ , NH ₄ I, NH ₂ SO ₄ , NH ₄ F and dry ice may be selected. Can be. Here, the triple point temperature is a temperature at which gas, liquid, and solid coexist.

Based on the above facts, the present invention comprises a first step of heating and melting zinc dross in a reflection furnace and then stirring to discharge and remove impurities floating on the upper part of the molten metal;

A second step of introducing and stirring Al into the molten metal to which the first step is performed to discharge and remove residual impurities floating on the upper portion of the molten metal;

After the second step, a third step of discharging and removing the fine impurities that float or precipitate in the molten metal by adding a sublimable substance having a triple point temperature of 500 ° C. or less to the molten metal from which residual impurities are removed after the second step; Play it.

The first step is a step of removing impurities by a simple specific gravity difference.

Zinc dross is collected in the general galvanizing process and is usually contained in weight% of iron (Fe): 1.0 to 2.0%, aluminum (Al): 1.0 to 2.5%, lead (Pb): 0.08 to 0.012%, and other unavoidable impurities. It consists of, and consists of the remaining zinc (Zn). The melting temperature of the zinc dross is a temperature range of approximately 550 ~ 600 ℃, the zinc dross is not necessarily limited to the actual composition of the collected zinc dross. Melting uses a reflecting furnace, but is not necessarily limited thereto, and a crucible furnace may also be used.

Stirring carries out mechanical stirring using a stirrer or the like. Agitation promotes the formation of the intermetallic compound by melting point and decomposition temperature difference of each component, whereby the intermetallic compound having a lower specific gravity than the zinc is floated on the upper portion of the molten metal. The intermetallic compound may include an Al-Fe-based intermetallic compound mainly or other impurities contained in zinc dross, and a part of the intermetallic compound may be precipitated under the molten metal.

The second step is a step of removing impurities not yet removed in the first step.

Al should be 0.45 ~ 0.50% of Al content by weight in the molten metal. Here, the content control of Al is made through the component analysis of the process step. Al forms Fe as an Al-Fe-based intermetallic compound, which is not removed in the first step, and rises to the top of the molten metal. And the impurity which floated to the upper part of a molten metal in a 2nd process is discharged | emitted and removed. Stirring performs mechanical stirring similarly to a 1st process.

The third step is to remove iron and fine impurities dissolved in zinc.

The sublimable material is added to the molten metal to promote the entire molten metal stirring to effectively float the impurities. As the sublimable material, one material selected from NH ₄ Cl, NH ₄ Br ₂ , NH ₄ I, NH ₂ SO ₄ , NH ₄ F and dry ice having a triple point temperature of 500 ° C. or less may be used. More preferably NH ₄ Cl can be used. The sublimable material is introduced in the solid state.

At this time, the sublimable material is added in the range of 0.15 ~ 0.2% by weight. This is because if the concentration is less than 0.15%, the local cooling effect of the melt is insufficient, and if it exceeds 0.2%, the melt is supercooled and there is no impurity separation effect.

In another embodiment, the liquid nitrogen gas may be blown into the molten metal instead of the sublimable material in the third process. Liquefied nitrogen gas can be used in place of sublimable materials in that it has a local cooling effect with inert low temperature gas.

At this time, the liquefied nitrogen gas is added to the weight% 0.15 ~ 0.2% range. Like the sublimable material, the amount of liquefied nitrogen gas is less than 0.15%, and the local cooling effect of the molten metal is insufficient, and when 0.2% is exceeded, the molten nitrogen is supercooled, and it is difficult to expect an impurity separation effect.

For reference, various kinds of materials may be employed instead of the above-described sublimable material and liquefied nitrogen gas, which can exert a local cooling effect.

Sublimable material and liquefied nitrogen gas locally cool the melt to make the iron and other impurities dissolved in zinc non-equilibrium. Stirring uses mechanical stirring as in the first and second processes, but in the third process, the stirring operation of the molten gas by the vaporization gas generated by the injection of the molten sublimable substance is also generated. Such agitation promotes generation of Fe-Al-based intermetallic compounds such as FeAl ₂ and FeAl ₃ in the molten metal.

