WO2012036012A1

WO2012036012A1 - Production method for acidic component remover, and method for removing acidic component in gas

Info

Publication number: WO2012036012A1
Application number: PCT/JP2011/070172
Authority: WO
Inventors: 桜井　茂; 高田　英樹; 松本　知子
Original assignee: 旭硝子株式会社
Priority date: 2010-09-16
Filing date: 2011-09-05
Publication date: 2012-03-22
Also published as: TW201217269A; JPWO2012036012A1; JP5799955B2

Abstract

Provided is a production method for an acidic component remover that suppresses the increase in pressure loss in a filter cloth of bag filter and the leakage of acidic component remover from the filter cloth, is less likely to cause emission trouble from a silo, is excellent in handling property, and can sufficiently suppress the omission of the filtration layer accumulated on the surface of the filter cloth. A method for producing powders of an acidic component remover, comprising: mixing powders of sodium bicarbonate (A) having a mean particle size of 50 μm or more, powders of hydrophobic fumed silica (B), and powders of colloidal calcium carbonate (C) having a mean particle size of 50 nm or less in the primary particles; and pulverizing the resultant mixture, wherein the mean particle size of the obtained acidic component remover is 3 to 20 μm, the proportion of the hydrophobic fumed silica (B) in the acidic component remover is 0.2 to 0.5 wt%, and the proportion of the colloidal calcium carbonate (C) in the acidic component remover is 1.5 to 2.5 wt%.

Description

Method for producing acidic component remover and method for removing acidic component in gas

The present invention relates to a method for producing an acidic component remover that removes acidic components in a gas, and a method for removing an acidic component in a gas using the acidic component remover obtained by the production method.

排ガス Acidic components such as hydrogen chloride and sulfur oxides are contained in the exhaust gas generated by incineration of general waste and industrial waste. As an apparatus for removing an acidic component, a removing apparatus using an acidic component remover is known.

FIG. 1 is a block diagram showing an example of an apparatus for removing acidic components in exhaust gas. The removal device includes a silo (storage facility) 1 for storing a powdery acidic component remover M, an exhaust gas passage 2 (flue) through which exhaust gas containing acidic components flows, and an acidic component remover for silo 1. Is constituted roughly by a supply pipe 3 for supplying the exhaust gas into the exhaust gas and a bag filter 4 arranged on the downstream side of the exhaust gas passage 2.

The discharge unit 1a of the silo 1 is provided with a powder quantitative supply device 5 such as a rotary valve or a table feeder. By operating the powder quantitative supply device 5, the acidic component removing agent M is dropped into the opening 3 a of the supply pipe 3.
An incinerator (not shown) for general waste, industrial waste, etc. is installed on the upstream side of the exhaust gas passage 2. In the exhaust gas flow path 2, exhaust gas containing acidic components such as hydrogen chloride, nitrogen oxide, and sulfur oxide from the incinerator circulates.
The supply pipe 3 delivers the acidic component removing agent M supplied from the opening 3a to the downstream side by a gas flow such as an air flow circulated from the upstream side. The downstream end of the supply pipe 3 is disposed in the exhaust gas flow path 2. At the downstream end of the supply pipe 3, an ejector 3b for ejecting the acidic component removing agent M into the exhaust gas is attached.

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, and an upper portion of the housing 41. And an exhaust port 44 provided in 41c.
The filter cloth 43 has a lower end closed and a hollow portion 43a inside.
The upper part 41c and the central part 41b of the housing 41 are partitioned by a partition plate 45, and the exhaust gas always passes through the filter cloth 43 when the exhaust gas moves from the central part 41b of the housing 41 to the upper part 41c. Yes.
The partition plate 45 is provided with a penetrating portion 45a, and a communicating tube 46 for connecting the hollow portion 43a of the filter cloth 43 and the upper portion 41c of the housing 41 is attached to the penetrating portion 45a.

Next, the operation of the apparatus for removing acidic components in the exhaust gas 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 is carried in the gas flow, sent to the downstream end, and ejected from the ejector 3b into the exhaust gas in the exhaust gas flow path 2.
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.

As an acidic component remover used in an apparatus for removing acidic components in exhaust gas, slaked lime has been used in the past, but in recent years, for example, the following has been proposed.
(1) An acidic component remover containing sodium hydrogen carbonate as a main component and having an average particle size of 50 μm or less, preferably 10 to 30 μm (Patent Document 1).

In order to efficiently remove the acidic component in the exhaust gas, it is necessary to make the average particle size of the acidic component remover as small as possible. However, the acidic component remover having an average particle size of 30 μm or less has poor fluidity, or the adhesion between particles becomes large and tends to solidify, which may cause difficulty in stable handling. As a result, there is a possibility that the removal efficiency of the acidic component is deteriorated.

That is, when the fluidity of the acidic component remover deteriorates and the adhesion between particles increases, the acidic component remover itself easily aggregates. For example, as shown in FIG. Or a bridge phenomenon occurs in the silo 1 as shown in FIG. As a result, the supply of the acidic component removing agent stagnate, and there is a risk that the acidic component removal efficiency in the removal device will be significantly reduced.

