JP5425486B2 - Zinc separation from zinc steel scrap - Google Patents

Description

  The present invention relates to a method for separating zinc from galvanized steel scrap for recycling as a casting raw material of scrap iron in the steel and casting field, for example. More specifically, it uses induction heating characteristics and iron properties to volatilize and separate zinc components contained in galvanized steel scraps from galvanized steel scraps that contribute to energy saving, resource saving and cost reduction. The present invention relates to a method for separating zinc.

  When zinc steel scraps are melted in an electric furnace (induction heating furnace), the zinc vapor damages the furnace wall (refractory) of the electric furnace and adversely affects the quality of the cast product. For this reason, it is necessary to remove zinc when the zinc steel scrap is melted using an electric furnace. Therefore, for example, a method of volatilizing and removing zinc in galvanized steel scrap at 900 ° C. and about 0.0002 atm in a high vacuum firing furnace is known. There is also known a method in which zinc steel scraps are melted in an induction heating flat furnace, and the zinc is volatilized and removed by reducing the pressure to about 0.9 atm.

  However, the former method is disadvantageous in that high vacuum is used and batch processing is performed, so that operation efficiency is poor, equipment costs are increased, and indirect heating is required because of the indirect heating. On the other hand, in the latter method, although the life of the refractory furnace wall can be extended a little, the effect is not sufficient and there is a drawback that the durability is insufficient.

  The following proposal is made about the recycling system of the steelmaking dust containing this kind of dezincing process (for example, refer to patent documents 1). That is, a granulation process in which dust mainly composed of iron and its oxide generated in the steel production process is mixed with a powder mainly composed of carbon and granulated, and water in which the mixed granulated body is impregnated with water. An impregnation process, a solidification process in which the mixed granulated body is pressed and solidified, and a dezincification process in which the zinc of dust is concentrated to reach the solidification process. ing.

  Further, a scrap processing method has been proposed in which zinc-containing scrap is heated and held at 650 ° C. or higher in a non-oxidizing atmosphere to volatilize and remove zinc (see Patent Document 2). Further disclosed is a method for purifying crude zinc comprising a step of evaporating crude zinc, a step of collecting iron and lead from the evaporated zinc vapor, a step of condensing zinc from the zinc vapor, and a step of condensing cadmium. (See Patent Document 3). In addition, galvanized steel sheet scraps are preheated at 400 to 450 ° C. at atmospheric pressure and then heated at 500 to 900 ° C. at 0.16 Torr (mmHg) or less to evaporate and separate zinc, and further maintain the degree of vacuum. On the other hand, a zinc removal method is known in which evaporated zinc is cooled and solidified at 400 ° C. or lower to form metallic zinc (see Patent Document 4).

  In addition, the galvanized steel sheet scraps are heated in a vacuum furnace under reduced pressure to evaporate the galvanized layer, and the evaporated zinc is separated from the vacuum processing furnace, and has a higher pressure and lower temperature than the vacuum processing furnace. There is known a zinc removing method in which evaporated zinc is solidified and collected in this zinc recovery chamber (see Patent Document 5). Furthermore, a method for treating iron-making dust that reduces and volatilizes zinc while reducing iron-making dust with a reducing gas has been proposed (see Patent Document 6). In addition, a dezincing method is disclosed in which after the inside of a processing container containing metal scrap is evacuated under reduced pressure, the processing container is heated and methanol is introduced (see Patent Document 7).

JP 2007-270229 A (2nd page, 3rd page and FIG. 1) JP-A-7-138664 (2nd and 3rd pages) JP-A-6-108175 (pages 2 and 5) JP-A-6-287657 (Pages 2 and 3) JP-A-6-184657 (pages 2 and 3) Re-published patent WO97 / 32048 (page 2, page 3, page 6 and page 11) JP 2006-37146 A (page 2, page 3, page 5 and page 6)

  However, in the dezincing treatment step described in Patent Document 1, the efficiency of the dezincing treatment can be increased because the zinc of dust is concentrated and the dezincing treatment is performed, but the dezincing treatment method itself is a new one. Since the method is not described, the dezincification method itself is not improved.

  In the scrap processing method described in Patent Document 2, there is a problem that the reduction reaction of zinc oxide is slow because the heating is only performed in a non-oxidizing atmosphere, and the volatilization removal efficiency of zinc is low. In addition, when separating zinc from steel scrap containing zinc, the state of iron is involved, and unless the state is taken into account, zinc cannot be separated efficiently by uniform heating and rapid reduction reaction of zinc oxide. However, no such consideration has been made.

