JP2000218128A - Acid component removing agent, its production, and acid component removing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove acid components such as hydrogen chloride, sulfur oxides, and nitrogen oxides efficiently from exhaust gas and to reduce the amount of waste by facilitating disposal treatment by incorporating sodium hydrogen carbonate whose average particle size based on volume measured by a laser diffraction scattering method is specified. SOLUTION: In an acid component removing agent, the average particle size based on volume of sodium hydrogen carbonate is measured by a laser diffraction scattering particle size distribution measuring device. The average particle size of sodium hydrogen carbonate is set up at 1-9 μm. In sodium hydrogen carbonate, in the pore distribution of a powder layer by a mercury pressure injection method, a pore volume in which pore diameters are 1-10 μm is set up at 0.4 cm3 or above. Moreover, in sodium hydrogen carbonate, sodium carbonate obtained when baked at 200 deg.C for one hr preferably exhibits powder properties similar to those of sodium hydrogen carbonate. In this way, acid components in exhaust gas are removed efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an agent for removing an acidic component in a gas, a method for producing the same, and a method for removing an acidic component from a gas.

[0002]

2. Description of the Related Art It is known to use slaked lime as an acidic component remover in order to absorb and remove hydrogen chloride and sulfur oxides from exhaust gas discharged from a waste incinerator or the like. In this case, slaked lime is dispersed in a temperature range of 150 to 300 ° C., particularly 150 to 200 ° C. in an exhaust gas discharge path from an incinerator or the like, and collected by a bag filter or an electric dust collector to form a filtration layer to form an acidic layer. The components have been removed.

However, slaked lime is 3 to 4 parts per equivalent.
There is a drawback that the amount of dust to be discarded increases because it is necessary to use double equivalents and excessive use. In addition, since these dusts are solidified using concrete, they are putting pressure on the landfill site for landfills. Since the reaction product of hydrogen chloride and slaked lime is calcium chloride and water-soluble, it can be dissolved and removed in water.However, part of slaked lime that is added excessively becomes quicklime but is insoluble in water. Dust reduction effect by water is small. Furthermore, at the final disposal site, calcium scale is generated during the treatment of leachate containing calcium chloride, causing trouble.

It is known to use sodium hydrogen carbonate as an acidic component remover instead of slaked lime. In this case, unreacted sodium bicarbonate becomes sodium carbonate, and is effective in reducing dust due to water solubility. For example, Japanese Patent Application Laid-Open No. Hei 9-507654 discloses that sodium hydrogen carbonate exceeds 98% by mass and sodium carbonate 2% by mass.
An acidic component remover consisting of a composition containing less than is described. It is described that the average particle size of this composition is 50 μm or less, preferably 10 to 30 μm.

However, since sodium bicarbonate is more expensive than slaked lime, it is desired to supply inexpensive and industrial scale sodium bicarbonate which has a high reaction rate and can be obtained in a small amount. In addition, a pulverizer is not required during use, so it can be used immediately, is easy and stable to be injected into the gas to be treated, disperses well in the gas, has a high reaction rate, and has a storage tank at the place of use. And long-term storage in warehouses are desirable.

[0006]

In general, slaked lime is used as an acidic component remover in a garbage incineration plant or the like. Although slaked lime is inexpensive, it has problems in waste treatment, such as an increase in water-insoluble dust to be discarded as described above, and a problem of trouble due to generation of calcium scale in leachate at a final disposal site. In addition, since sodium bicarbonate is expensive when used, it is necessary to increase the reaction efficiency and reduce the amount used. Further, if the amount of use can be reduced, the size of the accompanying equipment can be reduced, and the dust to be treated can be reduced.

Accordingly, the present invention is to provide an acidic component remover which can efficiently remove acidic components such as hydrogen chloride, sulfur oxides, nitrogen oxides, etc. from exhaust gas, can easily dispose, and reduce the amount of waste. The purpose is to provide.

[0008]

According to the present invention, a volume-based average particle diameter measured by a laser diffraction scattering method is 1 to 9 μm.
The present invention provides an acidic component remover containing sodium hydrogen carbonate and a method for producing the same.

In the acidic component-removing agent of the present invention, the average particle size of sodium bicarbonate refers to the numerical value of the average particle size on a volume basis measured using a laser diffraction / scattering type particle size distribution analyzer. . Hereinafter, when simply referred to as the average particle size, it refers to the value measured by this method. In addition,
In the present specification, the average particle size is manufactured by Nikkiso Co., Ltd., trade name:
It was measured using a Microtrac FRA9220.

