KR101153410B1 - Method for recovering zinc powder - Google Patents

Abstract

The present invention comprises an evaporation step of evaporating zinc by heating the zinc content in the presence of a non-oxidizing gas; A recovery step of cooling and recovering zinc evaporated by the evaporation step; And a control step of controlling the ratio of the zinc-containing content of zinc-containing content and the flow rate of the non-oxidizing gas flowing into the evaporator to 0.5 to 4 [the amount of zinc containing (kg) / non-oxidizing gas flow (m ³ / hr)]. The present invention relates to a zinc powder recovery method comprising a zinc recovery rate significantly improved, and a structure of the recovery process apparatus is simplified and economical.

Zinc recovery, zinc, recovery, evaporation, non-oxidizing

Description

Method for recovering zinc powder

The present invention comprises an evaporation step of evaporating zinc by heating the zinc content in the presence of a non-oxidizing gas;

A recovery step of cooling and recovering zinc evaporated by the evaporation step; And

A control step of controlling the ratio of the zinc-containing zinc content and the flow rate of the non-oxidizing gas flowing into the evaporator to 0.5 to 4 [the zinc content (kg) / non-oxidizing gas flow rate (m ³ / hr)]; It relates to a zinc powder recovery method.

Recently, the rust prevention in the automobile industry has been strengthened, and the use of galvanized steel for most of the steel sheets constituting the vehicle body has resulted in a rapid increase in the amount of scrap of galvanized steel sheet, which has attracted attention for its efficient recycling.

The galvanized steel sheet can be effectively reused as a cast iron steel sheet because the steel plate under the plating layer is close to pure iron, but when reusing it, a large amount of zinc material is generated in the melting process, especially in a low frequency melting furnace. It penetrates, precipitates in the coils, short-circuits the coils, and causes a problem of significantly lowering the life of the furnace walls.

If this problem is not solved, the galvanized steel sheet is a low grade steel scrap and can only be used as an iron scrap for converter steelmaking, causing a great loss in terms of iron resource recycling.

In order to solve this problem, methods for removing and recovering zinc prior to the galvanized steel sheet dissolution process have been proposed, extraction methods for dissolving and removing with an acid such as sulfuric acid (JP-A 5-9607), and electrolytic removal in an alkaline solution. (US 005106467), an evaporation method (Japanese Patent Laid-Open Publication No. 5-70855, Japanese Patent Laid-Open Publication No. 5-148458, Japanese Patent Laid-Open Publication No. 2006-37146, EU Pat. 0566451) has been proposed. .

The extraction method and the electrolytic method are wet methods using acid and alkali, and have a problem in that wastewater is generated to cause further operation of wastewater treatment facilities and secondary environmental pollution problems.

On the other hand, the evaporation method does not use water, and since the steel scrap left after zinc recovery is heated to a high temperature, it has an advantage of saving energy when used directly as a casting iron source.

As a method for recovering zinc by the evaporation method, a zinc-plated steel sheet charged into a rotary furnace is heated and oxidized with an oxygen-combustible burner and recovered as zinc oxide powder in a dust collector, which is a subsequent device (Special 1993-0021804, France, EP 0566451A1) has been proposed. Also, a method of recovering lead and zinc by adding a reducing substance to zinc-containing steel dust, first removing chlorine by heating in an atmospheric atmosphere, and then sequentially by secondary and tertiary heating in a 0.001-20 torr vacuum atmosphere Proposed.

A method of heating and evaporating a galvanized steel scrap under vacuum and sucking the evaporated zinc to the cooling condenser side by a vacuum pump to condense and recover metal zinc (JP-A 5-70855). Carbon monoxide as a non-oxidizing gas in an external rotary kiln. Method of heating and evaporating under a gas atmosphere in which (CO) and carbon dioxide (CO2) are mixed at an appropriate ratio (JP-A 5-125458) .The process vessel is evacuated under reduced pressure with a vacuum pump, followed by heating by introducing an inert gas and introducing methanol during heating. A method of recovering zinc by inducing a reducing atmosphere with carbon monoxide and hydrogen, which are decomposition products of methanol, has also been proposed.

