JP2006239689A - Acid component-removing agent, method for producing it and method for removing acid component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acid component-removing agent that can efficiently adsorb and remove acid components such as hydrogen chloride and sulfur oxide, e.g., from waste gas in refuse incineration and combustion waste gas discharged from boilers and the like and can facilitate final waste disposal. <P>SOLUTION: This acid component-removing agent comprises sodium hydrogencarbonate that has a volume-based mean particle diameter of from 1 to 9 μm as measured by a laser diffraction and scattering method and, in a pore distribution in a powder layer form as measured by mercury porosimetry, the pore volume of pores having a diameter in the range of 1 to 10 μm is not less than 0.4 cm<SP>3</SP>/g. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In order to absorb and remove hydrogen chloride and sulfur oxide from exhaust gas discharged from a refuse incinerator or the like, it is known to use slaked lime as an acidic component remover. 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, collected by a bag filter or an electric dust collector, etc. to form a filtration layer and become acidic Ingredients are removed.

  However, since slaked lime needs to be used in an excess of 3 to 4 times the reaction equivalent, there is a drawback that the amount of dust to be discarded increases. Furthermore, since these dusts are solidified using concrete, they are putting pressure on the landfill site. The reaction product of hydrogen chloride and slaked lime is calcium chloride and is water-soluble, so it can be dissolved and removed in water, but some of the slaked lime that is added excessively becomes quick lime but is insoluble in water. There is little reduction effect of dust by water. Furthermore, at the final disposal site, calcium scale is generated during the treatment of leachate containing calcium chloride, causing trouble.

  Moreover, it is known to use sodium hydrogen carbonate as an acidic component removing agent instead of slaked lime. In this case, unreacted sodium hydrogen carbonate is converted to sodium carbonate, which is effective in reducing dust because of its water solubility. For example, JP-A-9-507654 describes an acidic component remover composed of a composition containing sodium hydrogen carbonate in excess of 98 mass% and sodium carbonate in less than 2 mass%. It is described that the average particle size of this composition is 50 μm or less, preferably 10 to 30 μm.

However, since the price of sodium hydrogen carbonate is higher than that of slaked lime, it is desired to supply sodium hydrogen carbonate at a low cost and on an industrial scale, which has a high reaction rate and is effective in a small amount. In addition, there is no need to install a pulverizer at the time of use, it can be used immediately, easy and stable injection into the gas to be treated, it is well dispersed in the gas, the reaction rate is fast, and the storage tank at the place of use It is desirable that it can be stored for a long time in a warehouse.
JP-T 9-507654

  Generally, slaked lime is used as an acidic component removing agent in a garbage incineration plant or the like. Although slaked lime is inexpensive, there are problems in waste disposal, such as an increase in water-insoluble dust to be discarded as described above, and troubles due to the generation of calcium scale in the leachate at the final disposal site. Moreover, since it is expensive when using sodium hydrogencarbonate, it is necessary to increase the reaction efficiency and reduce the amount used. Moreover, if the amount used can be reduced, the incidental equipment can be reduced in size, and dust to be processed can be reduced.

  Therefore, the present invention industrially provides an acidic component remover that can efficiently remove acidic components such as hydrogen chloride, sulfur oxides, and nitrogen oxides from exhaust gas, and can be easily disposed of to reduce the amount of waste. With the goal.

In the present invention, the volume-based average particle diameter measured by the laser diffraction scattering method is 1 to 9 μm, and the pore volume in the pore diameter range of 1 to 10 μm in the pore distribution by the mercury intrusion method of the powder layer The present invention provides an acidic component remover containing sodium hydrogen carbonate having a hydrogen content of 0.4 cm ³ / g or more and a method for producing the same.

  In the acidic component removing agent of the present invention, the average particle diameter of sodium hydrogen carbonate refers to the numerical value of the average particle diameter on a volume basis measured using a laser diffraction / scattering particle size distribution analyzer. Hereinafter, when the average particle diameter is simply referred to, it means a value measured by this method. In addition, in this specification, the average particle diameter was measured using the Nikkiso Co., Ltd. brand name: 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 remover of the present invention is applied to a compound containing chlorine such as hydrogen chloride, the reaction efficiency is higher and the use is easier than before. Hereinafter, hydrogen chloride will be described, but the same applies to other acidic components.

