JPH0347533A - Preparation of acidic gas absorbent - Google Patents

Abstract

PURPOSE:To obtain an absorbent having high absorptive capacity to acidic gases by press-molding a powder and/or granules containing calcium hydroxide and hydroxides of alkali metals, immersing the molding in water, and heating while retaining a specific amount of water. CONSTITUTION:A powder and/or granules containing calcium hydroxide with hydroxide of alkali metal such as lithium, sodium, etc., and/or hydroxide of alkaline earth metal besides calcium. Then, the molding is immersed in water and heated under the condition of retaining a specific amount of water. A tablet-type acidic gas absorbent having about 900-2600g of average hardness and >=50% of surface area being solidified from the molten state is thus obtained. The gas absorbent has high absorptive capacity to acidic gases such as carbon dioxide, hydrogen chloride, etc., and no fine powder and dust is produced during transportation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing an absorbent for acidic gases such as carbon dioxide, hydrogen chloride gas, and hydrogen fluoride gas, which are used to purify air and anesthetic gases. Regarding.

[Background of the Invention Cosoda lime is a substance that is widely used as an absorbent for carbon dioxide in the air or anesthetic gas, and its manufacturing method involves soaking quicklime in a concentrated aqueous solution of sodium hydroxide.
A method of heat-treating this and pulverizing the obtained lump to make granules, or a method of mixing calcium hydroxide with other metal hydroxides and water and heat-treating the mixture, A common method is to crush lumps into granules.

However, the soda lime thus obtained is
Its physical shape is irregular and often has sharp corners. For this reason.

When this is packed in containers and shipped, the soda lime grains in the containers rub against each other during transportation and the sharp edges are worn away, resulting in the formation of fine powder or dust. There was a problem. That is, since this fine powder or dusty soda lime is inherently corrosive, a column filled with it as an absorbent was installed, for example, in order to remove carbon dioxide from anesthetic gas. When the device is used, fine soda lime powder or dust is carried away with the anesthetic gas and can be inhaled and seriously affected by the anesthetized patient. Further, when refilling the soda lime as an absorbent, dust from the soda lime is scattered indoors, causing problems such as contaminating the indoor air.

In order to solve these problems, various efforts have been made6.For example, a method of coating soda lime particles as an absorbent with a glue-like substance such as dextran, and a method of coating soda lime particles with carboxylic acid Method of adding and mixing methylcellulose (Japanese Patent Publication No. 42-20464
Examples include a method in which the shape of soda lime is made into a semicircular sphere.

However, soda lime particles produced by these methods are not necessarily satisfactory in terms of performance as an absorbent and cost. For example, particles produced by a coating method are expensive and However, depending on the glue-like material used for coating, there are problems such as a decrease in carbon dioxide absorption ability, methods using carboxymethylcellulose have problems in terms of cost, and products manufactured using a method that uses a hemispherical shape Although the generation of fine powder or dust during transportation due to the physical shape can be reduced to some extent, there are problems such as the fact that the hardness is weak and the generation cannot be sufficiently suppressed. However, there was a need for further improvement.

[Purpose of the Invention] The present invention was made in view of the above-mentioned circumstances, and is capable of generating almost no fine powder or dust during transportation, and is free from carbon dioxide, carbon dioxide,
The object of the present invention is to provide a method for producing an absorbent having a high ability to absorb acidic gases such as hydrogen chloride gas and hydrogen fluoride gas.

[Structure of the Invention] The present invention provides calcium hydroxide, hydroxides of alkali metals, and/or hydroxides of alkaline earth metals other than calcium (hereinafter abbreviated as hydroxides of alkali metals, etc.).
A powder or/and granule containing the above is pressure-molded, then impregnated with water, and then further heat-treated in a state where a certain amount of water is retained. This invention is a method for producing an acidic gas absorbent.

In addition, the present invention contains calcium hydroxide, a hydroxide such as an alkali metal, and water as main components, and has an average hardness of 900 to 2.
800. The present invention is a tablet-shaped acid gas absorbent in which 50% or more of the surface of the tablet is in a molten and solidified state.

