JPH10249148A - Exhaust gas treating agent and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas treating agent that removes harmful oxides in exhaust gas with high efficiency, prevent sticking and clogging to a piping, has good powder flow property at a time of being produced, has low viscosity in a slurry state at the time of treating the exhaust gas, does not generate offensive smell at a keeping and storage time, unnecessitates severe control against fire, enables easy disposal of the agent because of the high strength at a time of being solidified with cement after a treatment of the exhaust gas, and lessens the pressure drop of a bag filter after a treatment of the exhaust gas. SOLUTION: This exhaust gas treating agent consists essentially of calcium hydroxide and incorporates 0.1-10wt.% hexitol against the calcium hydroxide and has >=40m<2> /g specific surface areas, and 7-15μm average sizes. When the calcium hydroxide is mixed with water, hexitol is mixed at a ratio of 0.1-10wt.% for the calcium oxide to digest the calcium oxide, thus the exhaust gas treating agent is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas treating agent containing calcium hydroxide as a main component and a method for producing the same. More specifically, the present invention relates to an exhaust gas treating agent suitable for purifying combustion exhaust gas discharged from an incinerator, a thermal power plant, an electric furnace, and the like of municipal garbage and a method for producing the same.

[0002]

2. Description of the Related Art Calcium hydroxide (slaked lime) is produced by supplying a certain amount of calcium oxide (quick lime) and water to a digester, and mixing and stirring them in the digester to digest (hydrate) quick lime. You. The calcium hydroxide discharged from the digester is supplied to the ripening machine, where the unevenness of digestion is eliminated, the attached water is made uniform, and then the calcium hydroxide is discharged. During this time, the amount of water supplied to the digester is adjusted so that excess water evaporates and the amount of calcium hydroxide at the outlet of the ripening machine becomes almost zero. One of the main uses of calcium hydroxide is purification of combustion exhaust gas from incinerators and the like. Calcium hydroxide used for purifying the exhaust gas is desired to have good reactivity with hydrogen chloride and sulfur oxide in the exhaust gas.

Hitherto, a method for producing calcium hydroxide and an exhaust gas treating agent for such a use have been proposed (for example, Japanese Patent Publication No. 6-8194, Japanese Patent Application Laid-Open No. H8-10804).
0, JP-A-9-103640). The invention described in Japanese Patent Publication No. 6-8194 discloses a method in which calcium oxide and a slaking liquid composed of 30 to 50 parts by volume of water and 50 to 70 parts by volume of an organic solvent such as lower alcohol, ketone, ether and aldehyde are fixed. Mix at a temperature below 45 ° C. in a ratio, then transfer the reaction mixture to the main reaction vessel and react at a temperature of 50-70 ° C., and place the final reaction in a second reaction vessel at 85-110 ° C.
This is a method for producing dried calcium hydroxide by performing the above process. The invention described in JP-A-8-108040 discloses an exhaust gas comprising calcium hydroxide having a specific surface area of 25 m ² / g or more, an average particle diameter of 6 μm or less, and a reaction activity of oxalic acid activity of 30 minutes or less. It is a processing agent. Furthermore, the invention described in JP-A-9-103640 is an exhaust gas treating agent containing calcium hydroxide containing 0.05 to 1.0% by weight of calcium hydroxide of a lower alcohol such as ethanol or methanol and having calcium hydroxide as an active component. . According to the calcium hydroxide or the exhaust gas treating agent described in the above publication, any of them can remove harmful oxides and the like in the exhaust gas with high efficiency. Calcium hydroxide or exhaust gas treatment agent that has purified the combustion exhaust gas generated in garbage incinerators, etc., becomes fly ash after processing, is captured by a bag filter, etc., is solidified with cement, and is often disposed of in landfill. ing.

[0004] In particular, Japanese Patent Publication No. 6-8194 and Japanese Patent Application Laid-Open
According to the invention described in JP-A-103640, an organic solvent such as a lower alcohol is contained to delay the digestion rate of calcium oxide, thereby producing a calcium hydroxide having a higher specific surface area and a higher reactivity, and improving the exhaust gas treatment effect. Is increasing. The invention described in Japanese Patent Application Laid-Open No. 9-103640 prevents the clogging and blockage of the pipe during supply and discharge of calcium hydroxide by making the content of the lower alcohol different from the invention described in Japanese Patent Publication No. 6-8194. It has the feature of suppressing aggregation and consolidation during storage.