The following are proposed as acidic component removers with improved fluidity.
(2) An acidic component removing agent obtained by adding fumed silica as an anti-caking agent to sodium hydrogen carbonate (Patent Document 2).
(3) An acidic component remover obtained by adding a magnesium compound containing magnesium carbonate as an agglomeration inhibitor to sodium hydrogen carbonate (Patent Document 3).

However, when the fluidity of the acidic component remover is extremely improved, the acidic component remover particles easily enter the gaps between the fibers constituting the filter cloth of the bag filter, which may cause the following problems.
(I) The pressure loss in the filter cloth increases, the pressure difference of the exhaust gas between the inlet and the outlet of the bag filter (hereinafter referred to as differential pressure) increases, and the circulation amount of the exhaust gas decreases significantly.
(Ii) In order to restore the differential pressure of the filter cloth, the compressed air is flowed in the reverse direction of the flow of the exhaust gas, and the acid component remover particles are removed from the surface of the filter cloth and the fiber gap of the filter cloth ( Even if backwashing is performed, the pressure differential does not increase and does not recover.
(Iii) Particles of the acidic component removing agent pass through the filter cloth and are observed as dust in the exhaust gas.
(Iv) The filtration layer deposited on the surface of the filter cloth is easily peeled off from the filter cloth.

Any of the problems (i) to (iv) may lead to a reduction in the removal efficiency of acidic components in the removal apparatus.
Therefore, the following is proposed as an acidic component remover that suppresses the increase in pressure loss in the filter cloth of the bag filter, leakage of the acidic component remover from the filter cloth, and dropping of the filter layer deposited on the surface of the filter cloth. Has been.
(4) It contains sodium hydrogen carbonate, alkaline earth metal carbonate and fumed silica, the alkaline earth metal carbonate ratio is 1 to 5% by mass, and the fumed silica ratio is 0.00. An acidic component remover having an average particle diameter of 5 to 2.0% by mass and an average particle size of 3 to 20 μm (Patent Document 4).

JP 09-050765 Gazette JP 2000-218128 A Special table 2002-500553 gazette JP 2008-068251 A

In the acidic component removing agent (4), the tensile breaking force, which is an index of the ease of dropping off the filtration layer and the ease of discharging from the silo, is much smaller in magnesium carbonate than in calcium carbonate (patent Table 3 in Literature 4. Further, hydrophilic fumed silica tends to be smaller than hydrophobic fumed silica (paragraph [0022] and Table 3 of Patent Document 4).
Therefore, in an actual site, magnesium carbonate is suitably used as the alkaline earth metal carbonate, and hydrophilic fumed silica is suitably used as the fumed silica. However, even in the case of an acidic component remover obtained by adding magnesium carbonate and hydrophilic fumed silica to sodium hydrogen carbonate, the supply from the silo that temporarily stores the acidic component remover to the exhaust gas becomes unstable, The drop-off cannot be sufficiently suppressed, and further improvement is demanded.

The present invention suppresses an increase in pressure loss in the filter cloth of the bag filter and leakage of the acidic component remover from the filter cloth, and is less likely to cause a discharge trouble from the silo, has excellent handleability, and Provided is a method for producing an acidic component remover that can sufficiently suppress the filtration layer deposited on the surface, and a method for removing an acidic component in a gas using the acidic component remover obtained by the production method. That is, a new acidic component remover that is compatible with both problems related to the influence on the filter cloth and problems related to the stability of supply to the exhaust gas from the silo, the adhesion force of the powder layer, the wall friction force, the hopper inclination angle, Provided paying attention to each element of outlet diameter, breaking stress, residual pressure loss, and leakage concentration.

The method for producing an acidic component remover of the present invention comprises a sodium bicarbonate (A) powder having an average particle diameter of 50 μm or more, a hydrophobic fumed silica (B) powder, and an average particle diameter of primary particles. Is a method of producing a powder of acidic component remover by mixing and pulverizing powder of colloidal calcium carbonate (C) having a particle size of 50 nm or less. The resulting acidic component remover has an average particle size of 3 to 20 μm, acidic The content ratio of the hydrophobic fumed silica (B) in the component remover is 0.2 to 0.5% by mass, and the content ratio of the colloidal calcium carbonate (C) in the acidic component remover is 1.5. It is characterized by being -2.5 mass%.

The average particle size of the sodium hydrogencarbonate (A) before pulverization is preferably 50 to 300 μm. The average particle diameter of the primary particles of the hydrophobic fumed silica (B) is preferably 5 to 50 nm. Further, the BET specific surface area of the colloidal calcium carbonate (C) is preferably 30 m ² / g or more, and the boiled linseed oil absorption amount of the colloidal calcium carbonate (C) is preferably 50 mL / 100 g or more. .

In addition, it is preferable to obtain an acidic component remover having the average particle diameter by pulverizing with a pulverizing means equipped with a classifying means and classifying the pulverized product. More preferably, the powder exceeding the diameter is returned to the pulverizing means.
The pulverization is preferably performed by a pulverizing means selected from an impact pulverizer and a jet mill.