Namely, the present inventors have developed a method to reduce the generation of fine powder and dust due to friction and vibration during transportation without reducing the ability to absorb acidic gases such as carbon dioxide, hydrogen chloride gas, and hydrogen fluoride gas, especially carbon dioxide. As a result of intensive research into a method for producing an acidic gas absorbent containing soda lime as a main component, we have developed a method for producing an acidic gas absorbent containing calcium hydroxide and hydroxides such as alkali metals by pressure molding. Hereinafter, the resulting product will be simply referred to as a molded product. ), and then impregnated with water, and then heat-treated in a state where a certain amount of water is retained. We have completed the present invention by discovering that it is possible to produce an acidic gas absorbent that is highly efficient and hardly generates fine powder or dust due to friction and vibration during transportation.

The hydroxides such as calcium hydroxide and alkali metals and water used in the present invention pose problems when the acid gas absorbent according to the present invention is used as an absorbent for carbon dioxide in air or anesthetic gas. Any material may be used as long as it does not contain any impurities (it is not necessary to use a particularly highly purified material).

The alkali metal hydroxide used in the present invention is 9
Examples include hydroxides of alkali metals such as lithium, sodium, and potassium. Examples of hydroxides of alkaline earth metals other than calcium include barium hydroxide, magnesium hydroxide, and the like. Further, these hydroxides of alkali metals and the like may be used alone or in appropriate combinations.

In order to produce an acidic gas absorbent by the method of the present invention, it may be carried out, for example, as follows.

That is, first, a mixture of powdered or/and granular calcium hydroxide and powdered or/and granular hydroxide of alkali metal, etc., or a mixture of calcium hydroxide and hydroxide of alkali metal, etc. The powder or/and granules of the mixture are press-molded into a suitable shape, for example, a tablet shape (disk shape, etc.). The acidic gas absorbent according to the present invention can be obtained by spraying and impregnating this with water by a conventional method using a sugar coating machine, coating pan, etc., and then heating it in a state where a certain amount of water is retained. is obtained.

The feature of the Il manufacturing method of the present invention lies in this hydrous heat treatment.

By performing this treatment, the surface area of the acidic gas absorbent is usually 50% or more, preferably 70% or more.

More preferably, the absorbent becomes 80% or more molten and solidified, increasing the hardness of the absorbent and, as a result, reducing the generation rate of fine powder during transportation.

When pressure molding powder or/and granules containing calcium hydroxide and hydroxide of alkali metal, etc., the mixing ratio of calcium hydroxide and hydroxide of alkali metal, etc. in the powder or granules is Although the mixing ratio is not particularly limited as long as it can work effectively when used as the acidic gas absorbent according to the present invention, it is usually 1 to 7 parts by weight of an alkali metal hydroxide to 100 parts by weight of calcium hydroxide. They are mixed appropriately so that the amount is preferably about 3 to 5 parts by weight.

In addition, the pressure molding method is not particularly limited as long as it can obtain a molded product that easily generates fine powder due to abrasion, such as having sharp corners in one part, but for example, commercially available tablets A method using a machine is preferred from the viewpoint of easy availability and operability of the machine.

The size of the molded product is not particularly limited as long as it can be packed at an appropriate density into a column etc. normally used for filling an acidic gas absorbent, but for example, when molded into a tablet, teeth.

The diameter is 1 to 10+a+a, preferably about 2 to 7IIIm, and the thickness is 1 to 10 mm, preferably 1.5 to 3 mm.
degree is more common.

Note that the pressure during molding is very important. In other words, if the pressure is increased, an acidic gas absorbent that generates less fine powder and dust but has a low ability to absorb acidic gases will be obtained, and if the pressure is decreased, acidic gas This is because an acidic gas absorbent having a high gas absorption capacity but low hardness easily generates fine powder and dust is obtained. The pressure during molding in the production of the acidic gas absorbent according to the present invention is usually 200 to 1300 kg/cm2. The pressure is preferably 250 to 800 Kg/cm2, more preferably 250 to 400 Kg/cm2. Of the molded products thus obtained, one disk-shaped tablet-shaped product usually weighs 200 to 2000 g, preferably 300 to 1
It has an average hardness of about 200, more preferably about 500 [The hardness of the molded product was measured by a conventional method using a water-filled jelly strength meter (Honya Seisakusho II). In addition, as a method for adding moisture to this molded product, for example, a method of spraying water evenly onto the molded product using a coating pan, etc. is a common method. %, preferably 14-19W
The molded product may be impregnated with water equivalent to 10% by spraying or spraying.