The Fe-Al-based intermetallic compound thus generated has a specific gravity lower than that of zinc, so that it floats and separates as impurities in the upper portion of the molten metal, and impurities such as Pb contained in the molten metal are precipitated in the lower portion of the molten metal due to the higher specific gravity.

At this time, the Fe-Al-based intermetallic compound, which is an impurity which has floated to the upper part of the molten metal, is discharged and removed by a method of removing it, and Pb, etc., deposited at the lower part of the molten metal is discharged and removed through the lower tap of the reflection furnace.

In another embodiment, the second process and the third process may be performed simultaneously. More specifically, Al and a sublimable substance having a triple point temperature of 500 ° C. or less may be simultaneously added and stirred to the molten metal to which the first step is performed to remove and remove floating and precipitated impurities in the molten metal.

Such simultaneous input realizes the effect of separating and removing impurities by Al injection and the effect of separating and removing fine impurities due to the addition of sublimable material. Even in such a co-injection process, Al and the sublimable substance are controlled so that the Al content of the molten metal is 0.45 to 0.50% by weight in the molten metal. Of course, Al content control is achieved through the component analysis of the process step. In addition, the impurities floating in the upper portion of the molten metal and the Pb deposited in the lower portion are discharged and removed in the same manner as in the above-described embodiment.

In another embodiment, the liquid nitrogen may be blown into the molten metal instead of the sublimable material at the same time as Al is added to the molten metal subjected to the first step. This also realizes the effect of separating and removing impurities by the addition of Al and the effect of separating and removing fine impurities due to the addition of sublimable materials.

In addition, in the present invention, in addition to the third step, when excessive impurities in the molten metal, in particular, Fe is excessively added, Al can be added again to control the Fe content.

On the other hand, the molten metal from which impurities are removed may be melted and put into a molding mold and molded by cooling to be commercialized. At this time, the tapping temperature of the molten metal is preferably maintained in the range of approximately 450 ~ 500 ℃ in consideration of the fluidity of the molten metal.

Hereinafter, a zinc regeneration method of zinc dross to help the understanding of the present invention will be described in detail through one embodiment.

(Example 1)

By weight%, iron (Fe): 1.0 to 2.0%, aluminum (Al): 1.0 to 2.5%, lead (Pb): 0.08 to 0.012%, zinc plating and zinc application process containing Cd, Sn, and residual zinc In each of the zinc dross generated as a by-product.

Then, the zinc dross was sequentially introduced into a large-capacity reflection furnace (20 tons / Charge), and then dissolved in a 550-600 ° C., and stirred using a stirrer to contain Al-Fe-Zn-based intermetallic compound as a main component. Impurities were removed after separation into the top of the melt. After removing the impurities, the component content of the molten metal was measured, and the results are shown in Table 1 below.

division Composition (wt%) Al Fe Pb CD Sn Zn Example 1 0.321 0.0152 0.007 0.0001 0.00001 residual Example 2 0.298 0.0136 0.006 0.0001 0.00001 residual Example 3 0.285 0.0178 0.007 0.0001 0.00001 residual Example 4 0.301 0.0166 0.007 0.0001 0.00001 residual Example 5 0.331 0.0145 0.006 0.0001 0.00001 residual

Next, Al was added to the molten metal treated as described above and stirred to float and remove impurities mainly containing Al-Fe-based intermetallic compounds to the upper portion of the molten metal. At this time, Al was controlled to be added so that the Al content in the molten metal was 0.45 to 0.50%. And the component content in the molten metal was measured and the results are shown in Table 2.

division Composition (wt%) Al Fe Pb CD Sn Zn Example 1 0.257 0.0113 0.006 0.0001 0.00001 residual Example 2 0.232 0.0109 0.005 0.0001 0.00001 residual Example 3 0.244 0.0092 0.006 0.0001 0.00001 residual Example 4 0.229 0.0117 0.007 0.0001 0.00001 residual Example 5 0.238 0.0098 0.006 0.0001 0.00001 residual

Then, after adding ammonium chloride (NH4Cl), which can cause local subcooling of the molten metal, by stirring with a stirrer, the impurities were suspended and discharged to the upper portion of the molten metal. First was discharged through the tap. In addition, the components of the melt thus processed were measured, and the results are shown in Table 3 below.

