JPH08109017A - Slaked lime and its production - Google Patents

Abstract

PURPOSE: To obtain a high quality slaked lime free from impurities accumulated on its surface layer, prevented in the presence of a left industrial salt, reduced in bulk density, and enhanced in porosity. CONSTITUTION: Natural lime 1 is mixed with an industrial salt and subsequently subjected to a high temperature calcination treatment in a reducing atmosphere. The surface layer of the produced small massive reduced salt calcined lime 13 is ground off with a grinder 14, and the left reduced salt calcined and shaved lime 15 is subjected together with a theoretical digestion amount of ion exchange water 17 to a hyclrothermal hydration treatment in a closed high pressure digestion machine 16 to obtain the high quality calcined lime 18. A solid carbon material 12 comprising coal and coke is used as a fuel for calcining the lime 1, and an alkali or alkaline earth salt such as sodium chloride, potassium chloride, magnesium chloride or calcium chloride is used as the industrial salt. The elevated temperature, the elevated pressure and the reaction-completion time in the closed type high pressure digestion machine are 150200 deg.C 10-20 (kg/cm<2> ), and 7-10hr, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-purity slaked lime obtained by adopting a quick lime having a novel structure as a raw material and subjecting this raw material to hydrothermal hydration, and a method for producing the same.

[0002]

2. Description of the Related Art Slaked lime is digested by adding water to quick lime (CaO), the main component of which is calcium hydroxide Ca.
(OH) ₂ . This slaked lime has been used in a wide range of fields for a long time. For example, in the case of environmental problems such as pollution, it is used as a flue gas desulfurization material to prevent air pollution or as a neutralization treatment material for various factory wastewater. It is used as a soil conditioner for volcanic ash soils and as a wall material for buildings. As a familiar example, slaked lime is used as a coagulant for konjac.

In particular, slaked lime is often applied for the purpose of easily decomposing hardly decomposable organic nitrogen in soil. Recently, it has also been used in fields such as plastics, rubber, agricultural chemicals, and whitening materials. In particular, high-quality slaked lime with high purity in terms of chemical composition is widely used in the fields of chemical reagents, food additives, etc., and is highly evaluated in terms of characteristics.

In the generally known method for producing slaked lime, as shown in the production process diagram of FIG. 4, naturally occurring limestone 1 (CaCO ₃ ) is used as a raw material. 1 is crushed to form a small lump, and then fired at a high temperature of about 1000 ° C. in an oxidizing atmosphere based on the firing means 2 using heavy oil or the firing means 3 using coal or coke, and pyrolyzed to give quicklime 4. The method of adding the industrial salt 5 to the limestone which has been made into a small lump by the above-mentioned coal or coke firing means 3 is also partially adopted.

Then, the obtained lump of quick lime 4 is hydrated with water 7 injected by using atmospheric pressure open digestion means 6 to obtain each powder of alkaline heavy oil burned slaked lime 8 or salt burned slaked lime 9. Here, "salt-baking" refers to a method in which industrial salt 5 is added and fired when a small lump of limestone is pyrolyzed.

[0006]

However, with such a conventional method for producing slaked lime, it is difficult to obtain high quality slaked lime for each of the following reasons. That is, the limestone 1 is naturally produced all over the country and is used in large amounts as various industrial raw materials, but its quality varies widely, and the limestone 1 is burned at high temperature using heavy oil or coal / coke as fuel. When salt-baked, the quick-lime obtained in the baking furnace is in an atmosphere of zero oxidation, and the quick-lime obtained does not have a characteristic that the bulk specific gravity is small and the porosity is large, which is a characteristic of the salt-baking effect.

There is also a method of firing in a reducing atmosphere. In this method, the ash content of solid fuel is deposited on the surface of the quicklime 4 obtained, and when the industrial salt 5 is further added, it is added. Since the industrial salt remains, there is a problem that impurities are accumulated in the surface layer of quicklime 4.

Furthermore, when the quicklime 4 thus obtained is digested by a hydration reaction, it is 1.5 times the theoretical amount of water to be digested under the conditions of atmospheric pressure release.
Although twice the amount of water is added for digestion, the resulting slaked lime powder aggregates into flocs due to uneven distribution of excess water, and there are many coarse particle residues due to undigested quicklime remaining due to insufficient water. is there. In particular, groundwater, industrial water, or tap water is usually used as the digestion water for quicklime 4, but these waters have chlorine and many dissolved substances in terms of water quality, which is also a factor that deteriorates the quality.

