JP2934826B2 - Method for producing acid-resistant calcium silicate filter aid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The acid-resistant calcium silicate obtained by the method of the present invention, when used as a filter aid, is subjected to solid-liquid separation by subjecting difficult-to-filter slurry or dilute slurry to body feed filtration or precoat filtration. In addition, the separation and recovery of the high-clarity filtrate can be performed efficiently. Further, by selecting a raw material, a filter aid containing no organic matter or iron can be supplied stably, so that it is promising for use in pharmaceutical, food, and petrochemical fields.

[0002]

2. Description of the Related Art Solid-liquid separation in the case where filter particles are clogged due to the sticky nature of dispersed particles in a slurry, and improvement in filtration speed and separation of a clarified filtrate when the dispersed particles are fine and low in concentration. Conventionally, diatomaceous earth filter aid has been used for recovery. However, because diatomaceous earth has a different particle size and crystal form depending on its type, there is also a considerable difference in its properties as a filter aid, and there are difficulties in quality control in the filter aid manufacturing process such as grinding and classification. was there. In addition, Japan has many technical and economic disadvantages, including abundant ore reserves, few high-grade diatomite deposits, and problems with stable supply. In addition, diatomaceous earth, which is a natural sedimentary mineral, contains impurities such as organic matter and iron, and in the pharmaceutical industry, strict pretreatment is required when using diatomaceous earth to avoid contamination of the filtrate with organic matter. Is being done.
In the food and petrochemical fields, coloring of filtrate by iron has become a problem.

[0003]

The calcium silicate powder obtained by hydrothermal synthesis is a porous material like diatomaceous earth, and has a particle size and crystal form without being crushed and classified according to the purpose. Has many advantages as a filter aid, such as the ability to stably supply a filter aid that does not contain organic matter or iron by selecting raw materials. However, it also has the disadvantage that the range of use is limited due to poor acid resistance. Therefore, development of a technique for imparting acid resistance without impairing the advantages of calcium silicate has been a problem.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to overcome the drawbacks of the conventional calcium silicate-based filter aids, and as a result, have identified a silica raw material, an alumina raw material and a lime raw material. After the mixture is subjected to a hydrothermal reaction using an autoclave, the resulting calcium silicate is subjected to a carbonation treatment and then an acid treatment, so that the crystal shape is not impaired, the acid resistance is excellent, and the filtration is performed. The present inventors have found that a filter aid having improved properties can be obtained, and have accomplished the present invention based on this finding.

That is, according to the present invention, a silica raw material, an alumina raw material and a lime raw material have a molar ratio Ca / (Si + Al) of 0.2 to 1.2 and a molar ratio Al / (Si + Al) of 0.0
After mixing at a ratio ranging from 1 to 0.2 and hydrothermally reacting in an aqueous solution using an autoclave, the resulting calcium silicate is subjected to a carbonation treatment, and then treated in an acidic solution. It is another object of the present invention to provide a method for producing an acid-resistant calcium silicate filter aid characterized by performing a heat treatment at 800 to 1400 ° C.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a silica raw material in the method of the present invention, siliceous raw materials such as quartz and rice ash can be effectively used. As the alumina raw material, alumina raw materials such as bauxite and aluminum hydroxide and fly ash,
Various alumina-containing materials such as aluminum silicate raw materials such as shirasu can be used. As the lime raw material, quick lime, slaked lime and the like can be used. The silica raw material and the alumina raw material may be used separately, or may be supplied together as an aluminum silicate raw material such as fly ash or shirasu containing both silica and alumina.

When the molar ratio Ca / (Si + Al) of the mixture of the raw material of silica, the raw material of alumina and the raw material of lime is low, the formation of calcium silicate is insufficient and the effect as a filter aid is not exhibited. On the other hand, when the molar ratio Ca / (Si + Al) is high, unreacted lime raw material remains as it is, and calcium silicate with high crystallinity cannot be obtained. There is an appropriate range, and the appropriate range is the molar ratio Ca / (Si + Al)
Is 0.2 to 1.2.

When the molar ratio Al / (Si + Al) of the mixture of the silica raw material and the alumina raw material is low, the formation of calcium silicate is not hindered, but the effect of adding alumina is not exhibited. On the other hand, when the molar ratio Al / (Si + Al) increases,
Since the precipitation of fine granular crystals of the hydrogarnet becomes remarkable and impairs the filtration characteristics, the mixing ratio of the silica raw material and the alumina raw material has an appropriate range, and the appropriate range is a molar ratio of Al /
(Si + Al) is 0.01 to 0.2.