The acidic component removing agent of the present invention reacts with an acidic component present in a gas to remove the acidic component from the gas. The acidic component to be removed is not particularly limited, and can be applied to various acidic components such as hydrogen chloride, sulfur dioxide, sulfur trioxide, and nitrogen oxide. In particular, when the acidic component-removing agent of the present invention is applied to a compound containing chlorine such as hydrogen chloride, the reaction efficiency is higher than before and the use is easy. Hereinafter, hydrogen chloride will be described, but the same applies to other acidic components.

When sodium bicarbonate is used, when sodium bicarbonate particles are converted into sodium carbonate by firing, the particles become porous and react efficiently with hydrogen chloride, so that hydrogen chloride can be removed efficiently. The present inventors measured and observed the particle diameter, pore distribution, and shape of sodium hydrogen carbonate and sodium carbonate before and after calcination in detail, and found that the reaction between the pore structure obtained by making the pores porous and hydrogen chloride. The inventors have found that the characteristics are sensitively affected by the average particle size of sodium hydrogen carbonate, and have reached the present invention.

In the acidic component-removing agent of the present invention, the average particle size of sodium hydrogen carbonate is in the range of 1 to 9 μm.
When the average particle size of sodium bicarbonate exceeds 9 μm,
When sodium bicarbonate is calcined into sodium carbonate, sponge-like sodium carbonate particles having fine holes with a diameter of several tens nm or less are obtained while maintaining the contour of the outer surface of sodium bicarbonate. On the other hand, when the average particle size of sodium bicarbonate is 9 μm or less, pores having a relatively large diameter with respect to the particle size are formed. Become.

The gist of the present invention is that when sodium bicarbonate having an average particle size of 9 μm or less is calcined to form sodium carbonate, the above-mentioned special pore structure is obtained, and the pore structure is formed of an acidic gas. It is very effective for absorption. In the prior art, although the absorption of acidic gas by sodium hydrogen carbonate having a large particle size is exemplified, the average particle size is 9 μm.
The following sodium hydrogen carbonate is not used, and it is not known that the fine particle size of sodium hydrogen carbonate changes the pore structure and the particle shape of sodium carbonate after firing.

The present inventors have found that when particles are scattered in an air stream, or when a gas of an acidic component such as hydrogen chloride flows through the particle gap when the particles are trapped by a bag filter to form a particle deposition layer. It is presumed that the above-mentioned shape facilitates diffusion and reaction of the acidic component to the particle surface, and promotes a favorable reaction with the acidic component. Sodium bicarbonate
It is more preferable that the average particle size is 8 μm or less.

The lower limit of the average particle size of sodium hydrogen carbonate is as follows:
Although not particularly limited in terms of the reaction with the acidic component, when the average particle size is less than 1 μm, there is a strong tendency to adhere to each other, and sufficient fluidity cannot be maintained even when an anti-adhesion agent described below is used in combination. Or a large amount of an anti-sticking agent needs to be added. Furthermore, for industrial production, the cost of equipment and power required for grinding may be excessive.

Bicarbonate in the acidic component remover of the present invention
Sodium is found in the pore distribution of the powder layer by the mercury intrusion method.
And the pore volume in the range of pore diameter of 1 to 10 μm is 0.4
cm ^Three/ G or more. In this specification
Therefore, the pore distribution of the powder layer by the mercury intrusion method is
The value measured by the mercury intrusion method for the thorium powder layer
Good, specifically, a cylinder with a diameter of 15 mm and a height of 30 mm
0.25 g of powder was lightly dropped from spatula
The measurement is performed on the powder layer that has been filled in such a way that it is dropped. Less than,
When simply called the pore volume, the value measured by this method
Shall be referred to.

Further, it is preferable that the sodium bicarbonate obtained by baking at 200 ° C. for 1 hour has the same powder characteristics as sodium bicarbonate. That is, the obtained sodium carbonate has a pore volume in the range of pore diameter of 1 to 10 μm in the pore distribution of the powder layer by the mercury intrusion method of 0.1 μm.
It is preferably at least 4 cm ³ / g.

The baking operation for converting sodium bicarbonate into sodium carbonate is performed by spraying 5 g of sodium bicarbonate thinly on a 60 mm diameter petri dish preheated to about 200 ° C., and keeping the hot air maintained at 200 ° C. It carried out by leaving still in a circulation dryer and taking out after 1 hour.

When the pore volume of sodium hydrogen carbonate and sodium carbonate in the range of pore diameter of 1 to 10 μm is in the above range, high removal efficiency of acidic components can be exhibited.
The mechanism of the manifestation of this effect is not clear in detail, but the ease of diffusion of the acidic component to the acidic component removing agent and the pore diameter of 1
It is believed that there is a correlation between pore volume in the range of 〜１０10 μm. That is, in the acidic component-removing agent of the present invention, since the average particle size of sodium hydrogen carbonate is 9 μm or less, pores having a large diameter of 1 μm or more are formed when sodium carbonate is formed, and as a result, the particle shape becomes It is presumed that the diffusion of gas is facilitated by the fact that the surface becomes largely uneven and shows an irregular contour.

