JPH0881217A - Solidification of caco3 - Google Patents

Abstract

PURPOSE: To improve reactivity in reaction in an autoclave and solidification strength of CaCO3 by carrying out specific treatment before autoclave treatment in treating a raw material substance comprising CaCO3 or consisting essentially of CaCO3 in an autoclave and solidifying. CONSTITUTION: In treating a raw material substance [e.g. a substance obtained by absorbing CO3 in a combustion exhaust gas in sea water and solidifying it as CaCO3 or (Ca.Mg)CO3 ] comprising CaCO3 or consisting essentially of CaCO3 in an autoclave and solidifying, before the autoclave treatment, the raw material substance is calcined so as to partially make CaCO3 in the raw material substance into CaO, preferably >=70%, especially 80-90% residual ratio of CaCO3 . Consequently, the raw material substance is efficiently solidified at a relatively low temperature by a low-pressure autoclave reaction to give high-strength solidified material.

Description

Detailed Description of the Invention

[0001]

The present invention relates relates to a method of solidifying CaCO _3, in particular, a raw material whose main component is made or CaCO ₃ from CaCO ₃ and solidified by mild processing conditions, the high strength solidification body Regarding how to get.

[0002]

2. Description of the Related Art Since CO _{2 in} exhaust gas emitted from various industrial fields is concerned about the influence on global warming, reduction of CO _{2 in} the atmosphere is being studied. ing.

Conventionally, as a technique for reducing CO _{2 in} the atmosphere,
By absorbing CO ₂ -containing gas such as combustion exhaust gas into seawater,
There is a method of immobilizing CO ₂ as CaCO ₃ or (Ca · Mg) CO ₃ . Then, immobilized CaCO
Attempts have been made to solidify ₃ and (Ca · Mg) CO ₃ and use them effectively for construction and civil engineering materials.

As a method for solidifying CaCO ₃ , a hot pressing method, a hydrothermal hot pressing method, etc. have hitherto been proposed.

However, since the method of solidifying conventional CaCO ₃ in need of treatment conditions both conforming to generate conditions of marble and limestone is CaCO ₃ solidification of natural,
Since the processing conditions are severe conditions of high temperature and high pressure and the equipment is complicated, it is not suitable for large-scale processing, energy consumption is large, and processing cost is high.

[0006] The above solves the conventional problems, a material mainly composed of CaCO ₃ or CaCO ₃ as a method of solidifying under mild conditions, the applicant, CaCO ₃ or CaCO
A method for solidifying a substance containing ₃ as a main component by utilizing an autoclave reaction was found, and a patent application was previously filed (Japanese Patent Application No. 5-209399, hereinafter referred to as "prior application").

According to the method utilizing the autoclave treatment of the above-mentioned prior application, CaCO ₃ or a substance containing CaCO ₃ as a main component can be solidified under mild conditions of low temperature and low pressure as compared with the conventional method.

[0008]

By the way, in consideration of the use of the solidified body thus obtained as various construction and civil engineering materials, it is desired that its strength is much higher.

According to the method of the above-mentioned prior application, the present invention provides CaC
An object of the present invention is to provide a method for obtaining a solidified product useful for various purposes by increasing the strength of the solidified product obtained when solidifying a substance containing O ₃ or CaCO ₃ as a main component.

[0010]

Means for Solving the Problems The method for solidifying CaCO ₃ according to claim 1, consisting of CaCO ₃ or raw material to the CaCO ₃ as the main component a method of solidifying by autoclaving, autoclaving It is characterized in that the raw material is calcined in advance so that a part of CaCO ₃ in the raw material becomes CaO.

The method for solidifying CaCO _{3 according to} claim 2 is the method according to claim 1, wherein the raw material is calcined, mixed with a silica-based material, and then solidified by utilizing an autoclave reaction. And

The present invention will be described in detail below. In the following, for CaCO ₃ of before calcination of the raw materials in, after calcination, the ratio of CaCO ₃ remaining as CaCO ₃ without converted to CaO (% by weight), referred to as "CaCO ₃ residual ratio" .

In the method for solidifying CaCO ₃ of the present invention,
Examples of the raw material CaCO ₃ or a substance containing CaCO ₃ as a main component include CaCO ₃ or (Ca · Mg) CO _{3 obtained} by absorbing CO _{2 in} combustion exhaust gas into seawater or the like.
Examples thereof include substances obtained by immobilization, but the present invention is not limited to these substances.
A substance containing 50% by weight or more of O ₃ or CaCO ₃ as a main component (for example, dolomite having a CaCO ₃ content of 50% or more) can be effectively applied.

In the present invention, such a raw material is calcined so that a part of CaCO _{3 in} the raw material becomes CaO, and then subjected to an autoclave treatment. By calcining the raw material, a part of CaCO _{3 in} the raw material reacts with CaCO ₃ → CaO + CO ₂ to become highly reactive CaO, and the reactivity in the autoclave reaction is improved and the solidification strength is increased. .

In the present invention, the degree of calcination of the raw material is such that the residual rate of CaCO ₃ is 70% or more, particularly 80 to 90%.
It is preferable that it is such that

If the CaCO ₃ residual rate is excessively high, the effect of improving the solidification strength according to the present invention cannot be sufficiently obtained, and conversely C
If the residual rate of aCO ₃ is too small, the intended purpose of immobilizing CO ₂ cannot be achieved.