  In the crude zinc purification method described in Patent Document 3, since the evaporation temperature of the crude zinc is specifically 580 to 620 ° C., the evaporation of zinc is not sufficient and the removal efficiency of zinc is poor. In the zinc removal method described in Patent Document 4, it is necessary to remove zinc under conditions of a very high degree of vacuum. Such setting of conditions is difficult, and there is a drawback that the removal efficiency of zinc is poor. It was. Even in the zinc removal method described in Patent Document 5, it is necessary to recover zinc in a zinc recovery chamber after further heat treatment in a vacuum processing furnace, and in a zinc recovery chamber, the setting of conditions is strict and the efficiency of zinc removal There was a fault that it was bad.

  In the iron dust processing method described in Patent Document 6, after iron dust and carbon material are mixed, a reducing gas containing hydrogen or carbon monoxide is supplied to the rotary furnace, and reduction treatment is performed at 900 ° C. or 950 ° C. However, the iron state is not considered. For this reason, heating and heat conduction in the rotary furnace requires time and energy for heating, resulting in inefficient space, space loss being directly linked to energy loss, and rapid progress of the zinc oxide reduction reaction. Therefore, zinc cannot be separated efficiently. In the dezincification method described in Patent Document 7, specifically, the inside of the processing vessel is evacuated and heated to 460 ° C., then methanol is introduced when the temperature reaches 600 ° C., and then heated to 950 ° C., Hold at that temperature for about 60-90 minutes. However, at 600 ° C., the reduction rate is slow and the zinc separation efficiency is poor. Further, at 950 ° C., the temperature is higher than the temperature showing the transformation point from α iron to γ iron, and the holding time at that temperature is long.

Therefore, it is expected to efficiently remove zinc by controlling the heating at a temperature at which the amorphous zinc steel scrap is not dissolved by induction heating.
The present invention has been made paying attention to such problems existing in the prior art, and the object thereof is a zinc steel material that can efficiently remove zinc without melting and fixing iron. The object is to provide a method for separating zinc from waste.

In order to achieve the above object, the method for separating zinc from zinc steel scraps according to claim 1 is a method of separating zinc by heating zinc steel scraps,
In the dezincification furnace, in the presence of a reducing agent, induction heating of zinc steel scrap from the temperature showing the iron magnetic transformation point to the temperature showing the transformation point from α iron to γ iron, without melting and fixing the iron It is characterized in that zinc oxide contained in zinc steel scrap is reduced and converted into metallic zinc, and the metallic zinc is volatilized and separated.

According to a second aspect of the invention, there is provided a method for separating zinc from zinc steel scrap, wherein the reducing agent is carbon.
The method for separating zinc from zinc steel scraps according to claim 3 is the invention according to claim 1 or 2, wherein the amount of the reducing agent added is 0.1 to 10% by mass with respect to the zinc steel scraps. It is characterized by.

  A method for separating zinc from zinc steel scraps according to claim 4 is the invention according to any one of claims 1 to 3, wherein the zinc steel scraps in the dezincification furnace are at a temperature indicating the magnetic transformation point of the iron. The temperature is maintained at 770 ± 50 ° C., and the temperature of the galvanized steel scrap in the dezincification furnace is maintained at 910 ± 50 ° C. at a temperature indicating a transformation point from α iron to γ iron.

The method for separating zinc from zinc steel scrap according to claim 5 is the invention according to any one of claims 1 to 4, wherein the pressure reduced in the entire period of separating zinc in the dezincification furnace is: It is set within a range of 81.25 to 101.15 kPa .

  The method for separating zinc from zinc steel scrap according to claim 6 is the invention according to any one of claims 1 to 5, wherein the inside of the dezincification furnace is set to a reducing atmosphere or an inert gas atmosphere. Features.

  The method for separating zinc from zinc steel scraps according to claim 7 is the invention according to any one of claims 1 to 6, wherein when the zinc steel scraps reach a temperature indicating a magnetic transformation point of iron or α The temperature difference between the maximum temperature and the minimum temperature of the galvanized steel scrap in each region in the dezincification furnace is maintained within 50 ° C. when the temperature indicating the transformation point from iron to γ iron is reached. .

According to the present invention, the following effects can be exhibited.
In the method for separating zinc from galvanized steel scrap according to claim 1, in the presence of a reducing agent in a dezincification furnace, from a temperature indicating the magnetic transformation point of iron to a temperature indicating a transformation point from α iron to γ iron. Zinc steel scraps are induction-heated, zinc oxide contained in the zinc steel scraps is reduced and converted into metallic zinc without melting and fixing iron, and the metallic zinc is volatilized and separated. For this reason, iron in zinc steel scrap is heated and changes from the magnetic transformation point (A2 transformation point) where the magnetism disappears to the transformation point from α iron to γ iron (A3 transformation point). In the process, zinc oxide changes to metal zinc which is easily volatilized based on the reducing action of the reducing agent. Therefore, zinc can be efficiently removed without dissolving and fixing iron.