In the case where the average particle size of sodium bicarbonate exceeds 9 μm, pores having a diameter of 1 μm or more are not formed, or even if formed, the ratio is low. For example, sodium bicarbonate having an average particle size of 83 μm
When calcined for 1 hour, the resulting sodium carbonate has a pore volume of 0.30 cm ^{3 with} a pore diameter of 0.1 to 1.0 μm.
/ G, pore volume of 1.0 to 10 μm is 0.04
cm ³ / g. When sodium bicarbonate having an average particle size of 21 μm is calcined at 200 ° C. for 1 hour, the obtained sodium carbonate has a pore volume of 0.18 to 1.0 μm, a pore volume of 0.28 cm ³ / g, 1.0 to 10 μm in diameter
Has a pore volume of 0.24 cm ³ / g.

That is, most of the pores have a pore diameter of 0.1 to
1.0 μm, and the particles have a shape with relatively fine pores. For this reason, the acidic component needs to be diffused through a thin and long flow path, and it takes time to diffuse the acidic component, which is inconvenient for the reaction. On the other hand, a pore diameter of 1.0 to 1 which is considered to be effective for removing an acidic component in a short time.
Since the pore volume of 0 μm is less than 0.4 cm ³ / g,
Poor absorption of acidic components.

When sodium bicarbonate is calcined at a temperature of 100 ° C. or higher, it becomes sodium carbonate. For example, when observing sodium carbonate obtained by baking sodium bicarbonate at 200 ° C. for 1 hour, no significant change occurs in the average particle size before and after baking. Specifically, the average particle size of sodium bicarbonate observed by the present inventors was 0.7 to 50 μm.
In the range, the average particle size hardly changes before and after firing.

Sodium hydrogen carbonate (molecular weight 84.01,
The difference between the true volume of specific gravity 2.19) and the true volume of sodium carbonate (molecular weight 105.99, specific gravity 2.53) obtained from the sodium hydrogencarbonate is 0 based on the mass of sodium carbonate. 0.33 cm ³ / g. That is, when sodium bicarbonate becomes sodium carbonate while maintaining its outer shape, 0.33 cm ³ / g is the pore volume of sodium carbonate. When this sodium carbonate reacts with hydrogen chloride to form a salt (molecular weight 58.44, specific gravity 2.161), the pore volume decreases due to a slight increase in the true volume. 19c
A pore volume of m ³ / g remains. This is one of the reasons why sodium bicarbonate has a higher reaction rate than calcium-based acidic component removers such as slaked lime, and is an inherently advantageous point.

In the conventional calcium-based acidic component remover, a water-insoluble calcium salt other than calcium chloride is generated from the excessively used acidic component remover in the process of treating the acidic component to produce solid waste. . On the other hand, in the acidic component remover of the present invention, in the case of hydrogen chloride, the product in the process of treating the acidic component is mainly sodium chloride and sodium carbonate. For this reason, if separated from fly ash such as other heavy metals, it can be dissolved and treated in water, and the amount of solid waste can be reduced. In this respect, a potassium-based acid component remover is also advantageous, but potassium-based sodium bicarbonate is more advantageous in terms of high hygroscopicity and the price at the time of general availability.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The acidic component-removing agent of the present invention can be produced, for example, by pulverizing sodium bicarbonate having an average particle size of 50 μm or more so that the average particle size becomes 9 μm or less. As a pulverization method, either dry pulverization or wet pulverization can be adopted.

In the case of dry pulverization, it is preferable to use an impact pulverizer (a pulverizer using high-speed rotating blades), a jet mill (a pulverizer using an impinging air flow), a ball mill, or the like. When the sodium bicarbonate is pulverized while classifying the particles discharged from the pulverizer and returning the coarse particles to the pulverizer again using an impact type pulverizer equipped with an air classifier, the desired yield can be obtained with a high yield. It is more preferable since sodium bicarbonate having a particle size can be obtained. Also, when using a jet mill,
It is suitable for pulverization as a pulverization method, and is preferable because sodium bicarbonate having a target particle size can be obtained in a high yield without removing coarse particles by sieving.

In the case of wet pulverization, it is preferable to use a medium stirring mill, a ball mill or the like. Particularly, when a slurry in which sodium bicarbonate is dispersed in a liquid that does not substantially dissolve or deteriorate sodium bicarbonate is wet-pulverized with a medium stirring mill or a ball mill, and the obtained sodium bicarbonate is separated and dried. Is preferable since sodium bicarbonate having a small average particle size can be obtained. As the liquid that does not substantially dissolve sodium bicarbonate, a liquid that does not deteriorate due to the alkalinity of sodium bicarbonate and has a low viscosity is preferable.

