JP2001300251A - Device for cleaning foul gas and cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for cleaning a foul gas which securely maintains a high removing performance of a pollutant such as an exhaust gas by making treatment conditions suitable for the purpose and reducing the degree or contamination in soil or underground water by efficiently converting a nitrogen component to a nitrogen gas as well as a cleaning method using the device. SOLUTION: This cleaning device has a layer filled with an adsorbent which adsorbs and removes the injurious substance of the foul gas as a device for cleaning the foul gas. The device comprises a filled layer for blowing the foul gas thereinto through a blowing means, a filled layer for adsorbing/removing hydrocarbons which adsorbs/removes hydrocarbon pollutans contained in the foul gas, including soil, and the like, and a filled layer for adsorbing a nitrogen oxide which adsorbs the nitrogen oxide contained in the foul gas formed sequentially on the filled layer for the foul gas to be blown into, a water spray means which sprays water to the surface of the filled layer for adsorbing the nitrogen oxide and a filled layer for removing the nitrogen oxide which is formed at the lower part of the filled layer for the foul gas to be blown into and decomposes/removes the nitrogen oxide absorbed into water, including the soil, and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for purifying polluted gas, and more particularly to a method for purifying air polluted by automobile exhaust gas or combustion exhaust gas containing nitrogen oxides and hydrocarbons. The present invention relates to an apparatus and a method for purifying a contaminated gas.

[0002]

2. Description of the Related Art Nitrogen oxides contained in automobile exhaust gas,
Hydrocarbons, suspended dust and the like are required as countermeasures for air pollution. Conventionally, as a method for removing malodorous substances such as ammonia and sulfur oxides, a method utilizing microorganisms living in soil or compost has been frequently used.In recent years, a method for removing malodorous substances utilizing this microorganism has been used. Attempts have been made to apply it to automotive exhaust. For example, Japanese Unexamined Patent Publication No. Hei 10-128043 discloses a method of purifying automobile exhaust gas in which harmful components in automobile exhaust gas are adsorbed to soil particles containing a certain percentage of fine gravel and activated carbon and decomposed and removed by microorganisms in the soil. Has been proposed. However, some harmful substances in automobile exhaust gas, such as nitrogen oxides, hydrocarbons, and suspended dust, are biodegradable, while others are not. Furthermore, even if the soil has biodegradability, the characteristics of microorganisms involved in the degradation are various. For example, nitrogen oxides are reduced by denitrifying bacteria in an anaerobic state without oxygen and further in an environment in which a hydrogen donor such as an organic substance is present, and are released into the atmosphere as nitrogen gas. Hydrocarbons are removed by being decomposed into water and carbon dioxide by microorganisms in the presence of oxygen.
Therefore, depending on the environment where the microorganisms live, the purpose of removing harmful substances may not be achieved.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to achieve high removal performance by optimizing treatment conditions for various pollutants such as automobile exhaust gas and combustion exhaust gas. To provide a pollutant gas purifying apparatus and a purifying method capable of converting nitrogen components present in the form of nitric acid and nitrous acid into nitrogen gas at a high rate and reducing soil and groundwater pollution. is there.

[0004]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies and as a result, considered the characteristics of each of the harmful substances contained in automobile exhaust gas and combustion exhaust gas, and made it suitable for each harmful substance. It has been found that the above problems can be achieved by treating automobile exhaust gas and combustion exhaust gas by combining the above-described treatment conditions, and have reached the present invention. That is, the invention claimed in the present application is as follows.

