JP5045225B2 - Acid component removing agent and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acidic component removing agent which suppresses the pressure loss of filter cloth, prevents a filter layer from dropping from the surface of the filter cloth, hardly causes trouble when discharged from a silo or the like and has excellent handleability, and to provide its production method. <P>SOLUTION: The acidic component removing agent contains sodium hydrogen carbonate, a clay mineral and fumed silica. The content of the clay mineral is 1-5 mass% and that of fumed silica is 0.5-2.0 mass%. The average particle size of the acidic component removing agent is within 3-20 &mu;m. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an acidic component remover that removes acidic components in a gas and a method for producing the same.

  The exhaust gas generated by the incineration treatment of general waste and industrial waste contains acidic components such as hydrogen chloride and sulfur oxides. In order to absorb and remove these acidic components, a removal device using an acidic component remover is conventionally known.

  FIG. 1 is a schematic diagram showing an example of an apparatus for removing acidic components in exhaust gas. The removal apparatus shown in FIG. 1 has a silo 1 for storing a powdery acidic component removing agent M, an exhaust gas passage (flue) 2 through which an exhaust gas containing an acidic component flows, and an acidic component removing agent M for silo 1. From the supply pipe 3 supplied into the exhaust gas, and a bag filter 4 arranged on the downstream side of the exhaust gas flow path 2.

The discharge part 1a of the silo 1 is provided with a powder quantity supply device 5 such as a rotary valve 5 and a table feeder. By operating these powder quantity supply devices 5, the acidic component removing agent M is opened in the supply pipe 3 It is comprised so that it may fall to 3a.
Further, an incinerator (not shown) such as a general waste or an industrial waste is installed on the upstream side of the exhaust gas flow path 2, and the exhaust gas containing acidic components such as hydrogen chloride, nitrogen oxide, and sulfur oxide is installed. Circulates in the exhaust gas passage 2.
In addition, an air flow is circulated from the upstream side to the supply pipe 3, and the acidic component removing agent M supplied through the opening 3a can be put on the air flow and sent to the downstream side. Further, the downstream end of the supply pipe 3 is disposed in the exhaust gas flow path 2, and an ejector 3 b for ejecting the acidic component removing agent M into the exhaust gas is further attached to the downstream end.

  Next, the bag filter 4 includes a housing 41, an exhaust gas inlet 42 provided in a lower portion 41 a of the housing 41, a plurality of tubular filter cloths 43 disposed in a central portion 41 b of the housing 41, a housing 41 and an exhaust port 44 provided in an upper portion 41c of 41. The cylindrical filter cloth 43 is closed at the lower end and has a hollow portion 43a inside. Further, the upper portion 41c and the central portion 41b of the housing 41 are partitioned by a partition plate 45, so that the exhaust gas always passes through the filter cloth 43 when the exhaust gas moves from the central portion 41b of the housing 41 to the upper portion 41c. It is configured. Further, the partition plate 45 is provided with a through portion 45a, and a communication tube 46 for connecting the hollow portion 43a of the filter cloth and the upper portion 41c of the housing 41 is attached to the through portion 45a.

  Next, the operation of the above removal device will be described. The powder quantitative supply device 5 is operated to supply the acidic component removing agent M in the silo 1 to the supply pipe 3. The acidic component removing agent M supplied to the supply pipe 3 rides on the air flow and is sent to the downstream end, and is ejected into the exhaust gas by the ejector 3b. A part of the ejected acidic component removing agent M reacts with the acidic component in the exhaust gas to become a reaction product. Then, the reaction product and the unreacted acidic component removing agent M are sent to the bag filter 4 together with the exhaust gas. In the bag filter 4, the reaction product and the unreacted acidic component removing agent M are deposited on the surface of the filter cloth 43 to form a filtration layer, and the acidic component in the exhaust gas is further removed by the filtration layer. The exhaust gas from which the acidic component has been removed passes through the filter cloth 43 and is discharged from the discharge port 44 through the communication pipe 46.