  In the method for separating zinc from zinc steel scrap according to claim 2, since the reducing agent is carbon, in addition to the effect of the invention according to claim 1, the reduction action of zinc oxide can be improved and the removal of zinc The rate can be increased. Furthermore, since the reducing agent is composed of carbon, and the carbon has a property of being heated faster than zinc steel plate scraps by induction heating, in addition to being used for reducing zinc oxide or forming a reducing atmosphere, the level of the zinc steel plate scraps is not limited. It can contribute to thermalization.

  In the method for separating zinc from the zinc steel material waste according to claim 3, the amount of the reducing agent added is 0.1 to 10% by mass with respect to the zinc steel material waste. Therefore, in addition to the effect of the invention according to claim 1 or claim 2, the reduction action of zinc oxide can be sufficiently exhibited, and the removal rate of zinc can be further increased.

  In the method for separating zinc from galvanized steel scraps according to claim 4, the temperature of the galvanized steel scraps in the dezincification furnace is once uniformly heated and maintained at 770 ± 50 ° C. at a temperature indicating the magnetic transformation point of iron. When heating to a temperature indicating the transformation point from iron to γ iron, the temperature of the galvanized steel scrap in the dezincification furnace is easily controlled to be uniformly heated to 910 ± 50 ° C. For this reason, the effect of the invention according to any one of claims 1 to 3 can be improved.

In the method for separating zinc from galvanized steel scraps according to claim 5 , the pressure reduced in the entire period of separating zinc in the dezincification furnace is set in the range of 81.25 to 101.15 kPa . Therefore, in addition to the effects of the invention according to any one of claims 1 to 4, zinc can be removed under reduced pressure, and the removal rate of zinc can be further increased.

In the method for separating zinc from galvanized steel scrap according to claim 6, the inside of the dezincification furnace is set to a reducing atmosphere or an inert gas atmosphere. For this reason, in addition to the effect of the invention according to any one of claims 1 to 5, the influence of oxygen can be avoided and the reduction reaction of zinc oxide can proceed smoothly. The reducing atmosphere is formed by heating while preventing air inflow in the dezincification furnace, and reacting with the reducing agent and air or zinc oxide in the galvanized steel plate scrap to generate CO gas. Furthermore, a reducing atmosphere can be formed by blowing a reducing gas such as CO gas or CH ₄ gas into a dezincing furnace without adding a solid reducing agent, and zinc can be separated. .

  In the method for separating zinc from galvanized steel scrap according to claim 7, when the galvanized steel scrap reaches a temperature indicating a magnetic transformation point of iron or a temperature indicating a transformation point from α iron to γ iron, dezincification is performed. The temperature difference between the maximum temperature and the minimum temperature of the galvanized steel scrap in each region in the furnace is maintained within 50 ° C. For this reason, in addition to the effect of the invention which concerns on any one of Claims 1-6, the soaking | uniform-heating of zinc-steel material waste can be improved further.

Sectional drawing which shows typically the apparatus provided with the dezincification furnace for isolate | separating metallic zinc from zinc steel material waste. The graph which shows the relationship between the heating time in the reference example 1, and the temperature in a dezincification furnace. The graph which shows the relationship between the pressure in the dezincification furnace in reference example 2, and total zinc volatilization temperature. Sectional drawing which shows typically another apparatus provided with the dezincification furnace for isolate | separating metallic zinc from zinc steel material waste. The graph which shows the relationship between the heating time in Example 1, and the temperature in a dezincification furnace. The graph which shows the relationship between the heating time in Example 2, and the temperature in a dezincification furnace. The graph which shows the relationship between the heating time in Example 3, and the temperature in a dezincification furnace. The graph which shows the relationship between the heating time in Example 4, and the temperature in a dezincification furnace. The graph which shows the relationship between the heating time in Example 5, and the temperature in a dezincification furnace.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
The method for separating zinc from zinc steel scraps in this embodiment is a method of separating zinc by induction heating of zinc steel scraps, and without melting and fixing iron (melting point: 1535 ° C.) (Boiling point 907 ° C.). That is, in the presence of a reducing agent in the dezincification furnace, induction heating is performed from the temperature showing the iron magnetic transformation point to the temperature showing the transformation point from α iron to γ iron, and the zinc oxide contained in the zinc steel scrap is reduced. Thus, it is converted into metallic zinc, and the metallic zinc is volatilized and separated.

  Zinc steel scrap is scrap iron after using steel and contains zinc oxide. Zinc oxide [ZnO, boiling point (sublimation point) 1725 ° C.] contained in this zinc steel scrap is reduced by a reducing agent to become metallic zinc (Zn) that can be easily separated by volatilization. The type of the reducing agent is not limited as long as it can exhibit such a reducing action, but carbon is preferably used. Examples of carbon include 98% granular carbon (carburized material) and coke.