The inside of the above-mentioned atmospheric pressure release type extinguishing means 6 is
A large amount of water vapor is generated due to the exothermic phenomenon caused by the digestion reaction of quicklime 4, and since the produced slaked lime fine powder is mixed in this water vapor, there is a problem that it cannot be released into the atmosphere as it is from the viewpoint of pollution prevention. is there.

Therefore, the present invention solves the problems of the conventional slaked lime and the method for producing the slaked lime, prevents impurities from accumulating in the surface layer, and prevents the residual industrial salt to have a bulk specific gravity. The purpose is to obtain high quality slaked lime which is small and has high porosity.

[0011]

[Means for Solving the Problems] To achieve the above object, the present invention comprises adding industrial salt to naturally produced limestone and subjecting it to a high-temperature calcination treatment in a reducing atmosphere to obtain reduced salt-baked quicklime, which is in the form of small blocks. Disclosed is a slaked lime obtained by grinding and removing a surface layer of salt-baked quicklime, and then hydrothermally hydrating reduced salt-baked quicklime with ion-exchanged water of a theoretical amount of digested water in a closed high-pressure digester, and a method for producing the same.

A solid carbonaceous material composed of coal and coke is used as a fuel for burning the limestone, and an alkaline salt or alkaline earth salt such as sodium chloride, potassium chloride, magnesium chloride or calcium chloride is used as the industrial salt. I am using. The temperature rise in the closed high-pressure digester is 150 ° C to 200 ° C, and the pressure rise is 10 to 20 (Kg / c).
m ² ), the reaction completion time is 7 to 10 hours.

[0013]

According to such slaked lime and its manufacturing method, limestone is charged into a calcination furnace to use solid carbonaceous material composed of coal and coke as a fuel, and industrial salt is added to the calcination furnace to keep the inside of the furnace at a reduced zero temperature and high temperature. By firing, a small lump of reduced salt-baked quicklime is obtained, and the surface layer of the reduced salt-baked quicklime is ground away to obtain reduced salt-baked quicklime.

Next, the reduced salt burned quicklime thus obtained is charged into the closed high-pressure digester as a small lump, and then a theoretical amount of ion-exchanged water is poured, and then rotationally driven to perform hydrothermal hydration treatment. By doing, alkaline high quality slaked lime is obtained. The reduced salt-baked quicklime has a low bulk specific gravity,
The surface layer is easy to grind because it is porous and soft. Further, it becomes possible to obtain high quality slaked lime by a hydrothermal hydration reaction in which a theoretical amount of water is added to reduced salt burned quick lime in a closed type high pressure digester.

[0015]

EXAMPLES Specific examples of slaked lime and a method for producing the same according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the basic manufacturing process of this embodiment, and the outline of the manufacturing process of slaked lime will be described based on this drawing.

Reference numeral 1 is a naturally produced limestone, 11 is a sake bottle type vertical furnace used in the firing process of the limestone 1, 14 is a grinder used in the surface treatment process of reduced salt baked quicklime 13, and 16 is reduced salt baked quicklime 15. It is a closed high-pressure digester used in the hydrothermal hydration reaction step of.

2 (A) and 2 (B) show an example of the above-mentioned closed type high pressure digester 16, 21 in the figure is a pressure tank made of stainless steel.
And a water injection valve (not shown) for the ion-exchanged water 17 are attached. Reference numeral 23 denotes a pedestal, and a geared motor 24 is arranged below the pedestal 23. Between the output shaft 24a of the geared motor 24 and a pulley provided at each end of a rotary shaft 26 protruding from the pressure tank 21. A belt 25 is hung. 27 is a pressure gauge, 28
Is a safety valve, and 29 is a thermometer.

In this embodiment, naturally produced limestone 1 is used as a raw material, and this limestone 1 is charged into a sake bottle type vertical furnace 11 to use a solid carbonaceous material 12 made of coal / coke as a fuel, and an industrial salt 5 is added to the furnace. Keeping the inside of the atmosphere at a reduced atmosphere and firing at high temperature (CaCO
₃ → CaO + CO ₂ ↑). In this way, a small lump of reduced salt baked quick lime 13 is obtained, the surface layer of this reduced salt baked quick lime 13 is removed by a grinding machine 14 in the next stage, and reduced salt burned quick lime 15 is obtained.
Get. In this grinding step, the surface layer of reduced salt baked quicklime 13 is removed by about 50% by weight. As the industrial salt 5, an alkali salt or an alkaline earth salt such as sodium chloride, potassium chloride, magnesium chloride or calcium chloride is used.