In the removal device as described above, slaked lime (calcium hydroxide: Ca (OH) ₂ ) has been used as the acidic component removal agent M for treating exhaust gas at about 150 ° C. to 300 ° C., for example. However, slaked lime needs to be used in excess due to its poor reaction rate, and as a result, the amount of the filtered layer to be recovered increases, that is, the amount of the filtered layer to be discarded increases, and the final landfill The site of the disposal site is under pressure, and the reaction product of hydrogen chloride and slaked lime is calcium chloride, which is water-soluble, so it can be dissolved in water and removed, but forms a hardly soluble double salt, Processing may be difficult. In addition, since it has moisture absorption and deliquescence properties, there are difficulties in handling such as adhesion to filter cloth. In addition, slaked lime that has been added excessively is slightly soluble in water and has strong alkalinity, so the amount of dust generated is large and the effect of reducing dust by dissolving in water is small, and neutralization is necessary. There are disadvantages such as.

  Therefore, a method using sodium hydrogen carbonate instead of slaked lime has been proposed. For example, Patent Document 1 describes an acidic component remover having sodium bicarbonate as a main component and having an average particle size of 50 μm or less, preferably 10 to 30 μm. To achieve higher efficiency of removal, it is necessary to use sodium hydrogen carbonate with a smaller particle size. However, powders prepared to 30 μm or less have poor flowability or increased adhesion between particles. This may cause difficulty in stable handling such as being easy to consolidate, and there is a possibility that the removal efficiency of acidic components may deteriorate.

  That is, when the fluidity of the powder deteriorates and the adhesion between the particles increases, the acidic component remover itself easily aggregates. For example, as shown in FIG. 2A, a so-called rathole phenomenon occurs in the silo. As shown in FIG. 2B, a bridge phenomenon may occur, which may cause the supply of the acidic component removing agent to stagnate, and the removal efficiency of the removal device may be significantly reduced.

Therefore, in Patent Document 2, the fluidity obtained by using fumed silica as an anti-caking agent against the deterioration of the fluidity of the powder of finely divided sodium bicarbonate due to the adhesion between particles. Excellent powders have been proposed.
Japanese National Patent Publication No. 9-50765 JP 2000-218128 A

However, when the flowability of sodium hydrogen carbonate is extremely improved, sodium hydrogen carbonate particles easily enter the gaps between the fibers that make up the filter cloth of the bag filter, which increases the pressure loss in the filter cloth, There is a concern that the pressure difference between the gas at the inlet and the outlet (hereinafter referred to as differential pressure) increases and increases, and the flow rate of the exhaust gas decreases significantly. Further, sodium hydrogen carbonate particles may pass through the filter cloth and be observed as dust in the exhaust gas. In addition, the filtration layer deposited on the surface of the filter cloth may be peeled off from the filter cloth. In either case, there is a possibility that the removal capability of the acidic component in the entire removal apparatus may be reduced. Therefore, if it becomes possible to control the fluidity of sodium hydrogen carbonate within an appropriate range, further improvement in the ability to remove acidic components in the removal device can be expected.
Acidic component removal agent, hydrogen chloride in the combustion exhaust gas from the refuse incinerator (HCl) and sulfur dioxide _(SO 2), sulfur dioxide (SO ₂₎ and sulfur trioxide _(SO 3) of the boiler flue gas, sulfuric acid (H ₂ SO ₄ ) In addition to this, it is used for the purpose of removing acidic components in gases, and a reduction in the ability to remove acidic components leads to a reduction in the removal efficiency of harmful substances in exhaust gas, so it must be avoided for environmental conservation. .
Therefore, the present invention suppresses an increase in pressure loss in the filter cloth, prevents the filtration layer from falling off from the surface of the filter cloth, and is less likely to cause a discharge trouble from a silo, etc., and has an excellent handling property. And it aims at providing the manufacturing method.

  As a result of intensive studies to solve the above-mentioned problems, a powder containing sodium hydrogen carbonate, clay mineral, and fumed silica in an appropriate ratio and having an average particle size in the range of 3 to 20 μm has an appropriate fluidity. It has the property that it is hard to consolidate with this, thereby suppressing the rise in pressure loss in the filter cloth and preventing the filtration layer from falling off the filter cloth, and also preventing the occurrence of rat holes and bridges in the silo, Furthermore, it discovered that the removal efficiency of the acidic component in waste gas can be improved.

That is, the present invention employs the following configuration in order to achieve the above object.
The acidic component remover of the present invention is an acidic component remover that removes acidic components in exhaust gas, and contains sodium hydrogen carbonate, clay mineral, and fumed silica, and the clay mineral content is 1 to 1. 5% by mass, the content of fumed silica is 0.5 to 2.0% by mass, the average particle size is in the range of 3 to 20 μm, and the fumed silica is in the form of primary particles on the surface. It shall consist of the particle | grains which consist of the disperse | distributed sodium hydrogencarbonate.
In the acidic component removing agent, the clay mineral is preferably at least one selected from the group consisting of talc, activated clay, kaolin and bentonite.
Further, the fumed silica may be hydrophilic or hydrophobic.