  The amount of the reducing agent added is preferably 0.1 to 10% by mass and more preferably 0.2 to 2% by mass with respect to the zinc steel scrap. When the addition amount of the reducing agent is less than 0.1% by mass, the reducing agent is insufficient and zinc oxide cannot be sufficiently reduced. On the other hand, when it exceeds 10% by mass, the reducing agent becomes excessive and the reducing agent that is not used for the reduction of zinc oxide remains and is wasted.

  The iron transformation point means the temperature at which the atomic arrangement and physical properties change, and the magnetic transformation point (A2 transformation point) disappears from the magnetized state as the temperature rises. The temperature is 770 ° C. (1040 K) for pure iron. This magnetic transformation point is almost unaffected by the carbon content in the iron and is almost constant. On the other hand, the transformation point (A3 transformation point) from α iron to γ iron is 910 ° C. (1183 K) in pure iron. The transformation point from α iron to γ iron is a transformation of the crystal form of iron from body-centered cubic to face-centered cubic, and this transformation point decreases with an increase in the carbon content in iron.

  As for the heating temperature, at the temperature showing the A2 transformation point, which is the magnetic transformation point of iron, the temperature of the galvanized steel scrap in the dezincification furnace is uniformly heated and maintained at 770 ± 50 ° C., and from α iron to γ iron It is preferable that the temperature of the galvanized steel scrap in the dezincification furnace 11 is uniformly heated and maintained at 910 ± 50 ° C. as a whole at the temperature indicating the A3 transformation point, which is the transformation point. As described above, by induction heating to a temperature at which the characteristics of iron change, a reduction reaction for reducing zinc oxide to produce metallic zinc can be easily performed. For this reason, it is not necessary to input heat energy more than necessary in a state where iron does not melt, and it is possible to efficiently remove metallic zinc. When the heating temperature is lower than the magnetic transformation point, the reduction reaction from zinc oxide to metallic zinc cannot proceed efficiently. On the other hand, when the heating temperature exceeds the transformation point from α iron to γ iron by 50 ° C. or more, in addition to requiring excessive heat energy, it is locally accompanied by a discharge phenomenon between adjacent zinc steel scraps. Concerns about melting and sticking increase, and handling properties decrease.

  Further, when the magnetic transformation point of iron or the transformation point from α iron to γ iron is reached, the temperature can be maintained in that temperature for a certain period of time, so that the soaking in the dezincification furnace 11 can be achieved. The time for holding at a constant temperature is, for example, 10 to 60 minutes when the magnetic transformation point is reached, and for example, 5 to 30 minutes when the transformation point from α iron to γ iron is reached. This time can be appropriately set according to the temperature distribution in the dezincification furnace 11 or the like. Thus, local overheating in the dezincification furnace 11 can be suppressed by achieving temperature uniformity in the dezincification furnace 11. Accordingly, in the dezincification furnace 11, partial melting of iron can be prevented, and adhesion between irons and adhesion of iron to the furnace wall can be prevented.

When carrying out the zinc separation method, the pressure in the dezincification furnace is preferably set to a reduced pressure of 101.15 to 81.25 kPa in order to promote the separation of metallic zinc. That is, the differential pressure from the atmospheric pressure (101.25 kPa) is desirably −0.1 to −20 kPa. By setting the pressure in the dezincification furnace to a reduced pressure in this manner, metallic zinc can be sucked and removed, and separation and removal of metallic zinc can be performed efficiently. When the pressure in the dezincification furnace is higher than 101.15 kPa, the effect of reducing the pressure in the dezincification furnace is reduced, and the efficiency of sucking and removing metal zinc is deteriorated. On the other hand, if the pressure is lower than 81.25 kPa, excessive energy is required to reduce the pressure to such a high degree of pressure reduction, and the metal zinc separation efficiency corresponding to that is not obtained.

  Moreover, the reduction reaction of zinc oxide can be promoted by setting the inside of the dezincification furnace to a reducing atmosphere or an inert gas atmosphere. The reaction to produce metallic zinc from solid reducing agent such as granular coke (carburized material) and zinc oxide is a reduction reaction as shown in the following reaction formula (1). A gas atmosphere is preferred.

ZnO + C → Zn + CO (1)
Of these atmospheres, a reducing atmosphere is most preferable because it can promote a reduction reaction. By suppressing the air inflow into the dezincification furnace, the carbon monoxide (CO) gas generated by the reaction of the following reaction formula (2) between the carburized material and air is further based on the following reaction formula (3), Promotes reduction of zinc oxide. Further, as an alternative to the solid reducing agent, the zinc separation process can also be performed by mixing and heating a reducing gas such as CO gas or methane (CH ₄ ) gas in the dezincification furnace.

C + 1 / 2O ₂ → CO (2)
ZnO + CO → Zn + CO ₂ (3)
Note that in an air atmosphere where a large amount of oxygen is present, oxygen contained in the air is not preferable because it inhibits the reduction reaction.

