JPH07242413A - Production of crystalline siliceous compound - Google Patents

Abstract

PURPOSE:To suppress the formation of the deposit layer and agglomerate in a device and improve the productivity by burning a powdery amorphous silica compd. having a specified content of water. CONSTITUTION:A siliceous compd. soln. (e.g. silicate soln.) contg. 28-95wt.% (wet basis) water is dried at 170-400 deg.C by spray drying, etc., to obtain a powdery amorphous siliceous compd. contg. <=1.2wt.% (wet basis) water. The compd. is then burnt at 550-830 deg.C by a rotary kiln, etc., to obtain a crystalline siliceous compd. expressed by the formula (M is Ni and/or K, M' is Ca and/or Mg, y/x=0.5 to 3.5, and z/x=0 to 1.0).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for industrially producing a crystalline silicic acid compound. More specifically, the present invention relates to a method for producing a highly productive crystalline silicic acid compound in which the formation of a deposit layer and agglomerates in a firing apparatus is suppressed.

[0002]

2. Description of the Related Art When a crystalline silicic acid compound is produced by calcining a hydrous silicic acid compound, when a heat load is applied to the hydrous silicic acid powder as a raw material, a foaming phenomenon and a softening phenomenon generally occur due to dehydration, and It is known that adhesion occurs at. Therefore, in order to enable stable continuous production, it is necessary to suppress the adhesion phenomenon that hinders the movement of the raw material powder.

As a conventional method for producing a crystalline silicic acid compound, JP-B-5-66888 and JP-A-3-164422.
Japanese Patent Laid-Open No. 4-214024, Japanese Patent Laid-Open No. 4-2024
The method described in Japanese Patent No. 38809 may be used.

In Japanese Patent Publication No. 5-66888, a crystalline silicate compound is obtained by heating and crystallization in an internal heat type horizontal rotary tubular furnace in which a powdery amorphous hydrated silicate compound is thermally insulated. At this time, adhesion of raw material powder to the inner wall surface of the furnace core tube,
As a means for suppressing the formation of agglomerates having a large particle size that hinders the movement of the raw material powder in the furnace core tube, a method of refluxing a part of the crystalline silicate compound to be the product and blending it into the raw material powder Is proposed. In this case, the water content of the powdery hydrous silicate is such that the maximum loss on ignition is 20 wt%,
It is described that one having a water content of -20 wt% is prepared and used (see Japanese Patent Publication No. 5-66888, claims column, column 4, lines 31 to 39, see Loss on ignition of 4.7% in Example 5 of column 6, 1.4% of ignition loss on Example 6 of column 7, 4.8% on Example 7 of column 7
The loss on ignition is disclosed). In other words, 1-20
When using an amorphous hydrous silicate compound having a water content of wt%, it is possible to reflux a part of the crystalline silicate compound that is the product, in which the raw material powder adheres to the inner wall surface of the furnace core tube or inside the furnace core tube. It is necessary to suppress the formation of agglomerates of.

In Japanese Patent Laid-Open No. 3-164422, powdery amorphous sodium silicate having a high bulk density is obtained by spray drying at a low temperature and a short residence time, and this is heated in a heat-insulated internal rotary tube furnace. To obtain crystalline sodium silicate. At this time, a method has been proposed in which a silicate compound powder obtained by suctioning from a rotary tubular furnace and collecting with a filter is mixed with the hydrous silicate compound powder as a raw material.

In Japanese Patent Application Laid-Open No. 4-214024, a number of 12
The melt of the silicate compound obtained by melting at a temperature of 00 to 1400 ° C. is pulverized to a particle size of 2 mm or less, and heat crystallization treatment is performed to obtain a crystalline silicate compound. As a means for preventing the seizure of water glass during the heat crystallization treatment, a method has been proposed in which a part of the crystalline silicate compound to be the product is added to crushed water glass particles.

Further, Japanese Patent Application Laid-Open No. 4-238809 proposes a method of heating and crystallizing a sodium silicate solution in a horizontal rotary tube furnace equipped with a scraper.

[0008]

However, in any of the methods described in JP-B-5-66888, JP-A-4-214024, and JP-A-3-164422, the inside of the furnace core tube is used. Since a part of the powder or the product powder is refluxed, the thermal efficiency and the productivity are reduced.