For heat treatment of molded products containing moisture, the heating temperature is usually from 50 to 120°C, preferably from 75 to 85°C,
The heating time is usually 1 to 24 hours, preferably 4 to 1 hour.
It may be selected appropriately from the range of 5 hours. However, when performing heat treatment, care must be taken so that the moisture contained in the molded product is difficult to evaporate and dissipate. That is, in order for the acidic gas absorbent according to the present invention to function as an acidic gas absorbent, it is essential that it retains a certain amount of water. Therefore, when heat treating, it is desirable to carry out the heat treatment in a state where the water vapor pressure is almost saturated. The simplest method to perform heat treatment in this state is, for example, to fill a sealable container or bag with the above-mentioned molded product and then seal it or close it to a sealed state.
Examples include a method of performing heat treatment in this state, but the specific method is not particularly limited as long as it is a method that can perform heat treatment under such conditions. In addition, the water content in the acidic gas absorbent according to the present invention is usually 5 to 21v.
/V%, preferably in the range of 14 to 19 W/W%.

The acidic gas absorbent according to the present invention obtained in this way not only has a high ability to absorb acidic gas, but also has the characteristics that the amount of fine powder and dust generated during transportation is extremely small. . The hardness of the acid gas absorbent according to the present invention is 1. For example, in the case of a disk-shaped tablet type, the hardness is usually in the range of 900 to 2,600 g, but in particular, those with a hardness in the range of 900 to 1,400 generate more fine powder and dust. It is more preferable because it has a smaller amount and has a higher ability to absorb acidic gases.

Furthermore, the acidic gas absorbent according to the present invention does not need to have a constant content of each component, nor does it need to have a constant weight, and furthermore, its appearance, size, etc. need not be uniform. As can be inferred from the purpose of use, it is not necessary.

The acidic gas absorbent according to the present invention may contain an indicator for detecting the remaining acidic gas absorption capacity, that is, an acid-alkali indicator such as ethyl violet, titanium yellow, Congo red, etc. If it is contained in the acidic gas absorbent according to the present invention, it will absorb acidic gas and the degree of alkalinity of the absorbent itself will decrease.

In other words, when the acid gas absorption capacity decreases, the color of the tablet changes, making it possible to determine with the naked eye when it is time to replace the absorbent. Methods for incorporating the acid-alkali indicator as described above into the acidic gas absorbent according to the present invention include, for example, a method in which a powdered acid-alkali indicator is mixed and molded at the time of molding, or a method in which a powdered acid-alkali indicator is mixed into the water to be included in the molded product. Examples include a method in which an acid-alkali indicator is dissolved, but the method is not particularly limited.

The shape of the acidic gas absorbent according to the present invention is not particularly limited as long as it does not have a shape that easily generates fine powder due to wear, such as having partially sharp corners, but specifically, for example, spherical, Examples include hemispherical, tablet-shaped, etc. Among them, tablet-shaped ones are preferred because of ease of preparation.

In addition, the shape of tablets is generally disc-shaped or disc-shaped as shown in FIG. 1(a), but for example, FIG. 1(b), (c), The shape shown in (d) may also be used. If this shape is used, the surface area of the absorbent can be increased.
! Needless to say, it is possible to improve the ability to absorb monovalent gases.

The present invention will be explained in more detail with reference to Experimental Examples, Examples, and Comparative Examples below, but the present invention is not limited by these in any way.

[Examples] Experimental Examples 1 to 6 (1) Tablet-type acid gas absorbent a Milling 6 kg of calcium hydroxide in the form of a bundle and 280 g of powdered sodium hydroxide were thoroughly mixed and then divided into 6 equal parts. Using a commercially available tableting machine, these were compressed into tablets with a diameter of
am, and molded into tablets with a thickness of 2.5 mm.

The obtained tablets were coated using a commercially available coating pan.

Water was sprayed and impregnated so that the moisture content was 17%.Then, this was placed in a plastic bag and sealed.

The mixture was left in a thermostat at 80° C. for 15 hours to obtain a 1-tablet acid gas absorbent. Incidentally, more than 80% of the surface of the obtained tablet-shaped acidic gas absorbent was in a state of being melted and solidified.

In addition, the water content (1
When the water content (1/W%) was measured, it was almost the same as the water content impregnated using a coating pan.

(2) Carbon dioxide absorption capacity test A carbon dioxide absorption capacity test of the tablet-shaped acidic gas absorbent obtained in (1) was conducted according to the following procedure.

