NL8204778A - METHOD FOR PREPARING FERROMAGNETIC OXIDES - Google Patents

Description

+. * ->,. VO 4002

Process for preparing ferromagnetic oxides.

The invention relates to ferromagnetic oxides and a method for the preparation thereof. As a result of the invention, the amount of energy required to make ferrites is greatly reduced compared to conventional methods. In conventional methods, oxides of manganese, nickel, magnesium, zinc, cobalt 2+ and other elements of the valence 2+ (referred to below as H) and / or salts of these elements are mixed with iron oxides. These mixtures are then converted to ferrites by roasting.

The oxides of these elements are usually pretreated to have the appropriate chemical composition and particulate properties for the production of ferrite. A great deal of energy is required for this pre-treatment.

Much has been published about the various conventional manufacturing methods for ferrite. Below is indicated how much energy can be saved in the present process compared to a conventional process.

Usual process:

MnSO 7.5%

MnO

2FeS04 17.5% -> 20 H20 7.5% oil Fe203 N-r / 1 kg n-vw (A) (B), 1 kg of oil is required to convert (A) to (B).

Method according to the invention:

MnSO.

MnO

25 Fe203 -> HO ° lie Fe-0

^ 0.3 kg yYY

(A) (B) in this case, therefore, only 300 g of oil is required for the conversion of (A) to (B). Thus, under comparable conditions, 30 700 g of oil can be saved.

8204778 •% -2-

The invention thus provides a strong oil saving.

In the invention, natural iron oxides, iron sulfate and / or iron oxide can be used as by-products of other processes as the main starting materials for ferrite. Oxides of other 5 elements are also added to this starting material. The oxides of these other elements must be oxides such that they can be decomposed during the roasting required for conversion to ferrite. To achieve the required magnetic properties of the ferrite, appropriate amounts of oxides of iron, manganese, nickel, magnesium and cobalt must be added to the starting material.

The total mixture is converted into a ferrite core after sintering. The invention is explained in more detail below.

For making ferrite, the usual recipe is as follows:

Usual recipe: (A) f®2 ° 3: ^ mol · * (B) oxide mixture of single or a combination of 2+ M: 50 mol%.

The amount of Fe2 ° 3 in this recipe is about 70% by weight.

The in this recipe is usually obtained from iron sulfate or iron chloride. Much energy is required to decompose Fe 2 SO 4 or FeCl 3 to Fe 2 O 3. In addition, much purification costs are required in purifying the offgas released when decomposing FeSO and FeCl.

1 A 2+

If oxides of M can be used as starting materials for this recipe without further chemical treatment, this means strong energy savings and clear waste gas savings. However, these types of oxides are not very reactive. It is therefore necessary to mix them well to improve the reactivity.

This mixing also costs extra energy. The preparation of oxides of 2+ 2+ M requires a pyrolysis vein M solutions obtained by extraction of natural ores. This also costs a lot of energy, while the resulting exhaust gases have to be purified. Moreover, such M oxides are not very reactive. In the present process, 2+ 2+ becomes a solution of M salts without conversion of these M salts 82 0 4 7 7 8 F ......: -. = 1: - * '' -3- 2 + in M oxides used directly as starting material. This saves a lot of energy and eliminates the difficult purification of the exhaust gases.

2+

In addition, the solutions of M salts are more reactive, which contributes to reducing mixing costs and permitting a lowering of the roasting temperature. These advantages mean a great total energy saving. In the invention, only energy and gas purification are required in toasting.

In the invention, to obtain the necessary oxides, a mixture of the following materials (1), (2) and (3) is roasted in the form of a suspension, solid particles or granules at an appropriate temperature.

(1) Saline

Natural ores containing one or more of the elements Mn, Ni,

Co, Mg, Cu, Fe, Ca, Al, Ti and V in a certain percentage, 2+ 15 or metal scrap containing M are put in an acid solution. All these elements are extracted from the ores or the metal chips in the acid are dissolved.

(2) Natural iron oxide ore (3) Iron oxide formed as a by-product of certain processes. The following describes how to remove the impurities from saline (1), the iron ore oxide (2) and the iron oxide as a by-product (3).