The common process of the distillation methods to recover in the form of metal zinc proposed above is to evaporate zinc by heating the steel sheet by a heating source under a non-oxidizing gas atmosphere or a vacuum under moderate pressure to prevent oxidation of the evaporated zinc. The extracted zinc to a top or side of the reactor by a vacuum pump, and the induced evaporated zinc gas is condensed in a cooling condenser to be recovered in molten zinc form or through a water-cooled recoverer. It is discharged out of the system, cast into a predetermined shape, and recycled into various raw and subsidiary materials. At this time, the cooling condenser recovering evaporated gas has a complicated structure in which molten metal zinc, which is maintained at a constant temperature, is splashed by a rotary rotor and contacted with vapor phase zinc to condense.

However, the zinc recovery method by the evaporation method proposed or used conventionally adopts a method of introducing a non-oxidizing gas under a proper vacuum condition and splashing and recovering a specially designed cooling capacitor, that is, molten metal zinc. Not only is the structure complicated, but also the complexity of the operation and process of auxiliary equipment such as a vacuum pump to maintain proper vacuum conditions, and the recovery of zinc by contact with the splashed molten zinc metal. there is a problem.

The present invention is to solve the above problems, an object of the present invention in the recovery of metal zinc from zinc by-products, it is possible to reduce the equipment cost and equipment maintenance costs as well as the ease of operation of the equipment, simplify the metal zinc recovery process It is to provide a zinc recovery method with improved metal zinc powder recovery.

The present invention provides a means for solving the above problems, the evaporation step of evaporating zinc by heating the zinc content in the presence of a non-oxidizing gas;

A recovery step of cooling and recovering zinc evaporated by the evaporation step; And

A control step of controlling the ratio of the zinc-containing zinc content and the flow rate of the non-oxidizing gas flowing into the evaporator to 0.5 to 4 [the zinc content (kg) / non-oxidizing gas flow rate (m ³ / hr)]; It provides a zinc powder recovery method.

By using the zinc recovery apparatus of the present invention, the zinc recovery rate is remarkably improved, the structure of the recovery process apparatus is simplified, and economical.

The present invention comprises an evaporation step of evaporating zinc by heating the zinc content in the presence of a non-oxidizing gas;

A recovery step of cooling and recovering zinc evaporated by the evaporation step; And

A control step of controlling the ratio of the zinc-containing zinc content and the flow rate of the non-oxidizing gas flowing into the evaporator to 0.5 to 4 [the zinc content (kg) / non-oxidizing gas flow rate (m ³ / hr)]; It relates to a zinc powder recovery method.

Hereinafter, the zinc recovery apparatus of this invention is demonstrated in detail.

In the zinc recovery apparatus used in the method of the present invention, for example, the evaporation unit for heating the zinc content and the zinc recovery unit for cooling the evaporated zinc to recover the zinc powder is preferably configured as a separate facility. That is, the apparatus is a vapor-only condensation unit for heating the zinc-containing material to evaporate zinc, and a zinc-only recovery unit equipped with a cooling system connected to the evaporation-only conduit, and a structure in which a dust collector is integrated with a conduit at the rear of the zinc recovery unit. By using the zinc recovery apparatus, the metal zinc can be recovered from the zinc-containing material.

That is, the zinc recovery device is a cooling system along the conduit due to the flow of non-oxidizing atmosphere adjusting gas in which the evaporated zinc gas phase is injected into the evaporation furnace, the pressure and temperature difference of the evaporation furnace and the zinc recovery dedicated portion. It is moved to the zinc recovery unit provided with condensation, is recovered as zinc powder. According to the cooling state of the zinc recovery unit, the zinc powder that is not recovered from the zinc recovery unit may have a structure in which a gas is collected in the dust collector installed at the rear end of the zinc recovery unit and the gas of which zinc powder recovery is completed is discharged to the atmosphere.

