JPH0620821A - Manufacture of mn-zn ferrite raw oxide - Google Patents

Abstract

(57) [Summary] [Purpose] A raw material for Mn-Zn ferrite in which zinc chloride is prevented from evaporating from a chloride mixed aqueous solution containing chlorides of iron, manganese and zinc, and zinc oxide is uniformly mixed. Produce an oxide. [Structure] A chloride mixed aqueous solution containing chlorides of Fe, Mn and Zn is sprayed in a heating atmosphere so that the maximum history temperature of the obtained intermediate heating body is lower than the boiling point of Zn chloride, The first step of removing water to form an intermediate heating body, and heating the intermediate heating body to a temperature lower than the boiling point of the chloride of Zn to oxidize and roast the mixed oxide of Fe, Mn, and Zn. The second step is to obtain. In the second step, the oxygen content of the heating atmosphere is 15 vol% or more, and the temperature is 600.
It is preferable that the temperature is not higher than ° C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a raw material oxide for Mn-Zn ferrite.

[0002]

Mn-Zn ferrite is widely used as a high frequency soft magnetic material. The raw material powder used for the molding is Fe, Mn and Zn, which are the main constituent elements.
After mechanically mixing the oxide powder of, heat treatment (calcination),
The crushed one is most commonly used.

On the other hand, a mixed oxide powder obtained by preparing Fe, Mn and Zn as a chloride mixture mixed aqueous solution and spray-baking the aqueous solution has more constituent elements than those obtained by mixing each oxide powder. Since it is mixed more uniformly, it has advantages such as high magnetic characteristics. However, the method of spray roasting a chloride-mixed aqueous solution has a problem that ZnCl ₂ having a high vapor pressure evaporates during roasting, resulting in a low Zn yield and a compositional deviation. Note that ZnO, Zn having a low vapor pressure was replaced with ZnCl ₂ as the Zn raw material.
Even if (OH) ₂ or ZnCO ₃ is used, the Zn compound dissolves to form ZnCl ₂ , so the problem of evaporation during spray roasting cannot be solved.

Then, as a method for solving this problem,
It has been proposed to mechanically mix ZnO powder with a mixed oxide obtained by spray roasting a chloride mixed aqueous solution containing only Fe and Mn to form a forming raw material powder (Japanese Patent Publication No. 63-177).
76). However, in this method, since ZnO mechanically mixes the powder, the mixing of ZnO must be non-uniform.

A molding raw material obtained by reheating a mixed oxide obtained by spray roasting a chloride mixed aqueous solution containing only Fe and Mn for desalting, and mechanically mixing ZnO powder therewith. The powder is promising and promising because it has a lower risk of defects during firing as compared with the method of Japanese Patent Publication No. 63-17776, but the non-uniformity of ZnO mixing has not been solved.
(JP-A-2-271923).

Also, in these two methods, spray roasting is carried out with a chloride mixed aqueous solution containing only Fe and Mn.
Zn from a chloride mixed aqueous solution containing e, Mn and Zn
It does not directly yield a mixed oxide in which the oxides of Fe, Mn and Zn are uniformly mixed without lowering the yield of. As described above, a mixed oxide in which Fe, Mn and Zn oxides are uniformly mixed can be directly obtained from a chloride mixed aqueous solution containing Fe, Mn and Zn without lowering the Zn yield. The reality was that there was no means.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by reducing the Zn yield from an aqueous solution containing chlorides of Fe, Mn and Zn.
Moreover, Mn-Zn in which oxides of Fe, Mn, and Zn are uniformly mixed is intended to produce a raw material oxide for ferrite.

[0008]

The present invention relates to Fe, Mn and Z.
A chloride mixed aqueous solution containing a chloride of n is sprayed in a heating atmosphere so that the maximum history temperature of the obtained intermediate heating element is lower than the boiling point of the chloride of Zn to remove water in the mixed aqueous solution and perform intermediate heating. The first step of forming a body and the intermediate heating body are Z
A raw material oxide for Mn-Zn ferrite, which comprises a second step of heating at a temperature lower than the boiling point of the chloride of n to perform oxidative roasting to obtain a mixed oxide of Fe, Mn and Zn. In the second step, it is preferable that the oxygen content of the heating atmosphere is 15 vol% or more, and the heating temperature is 600 ° C. or less.