Further, in the method disclosed in Japanese Patent Laid-Open No. 4-214024, there is a problem that the volume of the furnace core tube becomes large because the apparent specific gravity of the reflux powder blended in the raw material powder is low. In addition, the powder obtained by industrial spray drying has an average particle size of 500 μm or less, the contact area between powders during firing is large, and the powder softens during heating. It is not possible to prevent them from aggregating into a lump. In the latter method, sodium silicate obtained by suction from a rotary tubular furnace is recovered by a filter, mixed again with amorphous sodium silicate and introduced into a tubular furnace. Since the obtained sodium silicate is not sufficiently heated, the degree of crystallization is small and the effect of preventing adhesion to the tube wall can hardly be expected.

In Japanese Patent Publication No. 5-66888,
The water content of the powdery hydrous silicate compound supplied to the firing furnace is 1
˜20 wt%, specifically 1.4 wt% (wet weight basis) to 4.8 wt% (wet weight basis) is given as an example, but both are relative to the hydrous silicate compound. Adhesion in the furnace is prevented by a complicated process of refluxing 10 wt% or more of product powder.

Further, in the method described in Japanese Patent Application Laid-Open No. 4-238809, the sodium silicate solution is directly charged into the heating zone, but in this case, the phenomenon of foaming and adhering to the tube wall occurs. Although it is disclosed that a scraper is attached to remove the adhered matter, the scraper itself also adheres, which has a drawback that the number of maintenance operations for removing the adhered matter adhered to the scraper increases. In the present specification, a layer formed by an adhering substance on a pipe wall or a scraper in a heating furnace is referred to as an adhering substance layer.

Therefore, a method for producing a crystalline silicic acid compound without forming an adhered substance layer inside a firing apparatus (for example, inside a furnace core tube of a heating furnace) and without lowering thermal efficiency and productivity has never been available. Currently, it is not provided. The present invention has been made in view of the above problems, and is a highly productive crystalline silicic acid compound in which the formation of an adherent layer and an agglomerate in a firing apparatus is suppressed without refluxing the product powder. It aims at providing the manufacturing method of.

[0013]

DISCLOSURE OF THE INVENTION The present inventors have found that the foaming and the formation of a deposit layer that occur when a silicic acid compound is fired are caused by the evaporation of water contained in the silicic acid compound, and further research is conducted. Then, the present invention was completed.

That is, the gist of the present invention is (1) water content 1.
A method for producing a crystalline silicic acid compound, which comprises firing a powdery amorphous silicic acid compound at 2 wt% (wet amount basis) or less, (2) a method for producing a crystalline silicic acid compound,
Water content of 28 wt% (wet amount basis) or more and less than 95 wt% (wet amount basis) of a silicic acid compound solution is dried to 1.2 wt%
% (Wet weight standard) or less powdery amorphous silicic acid compound,
Next, the method for producing a crystalline silicic acid compound, which comprises firing the amorphous silicic acid compound, (3) having a water content of 0.05
The production method according to the above (1) or (2), wherein the crystalline silicic acid compound produced is from the general formula xM ₂ O · ySiO ₂ · zM′O (however, ,
M represents Na and / or K, M ′ represents Ca and / or M
g, y / x = 0.5 to 3.5, z / x = 0 to 1.
It is 0. (1) which is a compound represented by
The present invention relates to the manufacturing method according to (2) or (3).

The present invention will be described in detail below. In the manufacturing method of the present invention, the water content is 1.2 wt% (based on the amount of moisture).
The following powdery amorphous silicic acid compound is subjected to firing. The method for preparing a powdery amorphous silicic acid compound having a water content of 1.2 wt% (wet amount basis) or less is not particularly limited. Usually, the silicic acid compound solution used as a raw material is a silicic acid compound solution having a water content of 28 wt% (wet amount standard) or more and less than 95 wt% (wet amount standard), and preferably a water content of 35 wt.
% (Wet weight basis) to 75 wt% (wet weight basis) of the silicic acid compound solution. As the silicate compound solution, it is possible to use an industrially produced silicate solution as it is, but since the industrially produced silicate solution usually has a low alkali metal concentration with respect to silicic acid, Sodium hydroxide solution and / or potassium hydroxide solution or the like may be added to the mixture to appropriately adjust the alkali metal concentration to be used. Further, even a silicic acid compound solution containing these hydroxides, chlorides or nitrates as a source of Ca and Mg can be used. In the present specification, the water content is simply expressed as wt% in the following, but it is a value on a wet basis.