The present invention is also a method for removing an acidic component in a gas, wherein the acidic component removing agent obtained by the production method of the present invention is temporarily stored in a storage facility and then supplied into a gas containing an acidic component. In that case, it is preferable that the acidic component removing agent is discharged from the storage facility and supported on the gas flow, and the gas flow carrying the acidic component removing agent is supplied into the gas containing the acidic component.

According to the acidic component removing agent obtained by the production method of the present invention and the acidic component removing method in gas using the same, an increase in pressure loss in the filter cloth of the bag filter and leakage of the acidic component removing agent from the filter cloth In addition, it is difficult to cause a trouble of discharging from the silo, the handleability is excellent, and the filtration layer deposited on the surface of the filter cloth can be sufficiently prevented from falling off.

It is a block diagram which shows an example of the removal apparatus of the acidic component in waste gas. It is a figure explaining the rat hole phenomenon in the silo of the removal apparatus of FIG. It is a figure explaining the bridge phenomenon in the silo of the removal apparatus of FIG. It is a figure explaining a hopper inclination angle.

<Method for producing acidic component remover>
The method for producing an acidic component remover of the present invention comprises mixing sodium hydrogen carbonate (A) powder, hydrophobic fumed silica (B) powder, and colloidal calcium carbonate (C) powder, Manufacture by grinding. It is necessary that these three kinds of powders coexist for most of the period during which the pulverization is performed. Therefore, it is preferable to mix these three kinds of powders and supply the mixture to the pulverizer, or to supply these three kinds of powders to the pulverizer almost simultaneously to perform pulverization. In addition, in this specification, each powder before mixing is called raw material powder.

The method for producing the acidic component removing agent of the present invention is obtained by mixing raw material powders and supplying the mixture to a pulverizer or supplying each raw material powder to the pulverizer almost simultaneously for the following reason. A method of pulverizing the acidic component removing agent so that the average particle size is 3 to 20 μm is preferable.
(I) Hydrophobic fumed silica (B), which tends to agglomerate secondary by applying a strong shear stress to the powder during pulverization of the mixture, and colloidal carbonate having an average primary particle size of 50 nm or less Colloidal calcium carbonate in which the average particle size of hydrophobic fumed silica (B) and primary particles is 50 nm or less on the surface of particles of sodium hydrogen carbonate (A) which is efficiently crushed calcium (C) (C) can be uniformly applied in the state of primary and secondary particles.
(Ii) When the particle size of the pulverized sodium hydrogencarbonate (A) is small, the adhesion between the particles increases, so that the particles are solidified and the fluidity of the powder is deteriorated, which makes it difficult to handle. In addition, since hydrophobic fumed silica (B) has strong cohesiveness, sodium bicarbonate (A) is pulverized to 3 to 20 μm, and then hydrophobic fumed silica (B) is uniformly dispersed in the sodium bicarbonate (A). Mixing is difficult.

The acidic component removing agent obtained by the method of the present invention has fine particles of hydrophobic fumed silica (B) on the surface of sodium hydrogencarbonate (A) particles pulverized to have an average particle size of about 3 to 20 μm. It is considered to be composed of particles having a structure in which particles and fine particles of colloidal calcium carbonate (C) are attached. In pulverization, sodium bicarbonate (A) is pulverized, hydrophobic fumed silica (B) secondary particles are pulverized into primary particles and fine secondary particles, colloidal calcium carbonate (C) primary particles and fine particles Crushing into fine secondary particles, and fine particles (hydrophobic fumed silica (B) and colloidal calcium carbonate (C) primary particles and fine secondary particles on the surface of the pulverized sodium hydrogen carbonate (A) particles. It is considered that particles of the acidic component removing agent are generated by the adhesion of the secondary particles). The acidic component removing agent in the present invention is a powder and is considered to be composed of an aggregate of such particles.

As the pulverizing means, 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 is preferable. By using an impact pulverizer equipped with a wind classifier, the particles discharged from the pulverizer are classified, and the coarse particles are returned to the pulverizer again, while pulverizing the mixture of raw material powders. An acidic component removing agent having a target average particle diameter can be obtained. Further, when it is desired to obtain finer pulverized particles, it is preferable to use a jet mill. Jet mills are expensive in terms of power, but are suitable for pulverization as a pulverizing means, and can remove acidic particles with the desired average particle size in high yield without removing coarse particles by sieving. Can do.

(Sodium bicarbonate (A))
Sodium hydrogen carbonate (A) as a raw material powder is a powder composed of particles having an average particle diameter of 50 μm or more, and is usually preferably a powder composed of particles having an average particle diameter of 90 to 300 μm. Sodium hydrogen carbonate powder is usually produced industrially by a crystallization method. It is difficult to industrially efficiently obtain a raw material powder having an average particle size of less than 50 μm by crystallization, and such a raw material powder having a small average particle size has poor flowability and is difficult to handle. In addition, a raw material powder having an excessively large average particle size requires large energy for pulverization.
The average particle size of sodium bicarbonate (A), which is the raw material powder here, is measured with a measuring device using a standard sieve (manufactured by Seishin Enterprise Co., Ltd., automatic dry sieving measuring instrument robot shifter RPS-105). It is a thing.