[0009]

The present invention will be described in detail below. 1st of the manufacturing method of the raw material oxide for Mn-Zn ferrite of this invention
In the step of, a chloride mixed aqueous solution containing chlorides of Fe, Mn and Zn is sprayed in a heating atmosphere so that the highest hysteresis temperature of the obtained intermediate heating body is a temperature lower than the boiling point (732 ° C.) of ZnCl _2. It is necessary to remove the water content of the mixed aqueous solution to obtain an intermediate heating body.

Generally, most of the thermal energy required for oxidative roasting to obtain a metal oxide from a metal chloride solution is used for evaporation of water and removal of crystal water. Therefore, in this step, heat is efficiently transmitted to the prepared chloride mixed aqueous solution, the evaporation of water and the removal of the crystal water of chloride of Fe, Mn and Zn are quickly completed, and moreover Fe, Mn and Zn are uniformly dispersed. To mix with the above, the aqueous solution is sprayed into a heated atmosphere.

At this time, the minimum amount of heat to be transferred is the latent heat of vaporization of water in the aqueous solution and the sensible heat of heating to the vaporization temperature.
It is necessary that the total amount of the latent heat required for releasing the water of crystallization of the chlorides of Fe, Mn, and Zn and the sensible heat for heating the chlorides of Fe, Mn, and Zn to the temperature of removing the water of crystallization. When the amount of heat transfer is less than the above total amount, a large amount of heat is further added to the obtained intermediate heating body by another heating furnace having a lower heat transfer efficiency than spray heating because of insufficient release of chloride crystal water. There is a need. Therefore, in order to effectively utilize the high transfer efficiency of the spray heating furnace, it is necessary to transfer more heat than the above total amount by spray heating. In other words, by spray heating, evaporation of water of the chloride mixed aqueous solution and Fe, M
Complete removal of water of crystallization of n and Zn chlorides.

When the amount of heat transferred exceeds the above minimum amount,
The temperature of the intermediate heating element rises, and the anhydrous chloride in the intermediate heating element is oxidized and roasted to the respective oxides.
_The intermediate heating element containing _{2 has} a boiling point of ZnCl ₂ (73
When heated to a temperature of 2 ° C. or higher, ZnCl ₂ evaporates and the Zn yield decreases. Therefore, the maximum temperature (maximum hysteresis temperature) encountered by the intermediate heating element obtained by spraying the aqueous solution in the heating atmosphere must be lower than the boiling point of ZnCl ₂ .

The amount of heat to be transferred is controlled so that the maximum crystallization temperature of the intermediate heating element is completely removed by the water of crystallization of chloride.
Controlling from around ℃ to below 732 ° C. which is the boiling point of ZnCl ₂ can be performed by changing the temperature in the heating furnace, the droplet size, the droplet flight distance, and the like.
The maximum history temperature of the intermediate heating element is lower than the maximum temperature in the heating furnace, and by making the droplet size small and the droplet flight distance long, it is possible to approach the maximum temperature in the heating furnace. on the other hand,
The heat transfer efficiency can be increased by increasing the temperature in the heating furnace.

Usually, the temperature in the spray heating furnace is 300 to 10
00 ° C., droplet diameter is several μm to 1 mm, droplet flight distance is 1
The maximum history temperature of the intermediate heating element is 20 m
In order to reliably control the temperature between 0 and 732 ° C., the heating furnace temperature is set within the same range as the target temperature (less than 200 to 732 ° C.), preferably in the high temperature part (730 to 500 ° C.). The droplet diameter may be small (several to several tens of μm), and the flight distance may be long (about 3 to 10 m) so that the maximum history temperature of the intermediate heating body and the heating furnace maximum temperature coincide with each other.