[0005]

[Problems to be solved by the invention]
The inventions described in JP-A No. 194 and JP-A-9-103640 have the following problems due to containing a lower alcohol. When a lower alcohol contained in calcium hydroxide is left in a high temperature state for a long time, it may be transformed into an aldehyde to generate an unpleasant odor. After the exhaust gas treatment, the used calcium hydroxide when solidified with cement has a relatively low solidification strength, so that it is easily scattered and difficult to dispose. Since water and lower alcohol are mixed and digested, in the case of degassing by evaporation, a high-cost lower alcohol recovery and reuse device is required. Lower alcohols have high volatility and require careful handling of fire during storage.

In the inventions described in JP-A-8-108040 and JP-A-9-103640, calcium hydroxide is an extremely fine particle having an average particle diameter of 6 μm or less. However, when the exhaust gas is treated, the filter cloth of the bag filter is clogged and the pressure loss of the bag filter is increased. Furthermore, the exhaust gas treating agent may be used in the form of a slurry and sprayed into the exhaust gas, but the slurry of the exhaust gas treating agent made of calcium oxide and digested water or digested alcohol aqueous solution has a relatively high viscosity, There was a drawback that the piping of the processing device was blocked.

A first object of the present invention is to provide an exhaust gas treating agent for removing harmful oxides and the like in exhaust gas with high efficiency and a method for producing the same. A second object of the present invention is to provide an exhaust gas treating agent that has good fluidity when it is turned into a powder product, has a low viscosity in a slurry state during exhaust gas treatment, and does not cause adhesion or blockage to pipes, respectively. It is to provide a manufacturing method thereof. A third object of the present invention is to provide an exhaust gas treating agent which does not generate an unpleasant odor during storage and storage, does not require strict control over fire, has high strength when cement solidified after exhaust gas treatment and is easy to dispose, and its production. It is to provide a method. A fourth object of the present invention is to provide an exhaust gas treating agent having a small pressure loss of a bag filter after exhaust gas treatment, and a method for producing the same.

[0008]

The invention according to claim 1 is
It contains calcium hydroxide as a main component, contains 0.1 to 10% by weight of hexite based on the calcium hydroxide, has a specific surface area of 40 m ² / g or more, and has an average particle size of 7 to 15%.
It is an exhaust gas treating agent having a size of μm. The specific surface area is 40m ² /
g, it has high reactivity and removes harmful oxides and the like in exhaust gas with high efficiency. The average particle size is 7 to 15μ.
m, which are not very fine particles, so that the exhaust gas treating agent does not easily aggregate and does not clog the filter cloth of the bag filter after exhaust gas treatment.

The invention according to claim 2 is the invention according to claim 1, wherein one or more powders selected from the group consisting of inorganic minerals, activated carbons, and lightweight lightweight concrete concrete are hydroxylated. An exhaust gas treating agent uniformly mixed with 1 to 50% by weight of calcium. Average particle size is 7 to 15 μm
By uniformly mixing powder consisting of inorganic minerals, activated carbons, and lightweight aerated concrete waste material with calcium hydroxide, the fluidity of the exhaust gas treating agent is further improved, and adhesion and clogging of pipes are further prevented.

The invention according to claim 3 is a method for producing calcium hydroxide by mixing calcium oxide and water and digesting the calcium oxide, wherein the hexit is 0.1 to 10% by weight based on the calcium oxide. % Of the mixture is mixed with calcium oxide at a ratio of 0.1%. When Hexit is mixed with calcium oxide, the generated calcium hydroxide is finely divided to have a large specific surface area and high reactivity. The reason for this is not always clear, but the addition of hexite alleviates the rapid hydration of quicklime, and the quicklime particles gradually react with water from the particle surface during hydration, and fine slaked lime particles from the surface of the quicklime particles. It is presumed that this is due to the generation of flakes. Furthermore, unlike lower alcohols, hexit has the effect of delaying the digestion reaction with very small amounts of calcium oxide. The reason for this is not necessarily clear, but is presumed as follows. Addition of hexite forms fine primary particles and the concentration in the digestion aqueous solution is low, so that secondary particles are promoted and the like, and agglomerates of slaked lime rich in voids are formed. The agglomerates have a large specific surface area despite their large particle size, are highly reactive, and lower the viscosity of the slurry. In addition, the fine porosity is high due to the aggregate of the fine particles, so that the cement solidification strength is not reduced.