In the present invention, in order to improve the recovery rate of zinc powder in the zinc recovery unit, the amount of zinc oxide contained in the non-oxidizing gas inflow amount into the evaporation unit and the raw material introduced into the evaporation unit, that is, the ratio of zinc content to the non-oxidizing gas inflow amount (in the input raw material box). It is characterized by adjusting the amount of zinc (Kg) / non-oxidizing gas flow rate (m ³ ) to the evaporation section in the range condition of 0.5 to 4, more preferably in the range of 1-2.

If the ratio of zinc oxide content in the raw material to the inflow of non-oxidizing gas is less than 0.5, the zinc powder is not produced and grown due to the collision of the zinc gases evaporated during the condensation process. It is not possible to improve the zinc recovery rate because of the large amount of gas released into the atmosphere in the fume state (0.1um or less).

In addition, when the ratio of the amount of zinc content in the raw material to the inflow rate of non-oxidizing gas is 4 or more, the rate of recovery in particulate form (more than 100 μm) is increased due to the overcondensation of the boil-off gas rather than in the form of metal zinc powder to be obtained in the present invention. Because it is not desirable.

Therefore, in the present invention, it is necessary to react by adjusting the ratio of the amount of zinc-containing zinc to the amount of non-oxidizing gas, which is obtained in the form of zinc powder, by an appropriate condensation process by contacting the evaporated zinc gases to 0.5 to 4 ranges.

The evaporation step of the present invention takes place under a non-oxidizing gas atmosphere. Since zinc gas heated and evaporated at a high temperature has a very high activity, even if a very small amount of oxygen is present in the evaporator, the zinc gas may react with oxygen to form zinc oxide. Therefore, control to a non-oxidizing gas atmosphere is important for recovering in the form of metal zinc. That is, the oxidation of zinc on the metal content in the non-oxidizing gas atmosphere is suppressed, and metal zinc with high purity can be obtained.

In the present invention, the type of the non-oxidizing gas is not particularly limited. For example, an inert gas such as argon gas and nitrogen gas, a mixed gas of argon and hydrogen, or a mixed gas of nitrogen and hydrogen may be used. Nitrogen gas or a mixed gas of nitrogen and hydrogen may be used.

In particular, in the mixed gas of nitrogen and hydrogen, hydrogen gas is a gas having excellent reducing power, and thus reacts with oxygen existing in the evaporator to consume and remove the oxygen, thereby recovering high purity metal zinc.

In the mixed gas of nitrogen and hydrogen of the present invention, the mixed gas preferably contains hydrogen in an amount of 4% by weight or less. If the content of hydrogen exceeds 4% by weight there is a risk of explosion.

In addition, in the present invention, the kind of zinc-containing material is not particularly limited, and for example, a group consisting of zinc-containing dust, zinc-containing powder, zinc-containing molded body, galvanized steel sheet scrap, galvanized steel coil and zinc compressed plated steel sheet scrap. It may include one or more selected from, if it is necessary to control the amount of zinc contained in the feedstock can be used with zinc dross by-products in the zinc plating process.

In the present invention, the evaporator is provided with a heating source, the zinc containing may be charged, and the zinc containing may be heated to evaporate zinc. The shape and material of the evaporation unit are not particularly limited, and shapes and materials used in the art may be used.

In the present invention, if the heating source can increase the temperature of the evaporator, the position is not particularly limited, and may be installed inside the evaporator or outside the evaporator. The heating source should have a structure that uniformly heats and maintains all the temperature of the location inside the evaporator at 910 ° C. or higher. That is, since the volatilization temperature of zinc is 908 ° C, it exists as a gas phase above this temperature, but if there is a temperature deviation inside the evaporation furnace and a temperature of lower temperature exists, the vaporized zinc gas phase is condensed and traced there. As a result, the zinc recovery rate in the dedicated zinc recovery unit cannot be expected. Therefore, all the parts inside the evaporation furnace should have a structure that should be heated and maintained uniformly above 908 ℃ without temperature variation.