(Hydrophobic fumed silica (B))
Hydrophobic fumed silica (B) used as a raw material powder is obtained by hydrophobizing the surface of fumed silica (hydrophilic fumed silica).
Fumed silica is a synthetic amorphous silica produced by a dry process. Specific examples include those produced by a combustion method, a self-combustion method, or a heating method.

Hydrophobing treatment includes silane treatment with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc., silane coupling agent treatment with vinyltrimethoxysilane, dimethylpolysiloxane treatment, methylhydrogenpolysiloxane treatment, fatty acid treatment, etc. Can be mentioned.

The hydrophobicity of the hydrophobic fumed silica (B) is preferably 0.8% or more and 5% or less. If the degree of hydrophobicity is less than 0.8%, the fluidization effect cannot be sufficiently obtained. When the degree of hydrophobicity exceeds 5%, the cohesiveness of the hydrophobic fumed silica (B) becomes strong on the contrary, and similarly, a sufficient effect cannot be obtained. Further, the hydrophobic fumed silica (B) can be arbitrarily selected from commercially available ones.
The degree of hydrophobicity of the hydrophobic fumed silica (B) is an index indicating the degree of adhesion of the hydrophobizing agent such as dimethylsilane adhering to the surface of the fumed silica. It is represented by the carbon content of B). The carbon content of the hydrophobic fumed silica (B) is measured by a combustion type carbon amount measuring device (such as SUMIGRAPH NC-80 (Sumitomo Chemical Analysis Center Co., Ltd.) or EMIA-110 (Horiba Seisakusho Co., Ltd.)). .

In the acidic component remover, it is preferable that most of the hydrophobic fumed silica (B) is uniformly dispersed on the surface of the sodium hydrogen carbonate particles in the form of primary particles. Since most of the hydrophobic fumed silica (B) is dispersed in the form of primary particles, the acidic component removing agent can be used as compared with the case where the hydrophobic fumed silica (B) is present in the form of secondary particles. The fluidity can be further moderated, and agglomeration due to aggregation can be suppressed. Therefore, the average particle diameter of the primary particles of hydrophobic fumed silica (B) used as the raw material powder is preferably 5 to 50 nm. When the average particle diameter of the primary particles of the hydrophobic fumed silica (B) is less than 5 nm, the cohesiveness is strong and it is difficult to disperse in the acidic component removing agent. When the average particle diameter of the primary particles of the hydrophobic fumed silica (B) exceeds 50 nm, a predetermined effect cannot be obtained. The primary particle | grains of hydrophobic fumed silica (B) here mean the minimum unit of the structure particle judged by visual observation of a SEM (scanning electron microscope) observation image. The average particle size of the primary particles of the hydrophobic fumed silica (B) is actually measured by SEM (scanning electron microscope). Specifically, the particle size of 100 primary particles is measured. , The arithmetic average of the measured values.

(Collate calcium carbonate (C))
Colloidal calcium carbonate (C) generally refers to precipitated calcium carbonate (synthetic calcium carbonate) called primary colloidal calcium carbonate or colloidal calcium carbonate having a primary particle size of 0.2 μm or less. In the present invention, this colloidal calcium carbonate (C) is used as a raw material powder.

The average particle diameter of primary particles of colloidal calcium carbonate (C) used as the raw material powder is 50 nm or less, and more preferably 30 nm or less. The primary particle of colloidal calcium carbonate (C) here refers to the minimum unit of constituent particles determined by visual observation of an SEM (scanning electron microscope) observation image. The average particle diameter of primary particles of colloidal calcium carbonate (C) is actually measured by SEM (scanning electron microscope). Specifically, the particle diameter of 100 primary particles is measured and measured. The value is an arithmetic average.

The BET specific surface area of the colloidal calcium carbonate (C) measured by the nitrogen adsorption method is preferably 30 m ² / g or more, and more preferably 40 m ² / g or more. The BET specific surface area is preferably 85 m ² / g or less.
The amount of boiled linseed oil absorbed by the colloidal calcium carbonate (C) is preferably 50 mL / 100 g or more. The amount of boiled linseed oil absorbed is preferably 100 mL / 100 g or less. The boiled linseed oil absorption amount of the colloidal calcium carbonate (C) here is measured according to JIS K 5101-13.

(Percentage)
The ratio (content ratio) of each component in the acidic component remover is substantially equal to the mixing ratio of each raw material powder used in the production. However, when there are components that have not been incorporated into the acidic component remover in the production of the acidic component remover, the mixing ratio of each raw material powder and the content ratio of each component in the acidic component remover may be different. For example, sodium hydrogen carbonate (A) that is not pulverized to a predetermined size and is not taken into the acidic component remover may be generated. The content ratio of each component in the acidic component remover can be calculated from the mixing ratio of each raw material powder by excluding the amount of the component that has not been incorporated into the acidic component remover. Moreover, the content rate of each component in an acidic component removal agent can also be determined by measuring the quantity of each component in the obtained acidic component removal agent.
The content of each component in the acidic component removing agent (100% by mass) is 0.2 to 0.5% by mass for hydrophobic fumed silica (B) and 1.5 to 2% for colloidal calcium carbonate (C). 5% by mass. The remainder is sodium bicarbonate (A), except where there is a small amount of additive. In the combination found in the present invention, if the content ratio of the hydrophobic fumed silica (B) is 0.2% by mass or more, the discharge from the silo is sufficiently improved, and if it is 0.5% by mass or less. No problems such as clogging of filter cloth occur. When the content ratio of the colloidal calcium carbonate (C) is less than 1.5% by mass, the rupture stress of the powder layer becomes large and a sufficient effect cannot be obtained. The effect obtained is not changed.