  When sodium hydrogen carbonate is used, when the sodium hydrogen carbonate particles are converted to sodium carbonate by firing, the particles become porous and react efficiently with hydrogen chloride, thereby efficiently removing hydrogen chloride. By measuring and observing in detail the particle size, pore distribution and shape of sodium bicarbonate and sodium carbonate before and after firing, the present inventors have reacted the pore structure and hydrogen chloride obtained by the porous structure. The characteristics were found to be sensitively influenced by the average particle size of sodium hydrogen carbonate, and the present invention was achieved.

  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 diameter of sodium hydrogen carbonate exceeds 9 μm, when sodium hydrogen carbonate is baked into sodium carbonate, fine holes with a diameter of several tens of nm or less are maintained while maintaining the contour of the outer surface of sodium hydrogen carbonate. Becomes spongy sodium carbonate particles. On the other hand, when the average particle size of sodium hydrogen carbonate is 9 μm or less, pores having a relatively large diameter are formed with respect to the particle size, so that the particle shape has a rough surface and an irregular shape. Become.

  The gist of the present invention is that when sodium hydrogen carbonate having an average particle size of 9 μm or less is baked to become sodium carbonate, the above-mentioned special pore structure is obtained, and this pore structure is very effective in absorbing acid gas. Is effective. In the prior art, although there is an example of absorption of acidic gas by sodium hydrogen carbonate having a large particle diameter, sodium hydrogen carbonate having an average particle diameter of 9 μm or less is not used, and after baking, It is not known that the pore structure and particle shape of sodium carbonate change.

  When the particles are scattered in an air stream, or when an acidic component gas such as hydrogen chloride flows through the particle gap by being trapped by a bag filter to form a particle deposition layer, It is presumed that this facilitates the diffusion and reaction of the acidic component to the particle surface and promotes the reaction with a good acidic component. Sodium bicarbonate is more preferable when the average particle size is 8 μm or less.

  The lower limit of the average particle size of sodium bicarbonate is not particularly limited in terms of reaction with the acidic component, but when the average particle size is less than 1 μm, there is a strong tendency to stick to each other, and an anti-sticking agent described later is used in combination. In some cases, sufficient fluidity cannot be maintained or a large amount of anti-sticking agent needs to be added. Furthermore, for industrial production, there is a risk that the equipment and power costs required for grinding will be excessive.

Sodium bicarbonate in the acidic component removing agent of the present invention has a pore volume in the range of pore diameters of 1 to 10 μm of 0.4 cm ³ / g or more in the pore distribution by the mercury intrusion method of the powder layer. preferable. In the present specification, the pore distribution by the mercury intrusion method of the powder layer refers to a numerical value measured by the mercury intrusion method for the sodium hydrogen carbonate powder layer, specifically, a cylindrical shape having a diameter of 15 mm and a height of 30 mm. Measurement is performed with a powder layer in which 0.25 g of powder is gently dropped from a spatula into a cell. Hereinafter, when simply referred to as pore volume, it means that measured by this method.

Furthermore, as for the sodium hydrogen carbonate in the acidic component removing agent of the present invention, it is preferable that the sodium carbonate obtained when baked at 200 ° C. for 1 hour shows the same powder characteristics as sodium hydrogen carbonate. That is, the obtained sodium carbonate preferably has a pore volume in the range of 1 to 10 μm in pore diameter of 0.4 cm ³ / g or more in the pore distribution of the powder layer by mercury porosimetry.

  In addition, the baking operation which converts sodium hydrogen carbonate to sodium carbonate is a hot-air circulating dryer in which 5 g of sodium hydrogen carbonate is thinly sprayed on a petri dish having a diameter of 60 mm preheated to about 200 ° C. and kept at 200 ° C. The sample was taken out after 1 hour.

  When the pore volume in the range of 1 to 10 μm pore diameter of sodium hydrogen carbonate and sodium carbonate is in the above range, high acidic component removal efficiency can be expressed. Although the mechanism of the manifestation of this effect is not clear in detail, there is a correlation between the ease of diffusion of the acidic component into the acidic component removing agent and the pore volume in the pore diameter range of 1 to 10 μm. it is conceivable that. That is, in the acidic component removing agent of the present invention, since the average particle diameter 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. As a result, the particle shape is It is presumed that the diffusion of gas is facilitated by the fact that the surface is greatly uneven and has an irregular outline.

