JP2002058958A - Treatment of exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of treatment for sufficiently removing organic chlorine compounds and/or NOx gas with SOx gas contained in exhaust gas. SOLUTION: The treatment method of the exhaust gas comprizes removing components to be removed in the exhaust gas W, by contacting the exhaust gas containing the specified gas concentration of sulfer dioxide (SO2) gas and organic chlorine compounds such as dioxins or the same, namely concentration in the range shown by hatched part in the figure, with media such as a carbonaceous adsorbent A. It is capable of removing SO2 gas and dioxins with high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment method and, more particularly, to an exhaust gas treatment method for removing components to be removed contained in exhaust gas.

[0002]

2. Description of the Related Art Conventionally, as a method of removing components to be removed contained in exhaust gas, a medium such as a carbonaceous adsorbent (material) or a catalyst is brought into contact with the exhaust gas to obtain SOx gas, NOx
Exhaust gas treatment methods for removing harmful components such as x gas, HCl gas, or organic chlorine compounds such as dioxins are widely used. In such an exhaust gas treatment method, it is generally known that there is a correlation between the removal rate of the component to be removed and the exhaust gas temperature. Specifically, as the temperature of the exhaust gas increases, the removal rate of the SOx gas decreases, while the removal rate of the NOx gas increases (ie, the Sx gas removal rate increases).
Ox gas and NOx gas are in a trade-off relationship)
Examples are given.

[0003]

The inventors of the present invention have studied the conventional exhaust gas treatment method, and have found that
When removing organic chlorine compounds such as dioxins and / or NOx gas together with SOx gas such as SO ₂ gas as components to be removed, the organic chlorine compounds and / or NOx gas depends on the SOx gas concentration regardless of the exhaust gas temperature. It has been found that the removal rate of NOx gas may not always be sufficiently increased. In this case, in order to increase the treatment efficiency of the exhaust gas, there is a tendency to use an exhaust gas treatment device having a different specification depending on the characteristics of the exhaust gas (concentration of the component to be removed, concentration ratio, etc.) or use a device of a different scale. there were. Alternatively, depending on the type of exhaust gas, there is a case where a device design specific to the exhaust gas is indispensable.

Accordingly, the present invention has been made in view of such circumstances, and it has been possible to sufficiently remove an organic chlorine compound and / or NOx gas together with SOx gas contained in exhaust gas, and to treat the exhaust gas. An object of the present invention is to provide an exhaust gas treatment method capable of sufficiently reducing the concentration of an organic chlorine compound and / or NOx gas in the exhaust gas while sufficiently reducing the concentration of the SOx gas in the exhaust gas.

[0005]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies and as a result, have found that SOx gas, NOx gas, and dioxins contained in exhaust gas such as sintering gas. Concentration of organic chlorine compounds in exhaust gas and NO
The inventors systematically found that there is a correlation between the x gas and the removal rate of the organic chlorine compound, and completed the present invention.

[0006] That is, the exhaust gas treatment method according to the present invention provides at least one of the components to be removed contained in the exhaust gas.
A method for removing Ox gas and an organic chlorine compound,
SOx gas having a concentration satisfying the relationship represented by the following formula (1): 100 ≦ X (1), and the following formula (2):

(Equation 3) An exhaust gas containing an organic chlorine compound having a concentration satisfying the following relationship is brought into contact with a medium having adsorption capacity or resolution for a component to be removed. Here, in the formula, X represents the concentration (ppm) of SOx gas in the exhaust gas, and Cd represents the concentration (ng-TEQ) of the organic chlorine compound in the exhaust gas.
/ M ³ (standard condition; the same applies hereinafter)).

In such an exhaust gas treatment method, the concentration of the organochlorine compound in the exhaust gas with respect to the concentration of the SOx gas represented by the above formula (1) is set to a value within the range represented by the above formula (2). Thereby, the desulfurization rate and the removal rate of the organic chlorine compound in the exhaust gas are sufficiently increased, and the SOx component and the organic chlorine compound can be almost completely removed and decomposed, respectively.

[0008] The "medium" used in the present invention is:
A substance having an adsorption capacity or a resolution with respect to the component to be removed contained in the exhaust gas is shown, and the form is not particularly limited. For example, a plurality of powdery or granular solid particles (specifically, carbon Adsorbent (material) particles, catalyst particles, etc.), and may be an aggregate or an aggregate of those solid particles, and the geometric or three-dimensional shape is not particularly limited. , Spherical, cylindrical, cylindrical, and the like.