On the other hand, in order to increase the heat transfer efficiency, the heating furnace temperature is set to a higher temperature (600 to 1000 ° C.), the droplet diameter is increased (several tens to several hundreds of μm), and the flight distance is shortened (1
However, the control becomes difficult. Actually, it is difficult to measure how many times the intermediate heating body has been heated, that is, how many times the maximum hysteresis temperature has been reached.Therefore, the operating parameters are determined by simulation calculation and experience, and the product analysis is performed. Check the removal of chloride water of crystallization and the evaporation of ZnCl ₂ and correct and determine the operating parameters.

As the chloride mixed aqueous solution to be sprayed, for example, pure water in which chlorides of Fe, Mn and Zn are dissolved is used. Instead of ZnCl ₂ , ZnO and Zn (OH) ₂ are used.
And ZnCO ₃ , these Zn compounds are Fe
Since it can be dissolved in an aqueous solution of Cl ₂ and MnCl ₂ to form ZnCl ₂ , it can be used in the same manner as ZnCl _2, and in particular, a metal or an alloy can be added to a waste solution of pickling which is generated in a large amount at an iron mill if necessary. Further, the dissolved product can be preferably used economically.

The weight ratio of Mn, Zn and Fe in the chloride mixed aqueous solution is determined by the composition of the roasted oxide to be produced, but the metal ratio is usually Mn: 5 to 70 wt%, Z
The composition is n: 1 to 50 wt% and the balance Fe. The heating atmosphere in which the chloride mixed aqueous solution is sprayed is preferably an oxygen-containing atmosphere in order not only to remove water but also to oxidize and roast the chloride, so that heating can be performed economically. Oxygen-containing high-temperature gas produced by burning a fuel containing hydrocarbons (usually: oxygen content 2-10 v
ol%) is preferably used.

In the first step of the present invention, Fe, M
Since the water content of the chloride mixed aqueous solution containing the chlorides of n and Zn is removed by spray heating whose temperature control is easy, not only the yield of Zn in the obtained intermediate heating element is good, but also The uniformity of mixing is also good. In the second step of the production method of the present invention, it is necessary to further heat the intermediate heating body at a temperature lower than the boiling point of ZnCl ₂ to perform oxidative roasting.

As described above, the first step of the present invention uses a spray heating furnace to evaporate water and chlorinate Fe, Mn and Zn when the raw material droplets or their heating bodies fly in a heating atmosphere. It is carried out to remove the water of crystallization of the product to obtain an intermediate heating body. Therefore, since the intermediate heating body is not sufficiently oxidized and roasted, in order to complete the oxidation roasting, the second step is performed. It is necessary to heat. However, when the heating temperature is above the boiling point of ZnCl _2, the yield of Zn for the ZnCl ₂ evaporation decreases. Therefore, the heating temperature in the second step needs to be lower than the boiling point of ZnCl ₂ .

Further, it is preferable that the oxygen content of the heating atmosphere in the second step is reasonably high. Because the purpose of the first step is to remove water, it was not affected by the oxygen content, but in the second step, the oxidation reaction is performed, so that the oxygen content is preferably high. Also,
In consideration of heating cost, when using a high temperature gas containing oxygen (usually: oxygen content of 2 to 10 vol%) produced by burning a fuel containing hydrocarbon, etc., introduce air or the like, The oxygen content of 15 vol% or more is preferable because the roasting reaction can be efficiently performed.

Furthermore, in order to substantially completely eliminate evaporation of ZnCl ₂ is the vapor pressure of ZnCl ₂ is atmospheric pressure 1/1
It is preferable that the heating temperature in the second step is 600 ° C. or lower at which the temperature becomes 0. Although not particularly limited, the oxidation roasting can be efficiently completed by setting the heating temperature in the second step to 400 ° C. or higher.

Usually, the heating time of the second step is 0.5 to
It takes about 12 hours. In the heating of the second step, a heating device that can easily and accurately control the temperature and atmosphere is used. This heating device may be of a type that does not have a chance of heating for only a few seconds, such as a spray heating furnace, and a tunnel furnace or a rotary kiln can be preferably used.

