JPS5951499B2 - Goethite manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention produces goethite (Fe) by a wet method using an aqueous ferrous sulfate solution as a raw material.

O,・H. O). Goethite itself is used as an inorganic yellow pigment and also used as a pigment (Fe).

raw materials for magnetic materials, iron oxide (Fe.O, and γ)
・Fe. It is also used as a raw material for pure iron powder with high magnetic coercivity. Previously, Bengara for pigments was made using ferrous sulfate at 7 water temperatures (FeSO, 7H).

It has been manufactured by sintering O). However, since this method causes pollution due to the generation of sulfur dioxide gas during sintering, a method is gradually being adopted in which goethite is used as a raw material and the valve I pattern is obtained by roasting it. In addition, iron oxide for magnetic materials is produced by dehydrating and reducing goethite.
e, O. (magnetic material) and further Fe. O. It is obtained by oxidizing at low temperature to form maghemite. Further, pure iron powder with high magnetic coercivity can be obtained by reducing goethite obtained by oxidation with an alkali side. Goethite used for such various purposes is manufactured, for example, in the following manner.

Add a certain amount of caustic soda to an aqueous solution of ferrous sulfate in advance.
Alternatively, Fe(OH)O produced by adding ammonia is oxidized to generate goethite seed crystals, and air or oxygen is then introduced to continue oxidation, and the solution value is 4 to 4.
Add alkali dropwise to maintain the liquid temperature at 60 to 70.
While maintaining the temperature at °C, air is introduced to continue oxidation to produce goethite. This goethite is obtained by growing existing seed crystals (fine needle-like crystals) into needle-like crystals. The reaction in this method is as shown in the formula below, and 1/2 mole of oxygen is required to oxidize 2 moles of iron sulfate. l2Fe
SO4+1/202+4NH4OH22FeOOH+
2 (NH.). SO, +H. However, this method has the disadvantage that the reaction efficiency is low and the processing time is long because the reaction is carried out in a temperature range where the solubility of oxygen is low.

That is, the solubility of oxygen in water under normal pressure (volume cm3 in which oxygen at 1 atm dissolves in 1 cm3 of water) is:
0.049 at 0°C, 0.023 at 40°C, 0.0 at 60°C.
019, and at 60°C it is 2.6 compared to 0°C.
decreases by a factor of 1. Moreover, when air is blown into the reactor, the partial pressure of oxygen becomes one-fifth, so the amount of dissolved oxygen is reduced, and the reaction efficiency is further reduced. Therefore, in this method, it is necessary to improve the reaction efficiency by increasing the amount of dissolved oxygen by introducing air under pressure or by increasing the gas-liquid contact area by making the air into fine bubbles. In the method of carrying out the reaction under pressure,
The oxidation reaction can be carried out in a few tenths of the time required for reaction at normal pressure, and the liquid temperature can be set from room temperature to nearly 200°C, and there is a permissible range. However, since the reaction is carried out under pressure, the equipment becomes complicated and the operation becomes complicated.Additionally, as a method of making air into microbubbles, an acid-resistant metal pipe with many ventilation holes or l There is a method using a ventilation plate with ventilation holes, but there is a problem that the product gradually blocks the ventilation holes.

There is also a method of turning air into microbubbles using heat-resistant and acid-resistant woven fabrics made possible by the development of synthetic fibers. This method is effective in the early stage of the reaction, as fine bubbles are generated from a wide area, but as the reaction progresses, the mesh becomes clogged with deposits, resulting in high air resistance. Therefore, there is a drawback that the generation of bubbles is uneven. Also, although the weave appears to be uniform at first glance, in reality the size of the weave varies depending on the location. Because of this, the air bubbles gather in areas with less resistance, and the air bubbles that exit the cloth gather to form large air bubbles.
Furthermore, when goethite is used as a non-wiping yellow pigment, as a raw material for red pigments, or as a raw material for iron oxide for magnetic materials, it is required that the goethite crystals be fine and uniform in size.

For example, goethite, which is used as a non-wipeable yellow pigment, needs to have a uniform particle size in order to make its hue clear, that is, to eliminate so-called ``dullness''. In order to make the particle size of goethite uniform, it is necessary to form air into fine bubbles and uniformly disperse the air to achieve good gas-liquid contact. There is a gas-liquid contact device designed to achieve this purpose, as shown in Figure 1.
issue).

