JPS5844612B2 - Method for producing light granular calcium carbonate composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a light granular calcium carbonate composition, and more specifically, it is an object of the present invention to provide a porous granular calcium carbonate composition with high bulk and high oil absorption. be.

Traditionally, calcium carbonate has been used as a bulking agent, adsorbent, reinforcing filler,
Alternatively, it has been widely used as a modifier in fields such as rubber, plastics, paper manufacturing, agricultural chemical carriers, foods, and cosmetics.

However, in either case, the required properties are imparted to the material by pulverization.

In other words, heavy calcium carbonate, which is made by mechanically crushing limestone and pulverized, is prized as an inexpensive bulking agent, but light calcium carbonate, which is obtained by carbonating milk of lime using a chemical reaction, is produced using chemical methods. It is made into an ultra-fine powder and has the performance as a variety of modifiers, and is more expensive than mechanically pulverized heavy calcium carbonate.

On the other hand, examples of using relatively coarse particles include mechanically crushed and classified crude crystalline limestone such as kansui stone in the field of building materials, sand walls for finishing, aggregate for artificial stone, and even filler for asphalt. In the chemical field, there are fillers for adsorbing and neutralizing acidic waste gases and liquids.

However, all of the above-mentioned methods for producing granules are obtained by mechanically crushing natural limestone, and there is no example in which granules are produced by carbonation of slaked lime.

Coarsely crushed limestone is inexpensive, but it is difficult to change the physical and chemical properties of the raw stone. For example, when adsorbing and neutralizing acidic waste gas, a hard reaction product layer is formed on the surface and the internal There are problems such as difficulty in forming reactions.

In view of these points, the present invention has been developed to produce a calcium carbonate composition that has the basic physical properties of having a large specific bulk volume, a large amount of oil absorption, being porous, and exhibiting a granular shape. As a result of extensive research in order to improve the shortcomings and provide new uses, we have completed a technology for producing light granular calcium carbonate compositions that are inexpensive and of stable quality.

The light granular calcium carbonate composition of the present invention is mainly used in fields where the above-mentioned physical properties are applied, and for building materials, it is used as fine aggregate for walls and fireproofing, making use of its whiteness, lightness, and granular properties. It is used as a spray material that takes advantage of its heat-insulating properties, and as an aggregate for mortar.

Furthermore, for industrial purposes, it is also used as a carrier for pesticide granules that utilizes its highly absorbent oil and fat properties, an air filter that utilizes its porous and granular properties, and an adsorption neutralizing filler.

Next, to explain the method of the present invention in detail, in terms of the process, when digesting quicklime, the quicklime is sprinkled with digested water to which one or more compounds having acidic groups have been added, or the quicklime is added to the digested water. The process consists of a step of obtaining light granular slaked lime obtained by charging the slaked lime, and a step of carbonating the granular slaked lime with carbon dioxide gas to obtain a light granular calcium carbonate composition.

First, the activity of the raw material quicklime is not particularly limited, and industrially calcined lime can be used.

As for the particle size, it is generally better to use coarse particles if they are finely crushed (hereinafter, particles with a particle size of 0.246 to 3 mvt will be referred to as coarse particles).

) has a high yield. Next, it is important that the type of compound having an effective acidic group basically has the following two properties.

■It is soluble in water. ■Reacts with lime to produce water-insoluble salts.

Various inorganic acid salts and organic acid salts can be listed as those having the above characteristics, and acidic groups generally include phosphoric acid, sulfuric acid, boric acid, silicic acid, silicofluoride, chromic acid, citric acid, tartaric acid, and oxalic acid. It can be listed as inexpensive, and basic groups include AI, Zn, Ni, Mn, H, NH3
, Na, K, etc. can be listed.

Furthermore, the selection and amount of the compound having an acidic group may be determined depending on the purpose.

Furthermore, the higher the temperature of the digested water containing the additives, the higher the yield of coarse particles produced by digestion.

This tendency is also observed in the differences in digestion methods, with the wet digestion method in which quicklime is added to the digestion water having a higher yield of coarse particles than the dry digestion method in which quicklime is sprinkled with digested water.

In general, wet-digested lime has a smaller apparent specific gravity than dry-digested lime, and hard granular slaked lime can be obtained.

Therefore, which method to use the granular slaked lime obtained in the next carbonation step can be determined by taking into consideration the use, required characteristics, and cost.

Next, in the carbonation process, there are two methods: a dry method in which granular slaked lime is impregnated with water less than its oil absorption and carbonated while standing or stirring in a solid state, and the other is carbonation while stirring in an aqueous slurry state. Any wet method may be used.

There are no particular limitations on the carbon dioxide supply source during carbonation, but there are cases where it is used as a gaseous substance such as liquefied carbon dioxide, dry ice, and exhaust gas during lime calcination, and liquid substances such as soda carbonate and bicarbonate of soda. Cheap gaseous substances can be used advantageously.

In addition, although the carbonation rate differs between solid phase and liquid phase reactions, it is proportional to carbon dioxide partial pressure, carbon dioxide concentration, atmospheric humidity, temperature, etc., so autoclave is recommended for pressurized back oxidation to achieve a short reaction time. It is sufficient to increase the pressure of carbon dioxide gas inside the reactor, and humidification and/or heating are effective for return oxidation under normal pressure.

The degree of carbonation can be determined depending on the application and required characteristics. For example, carbonating light granular slaked lime by 5 to 10% can significantly improve the surface hardness of the granules, and also improve the atmospheric pH in a closed container. Since a decrease is observed, more light granular slaked lime with high activity is used for air filters and adsorption neutralization of acidic exhaust gas and waste liquid rather than complete carbonation, and favorable results can be obtained.