In the present invention, the evaporation unit may further include a reaction vessel, the reaction vessel may accommodate the zinc containing. In particular, in the present invention, it is preferable to use a reaction vessel when the zinc-containing substance is in the form of dust or scrap. In the case where the zinc-containing material is in the form of dust or scrap, when directly charged into the evaporation part, the process may be affected by the blowing of particles, etc., and thus the zinc-containing material may be charged using a reaction vessel. On the other hand, in the case of a compacted compact, it can be used by loading on a skid without charging in a reaction vessel.

The material of the reaction vessel is not particularly limited, heat-resistant steel or graphite may be used, preferably graphite may be used. When using ordinary steel as a reaction vessel, the service life is shortened due to repeated thermal history and high temperature. In addition, when the heat resistant steel is used as the reaction vessel, the heat history and the high temperature are less affected, but there is a fear that zinc evaporated from the zinc containing reacts with the reaction vessel to form a alloy. On the contrary, since graphite is an inorganic material, when the graphite is used as a reaction vessel, not only does it deteriorate, but also does not occur with the evaporated metal zinc and thus can be used semi permanently.

The zinc recovery step of the present invention is a step of recovering by cooling and condensing the zinc gas evaporated in the evaporator in a recovery unit including a cooling unit.

Cooling water circulation pipe may be connected to the cooling unit. Since the coolant moves in the coolant circulation pipe along the pipe, it is possible to maintain the temperature of the zinc recovery part (particularly the cooling part) raised by the zinc gas at a desired temperature.

The present invention may further include a dust collecting step of collecting the unrecovered zinc powder in the dust collector installed at the rear end of the zinc recovery unit. The dust collecting unit may appropriately select and use an electrostatic precipitator EP, a cyclone (CY), a bag filter, or the like.

Example

Hereinafter, the present invention will be described in more detail through examples according to the present invention, but the scope of the present invention is not limited to the following examples.

Examples 1 to 3

60T galvanized steel sheet (60cmX70cm, zinc content 2%), 200kg by weight into 100cmX80cmX60cm heat resistant steel sample container Nitrogen was purged at 10 rubes / hour until the oxygen concentration in the evaporator-zinc recovery-dust collection unit system became less than 100 ppm. Thereafter, the temperature was raised to 1100 ° C. while flowing nitrogen gas at 3 rubes / hour, followed by cooling for 2 hours. At this time, the ratio of the amount of zinc contained in the input material to the amount of non-oxidizing gas inflow during the temperature raising, maintaining, and cooling was 1.3.

In addition, nitrogen gas was changed to 8 rubes / hour and 1 rubbe / hour, respectively, during heating, holding, and cooling.

The zinc recovery unit equipped with the water cooling system at the rear end of the evaporator connected to the evaporator was continuously flowing the cooling water from the start of the reaction to the end of the reaction. Metal zinc powder samples recovered from the zinc recovery unit after the reaction were collected and weighed, and the results are shown in Table 1.

Comparative Examples 1 and 2

60 sheets of 0.5T galvanized steel sheet (60cmX70cm, zinc content 2%), 200Kg in weight and 100cmX80cmX60cm heat-resistant steel sample container Phosphorus nitrogen was purged at an evaporation rate of 10 rubes / hour until the concentration of oxygen in the zinc-collecting portion-dust collector integrated system became 100 ppm or less. Thereafter, the nitrogen gas was heated to 1100 ° C. while flowing at 10 rubes / hour and 0.5 rubes / hour, and then cooled by maintaining for 2 hours. At this time, the ratio of the amount of zinc contained in the input material to the inflow rate of non-oxidizing gas during the temperature raising, holding and cooling was 0.4 and 8.0.

Reaction condition Measurement result Hama ( Kg ) Of Non-oxidizing gas  Inflow (m ³ ) evaporation
Temperature maintain
time Zinc
Recovery Metal zinc
Powder recovery Remainder room
city
Yes One 1.3 1100 ℃ 2 hr . 4.0 kg 95% (3.8 kg ) 0.2 kg  Particulate
part ZnO Mixed 2 0.5 1100 ℃ 2 hr . 3.9 kg 90% (3.51 Kg ) 0.39 kg
( Fume loss )
part ZnO Mixed 3 4.0 1100 ℃ 2 hr . 3.9 kg 90% (3.51 kg ) 0.2 kg  Particulate
part ZnO Mixed Comparative example One 0.4 1100 ℃ 2 hr . 0.6 kg 15% (0.6 Kg ) Fume loss 2 8.0 1100 ℃ 2 hr . 3.8 Kg 40% (1.52 Kg ) 2.28 kg Particulate
part ZnO Mixed

