JPS5842129B2 - Method for producing calcium silicate hydrate crystals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing calcium silicate hydrate crystals, and more specifically, a method for producing calcium silicate hydrate crystals mainly consisting of tobermorite crystals using blast furnace slag as a raw material. It is related to.

Calcium silicate hydrate crystal contains CaO-8in2-H
There are various crystal forms depending on the composition of 2O,
Among them, tobermorite crystals are excellent in terms of heat insulation, fire resistance, strength, etc. when formed into a molded body.

However, as a general method for producing tobermorite crystals, a method is known in which an aqueous slurry of a calcium raw material and a silicic acid raw material is subjected to pressure and heat treatment to perform a hydrothermal synthesis reaction.

It was considered necessary to use high-grade silicic acid raw materials with an alumina content of about 5% by weight or less, such as diatomaceous earth, silicate quartz, and silica stone.

That is, in the production of tobermorite crystals, for example, the presence of a small amount of alumina of about 5% by weight is said to be desirable as it has the effect of increasing the reaction rate, but when the alumina content is 10% by weight or more, This is because when a silicic acid raw material is used, undesirable hydrogarnet is produced as a by-product, which impairs the excellent physical properties of tobermorite crystals.

However, blast furnace water slag, which is a large amount of by-product from the pig iron manufacturing process, generally has the following composition, and although it is an inexpensive raw material containing appropriate amounts of CaO and SiO2 for manufacturing tobermorite crystals, most of it is Because it contains 10% by weight or more of alumina, it could not be used as a raw material for producing tobermorite crystals for the reasons mentioned above.

Composition of blast furnace water slag CaO: 35-50% by weight SiO2: 30-40 〃 Al2O3: 5-20 〃 MgO: 5-10 As a result of intensive studies on the production method of calcium silicate hydrate crystals that can be used as
It was discovered that calcium silicate hydrate crystals mainly consisting of tobermorite crystals could be obtained without producing hydrogarnet as a by-product even if 0% by weight or more of blast furnace water slag was used, and this led to the completion of the present invention.

That is, the gist of the present invention is to provide a method for producing calcium silicate hydrate crystals by pressurizing and heating a water slurry of blast furnace water slag, in which blast furnace water slag having an alumina content of 10% by weight or more is used as a raw material. , a method for producing calcium silicate hydrate crystals, characterized by carrying out pressure and heat treatment together with a water-soluble inorganic compound of an alkali metal of at least 5% by weight (calculated as alkali metal hydroxide) based on the raw material solid content in the slurry. Exists.

Detailed explanation of the present invention: 1. In the present invention, the alumina content, which is a by-product in the process of producing pig iron from iron ore, is 10% by weight.
The above blast furnace water slag is used as a raw material.

Blast furnace water slag is usually in powder form suspended in about 5-30 parts by weight of water and subjected to hydrothermal synthesis reaction as a slurry. This is preferable because the reaction rate is increased.

In addition, depending on the type of blast furnace water slag, the molar ratio of CaO/5i02 may change to the formation region of tobermorite crystals (CaO/SiO2).
2 molar ratio is 0.5 to 1.5. Preferably 0.7-1.0
), but in such cases, the molar ratio of Ca O / S t 02 in the raw material slurry may be adjusted within the above range using a conventionally known lime raw material and/or silicic acid raw material.

In the present invention, blast furnace water slag having a CaO/5i02 molar ratio in the above-mentioned tobermorite crystal formation region and an alumina content of 10% by weight or more is used as a raw material, and this is hydrothermally heated together with a specific amount of a water-soluble inorganic compound of an alkali metal. It is an essential requirement that it be subjected to a synthetic reaction.

Examples of water-soluble inorganic compounds of alkali metals include hydroxides and silicates of sodium and potassium.

Sulfates, nitrates, chlorides and the like are suitable, and specific examples include sodium hydroxide, potassium hydroxide, water glass and the like.

What is the amount of water-soluble inorganic compounds of alkali metals added?