Next, the reduced salt burned quicklime 15 thus obtained is charged into the pressure tank 21 of the next-stage closed high-pressure digester 16 in the form of a small lump, and then the theoretical digested water amount is supplied from the water injection valve into the pressure tank 21. Of high-purity ion-exchanged water 17 is injected, and the geared motor 24 is started to activate the geared motor 2.
The pressure tank 21 is rotationally driven as indicated by an arrow A by the action of the belt 25 that is wound between the pulleys provided between the output shaft 24a of No. 4 and the rotation shaft 26 of the pressure tank 21.
As a result, the reduced salt burned quicklime 15 is hydrothermally hydrated to obtain alkaline high quality slaked lime 18.

The reduced salt baked quicklime 13 has a low bulk specific gravity and is porous and soft, so that the grinding machine 14 of the next stage is used.
It becomes easy to grind the quicklime surface layer in the grinding step. Closed type high pressure digester 16 for further hydrothermal hydration treatment
Since it is a completely closed system, high quality slaked lime can be obtained by the hydrothermal hydration reaction in which the theoretical amount of water is added to the reduced salt burned quick lime 15.

In the above hydrothermal hydration reaction treatment, as shown in the hydrothermal hydration reaction time and temperature / pressure curve of FIG. 3, the temperature and pressure in the pressure tank 21 rapidly increase due to the generation of heat of digestion reaction. Although it rises, the temperature and pressure gradually decrease with the progress of the reaction, and the hydrothermal hydration reaction is completed when the pressure tank 21 reaches normal temperature and pressure. At this time, the temperature rise in the pressure tank 21 is 150 ° C. to 200 ° C., and the pressure rise is 1
It is 0 to 20 kg / cm ² , and the reaction completion time is 7 to 10 hours.

Due to the combined action and effect of the hydrothermal hydration reaction step {CaO + H ₂ O → Ca (OH) ₂ } by the closed type high pressure digester 16, it becomes possible to produce high quality slaked lime 18.

The physical characteristics of the reduced salt burned quicklime 15 are that the digestion exothermic reaction does not start for a few minutes after the addition of water, so that the water injection valve of the digester can be closed and the steam containing dust is released to the outside of the machine. It is effective in preventing dust pollution.

Specific examples of the present invention will be described below. [Example 1] In order to confirm the effect of calcining limestone and the effect of addition or non-addition of industrial salt / magnesium chloride on the properties of quicklime, liquor sampled from Inabu, Nankoku City, Kochi Prefecture was used as a raw material, and a sake bottle furnace 11 Baking temperature 1000 ℃ ± 5
Quick lime was prepared under the condition of 0 ° C. and the presence or absence of addition of 0.3% of magnesium chloride as an industrial salt in the furnace atmosphere in an oxidized and reduced state.

The bulk specific gravity of the quicklime thus obtained (g / m
l), porosity (%) and hardness were measured. The results are shown in Table 1, and an electron micrograph (× 6000 times) showing the structure of quick lime crystals calcined in an oxidizing atmosphere is shown in FIG. 6, and an electron micrograph showing the structure of quick lime crystals salt baked in a reducing atmosphere ( × 3500 times) is shown as FIG.

[0026]

[Table 1]

According to Table 1 and photographs 1 and 2, quicklime obtained under the condition of adding 0.3% of magnesium chloride in a reduced atmosphere has a low bulk specific gravity, has the highest porosity, and is soft in terms of hardness. It was confirmed that there was a difference in physical properties due to the effect of salt baking.

Example 2 Next, in order to confirm the effect of grinding the surface layer of the obtained quicklime by the grinder 14, hard quicklime and soft calcium obtained under the firing conditions according to Example 1 above. The result of grinding the surface layer of both quicklimes using a rotary wire brush grinder for quicklime will be described.

In practice, it is practically impossible to grind the surface layer of hard quicklime, but it is easy to grind the surface layer of soft quicklime salt-baked in a reducing atmosphere, and the difference in the grindability between them is remarkable. Met. Table 2 shows the results of analysis of the impurity content of quicklime powder obtained by cutting the surface layer of reduced salt-baked quicklime by 40% based on the total weight ratio and the mass of quicklime particles cut by 60% by weight ratio.