  As schematically shown in FIG. 1, an apparatus for separating zinc from galvanized steel scrap has an induction heating coil 12 on the outer peripheral surface of a bottomed cylindrical fire-resistant dezincification furnace (crucible) 11. It is configured to be wound and induction heated. And when separating zinc from galvanized steel scrap, the raw material 13 containing the galvanized steel scrap and reducing agent is put into the dezincification furnace 11 and heated to a predetermined temperature with a cover not shown in the figure kept confidential. Is done. As a result, the zinc oxide contained in the zinc steel scrap is reduced and converted to metallic zinc, and the converted highly volatile metallic zinc is volatilized and separated. In addition, the return material 14 may be put into the dezincification furnace 11 together with the zinc steel material waste and heated.

  Moreover, the apparatus for isolate | separating zinc from zinc steel material waste is comprised as shown, for example in FIG. That is, the dezincification furnace 11 is accommodated in an outer container 15 for heat insulation, and an induction heating coil 12 is wound around the outer periphery of the dezincification furnace 11 for induction heating. A hood 16 for sealing the inside of the dezincification furnace 11 is put on the upper end portion of the dezincification furnace 11. A plurality of thermocouples 17 are inserted in the dezincification furnace 11 so that the temperature of each part in the dezincification furnace 11 can be measured. A differential pressure gauge 18 for measuring a differential pressure from the atmospheric pressure is attached to the hood 16. Further, an air inflow valve 20 and a dust collector (zinc collector) 21 are connected to the hood 16 through an exhaust pipe 19 so that metallic zinc converted in the dezincification furnace 11 is exhausted. When it is difficult to reduce the CO gas only by air inflow, a small hot air generator can be installed instead of the air inflow valve 20 to reliably burn the CO gas.

In this embodiment, the gaseous metallic zinc changes into a zinc oxide solid powder simultaneously with the combustion of the CO gas, so that it is recovered by the dust collector 21 as zinc oxide dust. If necessary, a cooler is installed in front of the dust collector 21. Also, when recovering as metallic zinc, the combustor is eliminated and the zinc recovery unit (multi-layer cooling plate) condenses and recovers the metallic zinc on the cooling plate and recovers the catalyst in the downstream process of the zinc recovery unit. release CO gas as harmless CO ₂ using. Alternatively, this CO gas is reused as a reducing gas or fuel.

The effects exhibited by the embodiment described in detail above will be collectively described below.
In the method for separating zinc from zinc steel scrap in this embodiment, in the dezincification furnace 11, in the presence of a reducing agent, zinc steel scrap is induction-heated from the iron magnetic transformation point to the transformation point from α iron to γ iron. Then, the zinc oxide contained in the zinc steel scrap is reduced and converted into metallic zinc without melting and fixing iron, and the metallic zinc is volatilized and separated. For this reason, the iron in zinc steel scrap is heated and changes from the magnetic transformation point at which magnetism disappears to the transformation point from α iron to γ iron, and in that state, zinc oxide volatilizes based on the reducing action of the reducing agent. It changes to metallic zinc which is easy to do. Therefore, zinc can be efficiently removed without dissolving and fixing iron. For example, a high removal rate of 77 to 87% can be obtained. Therefore, scrap iron can be used as a raw material such as castings, which can contribute to energy saving, resource saving, and cost saving.

-Since the said reducing agent is carbon, the reduction effect | action of zinc oxide can be improved and the removal rate of zinc can be raised.
-By the addition amount of a reducing agent being 0.1-10 mass% with respect to zinc steel material waste, the reduction effect of zinc oxide can fully be exhibited and the removal rate of zinc can be raised further.

  The temperature of the zinc steel material scrap in the dezincification furnace 11 is maintained at 770 ± 50 ° C. at a temperature showing the iron magnetic transformation point, and the zinc in the dezincification furnace 11 is shown at a temperature showing the transformation point from α iron to γ iron. The temperature of the steel scrap is maintained at 910 ± 50 ° C. In this case, in addition to the above-described effects, the temperature can be equalized in the dezincification furnace 11.

-The pressure reduced in the entire period of separating zinc in the dezincification furnace 11 is set in the range of 81.25 to 101.15 kPa, so that zinc can be removed under reduced pressure, and the removal rate of zinc Can be further enhanced.

  -By setting the inside of the dezincification furnace 11 to a reducing atmosphere or an inert gas atmosphere, the influence of oxygen can be avoided and the reduction reaction of zinc oxide can proceed smoothly.

  When the zinc steel scrap reaches a temperature indicating the magnetic transformation point of iron or when it reaches a temperature indicating the transformation point from α iron to γ iron, each region such as the outer peripheral region and the central region in the dezincification furnace 11 By maintaining the temperature difference between the maximum temperature and the minimum temperature of the zinc steel material scraps in a narrow temperature range of 50 ° C. or less, soaking of the zinc steel material scraps can be further improved.