The invention according to claim 4 is the invention according to claim 3, which is a manufacturing method in which the atmosphere during digestion is reduced. By reducing the atmosphere during digestion, the boiling point of water can be lowered and the digestion reaction temperature can be lowered. As described above, the boiling point of water at the time of the digestion reaction decreases, and the maximum point of the digestion reaction temperature decreases, whereby the specific surface area of calcium hydroxide increases. The invention according to claim 5 is the invention according to claim 3 or 4, wherein the water for digestion is divided into two portions and mixed with calcium oxide. This is a production method in which an alkali hydroxide is added to water to be added a second time. By adding an alkali hydroxide to the digestion water attached for the second time, the atomization of calcium hydroxide crystals is promoted, and the specific surface area of calcium hydroxide increases. In this case as well, only the first time or 1
The atmosphere may be decompressed both in the second time and the second time.

The invention according to claim 6 is the invention according to claims 3 to 5
The invention according to any one of the above, wherein the amount of water for digestion is 2 to 5 times the digestion equivalent of calcium oxide, and the calcium hydroxide containing generated water is dried.
Such excessive mixing of water lowers the temperature during digestion and slows the digestion rate. The resulting calcium hydroxide is less likely to come into contact with air in a highly active state, preventing the absorption of carbon dioxide and moisture in the air,
Calcium hydroxide having a high specific surface area can be obtained.

The invention according to claim 7 is the invention according to claims 3 to 6
An organic solvent having a higher boiling point than water is added to the aqueous hexit solution in an amount of 5 to 40 to the hexite.
This is a production method in which the additive is added at a ratio of% by weight. By further including an organic solvent having a boiling point higher than that of water, the adhesion between particles is reduced and electrification is also prevented. As a result, the fluidity of the exhaust gas treating agent is further improved, and the adhesion and clogging of pipes are reduced. Prevent further.

The invention according to claim 8 is the invention according to claims 3 to 7
The invention according to any one of the above, wherein the calcium hydroxide produced by digestion has an average particle diameter of one or more selected from the group consisting of inorganic minerals, activated carbon, and lightweight aerated concrete waste material of 7 to This is a production method in which 15 μm powder is added and mixed. By uniformly mixing powder composed of inorganic minerals having an average particle diameter of 7 to 15 μm, activated carbons, and lightweight lightweight concrete concrete with calcium hydroxide, the flowability of the exhaust gas treating agent is further improved, Blockage is further prevented.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material calcium oxide (quick lime) used in the present invention is preferably as active as it is higher and finer in particle size. It is preferably 5 mm or less, particularly preferably 150 μm or less. As the activity, the activity by the 50 g method defined in Examples described later is 250 (m
1/5 minutes) or more.

According to the first and third aspects of the present invention, when digesting calcium oxide as a raw material with water, hexit is added. Hexit is a kind of sugar alcohol, and is a general term for hexahydric alcohol obtained by reduction of hexose, CH
_It has the structure of ₂ OH (CHOH) ₄ CH ₂ OH. Hexit used in the present invention includes D-sorbit, D-mannit, D-inject, D-talit, dullcit, and alit. Especially D- which exists in the natural world
Sorbit, D-mannit, D-inject, and dursit are preferred. Hexit has the effect of slowing the rate of reaction between quicklime and digestive water. It is presumed that the addition of hexite causes the lime particles to gradually react with water from the particle surface when hydrated, and to generate fine calcium hydroxide particles, thereby increasing the specific surface area of calcium hydroxide. Hexit is 0.1 to calcium oxide
It is mixed with calcium hydroxide in a proportion of 10% by weight. Preferably 0.3-3% by weight, most preferably 0.5-2%
% By weight. If the added amount is less than 0.1% by weight, the improvement of the reactivity is insufficient, and if it exceeds 10% by weight, the cost increases. It is preferable that the hexit is mixed by adding a hexit soluble in water to digested water to form a hexit aqueous solution, and then mixing and stirring the hexit aqueous solution and quicklime. Alternatively, quicklime, digested water and hexit may be separately mixed. The mixing and stirring device may be a mixing vessel equipped with a stirrer or a continuous line mixer.