The silicic acid compound solution used in the present invention includes, in addition to the silicate solution, solid sodium orthosilicate or sodium metasilicate, sodium or potassium hydroxide, chlorides and nitrates, soluble silica, etc. It is also possible to use a silicic acid compound solution whose composition is adjusted by adding an aqueous solution of one or a mixture thereof.

The composition of these silicic acid compound solutions used in the present invention is not particularly limited, but the crystalline silicic acid compound formed by firing is represented by the general formula xM ₂ O.y.
SiO ₂ · zM′O (provided that M represents Na and / or K, M ′ represents Ca and / or Mg, and y / x = 0.5.
.About.3.5 and z / x = 0 to 1.0. ) Is appropriately prepared to have a desired composition.

The silicic acid compound solution prepared to have the desired composition is
Next, by performing a drying treatment to reduce the upper limit of the water content to 1.2 wt%, it is possible to prepare the powdery amorphous silicic acid compound used in the present invention. Here, the upper limit of the water content of the powdery amorphous silicic acid compound is 1.2 wt%, but it is preferably reduced to 0.05 to 0.9 wt% or less, more preferably 0.1 to 0.7 wt%. Is desirable. When the water content exceeds the upper limit, it becomes difficult to effectively prevent foaming and the formation of a deposit layer during firing. The reason why the water content of the amorphous silicate compound is reduced by performing the drying treatment will be described below.

The main causes of foaming and formation of a deposit layer when firing the amorphous silicic acid compound are that the moisture contained in the amorphous silicic acid compound facilitates the softening of the amorphous silicic acid compound and the evaporated moisture. The volume expansion of. Therefore, it is important to sufficiently reduce the water content of the amorphous silicic acid compound before starting the firing step in order to prevent foaming and the formation of a deposit layer during firing. is important.

As described above, in Japanese Patent Publication No. 5-66888, when an amorphous hydrous silicate compound having a water content of 1 to 20 wt% is used, a part of the crystalline silicate compound to be a product is refluxed. It is disclosed that this is necessary to suppress the adhesion of the raw material powder to the inner wall surface of the furnace core tube and the generation of lumps in the furnace core tube. However, although the present inventors tend to expand the volume of the particles to a certain extent when the content exceeds 1 wt%, if the content is 1.2 wt% or less, a part of the crystalline silicate compound to be a product may be refluxed. It has been found that the raw material powder does not adhere to the inner wall surface of the furnace core tube, and the firing step can be performed without forming a lump in the furnace core tube. Therefore, according to the method of the present invention, the crystalline silicic acid compound can be industrially advantageously produced easily.

The drying method in the drying step of the present invention is not particularly limited, and it is possible to carry out the drying treatment in one step, but in view of thermal efficiency, the drying is divided into two steps. Is desirable. That is, first, in the first-stage drying, a silicic acid compound solution having a water content of 28 wt% or more and less than 95 wt% is dried to a water content of less than 28 wt% to over 1.2 wt% to be powdered. Examples of the dryer used at this time include shelf drying, drum dryer, spray drying, and the like. When drying a large amount, spray drying is preferably used because continuous operation is possible and a crushing step is not required.

Next, in the second-stage drying, in order to further reduce the water content, a water content of 1.2 w was obtained by using a fluidized bed, shelf drying or the like.
A powdery amorphous silicic acid compound of t% or less is obtained. The drying temperature at this time is 170 ° C to 400 ° C, preferably 1 at the product temperature.
90 to 350 ° C, more preferably 220 to 320 ° C. At a temperature lower than 170 ° C, the water content is 1.2 wt.
%, It takes time, and at temperatures above 400 ° C., the silicate compound powder may soften and form agglomerates. With respect to the type of dryer, fluidized bed drying is preferable because a continuous operation is possible when drying a large amount, but it is not particularly limited to the dryer described here.