The hydrothermal reaction of a mixture of a raw material of silica, a raw material of alumina and a raw material of lime in an aqueous potassium hydroxide solution changes the crystal form of calcium silicate and suppresses the precipitation of fine granular crystals of hydrogarnet. This is for promoting the hydrothermal reaction. If the concentration of the aqueous potassium hydroxide solution is low, the effect of adding potassium hydroxide is not exhibited. On the other hand, when the concentration of the aqueous solution of potassium hydroxide is increased, there is a change in the crystal form and an effect of promoting the reaction, but there is no effect of improving the filtration characteristics corresponding to the increase in the concentration of the aqueous solution of potassium hydroxide, and the suitable range of the concentration of the aqueous solution of potassium hydroxide is not suitable. Is 0.01 to 1.0 N.

The heat treatment of calcium silicate changes the crystal structure and further improves the effect of dissolving in an acid solution. If the heat treatment temperature of calcium silicate is low,
There is no further insoluble effect of calcium silicate in acid solution due to heat treatment. On the other hand, when the heat treatment temperature is high, the insolubility effect of calcium silicate in the acid solution is large, but the calcium silicate shrinks and changes the crystal form before the heat treatment, so that it has properties as a filter aid. Is impaired, there is an appropriate range for the heat treatment temperature of calcium silicate,
The suitable temperature range is 800-1200 ° C.

After the calcium silicate is carbonated,
The acid treatment is performed by removing CaO as CaCO ₃ from calcium silicate without changing the crystal shape of calcium silicate by carbonation treatment, and dissolving CaCO ₃ from the slurry by further acid treatment. In order to remove it.

After carbonation of calcium silicate,
The acid treatment and the heat treatment are performed to change the crystal structure and further improve the insolubility in an acid solution. When the heat treatment temperature of calcium silicate is low, there is no further insoluble effect of calcium silicate in the acid solution due to the heat treatment. On the other hand, when the heat treatment temperature is high, the insolubility effect of calcium silicate in the acid solution is large, but the calcium silicate shrinks and changes the crystal form before the heat treatment, so that it has properties as a filter aid. Therefore, the heat treatment temperature of calcium silicate has an appropriate range, and the appropriate temperature range is 800 to 1400 ° C.

[0013]

Next, the present invention will be described in more detail by way of examples.

Example 1 A silica raw material, an alumina raw material and a lime raw material were mixed at a molar ratio C
a / (Si + Al) is 0.8, molar ratio Al / (Si + A)
l) is 20 for the powder mixed to be 0.05.
A weight-fold amount of water was added and mixed to prepare a slurry, which was subjected to a hydrothermal reaction with stirring in an autoclave at 180 ° C. for 8 hours to obtain a calcium silicate slurry. Next, carbon dioxide gas is blown into the calcium silicate slurry, and the calcium silicate slurry is p-pulped with hydrochloric acid.
It was adjusted to H1.5 and stirred for 10 minutes. Next, the calcium silicate is filtered, dehydrated, and dried at 120 ° C.
An acid-resistant calcium silicate filter aid was obtained.

Example 2 A silica raw material, an alumina raw material and a lime raw material were mixed at a molar ratio of C
a / (Si + Al) 0.6, molar ratio Al / (Si + A)
l) is 20 for the powder mixed to be 0.05.
A weight-fold amount of water was added and mixed to prepare a slurry, which was subjected to a hydrothermal reaction with stirring in an autoclave at 180 ° C. for 8 hours to obtain a calcium silicate slurry. Next, carbon dioxide gas is blown into the calcium silicate slurry, and the calcium silicate slurry is p-pulped with hydrochloric acid.
It was adjusted to H1.5 and stirred for 10 minutes. Next, the calcium silicate is filtered, dehydrated, and dried at 120 ° C.
An acid-resistant calcium silicate filter aid was obtained.

EXAMPLE 3 A silica raw material, an alumina raw material and a lime raw material were mixed at a molar ratio C
a / (Si + Al) is 0.8, molar ratio Al / (Si + A)
l) was added to the powder mixed to be 0.15.
A 0.3 N-weight aqueous solution of potassium hydroxide was added and mixed by weight to prepare a slurry. The slurry was stirred at 180 ° C. for 8 hours in an autoclave and subjected to a hydrothermal reaction to obtain a calcium silicate slurry. Next, carbon dioxide gas was blown into the calcium silicate slurry, and then the calcium silicate slurry was adjusted to pH 1.5 with hydrochloric acid and stirred for 10 minutes. Next, the calcium silicate was filtered, dehydrated, and dried at 120 ° C. to obtain an acid-resistant calcium silicate filter aid.