(Average particle size of acidic component remover)
The average particle size of the acidic component remover is 3 to 20 μm, preferably 5 to 10 μm. If the average particle size of the acidic component remover is 3 μm or more, sufficient fluidity can be obtained by using hydrophobic fumed silica (B) and colloidal calcium carbonate (C) in combination. Moreover, the problem that the particle diameter is too small to pass through the filter cloth can be avoided. If the average particle diameter of the acidic component remover is 20 μm or less, the acidic component in the exhaust gas can be efficiently removed.

The average particle diameter of the acidic component remover is an average particle diameter on a volume basis measured using a laser diffraction / scattering particle size distribution measuring apparatus (for example, Microtrack FRA9220 manufactured by Nikkiso Co., Ltd.). Hereinafter, when the average particle diameter is simply referred to, it means a value measured by this method using ethanol as a medium.

(Characteristics of acidic component remover)
The breaking stress of the powder layer of the acidic component remover is preferably 300 mN or less, and more preferably 250 mN or less. The breaking stress of the powder layer of the acidic component removing agent is an indicator of the consolidation strength of the powder layer inside the facility for temporarily storing a powder such as a silo and the ease of collapse. That is, if the breaking stress of the powder layer is 300 mN or less, the filtration layer deposited on the surface of the filter cloth is unlikely to fall off, and the filtration layer is subjected to backwashing (backwashing) on the filter cloth. Can be easily removed from the filter cloth, and the phenomenon of rat hole and bridge formation in the silo is less likely to occur, and the acidic component remover can be stably supplied. It is preferable that the breaking stress of the powder layer is small, but if it is too small, it is difficult to form a filtration layer on the surface of the filter cloth, and the function of removing acidic components in the exhaust gas is reduced or the chemical is wasted. Preferably it is.
The breaking stress of the powder layer of the acidic component removing agent can be obtained by measurement by a two-part cell method using a suspended powder layer adhesion measuring device (manufactured by Hosokawa Micron Corp., Kochi Tester CT-2 type).

As for the residual pressure loss in the filter cloth when using the acidic component remover, the numerical value obtained by the filter cloth residual pressure loss test method described later is preferably 150 Pa or less, more preferably 125 Pa or less, and 100 Pa or less. More preferably, If the residual pressure loss in the filter cloth is 150 Pa or less, the degree of penetration of the acid component remover particles into the gaps between the fibers constituting the filter cloth of the bag filter is small, and the bag filter can be stably operated for a long time. However, if the residual pressure loss is too small, it is difficult to form a filtration layer on the surface of the filter cloth, and the function of removing acidic components in the exhaust gas is reduced or the chemical is wasted.

Leakage concentration of the acidic component removal agent from the filter cloth is preferably from 15 mg / Nm ³ or less, 5 mg / Nm ³ or less is more preferable. Most preferably, there is no leakage of the acidic component remover from the filter cloth, but if the leakage concentration is 15 mg / Nm ³ or less, the burden on the living environment due to discharged dust can be suppressed to a low level.

Residual pressure drop in filter cloth and leakage concentration of acid component remover from filter cloth were established in 2007 in accordance with DIN (German Federal Standard established by German Standards Association) Dust Collection Performance Tester (Filter MediaTester) Further, it can be obtained by measurement with an apparatus conforming to JIS Z8909-1 (test method for dust collecting filter cloth).

(Method for removing acidic components in gas)
Gas containing an acidic component that can be treated with the acidic component remover obtained by the production method of the present invention includes hydrogen chloride from incinerators such as general waste (city waste), industrial waste, and medical waste, Exhaust gas containing hydrogen fluoride, sulfur oxide (sulfur dioxide), etc .; Exhaust gas containing sulfur oxide (sulfur dioxide, sulfur trioxide, sulfuric acid), nitrogen oxides, etc. from boilers; As impurities in the manufacturing process of various products Examples thereof include a gas in which an acidic substance is mixed as a component.

The temperature of the gas containing the acidic component is preferably higher than the dew point of the acid (the acid dew point is a temperature at which the acidic component is liquefied in combination with moisture in the exhaust gas). In the case of waste gas treatment in a garbage incinerator, a low temperature is preferable from the viewpoint of suppressing the production of dioxins, specifically 100 to 200 ° C. is preferable. Moreover, 150 to 250 ° C. is preferable from the viewpoint of the efficiency of removing acidic components and the viewpoint of heat recovery efficiency for effectively using the heat of the combustion exhaust gas.