This device has a rotary cylinder 2 in a tank 1 and an air blowing pipe 3 inside the rotary cylinder 2. The rotary cylinder 2 is rotated about a shaft 4 and air is supplied from the air blowing pipe 3. Blow in as shown by the arrow to achieve fine bubble formation and uniform dispersion. However, when a ferrous sulfate aqueous solution is brought into gas-liquid contact with oxygen in the presence of an alkali, ferrous hydroxide and goethite are produced and the viscosity increases.

Therefore, in the gas-liquid contact device shown in FIG. 1, it is difficult to form fine bubbles of air and uniformly disperse the air. As a result, it is difficult to obtain fine and uniform goethite, and for example, goethite used as a no-wipe yellow pigment tends to have a ``dull'' hue. In other words, the process in which goethite is produced using ferrous sulfate as a raw material is that seed crystals that have been generated or added in advance grow as the ferrous salt oxidizes, and the acicular crystals of goethite grow in the length and width directions. The growth of goethite progresses, and the characteristics of goethite are determined by the degree of growth.

However, when ferrous hydroxide and goethite are produced in the course of this reaction, the viscosity of the slurry containing them increases, making stirring difficult.

This prevents air from being uniformly supplied into the slurry, and as the air bubbles rise through the slurry, the pressure decreases and the air bubbles become larger due to their bonding. As a result, the gas-liquid contact becomes poor, the oxidation reaction in the slurry becomes non-uniform, and the crystal size becomes non-uniform. Furthermore, in the conventional method, there are problems not only in the manufacturing technology described above but also in raw materials.

That is, iron sulfate, which is a raw material in the conventional method, was obtained mainly from a large amount of sulfuric acid pickling waste generated by continuous pickling of hot rolled steel sheets. However, in recent years, continuous pickling has mostly been replaced by hydrochloric acid picklinda. The ferrous chloride obtained from this hydrochloric acid pickling waste liquid is not suitable for the production of goethite in terms of crystal form and hue. Therefore, sulfuric acid is added to this iron chloride solution and heat treated to remove the hydrochloric acid content. Iron sulfate can be obtained by removal and recovery. However, in this case, there are disadvantages of high equipment costs and high raw material costs. The present invention has been made in view of the above circumstances, and aims to have high reaction efficiency, fine and uniform goethite crystals obtained, and high purity and inexpensive raw materials. The purpose is to obtain a method for manufacturing goethite that can be used.

That is, the present invention includes a disc-shaped rotating base, a plurality of vertical rod-shaped agitators provided on the inside of the lower surface of the base, and a gas inflow system that causes air to flow upward from below into the space surrounded by the agitators. A gas-liquid contact device is provided with a tube, and while a solution containing a ferrous sulfate aqueous solution and goethite seed crystals is placed in the gas-liquid contact device, the rotating base is rotated and gas is injected from the gas inflow tube. This is a goethite production method characterized by growing goethite seed crystals by blowing oxygen gas or a gas containing the gas.

Further, in an embodiment of the present invention, when obtaining an aqueous ferrous sulfate solution, converter 0G dust is thermally decomposed with a sulfuric acid solution to crystallize ferrous sulfate, and the crystallized ferrous sulfate is separated. This method is characterized in that it is dissolved to prepare a ferrous sulfate solution and used as a raw material liquid. The present invention will be explained below with reference to the drawings.

The method of the present invention is a method for obtaining goethite by bringing a solution containing a ferrous sulfate aqueous solution and goethite seed crystals into gas-liquid contact while stirring in a gas-liquid contacting device as shown in FIGS. 2 to 4. .

In this method, we developed a method that uses converter 0G dust to obtain the ferrous sulfate aqueous solution that is the raw material.

Converter 0G dust is dust obtained in a precipitator when recovering CO gas during scouring in a converter. Its composition is mainly composed of metallic iron and FeO, as illustrated in Table 1, and sulfuric acid. The content of Fe2O3, which is difficult to dissolve in iron, is small. Therefore, it does not require any reduction treatment in advance. In addition, those obtained from mill scale or hydrochloric acid pickling waste liquid are
As shown in the table, it contains a large amount of Fe2O3 and requires a prior reduction treatment to be used as a raw material for an aqueous ferrous sulfate solution. In addition to Mn in the steel, this 0G dust contains impurities such as Si, Al, CO, and Mg that are thought to have been mixed in by the scattering of slag, so it is necessary to purify and remove these impurities. .