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

That is, many of the pores have a pore diameter of 0.1 to 1.0 μm, and the particles have relatively thin pores. Therefore, it is necessary for the acidic component to diffuse through a thin and long channel, and it takes time to diffuse the acidic component, which is inconvenient for the reaction. On the other hand, since the pore volume with a pore diameter of 1.0 to 10 μm considered to be effective for removing the acidic component in a short time is less than 0.4 cm ³ / g, the absorption performance of the acidic component is low.

  Sodium bicarbonate becomes sodium carbonate when fired at a temperature of 100 ° C. or higher. For example, when sodium carbonate obtained by baking sodium bicarbonate at 200 ° C. for 1 hour is observed, the average particle size does not change significantly before and after baking. Specifically, when the average particle diameter of sodium hydrogen carbonate observed by the present inventors is in the range of 0.7 to 50 μm, the average particle diameter hardly changes before and after firing.

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

  In the conventional calcium-based acidic component remover, a water-insoluble calcium salt is produced in addition to calcium chloride from the acidic component remover used in excess during the treatment of the acidic component, and solid waste is produced. On the other hand, in the acidic component removing agent of the present invention, the product in the process of treating the acidic component is mainly sodium chloride and sodium carbonate in the case of hydrogen chloride, for example. For this reason, if it isolate | separates from fly ash, such as another heavy metal, since it can melt | dissolve and process in water, the amount of solid waste can be reduced. In this respect, a potassium-based acidic component remover is also advantageous, but potassium-based is highly hygroscopic, and sodium hydrogencarbonate is more advantageous in terms of cost when generally available.

  The acidic component removing agent of the present invention can be used industrially effectively in the removal of acidic components in exhaust gas, particularly hydrogen chloride components. In the present invention, since the reactivity between the acidic component removing agent and hydrogen chloride gas is good, the hydrogen chloride gas can be sufficiently removed by adsorption with a small amount of acidic component removing agent. Moreover, since the reaction product sodium chloride and unreacted sodium carbonate are water-soluble, the dust after removal of acidic components in the exhaust gas dissolves in water. The heavy metals can be separated and removed from the aqueous solution of sodium chloride and sodium carbonate by selectively precipitating as hydroxides, sulfides or carbonates or by ion exchange. Moreover, the oxide insoluble in the aqueous solution can be separated as it is. 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 removing agent of the present invention can efficiently remove acidic components, particularly hydrogen chloride, in exhaust gas discharged from a garbage incineration plant, etc., and reduce the generated incineration residue. It has the effect of preventing the occurrence and can greatly reduce the impact on the environment.

  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 is 9 μm or less. As the pulverization method, either dry pulverization or wet pulverization can be employed.

  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 a collision airflow), a ball mill, or the like. When pulverizing sodium bicarbonate while classifying particles discharged from the pulverizer and returning the coarse particles to the pulverizer again using an impact pulverizer equipped with a wind classifier, the target is obtained in a high yield. It is more preferable because sodium hydrogen carbonate having a particle size can be obtained. A jet mill is also preferred because it is suitable for pulverization as a pulverization method, and sodium hydrogen carbonate having a desired particle diameter 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. In particular, when a sodium hydrogen carbonate slurry is dispersed in a liquid that does not substantially dissolve or alter sodium bicarbonate, and is wet pulverized with a medium stirring mill or a ball mill, and the resulting sodium bicarbonate is separated and dried. Is preferable because sodium hydrogen carbonate having a small average particle diameter can be obtained. The liquid that does not substantially dissolve sodium hydrogen carbonate is preferably a liquid that does not deteriorate due to the alkalinity of sodium hydrogen carbonate and has a low viscosity.

Examples of such a liquid include methanol, ethanol, acetone, C ₄ F ₉ OCH _{3 and the} like. The liquid that does not substantially dissolve sodium bicarbonate preferably has a sodium bicarbonate solubility of 3% by mass or less, and more preferably has a solubility of 1% by mass or less.

  In addition to sodium bicarbonate having an average particle diameter of 1 to 9 μm, the acidic component remover of the present invention includes other acidic component removal components such as potassium bicarbonate, slaked lime, calcium carbonate, zeolite, adsorbents such as activated carbon, silica, You may contain anti-caking agents, such as diatomaceous earth. It is preferable that 70% or more of sodium hydrogen carbonate having an average particle diameter 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, sodium hydrogen carbonate having a smaller particle size than that of the conventional one is used, so that it is consolidated 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 to the gas to be treated. However, when sodium hydrogen carbonate is solidified, the fluidity as a powder is deteriorated and the discharge from the storage tank is deteriorated, or in the flue There is a risk that the dispersion of the resin becomes poor and the reactivity with the acidic component decreases. Therefore, it is preferable to add an anti-caking agent to the acidic component remover. The fluidity is maintained by the addition of the anti-caking agent, and the acidic component removing agent can be stored in the storage tank.