Refining the saline

Required elements such as Mn, Fe, Co, Ni, Cu, and Zn can be separated by introducing Oj or H 2 S gas into solution (1) or by adjusting pH values. Depending on the refining operations used, such as recrystallization, filtration, absorption, dewatering or a combination thereof, these must be repeated such that the required purity of the chemical constituents is achieved.

Refining of Iron Ore Oxide

SiO4 and the like in natural ore material hematite are removed to a percentage below 0.3% by magnetic separation or by flattering.

8204 778 ---------------------——; --------- --------- 35 β -4-

Iron oxide refining

Usually, a solution is formed upon the brining of steel neutralized and then hydrogen gas is blown therein. To remove impurities, operations such as recrystallization and filtration are repeated. The resulting salt is then roasted to iron oxide. The following chemicals (4) are produced from these types of refining operations.

Chemicals 2+

Iron oxide, oxides of M, ion hydroxides, crystals of acid 2+ 10 salts with M ions. An appropriate amount of ammonium sulfate solution is added to an appropriate molar amount of these chemical compounds (4) until a suspension (5) is formed.

The compounds in this suspension (5) are then processed to ferrite via the following grating treatments: a) spray grills b) atomization spray grills c) smooth grilling d) roasting in a rotary oven.

Before roasting in a rotary oven, the slurry 20 must be concentrated to form solid particles or granules. These kinds of particles and / or granules are placed in the rotary oven. In order to concentrate the suspension in a known manner, further chemical material can be added to this suspension.

It is also a good method of spraying the suspension over the material in a fluid bed. Desirably, the flowable agent consists of roasted oxides having a composition similar to that of the slurry. It is one of the advantages of the invention that iron oxide can be mixed well with the salt solution in this recipe. Since the remainder, unlike the iron oxides (usually 50 mole%), consists of saline and solid particles, the iron oxide is mixed much better with the solution than it would with dry particles. For further mixing, if necessary, a ball mill and a mixing device can be used. The better the mixing, the less energy is required, because this allows for roasting at a lower temperature.

820 4 778 ______________ F -: -: 2+ -5- lr * '

Usually Zn is easily vented with the vent 2+ gas during spraying or atomizing spraying. This discharge of Zn changes the ferrite composition, which is unfavorable for the ferrite properties. The table below shows how this discharge of 2+ 5 Zn ions can be minimized during toasting.

During the grating treatments, an acidic salt of zinc ion is oxidized to fine ZnO particles. However, the acid-reacting salt of zinc (for example ZnCl2) in the slurry evaporates due to the causes described below: · During the roasting, the temperature of the grate flame and the product must be approximately 1000 ° C, although the temperature of the fire flame is approx. 1700 ° C.

These 2nci2-4partj.s are enclosed within fine but agglomerated particles. Such agglomerated Fe 2 4 particles, free ZnO and ZnCl 3, are moved in an oven flame. Because of the flame temperature, the ZnCl2 escapes from the agglomerated particles and immediately evaporates since the boiling point of ZnCl2 is only 732eC.

For further reference, the properties of some metal chlorides are shown in the following Table A.

TABLE A

Elements of Melting Point Boiling Point Temperature chlorides to decomposition

Zn2 + 313 732

CO2 * 735 1049 4+ sublimation

Zr> 300 m, 2 + sublimation - ...

Ti (in H2 gas) (in air)

Ti3 * 440

Pe2 + 672 1023.4 (H20) 550

Fe3 * 300 317 02 1100

Cu + 422 1366

Ni2 + 1001 973.4

Mg2 * 712 1412

Mn2 * ...................... 650 .................. 1190 ...... . ......

Mn4 * 100 8204778 -6-

The properties listed above are well known.

According to this table, most chlorines will evaporate around 1000 ° C 2+ 3+ 4+ pen while the chlorides of Zn, Fe and Zr will already evaporate below 700 ° C.

It is possible that the chlorides of this table A are below 1000 ° C

into their oxides, with some exceptions, when these chlorides are heated together with steam and oxygen.