[0028] Such liquids include methanol, ethanol and the like.
Tanol, acetone, C_FourF₉OCH _ThreeAnd the like.
Liquids that do not substantially dissolve sodium bicarbonate
Those having a solubility of sodium hydrogen of 3% by mass or less are preferred.
More preferably, the solubility is 1% by mass or less.
New

The acidic component remover of the present invention has an average particle size of 1 to 1.
In addition to 9 μm sodium bicarbonate, it contains other components for removing acidic components such as potassium bicarbonate, slaked lime, calcium carbonate, zeolite, adsorbents such as activated carbon, and anti-caking agents such as silica and diatomaceous earth. Is also good. It is preferable that 70% or more of sodium bicarbonate having an average particle size of 1 to 9 μm is contained in the total mass of the acidic component remover.

In the acidic component removing agent of the present invention, since sodium bicarbonate having a smaller particle size than conventional ones is used, it solidifies when stored for a long period of time. The acidic component-removing agent of the present invention can be supplied directly from the storage tank into the gas to be treated, but when sodium bicarbonate solidifies, the fluidity as a powder is reduced, and the discharge from the storage tank is deteriorated. Dispersion may be poor and the reactivity with acidic components may be reduced. Therefore, it is preferable to add an anti-caking agent to the acidic component remover. By adding the anti-caking agent, the fluidity is maintained, and the acid component removing agent can be stored in the storage tank.

As the anti-caking agent, fumed silica,
Preferred are silica-based powders such as white carbon, basic magnesium carbonate, calcium carbonate, diatomaceous earth and the like. In particular, fine silicic anhydride called fumed silica,
It is preferable because a small amount is effective. Although the optimum amount of the anti-caking agent varies depending on the degree of pulverization of sodium bicarbonate and the state of storage, it is 0.1 to 5% of the total mass of the acidic component remover containing the anti-caking agent, particularly 0.3%. ~ 2% is preferred.

Here, the fumed silica includes those subjected to a hydrophobic treatment and hydrophilic ones which are not subjected to a hydrophobic treatment. The use of hydrophobicized hydrophobic silica improves the fluidity of the acidic component remover in the gas, but if it is dissolved in water after the treatment of the acidic component, it slightly floats in the water. The use of hydrophilic fumed silica is preferred for treating boiler exhaust gas. For example, in a boiler, the presence of moisture in the absorption tower of a flue gas desulfurization apparatus causes hydrophobic silica to aggregate on the water surface to form a film, which may cause foaming.

On the other hand, when the gas is treated in a dry manner, the above problem does not occur even if hydrophobic silica is contained as an anti-caking agent. In addition, since the ratio of hydrophobic silica suspended in water after exhaust gas treatment is small, it is possible to dissolve the dust in water using an acidic component remover containing hydrophobic silica in exhaust gas treatment of garbage incineration plants, etc. In that case, the floating portion may be removed by filtration or the like.

As a countermeasure for preventing the solidification of the acidic component remover of the present invention, there is a method other than the above method in which sodium hydrogen carbonate having an average particle size of 50 μm or more is added to the acidic component remover. The acidic component remover obtained by this method has two peaks in a range of 1 to 9 μm and a range of 50 to 200 μm in a volume-based average particle size distribution measured by a laser diffraction scattering method, and 44 μm. It is preferable to include sodium bicarbonate in which the volume of particles having a particle size exceeding 10 to 30% of the total volume.

Instead of measuring the content ratio of particles having a particle size exceeding 44 μm by laser diffraction scattering, it is also possible to measure the particle size distribution by sieving to measure the content ratio (mass ratio) of particles having a relatively large particle size. it can. Since the crystals of sodium bicarbonate are not porous or hollow and have a uniform density, the content ratio can be regarded as the same regardless of the volume basis or the mass basis. Specifically, a sieve having an opening of 45 μm is used, and the particle size distribution by sieving is measured. At this time, sodium bicarbonate having a particle size exceeding 45 μm contains sodium bicarbonate which is 10 to 30% of the total mass of the acidic component removing agent, and has a volume-based average particle size distribution measured by a laser diffraction scattering method of 1 to 1. It is preferable to have two peaks in the range of 9 μm and in the range of 50 to 200 μm.

The content of sodium bicarbonate having an average particle size of 50 to 200 μm is 1% of the total mass of the acidic component remover.
0-30% is preferred. When the content of sodium hydrogen carbonate having an average particle size of 50 to 200 μm is less than 10%, the effect of improving the fluidity cannot be substantially obtained. When the content of sodium bicarbonate having an average particle size of 50 to 200 μm is 30
%, The removal efficiency of acidic components may be reduced.