The method for producing an acidic component remover of the present invention is a method for producing an acidic component remover that removes acidic components in exhaust gas, and comprises mixing sodium hydrogen carbonate, clay mineral, and fumed silica. The mixture of clay minerals is 1 to 5% by mass and the content of fumed silica is 0.5 to 2.0% by mass. The mixture has an average particle size in the range of 3 to 20 μm. In this method, the fumed silica is pulverized until it reaches the surface, and the fumed silica is coated on the surface of the sodium hydrogen carbonate in a primary particle state.
In the above production method, the clay mineral is preferably at least one selected from the group consisting of talc, activated clay, kaolin and bentonite.

  According to the present invention, an acidic component removing agent that suppresses pressure loss in a filter cloth and prevents the filtration layer from falling off the filter cloth, is less likely to cause a discharge trouble from a silo, etc., and has excellent handleability, and its A manufacturing method can be provided.

Hereinafter, the acidic component removing agent of the present invention and the production method thereof will be described in detail.
The acidic component removing agent of the present invention contains sodium hydrogen carbonate, clay mineral, and fumed silica, and the average particle size of these mixtures is in the range of 3 to 20 μm.
In this acidic component remover, it is preferable that most of the fumed silica is uniformly dispersed in the form of primary particles on the surface of the particles made of sodium hydrogen carbonate. Since most of the fumed silica is dispersed in the state of primary particles, the fluidity of the acidic component removing agent can be made moderate as compared with the case where fumed silica is present in the state of secondary particles. And agglomeration due to aggregation can be prevented. Moreover, caking of the particles which comprise an acidic component removal agent can be prevented by containing a clay mineral. As described above, since the acidic component remover of the present invention has appropriate fluidity and anti-caking ability, it suppresses the increase in pressure loss in the filter cloth and prevents the filtration layer from falling off the filter cloth surface. Moreover, it is possible to prevent discharge troubles from silos.

  The production method of the acidic component remover of the present invention is not particularly limited, and can be obtained by appropriately mixing and pulverizing by a known method. However, as will be described later, sodium hydrogen carbonate, clay mineral, and fume. It is preferable to obtain by pulverizing after mixing with silica. By crushing after mixing, not only sodium hydrogen carbonate and clay mineral are pulverized well, but fumed silica that tends to agglomerate effectively is crushed, and fumed silica on the surface of sodium hydrogen carbonate Can be applied uniformly in the state of primary particles. This is because the powder can be effectively mixed by applying a strong shear stress to the powder during pulverization.

  The average particle size of the acidic component remover is preferably in the range of 3 to 20 μm, and more preferably in the range of 5 to 10 μm. If the average particle size is 3 μm or more, the tendency of particles to adhere to each other is weakened, and even when clay minerals and fumed silica are used in combination, fluidity does not decrease, and even when a small amount of clay mineral is added, sufficient flow is achieved. It is preferable because of its property. Moreover, the problem that the particle diameter is too small to pass through the filter cloth can be avoided. Furthermore, it is preferable if the average particle size is 20 μm or less because acidic components in the exhaust gas can be efficiently removed. Moreover, if the average particle diameter of an acidic component removal agent is the range of 5-10 micrometers, since it becomes excellent in an acidic component removal performance and becomes easy to handle, it is preferable.

  In the present invention, the average particle size of the acidic component remover refers to the numerical value of the average particle size on a volume basis measured using a laser diffraction / scattering particle size distribution analyzer. In the present invention, when the average particle diameter is simply referred to, it means a value measured by this method using ethanol as a medium. In the present specification, the average particle diameter is measured by using Nikkiso Co., Ltd., trade name: Microtrac FRA9220.

 The clay mineral is mainly composed of fine layered silicate. In the present invention, the clay mineral is selected from the group consisting of talc, activated clay, kaolin, bentonite, mica, sepiolite, bentonite-containing smectite, vermiculite, and allophane. It is preferable to use at least one species, and it is more preferable to use at least one selected from the group consisting of talc, activated clay, kaolin and bentonite. As these clay minerals, those which can be stably obtained at low cost can be used regardless of natural or synthetic. In particular, talc is particularly preferable because it has lubricity.