In the invention according to claim 4, the atmosphere during digestion is reduced in pressure. Atmospheric pressure at this time is preferably at least 0.6 atm. In the invention according to claim 5, an alkali hydroxide is added to the water to be added for the second time. Examples of the alkali hydroxide include sodium hydroxide, potassium hydroxide, and lithium hydroxide. This alkali hydroxide is preferably added in an amount of 0.05 to 3% by weight based on calcium oxide. In the invention according to claim 6, the amount of water for digestion is 2 to 5 times the digestive equivalent of calcium oxide. This amount of water is preferably 2.5 to 5 times. Further, the water content in the generated calcium hydroxide is 3 to 30% by weight, preferably 5 to 2%.
It is preferable to determine the amount of digested water so as to be 0% by weight. If the amount of digested water is less than twice the theoretical amount of digested water or the generated calcium hydroxide has a water content of less than 3% by weight, the specific surface area becomes small, and the improvement of reactivity becomes insufficient. When the amount of digested water exceeds 5 times the theoretical amount of digested water and the water content of the generated calcium hydroxide exceeds 30% by weight, the calcium hydroxide becomes a paste or slurry, and a separate dehydrator is required. In addition, in addition to adding 2 to 5 times the theoretical amount of water to lower the temperature during digestion, the digestive atmosphere temperature may be forcibly reduced. The temperature during digestion is 100 ° C or lower, preferably 80 ° C or lower.

In the invention according to claim 7, an organic solvent having a boiling point higher than that of water is added to the aqueous hexit solution in an amount of 5 to hexit.
１００100% by weight. Examples of the organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin and the like. This addition amount is preferably 10 to 80
%, More preferably 20 to 60% by weight. If the amount is less than 5% by weight, the effect of addition is poor, and if it exceeds 100% by weight, a large amount of extremely fine calcium hydroxide powder is generated.
It becomes difficult to manufacture the 15 μm, and the cost is further increased. In the invention according to claims 2 and 8, one selected from the group consisting of inorganic minerals, activated carbons and lightweight aerated concrete wastes.
Seed or two or more powders with respect to calcium hydroxide
Mix 50% by weight uniformly. Inorganic minerals include zeolite, activated clay, perlite, clay, and the like. Activated carbons include activated carbon, thinned wood, construction waste, rice hulls, and the like.

Calcium hydroxide (slaked lime) containing water generated by the digestion reaction is introduced into a ripening machine, and is aged by being stirred by stirring blades. The aged slaked lime is introduced into a dryer, stirred by a stirring blade, and dried. Thereafter, the powder is classified to a predetermined particle size or less by a classifier, and the coarse powder is pulverized by a pulverizer to obtain a product. It is also possible to omit the aging machine and supply slaked lime directly from the digester to the dryer. Examples of the dryer include a paddle dryer, a belt dryer, a band dryer, a rotary dryer, a fluid dryer, a flash dryer, an electromagnetic wave dryer, and an infrared (far infrared) dryer. Preferably, an indirect heating type is used in order to avoid contact with carbon dioxide gas as much as possible and to prevent calcium hydroxide from being carbonated into calcium carbonate.

According to the above method, calcium hydroxide having a specific surface area of 40 m ² / g or more and an average particle size of 15 μm or less can be obtained. In the present invention, this calcium hydroxide is sieved, and calcium hydroxide having an average particle diameter of 7 μm or more is used as an exhaust gas treating agent. This is because calcium hydroxide having an extremely fine particle size causes clogging of the filter cloth of the bag filter after exhaust gas treatment. Further, calcium hydroxide having an average particle size of 7 to 15 μm is finely divided, so that the whiteness is 90 or more, the appearance is good, and the product value is enhanced. In addition, the angle of repose is as small as 50 degrees or less, and the fluidity is excellent. Therefore, this exhaust gas treatment agent adheres little to pipes and hoppers,
Extraction from the hopper is easy.

[0021]

EXAMPLES Next, examples of the present invention will be described together with comparative examples in order to show specific embodiments of the present invention. In the following Examples and Comparative Examples, as a raw material calcium oxide, a particle size of 150 was used.
Quicklime powder having an activity of 310 μm or less (ml / 5 min) was used. This activity refers to a 3 liter beaker with 2 water
Liter (40 ° C.) and stir, then 50 g of quicklime
(Particle size: 10 to 3 mm), and at the same time, 2 to 3 drops of phenolphthalein as an indicator are dropped. 4N-HCl is continuously added dropwise for 5 minutes so that the solution remains slightly red. The hydrochloric acid consumption at this time is defined as activity. The higher the consumption of hydrochloric acid, the higher the activity.