When sodium bicarbonate having a large average particle size is added, the acidic component remover itself (sodium bicarbonate having an average particle size of 1 to 9 μm and an average particle size of 50 to 2) is used.
(00 μm sodium bicarbonate) and the reaction product with acid gas dissolve in water. For this reason, the amount of water-insoluble matter after treatment of acidic components is reduced compared to the case where anti-caking agents with low solubility in water such as silica-based powder, basic magnesium carbonate, calcium carbonate, and diatomaceous earth are used. It is also possible to suppress the generation of dust due to the anti-caking agent which is fine powder. Also,
Sodium hydrogen carbonate having an average particle size of 50 μm or more can be used in combination with an anti-caking agent such as fumed silica. At this time, the content of the anti-caking agent depends on the anti-caking agent and the average particle size of 50 to 20.
It is preferably 0.1 to 5% of the total mass of the acidic component remover containing 0 µm of sodium bicarbonate. In this case, the average particle size is 50
The amount of the anti-caking agent to be added can be reduced as compared with a case where sodium bicarbonate of up to 200 μm is not added.

Examples of the gas containing an acidic component that can be treated by the acidic component removing agent of the present invention include hydrogen chloride and hydrogen fluoride from an incinerator for industrial waste such as polyvinyl chloride, municipal waste, medical waste, and the like. Exhaust gas containing, for example, a combustion gas containing sulfur oxides and nitrogen oxides, a gas containing an acidic component as an impurity in the production process of various products, and the like.

As a method for removing an acidic component in a gas using the acidic component removing agent of the present invention, the acidic component removing agent of the present invention is dispersed in a gas containing an acidic component, and collected by a bag filter or the like. The method is preferred. According to this method, a filtration layer of the acidic component removing agent is formed on the surface of the bag filter, so that the acidic component can be efficiently removed. The temperature of the gas containing the acidic component is preferably higher than the acid dew point, but from the viewpoint of suppressing the generation of dioxin, a lower temperature is preferable, and specifically 100 to 200 ° C is preferable.

[0040]

[Example 1] An impact-type pulverizer equipped with a wind-type classifier (manufactured by Hosokawa Micron Corporation, manufactured by Asahi Glass Co., Ltd.) Name: ACM Pulverizer A
Using sodium chloride (CM10A), the sodium hydrogen carbonate discharged from the grinder was classified, and the coarse particles were ground again while returning to the grinder to obtain sodium hydrogen carbonate having an average particle size of 9 μm. According to this pulverizer, 150 kg of sodium bicarbonate could be pulverized to the above-mentioned average particle size in one hour, and coarse particles were not removed by sieving.

Example 2 (Comparative Example) High-speed pulverization of sodium bicarbonate having an average particle size of 92 μm by the impact and repulsion of a pin mounted on a disk rotating at a high speed and a pin mounted on a fixed disk. Rotary pin mill (Nara Machinery Co., Ltd., trade name: free crusher M-5)
500kg in 1 hour with fine grinding
The coarse particles were removed with a sieve having a size of μm to obtain sodium hydrogen carbonate having an average particle size of 38 μm. The yield was 83%. The coarse particles can be returned to the mill and remilled, but
The process becomes complicated as compared with the pulverizers of No. In addition, the use of a sieve to classify a large amount industrially is practically 4 times.
The lower limit is about 5 μm, and it is difficult to obtain sodium bicarbonate having a particle size of 9 μm or less.

Example 3 (Comparative Example) A high-speed rotary hammer mill (trade name: Atomizer C-20, manufactured by Fuji Paudal Co., Ltd.) that grinds sodium bicarbonate having an average particle size of 92 μm with a hammer rotating at a high speed. 1000)
After finely pulverizing the kg for 1 hour, coarse particles were removed with a sieve having openings of 100 μm to obtain sodium hydrogen carbonate having an average particle size of 28 μm. The yield was 8%.

Example 4 A sodium bicarbonate having an average particle size of 92 μm was added to a jet mill (trade name: Single Track Jet Mill STJ-200, manufactured by Seishin Enterprise Co., Ltd.).
6 kg in 1 hour with a mold) and average particle size 4 μm
Of sodium bicarbonate was obtained. It was not necessary to remove coarse particles by sieving, and almost the entire amount could be obtained as a product.

Example 5 Sodium hydrogen carbonate having an average particle size of 92 μm was wet-pulverized using an alumina ball mill. The ball mill used was a table-top ball mill having an internal volume of 866 cm ³ , and a ball made of alumina having a diameter of 10 to 15 mmφ was placed at 430 cm ³ and a mass of 782 g was used. The sodium hydrogencarbonate (60 g) and ethanol (200 g) were put therein and operated at 100 rpm for 24 hours to obtain a fine powder slurry of sodium hydrogencarbonate. The obtained sodium hydrogencarbonate slurry was thinly placed in a stainless steel vat and allowed to dry in a 40 ° C. explosion-proof dryer for 5 hours to obtain sodium hydrogencarbonate having an average particle size of 8 μm.