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

  Here, the fumed silica includes a hydrophobized one and a hydrophilic one that is not hydrophobized. Hydrophobic treated hydrophobic silica improves the fluidity of the acidic component remover in the gas, but if it is dissolved in water after treatment of the acidic component, it will float slightly in water, so a wet exhaust gas treatment facility will be installed. It is preferable to use hydrophilic fumed silica in the treatment of the boiler exhaust gas. For example, in a boiler, hydrophobic silica aggregates on the surface of water due to the presence of moisture in the absorption tower of the flue gas desulfurization apparatus, so that a film may be formed and foamed by the film.

  On the other hand, when the gas is treated by a dry method, the above-described troubles are not caused even if hydrophobic silica is contained as an anti-caking agent. In addition, since the proportion of hydrophobic silica floating in water after exhaust gas treatment is small, it can be treated by dissolving the dust in water using an acidic component remover containing hydrophobic silica in exhaust gas treatment of waste incinerators, etc. In that case, the floating portion may be removed by filtration or the like.

  Further, as a measure for preventing caking of the acidic component remover of the present invention, there is a method of adding sodium hydrogen carbonate having an average particle size of 50 μm or more to the acidic component remover in addition to the above method. The acidic component removing agent obtained by this method has peaks at two locations in the range of 1 to 9 μm and in the range of 50 to 200 μm in the volume-based average particle size distribution measured by the laser diffraction scattering method, and 44 μm It is preferable to include sodium hydrogen carbonate having a volume of particles having a particle diameter exceeding 10 to 30% of the whole.

  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 determine the content ratio (mass ratio) of particles having a relatively large particle size. Since the sodium hydrogencarbonate crystals are not porous or hollow and have a uniform density, the content can be regarded as the same regardless of whether the content is based on volume or mass. Specifically, the particle size distribution by sieving is measured using a sieve having an opening of 45 μm. In this case, the sodium hydrogen carbonate having a particle size of more than 45 μm contains 10 to 30% of the total mass of the acidic component removing agent, and the volume-based average particle size distribution measured by the laser diffraction scattering method is 1 to It is preferable to have peaks at two locations in the range of 9 μm and 50 to 200 μm.

  As content of sodium hydrogen carbonate with an average particle diameter of 50-200 micrometers, 10-30% in the total mass of an acidic component removal agent is suitable. 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 fluidity is not substantially obtained. When the content of sodium hydrogen carbonate having an average particle size of 50 to 200 μm exceeds 30%, the removal efficiency of acidic components may be reduced.

  When sodium bicarbonate having a large average particle size is added in this manner, the reaction with the acidic component removing agent itself (sodium bicarbonate having an average particle size of 1 to 9 μm and sodium bicarbonate having an average particle size of 50 to 200 μm) or acidic gas The product dissolves in water. For this reason, the amount of water-insoluble matter after treatment of acidic components is reduced compared with the use of anti-caking agents with low solubility in water, such as silica powder, basic magnesium carbonate, calcium carbonate, diatomaceous earth, etc. It is also possible to suppress the generation of dust due to the anti-caking agent which is fine powder. Further, sodium bicarbonate 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 is preferably 0.1 to 5% of the total mass of the acid component removing agent including the anti-caking agent and sodium hydrogen carbonate having an average particle diameter of 50 to 200 μm. In this case, the addition amount of the anti-caking agent can be reduced as compared with the case where sodium hydrogen carbonate having an average particle diameter of 50 to 200 μm is not added.

  The gas containing an acidic component that can be treated by the acidic component removing agent of the present invention includes exhaust gas containing hydrogen chloride or hydrogen fluoride from incinerators such as industrial waste such as polyvinyl chloride, municipal waste, and medical waste. Examples include gases, combustion gases containing sulfur oxides and nitrogen oxides, and gases in which acidic components are mixed as impurities in the manufacturing process of various products.