Example 4 A silica raw material, an alumina raw material and a lime raw material were mixed at a molar ratio C
a / (Si + Al) 0.6, molar ratio Al / (Si + A)
l) was added to the powder mixed to be 0.15.
A 0.3 N-weight aqueous solution of potassium hydroxide was added and mixed by weight to prepare a slurry. The slurry was stirred at 180 ° C. for 8 hours in an autoclave and subjected to a hydrothermal reaction to obtain a calcium silicate slurry. Next, carbon dioxide gas was blown into the calcium silicate slurry, and then the calcium silicate slurry was adjusted to pH 1.5 with hydrochloric acid and stirred for 10 minutes. Next, the calcium silicate was filtered, dehydrated, and dried at 120 ° C. to obtain an acid-resistant calcium silicate filter aid.

EXAMPLE 5 A silica raw material, an alumina raw material and a lime raw material were mixed at a molar ratio C
a / (Si + Al) is 0.8, molar ratio Al / (Si + A)
l) is 20 for the powder mixed to be 0.05.
A weight-fold amount of water was added and mixed to prepare a slurry, which was subjected to a hydrothermal reaction with stirring in an autoclave at 180 ° C. for 8 hours to obtain a calcium silicate slurry. Next, carbon dioxide gas is blown into the calcium silicate slurry, and the calcium silicate slurry is p-pulped with hydrochloric acid.
It was adjusted to H1.5 and stirred for 10 minutes. Next, the calcium silicate is filtered, dehydrated, and dried at 120 ° C.
The mixture was placed in an electric furnace and heated at 1200 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

Example 6 A silica raw material, an alumina raw material and a lime raw material were mixed at a molar ratio C
a / (Si + Al) 0.6, molar ratio Al / (Si + A)
l) is 20 for the powder mixed to be 0.05.
A weight-fold amount of water was added and mixed to prepare a slurry, which was subjected to a hydrothermal reaction with stirring in an autoclave at 180 ° C. for 8 hours to obtain a calcium silicate slurry. Next, carbon dioxide gas is blown into the calcium silicate slurry, and the calcium silicate slurry is p-pulped with hydrochloric acid.
It was adjusted to H1.5 and stirred for 10 minutes. Next, the calcium silicate is filtered, dehydrated, and dried at 120 ° C.
The mixture was placed in an electric furnace and heated at 1200 ° C. for 1 hour to obtain an acid-resistant calcium silicate filter aid.

EXAMPLE 7 A silica raw material, an alumina raw material and a lime raw material were mixed at a molar ratio C
a / (Si + Al) is 0.8, molar ratio Al / (Si + A)
l) was added to the powder mixed to be 0.15.
A 0.3 N-weight aqueous solution of potassium hydroxide was added and mixed by weight to prepare a slurry. The slurry was stirred at 180 ° C. for 8 hours in an autoclave and subjected to a hydrothermal reaction to obtain a calcium silicate slurry. Next, carbon dioxide gas was blown into the calcium silicate slurry, and then the calcium silicate slurry was adjusted to pH 1.5 with hydrochloric acid and stirred for 10 minutes. Next, the calcium silicate is filtered, dehydrated, dried at 120 ° C., and placed in an electric furnace at 1200 ° C.
For 1 hour to obtain an acid-resistant calcium silicate filter aid.

Example 8 A silica raw material, an alumina raw material and a lime raw material were mixed at a molar ratio C
a / (Si + Al) 0.6, molar ratio Al / (Si + A)
l) was added to the powder mixed to be 0.15.
A 0.3 N-weight aqueous solution of potassium hydroxide was added and mixed by weight to prepare a slurry. The slurry was stirred at 180 ° C. for 8 hours in an autoclave and subjected to a hydrothermal reaction to obtain a calcium silicate slurry. Next, carbon dioxide gas was blown into the calcium silicate slurry, and then the calcium silicate slurry was adjusted to pH 1.5 with hydrochloric acid and stirred for 10 minutes. Next, the calcium silicate is filtered, dehydrated, dried at 120 ° C., and placed in an electric furnace at 1200 ° C.
For 1 hour to obtain an acid-resistant calcium silicate filter aid.