 The reason why it is preferable to mix the clay mineral is not clear in detail, but it is presumed that the fluidity of sodium hydrogen carbonate is likely to be improved because the moisture absorbs easily due to the hygroscopic property derived from the multilayer structure of the clay mineral. In addition, by adsorbing and holding acidic components in the multilayer structure, the acidic gas is concentrated in the vicinity of sodium hydrogen carbonate, and the sodium hydrogen carbonate-acid gas neutralization reaction, which is a solid-gas reaction that is difficult to proceed by itself, is carried out. It is also expected to work to accelerate.

  Fumed silica refers to synthetic amorphous silica that is said not to cause necrosis and is produced by a dry process. Specifically, those produced by a combustion method, a self-combustion method, or a heating method can be exemplified.

  In the fumed silica, there are hydrophobic fumed silica whose surface is subjected to hydrophobic treatment such as silane treatment and silane coupling treatment, and hydrophilic fumed silica that is not subjected to hydrophobic treatment. When it is desired to obtain a powder containing sodium hydrogen carbonate, clay mineral and fumed silica, which is excellent in fluidity and easy to handle, it can be selected from hydrophilic and hydrophobic depending on the required fluidity. Hydrophilic fumed silica enhances the adhesion between particles, and in particular, the acid component remover keeps it well without increasing the pressure loss in the filter cloth and without removing the deposited layer from the filter cloth surface. . On the other hand, when hydrophobic fumed silica is selected, the powder fluidity of the acidic component remover using this improves, so it becomes difficult to form ratholes and bridges in silos, especially from silos and feeders. Emissions can be obtained.

  Of course, by mixing and using hydrophilic and hydrophobic fumed silica, it is also possible to obtain an acidic component remover that balances the improvement in pressure loss in the filter cloth and the good discharge from the silo in a balanced manner. it can. The combination of hydrophilic fumed silica and clay mineral is particularly preferable.

Hydrophobic treatment for obtaining hydrophobic fumed silica includes silane treatment such as dimethyldichlorosilane, hexamethyldisilazane, octylsilane, silane coupling agent treatment with vinyltrimethoxysilane, dimethylpolysiloxane treatment, methylhydro Although arbitrary processes, such as a gene polysiloxane process and a fatty acid process, can be illustrated, it is not limited to this.
The degree of hydrophobicity with respect to fumed silica can be measured from the amount of dimethylsilane or the like adhering to the surface of fumed silica. The adhesion amount of dimethylsilane or the like can be determined from, for example, the carbon content in fumed silica. The degree of hydrophobicity of the hydrophobic fumed silica is over 0%, preferably in the range of about 0.8 to 1%. Moreover, the hydrophobization degree of hydrophilic fumed silica is almost 0%. Moreover, the measuring method of a carbon content rate can be measured with a combustion type carbon amount measuring apparatus (for example, CN analyzer (SUMIGRAPH NC-80)).
In addition, as for the hydrophilic fumed silica and hydrophobic fumed silica in this invention, all can use the commercial item which satisfy | fills said conditions.

  The ratio of the clay mineral to fumed silica added to sodium hydrogen carbonate is preferably 1 to 5% by mass of clay mineral and 0.5 to 2.0% by mass of fumed silica. If the ratio to add is below an upper limit, since sufficient physical property is obtained, it is preferable. If the ratio to add is more than a lower limit, since the pressure loss in a filter cloth will reduce and the discharge property from a silo will also improve, it is preferable.

The acidic component remover of the present invention preferably has an angle of repose of 40 to 60 °, a dispersity of 50 or less, and a jetability index of less than 90.
If the angle of repose is in the range of 40 to 60 °, it is possible to suppress the rathole phenomenon and the bridge phenomenon in the silo, thereby smoothing the supply of the acidic component removing agent in the removal device and increasing the acidic component removal efficiency. .
As the degree of dispersion increases, the powder scattering and jetting properties increase. When the dispersity is in the range of 50 or less, the jet property is in an appropriate range, and the increase in pressure loss of the bag filter and the leakage of particles from the filter cloth of the bag filter can be suppressed.
Further, the jet property index is an index for evaluating the jet property of the powder, and the higher this value, the higher the scattering property and the jet property. If the jet property index is less than 90, an increase in the pressure loss of the bag filter and the leakage of particles from the filter cloth of the bag filter can be suppressed.
Moreover, it is more preferable that the acidic component removing agent of the present invention has an angle of repose of 40 to 55 °, a dispersity of 15 to 50, and a jet property index of less than 90.