To convert FeCl2 to Fe ^ O ^:

FeCl boils at 1023.4 ° C. Theoretically, it is assumed that the gas of mt 10 FeCl 2 *** 0 is converted to Fe 2 ° 3 under an oxidizing atmosphere at about 1100 ° C. In practice, however, it is converted very slowly into Fe2 ° 3 and C ^ 2 *

However, it can be converted very quickly into Fe 2 O 3 and converted if a small amount of H 2 O is mixed in this gas as a catalyst. In this case, FeCl2 can already be converted into Fe2O3 according to the following formula when roasting at about 550 ° C, at least if the required amounts of H2O2 are added.

2FeCl2 + H20 + 1/202 -> Fe203 + 4HC1.

The following describes how the chlorides can be successfully converted into oxides in practice. The pH of the saline containing M ^ + is adjusted to 7 or higher to leave as little free acid in the solution as possible. The remaining free acid is detrimental to maintaining the desired recipe. Namely, because acids react with iron oxides in the solution, FeCl 2 is produced. This FeCl 2 already evaporates at 317 ° C. Thus, FeCl3 will evaporate easily during toasting. To counteract this evaporation of FeCl3, metal powders are added to the solution to react with the free acid before being roasted, turning FeCl3 into FeCl2. This FeCl2 only evaporates at 1023.4 ° C.

Another reaction can also take place. The hydrochloric acid in the solution can also convert zinc ions into ZnCl2. It is therefore necessary to neutralize this hydrochloric acid before adding ZnO to the solution. Iron metal and Fe2 ° 3 'which are the major component of the ferrite are then added to the solution.

When working on a technical scale, the ratio of the various compounds in a common recipe may vary slightly.

6204778 -7- (Τ '.......................

It is impossible to completely avoid the formation of chloride in the solution, even if water is present as a catalyst and oxygen during roasting. By diluting these chlorides, the predetermined ratio of the oxides in the recipe can vary slightly. In practice, therefore, the necessary oxides are added later to correct this ratio. In the invention, a deviation in the ratio of the components can be avoided in the following manner: 1) The solution containing Fe, Mn, Ni, Cu and Co-chlorides is neutralized before roasting.

2) ZnO is mixed in this solution after neutralization.

3) f 2 ° 3 '** The main oxide for the ferrite is prepared separately from other sources. This Fe 2 is then added to the solution so that it becomes thick enough to prepare granules by a granulation treatment.

4) Subsequently, these granules are roasted in an atmosphere with sufficient oxygen and ^ 0, and this at a temperature that exceeds the pyrolysis temperature of the chlorides of all these elements in the granules.

This roasting makes it possible to convert virtually all chlorides in the granules into oxides. Thus, a deviation from the predetermined ratio will remain minimal. If, however, a certain deviation does occur, it can be easily corrected by adding appropriate amounts of MnO, Fe 2 O 4, etc. later.

25 Below is another summary: (A) (B) (C) (D) mixing —► mixing-grinding - "* dried —► roasting in a (x + Y + Z) ïïV particle atmosphere of \\ ° 2 and H2 ° \ granules \ Y j ^ spray grills in suspension ^ an oxidizing atmosphere \ with water drip spray grills \ in an oxidizing atmosphere \ * paste paste with roasting in a water * + oxidizing atmosphere 8204778% -8 -

In the mixture (A), the main material is XiFe ^ O ^. The rest is formed by FeSC> 4, FeCl2 and Fe (NO ^) · Y is chloride, sulfate, nitrate of Mn, Ni, Cu, Co, Mg and partial oxides of these elements.

Z is mainly ZnO, but can also be chloride, sulfate or nitrate.

5 Acid residue always remains in the mixture (A), these acids must be neutralized. Since X and Z mainly consist of particles, they are nevertheless well mixed with Y, which is dissolved in water. During mixing under heating, water slowly evaporates from mixture (A). This mixture (A) then conglutinates by melting.

For the production of Fe-Zn ferrites, the amount of ZnO in the mixture (A) must be greater than Y. In the invention, ZnO and Fe2O2 are always formed into spinels such as ZnO-Fe ^ O ^ ^ by roasting.