(1) A pollutant gas purifying apparatus having a packed bed of an adsorbent for adsorbing and removing harmful substances in a polluted gas, wherein the packed bed for injecting the polluted gas through a blowing means. And a hydrocarbon adsorbing and removing packing layer formed in order on the contaminated gas injecting filling layer and adsorbing and removing hydrocarbon contaminants contained in the contaminant gas, including soil and / or compost, and the contaminant. A filling layer for adsorbing nitrogen oxides contained in a gas, a watering means for spraying water on the surface of the filling layer for adsorbing nitrogen oxides, and a lower part of the filling layer for blowing the contaminated gas. And a nitrogen oxide removal packed bed that decomposes and removes nitrogen oxides absorbed in the water, including soil and / or compost. (2) The contaminated gas purifying apparatus according to (1), wherein hydrophobic particles are mixed in the nitrogen oxide adsorption packed bed and the hydrocarbon adsorption removal packed bed. (3) The pollutant gas purifying apparatus according to (1) or (2), wherein a biodegradable plastic is mixed in the nitrogen oxide removing packed bed.

(4) When purifying the contaminated gas using the contaminated gas purifying apparatus according to any one of (1) to (3), the contaminated gas supplied to the contaminated gas injection packed bed by the blowing means. Are sequentially passed through a hydrocarbon adsorbing and removing packed bed and a nitrogen oxide adsorbing packed bed, and the hydrocarbon adsorbing and removing packed bed adsorbs and decomposes hydrocarbon-based pollutants in the polluted gas to form the nitrogen oxide adsorbent. The nitrogen oxides in the polluted gas are adsorbed by the packing layer for adsorbing, and a clean gas is released from the upper part of the packing layer for adsorbing nitrogen oxides to the outside of the system. Spray water with
Water passing through the nitrogen oxide adsorption packed bed and the hydrocarbon adsorption removal packed bed absorbs the nitrogen oxides contained in the contaminated gas and the nitrogen oxides adsorbed on each layer,
After reducing the absorbed nitrogen oxides by a nitrogen oxide removal packed bed provided below the polluted gas injection packed bed, the nitrogen oxides are discharged out of the system as wastewater. Purification method.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a polluted air purifying apparatus showing one embodiment of the present invention. In FIG. 1, this purifying apparatus includes a contaminated air blowing packed layer 1 into which contaminated air is blown through a blowing device 6, and a contaminated air formed on an upper portion of the contaminated gas blowing packed layer 1. Packing layer 2 for adsorbing and removing hydrocarbon pollutants contained in water and packing bed for NOx adsorbing nitrogen oxides contained in the polluted air (filling layer for adsorbing nitrogen oxides)
3, a water spray device 5 for spraying water on the surface of the NOx adsorption packed bed 3, and a NO for decomposing and removing nitrogen oxides dissolved in water formed below the contaminated air blowing packed bed 1.
x removing filling layer (nitrogen oxide removing filling layer) 4.

In such a configuration, the contaminated air is blown into the contaminated air blowing packed bed 1 through the blowing device 6, and the hydrocarbon adsorbed and removed packed bed 2 and the NOx
The hydrocarbon-based pollutants in the pollutant gas are adsorbed and decomposed when passing through the packed bed 2 for adsorption and removal of hydrocarbons, and pass through the packed bed 2 for adsorption of hydrocarbons. Nitrogen oxides in the contaminated gas are adsorbed, and clean air is released from the upper part of the nitrogen oxide adsorption packed bed 3 to the outside of the system. Examples of the polluted air include polluted air and combustion exhaust gas that are rich in exhaust gas containing nitrogen oxides, hydrocarbon compounds, suspended dust and the like in roadsides and in tunnels. As the blowing device 5, for example, an air collecting device or a blower is used. The contaminated air blowing filling layer 1 is filled with crushed stones and the like, and a contaminated air blowing pipe (not shown) is introduced to prevent the contaminated air blown into the inside thereof from drifting. In addition, the contaminated air blowing filling layer 1 is not limited to such a configuration, as long as the contaminated air can be blown uniformly over the entire surface of the hydrocarbon adsorption and removal filling layer 2 formed thereon. Good.

The soil and / or compost is filled in the packing layer 2 for removing and absorbing hydrocarbons, and the hydrocarbon-based pollutants in the contaminated air are captured and adsorbed on these soils and the like, and are further absorbed by the soils and the like. It is decomposed into water and carbon dioxide in the presence of oxygen by inhabiting hydrocarbon-degrading microorganisms.
As the soil, a natural soil such as Kuroboku soil or a mixed soil mainly containing this as a soil improving material such as perlite is used. As compost, for example, sewage sludge compost or the like is used.