First, as shown in the flow sheet of FIG. The dust 11 is thermally decomposed with a sulfuric acid solution 12 at a temperature of about 70 to 90°C.

As a result of this thermal decomposition, the ferric oxide contained in the 0G dust 11 is reduced by the hydrogen generated when the mixed metal iron is dissolved, and is dissolved as ferrous sulfate. Sulfuric acid No. 1
The solubility of iron is Changes as shown in Figure 6 (Bla
stFumaceandSteelPlantSept
1957). In the figure, a1 is 0% sulfuric acid concentration, A2 is 5%, A
3 is 10%, A4 is 20%, A5 is 30%, A6 is 40%
% and A7 indicate 50%, and on the right side of the broken line in the figure, ferrous sulfate monohydrate (FeSO4.H2O) is produced, and on the left side, its heptahydrate (FeSO4.7H20) is produced. Therefore, based on the solubility curve of ferrous sulfate shown in FIG. 6, by keeping the solubility sulfuric acid concentration at 20% or more, iron sulfate is precipitated as a hydrated salt (FeSO4.H2O).

Next, the ferrous sulfate monohydrate 13 is separated without washing and dissolved in water 14, and the undissolved residue 15 is filtered off to be used as the ferrous sulfate aqueous solution 16. Approximately 1/20 of the supernatant liquid 17 from which the ferrous sulfate monohydrate 13 has been separated is discarded, concentrated sulfuric acid is added thereto, and the supernatant liquid 17 is recycled as the sulfuric acid solution 12 again. The reason for rejecting about 1/20 is to prevent accumulation of impurities. Furthermore, the present invention allows goethite seed crystals to coexist in the ferrous sulfate aqueous solution thus obtained.

This method is carried out by adding a certain amount of caustic soda or ammonia to a ferrous sulfate aqueous solution in advance, and then oxidizing it to produce goethite seed crystals, similar to the conventional method. In the method of the present invention, this solution is stirred and brought into gas-liquid contact, and the gas-liquid contact apparatus used in this method is as shown in FIGS. 2 to 4. That is, this gas-liquid contact device includes a disc-shaped rotating base 22 in a tank 21, a plurality of vertical rod-shaped agitators 23 provided inside the lower surface of the base 22, and a space surrounded by the agitators 23. Gas inflow pipes 24 are provided for inflowing air from below upwards. A rotating shaft 25 is provided at the center of the rotating base 22, and is rotated by a geared motor 28 through an airtight bearing 26 and a transmission device 27 such as a bevel gear at the bottom of the tank 21. Further, a goethite discharge pipe 29 is attached to the lower part of the tank 21. A raw material inflow pipe 30 and an air discharge pipe 31 are provided at the upper part of the tank 21 . This device itself is
This is known from Japanese Patent Publication No. 53-42472. The present invention uses this gas-liquid contact device, and when the rotating base 22 is rotated at high speed, the synergistic effect of the rotation of the rotating base 22 and the agitator 23 that rotates accordingly causes the rotation of the rotating base 22 to increase. A circulating flow as shown by the broken lines at the top and bottom is generated. These two circulating flows mix with each other to some extent when flowing in the circumferential direction, that is, in the tank wall direction, at the position of the rotating base 22, so that they are homogenized as a whole. The air blown from the gas inflow pipe 24 rises in the space surrounded by the stirring rod 23 as slightly large bubbles, forms a bubble film on the bottom surface of the base, and gradually moves to the periphery. Films are becoming increasingly thin.
Furthermore, the thinned air generates a strong shearing force with the liquid at the peripheral edge of the bottom surface of the substrate, forming microbubbles, and as the two circulation flows mentioned above flow, they are attached to the tank wall in an abcentric manner. Once spouted. As a result, air is uniformly dispersed throughout the liquid, and air is constantly supplied to positions on the substrate where intense gas-liquid contact occurs. Through this gas-liquid contact, ferrous sulfate is oxidized as shown in the formula below to produce goethite, and goethite seed crystals grow. 2FeS0.

+ 1/202+ 4NH,0H= 2Fe00H+
The formation of 2(NH4)2S04+H2OFeOOH turns the solution into a slurry, and as its amount increases, the consistency of the slurry increases.