  As a method for removing an acidic component in a gas using the acidic component remover of the present invention, a method in which the acidic component remover of the present invention is dispersed in a gas containing an acidic component and collected by a bag filter or the like is preferable. . In this method, since the filtration layer of the acidic component removing agent is formed on the bag filter surface, the acidic component can be efficiently removed. Although the temperature of the gas containing an acidic component is preferably higher than the acid dew point, a low temperature is preferable from the viewpoint of suppression of dioxin production, and specifically, 100 to 200 ° C is preferable.

[Example 1]
Sodium hydrogen carbonate having an average particle size of 92 μm (made by Asahi Glass Co., Ltd., all the same in the following examples), an impact type pulverizer equipped with a wind classifier (made by Hosokawa Micron Co., Ltd., trade name: ACM Pulverizer ACM10A type) The sodium bicarbonate discharged from the pulverizer was classified, and the coarse particles were pulverized while returning to the pulverizer again to obtain sodium bicarbonate having an average particle size of 9 μm. According to this pulverizer, 150 kg of sodium hydrogen carbonate could be pulverized to the above average particle diameter in 1 hour, and coarse particle removal by sieving was not performed.

[Example 2 (comparative example)]
High-speed rotating pin mill (made by Nara Machinery Co., Ltd.) that grinds sodium bicarbonate with an average particle size of 92 μm by impact and repulsion between the pin attached to the disk rotating at high speed and the pin attached to the fixed disk (Product name: Free crusher M-5 type) 500 kg was finely pulverized in 1 hour, and then coarse particles were removed with a sieve having an aperture of 180 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 pulverizer and pulverized again, but the process is more complicated than the pulverizer of Example 1. Moreover, the industrially large-scale classification using a sieve has a practically lower limit of about 45 μm, and it is difficult to obtain sodium bicarbonate having a particle size of 9 μm or less.

[Example 3 (comparative example)]
1000 kg of sodium bicarbonate with an average particle size of 92 μm is finely pulverized in 1 hour using a high-speed rotary hammer mill (trade name: Atomizer C-20, manufactured by Fuji Paudal Co., Ltd.). Then, coarse particles were removed with a sieve having an opening of 100 μm to obtain sodium hydrogen carbonate having an average particle size of 28 μm. The yield was 8%.

[Example 4]
Sodium bicarbonate having an average particle diameter of 92 μm is finely pulverized in 6 hours in a jet mill (trade name: Single Track Jet Mill STJ-200, manufactured by Seishin Enterprise Co., Ltd.), and hydrogen carbonate having an average particle diameter of 4 μm. Sodium was obtained. The removal of coarse particles by sieving was unnecessary, and almost the entire amount could be made into a product.

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

[Example 6]
After dispersing 180 g of sodium hydrogen carbonate having an average particle size of 92 μm in 600 g of C ₄ F ₉ OCH ₃ , a fine powder slurry of sodium hydrogen carbonate is obtained by wet grinding using a bead mill which is a kind of medium stirring mill. Obtained. The bead mill used had an internal volume of 1400 cm ³ and was made of zirconia. As beads, 1120 cm ³ of zirconia having an average diameter of 0.65 mmφ was used. The operating conditions were a rotational speed of 2500 rpm and pulverization for 20 minutes. The sodium hydrogen carbonate slurry was thinly placed in a stainless steel vat and left to stand in a dryer at 40 ° C. for 5 hours to obtain sodium hydrogen carbonate having an average particle size of 1.5 μm.

[Example 7 (comparative example)]
A sodium hydrogen carbonate slurry was obtained in the same manner as in Example 6 except that the beads were changed to zirconia beads having an average diameter of 0.3 mmφ and the pulverization time was 30 minutes. 5 μm sodium hydrogen carbonate was obtained.

[Measurement of pore distribution]
Using a mercury intrusion type pore diameter measuring device (trade name: Micromeritic Pore Sizer 9310, manufactured by Shimadzu Corporation) for the pore distribution as a powder layer of sodium hydrogen carbonate having an average particle diameter of 9 μm obtained in Example 1 And measured. The results are shown in Table 1 as pore volumes corresponding to pore diameters of less than 0.01 μm, 0.01 to 0.1 μm, 0.1 to 1 μm, 1 to 10 μm, and more than 10 μm. 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 measuring device (trade name Bell Soap 28, manufactured by Nippon Bell Co., Ltd.). The results are also shown in Table 1.

