JPH0551218A - Production of ferrite powder by spray roasting and its device - Google Patents

Abstract

PURPOSE:To produce a multliple oxide low in impurities, with the composition stabilized and having almost the same metallic elements as the raw material in one stage from the multicomponent raw material contg. a high-vapor pressure substance by spray roasting. CONSTITUTION:A liq. mixture of metal chlorides is spray-roasted to produce a ferrite powder consisting of multiple oxide fine particles, and the deviation of the Zn content of the powder is reduced. In this case, the particle size of the sprayed liq. droplets is controlled to <=200mum, and the droplets are cooled to <=400 deg.C within 10sec immediately after spray roasting to obtain the powder. The powder is held above the dew point and recovered. Consequently, the composition adjusting stage after roasting which has been carried out is omitted, the load of the dechlorination stage is reduced, the process is simplified, the cost is drastically reduced, and the quality is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ferrite powder by a spray roasting method and an apparatus therefor, and more specifically, a solution containing a chloride of a metal constituting ferrite is spray roasted to obtain a ferrite powder at a stretch. The present invention relates to a method of manufacturing a body and an apparatus thereof.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a complex oxide by using a spray roasting method, a mixed aqueous solution of a compound such as metal nitrate, chloride or alkoxide, or a mixed organic solution is directly sprayed into a combustion flame. There is a method of pyrolyzing and roasting. Furthermore, in a complex oxide containing a raw material having a relatively high vapor pressure, only raw materials having a low vapor pressure are mixed at a predetermined molar ratio, and then oxidatively roasted. As a method of adding and mixing in the form of an oxide powder and firing the mixture to form a composite oxide having a predetermined composition, the method is disclosed in JP-A-55-1.
Japanese Patent No. 44421 is known. In addition, JP-A 1-1
As is known from Japanese Patent No. 92708, a high-temperature high-speed gas stream containing little or no reducing substance and a mixed solution of a raw material metal chloride are spray-mixed to rapidly reach a predetermined roasting temperature. The so-called co-current roasting, in which the raw material and the decomposition products are entrained in parallel with the hot gas flow to decompose the metal chloride mixture while maintaining the same, the metal element ratio of the raw material is almost the same in one step. There have been proposed methods such as a spray roasting method and a method using a fluidized bed, which can obtain a composite oxide having a metal element ratio, a small amount of impurities, and a stable composition.

[0003]

However, in the above-mentioned JP-A-55-144421, the roasting and mixing, the re-roasting and the number of steps are increased, and the molecular state characteristic of spray roasting is increased. However, the method of spraying the aqueous solution directly into the flame causes the combustion flame to be rapidly cooled, resulting in an increase in impurities due to the formation of fine carbon particles and the formation of carbides. There are drawbacks such as non-uniformity of product quality due to generation and instability of flame. In addition, JP-A-1
In Japanese Patent Laid-Open No. 192708, re-chlorination of a high vapor pressure substance is performed because the influence of the droplet size during roasting on the component deviation and the heat history of the powder after roasting are not sufficiently followed. Also, there is a drawback that the deviation of zinc becomes large due to chlorination by adsorbed hydrogen chloride.

[0004]