division Composition (wt%) Al Fe Pb CD Sn Zn Example 1 0.213 0.0081 0.004 0.00010 0.000008 residual Example 2 0.221 0.0078 0.004 0.00005 0.000008 residual Example 3 0.198 0.0091 0.005 0.00008 0.000009 residual Example 4 0.211 0.0072 0.004 0.00010 0.000009 residual Example 5 0.204 0.0084 0.003 0.00009 0.000008 residual

As shown in Table 2, it can be seen that the content of impurities in the melt is lowered by the addition of Al, in particular, as shown in Table 3, it can be seen that the content of impurities in the melt is controlled to a more appropriate level by the addition of ammonium chloride.

Meanwhile. In Table 4 below, Al is added to the molten metal so as to meet the required level of demand.

It shows the case where the Al content is readjusted in the treated molten metal.

division Composition (wt%) Al Fe Pb CD Sn Zn Example 1 0.465 0.0065 0.003 0.00010 0.000009 residual Example 2 0.476 0.0071 0.004 0.00010 0.000010 residual Example 3 0.471 0.0084 0.003 0.00007 0.000070 residual Example 4 0.461 0.0080 0.003 0.00007 0.000010 residual Example 5 0.484 0.0078 0.004 0.00006 0.000007 residual

Table 4 is a component control by adding Al to be reused in the hot dip galvanizing process, by measuring the components of the process-treated molten metal and confirmed the results, it was possible to obtain high purity zinc with a recovery recovery rate of 99.5% or more. Here, adjusting the components of the molten metal by adding Al is to satisfy the standard of the combination zinc for plating.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and various changes and modifications can be made by those skilled in the art within the scope of the claims. It is self-evident.

Claims (12)

A first step of dissolving and stirring the zinc dross to discharge and remove the impurities floating on the upper portion of the molten metal; A second step of discharging and removing impurities floating in the upper part of the molten metal by stirring and adding aluminum to the molten metal in which the first step is performed; A third step of discharging and removing impurities impregnated or precipitated in the molten metal by adding and stirring a sublimable substance having a triple point temperature of 500 ° C. or less to promote the generation of intermetallic compounds of impurities in the molten metal in which the second step is performed; Zinc regeneration method of zinc dross characterized in that. The method of claim 1, The second step and the third step of the zinc dross zinc regeneration method, characterized in that carried out simultaneously. delete The method of claim 2, The sublimable material is any one of NH ₄ Cl, NH ₄ Br ₂ , NH ₄ I, NH ₂ SO ₄ , NH ₄ F and dry ice. The method of claim 4, wherein The sublimable material is zinc dross zinc regeneration method, characterized in that it is contained in the range of 0.15 ~ 0.2% by weight. The method of claim 1, After the third step, the zinc regeneration method of zinc dross characterized in that the aluminum content is re-inserted so that the aluminum content is 0.45 ~ 0.50% by weight. The method according to claim 1 or 2, And re-injecting aluminum into the molten metal after the third process to control the iron content in the molten metal. A first step of dissolving and stirring the zinc dross to discharge and remove the impurities floating on the upper portion of the molten metal; A second step of discharging and removing impurities floating in the upper part of the molten metal by stirring and adding aluminum to the molten metal in which the first step is performed; And a third step of injecting and stirring the liquefied nitrogen gas to promote the generation of the intermetallic compound of the impurity into the molten metal in which the second step is carried out to remove and remove the impurities floating or precipitated in the molten metal. Dross Zinc Regeneration Method. The method of claim 8, The second step and the third step of the zinc dross zinc regeneration method, characterized in that carried out simultaneously. The method of claim 8, The liquefied nitrogen gas is zinc dross zinc regeneration method, characterized in that it is contained in the range of 0.15 ~ 0.2% by weight. The method of claim 8, After the third step, the zinc regeneration method of zinc dross characterized in that the aluminum content is re-inserted so that the aluminum content is 0.45 ~ 0.50% by weight. The method according to claim 8 or 9, And re-injecting aluminum into the molten metal after the third process to control the iron content in the molten metal.