<Embodiment 1> 30 g of D-sorbit was added to 20 g
The solution was dissolved in 9.6 kg of water at ℃, and 10 kg of quicklime was digested using this sorbite aqueous solution. Therefore, the addition amount of sorbite is 0.3% by weight based on quicklime. Also,
The amount of digested water is three times the theoretical amount. The atmospheric pressure during digestion was 1 atm (atmospheric pressure), and the atmospheric temperature was 10 ° C. 1
The water content (before drying) after the time aging was 18.6%. This was dried to produce an exhaust gas treating agent containing calcium hydroxide as a main component. The water content after drying was 0.2%. <Example 2> The amount of D-sorbitol added was 0.5% by weight, the amount of digested water was 2.5 times the theoretical value, the moisture after aging for 1 hour (before drying) was 10.2%, and the moisture after drying was 0%. An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the amount was 0.1%.

<Embodiment 3> The amount of D-sorbitol added was set to 0.
Except that the content was 5% by weight, an exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1. <Example 4> The amount of D-sorbitol added was 0.5% by weight, the amount of digested water was 5 times the theoretical value, and the moisture after aging for 1 hour (before drying)
Was 48.7% and the moisture after drying was 0.5%, to produce an exhaust gas treating agent containing calcium hydroxide as a main component in the same manner as in Example 1. <Example 5> The amount of D-sorbitol added was 0.5% by weight, the amount of digested water was 7 times the theoretical value, and the water content after aging for 1 hour (before drying)
And an exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the water content after drying was changed to 104.3% and the water content after drying was changed to 8.6%.

<Embodiment 6> The amount of D-sorbitol added was set to 1.
0% by weight, moisture after 1 hour aging (before drying) 18.1%
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the above conditions were used. <Example 7> The amount of D-sorbitol added was 2.0% by weight,
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the moisture after aging (before drying) was changed to 18.8%. Example 8 The amount of D-sorbitol added was 6.0% by weight,
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the moisture after aging (before drying) was changed to 18.8%.

<Embodiment 9> The amount of D-sorbit added was 1
28. Water content (before drying) after aging for 1 hour at 0.0% by weight.
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the water content after drying was 9% and the moisture content after drying was 0.3%. <Example 10> The amount of D-sorbitol added was 0.5% by weight,
Manufacture of an exhaust gas treating agent containing calcium hydroxide as a main component in the same manner as in Example 1 except that the atmospheric pressure during digestion was changed to 0.6 atm and the moisture after aging for 1 hour (before drying) was changed to 15.9%. did. <Example 11> The amount of D-sorbitol added was 0.5% by weight,
Manufacture of an exhaust gas treating agent containing calcium hydroxide as a main component in the same manner as in Example 1 except that the atmospheric pressure during digestion was set to 0.8 atm and the moisture after aging for 1 hour (before drying) was set to 17.1%. did.

Example 12 Digested water was added in two portions. Twice the theoretical amount was added the first time, and the same amount as the theoretical amount was added the second time. An exhaust gas treating agent containing calcium hydroxide as a main component was prepared in the same manner as in Example 1 except that the amount of D-sorbitol added was 0.5% by weight and the moisture after aging for 1 hour (before drying) was 18.1%. Manufactured. Example 13 Digestion water was added in two portions. The first time, the same amount as the theoretical amount was added, and the second time, twice the theoretical amount was added. An aqueous NaOH solution was added to the second digestion water. Na
The OH content was 0.1% by weight based on quicklime. An exhaust gas treating agent containing calcium hydroxide as a main component was prepared in the same manner as in Example 1 except that the amount of D-sorbitol added was 0.5% by weight and the moisture after aging for 1 hour (before drying) was 19.6%. Manufactured.

Example 14 Digested water was added in two portions. Twice the theoretical amount was added the first time, and the same amount as the theoretical amount was added the second time. An aqueous NaOH solution was added to the second digestion water. The amount of NaOH was 0.1% by weight based on quicklime. An exhaust gas treating agent containing calcium hydroxide as a main component was prepared in the same manner as in Example 1 except that the amount of D-sorbitol added was 0.5% by weight, and the moisture after aging for 1 hour (before drying) was 22.8%. Manufactured. Example 15 Digested water was added in two portions. The first time, 2.5 times the theoretical amount was added, and the second time, 0.5 times the theoretical amount.
One-fold was added. An aqueous NaOH solution was added to the second digestion water. The amount of NaOH was 0.1% by weight based on quicklime. Example 1 except that the amount of D-sorbitol added was 0.5% by weight and the moisture after aging for 1 hour (before drying) was 31.6%.
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as described above.