In order to solve the above drawbacks, the present invention provides rapid quenching after spray roasting in one step even if a multi-component raw material containing a high vapor pressure substance is used.
An object of the present invention is to provide a spray roasting method and apparatus capable of reducing re-chlorination of zinc spinel in a high temperature chlorine gas and reducing ZnO deviation in recovered powder. The gist of the present invention resides in (1) a method of reducing deviation of Zn in a ferrite powder composed of fine composite oxide particles by spray roasting a mixed solution of a metal chloride, and a spray droplet diameter of 200 μm. The method for producing a ferrite powder by the spray roasting method, in which the temperature is set to the following, and immediately after the spray roasting, the roasted powder is cooled to 400 ° C. or lower within 10 seconds and the roasted powder after cooling is collected while keeping the dew point or higher, ( 2) In a ferrite powder manufacturing apparatus for reducing deviation of Zn in ferrite powder composed of fine composite oxide particles by spray roasting a mixed solution of metal chlorides, a flame burner is provided at the top of the roasting furnace main body. Is provided, the raw material spray nozzle surrounding the flame burner is a nozzle capable of spraying with a spray droplet diameter of 200 μm or less, and a quencher arranged continuously at the bottom of the roasting furnace main body is provided, Quencher After spray roasting, a quencher nozzle that can be rapidly cooled immediately after spray roasting is arranged on the exit side of the roasting furnace, in a circumferential direction, and is an apparatus for producing ferrite powder by spray roasting, as well as the roasting furnace body and the roasting furnace. Quencher placed close to the furnace body
In the apparatus for producing ferrite powder by spray roasting, a quencher nozzle that can be rapidly cooled immediately after spray roasting is arranged in the circumferential direction.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a conceptual diagram of the thermal history of particles during roasting in the present invention and the prior art. That is, Fe ₂ O ₃ , Mn
In the manufacturing process of a ferrite sintered body using a ternary complex oxide mainly containing O and ZnO, when roasting a mixed aqueous solution containing iron chloride, zinc chloride and manganese chloride, the time during roasting and It shows the relationship of particle temperature. As can be seen from this figure, if the atomized droplet size is large, the drying time at the ZnCl ₂ boiling point or higher at a particle temperature of 732 ° C. or more becomes long, and the ZnSpin ₂ gas scatters before the zinc spinel reaction proceeds. In addition, the zinc deviation increases. Further, in the co-flow roasting method, when the recovered powder is present in the high temperature chlorine and hydrogen chloride gas for a long time, the zinc spinel is re-salted, which increases the zinc deviation. Further, it was confirmed that, when the adsorbed hydrogen chloride was hydrated below the dew point after roasting and cooling, it rapidly chlorinated zinc. This is clearly shown in the conventional co-flow roasting method and Rusner method. That is, in the Lusner method, one having a larger atomized droplet diameter than that of the method of the present invention is used. In this case, at a particle temperature of 732 ° C. or higher and a ZnCl ₂ boiling point or higher, The time t ₃ becomes longer and the ZnCl ₂ gas scatters without reacting with the powdered iron oxide and manganese oxide before reaching the zinc spinel completion region at the particle temperature of 800 ° C., and after further roasting Even in the cooling process, if the time t ₃ is increased, the zinc spinel is re-chlorinated during that time, and eventually the zinc deviation greatly increases. Further, the same is true in the conventional cocurrent roasting method, and in comparison with the method of the present invention,
Since the atomized droplet size is large, the residence time until the completion of the ZnCl ₂ gasification zone and the zinc spinel reaction is long,
Therefore, before reaching the zinc spinel complete region, ZnC
L ₂ scatters as a gas, and zinc spinel is re-chlorinated even after cooling, which leads to an increase in zinc deviation although the zinc deviation is smaller than in the Lusner method.

Therefore, in order to prevent an increase in these zinc deviations, it is necessary to reduce the spray droplet size, cool immediately after roasting, and keep the recovered powder at a dew point temperature or higher. There is a need. In order to achieve these conditions, first, FIG. 2 shows the atomized droplet size. FIG. 2 is a curve diagram showing the relationship between the maximum particle size and the ZnO deviation of the liquid composition. As shown in this figure, it can be seen that the ZnO deviation of the liquid composition rapidly increases when the maximum particle diameter exceeds 200 μm. Therefore, in order to reduce the deviation, it was confirmed that the maximum particle size of spray droplets needs to be 200 μm or less. Next, FIG. 3 shows the cooling time after spray roasting, which is the greatest feature of the present invention. That is,
Figure 3 shows the time from spray roasting to quenching and the composition of Zn.
It is a linear diagram which shows the relationship with O deviation. As shown in this figure, it can be seen that the longer the time from spray roasting to quenching, the greater the ZnO deviation of the liquid composition increases in proportion thereto. Therefore, it is necessary to immediately cool to 400 ° C. or lower after spray roasting. It is essential that the cooling is completed within 60 seconds, preferably 10 seconds. Further, it is necessary to keep the recovered powder at a dew point temperature or higher.

An example of a device used to achieve these conditions is shown in FIG. Reference numeral 1 is a roasting furnace main body, and a furnace having a vertical cylindrical refractory lined therein is suitable. A quencher 2 is connected to the roasting furnace main body 1 and has a structure capable of being immediately cooled after roasting. On the other hand, a mixed solution of a raw material chloride is arranged by a raw material spray nozzle 3 so as to surround a flame burner-4 in the circumferential direction of the top of the roasting furnace main body 1. By thus arranging the flame burner 4 and the raw material spray nozzle 3 in a co-current manner, the aqueous solution from the raw material spray nozzle is not directly sprayed to the flame burner, so that the combustion flame is generated. It is not rapidly cooled, and the raw material mixed liquid is mixed with the burning flame in a cocurrent manner from around the flame burner. As a result, a high-speed gas flow for improving mixing is obtained, and the mixed liquid of the raw material chloride is sprayed from the spray nozzle 3 into the high-speed high-temperature gas in the furnace. The maximum particle size of the sprayed droplets at this time is 200 μm or less as described above, and preferably in the range of 5 to 150 μm. The particle size of the liquid droplet is a value at room temperature.