However, with this gas-liquid contact device, even when the slurry is made, the two circulating flows perform good agitation, maintain uniformity within the slurry, uniformize the growth rate of goethite crystal nuclei, and reduce the crystal size to a fine level. And it can be made uniform. Furthermore, according to this gas-liquid contacting device, the oxidation rate can be adjusted by changing the amount of air supplied or the rotational speed, so it is also possible to adjust the growth rate of goethite crystal nuclei, that is, the crystal size. Note that the temperature conditions and temperature conditions in this gas-liquid contact reaction are appropriately selected as necessary.
For example, the liquid temperature is room temperature or heated, and the flattening condition is performed on the alkaline side or acidic side. In the present invention, a ferrous sulfate aqueous solution and goethite seed crystals coexist, but according to this gas-liquid contact device, goethite can be produced even without coexisting goethite seed crystals by setting temperature conditions and flat conditions. can be manufactured. Next, examples of the present invention will be described. Example 1 A 20% aqueous solution of 11% iron sulfate (FeSO) was kept at room temperature, and 4N ammonia water (NH) was added in an amount equivalent to about 1/10 of the iron sulfate in the solution.

7%) 7.21 was added and part of the iron sulfate was replaced with iron hydroxide.

The gas-liquid contact device according to the present invention was applied to this liquid at an air introduction rate of 201/min and a rotating board rotation speed of 3000 r. p.
m. It was operated for about 2 hours under these conditions to generate fine seed crystals of goethite. Next, this solution was brought into gas-liquid contact under the conditions shown in Table 2, during which time 4N ammonia water (NH, 7%) was added little by little to maintain the flat value at 4 to 4.5.

The properties of the goethite thus obtained are also listed in Table 2. In contrast, when a solution containing an aqueous ferrous sulfate solution and goethite seed crystals was treated using an acid-resistant and heat-resistant chemical fiber diffuser cloth, and a conventional gas-liquid contact device shown in Fig. 1. The respective conditions and properties of the obtained goethite are also listed in Table 2.

As is clear from the above table, according to the present invention, the oxidation time is short, the reaction efficiency is high, and the resulting goethite particles can be made uniform.

This is because, according to the gas-liquid contact device of the present invention, the oxidation reaction is rate-determined by the reaction at the gas-liquid contact interface, and the air forms extremely fine bubbles at the peripheral edge of the bottom surface of the substrate, resulting in an extremely large surface area. It is thought that. Example 2 After adding 1/10 equivalent of caustic soda to 3.0% aqueous solution 11 of ferrous sulfate (FeSO4) and converting part of the iron sulfate to ferrous hydroxide, a relatively mild 2 Through gas-liquid contact, fine crystal nuclei of hydrous ferric oxide (goethite) were created.

After this solution was heated to 65° C., the rotating base of the gas-liquid contact device shown in FIG. 2 was rotated at a circumferential speed of 5 m/Sec, and air was introduced at a rate of 0.31/min. At the same time, 4N caustic di-soda aqueous solution was added dropwise to remove the solution. value 4
It was maintained at ~5. The acicular goethite thus obtained was then washed, filtered, and dried. Table 3 shows the time required for oxidation and the amount of air used in this case. Furthermore, an electron micrograph of the obtained goethite crystals is shown in Fig. 7. The obtained goethite had a good yellow color tone and was of excellent quality as a yellow pigment.

Next, this goethite is dehydrated and reduced to produce Fe3O4, which is then subjected to a low-temperature oxidation process to obtain γ.Fe2O3. Ta.

The crystal size, axial ratio, coercive force (HC
) are shown in Table 4. To this, air was blown at a ratio of 11/min through a chemical fiber woven cloth to obtain goethite.

This goethite has a slight dullness in its hue.
Ta. The time required for oxidation and the amount of air used in this case are also listed in Table 3. Furthermore, γ.Fe2O3 was obtained from this goethite, and its crystal size, axial ratio, and holding power are also listed in Table 4.

From the above table, according to the present invention, the reaction efficiency of gas-liquid contact is high;
It is also seen that the reaction time is short and the magnetic properties of γ.Fe2O3 obtained using goethite as a raw material are excellent. Example 3 Ferrous sulfate monohydrate (FeSO4.H2O) was dissolved in 71 parts of water, and 21 parts of 4N caustic soda was mixed at room temperature to replace iron sulfate with ferrous hydroxide. Of slurry? The value reached 12.