Example 6 Nato hydrogen carbonate having an average particle size of 92 μm
180 g of lithium and 600 g of C_FourF₉OCH _ThreeDispersed in
After that, using a bead mill, which is a kind of medium stirring mill,
Fine powder of sodium bicarbonate by wet grinding
Got a rally. The used bead mill has an internal volume of 1400c
m^ThreeAnd the material was zirconia. Beads are flat
Zirconia with an average diameter of 0.65 mmφ is 1120c
m^ThreeWe put and used. The operating conditions are as follows:
pm and ground for 20 minutes. This sodium bicarbonate
Put the slurry thinly in a stainless steel vat and add 4
Dry for 5 hours in a dryer at 0 ° C and average particle size of 1.5 μm
Of sodium bicarbonate was obtained.

Example 7 (Comparative Example) Beads having an average diameter of 0.3
A sodium hydrogen carbonate slurry was obtained in the same manner as in Example 6 except that the zirconia beads were changed to zirconia beads having a diameter of mm and the pulverization time was changed to 30 minutes.
Of sodium bicarbonate was obtained.

[Measurement of Pore Distribution] The pore distribution as a powder layer of sodium bicarbonate having an average particle diameter of 9 μm obtained in Example 1 was measured using a mercury intrusion-type pore diameter measuring device (manufactured by Shimadzu Corporation). Name Micromeritic Pore Sizer 931
0). The result is expressed as pore diameter 0.0
Less than 1 μm, 0.01-0.1 μm, 0.1-1 μm,
As a pore volume corresponding to 1 to 10 μm and more than 10 μm,
It is shown in Table 1. Further, the pore distribution of this sodium hydrogen carbonate was also measured by a nitrogen adsorption method. The measurement by the nitrogen adsorption method was performed using a nitrogen gas adsorption amount measurement type pore distribution measurement device (manufactured by Nippon Bell Co., Ltd., trade name: Bellsoap 28). Table 1 also shows the results.

In Table 1, the mercury method pore volume is a pore volume measured by a mercury intrusion method, and the nitrogen method pore volume is a pore volume measured by a nitrogen adsorption method. In the nitrogen method pore volume, a portion having a pore diameter of 1 μm or more cannot be measured. This notation is the same in Table 2 below.

[0049]

[Table 1]

From Table 1, it can be seen that this sodium bicarbonate has most of the pores at the pore diameter of 1 to 10 μm in the mercury method pore volume. 0.1μm pore diameter
The point having less than substantially no pores can be confirmed from both the mercury method pore volume and the nitrogen method pore volume.

When this sodium hydrogen carbonate was allowed to stand in a constant-temperature oven at 200 ° C. for 1 hour and calcined, the average particle size was 9%.
μm of sodium carbonate was obtained. Table 2 shows the pore distribution of this sodium carbonate measured in the same manner as the above-mentioned sodium hydrogen carbonate.

[0052]

[Table 2]

From Table 2, it can be seen that most of the pores of sodium carbonate are in the range of pore diameter of 1 to 10 μm. In sodium carbonate, there are a few pores having a pore diameter of 0.1 to 1 μm, but when the pore diameter is less than 0.1 μm, there are substantially no pores. It can be confirmed from both pore volumes.

When the particle shapes of the sodium hydrogen carbonate and sodium carbonate were observed with an electron microscope, the sodium bicarbonate had a smooth particle surface, but had an inner diameter of 1 μm to several μm on the surface of the sodium carbonate.
m.

Next, the pore distribution of the sodium hydrogen carbonate obtained in Examples 2 to 7 was measured in the same manner as in Example 1. Among them, a pore volume having a pore diameter of 0.1 to 1 μm by a mercury intrusion method is defined as a pore volume A, and a pore volume having a pore diameter of 1 to 10 μm by a mercury intrusion method is defined as a pore volume B. Volume A
And only the pore volume B is shown in Table 3. In Table 3, the results are rearranged in ascending order of the average particle size of sodium hydrogencarbonate including those of Example 1. Further, the sodium bicarbonate obtained in Examples 2 to 7 has substantially no pores with a pore diameter of less than 0.1 μm, from both the mercury method pore volume and the nitrogen method pore volume. It could be confirmed.