As a method of removing an acidic component in a gas using the acidic component remover obtained by the production method of the present invention, the acidic component remover obtained by the production method of the present invention is contained in a gas containing an acidic component. A method of collecting and reacting with a bag filter or the like after supplying and dispersing in a flue gas from a silo or the like once stored, or placing an acidic component remover on the flue gas flow to form a filter cloth on the bag filter A method of reacting when exhaust gas passes through the filtered layer, or a combination thereof, is preferable. In general, an efficient combination method is generally employed.

In the method of discharging the acidic component remover from the storage facility for the acidic component remover such as silo, a commonly used rotary valve or table feeder can be used without any problem.

As the means for dispersing the acidic component removing agent in the gas, for example, an acidic component removing device in the exhaust gas as shown in FIG. 1 may be used. In this apparatus, since the filtration layer of the acidic component removing agent is formed on the surface of the filter cloth of the bag filter, the acidic component can be efficiently removed.

(Function and effect)
The acidic component remover obtained by the production method of the present invention described above contains hydrophobic fumed silica (B) and colloidal calcium carbonate (C), so that the fluidity of the acidic component remover is moderate. And agglomeration due to aggregation can be suppressed. Moreover, since it contains colloidal calcium carbonate (C), solidification of particles constituting the acidic component remover can be prevented. Thus, since it has moderate fluidity | liquidity and anti-caking ability, the rise of the pressure loss in a filter cloth can be suppressed, and the excessive fall of the filtration layer deposited on the surface of the filter cloth can be suppressed. In addition, it is possible to suppress a discharge trouble from the silo, and it is possible to suppress a decrease in reactivity between the acidic component in the exhaust gas and the acidic component remover due to poor supply to the exhaust gas or poor dispersion with respect to the exhaust gas.

In particular, in the acidic component removing agent obtained by the production method of the present invention, since hydrophobic fumed silica (B) and colloidal calcium carbonate (C) are combined, a conventional acidic component removing agent (carbonic acid) Compared to acidic component remover with magnesium carbonate and hydrophilic fumed silica added to sodium hydride, Patent Document 4), it is superior in all of the evaluation of adhesive force, wall friction angle, hopper inclination angle, outlet diameter, pressure loss in filter cloth , The dropout of the filtration layer deposited on the surface of the filter cloth can be sufficiently suppressed, and the discharge trouble from the silo can be suppressed in advance.
In Patent Document 4, it was considered that magnesium carbonate was superior to calcium carbonate and hydrophilic fumed silica was superior to hydrophobic fumed silica. However, in the present invention, hydrophobic fumed silica (B) and It turned out that the combination with the colloidal calcium carbonate (C) whose average particle diameter of a primary particle is 50 nm or less is the most excellent.
This is because the oil absorption amount of colloidal calcium carbonate (C) having an average primary particle size of 50 nm or less during mixing and pulverization operations is large, that is, the void ratio in the secondary particles is high, so that the primary particles are more This is thought to be due to being easily crushed. In addition, fumed silica is spherical and slippery, and is particularly effective as a fluidizing agent for hydrophobic fumed silica (B), but sometimes it tends to be “too effective”, such as clogging the eyes of a bag filter. However, primary particles of colloidal calcium carbonate (C) having an average primary particle diameter of 50 nm or less are irregular shapes such as cubes and spindles, and the same phenomenon is unlikely to occur. I think.

Examples are shown below, but the present invention is not limited to these examples.

(Hydrophobic degree of hydrophobic fumed silica)
The degree of hydrophobicity of the hydrophobic fumed silica was measured with a combustion type carbon content measuring device (CN analyzer (SUMIGRAPH NC-80)). Specifically, helium and oxygen are passed through the combustion furnace in this order, the temperature in the combustion furnace is raised to 800 ° C., and 20 to 30 mg of a measurement sample is weighed into a quartz cell and placed in the combustion furnace. After burning in the furnace for 1 minute, the generated gas was measured with a CN analyzer to determine the carbon content in the sample, and this was used as the degree of hydrophobicity.

<Shear test>
A shear test using a ring-shaped shear cell (Genique cell, inner diameter: 64 mm, made of stainless steel SUS316) was performed, and the adhesion force, wall friction angle, hopper inclination angle, and outlet diameter of the acidic component remover were as follows. I asked for it.

(Adhesive force)
The vertical load (W) and shear load (W1 to W3) used in the test were determined as shown in Table 1 according to the bulk specific gravity of the test powder. Pre-consolidation was performed by applying a vertical load to the upper lid of the lower fixed type shear cell packed with the acidic component removing agent, and the mixture was sheared to a steady value while the same vertical load was applied, followed by consolidation. Thereafter, according to Table 1, the shear stress was measured while applying a shear load, plotted to obtain a fracture envelope, and the adhesive force of the acidic component remover was determined from the intercept of the fracture envelope.

(Wall friction angle)
The vertical load (W) and shear load (W1 to W4) used in the test were determined as shown in Table 2 according to the bulk specific gravity of the test powder. Pre-consolidation by applying a vertical load to the top of a shearing cell made of stainless steel SUS316 and packed with an acidic component remover, and then measuring the shear stress while applying the shear load according to Table 2, and plotting The wall destruction envelope was obtained. The wall friction angle with the stainless steel SUS316 was obtained from the inclination of the wall fracture envelope.