As shown in Examples 1, 2, and 3 of Table 1, when the heating and evaporation were respectively adjusted to the range of 0.5 to 4 in the feedstock content ratio relative to the non-oxidizing gas inflow, the zinc recovery part was recovered. The recovery rate of the metal zinc powder was 95%, 90% and 90%, respectively, which was more than 90%. The remaining amount was found to be in particulate form or fume loss depending on the respective conditions, and some of the remaining amount was oxidized to be white zinc oxide. Existed in the form.

On the other hand, in the case of Comparative Examples 1 and 2 heated and evaporated by adjusting the ratio of zinc content in the feedstock to the amount of non-oxidizing gas inflow to 0.4 and 8.0, the recovery rate of the metal zinc powder was only about 15% and 40%. Especially, in case of Comparative Example 1 in which the non-oxidizing gas inflow was adjusted to 10 rubes / hour, about 85% loss occurred due to fume generation, and in Comparative Example 2 in which the non-oxidizing gas inflow was adjusted to 0.5 rube / hour. At least about 50% of the recovered zinc was recovered in particulate form.

Judging from these results, it can be seen that in order to improve the recovery rate of the zinc metal powder, it is preferable to adjust the ratio of the amount of zinc containing in the input material to the inflow of non-oxidizing gas in the range of 0.5 to 4 to heat and evaporate it.

Examples 4-5

60T galvanized steel sheet (60cmX70cm, zinc content 2%), 200kg by weight into 100cmX80cmX60cm heat resistant steel sample container Nitrogen was purged at 10 rubes / hour until the oxygen concentration in the evaporator-zinc recovery-dust collection unit system became less than 100 ppm. Thereafter, the mixture was heated to 1100 ° C. while flowing nitrogen + hydrogen mixed gas (hydrogen mixture ratio 4%) at 3 rubes / hour, and then cooled for 2 hours. At this time, the ratio of the amount of zinc contained in the input material to the amount of non-oxidizing gas inflow during the temperature raising, maintaining, and cooling was 1.3. In addition, 60 sheets of 1.0T galvanized steel sheet (60cmX70cm, zinc content 0.5%), pre-loaded and loaded 200Kg in a 100cmX80cmX60cm heat-resistant steel sample container and weighed 3.7kg of zinc dross ingot (80% zinc content) After charging, the internal volume was charged into a three-lube evaporation furnace and purged with a non-oxidizing gas of 10 rubes / hour until the oxygen concentration in the evaporator-zinc-recovery-dust collector integrated system became less than 100 ppm. Thereafter, the mixture was heated to 1100 ° C. while flowing nitrogen + hydrogen mixed gas (hydrogen mixing ratio 4%) at 3 rubes / hour, and then cooled for 2 hours. At this time, the ratio of the amount of zinc contained in the input material to the amount of non-oxidizing gas inflow during the temperature raising, maintaining, and cooling was 1.3.

The zinc recovery unit equipped with the water cooling system at the rear end of the evaporation furnace connected to the evaporation furnace and the conduit continued to flow the cooling water from the start of the reaction to the end of the reaction. After the reaction, the metal zinc powder samples recovered from the zinc recovery unit were collected and weighed, and the results are shown in Table 2.

Comparative Example 3

60 sheets of 0.8T galvanized steel sheet (60cmX70cm, zinc content 0.5%), 200Kg in weight, loaded into 100cmX80cmX60cm heat-resistant steel sample container and loaded, and the internal volume is loaded into the evaporation part of 3L vane. Nitrogen was purged until the oxygen concentration in the furnace-zinc collection section-dust collector integrated system was below 10 ppm by evaporation at 10 rubes / hour. Thereafter, the mixture was heated to 1100 ° C. while flowing nitrogen + hydrogen mixed gas (hydrogen mixing ratio 4%) at 3 rubes / hour, and then cooled for 2 hours. At this time, the ratio of the amount of zinc contained in the input material to the amount of non-oxidizing gas inflow during the temperature raising, holding, and cooling was 0.3.