However, in the case of granular adsorption carriers for agricultural chemicals, it is better to neutralize them by converting them into calcium carbonate to prevent reaction with the agricultural chemical raw materials.

The features of the present invention will be explained in detail below using examples.

The granules used for various measurements in Examples and Comparative Examples were coarse particles with a particle size of 0.246 to 3 mm obtained by crushing with a Nara free crusher and then classifying with a sieve.

Moreover, the measurement method is as follows.

(1) Carbonation rate: Carbonic anhydride was determined according to JIS R9011-1964, and calculated using the following formula.

Carbonation rate (%) - Anhydrous carbonic acid analysis value (%) X□.

. 44 (%) (2) Apparent specific gravity: JIS K6 of calcium carbonate for rubber
223 (3) Oil absorption: JIS K for calcium carbonate for rubber
(4) PH: Measured with a glass electrode PH meter for 10% slurry.

(5) Identification of composition: powder x-ray diffraction (the anticathode used is Cu)
).

Example 1 Industrial aluminum sulfate liquid (JISK 14231970) 400T was placed in a 40J stainless steel lined iron container.
10 liters of 80°C warm water with Ll added was added as a digestive liquid, and the industrial quicklime code (JIS R9001-1958
) was crushed between 1 and 3 minutes, and 1000f of the crushed material was added, digested and aged for 3 minutes.

Next, this slurry was filtered, dehydrated, and dried in an electric heating dryer until the moisture content reached 60% on a dry weight basis to obtain light granular slaked lime.

In the carbonation process, the granular slaked lime is put into a small ribbon mixer with a capacity of 31 cm, then the raw material input port of the ribbon mixer is covered with a vinyl film, and carbon dioxide gas is poured into a liquefied carbon dioxide gas cylinder by 1. Inject at a flow rate of g/mi**, replace the air and carbon dioxide in the ribbon mixer, and react with intermittent slow stirring (20 rpm). After 2 hours, take out about half of the amount, and remove the remaining amount. was carbonated in the same manner for an additional 6 hours.

Each carbonated product was dried at 180° C. for 4 hours to obtain light granular calcium carbonate compositions of the present invention shown in Table 1.

Carbonation rate was 9.7% in 2-hour reaction and 63% in 8-hour reaction.
Therefore, identification of the granular calcium carbonate composition by powder x-ray diffraction showed a mixed pattern of Calcite and unreacted Portlancrite.

Example 2 In Example 1, when carbon dioxide gas is fed into the ribbon mixer in the carbonation step, the humidification capacity is reduced to 0.
Carbonation and drying were carried out in the same manner as in Example 1, except that carbon dioxide gas that had been sufficiently heated and humidified through a humidifying tower that had been humidified with a 5 l 7 ml electric humidifier was used to obtain the properties shown in Table 2. A light granular calcium carbonate composition was obtained.

Example 3 Light granular slaked lime obtained in the same manner as in Example 1 was dried in an electric heating dryer to produce light granular slaked lime with a moisture content of 0% and 60%, and the granular slaked lime was sieved through a 32-mesh sieve. Then, only the sieved material was packed into a basket made of a 32-mesh sieve screen to a thickness of 10 CrIL, and the dust was removed using a Venturi scrubber as a carbon dioxide gas source at 50°C and a CO2 content of 25%.
%, and a lime kiln furnace exhaust gas having a moisture content of 12% was used, and was suspended in the exhaust gas flue and carbonated for 8 hours.

Next, the obtained carbonated product was dried at 180° C. for 4 hours to obtain a light granular calcium carbonate composition having the properties shown in Table 3.

Example 4 A light granular slaked lime slurry obtained in the same manner as in Example 1 was taken into a stainless steel beaker for 21 minutes, each beaker was loaded into an autoclave equipped with a stirrer, carbon dioxide gas was pressurized into the autoclave from a liquefied carbon dioxide gas cylinder, and the autoclave was heated. After replacing the air inside with carbon dioxide, reduce the carbon dioxide pressure to 3
kg1crd, carbonated for 0.5 and 3 hours at a stirring speed of 65 rpm, and then the carbonated slurry was filtered and dehydrated, and dried at 180°C for 4 hours to obtain a light granular calcium carbonate composition having the properties shown in Table 4. I got it.

Comparative Example 1 Limestone produced in Akahaganeyama, Gifu Prefecture was medium crushed using a show crusher, and then crushed using a Nara-type free crusher, which was then sieved to obtain coarse particles with a particle size of 0.246 to 3 degrees.

※※The properties of this product are as shown in Table 5, and the apparent specific gravity was large (and only a small amount of oil absorption was obtained).

[Brief explanation of drawings]

The figure is an X-ray powder diffraction pattern of the coarse particles obtained in Inventive Example 2 of Example 1.

Claims (1)

[Scope of Claims] 1. When digesting quicklime, it reacts with lime such as phosphates, sulfates, borates, silicates, silifluorides, citrates, tartrates, oxalates, etc. and turns into water. Light granular slaked lime obtained by making an insoluble salt and digesting it with digestion water to which a compound having a water-soluble acidic group has been added is then completely or partially carbonated with carbon dioxide gas. A method for producing a light granular calcium carbonate composition. 2. A patent characterized in that, in the reaction of light granular slaked lime with carbon dioxide gas, the granular slaked lime is impregnated with water in an amount less than its oil absorption capacity, or is carbonated in an anhydrous solid state while standing still or being stirred. A method for producing a light granular calcium carbonate composition according to claim 1. 3. The method for producing a light granular calcium carbonate composition according to claim 1, wherein the light granular slaked lime is carbonated while being stirred in an aqueous slurry state.