Tablet-type acid gas absorbent 810. Using a spirometer (Cape Grystle Ventilator 1 manufactured by Nippon Medico Co., Ltd.), the absorbent canister (capacity: 950 m1) filled with
．． Oxygen gas containing 6% carbon dioxide at 6000ml/m
The time required for traces of carbon dioxide to leak into the gas exiting the absorbent canister was measured. Note that carbon dioxide in the gas was measured by gas chromatography.

The results are shown in Table 1.

(3) Measurement of hardness of tablet-type acidic gas absorbent The hardness of the tablet-type acidic gas absorbent obtained in (1) was measured according to the following procedure.

Five tablets were arbitrarily selected from among the tablet-type acid gas absorbents prepared under predetermined conditions, and the hardness of the tablets was measured in a conventional manner using a plug-in-mouth jelly strength meter (Honya Seisakusho WI).

Table 1 also shows the results of statistical processing of the measured values.

(4) Measurement of powder generation rate The powder generation rate of the tablet-shaped acidic gas absorbent obtained in (1) was measured by vibration or abrasion according to the following procedure.

Precisely weighed tablet-type acidic gas absorbent 20 was poured into a glass bottle (capacity f
This was fixed to a reciprocating shaker (manufactured by Hebashi Seisakusho), and shaken for 7 hours under conditions of shaker 11 @90 mm and a maximum number of shakes of 60 times/min. This was sieved and the incidence of powder with a size of 12 mesh or less (en/ken%) was measured.

The results are also shown in Table 1.

Comparative Example 1 Using a commercially available bulk carbon dioxide absorbent (the main component of the material is soda lime), a carbon dioxide absorption capacity test, hardness measurement, and powder generation rate were conducted in the same manner as in Experimental Examples 1 to 6. Measurements were taken.

The results are also shown in Table 1.

Comparative Example 2 Using a commercially available hemispherical carbon dioxide absorbent (the main component of the material is soda lime), a carbon dioxide absorption capacity test, hardness measurement, and powder generation were conducted in the same manner as in Experimental Examples 1 to 6. The rate was measured.

The results are also shown in Table 1.

Table 1 As is clear from the results in Table 1, the tablet-shaped acidic gas absorbent obtained by tableting at a tablet pressure in the range of 300 to 1200 Kg/cI112 by the method of the present invention is superior to commercially available carbon dioxide absorbents. It can be seen that the powder generation rate is clearly low, and the carbon dioxide absorption capacity is equal to or greater than that of commercially available carbon dioxide absorbents.

Examples 1 to 3 (1) Preparation of tablet-type acid gas absorbent After thoroughly mixing 3 powdered calcium hydroxide with 140 g of powdered sodium hydroxide, the mixture was compressed into tablets using a commercially available tablet machine. Pressure 300Kg/c 2, diameter 5mm, thickness 2
．． 5+ag+ tablets (the average hardness of the obtained tablets was 500 g), the obtained tablets were divided into three equal parts,
Using a commercially available coating pan, spray and impregnate each with water to the desired moisture content.Next, this was placed in a plastic bag, sealed, and left in a thermostat at 80°C for 15 hours. A tablet-type acidic gas absorbent was obtained. Incidentally, more than 80% of the surface of the obtained tablet-shaped acidic gas absorbent was in a state of being melted and solidified.

In addition, when the moisture content (shiba %) in the obtained tablet-shaped acidic gas absorbent was measured, it was almost the same as the moisture content impregnated using a coating pan.

(2) Using the tablet-type acidic gas absorbent obtained in Performance Test (1), Experimental Example 1
- Carbon dioxide absorption capacity test by the same method as in 6.
The hardness and powder generation rate were measured.

The results are shown in Table 2. For comparison, Table 2 also shows the results obtained in Comparative Examples 1 and 2.

Table 2 As is clear from the results in Table 2, the tablet-type acidic gas absorbents according to the present invention obtained in Examples 1 to 3 are as follows.

It can be seen that the powder generation rate is clearly lower than that of commercially available carbon dioxide absorbents, and that it has a carbon dioxide absorption capacity that is approximately equal to or greater than that of commercially available carbon dioxide absorbents.