[0030]

[Table 2]

According to Table 2, chloride (C
l), acid insolubles, and iron dioxide (Fe ₂ O ₃ ) contents were much lower in the reduced salt baked quicklime with the surface layer cut, and it was confirmed that the impurities of the surface layer were removed by grinding. . In particular, the iron dioxide content was significantly reduced by the deferring reaction of iron content containing limestone by reducing salt baking and the combined effect of cutting iron content accumulated in the surface layer, and high quality quicklime was obtained.

[Example 3] Next, in the hydrothermal hydration reaction by the closed type high pressure digester 16, in order to confirm the influence on the purity and the impurity content of the obtained slaked lime, the reduction obtained in the above Example 2 was performed. 30 kg of salt-baked quicklime mass 0.264
The mixture was put into a m ³ closed type high-pressure digester 16, and 9.5 liters of ion-exchanged water 17 corresponding to the theoretical amount of digested water was injected, and immediately thereafter, a hydrothermal hydration reaction was started at a speed of 2 revolutions per minute. The maximum temperature and pressure in the closed high-pressure digester 16 is 20
The temperature was increased to 16 Kg / cm ² at 0 ° C., rotation was stopped after 7 hours, the slaked lime produced in the machine was taken out, and sieved with a 100-mesh vibrating sieve to obtain a slaked lime powder.

Table 3 shows the results of chemical analysis of the purity and trace impurities of the obtained slaked lime by the method specified in JIS K8575 (1994).

[0034]

[Table 3]

Comparative Example 1 in Table 3 is an analysis of slaked lime obtained by pouring tap water in an amount of twice the theoretical amount of digested water by a conventional atmospheric pressure open type digester for reduced salt baked quick lime. The result is shown. In this Comparative Example 1, the purity of slaked lime is lower than that of the slaked lime obtained in Example 3, and the content of hydrochloric acid insolubles, chlorides and sulfates is large, and the slaked lime is below the standard value of JIS reagent special grade. is there.

On the other hand, the slaked lime obtained in Example 3 was high in purity, the impurities in many items were extremely small, and high quality slaked lime exceeding the standard value of JIS reagent special grade was obtained.

Example 4 Slaked lime has been used as a coagulant for konjac for a long time. Therefore, high quality slaked lime 1 obtained by hydrothermal hydration treatment of reduced salt burned quicklime 15
In order to evaluate the practicality of No. 8, a konjac production test and a trial konjac sensory evaluation test were performed using this high-quality slaked lime 18.

In the production test, first, 500 gram of konjac refined powder as a raw material was mixed with 15 liters of kneading water, stirred for 5 minutes, and aged for 1 hour. Separately, 30 g of the high-quality slaked lime obtained in this example was added to 1.5 liters of water and stirred to prepare a slaked lime emulsion, and the slaked lime emulsion having a 2% concentration was added to the swollen konjac after aging. In addition, 5 liters of water was further added, and the mixture was kneaded for 5 minutes. After that, it was put into a mold and shaped, immersed in hot water of 85 ± 2 ° C. for 15 minutes, and further aged for 10 hours in slightly hot water to obtain a trial konjac.

A sensory evaluation test was conducted by a questionnaire survey by 28 consumers on the trial konjac obtained as described above, and the konjac maker 15
The company was requested to carry out a trial test of the high quality slaked lime according to this example, and comprehensively evaluated. As a result, it was found that the high quality slaked lime of this example has the following features as compared with the conventional slaked lime for konjac.

First, since the high-quality slaked lime obtained in this example is excellent in hydrophilicity, the slaked lime is well dispersed in water when the slaked lime emulsion is prepared, and the powder in the conventional example aggregates. The so-called "mamako" phenomenon does not occur at all. Therefore, the workability during konjac production and the emulsion of slaked lime are improved.

Further, in the sensory test of the konjac product, the lime odor peculiar to the conventional konjac disappeared, and a preferable result as a favorite food was obtained.