[0056]

[Table 3]

Next, the sodium hydrogen carbonate obtained in Examples 2 to 7 was left in a thermostatic oven at 200 ° C. in the same manner as in Example 1, and the pore distribution of the obtained sodium carbonate was determined in the same manner as in Example 1. It was measured. Table 4 shows only the pore volume A and the pore volume B among them. In Table 4, the values are rearranged in ascending order of the average particle size, including the numerical values of sodium carbonate obtained from the sodium hydrogencarbonate of Example 1. In addition, it was confirmed from both the mercury method pore volume and the nitrogen method pore volume that these sodium bicarbonate had substantially no pores when the pore diameter was less than 0.1 μm.

[0058]

[Table 4]

[Removal Test of Acidic Component] With respect to the ground sodium bicarbonate obtained in Examples 1 to 7, the absorption performance of the acidic component was evaluated as follows. A vertically held fluororesin pipe (inner diameter 50 mm, length 100 mm) was filled with 30 g of sodium bicarbonate, and both ends were sealed with a glass filter cloth. Air heated to 200 ° C. was passed through the glass filter cloth from the lower part to the upper part of the pipe, and gaseous hydrogen chloride was injected so as to have a concentration of 600 vol ppm before entering the filter cloth.

The total amount of hydrogen chloride flowed was twice the theoretical reaction amount of sodium carbonate and hydrogen chloride when the total amount of sodium hydrogen carbonate in the sample was sodium carbonate. The air flow rate was 1 m / s with respect to the cross-sectional area of the sodium hydrogen carbonate packed bed. The sodium carbonate removed from the pipe was neutralized and titrated with 1 mol / l hydrochloric acid to determine the unreacted amount, thereby obtaining the absorption rate of hydrogen chloride.
Table 5 shows the results. In Table 5, the particles are rearranged in ascending order of the average particle size of sodium hydrogen carbonate.

[0061]

[Table 5]

With the acidic component remover of Example 1, a high removal rate of 91% was achieved, whereas in Examples 2 and 3,
Only low removal rates were obtained. In Examples 2 and 3, as compared with Example 1, pores having a pore diameter of 0.1 to 1.0 μm remained, and the development of pore volume having a pore diameter of 1 to 10 μm was insufficient. It is estimated that the diffusion of the gas became rate-limiting and the absorption rate of chlorine gas was low. In fact, for the particles of Examples 2 and 3, it was confirmed by observation with an electron microscope that the surfaces of the particles had sponge-like holes of 0.1 to 1.0 μm. In addition, the reason why the removal rate of hydrogen chloride gas is low in Example 7 is that the acidic component remover is easily aggregated due to the fine powder, and the filling structure becomes non-uniform when filling the pipe. It is estimated that the hydrogen chloride gas was drifted.

[Example 8] Hydrophobic fumed silica having an average particle diameter of 0.01 µm (trade name: Leolosil MT-10, manufactured by Tokuyama Corporation) was added to the finely ground sodium hydrogen carbonate of Example 1 as an anti-caking agent. The mixture was added and mixed so as to be 1.0% by mass in the whole amount of the mixture. As an evaluation method, evaluation was carried out using a suspended powder layer adhesion measuring instrument (manufactured by Hosokawa Micron Co., Ltd., trade name: Kohitester) using a two-piece cell.

That is, the sample was placed in two cylinders (inner diameter 50
(height: 20 mm, height: 20 mm) was packed in a two-segment cell formed by stacking on the bottom surface, and pressurized with a preconsolidation load of 8.8 × 10 ³ Pa to compress the powder layer. One of the cells was pulled at a rate of 2 mm per minute in a direction perpendicular to the axis of the cylinder, a shear stress was applied to the powder layer at the bottom of the cylinder, and the tensile force at break of the powder layer was measured. 0.9 × 10 ² Pa with the anti-caking agent added, whereas sodium bicarbonate without the anti-caking agent added 4.
It was 3 × 10 ² Pa. Table 6 shows the tensile force at break measured in the same manner by changing the addition amount of the anti-caking agent in units of Pa.

In addition, these sodium hydrogen carbonate 500
kg was filled in a flexible container, and the state after 60 days was confirmed. As a result, no solidification was observed in sodium hydrogen carbonate to which 1% of fumed silica was added. On the other hand, in the sodium bicarbonate to which fumed silica was not added, a portion solidified in a fist-sized manner was observed.

As anti-caking agent, white carbon having an average particle size of 11.8 μm (manufactured by Tokuyama Co., Ltd., trade name: Tokusil GU-N) and basic magnesium carbonate having an average particle size of 9.6 μm (manufactured by Asahi Glass Co., Ltd.) were used. Table 6 also shows the results of similarly measuring the tensile force at the time of breaking of the powder layer. It can be seen that the addition of fumed silica is most effective.