As described above, in the production method of the present invention, the spray heating furnace is used as the first step for efficient heating for the purpose of removing the water content of the chloride mixed aqueous solution, and the precision of Zn yield As a second step, a different type heating furnace that is not a spray method is used for the temperature control. As described above, the maximum hysteresis temperature of the intermediate heating body in the first step of the present invention and the heating temperature in the second step are both ZnCl ₂
Below the boiling point (732 ° C.) of As a result, a high Zn yield can be obtained.

However, it may be necessary to increase the average particle size of the powder in order to improve the formability of the oxide by pressing. In that case, the mixed oxide of Fe, Mn, and Zn containing 0.2 wt% or less of chlorine is obtained by the heating in the second step of the present invention, and then the heating in the second step is further performed. It can be calcined at a temperature higher than the temperature. After ZnCl ₂ is almost completely oxidized as a result of the heating in the second step (to the extent that it contains chlorine of 0.2 wt% or less), ZnCl _{2 which} is liable to evaporate is substantially absent, so that the temperature is further increased. ZnCl ₂ even when heated to
There is no substantial reduction in Zn yield due to the evaporation of.

As described above, according to the present invention, FeCl ₂ ,
To produce a raw material oxide for Mn-Zn ferrite from a chloride mixed aqueous solution containing MnCl ₂ and ZnCl ₂ without lowering the Zn yield, with good thermal efficiency, and with good ZnO mixing uniformity. You can next,
A preferred method for producing Mn-Zn ferrite using the mixed oxide obtained by the production method of the present invention will be described.

The raw material oxide obtained by the production method of the present invention is
In the manufacturing method of the used Mn-Zn ferrite, the present invention is used.
Oxidation of raw material for Mn-Zn ferrite obtained by the manufacturing method of
One or more products, or known products for adjusting components
Fe, a raw material for ellite₂ O ₃ , Mn₃ O_Four And ZnO
One or more of these are crushed and mixed for use. This mixing is a machine
This is done mechanically and is usually a dry or wet bow.
Lumil and attritor can be preferably used. like this
The contents of Mn, Zn and Fe thus obtained are MnO, Z
nO and Fe₂ O₃ Converted to
The ratio is 30 wt%, 2 to 15 wt% and the balance.

The mixed oxide that has been pulverized and mixed is
A maximum of 700 to 11 in the atmosphere of air, nitrogen, a mixed gas of these, or combustion exhaust gas of hydrocarbon fuel.
It is preferable to calcine by heating at 00 ° C. A rotary kiln or the like can be preferably used for calcination. The calcinated mixed oxide is mixed with trace additives at the same time as crushing,
Furthermore, after molding, it is baked.

As the trace additive, a trace amount of powder such as SiO ₂ , CaO and Nb ₂ O ₅ is added to improve the magnetic characteristics. The addition amount of these trace additives is, as is known,
0.3 wt% or less, 0.5 wt% or less, and 0.7, respectively
It is about wt% or less, and the added amount varies depending on desired magnetic characteristics. The mixed pulverized powder thus obtained is usually
It has an average particle size of about 0.3 to 2 μm.

The mixed pulverized powder usually contains 0.1 to 1 wt.
% Molding agent represented by PVA or 0.01 to 1
A lubricant represented by zinc stearate of about wt% is mixed and granulated to about -30 mesh to obtain a forming raw material. The molding raw material is usually molded into a desired shape under a pressure of about 0.1 to ² t / cm ² . The molded product is usually up to 120 in air, nitrogen, or a mixed gas thereof.
Hold at about 0 to 1350 ° C. and bake.

[0030]

The present invention will be described below with reference to examples. Use Example 1] Pure water and FeCl _2, MnCl ₂ and 4 kinds of zinc raw material (described in Table 1-3), 1 during liter Fe in metal units 100 g, the Mn 33 g, a Zn 1
A raw material liquid containing 3 g was prepared.