The powdery silicic acid compound obtained here is amorphous, and no clear peak is observed even when analyzed by X-ray diffraction. However, the crystalline silicic acid compound obtained by crystallizing this amorphous silicic acid compound by the following firing is
Specific peaks are observed depending on the crystalline phase.

Next, the crystalline silicic acid compound of the present invention is produced by firing the amorphous silicic acid compound of the present invention. In the present invention, there is no particular limitation on the firing method, the conditions and the apparatus used for firing, but in order to obtain the crystalline silicic acid compound, it is necessary to maintain the heating zone set to the temperature at which the crystalline phase is generated. is there. That is, the firing temperature range is usually 500 ° C. to the vitrification start temperature, preferably 550 to 8 from the viewpoint of producing a crystalline silicic acid compound in good yield.
It is 30 ° C. If the temperature exceeds the vitrification start temperature, the silicic acid compound vitrifies and a crystallized silicic acid compound cannot be obtained, which is not suitable. Further, if the temperature is lower than 500 ° C., the crystallization of the amorphous silicic acid compound is insufficient, which is not preferable.

The firing time is usually 3
It is 0 second or more, preferably in the range of 3 minutes to 3 hours, and more preferably in the range of 5 minutes to 1 hour. If the firing time is less than 30 seconds, the heating time is insufficient, so that the temperature of the amorphous silicate compound does not rise and uniform heat treatment cannot be performed. Also, 3
If the firing is performed for a long time exceeding the time, the productivity is lowered, which is not preferable.

In the present invention, the form of the firing apparatus is not particularly limited, and examples thereof include a horizontal or vertical rotary kiln, a fluidized bed, a rigid firing furnace, a box furnace, and a belt furnace. In particular, the rotary kiln and the fluidized bed are advantageous in industrial production because the silicic acid compound is calcined while flowing and uniform crystallization proceeds. The rotary kiln and the fluidized bed may be operated either batchwise or continuously.

The composition of the crystalline silicic acid compound produced by the production method of the present invention includes, for example, the following general formula (1) xM ₂ O.ySiO ₂ .zM'O (1) (where M is Na and // Or K, and M ′ represents Ca and / or Mg.). Here, in the general formula (1), y / x = 0.5 to 3.5, z / x =
It is preferably 0 to 1.0, and more preferably y.
/X=0.5 to 2.0 and z / x = 0.005 to 1.0. These crystalline silicic acid compounds can be used for various purposes, but are preferably used as, for example, a water softening agent.

[0028]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In each example, the water content was calculated from the weight loss value due to strong heat at 700 ° C. for 1 hour, and expressed on the basis of the moisture content. The average particle size is shown as a value of cumulative 50% by weight of the sieve. The bulk specific gravity is 1
It was determined using a liter graduated cylinder without tapping.

Example 1 Three 213 kg of No. 3 water glass (K3, made by Osaka Silica Co., Ltd.)
Charge in a 00 liter stirring tank and stir at room temperature for 48%
61 kg of NaOH (manufactured by Tosoh Corporation) and Ca (OH)
₂ (made by Tosa Lime Company) 26.2 kg was added. At this time, the temperature in the tank rose to 58 ° C. due to the heat of dissolution of 48% NaOH. After stirring for 3 hours, a cloudy slurry having a water content of 55 wt% was obtained.

Of the white turbid slurry having a water content of 55 wt%,
240 kg as it is spray drying tower (Okawara Kakoki Co.,
2.2 mφ x 5.4 mH), and the blowing temperature is 260
When spray drying was performed under the conditions of ℃ and exhaust air temperature of 115 ° C., 108 kg of dry powder having a water content of 20 wt%, an average particle diameter of 297 μm and a bulk specific gravity of 0.5 kg / liter was obtained. 5 kg of this was batch type fluidized bed (Kurimoto Iron Works, 250
mmφ), and the hot air temperature at the fluidized bed inlet is 2 in 2 hours.
After raising the temperature to 00 ° C, holding at 200 ° C for 3 hours, then raising to 350 ° C for 1 hour and holding at 350 ° C for 5 hours, allowing to cool naturally, and taking out the powder, the water content was 0.6 wt%. , Average particle diameter 350 μm, bulk specific gravity 0.4 k
3.1 kg of g / l of amorphous silicic acid compound powder was obtained.