[0067]

[Table 6]

Example 9 (Example) The average particle size of Example 5 was 8 μm.
Of sodium bicarbonate and sodium bicarbonate having an average particle size of 92 μm were mixed at the ratio shown in Table 7. This mixture had peaks at around 8 μm and around 92 μm in a volume-based average particle size distribution measured by a laser diffraction scattering method. The tensile force at the time of breaking the powder layer was measured in the same manner as in Example 8. Table 7 shows the results. The content of particles not passing through a sieve having an opening of 45 μm in the total mass of the sodium hydrogencarbonate particles was measured as follows.

That is, the sieve has an inner diameter of 200 mm and the openings are 250 μm, 150 μm and 10 μm, respectively.
Five sieves of 5 μm, 75 μm and 45 μm were stacked in this order from above and shaken for 15 minutes with a low tap shaker to measure the particle size distribution (mass basis). And
The content of particles that did not pass through a sieve having an opening of 45 μm was calculated, and is shown in Table 7.

[0070]

[Table 7]

[0071]

The acidic component remover of the present invention can be used industrially effectively in removing acidic components, particularly hydrogen chloride components, in exhaust gas. In the present invention, since the reactivity between the acidic component remover and the hydrogen chloride gas is good, a small amount of the acidic component remover can sufficiently adsorb and remove the hydrogen chloride gas. In addition, since salt and unreacted sodium carbonate, which are reaction products, are water-soluble, dust after removal of acidic components in exhaust gas is dissolved in water. The heavy metals can be separated and removed from the aqueous solution of sodium chloride and sodium carbonate by selectively precipitating them as hydroxides, sulfides or carbonates, or by performing ion exchange. Further, oxides insoluble in the aqueous solution can be separated as they are. Therefore, according to the present invention, there is an excellent effect that the amount of waste can be greatly reduced.

That is, the acidic component remover of the present invention can efficiently remove acidic components, particularly hydrogen chloride, in exhaust gas discharged from a garbage incineration plant and the like, and can reduce incineration residues generated. It has the effect of preventing the generation of calcium scale and can greatly reduce the effect on the environment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B02C 19/06 C01D 7/38 23/30 B01D 53/34 134A C01D 7/38 (72) Inventor Masaharu Tanaka (72) Inventor Ryo Kusaka 10 Goi Kaigan, Ichihara-shi, Chiba Prefecture Asahi Glass Co., Ltd.

Claims (12)

[Claims] An acidic component-removing agent containing sodium hydrogencarbonate having a volume-based average particle size of 1 to 9 μm as measured by a laser diffraction scattering method. 2. The sodium bicarbonate according to claim 1, wherein a pore volume in a pore diameter range of 1 to 10 μm is 0.4 cm ³ / g or more in a pore distribution of the powder layer by a mercury intrusion method. Acid component remover. 3. The sodium bicarbonate is obtained by calcination of sodium bicarbonate at 200 ° C. for 1 hour, in a pore distribution of a powder layer of sodium carbonate obtained by a mercury intrusion method.
The pore volume in the range of pore diameter of 1 to 10 μm is 0.4 cm ³
/ G or more. 4. An average particle size distribution on a volume basis measured by a laser diffraction scattering method in a range of 1 to 9 μm and 50
An acidic component-removing agent containing sodium hydrogencarbonate, which has two peaks in the range of ２００200 μm and the mass of particles that do not pass through a sieve having an opening of 45 μm in the analysis by sieving is 10 to 30% of the whole. 5. The acidic component-removing agent according to claim 1, further comprising an anti-caking agent. 6. The acidic component-removing agent according to claim 5, wherein the anti-caking agent is silica. 7. The acidic component remover according to claim 1, wherein the acidic component to be removed is hydrogen chloride. 8. The method for producing an acidic component-removing agent according to claim 1, wherein the particles discharged from the pulverizer are classified using an impact pulverizer equipped with an air classifier. A process for pulverizing sodium bicarbonate while returning the coarse particles to the pulverizer again. 9. The method for producing an acidic component-removing agent according to claim 1, wherein the sodium bicarbonate is pulverized using a jet mill. 10. The method for producing an acidic component-removing agent according to claim 1, wherein sodium bicarbonate is dispersed in a liquid that does not substantially dissolve sodium bicarbonate to form a slurry. A method for producing an acidic component-removing agent, comprising wet-grinding a slurry with a medium stirring mill or a ball mill, separating and drying the obtained sodium hydrogen carbonate. 11. An acidic component-removing agent according to claim 1, dispersed in a gas to be treated,
A method for removing acidic components in a gas, wherein the acidic components are collected by a bag filter. 12. An acidic component-removing agent containing sodium bicarbonate having an average particle diameter of 1 to 9 μm on a volume basis measured by a laser diffraction scattering method and hydrophobic silica as an anti-caking agent is added. A method for removing acidic components from exhaust gas from garbage incineration plants.