If this amount is too small, the by-product of hydrogarnet cannot be suppressed, so it is at least 5% by weight in terms of alkali metal hydroxide based on the solid content of the raw material in the slurry.
It should be 1 usually.

It is preferable to use about 5 to 30% by weight.

The hydrothermal synthesis reaction is carried out according to a conventional method using a pressure-resistant closed container such as an autoclave, and the reaction rate is 4 to 60 kg/ff1G.
The stirring treatment is carried out under a pressure of 0.5 to 8 hours.

After the reaction is completed, calcium silicate hydrate crystals mainly composed of tobermorite crystals can be obtained by depressurizing and separating the mixture.

As detailed above, according to the present invention, cheap blast furnace water slag, which is produced in large amounts as a by-product in the pig iron manufacturing process, can be used as a raw material, which is different from the conventional method where high-grade silicic acid raw materials such as diatomaceous earth had to be used. It is extremely advantageous compared to the law.

Furthermore, conventionally, blast furnace water slag has only been used to a limited extent by mixing it with cement, fertilizer, etc., and most of it has been disposed of as coastal reclamation at industrial sites.

With the current situation where there is a strong need for the development of new usage methods in line with environmental regulations, the present invention provides a new usage method for blast furnace water slag, and in this respect, its industrial value is extremely large. be.

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

In Examples and Comparative Examples, "parts" means parts by weight.

Further, the composition of the raw materials used is shown in Table 1, and the results of X-ray diffraction of the obtained crystals are shown in Tables 2 and 3.

Note that the measurement conditions for %X-ray diffraction are as follows.

Characteristic X-ray CuKa slit l' -0,3-10 Filter: Ni filter Applied voltage 30 Kv Applied current 15 mA Time constant, 1 second Example l Blast furnace A raw material slurry was prepared by adding 81.6 parts of water slag and 18.4 parts of silica stone.

This slurry was placed in an autoclave at a pressure of 8 kg/cr.
A hydrothermal synthesis reaction was carried out for 8 hours with stirring at 1G and 175°C.

After the reaction was completed, the pressure was decompressed and the crystals obtained were subjected to X-ray diffraction, and the results are shown in Table 2.

Examples 2 to 6 and Comparative Examples 1 to 5 Hydrothermal synthesis reactions were carried out according to the method of Example 1 under the conditions shown in Tables 2 and 3.

The X-ray diffraction results of the obtained crystals are shown in each table.

As is clear from the results in Tables 2 and 3.

Using blast furnace water slag with an alumina content of 17.0% by weight as a raw material, according to the present invention, at least 5% by weight of sodium hydroxide or an equivalent amount of water glass is added to the raw material solid content in the raw material slurry. If the reaction is carried out by adding it, a calcium silicate hydrate crystal mainly composed of tobermorite crystals can be obtained.

In addition, as reference materials, electron micrographs (magnification: 9000) of each crystal obtained in Examples and Comparative Examples are shown.

Reference material 1) is a photograph of a tobermorite-based crystal obtained by the method of Example 4, and reference material (2) is a photograph of a crystal mainly composed of hydrogarnet obtained by the method of Comparative Example 4. This is a photo.

[Brief explanation of drawings]

The attached drawing is a graph showing the results of X-ray diffraction. A is a graph for the crystal obtained in Example, and B is a graph for the crystal obtained in Comparative Example 1. T in the graph. (The peak of stobamorite (C5S6H5) crystal. HG indicates the peak of hydrogarnet (C3ASH6) crystal, and the peak of CCI''lCaCO3 crystal.

Claims (1)

[Claims] 1. A method for producing calcium silicate hydrate crystals by pressurizing and heating a water slurry of blast furnace water slag. Using blast furnace slag as raw material with an alumina content of 10% by weight or more,
The production of calcium silicate hydrate crystals is characterized in that this is subjected to pressure and heat treatment together with a water-soluble inorganic compound of an alkali metal of at least 5% by weight (calculated as alkali metal hydroxide) based on the raw material solid content in the slurry. Method.