Example 16 Digested water was added in two portions. Twice the theoretical amount was added the first time, and the same amount as the theoretical amount was added the second time. An aqueous NaOH solution was added to the second digestion water. The amount of NaOH was 0.1% by weight based on quicklime. Water was prepared in the same manner as in Example 1 except that the amount of D-sorbitol added was 0.5% by weight, the atmospheric pressure during digestion was 0.6 atm, and the moisture after aging (before drying) was 21.8%. An exhaust gas treating agent containing calcium oxide as a main component was manufactured. <Example 17> Digested water was added in two portions. Twice the theoretical amount was added the first time, and the same amount as the theoretical amount was added the second time. An aqueous NaOH solution was added to the second digestion water. Na
The OH content was 0.1% by weight based on quicklime. The amount of D-sorbitol added was 0.5% by weight, the atmospheric pressure during digestion was 0.8 atm, and the moisture after aging for 1 hour (before drying) was 22.8.
%, And an exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the water content after drying was changed to 0.3%.

Comparative Example 1 No hexit was added to digested water. The digested water amount is twice the theoretical value, the moisture after aging for 1 hour (before drying) is 0.1%, and the moisture after drying is 0.1%
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the above conditions were used. <Comparative Example 2> No hexit was added to digested water. An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the moisture after aging for 1 hour (before drying) was 13.5% and the moisture after drying was 0.1%. . Comparative Example 3 No hexit was added to digested water. Calcium hydroxide was mainly used in the same manner as in Example 1 except that the digested water amount was 5 times the theoretical value, the moisture after aging for 1 hour (before drying) was 30.7%, and the moisture after drying was 0.3%. An exhaust gas treating agent as a component was produced.

Comparative Example 4 No hexit was added to digested water. The digested water amount is 7 times the theoretical value, the moisture after aging for 1 hour (before drying) is 85.3%, and the moisture after drying is 5.6%.
%, An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1. <Comparative Example 5> No hexit was added to digested water. The atmospheric pressure during digestion is 0.6 atm, the moisture after aging for 1 hour (before drying) is 12.7%, and the moisture after drying is 0.1%
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the above conditions were used. <Comparative Example 6> No hexit was added to digested water. Digestion water was added in two portions. Twice the theoretical amount was added the first time, and the same amount as the theoretical amount was added the second time.
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the moisture after aging for 1 hour (before drying) was 12.8% and the moisture after drying was 0.1%. .

<Comparative Test 1> The exhaust gas treating agents obtained in Examples 1 to 17 and Comparative Examples 1 to 6 were measured for whiteness, angle of repose, specific surface area, CAA, average particle diameter and pressure loss. Table 1 shows the results. The whiteness was measured using Tokyo Denshoku Color Ace. Whiteness means that the larger the numerical value is, the whiter it is. The angle of repose was measured using a Hosokawa Micron powder tester. The angle of repose shows a small value in a powder having good fluidity. The angle of repose of a fine powder having strong adhesion and cohesion tends to be large, and the fluidity tends to be poor. The specific surface area was measured using a specific surface measuring device (manufactured by Yuasa Ionics). The larger the specific surface area, the finer the particle size. CAA is an abbreviation for citric acid activity. This CAA is charged with 3.705 g of calcium hydroxide while stirring 100 ml of a 0.4N citric acid solution (30 ° C.), and the time until the liquid changes from a faint red to a deep red using phenolphthalein as an indicator ( Second). The smaller the CAA value, the higher the reactivity. Further, the pressure loss was measured using a filter cloth for bag filter made of polyester felt, and an exhaust gas treating agent was added to the filter cloth at a dust-containing concentration of 10 g / Nm ³ at 2 m ³ / cm 2.
The test was carried out by adjusting the blower so that the air flow per minute was obtained, and it was determined from the difference between the pressure at the inlet of the bag filter and the pressure at the outlet at the time of the steady state.