Hereinafter, although the embodiment will be described more specifically with reference to examples, the present invention is not limited to the scope of these examples.
(Reference Example 1)
In Reference Example 1, zinc steel scrap was put into the dezincification furnace 11 shown in FIG. 1, heated to the magnetic transformation point of iron in the air atmosphere, and reduction of zinc oxide contained in the zinc steel scrap was attempted. In this case, the temperature of each part in the dezincification furnace 11 was measured in order to equalize the temperature in the dezincification furnace 11. As a result, the bottom outer peripheral region A in the dezincification furnace 11 was 787 ° C., the bottom central region E was 769 ° C., the intermediate peripheral region B was 809 ° C., and the intermediate central region F was 770 ° C. The temperature difference ΔT in these regions was 40 ° C. The maximum zinc removal rate was 68%.

Further, the relationship between time (h) and temperature (° C.) in each of the above regions was measured, and the result is shown in FIG. From the results of FIG. 2, although a slightly irregular temperature increase was observed in the bottom center region E, the temperature increase was generally smooth and reached the magnetic transformation point (770 ° C.) in about 1 hour 30 minutes.
(Reference Example 2)
In this Reference Example 2, the relationship between the pressure (kPa) in the dezincification furnace 11 and the total zinc volatilization temperature (° C.) in a reducing atmosphere, an inert gas atmosphere or an air atmosphere is calculated by equilibrium calculation, and the result Is shown in FIG. As a result, in the reducing atmosphere and the inert gas atmosphere, the total zinc volatilization temperature was lower at the same pressure than in the air atmosphere. In FIG. 3, a solid line represents a reducing atmosphere, a one-dot chain line represents an inert gas atmosphere, and a dotted line represents an air atmosphere.
Example 1
40.00 kg of zinc steel material, 0.60 kg of 98% granular carbon (carburized material) (1.5% by mass with respect to zinc steel material) and 30.00 kg of return material are put into the dezincification furnace 11 shown in FIG. Then, heating was performed up to the A3 transformation point of iron in an air atmosphere, and zinc oxide contained in the zinc steel material was reduced. The pressure in the dezincification furnace was reduced to -0.15 kPa. The temperature was raised from room temperature to 760 ° C. for 30 minutes, and maintained at 760 ° C. for 45 minutes to control soaking, and maintained from 760 to 910 ° C. for 38 minutes and from 910 to 920 ° C. for 7 minutes.

As a result, the bottom outer peripheral region A in the dezincification furnace 11 is 908.2 ° C., the bottom central region E is 896.5 ° C., the intermediate peripheral region B is 908.2 ° C., and the intermediate central region F is 907.7 ° C. Met. The temperature difference ΔT between the highest temperature and the lowest temperature of the zinc steel material in these regions was 11.7 ° C., and the temperature of the zinc steel material in each region was within the range of 910 ± 50 ° C. The zinc removal rate was 89.9%. Further, the relationship between time (min) and temperature (° C.) in each of the above regions was measured, and the result is shown in FIG. From the results shown in FIG. 5, in the bottom outer peripheral area A and the middle outer peripheral area B, the temperature rise is slightly delayed as compared with the bottom central area E and the middle central area F, but the temperature rise is generally smooth. The test was completed in minutes. As can be seen from this graph, it was possible to sufficiently achieve soaking in the dezincification furnace 11.
(Example 2)
Into the dezincification furnace 11 shown in FIG. 4, 40.00 kg of zinc steel material, 0.32 kg of 98% granular carbon (carburized material) (0.78% by mass with respect to zinc steel material) and 30.00 kg of return material are charged, In a reducing atmosphere, heating was performed until the minimum temperature of the zinc steel material scrap in the furnace reached the temperature of the A3 transformation point, and the zinc oxide contained in the zinc steel material was reduced. The pressure in the dezincification furnace 11 was reduced to -0.51 kPa. The temperature raising method is 30 minutes from room temperature to 760 ° C., 33 minutes at 760 ° C., and temperature control is controlled, 17 minutes from 760 to 910 ° C. and 17 minutes at 910 ° C. and 23 minutes, temperature control is controlled. Furthermore, it hold | maintained at 910 degreeC for 17 minutes.