As a result, it is possible to avoid cracks on the compressed pieces during sintering. If no roasting is used, cracks occur in the molded parts during sintering, due to expansion or shrinkage in the spinel formation.

Example I

100 mole% iron sulfate, 36.8 mole% MnCl 4 and 13.2 mole% ZnO

are mixed to a suspension (1). This suspension must be mixed well to get it homogeneous. The homogeneous suspension is then sprayed in a grill oven at a temperature of 900 ° C. The suspension is then taken out in the form of particles or granules. These particles are ground into fine particles with water. After this, the particles are dried and compressed to the desired shapes. The compressed particles are then sintered at 1280 ° C. After this sintering, they are cooled in a nitrogen gas atmosphere. The properties of the compressed pieces are as follows:

Permeability ^ 10) = 2100

Quality factor Q = 150

Fermeability loss factor: tan8 / pi = 3.1x10 8204778 r -: --- J'k,.

mm C ^ aw

Example II

48 mole% iron oxide, 36.8 mole% MnCl 2 and 14.2 mole% ZnO are mixed to a suspension (2). It is dried and granulated into particles with a size of about 2 mm. These particles are roasted in an oven with a steam and oxygen atmosphere. They are then immersed in water for rapid cooling. 1 mol% HnO 2 is added to the water (3) containing the roasted particles. MnO 2 and roasted particles are then well ground in the water and mixed into suspension (3). This suspension (3) is dehydrated and residual acid is removed simultaneously. The compressed pieces are compressed at 1300 ° C. The properties of the obtained pieces are as follows:

Permeability (po) 2900 Quality factor Q * 90 —g 15 Permeability loss factor: tanQ / jso * 3.8x10.

The use of sulfate and nitrate as components of a recipe is described below. Manganese must be extracted from its ore by sulfuric or nitric acid. The resulting liquid is concentrated to a concentration of about 4 mol / liter. Iron oxide is then added to this solution. ZnO is added to this solution to replace part of the manganese sulfate or nitrate. The solution is then concentrated by heating.

The concentrated solution is then mixed well and then dried. The dried concentrate is granulated. The granulate 25 is roasted at 900-1200 ° C to decompose the manganese sulfate.

The roasted particles are cooled with air, nitrogen gas or water. These cooled granules are then ground into powders. These powders consist of ferrite. It is absolutely necessary for the production of good quality ferrite that all compounds such as FeZnO and sulphate, nitrate and chloride are homogeneously mixed before granulation. In the practice shown above, Feen ZnO are solid particles and the manganese is in the form of a salt with an acid which has been used for extraction. This salt is in liquid form. Therefore, the particles of a ZnO are mixed well with this acidic salt, which contains manion ions, and is better than would be the case with solid particles of manganese oxide. This mixing operation is only possible with the invention.

8204778 -10-

For the aforementioned mixing and granulation, a heated stirrer coated with Teflon is suitable. This mixing granulator is particularly suitable for the indicated purpose. The conversion of hydrated crystals of salts of M takes place at about 1000 ° C during the mixing granulation, while the mixture is heated in the mixing granulator. Fig. 1 shows the characteristics of crystal formation and dehydration. After the mixed granulation, the granules are toasted. The grating temperature should be kept between 900 and 1100 ° C, which is slightly above the pyrolysis temperature for the sulfates of manganese, zinc and magnesium. All ions of elements in the granules then diffuse into the iron oxide. 1-6 hours are required for this schedule treatment. The duration of the grating period depends on the properties of the iron oxide particles. If the iron oxide was obtained from the brining of steel scrap in a steel mill as the main component of the ferrite, the grating period may be short. This is because the steel salt from the brine process is sprayed into very fine Fe 2 O 2 powders. The required grating temperature for these powders can be low because they are very finely divided and the 2+ M salt easily penetrates into this porous Fe 2 O 2 powder. These latticed particles are particularly suitable for ferrite. If the iron oxides were obtained from a Lurgi-type grate furnace or material obtained directly from iron ore, such as hemation is used as the main component for the ferrite, the period required for roasting is longer. Due to the density of this type of iron oxides that is higher than in the previous case, the grating temperature for this type of iron oxides and other additives should be about 1000 ° C. The product of this grating treatment is also suitable for ferrites. Incidentally, it is always possible to lower the required grating temperature if the roasted oxides are ground into very fine particles.