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

  It can be seen from Table 1 that this sodium hydrogen carbonate has most of the pores in the portion having a pore diameter of 1 to 10 μm in the mercury method pore volume. It can be confirmed from both the mercury method pore volume and the nitrogen method pore volume that the pore diameter is less than 0.1 μm.

  When this sodium bicarbonate was left to stand in a constant temperature dryer at 200 ° C. for 1 hour and baked, sodium carbonate having an average particle size of 9 μm was obtained. Table 2 shows the pore distribution of this sodium carbonate measured in the same manner as the above-mentioned sodium bicarbonate.

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

  Further, when the particle shape of the sodium hydrogen carbonate and sodium carbonate was observed with an electron microscope, the sodium hydrogen carbonate had a smooth particle surface, but the sodium carbonate surface had a concave portion with an inner diameter of about 1 μm to several μm. It was observed.

  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, the pore volume having a pore diameter of 0.1 to 1 μm by the mercury intrusion method is defined as a pore volume A, and the pore volume having a pore diameter of 1 to 10 μm by the mercury intrusion method is defined as a pore volume B. Only the volume A and the pore volume B are shown in Table 3. In Table 3, the sodium bicarbonate is rearranged in order from the smallest average particle size including that 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.

  Next, the sodium hydrogencarbonate obtained in Examples 2 to 7 was left in a constant temperature dryer at 200 ° C. in the same manner as in Example 1, and the pore distribution of the obtained sodium carbonate was measured in the same manner as in Example 1. Of these, only pore volume A and pore volume B are shown in Table 4. In Table 4, the values are sorted in ascending order of the average particle size including the values of sodium carbonate obtained from the sodium hydrogen carbonate of Example 1. Further, it was confirmed from both the mercury method pore volume and the nitrogen method pore volume that these sodium carbonates have substantially no pores when the pore diameter is less than 0.1 μm.

[Removal test of acidic components]
About the sodium hydrogencarbonate obtained in Examples 1-7, the absorption performance of the acidic component was evaluated as follows. A fluororesin pipe (inner diameter 50 mm, length 100 mm) held vertically was filled with 30 g of sodium hydrogen carbonate, and both ends were sealed with glass filter cloth. From the bottom to the top of this pipe, air heated to 200 ° C. was passed through a glass filter cloth, and gaseous hydrogen chloride was injected so as to have a concentration of 600 ppm by volume before entering the filter cloth.

  The total amount of hydrogen chloride flowed was twice the theoretical reaction amount of hydrogen chloride to sodium carbonate when the total amount of sodium bicarbonate 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. Sodium carbonate taken out from the pipe was neutralized and titrated with 1 mol / liter hydrochloric acid to determine the unreacted amount, thereby determining the absorption rate of hydrogen chloride. The results are shown in Table 5. In Table 5, the sodium bicarbonate is rearranged in order of increasing average particle size.

  The acidic component remover of Example 1 achieved a high removal rate (hydrogen chloride absorption rate) of 91%, while Example 2 and Example 3 achieved only a low removal rate (hydrogen chloride absorption rate). There wasn't. In Example 2 and Example 3, as compared with Example 1, pores with a pore diameter of 0.1 to 1.0 μm remained, and the development of pore volume with a pore diameter of 1 to 10 μm was insufficient. It is presumed that the absorption rate of hydrogen chloride was low due to gas diffusion control. In fact, in the particles of Examples 2 and 3, it was confirmed by observation with an electron microscope that the surface of the particles was sponge-like and 0.1 to 1.0 μm holes were formed. In addition, in Example 7, the reason why the absorption rate of hydrogen chloride is low is that the acidic component remover tends to agglomerate due to fine powder, and the filling structure becomes uneven when filling the pipe, and the chlorination occurs in the packed bed of sodium bicarbonate. It is presumed that hydrogen drifted.

[Example 8]
Hydrophobic fumed silica having an average particle size of 0.01 μm (trade name Leolosil MT-10, manufactured by Tokuyama Corporation) as an anti-caking agent was added to the finely pulverized sodium hydrogen carbonate of Example 1 in the total amount of the mixture. It added and mixed so that it might become 0 mass%. As an evaluation method, the evaluation was performed by using a suspended powder layer adhesion measuring device (trade name: Kohitaster, manufactured by Hosokawa Micron Corporation) using a two-divided cell.