  An angle of repose is formed by powder when a powder sample is passed through a sieve having a diameter of 80 mm and an aperture of 710 μm while being vigorously dropped from a 160 mm-high funnel onto a table having a diameter of 80 mm. It is defined by measuring the angle formed between the generatrix of the cone and the horizontal plane, and the smaller the powder, the better the fluidity. Here, the amount of powder falling is assumed to drop until the angle of repose is substantially stabilized.

  The jetability index is a standard for numerically evaluating the jetability, and the index was obtained from Table 1 and Table 2 from the measured values of fluidity, collapse angle, difference angle, and dispersity, and each index was added up. It is defined as a numerical value, and it is evaluated that the larger the numerical value, the stronger the jet property. Hereinafter, the definition of each physical property will be described.

The fluidity is defined by a numerical value obtained by similarly obtaining an index from the measured values of the angle of repose, the degree of compression, the spatula angle, and the uniformity, and adding the indices. The angle of repose is obtained by the method described above.
The degree of compression is defined by {(curve specific gravity) − (slack specific gravity)} / (hard specific gravity) × 100. Here, the loose specific gravity is defined as the powder when the powder sample is passed through a sieve having a diameter of 80 mm and an opening of 710 μm while vibrating, and then the dropped powder is sliced into a 100 cm ³ container. The specific gravity is defined by measuring the mass of a volume of 100 cm ³ when a container containing powder is tapped at a pace of 180 times for 180 seconds. The The spatula angle is defined by measuring a tilt angle of a side surface when a metal spatula of 120 mm × 22 mm is leveled and powder is deposited thereon.
The uniformity is defined by a value obtained by measuring the particle size distribution and dividing the 60% particle size in the cumulative mass distribution (sieve) by the 10% particle size. Various methods are used for the particle size distribution depending on the particle size of the target powder, such as a sieving method, a laser diffraction scattering method, etc., but this time, measured values by the laser diffraction scattering method were adopted. Nikkiso Co., Ltd. “Microtrac FRA9220” was used for the measurement.
Decay angle is to measure the tilt angle of the cone formed by collapse by giving predetermined vibration three times to the cone made of powder formed for the purpose of measuring the angle of repose with a shocker attached to the measuring instrument. It is prescribed by.
The difference angle is defined by a value obtained by subtracting the value of the collapse angle from the angle of repose.

  The degree of dispersion was determined by dropping 10 g of a powder sample from a height of 61 cm onto a 10 cm diameter watch glass set so that the concave surface is on top, and the watch glass relative to the total mass of the dropped powder sample. It is defined as a 100-percentage of the mass of the powder sample scattered outside, and a powder having a larger value can generally be regarded as a powder having greater scattering properties and jet properties.

Further, the acidic component removing agent of the present invention has a tensile breaking force of the powder layer of 100 mN / cm ² or less, a pressure loss with respect to the filter cloth is 500 Pa or less, and a leakage concentration of the powder from the filter cloth is It is preferably 40 mg / Nm ³ or less. The more preferable range of the tensile breaking force of the powder layer is 80 mN / cm ² or less, the more preferable range of the pressure loss is 400 Pa or less, and the more preferable range of the leakage concentration of the powder is 20 mg / Nm ³ or less, especially It is 10 mg / Nm ³ or less.

The tensile breaking force of the powder layer is an indicator of the consolidation strength of the powder layer and the tendency to collapse. If the breaking force is small, the powder layer has a small consolidation strength and tends to collapse, and if the breaking force is large, the powder It can be considered that the layer has a large consolidation strength and is difficult to collapse. Therefore, if the tensile breaking force of the powder layer is in the above range, the filtration layer deposited on the surface of the filter cloth is unlikely to drop off, and the filter cloth is filtered when subjected to backwashing (reverse point). The layer can be easily removed from the filter cloth.
Moreover, if the pressure loss in the filter cloth is within the above range, the removal efficiency of the acidic component in the processing apparatus does not significantly decrease.
Furthermore, if the leakage density of the powder is in the above range, the burden on the living environment in the amount of discharged dust can be suppressed to a low level.