As a result, the bottom outer peripheral region A in the dezincification furnace 11 is 959.4 ° C., the bottom central region E is 951.8 ° C., the intermediate peripheral region B is 919.3 ° C., and the intermediate central region F is 923.2 ° C. Met. The temperature difference ΔT in these regions was 40.1 ° C., and the temperature of the zinc steel material in each region was in the range of 910 ± 50 ° C. The zinc removal rate was 94.0%. Furthermore, the relationship between time (min) and temperature (° C.) in each of the above regions was measured, and the results are shown in FIG. From the results shown in FIG. 6, the bottom outer peripheral region A and the bottom central region E showed similar temperature changes, and the middle outer peripheral region B and the middle central region F showed similar temperature changes. An increase was noted and the test was terminated in 120 minutes. As can be seen from this graph, it was possible to achieve soaking in the dezincification furnace 11.
(Example 3)
Into the dezincification furnace 11 shown in FIG. 4, 40.00 kg of zinc steel material, 0.32 kg of 98% carbon powder (carburized material) (0.78 mass% with respect to zinc steel material) and 30.00 kg of return material are charged, The zinc oxide contained in the zinc steel material was reduced by heating until the minimum temperature of the zinc steel material scrap reached the temperature of the magnetic transformation point in a reducing atmosphere. Further, the pressure in the dezincification furnace 11 was reduced to -0.45 kPa. The temperature raising method was controlled from the normal temperature to 760 ° C. by maintaining the temperature at a rate of 30 ° C./min for 24 minutes and at 770 ° C. for 51 minutes.

As a result, the bottom outer peripheral region A in the dezincification furnace 11 is 789.3 ° C., the bottom central region E is 789.6 ° C., the intermediate peripheral region B is 765.3 ° C., and the intermediate central region F is 739.9 ° C. Met. The temperature difference ΔT showed a minimum value of 49.7 ° C., and the temperature of the zinc steel material in each region was in the range of 770 ± 50 ° C. The zinc removal rate was 90.8%. Furthermore, the relationship between time (min) and temperature (° C.) in each of the above regions was measured, and the results are shown in FIG. From the results shown in FIG. 7, the temperature of the bottom outer peripheral region A is the highest, the temperature of the intermediate central region F is the lowest, and the temperatures of the intermediate outer peripheral region B and the bottom central region E indicate intermediate temperatures thereof, The temperature rose substantially smoothly. The temperature difference ΔT in the dezincification furnace 11 showed a peak after 25 minutes, and then changed within about 50 ° C. As can be seen from this graph, it was possible to achieve soaking in the dezincification furnace 11.
Example 4
Into the dezincification furnace 11 shown in FIG. 4, 40.00 kg of zinc steel material, 0.32 kg of 98% carbon powder (carburized material) (0.78 mass% with respect to zinc steel material) and 30.00 kg of return material are charged, Heating was performed in a reducing atmosphere until the minimum temperature of the zinc steel material scrap reached the temperature of the A3 transformation point, and the zinc oxide contained in the zinc steel material was reduced. Further, the pressure in the dezincification furnace 11 was reduced to -0.45 kPa. The temperature rising method is from normal temperature to 760 ° C. at a rate of temperature increase of 40 ° C./min for 23 minutes and at 760 ° C. for 12 minutes to control soaking, and from 760 to 910 ° C. at a rate of temperature increase of 15 ° C./min. The temperature was raised for 6 minutes and maintained at 910 ° C. for 14 minutes to control soaking.

As a result, the bottom outer peripheral region A in the dezincification furnace 11 is 942.0 ° C., the bottom central region E is 918.4 ° C., the intermediate peripheral region B is 912.5 ° C., and the intermediate central region F is 911.4 ° C. Met. The temperature difference ΔT in these regions is 30.6 ° C., and the temperature of the zinc steel material in each region is within the range of 910 ± 50 ° C., and the temperature difference between the regions can be suppressed, so We were able to plan. Furthermore, the relationship between time (min) and temperature (° C.) in each of the above regions was measured, and the results are shown in FIG. The results shown in FIG. 8 showed similar temperature increases in each region, and the test was completed in 55 minutes. The temperature difference ΔT in the dezincification furnace 11 showed a peak after 20 minutes, and then changed around 30 ° C. As can be seen from this graph, it was possible to achieve soaking in the dezincification furnace 11 in a short time.
(Example 5)
40.00 kg of zinc steel material, 0.32 kg of coke powder (0.78 mass% with respect to zinc steel material) and 30.00 kg of return material are charged into the dezincification furnace 11 shown in FIG. Heating was performed up to the A3 transformation point, and the zinc oxide contained in the zinc steel material was reduced. Further, the pressure in the dezincification furnace 11 was reduced to -0.45 kPa. The temperature rising method is from normal temperature to 760 ° C. at a rate of temperature increase of 40 ° C./min for 23 minutes and at 760 ° C. for 12 minutes to control soaking, and from 760 to 910 ° C. at a rate of temperature increase of 15 ° C./min. The temperature was raised for 25 minutes and maintained at 910 ° C. for 7 minutes to control soaking.