This was put into a 134 mmφ × 800 L rotary kiln (manufactured by San-Ika Heat Co., Ltd.) at 1 kg / hour and fired at 800 rpm at 3 rpm. Adhesion to the inner wall, clogging of the retort and formation of agglomerates were observed. No, stable operation was possible, and 2.9 kg of a baked product was obtained. The water content of the obtained fired product is 0 wt% and the bulk specific gravity is 0.26 kg.
/ Liter. When the obtained calcined product was analyzed by an X-ray diffractometer, the fully crystallized silicate compound Na
_{It was 2} O · 1.5 SiO ₂ · 0.5 CaO.

Example 2 100 kg of No. 3 water glass (K3, made by Osaka Silica Co., Ltd.)
In the same spray drying tower as in Example 1, the blast temperature was 260 ° C,
Drying under the condition of exhaust air temperature 132 ℃, water content 10wt%,
41 kg of dry powder having an average particle diameter of 297 μm and a bulk specific gravity of 0.3 kg / liter was obtained. 2.0 kg of this was put into a batch type fluidized bed (manufactured by Kurimoto, 250 mmφ), and the hot air temperature at the inlet of the fluidized bed was raised to 320 ° C. in 5 hours.
When the sample was kept at 320 ° C. for 2 hours and sampled, the water content was 0.9 wt%, the average particle size was 350 μm, and the bulk specific gravity was 0.
The powder was 4 kg / liter of an amorphous silicic acid compound.
Therefore, when the temperature of the fluidized bed was raised to 700 ° C. for 1 hour and calcined at 700 ° C. for 3 hours as it was, there was no adhesion to the inner wall and formation of agglomerates, and it could be calcined in a stable fluid state. The thing was obtained. The fired product thus obtained had a water content of 0 wt% and a bulk specific gravity of 0.21 kg / liter. When the obtained calcined product was analyzed by an X-ray diffractometer, it was found to be a fully crystallized silicic acid compound Na ₂ O.
It was 3.1 SiO ₂ .

Example 3 3 parts of 262 kg of No. 3 water glass (K3, made by Osaka Silica Co., Ltd.)
Charge to a 00 liter stirring tank and stir at room temperature with 48% N
38.5 kg of aOH (Tosoh) was added. At this time, the temperature in the tank rose to 52 ° C. due to the heat of dissolution of 48% NaOH. After stirring for 30 minutes, 100 kg was subjected to spray drying. The same spray-drying tower as in Example 1 was used, and the conditions were such that the air temperature was 260 ° C and the air temperature was 119 ° C. Water content was 17 wt%, average particle diameter was 149 μm, and bulk specific gravity was 0.6.
33 kg of 0 kg / l dry powder was obtained.

30 kg of this was charged into a shelf dryer,
Dry powder 2 having a water content of 1.2 wt%, an average particle diameter of 149 μm, and a bulk specific gravity of 0.63 kg / liter after being raised to 220 ° C. in 1 hour and kept at 220 ° C. for 18 hours.
5 kg was obtained. This whole amount was put into a rotary kiln (manufactured by San-Ika Kabushiki Kaisha) of 134 mmφ × 800 L at 0.9 kg / hour and baked at 3 rpm and 700 ° C., but the particles expanded by about 1.3 times in volume, but to the inner wall No deposits, clogging of the retort and formation of agglomerates were observed, stable operation was possible, and 24 kg of a baked product was obtained. The water content of the obtained fired product was 0 wt% and the bulk specific gravity was 0.40 kg / liter. When the obtained calcined product was analyzed by an X-ray diffractometer, the crystallized silicate compound Na ₂ O.2 was sufficiently crystallized.
It was SiO ₂ .

Comparative Example 1 Spray-dried powder obtained in Example 1 (water content 20 wt
%, An average particle diameter of 297 μm, and a bulk specific gravity of 0.5 kg / liter, 5 kg of which is a batch type fluidized bed (manufactured by Kurimoto)
250 mmφ), the temperature of the hot air at the inlet of the fluidized bed was raised to 150 ° C. in 2 hours, and then maintained at 150 ° C. for 4 hours,
When the powder was taken out after natural cooling, the water content was 2.
1 wt%, average particle diameter 350 μm, bulk specific gravity 0.5 kg /
3.3 kg of amorphous silicic acid compound powder was obtained.
This powder is put into a rotary kiln (manufactured by San-Ika Heat Co., Ltd.) of 134 mmφ × 800 L at 1 kg / hour and 3 rp.
Although it was baked at 800 ° C. for 15 minutes, the particles were expanded and aggregated and the retort was clogged due to adhesion to the inner wall 15 minutes after the addition, so the baking was stopped.