  In addition, the tensile breaking force of powder can be calculated | required by the measurement by a 2 division | segmentation cell method, for example using the suspension type powder layer adhesive force measuring apparatus (Koh Tester CT-2 type | mold) by Hosokawa Micron Corporation. Moreover, the leakability from the filter cloth and the state of the differential pressure can be obtained by, for example, measurement by a dust collection performance tester (Filter Media Tester) compliant with DIN (German Federal Standard established by German Standards Association).

Next, in the method for producing an acidic component removing agent of the present invention, sodium hydrogen carbonate, clay mineral, and fumed silica that are generally handled are mixed, and then the average particle size of the mixture is 3 to 20 μm. It is preferable to produce by pulverizing to the range.
When sodium hydrogen carbonate has a small particle size, the adhesion between the particles increases, so that it solidifies, and the fluidity of the powder deteriorates, resulting in poor handling. Further, fumed silica has strong cohesiveness, and it is difficult to uniformly mix fumed silica after pulverizing sodium bicarbonate to 3 to 20 μm. An acidic component remover with good handleability can be obtained, which is preferable. The acidic component removing agent of the present invention contains a plurality of components in addition to sodium hydrogen carbonate, but each component is weighed individually and mixed with sodium hydrogen carbonate, and each weighed component is mixed. Any method of measuring and mixing with sodium bicarbonate can be used without any problem.

It is preferable to use the sodium hydrogen carbonate raw material powder having an average particle size in the range of 50 to 350 μm.
There is no particular limitation on the particle size of the raw material powder of clay mineral, but it is preferable to use a material having an average particle size of 0.5 to 500 μm, which is an easily available range in consideration of efficient grinding. Those having an average particle size in the range of 0.5 to 70 μm are preferably used.
In particular, when talc is used as the clay mineral, it is desirable to use one having an average particle size of 20 μm or less.
In addition, when activated clay is used as the clay mineral, it is desirable to use one having an average particle size in the range of 10 to 500 μm, and more desirably, one having an average particle size of 70 μm or less.
Moreover, when using bentonite as a clay mineral, it is desirable to use a thing with the average particle diameter of the range of 10-100 micrometers, and it is more desirable to use a thing with an average particle diameter of 40 micrometers or less.
Further, when kaolin is used as the clay mineral, it is desirable to use a material having an average particle size in the range of 0.5 to 10 μm, and it is more desirable to use a material having an average particle size of 3 μm or less.
Further, the fumed silica raw material powder preferably has an average particle size in the range of 5 to 500 nm, more preferably in the range of 5 to 100 nm, and particularly preferably in the range of 5 to 20 nm. Here, the average particle diameter of fumed silica refers to the average particle diameter of primary particles.
By crushing the mixture of each raw material powder having an average particle size in the above range, an acidic component remover having an average particle size of 3 to 20 μm can be obtained, which is preferable.

  For the pulverization, it is preferable to use an impact pulverizer (a pulverizer using a blade rotating at high speed), a jet mill (a pulverizer using a collision airflow), a ball mill or the like. Use an impact pulverizer equipped with a wind classifier to classify the particles discharged from the pulverizer and return the coarse particles to the pulverizer again, while pulverizing the mixture of raw material powders with a high yield. It is more preferable because an acidic component remover having a particle size of 5 nm can be obtained. Further, when it is desired to obtain finer pulverized particles, it is preferable to use a jet mill. Jet mills require high power costs, but are suitable for pulverization as a pulverization method, and can remove an acidic component remover with a desired particle size in a high yield without removing coarse particles by sieving. preferable.

  The lower limit of the average particle size of the preferred acidic component remover after pulverization is not particularly limited in terms of the reaction with the acidic component, but when the average particle size approaches 1 μm, the tendency of the powder particles to adhere to each other increases. Even when clay minerals are used in combination, sufficient fluidity cannot be maintained, or a large amount of clay mineral needs to be added. Furthermore, for industrial production, the equipment and power costs required for grinding are excessive. Moreover, it is preferable to set the average particle diameter after pulverization to 3 to 20 μm together with the purpose of maintaining good reactivity with the acidic component to be removed.

  According to the acidic component removing agent of the present invention, high fluidity and low adhesion are well maintained by the addition of clay mineral and fumed silica, and the acidic component due to deterioration of silo discharge and poor dispersion in the flue Therefore, it is possible to significantly reduce the possibility of a decrease in reactivity with the filter and the occurrence of an increase in pressure loss in the filter cloth of the bag filter.