This raw material liquid was sprayed into the spray heating furnace at a supply rate of 1 liter / h. Spray heating furnace has an inner diameter of 300 mm
The cylindrical core tube (1) (which is installed vertically) can be uniformly heated by an electric furnace over a length of 1500 mm from the outside, and the atmosphere can be controlled by adjusting the amount of air flowing into the core tube. In addition, a two-fluid spray nozzle was arranged immediately above the soaking zone in the core tube so that raw material liquid droplets with controlled average diameter could be sprayed. Tables 1 to 3 show the core soaking temperature, the average droplet diameter, the maximum history temperature, and the oxygen content in the core tube as conditions for the spray heating (first step).

Zn of the obtained spray-heated powder (intermediate heating body)
The yield, the removal rate of water of crystallization, and the roasting reaction rate are also shown in Tables 1 to 3. As for the yield of Zn, it is empirically known that the yield of Fe is almost 100%.
It was relatively calculated from the chemical analysis value of n. The crystal water removal rate was also calculated by relative comparison with Fe from elemental analysis results, assuming that the chlorides of Fe and Mn are tetrahydrates and the chlorides of Zn are anhydrous. Further, the ratio of the amount of chlorine removed to the amount of chlorine added was determined from the chlorine analysis value by relative comparison with Fe, and the 1% digit of the ratio was rounded up to 0 and 5 to obtain the roasting reaction efficiency.

The obtained intermediate heating body was heated in the second step by an external heating type rotary kiln using an electric furnace having a cylindrical core tube having an inner diameter of 50 mm and a length of 700 mm. The process conditions and the properties of the obtained mixed oxide are shown in Table 4. Example 1 of the present invention in which only the temperature condition of the first step was changed
3 to Comparative Examples 1 and 2, when the temperature is too low as 300 ° C. (Comparative Example 1), the droplets are not sufficiently heated and the crystal water is not sufficiently removed (the crystal water removal rate is 55
%), And it cannot be said that the heating in the first step is efficient, which is a problem. On the other hand, when the temperature is too high as 800 ° C. (Comparative Example 2), the heating becomes excessive, and not only the crystallization water removal (the crystallization water removal rate is 100%) but also the roasting progresses considerably (the roasting reaction efficiency is 95%). However, the evaporation of ZnCl ₂ (boiling point 73
2 ° C.), the Zn yield in the stage of the intermediate heating body is 75.
There is a drawback that it becomes as low as%. On the other hand, suitable temperature ranges (respectively 400, 55
When heated at 0,650 ° C., water of crystallization can be removed efficiently (removal rate of water of crystallization is 100%), and a high Zn yield of 99 to 100% can be obtained at the stage of the intermediate heating body. By the way, the difference in the heating temperature of 400 to 650 ° C. appears as the difference in the roasting reaction rate of 10 to 55%, and the higher roasting reaction rate is better as long as there is no problem in the Zn yield. Furthermore, by performing the second step of the present invention on the intermediate heating body of the present invention, the roasting reaction can be completed while maintaining a high Zn yield (97 to 98%), and 0.04 to 0 can be obtained. A mixed oxide having a low chlorine content of 0.06 wt% was obtained.

The temperature of the first step mentioned here is the core soaking temperature of the heating furnace, and on the contrary, the number of times the intermediate heating body actually has a history is based on the characteristics of the intermediate heating body. Infer. The maximum history temperature of the intermediate heating body is at least lower than the maximum temperature of the heating furnace, and the difference between the maximum history temperature and the heating furnace temperature is smaller as the droplet diameter is smaller. From the above results, as in Examples 1 to 3 of the present invention, the highest history temperature of the intermediate heating element is ZnCl 2.
The boiling point of ₂ must not exceed 732 ° C (furnace temperature is 732
It can be said that a high Zn yield can be secured when the temperature is lower than (° C.), and the higher the temperature within that range, the more water of crystallization can be removed, and more efficient heating can be performed.