The sprayed mixed liquid is rapidly mixed with a high-temperature swirling airflow, and is kept at a predetermined reaction temperature comprehensively by the latent heat of vaporization and the heat of decomposition, whereby the metal salt is decomposed. The reaction temperature at this time is 600 to 1000 ° C., preferably 750.
It is performed at ˜900 ° C. If the temperature is lower than 600 ° C., it becomes difficult to crystallize ferrite into a spinel structure for the purpose and the residence time must be lengthened. If it is lengthened, zinc spinel will be re-chlorinated and the zinc deviation will increase. Also, 1
When the temperature exceeds 000 ° C, when the raw material contains a volatile substance, vaporization is fast, and the recombination of fine particles generated by decomposing in the gas phase is delayed, resulting in composition fluctuation of the final product and binding at the molecular level. There is a problem with poor sex.

On the other hand, the residence time is preferably as short as possible, as described above, 10 seconds or less, preferably 0.1 to 5 seconds. In this way, the mixture of the fine particles produced by the decomposition of the metal salt in the roasting furnace and the high temperature gas surrounds the quencher nozzle 5 in the top circumferential direction of the quencher-2 in the quencher-2 as in the roasting furnace. Water is ejected from the quencher nozzle 5 to be cooled, and the produced fine particles are separated from the gas by a cyclone and an electric dust collector (not shown) to be collected. At this time, in Quencher-2, if the adsorbed hydrogen chloride is hydrated below the dew point after cooling, zinc will be rapidly converted to chloride. In order to avoid this, the inside of the quencher-2 is maintained at a dew point temperature or higher, and hydrogen chloride is recovered by a conventional method and used as a recovered acid.

Still another embodiment of the present invention is shown in FIG.
FIG. 5 is basically the same as FIG. That is, as in FIG. 4, reference numeral 1 indicates a roasting furnace main body, a furnace in which a vertical cylindrical refractory is lined is used, and a quencher-2 is arranged in parallel with the roasting furnace main body 1 in parallel. This quencher-2
Is connected to the lower part of the roasting furnace main body 1 through a passage 6 at the lower part thereof, and a quencher nozzle 5 capable of rapid cooling immediately after spray roasting is arranged in the circumferential direction of the quencher-2 at the lower part of the quencher-2. It consists of an established structure. On the other hand, as shown in FIG. 4, the raw material spray nozzle 3 for spraying the chloride mixed liquid as the raw material is arranged so as to surround the flame burner 4 in the circumferential direction of the furnace top portion of the roasting furnace main body 1. Is the same. By arranging the flame burner 4 and the raw material spray nozzle 3 in parallel in this manner, the aqueous solution from the raw material spray nozzle is not sprayed directly to the flame burner. There is. Further, the produced fine particles after roasting are separated from the hot gas, and the fine particles are discharged from the lower part, while the hot gas passes through the passage 6 and the quencher nozzle 5 arranged in the lower circumferential direction of the quencher-2. The water spurts out and is immediately cooled,
It is recovered as hydrogen chloride from above.

[0011]

According to the present invention, the time from 800 ° C. is zinc spinel complete region temperature as shown in the spray roasting after Figure 1 t ₁
By rapidly quenching at a low cooling rate (t ₁ <t ₂ <t ₃ ), re-chlorination of zinc spinel in high temperature chlorine gas can be reduced, and therefore ZnO deviation in the recovered powder can be made extremely small. You can Further, by making the maximum diameter of atomized droplets smaller than those of the conventional co-current method and Lusner method, the particle temperature of 732 ° C. which is the gasification region of ZnCl ₂
Or more, and residence time to the spinel reaction is complete is as t ₁₁ shown in FIG. _{1 (t 11 <t 22 <} t 33) becomes extremely short, making it possible to reduce the amount of separation zinc as ZnCl ₂ gas Therefore, the deviation of ZnO in the recovered powder can be made extremely small similarly to the quench rate. Furthermore,
By keeping the powder at a temperature above the dew point after quenching, it is possible to prevent the hydrated zinc of hydrogen chloride below the dew point from being re-chlorinated, and therefore a metal oxide with a low HCl adsorption amount. Will be recovered.

[0012]