During the roasting the weight of MnSO4 in the mixture according to fig. 2 varies in detail as follows: MnSO4 is dehydrated below 700 ° C, the pyrolysis of MnSO4 only takes place intensively at about 850 ° C. In this process SO2 is removed in vapor form. Since the salt of Mn and Fe2 O2 * n becomes the mixture at about 1000 ° C to Mnen Fe ^ +, the weight of the mixture decreases. This 8204778: 11 weight loss is caused by the amount of Fe 2 O-3 in the mixture, by the atmosphere in the grate oven, and by the heating time, moon: it is small.

When manufacturing Mn-Zn ferrite, it is possible to mix oxides 2+ 5 of M such as Zn, Na, Cu, Mg, Co, with a manganese ion solution.

Because the small amounts of these oxides are mixed well with a manganese solution lean. Likewise, in the manufacture of 2+ of Mg-Zn ferrites, it is possible to mix oxides of M such as Mn, Ni, Cu, and Co with a magnesium ion solution. It is also possible to use a mixture of 2+ 10 of sulfates, nitrates and chlorides of M elements as an additive for iron oxides. According to the pyrolysis formula 2+, the pyrolysis of the chlorides and nitrates of M elements 2+ takes place at lower temperatures than that of M sulfates. In this connection, the pyrolysis of this mixture takes place particularly well at the pyrolysis temperature of the sulfates by roasting. If acid residues remain in the ferrite even after roasting, these acid residues can be brought back to the desired level by appropriate control of the grating conditions and / or further operations such as grinding and washing with water.

Example III

The mixture was prepared according to the following recipe.

Fe ^ O ^ 69.56 wt%

Mn306 3.89 "

MgO 9.97 "25 NiO 0.34"

CuO 0.45

CoO 0.01

CaO 0.65 "(as binder)

ZrO 0.01 "(as binder) 30 SiO 0.1 solution of ZnSO ^ * * This solution should be equivalent to 15.2 wt% ZnO after pyrolysis.

8204778 -12-

The mixture is granulated into granules 2-3 mm in diameter. During this granulation, heating takes place at about 90 ° C. After the granules are obtained, they are slowly heated to above 200 ° C, dehydrating the granules. Then they are roasted to 5 ferrite. The ferrite granules are ground into powder.

This powder is compressed to a certain shape. The compressed pieces are finally sintered.

The properties of the sintered pieces are as follows: Permability ƒ10 = 410 10 Flux density B _ = 3100 8

Specific resistance p = 1 x 10 Ω Curie temperature Tc = 155eC Coercive force Hc = 0.3.

Example IV

The mixture was prepared according to the following recipe.

Fe ^ O ^ 71.35 in wt%

ZnO 12.70 "

Solution of MnSO ^ * * This must be equivalent to 15.95 wt.% MnO.

Water is added to this mixture to a slurry with about 50% dry matter. This suspension is ground and mixed in a ball mill for 2 hours. After this, the slurry is mixed granulated under heating. The granules obtained are toasted and then quickly cooled. The cooled granules are ground to powder for 2 hours.

0.02 wt% SiC ^ r 0.01 wt% A ^ O ^ / 0.01 wt% VjO ^ and 0.005 wt%

CaO are added to this powder. The powder is then compressed to the desired shape. The compressed pieces are sintered at 1300 ° C for 2 hours and then cooled in nitrogen gas.

The properties of the sintered pieces are as follows: Permeability ƒ10 = 2050 Flux density B ^ = 4900 Coercive force Hc = 0.25.

Example V

The mixture was prepared according to the following recipe.