(Hopper inclination angle)
Using the wall friction angle calculated from the measured value, the hopper inclination angle of the acidic component removing agent was obtained from the ff contour.

(Outlet diameter)
The vertical load in the adhesion test was set to level 1, and the same test was performed for levels 2 to 4 in Table 3 to obtain respective fracture envelopes. From these plots, the maximum principal stress and unconstrained fracture stress at each level were read, and a straight line FF was obtained as a flow function of the powder. Fc (unrestrained fracture stress) was obtained from the intersection of this FF and the straight line ff by the wall surface friction angle and the hopper inclination angle. Furthermore, the exit diameter was obtained from the following equation.
(Outlet diameter [cm]) = fc × (exit function) ÷ (bulk density of used powder)
The exit function here refers to a function determined by the hopper inclination angle and the shape of the hopper.

<Breaking stress test>
A breaking stress test was conducted using a suspended powder layer adhesion measuring device (manufactured by Hosokawa Micron Corporation, Kohitsta CT-2 type), and the breaking stress of the acidic component removing agent was determined as follows.

(Breaking stress)
About 20 g of the sample is filled into a two-part cell in which two cylinders (inner diameter: 50 mm, height: 20 mm) are stacked on the bottom, and the pre-consolidation load: 480 Pa, temperature: 20 ° C., relative humidity: 50%. Under pressure for 2 hours, the powder layer was compressed. One of the cells was pulled at a rate 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 breaking stress at the time of breaking the powder layer was measured.

<Filter cloth residual pressure drop test>
Residual pressure loss and leakage concentration were determined in the following manner using a dust collection performance test apparatus based on JIS Z8909-1 (test method for dust collection filter cloth).

(Residual pressure loss)
A glass fiber double woven filter cloth (manufactured by Unitika Ltd., WB992KR) is used as a test filter, filtration area: 0.0139 m ² , filtration speed: 2.0 m / min, dust concentration: 5.0 g / m ³ , pulse pressure : 0.5 MPa, filter cleaning execution pressure by pulse (= differential pressure of the filter during backwashing): 1,000 Pa, pulse operation time: 50 ms The operation was stopped, the dust supply was stopped, 10 pulse jets were performed, and the pressure loss measured thereafter was adopted as the residual pressure loss.

(Leakage concentration)
Furthermore, the leak concentration from the filter cloth was calculated from the amount of powder captured by an absolute filter installed at the subsequent stage of the test filter and the amount of passing gas.

(Raw material powder)
(A1): highly reactive slaked lime (average particle diameter by laser diffraction / scattering particle size distribution analyzer: 9 μm, BET specific surface area: 45 m ² / g).
(A2): Sodium hydrogen carbonate (average particle diameter by a sieving method using a standard sieve: 95 μm).
(B1): Hydrophobic fumed silica (average particle diameter of primary particles measured by SEM: 20 nm, degree of hydrophobicity: 1%).
(B2): Hydrophilic fumed silica (average particle diameter of primary particles measured by SEM: 20 nm, degree of hydrophobicity: 0%).
(C1): Basic magnesium carbonate (average particle diameter by a laser diffraction / scattering particle size distribution analyzer: 7 μm).
(C2): Colloidal calcium carbonate (average particle diameter of primary particles: 20 nm, BET specific surface area: 49 m ² / g, boiled linseed oil absorption: 85 mL / 100 g).
(C3): Colloidal calcium carbonate (average particle diameter of primary particles: 80 nm, BET specific surface area: 18 m ² / g, boiled linseed oil absorption: 25 mL / 100 g).

Comparative Examples 1-5, Examples 1 and 2
(Production of acidic component remover)
After mixing the raw material powder of sodium bicarbonate and the raw material powder of the anti-caking agent shown in Table 4 so that the proportion of the anti-caking agent in the acidic component removing agent becomes the ratio shown in Table 4, the wind power type Using an impact pulverizer equipped with a classifier (Hosokawa Micron, ACM Pulverizer ACM-10A type), the powder discharged from the pulverizer is classified, and coarse particles are pulverized while returning to the pulverizer to obtain an average. An acidic component remover with a particle size of 9 μm was obtained and compared with highly reactive slaked lime.
In addition, the average particle diameter of an acidic component removal agent is an average particle diameter in the volume reference | standard measured using the laser diffraction scattering type particle size distribution measuring apparatus (The Nikkiso Co., Ltd. make, Microtrac FRA9220). The same applies to Comparative Examples 6 to 12 and Examples 3 to 8 described later.

(Shear test)
The obtained acidic component remover was subjected to the shear test described above, and the adhesion force, wall friction angle, hopper inclination angle, and outlet diameter were determined. The results are shown in Table 4. The evaluations in the table indicate that ◎: excellent, ○: good, Δ: acceptable, and x: not possible.