[0032]

[Table 1]

As is clear from Table 1, the exhaust gas treating agents obtained in Examples 1 to 17 had high whiteness, small angle of repose, excellent fluidity, large specific surface area, and high reactivity ( CAA value was low). On the other hand, in the exhaust gas treating agents obtained in Comparative Examples 1 to 6 in which hexit was not added to digested water, the whiteness was low, the angle of repose was large, and
The specific surface area was small and the reactivity was low (the value of CAA was high). When the amount of digested water is twice the theoretical amount,
When the specific surface area is rather small, and the digested water volume is 6 times or more, calcium hydroxide becomes a paste or slurry,
Since a separate dehydrator is required, the digested water volume is 2.5 to
It has been found that it is preferable to make it five times. In addition, when adding the digestion water in two portions, Examples 13 to 15 confirmed that it is better to increase the amount of water in the first time than in the second time.

It was found from the comparison of Examples 12 to 17 that the specific surface area was increased and the reactivity was increased by adding NaOH to the digestion water for the second time. The comparison between Examples 3, 10, and 11 and Examples 14, 16, and 17 shows that the specific surface area and the reactivity are increased by reducing the pressure during digestion. The maximum temperature during digestion was measured as follows, and it was found that the maximum temperature was reduced by reducing the pressure.

Example 3 (1 atm) 99 ° C. Example 10 (0.6 atm) 71 ° C. Example 11 (0.8 atm) 82 ° C. Digestion water is divided into two parts and NaOH is added to the second digestion water. It was found from the comparison of Examples 12, 14, 14, 16 and 17 that the specific surface area and the reactivity were further improved by adding and reducing the atmosphere at this time.

Further, the average particle size increases when hexite is added, and decreases only when hexite or water is excessively added. On the other hand, it was found that the average particle diameter of the exhaust gas treating agents obtained in Comparative Examples 1 to 6 in which hexit was not added became smaller and became particularly smaller as the amount of digested water increased. Similarly, the pressure loss decreases when hexite is added and increases only when hexite or water is excessively added. On the other hand, Comparative Examples 1 to 6 without addition of hexite
It has been found that the pressure loss of the exhaust gas treating agent obtained in (1) becomes large and becomes particularly large as the amount of digested water increases.

Example 18 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the amount of D-sorbitol was changed to 0.5% by weight. <Example 19> An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the amount of D-mannitol added was 0.5% by weight. <Example 20> An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the added amount of dursit was 0.5% by weight.

Example 21 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the amount of D-sorbite was changed to 1.0% by weight. <Example 22> An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the amount of D-mannitol was changed to 1.0% by weight. Example 23 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that the added amount of dursit was 1.0% by weight.

Example 24 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1, except that 1.0% by weight of D-sorbitol and 0.1% by weight of diethylene glycol were added. . <Example 25> Example 1 except that 1.0% by weight of D-sorbitol and 0.3% by weight of diethylene glycol were added.
An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as described above. Example 26 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that 1.0% by weight of D-sorbitol and 0.1% by weight of glycerin were added.

Example 27 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that 1.0% by weight of D-sorbitol and 0.3% by weight of glycerin were added. . Example 28 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that 1.0% by weight of D-sorbite and 2% by weight of zeolite were added. Example 29 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that 1.0% by weight of D-sorbite and 4% by weight of zeolite were added.

Example 30 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that 1.0% by weight of D-sorbite and 2% by weight of activated clay were added. <Example 31> An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that 1.0% by weight of D-sorbite and 4% by weight of activated clay were added.

Comparative Example 7 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that no hexite was added to digested water. Comparative Example 8 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that 30% by weight of ethanol was added. Comparative Example 9 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that ethanol was added at 40% by weight.

Comparative Example 10 An exhaust gas treating agent containing calcium hydroxide as a main component was produced in the same manner as in Example 1 except that 50% by weight of ethanol was added.

<Comparative Test 2> The exhaust gas treating agents obtained in Examples 18 to 31 and Comparative Examples 7 to 9 were tested for the average particle size,
The whiteness, angle of repose, specific surface area, slurry viscosity, cement solidification strength and pressure loss were measured. Table 2 shows the results. The average particle size, whiteness, angle of repose, specific surface area, and pressure loss were measured in the same manner as in Comparative Test 1 described above. The slurry viscosity was obtained by mixing the obtained exhaust gas treating agent with water to prepare a slurry having a concentration of 30%, and measuring the viscosity of the slurry with a B-type viscometer. The smaller the value, the lower the viscosity. The cement solidification strength was determined by treating the exhaust gas using the obtained exhaust gas treating agent and treating the obtained fly ash, cement and water in a ratio of 14: 1 to 11: 1.
The mixture was poured into a cylinder and solidified to form a cylindrical test piece having a diameter of 5 cm and a height of 10 cm, and cured in a room at 20 ° C. for 10 days. It was measured by performing a compression test with a compressor at a place.