That is, the sample was filled in a two-divided cell in which two cylinders (inner diameter: 50 mm, height: 20 mm) were stacked on the bottom, and pressurized with a pre-consolidation load of 8.8 × 10 ³ Pa to compress the powder layer. One side of this cell 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 the time of breaking the powder layer was measured. What added the anti-caking agent was 0.9 × 10 ² Pa, while sodium hydrogen carbonate to which no anti-caking agent was added was 4.3 × 10 ² Pa. Similarly, the tensile force at break measured by changing the addition amount of the anti-caking agent is shown in Table 6 in unit Pa.

  Moreover, when 500 kg of these sodium hydrogen carbonates were filled in a flexible container and the situation after 60 days was confirmed, no caking was observed in the sodium hydrogen carbonate to which 1% of fumed silica was added. On the other hand, the sodium hydrogen carbonate to which fumed silica was not added was found to have a large amount of fists.

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

[Example 9 (Example)]
Sodium hydrogen carbonate having an average particle diameter of 8 μm and sodium hydrogen carbonate having an average particle diameter of 92 μm in Example 5 were mixed at a ratio shown in Table 7. This mixture had peaks around 8 μm and 92 μm in the volume-based average particle size distribution measured by the laser diffraction scattering method. In the same manner as in Example 8, the tensile force when the powder layer was broken was measured. The results are shown in Table 7. In addition, the content rate of the particle | grains which do not pass the sieve of 45 micrometers of openings in the total mass of sodium hydrogencarbonate particle | grains was measured as follows.

  That is, five types of sieves having an inner diameter of 200 mm and apertures of 250 μm, 150 μm, 105 μm, 75 μm and 45 μm are stacked in this order from above, and shaken for 15 minutes with a low-tap shaker. Distribution (mass basis) was measured. And the content rate of the particle | grains which did not pass the sieve of 45 micrometers of openings was computed, and it showed in Table 7.

Claims (14)

The volume-based average particle diameter measured by the laser diffraction scattering method is 1 to 9 μm, and the pore volume in the pore diameter range of 1 to 10 μm is 0.4 cm in the pore distribution by the mercury intrusion method of the powder layer. ^The acidic component removal agent containing the sodium hydrogencarbonate which is ³ / g or more. Sodium bicarbonate has a pore volume in the range of 1 to 10 μm in pore diameter in the pore distribution by the mercury intrusion method of the sodium carbonate powder layer obtained when sodium bicarbonate is baked at 200 ° C. for 1 hour. The acidic component remover according to claim 1, which is at least 4 cm ³ / g.   In the volume-based average particle size distribution measured by the laser diffraction scattering method, particles having peaks at two positions of 1 to 9 μm and 50 to 200 μm and not passing through a sieve having an opening of 45 μm in the analysis by sieving. The acidic component removal agent containing sodium hydrogencarbonate whose mass is 10-30% of the whole.   The acidic component removing agent according to claim 1, 2 or 3, comprising an anti-caking agent.   The acidic component removing agent according to claim 4, wherein the anti-caking agent is silica.   The acidic component removing agent according to claim 5, wherein the anti-caking agent is hydrophobic silica.   The acidic component removing agent according to claim 5, wherein the anti-caking agent is hydrophilic silica.   The acidic component remover according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the acidic component to be removed is hydrogen chloride.   The method for producing an acidic component remover according to claim 1 or 2, wherein an impact pulverizer equipped with a wind classifier is used to classify particles discharged from the pulverizer, and coarse particles are again pulverized. The manufacturing method of the acidic component removal agent characterized by grind | pulverizing sodium hydrogen carbonate, returning to step.   The method for producing an acidic component remover according to claim 1 or 2, wherein sodium bicarbonate is pulverized using a jet mill.   The method for producing an acidic component removing agent according to claim 1 or 2, wherein sodium bicarbonate is dispersed in a liquid that does not substantially dissolve sodium bicarbonate to form a slurry, and the slurry is a medium agitating mill or a ball mill. A method for producing an acidic component remover, characterized in that wet pulverization is carried out and the obtained sodium hydrogen carbonate is separated and dried.   The acidic component removing agent according to claim 1, 2, 3, 4, 5, 6, 7 or 8 is dispersed in a gas to be treated and collected by a bag filter. Component removal method.   An acidic component removing agent according to claim 6, wherein the acidic component removing agent according to claim 6 is added to a gas to be treated. A method for removing acidic components from exhaust gas from a boiler, wherein the acidic component removing agent according to claim 7 is added to a gas to be treated.