【Example】

Example 1 Using the roasting furnace shown in FIGS.
FeCl ₂ and MnCl ₂ and ZnCl ₂ were concentrated to 40% by concentrating FeCl ₂ at a concentration of 40% in a heat recovery tower, and Fe ₂ O ₃ : MnO: ZnO = 68.4: 27.8:
The aqueous solution adjusted to 3.8 (wt%) was sprayed as a solution having a maximum droplet size of 50 μm to 150 μm at room temperature using spray air. Roasting temperature is 800 ℃, 400 ℃
To 2 seconds and 10 seconds, and as a comparative example, 60 seconds and 4 hours. The results are shown in FIG. 3. In the comparative example having a quench time of 60 seconds and 4 hours, the deviation of zinc was significantly increased as compared with the method of the present invention, and particularly, zinc was hardly present in the powder left for 4 hours. .. As a result of analyzing the composition of the composite oxide obtained from the electric dust collector (EP) after quenching, the composition was Fe ₂ O ₃ : MnO: ZnO = 68.1:
27.7: 4.2 (wt%) was obtained. Example 2 Using the same production and raw material mixture as in Example 1, the maximum spray droplet diameters were changed to 127 μm, 165 μm, and 273 μm, and spraying was performed, and immediately after roasting at 800 ° C. roasting temperature, 400 in 2 to 8 seconds. The deviation of ZnO from the liquid composition in the recovered powder after quenching to ℃ was investigated and the results are shown in Fig. 2. The deviation of zinc increases with the increase of the maximum particle size, especially in the case of 273 μm exceeding 200 μm. The deviation of No. 2 increased sharply, and the composition of the ternary complex oxide could not be maintained, and the product was not put to practical use. Example 3 Using a device and a raw material mixture similar to those in Example 1, a spray droplet having a maximum diameter of 200 μm was sprayed, and immediately after roasting at 800 ° C. roasting temperature, 2 to 8 seconds up to 400 ° C. The recovered powder after quenching was collected by a cyclone or an electric dust collector at a dew point or higher and at 370 ° C., and at room temperature. As a result, the amount of HCl adsorbed was 370 or higher than the dew point.
In the case of collection at ° C, it was as small as 0.25%, and in the case of collection at room temperature, residual HCl of 0.95% was observed.

[0013]

As described above, compared with the conventional co-current method, the deviation of the recovered powder from the liquid composition of the high vapor pressure substance containing zinc is extremely small, and the residual hydrogen chloride and chloride are also reduced. It is also possible to reduce the load, and for that reason, the load of the conventional component adjustment process after roasting and dechlorination process is reduced,
Furthermore, the steps can be omitted, the cost can be greatly reduced, and the quality can be improved, and the practical effect is extremely remarkable.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of thermal history of particles during roasting according to the present invention and the prior art,

FIG. 2 is a curve diagram showing the relationship between the maximum particle size and the ZnO deviation of the liquid composition,

[Fig. 3] Time from spray roasting to quench and Z of liquid composition
Linear diagram showing the relationship with nO deviation

FIG. 4 is an implementation device showing an example of the present invention,

FIG. 5 is an implementation device showing yet another example of the present invention.

[Explanation of symbols]

 1 roasting furnace main body, 2 quencher, 3 raw material spray nozzle, 4 flame burner, 5 quencher nozzle, 6 passages.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tatsunori Sunagawa Inventor Tatsunori Sunagawa 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Co., Ltd. Technology Development Division (72) Inoue Souji 2-6 Otemachi, Chiyoda-ku, Tokyo -3 In Nippon Steel Co., Ltd. (72) Inventor Yoshitaka Yamana 1 Kimitsu, Kimitsu City, Chiba Prefecture In Japan Kimitsu Steel Co., Ltd. (72) Inventor, Shoichi Nagata 1 Kimitsu, Kimitsu City, Chiba Made in Japan (72) Inventor Yoshiaki Kinoshita 1-8-12 Hirayama, Hino-shi, Tokyo (72) Inventor Masakazu Ishikawa 5-14-14 Oananami Minami, Funabashi-shi, Chiba

Claims (3)

[Claims] 1. A method of reducing the deviation of Zn in a ferrite powder composed of fine composite oxide particles by spray roasting a mixed solution of metal chlorides to obtain a spray droplet diameter of 200 μm.
m or less and 40 within 10 seconds immediately after spray roasting
A method for producing a ferrite powder by a spray roasting method, which comprises cooling to 0 ° C. or lower and recovering the roasted powder after cooling while maintaining the dew point or higher. 2. In a ferrite powder manufacturing apparatus for reducing deviation of Zn in ferrite powder composed of fine composite oxide particles by spray roasting a mixed solution of metal chlorides, a flame burner is provided at the top of a roasting furnace main body. -A burner is provided and the flame burner
The raw material spray nozzle surrounding the
A nozzle that can be sprayed below is provided with a quencher that is continuously provided at the bottom of the roasting furnace body. An apparatus for producing a ferrite powder by a spray roasting method, which is arranged in a circumferential direction. 3. A ferrite powder manufacturing apparatus for reducing deviation of Zn in ferrite powder composed of fine composite oxide particles by spray roasting a mixed solution of metal chlorides, and a flame burner is provided at the top of a roasting furnace main body. -A burner is provided and the flame burner
The raw material spray nozzle surrounding the
The nozzle capable of spraying below, the roasting furnace main body and the quencher arranged in proximity to the roasting furnace main body are connected at the bottom,
An apparatus for producing ferrite powder by a spray roasting method, characterized in that a quencher nozzle capable of rapid cooling immediately after spray roasting is arranged in the lower part of the quencher in the circumferential direction.