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 thereof include gases, combustion gases containing sulfur oxides and nitrogen oxides, and gases in which substances that show acidity as impurities in the production processes of various products are mixed.
As a method of removing the acidic component in the gas using the acidic component remover of the present invention, the acidic component remover of the present invention is dispersed and reacted in a gas containing the acidic component, and then captured by a bag filter or the like. The method of collecting is preferred. As equipment relating to dispersion in gas, for example, a method generally used in exhaust gas treatment equipment such as slaked lime as shown in FIG. 1 can be used. In this method, since the filtration layer of the acidic component removing agent is formed on the filter cloth surface of the bag filter, the acidic component can be efficiently removed. The temperature of the gas containing the acidic component is preferably higher than the acid dew point. When used for exhaust gas treatment of a garbage incinerator, a low temperature is preferable from the viewpoint of suppression of dioxin production, specifically 100 to 200 ° C is preferable, but 150 to 250 ° C is preferable from the viewpoint of removing acidic components. .

An acidic component remover composed of sodium hydrogen carbonate, clay mineral and fumed silica was produced and evaluated in various ways.
In addition, the raw material of each Example uses sodium hydrogen carbonate with an average particle diameter of 95 μm, talc with an average particle diameter of 11 μm, activated clay with an average particle diameter of 45 μm, kaolin with an average particle diameter of 1 μm, and bentonite with an average particle diameter of 16 μm. It was. Further, hydrophilic fumed silica and hydrophobic fumed silica having an average particle diameter of 0.02 μm were used.

The hydrophobicity of hydrophilic fumed silica and hydrophobic fumed silica was measured by a combustion type carbon content measuring apparatus (for example, CN analyzer (SUMIGRAP NC-80)). In the measurement procedure, helium and oxygen are flowed in the order of helium and oxygen, the temperature in the combustion furnace is raised to 800 ° C., and after the temperature rises, 20 to 30 mg of a measurement sample is weighed in a quartz cell and then put into the combustion furnace. Then, after burning for 1 minute in the furnace, the generated gas was measured with a CN analyzer, and the carbon ratio in the sample was determined. This carbon ratio is defined as the degree of hydrophobicity.
The hydrophobicity of the fumed silica used in the examples was 0% for hydrophilic fumed silica and about 1% for hydrophobic fumed silica.

  After mixing these raw material powders at a predetermined ratio, the powder discharged from the pulverizer is obtained by using an impact pulverizer (made by Hosokawa Micron Co., Ltd., trade name: ACM Pulverizer ACM-10A type) equipped with a wind classifier. By classifying and pulverizing the coarse particles again in the pulverizer, acidic component removers (Examples 1 to 15 and Comparative Examples 1 to 4) having an average particle diameter shown in Tables 3 to 5 were obtained.

Moreover, the acidic component removal agent of the comparative examples 5 and 6 of the average particle diameter shown in Table 5 was manufactured like the said Examples 1-15 except not mixing a clay mineral.
Further, in the same manner as in Examples 1 to 15 except that the clay component and the fumed silica were not mixed and the acidic component removing agent was composed only of sodium hydrogen carbonate, the average particle size of Comparative Example 7 shown in Table 5 was used. An acidic component remover was produced.

About the obtained acidic component removing agent, the tensile breaking force (mN / cm ² ) of the powder layer, the pressure loss (Pa) in the filter cloth, the leakage concentration of the drug from the filter cloth (mg / Nm ³ ), the angle of repose, The dispersity and the jetability index were measured. The results are shown in Tables 3-5.

Evaluation of improvement and practicality of powder physical properties are as follows: 1) physical properties related to fluidity, etc. 2) tensile breaking force of powder layer, 3) leakage concentration from filter cloth, 4) generation of pressure loss in filter cloth, It was carried out using the data measured for.
1) Physical property values (rest angle, dispersity, and jet property index) relating to fluidity were measured by the above-described method using a powder tester PT-D type manufactured by Hosokawa Micron Corporation.
2) The tensile rupture force of the powder layer was evaluated using the suspended powder layer adhesion measuring device (Koh Testa CT-2 type manufactured by Hosokawa Micron Corporation) using a two-divided cell as described above. . That is, about 20 (g) of the sample is filled in a two-divided cell in which two cylinders (inner diameter 50 (mm), height 20 (mm)) are stacked on the bottom, and the temperature is set at a pre-consolidation load 480 (Pa). The powder layer was compressed by applying pressure for 2 hours in an environment of 20 (° C.) and a relative humidity of 50 (%). One of the cells was pulled at a speed of 1 mm / min 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. Here, the standard of the powder layer breaking force (mN / cm ² ) (value obtained by dividing the tensile force by the cross-sectional area of the powder layer) was set to 100 or less.