After raising the temperature of this slurry to 45°C, the rotating substrate was rotated at a circumferential speed of 5 m/Sec using the gas-liquid contact device shown in Figure 2, and air was blown in at a rate of 21/min to prevent microfoaming. Katta. The reaction was completed in 8.5 hours. The produced goethite was filtered and washed and then dried. Next, pure iron powder was obtained by reducing this goethite in a hydrogen atmosphere. When the magnetic properties of the pure iron powder thus obtained were investigated, the magnetic coercive force (Hc) was extremely high at 14,000e.

Example 4 35 kg of 0G dust having the composition shown in Table 1 above was put into 20ml of 40% sulfuric acid solution, and heated at about 80° C. with stirring to decompose it.

After decomposition, about 32 kg of crystals of ferrous sulfate monohydrate were precipitated.
Next, a solution part in which ferrous sulfate is dissolved (FeSO.

5.4%, H.

SO, 25%) 17O was removed by suction using a pipe with a filter cloth at the tip. Next, pour water into this tank and wait for 60~
The mixture was heated to 70° C. to dissolve one portion of ferrous sulfate in water, filtered to remove undissolved residues, and then transferred to another reaction tank to obtain a ferrous sulfate aqueous solution for goethite production. In this ferrous sulfate aqueous solution, almost all impurities other than manganese in the raw material dust can be removed.

Therefore, it was recognized that this ferrous sulfate aqueous solution can be used as a raw material liquid. Regarding the solution part 1701 in which ferrous sulfate is dissolved, about 1 year old is extracted and sent to wastewater treatment, and the remaining 16 year old is dissolved in concentrated sulfuric acid (
98%) was added thereto, water was added to make the solution 20%, the sulfuric acid concentration was adjusted to 40%, and the solution was used for the next dissolution of 0G dust.

As described above, according to the present invention, air can be finely and uniformly dispersed in a slurry solution to improve gas-liquid contact, thereby increasing reaction efficiency and processing in a short time. Because the contact can be made evenly,
The crystal size can be made uniform.

Therefore, the goethite obtained by this method is extremely effective as a raw material for non-wiping yellow pigments, red pigments for pigments, iron oxide for magnetic materials, and pure iron with high magnetic coercivity. Furthermore, by using the converter 0G dust as a raw material for the ferrous sulfate aqueous solution, the raw material cost can be reduced.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional gas-liquid contact device, Fig. 2 is a sectional view of a gas-liquid contact device used in the method of the present invention, Fig. 3 is a side view of the rotating base of the same device, and Fig. 4 is the same plane. Figure 5 is a flow sheet diagram showing the process of producing an aqueous ferrous sulfate solution, which is a raw material for the method of the present invention, from 0G dust, Figure 6 is a diagram showing the relationship between temperature and solubility of iron sulfate, and Figure 7 is a diagram showing the relationship between temperature and solubility of iron sulfate. The figure is an electron micrograph showing goethite crystals obtained by the method of the present invention. 1...tank, 2...rotating cylinder, 3
・・・・・・Air blowing pipe, 4 ・・・・・・Shaft, 11・
...0G dust, 12...Sulfuric acid solution, 1
3... Ferrous sulfate hydrate salt, 14...
Water, 15... Insoluble residue, 16... Ferrous sulfate aqueous solution, 17... Supernatant liquid, 21...
... Tank, 22 ... Rotating base, 23 ...
- Stirring body, 24... Gas inflow pipe, 25...
...Rotating shaft, 26...Bearing, 27...
Transmission device, 28...Geared motor, 29...
... Goethite discharge pipe, 30 ... Raw material inflow pipe, 31 ... Air discharge pipe.

Claims (1)

[Claims] 1. A disc-shaped rotating base, a plurality of vertical rod-shaped stirring bodies provided inside the lower surface of the base, and air flowing upward from below into the space surrounded by the stirring bodies. A gas-liquid contact device is provided, each having a gas inflow pipe, and with a solution containing a ferrous sulfate aqueous solution and goethite seed crystals coexisting in the gas-liquid contact device, the rotating base is rotated and the gas is A method for producing goethite, which comprises blowing oxygen or a gas containing the gas through an inflow pipe to cause gas-liquid contact and grow goethite seed crystals. 2 Ferrous sulfate aqueous solution is produced by thermally decomposing converter OG dust with sulfuric acid solution to crystallize ferrous sulfate.
The method for producing goethite according to claim 1, wherein iron is separated and then dissolved to prepare an aqueous ferrous sulfate solution to be used as a raw material liquid.