[0042]

As described above in detail, according to the slaked lime and the method for producing the same according to the present invention, an industrial salt is added to a calcination furnace of limestone by using solid carbonaceous material as a fuel, and the inside of the furnace is kept at a reduced atmosphere. While baking at high temperature, a small lump of reduced salt-baked quicklime is obtained, the surface layer of this reduced salt-baked quicklime is ground and removed to obtain reduced salt-baked quicklime, which is charged into a closed high-pressure digester. High-quality slaked lime can be obtained by performing hydrothermal hydration treatment with the theoretical amount of deionized water. The obtained slaked lime is characterized by having a low bulk specific gravity and being porous, and is particularly useful in the fields of chemical reagents, food additives, etc., which require high purity in terms of chemical composition. In particular, the obtained slaked lime is a Japanese Industrial Standard (JIS) reagent special grade (K8575-19).
94) The standard value is satisfied.

In the present invention, the hydrothermal hydration reaction is carried out by adding the theoretical amount of water to the reduced salt burned quick lime in the closed type high-pressure digester, so that the obtained slaked lime powder has uneven distribution of excess water or lack of water. It has the feature that no coarse particle residue is generated due to the remaining undigested quick lime due to the fact that ion-exchanged water is used as the quick lime digestion water, and dissolved substances such as chlorine due to the use of ordinary groundwater, industrial water or tap water. It is possible to improve the quality by eliminating the effect of.

Further, most of the steam generated by the quick lime digestion reaction in this embodiment is consumed as reaction water with the elapse of the reaction time, and excess steam does not remain. Therefore, there is no release of water vapor containing slaked lime dust to the outside of the closed high-pressure digester, and the effect of causing no pollution can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic manufacturing process of this embodiment.

FIG. 2 is a front view of the sealed high-pressure digester used in this example.

FIG. 3 is a graph showing a hydrothermal hydration reaction time and a temperature / pressure curve in a closed high-pressure digester.

FIG. 4 is a block diagram showing a conventional method for producing slaked lime.

FIG. 5 is an electron micrograph showing the structure of a quicklime crystal that has been salt-baked in a reducing atmosphere.

FIG. 6 is an electron micrograph showing the structure of a quicklime crystal fired in an oxidizing atmosphere.

[Explanation of symbols]

 1 ... Limestone 5 ... Industrial salt 11 ... Sake type furnace 12 ... Solid carbon material 13 ... Reduced salt grilled quick lime 14 ... Grinding machine 15 ... Reduced salt burned quick lime 16 ... Closed type high pressure digester 17 ... Ion exchange water 18 ... High quality slaked lime 21 ... Pressure tank 22 ... Input / discharge port 23 ... Stand 24 ... Geared motor 24a ... Output shaft 25 ... Belt 26 ... Rotation shaft 27 ... Pressure gauge 28 ... Safety valve 29 ... Thermometer

[Procedure amendment]

[Submission date] December 7, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

However, with such a conventional method for producing slaked lime, it is difficult to obtain high quality slaked lime for each of the following reasons. That is, the limestone 1 is naturally produced all over the country and is used in large quantities as various industrial raw materials, but its quality varies widely. When baking with salt, the baking furnace oxidizes
Cut a the quick lime obtained because囲気small bulk specific gravity, which is a feature of grilled effect is not observed feature that the porosity is large.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

[0011]

Means for Solving the Problems The present invention to achieve the above object, the limestone naturally occurring by adding industrial salt and high temperature firing process in a reducing atmosphere as a reducing grilled quicklime small bulk, this reduction Disclosed is a slaked lime obtained by grinding and removing a surface layer of salt-baked quicklime, and then hydrothermally hydrating reduced salt-baked quicklime with ion-exchanged water of a theoretical amount of digested water in a closed high-pressure digester, and a method for producing the same.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013]

In accordance with the according slaked lime and a manufacturing method thereof, a solid carbonaceous material by introducing a limestone burning furnace comprising coal-coke as fuel, while retaining further adding industrial salt in the furnace in a reducing atmosphere hot By firing, a small lump of reduced salt-baked quicklime is obtained, and the surface layer of the reduced salt-baked quicklime is ground away to obtain reduced salt-baked quicklime.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

FIG. 2 shows an example of the closed high-pressure digester 16, in which 21 is a pressure tank made of stainless steel, and the pressure tank 21 has an ion exchange with the charging / discharging port 22 of the quicklime 15. A water injection valve (not shown) for water 17 is attached. Reference numeral 23 denotes a pedestal, and a geared motor 24 is arranged below the pedestal 23. Between the output shaft 24a of the geared motor 24 and a pulley provided at each end of a rotary shaft 26 protruding from the pressure tank 21. Belt 2
5 is hung. 27 is a pressure gauge, 28 is a safety valve, 2
9 is a thermometer.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