In addition, 3) the leakage density of the powder from the filter cloth and 4) the pressure loss generated in the filter cloth were measured using a dust collection performance tester (Filter Media Tester) compliant with DIN. As test conditions, a glass fiber double woven filter cloth (manufactured by Unitika Ltd., WB992) was used as a test filter, a filtration area of 0.0154 (m ² ), a filtration rate (2.0 m / min), and a dust concentration (5 0.0 g / m ³ ), a pulse pressure of 0.5 (MPa), and a pulse jet of 1 (kPa) are set to be applied, and the operation of the test apparatus is continued for 6 hours, the operation is stopped, and the dust supply is stopped. Thereafter, 10 pulse jets were performed, and the pressure loss (residual pressure loss) measured thereafter was adopted.
Further, the leakage concentration from the filter cloth was calculated from the amount of drug captured by an absolute filter installed at the subsequent stage of the test filter and the amount of gas passing through. As a practical standard for the pressure loss generated in the filter cloth, the standard for the leak concentration was set to 500 (Pa) or less, and the standard for the leakage concentration was set to 40 (mg / Nm ³ ) or less.

As shown in Tables 3 to 5, regarding the addition effect of clay mineral, in Comparative Examples 5 and 6 in which the clay mineral was not added and only fumed silica was added, both the leak concentration was high and the angle of repose exceeded 50 degrees. The fluidity decreased a little, and for Comparative Example 6, the tensile breaking force exceeded 100 (mN / cm ² ).
On the other hand, as shown in Examples 1 to 15, it was confirmed that the addition of clay minerals improved both the differential pressure, the leakage concentration, and the fluidity.

In addition, as shown in Tables 3 to 5, with respect to the effect of adding fumed silica, in Comparative Example 7 in which fumed silica was not added and only clay mineral was added, the angle of repose indicating fluidity was remarkably deteriorated, and tensile fracture occurred. The force exceeded 100 (mN / cm ² ).
On the other hand, as shown in Examples 1 to 15, it was confirmed that the repose angle indicating fluidity was improved by adding fumed silica.

Moreover, also when the average particle diameter after grinding | pulverization is 18 micrometers, the tensile breaking force (mN / cm < ² >) is 37 and 46, and it has confirmed that dischargeability was favorable.

  From the above results, it can be seen that by using the acidic component remover of the present invention, a higher anti-caking effect than before can be obtained, and at the same time, pressure loss and leakage in the filter cloth can be suppressed.

FIG. 1 is a schematic view of a removal device that removes acidic components in exhaust gas using an acidic component remover. FIG. 2 is a schematic diagram for explaining a rathole phenomenon and a bridge phenomenon in the silo of the removing apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silo, 2 ... Exhaust gas flow path (flue), 3 ... Supply pipe, 4 ... Bag filter, 43 ... Filter cloth

Claims (4)

An acidic component removing agent for removing acidic components in exhaust gas, which contains sodium hydrogen carbonate, clay mineral, and fumed silica, and the content of clay mineral is 1 to 5% by mass, and fumed silica The content ratio of 0.5 to 2.0% by mass, the average particle size is in the range of 3 to 20 μm, and the fumed silica is composed of sodium hydrogencarbonate dispersed on the surface in the form of primary particles. Acidic component remover consisting of particles.   The acidic component remover according to claim 1, wherein the clay mineral is at least one selected from the group consisting of talc, activated clay, kaolin and bentonite. A method for producing an acidic component remover that removes acidic components in exhaust gas, wherein sodium bicarbonate, clay mineral, and fumed silica are mixed, and the clay mineral content is 1 to 5 mass%. And a fumed silica content of 0.5 to 2.0% by mass, the mixture is pulverized until the average particle size is in the range of 3 to 20 μm, and the fumes are placed on the surface of the sodium bicarbonate. A method for producing an acidic component remover in which dosilica is applied in the form of primary particles.   The method for producing an acidic component removing agent according to claim 3, wherein the clay mineral is at least one selected from the group consisting of talc, activated clay, kaolin and bentonite.

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