The acid resistance, loose constant pressure filtration coefficient and clarity of the filtrate of the acid-resistant calcium silicate filter aid obtained in the above Examples and the commercially available heat-treated diatomaceous earth filter aid as comparative examples are shown in Table 1. It is shown in FIG. The acid resistance, the loose constant filtration coefficient of looseness and the clarity of the filtrate were measured as follows.

[0023]

[Table 1]

A 0.10 g sample was adjusted to pH 2 with hydrochloric acid using a thermostatic water bath adjusted to 50 ° C. for acid resistance.
After immersion in 100 ml and stirring and mixing for 1 hour, solid-liquid separation was performed using a centrifuge, and then SiO ₂ in the filtrate was separated.
Is a spectrophotometer, CaO is an atomic absorption spectrophotometer, Al
₂ O ₃ was measured by an EDTA titration method, and Fe ₂ O ₃ was measured using an atomic absorption spectrophotometer, and evaluated based on an elution amount per 1 g of a filter aid.

The filtration experiment was carried out by using a pressure filter having a filtration area of 19.3 cm ² and feeding various filter aids to the Frog-eye clay slurry whose pH was adjusted to 2 to loose (Rut).
h) The constant pressure filtration coefficient K ₂₀ (cm ² / sec) (K value at a slurry temperature of 20 ° C.) was determined. At that time, the filtration pressure was 0.5 kg / cm ² , the slurry concentration was 0.005, F /
The volume mixing ratio of C (filter aid / Frogme clay) was 0.5. Incidentally constant pressure filtration coefficient K ₂₀ of Ruth shows that higher filtration rate value is large is high.

The clarity of the filtrate is measured by using the transmittance measurement of a spectrophotometer. The clarity is defined as 0 when the transmittance is set to 0 and the transmittance is set to 100 when the transmittance of distilled water is set to 100. 1 degree
It was regarded as 00, and the clarity of the filtrate after the filtration experiment was evaluated.
In addition, for the measurement of the clarity of the filtrate, the filtration pressure was 0.5 kg /
cm ² , the slurry concentration was 0.005, the volume mixing ratio of F / C was 0.5, and the filtrate 2 minutes after the start of the filtration experiment was used.

[0027]

EFFECT OF THE INVENTION The solubility of the acid-resistant calcium silicate filter aid obtained according to the present invention is greatly suppressed, is comparable to existing diatomaceous earth filter aids, and has a loose constant filtration coefficient and a filtrate. It is also superior to diatomaceous earth filter aid in filtration characteristics such as clarity. In addition, it does not require crushing, classification, etc. like diatomaceous earth filter aid, and easily and stably supplies filter aid of particle size and crystal form according to the purpose by appropriately adjusting the reaction conditions. And is of high industrial value. further,
By selecting a raw material, it is possible to stably supply a filter aid that does not contain organic matter or iron, and thus it is promising for use in pharmaceutical, food, and petrochemical fields.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Eiichi Abe 807-1, Nonoshita, Sukumachi, Tosu City, Saga Prefecture Inside the Kyushu Institute of Industrial Technology (56) References JP-A-7-206423 (JP, A) Hei 7-17708 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C01B 33/24 101 B01J 20/16

Claims (4)

(57) [Claims] 1. A silica raw material, an alumina raw material and a lime raw material have a molar ratio Ca / (Si + Al) of 0.2 to 1.2 and a molar ratio Al / (Si + Al) of 0.01 to 0.2. Mixing in a ratio, using an autoclave, after a hydrothermal reaction in an aqueous solution, carbonation treatment of the resulting calcium silicate, then treated in an acidic solution, characterized by acid-resistant calcium silicate filter aid Manufacturing method. 2. The process for producing an acid-resistant calcium silicate filter aid according to claim 1, wherein the hydrothermal reaction is carried out in an aqueous solution of potassium hydroxide having a concentration of 0.01 to 1.0 N. 3. The silica raw material, alumina raw material and lime raw material have a molar ratio Ca / (Si + Al) of 0.2 to 1.2 and a molar ratio Al / (Si + Al) of 0.01 to 0.2. After mixing at a ratio and using an autoclave to cause a hydrothermal reaction in an aqueous solution, the resulting calcium silicate is subjected to a carbonation treatment, and then treated in an acidic solution.
A method for producing an acid-resistant calcium silicate filter aid, comprising heat-treating at 1400 ° C. 4. The process for producing an acid-resistant calcium silicate filter aid according to claim 3, wherein the hydrothermal reaction is carried out in an aqueous solution of potassium hydroxide having a concentration of 0.01 to 1.0N.