Adhesive force is an index of mutual adhesive force between powders of the acidic component remover, and is preferably smaller.
The wall friction angle is an index of the mutual adhesive force between the acidic component removing agent and the container, and is preferably smaller.
The hopper inclination angle is an angle α of the silo bottom face inclination required for stable discharge of the powder from the silo described in FIG. 4, and a larger one is easier to handle.
The outlet diameter is the diameter of the silo outlet required for stable discharge of the acidic component remover from the silo, and is preferably smaller.
So far, more than the slaked lime that has been used so far, it has been difficult to obtain an acidic component remover with excellent fluidity in the silo, but the acidic component remover of Example 1 and in particular of Example 2, It can be seen that all the evaluation items show excellent results.

Comparative Examples 6-12, Examples 3-8
(Production of acidic component remover)
After mixing the sodium hydrogen carbonate raw material powder and the anti-caking agent raw material powder shown in Table 5 so that the proportion of the anti-caking agent in the acidic component remover becomes the ratio shown in Table 5, wind power By using an impact pulverizer equipped with a type classifier (Hosokawa Micron, ACM Pulverizer ACM-10A type), the powder discharged from the pulverizer is classified, and coarse particles are pulverized while returning to the pulverizer again. An acidic component remover having an average particle size of 9 μm was obtained.

(Breaking stress test, filter cloth residual pressure loss test)
The above-mentioned acidic component removing agent was subjected to the above-described breaking stress test and filter cloth residual pressure loss test, and the breaking stress, residual pressure loss, and leakage concentration were determined. The results are shown in Table 5.

The breaking stress reflects the ease of collapse of the powder layer during compaction, and is an indicator of the ease with which the filter layer deposited on the surface of the filter cloth can be removed and the ease of discharge from storage facilities such as silos. The smaller one is preferable.
It can be seen that the acidic component removers of Examples 3 to 8 show excellent results in all evaluation items.
In addition, although the comparative example 12 is the same composition as Example 13 in patent document 4, the value of a residual pressure loss differs. This is because, in Patent Document 4, the apparatus conforms to German standards, whereas in this specification, measurement is performed using an apparatus conforming to JIS standards.

(Supply from storage facilities and removal of acidic components)
The acidic component remover obtained in Example 4 was temporarily stored in a silo provided with an aeration nozzle (M-Technique, Fluidizer) as a powder fluidization measure, and discharged with a table feeder. When supply was carried out into the exhaust gas containing hydrogen chloride flowing through the flow shown, the acidic component removing agent was stably discharged from the silo, and hydrogen chloride was stably removed. In addition, stable operation was obtained without any problems with the bug filter.

Acidic component remover obtained by the production method of the present invention includes hydrogen chloride, sulfur dioxide, etc. in exhaust gas from refuse incinerators, sulfur dioxide, sulfur trioxide, sulfuric acid, etc. in exhaust gas from boilers, etc .; It is useful for removing acidic components in various gases.
The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2010-208383 filed on September 16, 2010 are cited herein as disclosure of the specification of the present invention. Incorporated.

1 silo (storage equipment)
2 Exhaust gas flow path 3 Supply pipe 4 Bag filter 43 Filter cloth

Claims

Sodium bicarbonate (A) powder having an average particle size of 50 μm or more, hydrophobic fumed silica (B) powder, and colloidal calcium carbonate (C) powder having an average primary particle size of 50 nm or less The powder is produced by mixing and pulverizing the body, and the average particle size of the obtained acidic component remover is 3 to 20 μm, and the hydrophobic fumed silica in the acidic component remover ( The content ratio of B) is 0.2 to 0.5 mass%, and the content ratio of the colloidal calcium carbonate (C) in the acidic component removing agent is 1.5 to 2.5 mass%. A method for producing an acidic component remover.
The method for producing an acidic component removing agent according to claim 1, wherein the average particle size of the sodium hydrogencarbonate (A) before pulverization is 50 to 300 µm.
The method for producing an acidic component removing agent according to claim 1 or 2, wherein an average particle size of primary particles of the hydrophobic fumed silica (B) is 5 to 50 nm.
The method for producing an acidic component removing agent according to any one of claims 1 to 3, wherein the colloidal calcium carbonate (C) has a BET specific surface area of 30 m 2 / g or more.
The method for producing an acidic component remover according to any one of claims 1 to 4, wherein the amount of boiled linseed oil absorbed by the colloidal calcium carbonate (C) is 50 mL / 100 g or more.
The method for producing an acidic component removing agent according to any one of claims 1 to 6, wherein the acidic component removing agent having the average particle diameter is obtained by pulverizing with a pulverizing unit including a classifying unit and classifying the pulverized product.
The method for producing an acidic component removing agent according to claim 6, wherein, in the pulverized product classified by the classifying means, the powder exceeding the average particle diameter is returned to the pulverizing means.
The method for producing an acidic component remover according to any one of claims 1 to 7, wherein pulverization is performed by a pulverizing means selected from an impact pulverizer and a jet mill.
A method for removing an acidic component in a gas, wherein the acidic component removing agent obtained by the production method according to any one of claims 1 to 8 is temporarily stored in a storage facility and then supplied into a gas containing an acidic component.
The acidic component removing method according to claim 9, wherein the acidic component removing agent is discharged from the storage facility and supported in a gas flow, and the gas flow carrying the acidic component removing agent is supplied into a gas containing the acidic component.