Examples 4 and 5 (1) After thoroughly mixing 3 kg of powdered calcium hydroxide manufactured by vR and 140 kg of powdered sodium hydroxide in a tablet type acidic gas absorbent, the tablets were compressed using a commercially available tableting machine. Diameter 5III1 with glc112 at pressure 300
1. Molded into tablets with a thickness of 2.5 mm (the average hardness of the obtained tablets was 500 g). Using a commercially available coating pan, the obtained tablets were molded to a moisture content of 17%. Then, the dough was sprayed and impregnated with water, divided into two equal parts, each placed in a plastic bag and sealed, and left in a thermostat at 80°C for a predetermined period of time to obtain a tablet-shaped acidic gas absorbent. Ta. still,
The surface of the obtained tablet-shaped acidic gas absorbent is
0% or more was in a state of melting and solidification.

In addition, the water content (W
/W%) was measured and found to be almost the same as the water content impregnated using a coating pan.

(2) Performance test (Experimental example 1 using the tablet-type acidic gas absorbent obtained in 1.
- Carbon dioxide absorption capacity test by the same method as in 6.
The hardness and powder generation rate were measured.

The results are shown in Table 3.

Comparative Example 3 After thoroughly mixing 3 kg of powdered calcium hydroxide and 140 g of powdered sodium hydroxide, tablets were made into tablets with a diameter of 5 cm and a thickness of 2.0 cm at a compression pressure of 300 kg/cm2 using a commercially available tablet machine.
It was molded into a 5-inch tablet. Using a coating pan, the obtained tablets were sprayed with water and impregnated with water so that the water content was 17%, to obtain a tablet-shaped absorbent.

Using this, a carbon dioxide absorption capacity test, hardness measurement, and powder generation rate measurement were performed in the same manner as in Experimental Examples 1 to 6.

The results are also shown in Table 3. For comparison, Table 3 also shows the results obtained in Comparative Examples 1 and 2.

Table 3 As is clear from the results in Table 3, the tablet-type acidic gas absorbents according to the present invention obtained in Examples 4 and 5 have a clearly lower powder generation rate than commercially available carbon dioxide absorbents. Moreover, it is found that the carbon dioxide absorption capacity is almost equal to or higher than that of commercially available carbon dioxide absorbents.

In addition, even with the same tablet-shaped absorbent, in the case of Comparative Example 3, in which no heat treatment was performed after hydration, the carbon dioxide absorption capacity was higher than that of commercially available carbon dioxide absorbents. It can be seen that the powder generation rate is not much different from that of commercially available carbon dioxide absorbents.

Here, for reference, a photograph taken of the surface of the acidic gas absorbent obtained in Comparative Example 3 is shown in Reference Material 1, and a photograph taken of the surface of the acidic gas absorbent obtained in Examples 4 and 5 is shown in Reference Material 1. are shown in Reference Material 2 and Reference Material 3, respectively. As is clear from these Reference Materials 1 to 3, the surface of the tablet-type acidic gas absorbent becomes in a state of melting and solidification by performing the hydrous heat treatment.

[Effects of the Invention] As described above, the acidic gas absorbent according to the present invention has an acidic gas absorption capacity equal to or higher than that of conventional acidic gas absorbents, and in addition, it has a fine powder It is characterized by a very low incidence of For this reason, the acidic gas absorbent according to the present invention.

Problems with conventional products due to fine powder of soda lime.

For example, there is the problem of indoor air contamination when refilling the absorbent, and when the absorbent is used to remove carbon dioxide from anesthetic gas, the inhalation of fine soda lime powder by patients who are inhaling anesthetic gas. It is possible to eliminate danger, etc., and the contribution to this industry is enormous.

[Brief explanation of drawings]

FIG. 1 shows an example of the shape of an acidic gas absorbent according to the present invention.

Claims (5)

[Claims] (1) Pressure mold powder or/and granules containing calcium hydroxide, an alkali metal hydroxide and/or an alkaline earth metal hydroxide other than calcium, and then impregnate it with water. 1. A method for producing an acidic gas absorbent, which comprises: (2) The manufacturing method according to claim 1, wherein the heat treatment is performed in a closed system or a nearly closed state. (3) 200-1300Kg/c of powder or/and granules
The manufacturing method according to claim 1 or 2, wherein the molding is carried out under pressure of m^2. (4) Claim 1 in which the powder or/and granules are molded into a tablet shape.
3. The manufacturing method according to any one of 3 to 3. (5) Calcium hydroxide, alkali metal hydroxide and/or alkaline earth metal hydroxide other than calcium,
and a tablet-type acidic gas absorbent containing water as a main component, having an average hardness of 900 to 2,600 g, and having 50% or more of its surface melted and solidified.