In order to calcine the raw material so as to have such a CaCO ₃ residual rate, in general, the raw material is calcined in the air at a temperature of 700 to 800 ° C. for about 0.1 to 5 hours. good.

By the way, in the present invention, the silica-based substance may be mixed with the raw material thus calcined and treated. As the silica-based material, amorphous SiO
_{In addition to 2} , crystalline SiO ₂ , silica sand, fine kira sand, diatomaceous earth, clay, etc. can be used. In this case, C--S--H (calcium silicate hydrate) is contained in the obtained solidified body. Substance) is produced, and the strength of the solidified body can be increased.

When a silica-based substance is used, if the amount of the silica-based substance used is too large, the ratio of the raw material is relatively reduced and the efficiency of effective utilization due to solidification of CaCO ₃ is reduced. The use ratio of the substance is preferably 50% by weight or less, particularly 10 to 30% by weight, based on the raw material.

In the present invention, the solidified raw material obtained by calcining the raw material and then optionally mixing the silica-based material is desired by a molding method such as press molding, cast molding, extrusion molding or cast molding. After being molded into the shape of, it is autoclaved. The solidified raw material may be subjected to autoclave treatment as it is without performing molding.

The autoclave treatment is 100 to 300.
Saturated vapor pressure (40 kg
f / cm ² or less), which is a relatively mild condition, and the treatment time is usually 2 to 20 hours, particularly 5 to 10 hours.

The solidified product thus obtained is dried under appropriate conditions, if necessary, and then used as various construction and civil engineering materials.

[0023]

SUMMARY OF According to autoclaving, the low temperature as compared with the conventional method, a low pressure of mild conditions, but the made or CaCO ₃ from CaCO ₃ can be solidified raw material whose main component, solidified by the autoclaving Prior to the above, by calcining the raw material and converting a part of CaCO ₃ into highly reactive CaO, the reactivity during the autoclave reaction is improved and the solidification strength can be increased.

When a silica-based material is mixed with the raw material after calcination, C--S--H is produced, and the strength of the obtained solidified product can be further enhanced.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Examples 1 to 8 CaCO ₃ (limestone having an average particle size of 80 μm) was calcined under the conditions shown in Table 1 so that the CaCO ₃ residual rate shown in Table 1 was obtained, and then the CaCO ₃ after this calcination was changed. SiO ₂ (average particle size 5
(μm quartz) is calcined CaCO ₃ : SiO ₂ = 80: 2
Dry mixing at a ratio of 0 (% by weight), uniaxial pressure molding (10
% Water) to obtain a molded product having a thickness of 40 mm × 10 mm × about 10 mm. Put the obtained molded body in an autoclave,
It was treated and solidified under the conditions shown in Table 1. Distilled water was added to the container (2000 cc capacity) of the autoclave.
It was charged with 0 cc and treated at a saturated vapor pressure.

The obtained solidified product was dried at 80 ° C. for 1 day, and the bending strength was measured. The results are shown in Table 1. The bending strength was measured under three-point bending strength measurement conditions with a span distance of 30 mm and a crosshead speed of 0.5 mm / min.

Comparative Example 1 A solidified body was obtained in the same manner as in Example 1 except that CaCO ₃ was not calcined, and the bending strength measurement results are shown in Table 1.

Comparative Example 2 A CaCO ₃ -CaO-SiO ₂ raw material having the same composition as the solidified raw material in Example 5 was prepared by adding CaO and SiO ₂ to CaCO ₃ which was not calcined, and this raw material was mixed. Was used in the same manner as in Example 5 to obtain a solidified body, and the bending strength measurement results are shown in Table 1.

The molding pressure is 300 to 900 kgf so that the bulk density of the molded body is about 1.95 in Examples and Comparative Examples.
/ Cm ^{2 It} was changed.

[0031]

[Table 1]

As is clear from Table 1, according to the present invention, CaCO ₃ can be autoclaved to obtain a high-strength solidified body.

The strength improving effect of the present invention is achieved by calcining the raw material and converting a part of CaCO ₃ into CaO, which is clear from the results of Example 5 and Comparative Example 2. As described above, the strength improving effect more than the case of adding CaO to CaCO ₃ from the outside and mixing is achieved.

[0034]

As described above in detail, the CaCO _{3 of} the present invention is used.
According to the solidification method of (1), CaCO ₃ or a substance containing CaCO ₃ as a main component can be easily and efficiently solidified under mild conditions of relatively low temperature and low pressure only by treatment with an autoclave which is a general apparatus. A high-strength solidified body can be obtained, and energy saving and cost saving in the CaCO ₃ solidifying technology can be achieved.

According to the present invention, CO _{2 in} combustion exhaust gas is fixed as CaCO ₃ or (Ca.Mg) CO ₃ and recovered, which is solidified at a low treatment cost to be used for construction and civil engineering materials. It can be effectively used.

Claims (2)

[Claims] 1. A consisting CaCO ₃ or raw material to the CaCO ₃ as the main component a method of solidifying by autoclaving, prior to autoclaving, CaC in raw material substance
A method for solidifying CaCO ₃ , characterized in that the raw material is calcined so that a part of O ₃ becomes CaO. 2. The method according to claim 1, wherein the raw material is calcined, mixed with a silica-based material, and then solidified using an autoclave reaction.
Solidification method of aCO ₃ .