It is preferable to mix hydrophobic particles in the soil and / or compost in a ratio of 5 to 50% by volume. By mixing the hydrophobic particles, the hydrocarbon contaminants in the contaminated air are more likely to be selectively adsorbed to the hydrophobic particles, and the trapping property of the hydrocarbon contaminants is higher than that of hydrophilic materials such as soil and compost. Significantly improved. In addition, air permeability is improved by mixing hydrophobic particles. As the hydrophobic particles, inorganic particles having a surface subjected to hydrophobic treatment, organic hydrophobic particles such as fluororesin, carbon particles, and the like can be used. Inorganic particles include, for example, silica, alumina, kaolin,
Talc, iron oxide, titanium oxide, zinc oxide and the like are used. Examples of the hydrophobic treatment method of the inorganic particles include, for example, a method in which the surface of the inorganic particles becomes hydrophobic by dehydration condensation accompanied by a dealcoholization reaction of metal alkoxide and metal alkoxide having a hydrophobic group. A method for introducing a group may be mentioned.

The NOx adsorbing packed bed 3 is filled with the above-mentioned soil and / or compost, and NOx (nitrogen oxide) and SOx (sulfur oxide) in contaminated air are adsorbed by these packings. And N as described later.
It is absorbed and dissolved in the water sprinkled on the surface of the Ox adsorption packed layer 3 and moves to the lower layer. Hydrophobic particles can be mixed with the soil and the like. By mixing the hydrophobic particles, the air permeability of the NOx adsorption packed layer 3 is improved. However, when the mixing ratio of the hydrophobic particles increases, the water retention capacity of the adsorption packed layer decreases, and the adsorbed NOx and the like are reduced. In order to reduce the amount of absorption in water, the mixing ratio of the hydrophobic particles is preferably about 3 to 30% by volume. The suspended particulate matter in the contaminated air is removed from the contaminated air by adsorption or filtration by particles in each of the hydrocarbon adsorbing and removing packed bed 2 and the NOx adsorbing packed bed 3. As a result, clean air from which contaminants have been removed is released into the atmosphere from the upper portion of the NOx adsorption packed bed 3.

On the other hand, water sprayed on the surface of the NOx adsorbing packed layer 3 by the water spray device 5 passes through the NOx adsorbing packed layer 3 and the hydrocarbon adsorbing and removing packed layer 2 and becomes water. Absorbs and dissolves NOx and the like adsorbed on the NOx adsorbing packed layer 3 when passing through, and further passes through the hydrocarbon adsorbing and removing packing layer 2 and the contaminated air blowing packed layer 1 below the NOx adsorbing packed layer 3 so as to absorb contaminated air. While absorbing and dissolving the NOx and the like contained in the NOx, and further reaches the NOx removal filling layer 4 below.
The NOx removal packed bed 4 is filled with soil and / or compost, and the NOx dissolved in the water
It is decomposed by denitrifying bacteria that inhabit the Ox removal filling layer 4. Since no air is supplied to the NOx removal packed bed 4 and an anaerobic state is maintained, NOx is easily reduced by denitrifying bacteria living in the soil and the like, and is converted to nitrogen gas with high efficiency. . In the case of reducing NOx by denitrifying bacteria, it is preferable to increase the mixing ratio of compost because an organic substance is required as a hydrogen donor. Further, hydrophobic particles may be mixed with the above soil and the like.

As the hydrogen donor, a biodegradable plastic which is gradually decomposed by microorganisms may be mixed with the NOx removal packed layer 4. As such a biodegradable plastic, synthetic polymers such as aliphatic polyester, polylactic acid, and polycaprolactone, and natural polymers such as starch are used. N biodegradable plastic
By mixing with the Ox removal filling layer 4, the biodegradable plastic is gradually biodegraded, so that the function as a hydrogen donor can be maintained for a long time. The NOx absorbed in the water as described above is efficiently converted into nitrogen gas by the NOx removal packed bed 4, so that the NOx
The NOx concentration of water discharged to the soil from the removal packed bed 4 can be kept low, and the pollution of soil and groundwater is significantly reduced.