  As a result, the bottom outer peripheral region A in the dezincification furnace 11 is 959.4 ° C., the bottom central region E is 913.3 ° C., the intermediate peripheral region B is 954.8 ° C., and the intermediate central region F is 925.2 ° C. Met. The temperature difference ΔT in these regions is 46.1 ° C., and the temperature of the zinc steel material in each region is within the range of 910 ± 50 ° C., and the temperature difference between the regions can be suppressed and soaking can be achieved. It was. Furthermore, the relationship between time (min) and temperature (° C.) in each of the above regions was measured, and the results are shown in FIG. From the results shown in FIG. 9, the temperature of the bottom outer peripheral region A is the highest, the temperature of the intermediate central region F is the lowest, the temperatures of the intermediate outer peripheral region B and the bottom central region E indicate intermediate temperatures thereof, The temperature rose substantially smoothly. The temperature difference ΔT in the dezincification furnace 11 showed a peak after 20 minutes, and thereafter changed at about 40 ° C. As can be seen from this graph, it was possible to achieve soaking in the dezincification furnace 11 in a short time.

It should be noted that the embodiment described above can be modified and embodied as follows.
-Zinc steel scrap can be refined (pulverized) in advance, and a powdery reducing agent can be mixed therewith.

-As a dezincification furnace 11, it is also possible to use the thing of the structure provided with the induction heating part in the bottom part or center part.
・ When separating metallic zinc from galvanized steel scrap, heating to the magnetic transformation point for volatile separation of metallic zinc, followed by heating to the transformation point from α iron to γ iron for volatile separation of metallic zinc it can.

  -The reducing agent used in the present invention is replaced with a reducing gas such as carbon monoxide or methane, and the zinc oxide in the galvanized steel scrap is reduced by flowing the reducing gas into the dezincification furnace to reduce the zinc oxide in the zinc steel scrap. Separation can also be performed.

  -It is also possible to use the dezincification furnace 11 used by this invention as a pre-processing furnace of the conventional melting furnace which fuse | melts and processes a zinc steel material waste. In this case, the heat energy in the dezincification furnace 11 can be used for melting in the melting furnace, which is energy saving.

-When carrying out volatile separation of metal zinc, it can also comprise so that the pressure reduction degree in the dezincification furnace 11 may be raised and the separation efficiency of metal zinc may be improved.
Next, the technical idea that can be grasped from the embodiment will be described below.

  The temperature is maintained for a certain period of time when reaching a temperature indicating the magnetic transformation point of iron or a temperature indicating a transformation point from alpha iron to gamma iron. The method for separating zinc from galvanized steel scraps according to item 1. When comprised in this way, in addition to the effect of the invention which concerns on any one of Claims 1-6, equalization in a dezincification furnace can be achieved.

  When the temperature indicating the magnetic transformation point of iron is reached, the entire dezincification furnace is at or above that temperature, and when reaching the temperature indicating the transformation point from α iron to γ iron, at least one in the dezincification furnace The method for separating zinc from galvanized steel scrap according to any one of claims 1 to 6, wherein the portion is at or above the temperature. When comprised in this way, in addition to the effect of the invention which concerns on any one of Claims 1-6, the zinc isolation | separation from zinc steel material waste can be performed more efficiently.

  11: Dezincing furnace.

Claims (7)

In a method for separating zinc by heating zinc steel scrap,
In the dezincification furnace, in the presence of a reducing agent, induction heating of zinc steel scrap from the temperature showing the iron magnetic transformation point to the temperature showing the transformation point from α iron to γ iron, without melting and fixing the iron A method for separating zinc from galvanized steel waste, characterized in that zinc oxide contained in the galvanized steel waste is reduced and converted to metallic zinc, and the metallic zinc is volatilized and separated. The method for separating zinc from galvanized steel scrap according to claim 1, wherein the reducing agent is carbon. The method for separating zinc from zinc steel scraps according to claim 1 or 2, wherein the amount of the reducing agent added is 0.1 to 10% by mass with respect to the zinc steel scraps. The temperature of the zinc steel scrap in the dezincification furnace is maintained at 770 ± 50 ° C. at the temperature indicating the iron magnetic transformation point, and the zinc steel scrap in the dezincification furnace at the temperature indicating the transformation point from α iron to γ iron. The method for separating zinc from galvanized steel scraps according to any one of claims 1 to 3, wherein the temperature of is maintained at 910 ± 50 ° C. The pressure reduced in the entire period of separating zinc in the dezincification furnace is set in a range of 81.25 to 101.15 kPa. A method for separating zinc from galvanized steel scraps as described in 1. The method for separating zinc from galvanized steel scrap according to any one of claims 1 to 5, wherein the inside of the dezincification furnace is set to a reducing atmosphere or an inert gas atmosphere. When the zinc steel scrap reaches a temperature indicating the magnetic transformation point of iron or reaches a temperature indicating the transformation point from α iron to γ iron, the maximum temperature of the zinc steel scrap in each region in the dezincification furnace The method for separating zinc from galvanized steel scrap according to any one of claims 1 to 6, wherein a temperature difference from the minimum temperature is maintained within 50 ° C.

Images