However, even when the furnace temperature is 800 ° C., which is higher than the boiling point of ZnCl ₂ as in Example 7 of the present invention, the droplet diameter is large and the maximum history temperature is much lower than the heating furnace temperature. , If it is lower than the boiling point of ZnCl _2, a high Zn yield is obtained. Further, the present invention is not limited to ZnCl ₂ as a Zn raw material and can be widely applied, that is, ZnO use examples of the present invention examples 4, 15 to 17 and the present invention examples 5 and 6
It is clear from the use example of ZnCO _{3 in} Example 6 and the use example of Zn (OH) _{2 in} Example 6 of the present invention.

Regarding the effect of the condition of the second step,
This is apparent from Examples 8 to 17 of the present invention and Comparative Examples 3 to 5. That is, the oxygen content in the second step is 6
As the oxygen content increased to vol% (invention example 8), 15 vol% (invention example 9) and 20.6 vol% (invention example 2), the chlorine content of the final mixed oxide was 0.1 w.
t% (invention example 8), 0.05 wt% (invention example 9),
It is as low as 0.04 wt% (invention example 2), which is preferable. Especially, 15 vol% less than 0.1 wt% chlorine
The above oxygen contents are preferable.

On the other hand, the oxygen content in the first step was changed to 6 vol% (invention example 2) and 20.6 vol% (invention example 10), but the roasting was completed at the end of the first step. The reaction rates are 30% (invention example 2) and 35% (invention example 1).
0), but the chlorine content of the final mixed oxide is 0.04 wt% (Example 2 of the present invention), 0.05 wt%
The former is economically preferable in that exhaust gas obtained by burning hydrocarbons and the like can be used as it is, not much different from (Invention Example 10). However, it is not limited.

Regarding the temperature of the second step, Zn
Inventive Examples 11 to 14 and Comparative Example 3 using Cl ₂
Inventive Examples 15 to 17 using ZnO and Comparative Example 5
In the case of heating above 732 ° C., which is the boiling point of ZnCl ₂ (Comparative Examples 4 and 5), the Zn yields are remarkably low and are 65% and 72%, respectively. By heating at a temperature lower than the boiling point of ZnCl ₂ for the first time, 91-99%
The roasting reaction can be completed while ensuring a high Zn yield, and as a result, a mixed oxide having a low chlorine content of 0.03 to 0.1 wt% is obtained (Invention Examples 11 to 1).
7). However, when the heating temperature is 600 ° C. or higher (Invention Examples 11 and 15), evaporation of a small amount of ZnCl ₂ cannot be prevented, and the Zn yields decrease to 91% and 92%, respectively. The temperature is preferably 600 ° C. or lower. On the other hand, when the heating temperature is too low at 390 ° C. (Comparative Example 3)
Is not preferable because a mixed oxide containing 0.5 wt% of chlorine cannot be obtained and the roasting reaction cannot be completed.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

[Effects of the Invention] A raw material oxide for Mn-Zn ferrite in which zinc is uniformly mixed from an aqueous chloride mixed solution containing chlorides of iron, manganese and zinc, without causing evaporation due to heating during the manufacturing process. Can be manufactured.

Front page continuation (72) Inventor Satoshi Nariya 1 Kawasaki-cho, Chuo-ku, Chiba City Technical Research Division, Kawasaki Steel Co., Ltd. (72) Hideaki Inaba 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Technical Research Division Within

Claims (3)

[Claims] 1. A mixed aqueous solution of chloride containing chlorides of Fe, Mn and Zn is sprayed in a heating atmosphere so that the maximum history temperature of the obtained intermediate heating element is lower than the boiling point of the chloride of Zn. The first step of removing water in the intermediate heating body to form an intermediate heating body, and the intermediate heating body is heated to a temperature lower than the boiling point of the chloride of Zn to oxidize and roast the Fe, Mn and Zn.
2. The method for producing a raw material oxide for Mn—Zn ferrite, comprising the second step of obtaining the mixed oxide of. 2. The method for producing a raw material oxide for Mn—Zn ferrite according to claim 1, wherein the oxygen content of the heating atmosphere in the second step is 15 vol% or more. 3. The Mn—Z according to claim 1, wherein the heating temperature in the second step is 600 ° C. or lower.
A method for producing a raw material oxide for n-ferrite.