[0014]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.
In addition, the measurement of the concentration of nitrogen oxides, hydrocarbons and suspended dust in the air was performed by a chemiluminescence measuring device, a gas chromatography measuring device, and a light scattering measuring device, respectively.
Further, the concentrations of nitrite ion and nitrate ion in the wastewater were measured by an ion chromatography measuring device.

Example 1 Purification processing of automobile exhaust gas was performed using the apparatus for purifying contaminated air shown in FIG. The bed for NOx adsorption, the bed for hydrocarbon adsorption removal and the bed for NOx removal contain black clay, compost, perlite and hydrophobic particles (hydrophobic silica with an organic functional group added to the particle surface). Each was filled in the mixing ratio shown in Table 1. In addition, the packed bed for injecting contaminated air was filled with crushed stone, and a contaminated air injecting pipe was introduced therein so that the contaminated air was dispersed and supplied into the purification device. 1 has a floor area of 1 m ² , the height of the packed bed for NOx adsorption is 0.18 m, the height of the packed bed for hydrocarbon adsorption and removal is 0.42 m, and the height of the packed bed for NOx removal is The height is 0.7 m. In addition, the exhaust gas treatment amount is 0.
Water was sprinkled from the upper part of the packed bed for NOx adsorption at 7 liters / day at 72 m ³ / min. The properties of the inlet air before the treatment and the outlet air after the treatment were examined, and the results are shown in Table 2. From Table 2, it can be seen that nitrogen oxides, hydrocarbons and suspended dust in the contaminated air are all removed at a high removal rate. Also, as a result of analyzing the nitrogen component of the wastewater flowing out from the lower part of the NOx removal packed bed, nitrite ions were found to be 11 mg /
1 and nitrate ion were 19 mg / l.

[0016]

[Table 1]

[0017]

[Table 2]

Example 2 The procedure of Example 1 was repeated except that the fillers in the bed for NOx adsorption, the bed for adsorption and removal of hydrocarbons and the bed for NOx removal had the mixing ratios shown in Table 3. Purification treatment of automobile exhaust gas was performed in the same manner as in Example 1. The properties of the inlet air before the treatment and the outlet air after the treatment were examined, and the results are shown in Table 4. From Table 4, it can be seen that nitrogen oxides, hydrocarbons and suspended dust in the contaminated air are all removed at a high removal rate. Further, as a result of analyzing the nitrogen component of the wastewater flowing out from the lower part of the packed bed for NOx removal, nitrite ion was 18 mg / l and nitrate ion was 25 mg / l.

[0019]

[Table 3]

[0020]

[Table 4]

Example 3 The procedure of Example 1 was repeated except that the packings for the NOx adsorbing packed bed, the hydrocarbon adsorbing and removing packed bed and the NOx removing packed bed were changed to the packings and the compounding ratios shown in Table 5. Purification treatment of automobile exhaust gas was performed in the same manner as in Example 1. Activated carbon was used as the hydrophobic fine particles, and aliphatic polyester-based polymer was used as the biodegradable plastic. The properties of the inlet air before the treatment and the outlet air after the treatment were examined, and the results are shown in Table 6. From Table 6, it can be seen that nitrogen oxides, hydrocarbons and suspended dust of the pollutant gas are all removed at a high removal rate. Also, as a result of analyzing the nitrogen component of the wastewater flowing out from the lower part of the packed bed for NOx removal, 13 mg / l of nitrite ions and 16 mg / liter of nitrate ions were analyzed.
l.