The zinc recovery unit equipped with the water cooling system at the rear end of the evaporation furnace connected to the evaporation furnace and the conduit continued to flow the cooling water from the start of the reaction to the end of the reaction. After the reaction, the metal zinc powder sample recovered from the zinc recovery unit was collected and weighed, and the results are shown in Table 2.

Reaction condition Measurement result Hama ( Kg ) / Non-oxidizing gas flow rate (m ³ ) gas Holding temperature
time Zinc
Recovery Metal zinc
Powder recovery Remainder room
city
Yes 4 1.3 Hydrogen + nitrogen 1100 ℃
2 hr 4.0 Kg 98%
(3.92 Kg ) 800g particulate 5 1.3 (zinc content: adjustment of zinc dross addition) Hydrogen + nitrogen 1100 ℃
2 hr 4.0 kg 98%
(3.92 Kg ) 800g particulate Comparative example 3 0.3 Hydrogen + nitrogen 1100 ℃
2 hr 0.4 Kg 10%
(0.4 kg ) Fume loss

As shown in Examples 4 and 5 of Table 2, to adjust the ratio of zinc oxide content in the feedstock to the non-oxidizing gas inflow, the zinc dross ingot was adjusted to 1.3, and the ratio was adjusted to 1.3. When the mixture was heated and evaporated using a nitrogen gas mixture, the recovery rate of the metal zinc powder recovered from the zinc recovery unit was 98%, and no zinc oxide powder was produced.

This can be seen that in the case of using only nitrogen gas as a non-oxidizing gas in Examples 1 to 3 it can be seen that the metal zinc powder recovery can be improved by more than 3%. It can be seen from this that it is preferable to use a mixed gas of nitrogen gas and hydrogen gas having an appropriate mixing ratio in order to control the atmosphere in the evaporation chamber to a completely non-oxidizing atmosphere. Hydrogen gas is the gas with the best reducing power, and it reacts with oxygen existing in the reactor first and consumes and removes oxygen, so it can maintain a completely non-oxidizing atmosphere and recover all evaporated zinc in the form of metal zinc. .

Even when the hydrogen + nitrogen mixed gas is used as the non-oxidizing gas as in Comparative Example 3, the recovery rate of the metal zinc powder can be improved unless the ratio of the content of zinc content in the feedstock to the non-oxidizing gas inflow is not adjusted within the range of 0.5 to 4, which is the scope of the present invention. You can see that you can't.

Claims (7)

An evaporation step of evaporating zinc by heating the zinc content in the presence of a non-oxidizing gas; A recovery step of cooling and recovering zinc evaporated by the evaporation step; And A control step of controlling the ratio of the zinc-containing zinc content and the flow rate of the non-oxidizing gas flowing into the evaporator to 0.5 to 4 [the zinc content (kg) / non-oxidizing gas flow rate (m ³ / hr)]; Zinc powder recovery method. The method of recovering zinc powder according to claim 1, wherein the non-oxidizing gas is nitrogen gas or a mixed gas of nitrogen and hydrogen. The method of recovering zinc powder according to claim 2, wherein the mixed gas of nitrogen and hydrogen contains 4 wt% or less of hydrogen. The zinc powder recovery according to claim 1, wherein the zinc-containing material comprises at least one selected from the group consisting of zinc-containing dust, zinc-containing powder, zinc-containing molded body, galvanized steel sheet scrap, galvanized steel coil and zinc compressed plated steel scrap. Way. 5. The method of claim 4, wherein the zinc content further comprises zinc dross. The zinc powder recovery method according to claim 1, wherein the temperature of the evaporation unit is controlled to be 910 ° C or higher. The zinc powder recovery method of claim 1, further comprising a dust collecting step of collecting the unrecovered zinc powder in the zinc recovery unit.