[0045]

[Table 2]

As is clear from Table 2, Examples 18 to 31
The exhaust gas treating agent obtained in (1) had high whiteness, a large specific surface area, and low slurry viscosity and low pressure loss.
On the other hand, Comparative Examples 7 to 7 in which hexit was not added to digested water
The exhaust gas treating agents obtained in 9 all have low whiteness,
The specific surface area was small and the slurry viscosity was high. Comparative Example 8
The exhaust gas treating agent to which ethanol was added was approximately the same in angle of repose as in Examples 18 to 31, and was excellent in fluidity together with Examples. On the other hand, the cement solidification strength was remarkably inferior to those of Examples 18 to 31.

Further, the exhaust gas treating agents obtained in Examples 18 to 31 had a large average particle diameter, and Comparative Examples 7 to 10 were all small. In particular, it was found that the larger the amount of the exhaust gas treating agent to which ethanol was added, the smaller the amount.

<Comparison between average particle size and pressure loss> In order to clarify the relationship between the average particle size and the pressure loss, the above Examples 1 to
31 and those having different average particle sizes are selected from Comparative Examples 1 to 10, and the corresponding pressure loss is shown in Table 3 and FIG.

[0049]

[Table 3]

As is clear from Table 3 and FIG. 1, Examples 10, 28, 30, and 31 having an average particle diameter of 7 to 20 μm are Comparative Examples 10, 9, 8, 4, and 1 having an average particle diameter of 6 μm or less. It was found that the pressure loss was relatively small as compared with.

[0051]

As described above, according to the exhaust gas treating agent of the present invention, the specific surface area is remarkably large and the reactivity is high, and harmful oxides and the like in the exhaust gas can be removed with high efficiency. The higher the degree, the better the appearance of the product and its value. In addition, since the fluidity of the powdered product is good and the viscosity of the slurry during exhaust gas treatment is low, it does not adhere to the pipes or blockage.
In addition, because it does not contain lower alcohols that are converted to aldehydes during high-temperature storage, it does not generate off-flavors during storage and storage, does not require explosion-proof equipment, does not require strict control over fire, and has solidified cement after exhaust gas treatment. There is an advantage that the strength at the time is high and it is easy to dispose. Further, clogging of the filter cloth of the bag filter after the exhaust gas treatment hardly occurs, and the pressure loss can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an average particle diameter and a pressure loss according to an example and a comparative example.

[Procedure amendment]

[Submission date] December 5, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0045

[Correction method] Change

[Correction contents]

[0045]

[Table 2]

Claims (8)

[Claims] 1. A composition comprising calcium hydroxide as a main component, 0.1 to 10% by weight of hexite based on calcium hydroxide, a specific surface area of 40 m ² / g or more, and an average particle size of 7 to 15 μm. An exhaust gas treating agent. 2. The method of claim 1, wherein one or more powders selected from the group consisting of inorganic minerals, activated carbons and lightweight lightweight concrete concrete are uniformly mixed in an amount of 1 to 50% by weight with respect to calcium hydroxide. The exhaust gas treating agent according to the above. 3. A method for producing calcium hydroxide by mixing calcium oxide and water to digest the calcium oxide, wherein hexit is added in a ratio of 0.1 to 10% by weight based on the calcium oxide. A method for producing an exhaust gas treating agent comprising mixing with an oxide of calcium. 4. The method according to claim 3, wherein the atmosphere during digestion is reduced in pressure. 5. The method according to claim 1, wherein the water for digestion is divided into two portions and mixed with calcium oxide, hexit is added to the first mixed water, and alkali hydroxide is added to the second added water. 5. The production method according to 3 or 4. 6. The method according to claim 3, wherein the amount of water for digestion is 2 to 5 times the digestion equivalent of calcium oxide, and the produced calcium hydroxide containing water is dried. 7. The method according to claim 3, wherein an organic solvent having a higher boiling point than water is added to the aqueous solution of Hexit at a ratio of 5 to 100% by weight based on Hexit. 8. A method according to claim 3, wherein one or more powders selected from the group consisting of inorganic minerals, activated carbons and lightweight lightweight concrete concrete are added to the calcium hydroxide produced by digestion and mixed. The production method according to any of the above.