8204778 r ~ -: -------- -13- ·· V - * · * Ρβ2 ° 3 71 wt%

ZnO 13 "

Solution of MnSO ^ (equivalent to 16% MnO)

Solution of NiSO ^ (equivalent to 0.02% NiO) 5 Solution of CoSO ^ (equivalent to 0.01% CoOj

SiOj 0.02 wt% ai2o3 0.01 "v2o5 0.01"

This mixture is ground well in a ball joint and then granulated in batch form with heating. The granules obtained are roasted at 1100 ° C for 3 hours and then poured into water for rapid cooling. The toasted granules are then ground in a ball joint with water for 6 hours. The suspension thus formed is dehydrated, dried and ground to a powder, adding 0.1% by weight of polyvinyl alcohol as a compression aid to the powder during compression.

The compressed pieces are sintered for 2 hours at 1300 ° C in a 0.4% oxygen-containing atmosphere and after sintering at 900 ° C # cooled in a nitrogen atmosphere containing 0.1% oxygen, after which further cooling is carried out in a complete nitrogen atmosphere.

The properties of the sintered pieces obtained are as follows:

Permeability jio 3 3200 Flux density 3 4800 25 Coercive force Hc 0.3.

Example VI

A dry mixture was mixed well and roasted:

Fe2 O3 53 mol%, MnSO ^ 37 mol%,

ZnO 9.5 mol%, FeCl2 0.5 mol%.

During the mixing under heating, the whole melted after which it became granules. The resulting granules were roasted at 1000 ° C for 1 hour and poured into water for rapid cooling. The cooled granules were then ground in water to particles smaller than 10 µl.

The particulate slurry was dewatered and then the material compressed to the desired shapes. The compressed pieces were sintered at 1350 ° C for 2 hours. Its properties are 8204778 -14- as follows:

Permeability jia (at 20 ° C) = 2700 ° C (at 80 ° C) = 4800

Flux density B ^ = 5100 5 Curie temperature Tc = 250 ° C.

8204778

Claims (10)

A method for producing a ferromagnetic 0x7de by mixing a solution containing sulfates, nitrates and / or hydrochlorides of at least one metal of the group Mn, Ni, Cu, Mg, Zn and Co with iron oxide, and to roast the resulting slurry to a ferromagnetic material, this grating step being carried out at a temperature of not more than 1450 ° C but equal to or higher than the temperature at which the acid groups of the sulfates, nitrates and / or hydrochlorides are decomposed and evaporated. 2. Process according to claim 1, characterized in that the solution comprises a suspension containing oxides of at least one metal and / or water-insoluble salts thereof which convert to oxides upon heating, said suspension being prepared by addition of part of the at least one metal in the form of oxide or water-insoluble salt. Method according to claim 2, characterized in that the suspension has a dry matter content of between 40 and 70% by weight. 4. Process according to claims 1-3, characterized in that as a mole fraction in the preparation of the suspension about 40-60% of iron oxide is mixed with about 60-40% of at least one metal in terms of the total oxide content of this solution or suspension. Method according to claim 4, characterized in that, based on the total solids content of the suspension, the mole fraction Zn and / or Mgf mixed in the form of this solution or suspension * is between 5 and 25% calculated as ZnO and / or MgO . Process according to claims 1 to 5, characterized in that SiO 2, TiOgr a * 2 ° 3 / 2r0 and // ° f Ca0 is added to suspension, such that the resulting ferromagnetic material contains these metals in an amount between 0.001 and 0.7% by weight. 7. Process according to claims 1-6, characterized in that the iron oxide consists of powdered iron oxide, the particles of which have a rough surface which is activated by brining. 8. Process according to claims 1-7, characterized in that during the roasting the suspension is first dried at 60-500 ° C, then decomposed by heating at 800-1200 ° C to evaporate the acidic groups followed by roasting at a temperature between the minimum temperature required for ferromagnetism to 1450 ° C. 9. Method according to claims 1-7, characterized in that during the roasting the slurry is introduced into a grate oven by spraying it in or introducing it in the form of a dry powder or granules. 10. A method according to claims 1-9, characterized in that the suspension is roasted in an atmosphere containing water vapor and oxygen. 8204778