Comparative Example 2 Spray-dried powder obtained in Example 2 (water content: 10 wt
%, Average particle diameter 297 μm, bulk specific gravity 0.3 kg / liter) 0.4 kg were charged in the fluidized bed of Example 2, and then the temperature of the hot air blown into the fluidized bed was raised at 100 ° C./hour. When the temperature reached 400 ° C., the powder agglomerated and the flow stopped.

Comparative Example 3 Spray-dried powder obtained in Example 3 (water content: 17 wt
%, Average particle diameter 149 μm, bulk specific gravity 0.6 kg / liter) were charged as they were into a 134 mmφ × 800 L rotary kiln (manufactured by San-Ika Heat Co., Ltd.) at 0.5 kg / hour, and baked at 3 rpm and 700 ° C. After 10 minutes, expansion and aggregation of particles and clogging of the retort due to adhesion to the inner wall occurred, and firing was stopped.

Comparative Example 4 3 parts of 262 kg of No. 3 water glass (K3, made by Osaka Silica Co., Ltd.)
Charge to a 00 liter stirring tank and stir at room temperature with 48% N
38.5 kg of aOH (Tosoh) was added. At this time, the temperature in the tank rose to 52 ° C. due to the heat of dissolution of 48% NaOH. After stirring for 30 minutes, 100 kg was subjected to spray drying. The same spray-drying tower as in Example 1 was used, and the drying was carried out under the conditions of a blast temperature of 260 ° C. and an exhaust air temperature of 119 ° C., and a water content of 17 wt% WB, an average particle diameter of 149 μm, and a bulk specific gravity of 0.60 kg / liter 33 kg of powder was obtained.

30 kg of this was charged into a shelf dryer,
Dry powder 2 having a water content of 1.4 wt%, an average particle size of 149 μm, and a bulk specific gravity of 0.63 kg / liter after being raised to 220 ° C. in 1 hour and kept at 220 ° C. for 12 hours.
5 kg was obtained. The whole amount was put into a rotary kiln of 134 mmφ × 800 L (manufactured by San-Ika Kabushiki Kaisha) at 0.9 kg / hour and fired at 3 rpm at 700 ° C., and from the third hour after the start of feeding, formation of aggregates of 30 mm to 40 mm and Adhesion to the wall begins to occur, and 70 hours after 7 hours from the start of charging.
Aggregates of -80 mm were clogged at the outlet and forced to stop the experiment.

[0040]

EFFECTS OF THE INVENTION According to the present invention, it is possible to generate agglomerates due to agglomeration of particles of a silicic acid compound during firing and to form a deposit layer on the inner wall of a firing device without refluxing the fired product as in the conventional method. The crystalline silicic acid compound can be produced in a stable state without causing this.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshi Matsushita 674-66 Hironishi, Wakayama, Wakayama Prefecture

Claims (4)

[Claims] 1. A method for producing a crystalline silicic acid compound, which comprises firing a powdery amorphous silicic acid compound having a water content of 1.2 wt% (wet amount basis) or less. 2. A method for producing a crystalline silicic acid compound, wherein a silicic acid compound solution having a water content of 28 wt% (wet amount basis) or more and less than 95 wt% (wet amount basis) is dried to obtain a water content of 1.2.
A method for producing a crystalline silicic acid compound, comprising: forming a powdery amorphous silicic acid compound in an amount of wt% (wet basis) or less and then calcining the amorphous silicic acid compound. 3. The method according to claim 1, wherein the water content is 0.05 to 0.9 wt% (based on the amount of moisture). 4. The crystalline silicic acid compound produced is represented by the general formula x
M ₂ O · ySiO ₂ · zM′O (where M is Na and /
Or K, M'represents Ca and / or Mg, y /
x = 0.5 to 3.5 and z / x = 0 to 1.0. The manufacturing method of Claim 1, 2 or 3 which is a compound represented by these.