[0022]

[Table 5]

[0023]

[Table 6]

Comparative Example 1 Purification equipment having a floor area of 1 m ² and a layer height of 0.6 m was filled with black clay, compost and pearlite at the compounding ratio shown in Table 7 to purify contaminated air containing automobile exhaust gas. Processing was performed. The contaminated air was supplied so as to be dispersed inside the purification device via the contaminated air blowing pipe introduced into the contaminated air blowing packed bed filled with crushed stone at the lower part of the purification bed. Also N
7 l / day of water was sprinkled from the top of the packed bed for Ox adsorption. The results of the treatment are shown in Table 8, which showed that the removal rate of hydrocarbons in the contaminated air was significantly reduced. Also, as a result of analyzing the nitrogen component in the water flowing out from the lower part of the contaminated air purification layer, nitrite ion was 109 mg / l and nitrate ion was 2 mg / l.
It was 43 mg / l, indicating that the wastewater contained a large amount of nitrogen components, and soil and groundwater were easily contaminated.

[0025]

[Table 7]

[0026]

[Table 8]

[0027]

According to the purifying apparatus and the purifying method of the present invention, it is possible to optimize treatment conditions for various pollutants such as automobile exhaust gas and combustion exhaust gas, so that high removal performance can be ensured. Nitrogen components existing in the form of nitric acid, nitrous acid and the like can be converted into nitrogen gas at a high rate to reduce soil and groundwater contamination.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a polluted air purifying apparatus showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Packing layer for blowing contaminated air, 2 ... Packing layer for removing and adsorbing hydrocarbons, 3 ... Packing layer for adsorbing NOx, 4 ... Packing layer for removing NOx, 5 ... Sprinkler, 6 ... Blower.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C08K 3/00 C08L 101/16 F term (reference) 3G091 AA02 AB00 AB09 AB10 AB15 BA14 BA15 CA15 GB00Y HA07 4D002 AA12 AA33 AA34 BA03 BA04 BA06 BA14 BA17 CA01 CA07 DA47 DA58 DA70 EA03 EA07 4J002 CF031 CF181 CF191 DM006 FD206 GT00

Claims (4)

[Claims] An apparatus for purifying a pollutant gas having a packed layer of an adsorbent for adsorbing and removing harmful substances in the polluted gas, comprising: A hydrocarbon adsorbing and removing packing layer formed in order on the contaminated gas injecting filling layer and adsorbing and removing hydrocarbon contaminants contained in the contaminant gas, including soil and / or compost; and the contaminant gas A filling layer for adsorbing nitrogen oxides contained in, a watering means for spraying water on the surface of the filling layer for nitrogen oxide adsorption, and a lower part of the filling layer for blowing the contaminated gas. And a nitrogen oxide removing packed bed that decomposes and removes nitrogen oxides absorbed in the water, including soil and / or compost. 2. The pollutant gas purifying apparatus according to claim 1, wherein hydrophobic particles are mixed in the nitrogen oxide adsorption packed bed and the hydrocarbon adsorption removal packed bed. 3. The pollutant gas purifying apparatus according to claim 1, wherein a biodegradable plastic is mixed into the nitrogen oxide removing packed bed. 4. When purifying a pollutant gas using the pollutant gas purifier according to any one of claims 1 to 3, the pollutant gas supplied to the polluted gas injection packed bed by the blowing means is carbonized. Pass through the packed bed for hydrogen adsorption and removal and the packed bed for nitrogen oxide adsorption in order, and the hydrocarbon-based contaminants in the polluted gas are adsorbed and decomposed by the packed bed for hydrocarbon adsorption and removal,
The nitrogen oxide-absorbing packed bed absorbs nitrogen oxides in the polluted gas and releases a clean gas from the upper part of the nitrogen oxide-absorbing packed bed to the outside of the system. Water is sprayed on the surface of the substrate by water spraying means, and the water passing through the nitrogen oxide adsorption packed bed and the hydrocarbon adsorption removal packed bed contains nitrogen oxides contained in the contaminated gas and nitrogen adsorbed on each layer. After absorbing the oxides, the absorbed nitrogen oxides are reduced and removed by a nitrogen oxide removal packed bed provided below the contaminated gas injection packed bed,
A method for purifying pollutant gas, which is discharged outside the system as wastewater.