In this embodiment, naturally produced limestone 1 is used as a raw material, and this limestone 1 is charged into a sake bottle type vertical furnace 11 to use a solid carbonaceous material 12 made of coal / coke as a fuel, and an industrial salt 5 is added to the furnace. holding the inner to the reduction atmosphere at a high temperature calcination (CaCO
₃ → CaO + CO ₂ ↑). In this way, a small lump of reduced salt baked quick lime 13 is obtained, the surface layer of this reduced salt baked quick lime 13 is removed by a grinding machine 14 in the next stage, and reduced salt burned quick lime 15 is obtained.
Get. In this grinding step, the surface layer of reduced salt baked quicklime 13 is removed by about 50% by weight. As the industrial salt 5, an alkali salt or an alkaline earth salt such as sodium chloride, potassium chloride, magnesium chloride or calcium chloride is used.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

Specific examples of the present invention will be described below. In Example 1 to confirm the effect on the properties of the lime with the addition presence of sintering atmosphere and industrial salt Magnesium chloride limestone, as raw materials limestone taken from Ino Kochi Nankoku, sake bottle type vertical furnace 11 Baking temperature 1000 ℃ ± 5
In the range of 0 ° C., the furnace atmosphere is created quicklime under conditions with and without magnesium chloride 0.3% addition of the industrial salt in a reduced state and oxidation.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

[0026]

[Table 1]

[Procedure Amendment 10]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

[0027] Table 1 and according to the picture 1, quick lime obtained under the condition of adding magnesium chloride of 0.3% under reducing atmosphere porosity is most often on the bulk specific gravity is small, and, in softer in hardness surface It was confirmed that there was a difference in physical properties due to the effect of salt baking.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction content]

[0042]

As described above in detail, according to the present invention, according to the slaked lime and the manufacturing method thereof according to the present invention, limestone solid carbonaceous material industrial salt added as a fuel in the firing furnace, the furnace reduction Ambient atmosphere <br /> By firing at high temperature while maintaining the air, small lumps of reduced salt-baked quick lime are obtained, and the surface layer of this reduced salt baked quick lime is ground and removed to obtain reduced salt burned quick lime, which is then stored in a closed high-pressure digester. It is possible to obtain high-quality slaked lime by charging it into the reactor and carrying out hydrothermal hydration treatment together with the theoretical amount of deionized water. The obtained slaked lime is characterized in that it has a low bulk specific gravity and is porous, and is useful particularly in the fields of chemical reagents and food additives, etc., which require high purity in terms of chemical composition. In particular, the obtained slaked lime is a Japanese Industrial Standard (JIS) reagent special grade (K8575-19).
94) The standard value is satisfied.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C09K 17/06 H // C09K 101: 00

Claims (5)

[Claims] 1. A limestone that is naturally produced is added industrial salt and is subjected to high-temperature calcination treatment in a reduced atmosphere to obtain reduced salt-baked quicklime in the form of small pieces. The surface layer of this reduced salt-baked quicklime is ground away and then reduced salt-burnt quicklime. A slaked lime obtained by hydrothermally hydrating water with a theoretical amount of deionized water in a closed high-pressure digester. 2. A limestone is charged into a firing furnace, and industrial salt is added to the furnace to maintain a reduced atmosphere in the furnace at a high temperature for high-temperature firing to obtain reduced salt baked quicklime, and the surface layer of the reduced salt baked quicklime is removed by grinding. To obtain reduced salt burnt quicklime, and then put the obtained reduced salt burnt quicklime into a closed high-pressure digester, then inject a theoretical amount of deionized water of ion-exchanged water and perform hydrothermal hydration to obtain high quality slaked lime. A method for producing slaked lime, which comprises: 3. The fuel for burning the limestone is coal,
The method for producing slaked lime according to claim 2, wherein a solid carbonaceous material made of coke is used. 4. The method for producing slaked lime according to claim 2, wherein an alkaline salt or alkaline earth salt of sodium chloride, potassium chloride, magnesium chloride, calcium chloride or the like is used as the industrial salt. 5. The temperature rise in the closed high-pressure digester is 1
50 ℃ ~ 200 ℃, rising pressure 10 ~ 20 (Kg / cm ² ),
The method for producing slaked lime according to claim 2, 3 or 4, wherein the reaction completion time is 7 to 10 hours.