The "dioxins" in the present invention
Mainly refers to polychlorinated dibenzoparadioxin (PC
DDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs)
s), and "TEQ" in the concentration unit indicates a toxicity equivalent conversion value.

Further, the exhaust gas treatment method according to the present invention is a method for removing at least SOx gas and NOx gas among components to be removed contained in exhaust gas, and the following formula (3): X ≦ 250 (3) SOx gas having a concentration satisfying the relationship represented by: and the following formula (4);

(Equation 4) An exhaust gas containing a NOx gas having a concentration satisfying the relationship represented by the following formula is brought into contact with a medium having an adsorption ability or a resolution for a component to be removed. Where:
X indicates the concentration (ppm) of SOx gas in the exhaust gas, and Cn
Indicates the concentration (ppm) of NOx gas in the exhaust gas.

In such an exhaust gas treatment method, the NOx gas with respect to the SOx gas concentration represented by the above formula (3) in the exhaust gas is defined as a value within the range represented by the above formula (4). In addition, the desulfurization rate and the denitration rate in the exhaust gas are sufficiently increased, so that the SOx component can be almost completely removed and the NOx component can also be removed with high efficiency.

Alternatively, the exhaust gas treatment method according to the present invention comprises:
At least SOx among the components to be removed contained in the exhaust gas
A method for removing a gas, an organic chlorine compound and a NOx gas, wherein the SOx gas having a concentration satisfying a relationship represented by the following formula (5): 100 ≦ X ≦ 250 (5); An exhaust gas containing an organic chlorine compound having a concentration satisfying the relationship represented by the following formula and a NOx gas having a concentration satisfying the relationship represented by the above formula (4) has an adsorption capacity or a resolution for a component to be removed. It may be one that comes into contact with the medium. Here, in the formula, X indicates the concentration (ppm) of the SOx gas in the exhaust gas.

In such an exhaust gas treatment method, the concentration of the organic chlorine compound and the concentration of the NOx gas with respect to the concentration of the SOx gas represented by the above formula (5) in the exhaust gas are represented by the above formulas (2) and (4), respectively. By defining the value within the range, the desulfurization rate in the exhaust gas, the decomposition rate of the organic chlorine compound and the denitration rate are sufficiently increased, and the SOx component and the organic chlorine compound can be almost completely removed and decomposed, respectively. In addition, NOx components can be removed with high efficiency.

Further, the exhaust gas coming into contact with the medium is represented by the above formulas (1) and (2), the above formulas (3) and (4), or the above formulas (2), (4) and (5). It is preferable to adjust the concentration of the component to be removed contained in the exhaust gas at the source of the exhaust gas so as to satisfy the following relationship.

[0015] In this way, the exhaust gas to be treated is treated together with the SOx gas together with the organochlorine compound and / or NOx.
It can be restricted to those having the above-mentioned concentration range suitable for high-efficiency processing of gas. Therefore, even for various exhaust gases having different concentrations of the components to be removed, high-efficiency treatment can be performed without changing the specifications and scale of the exhaust gas treatment apparatus.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted. Unless otherwise specified, the positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings.

FIG. 1 is a configuration diagram schematically showing an embodiment of an exhaust gas treatment apparatus for effectively implementing an exhaust gas treatment method according to the present invention. The exhaust gas treatment apparatus 100 includes a reaction tower 110 and a regeneration tower 120, and transfer machines 131 and 132 such as a conveyor are installed between them. The transfer devices 131 and 132 are arranged such that one end thereof is located below and above the reaction tower 110, respectively.
Further, the other end portions are arranged so as to be located above and below the regeneration tower 120, respectively. These transfer devices 131 and 132 are provided with a carbonaceous adsorbent (material) A as a medium.
Is circulated and transferred between the reaction tower 110 and the regeneration tower 120. Further, the reaction tower 110 and the regeneration tower 120
Is such that the carbonaceous adsorbent A is supplied from the upper end thereof, flows down the inside of each, and is discharged to the outside from the lower end.

The reaction tower 110 has an exhaust gas supply section 18 to which exhaust gas W such as a sintering gas is supplied to the side wall thereof, and
It has an exhaust gas discharge unit 20 from which the processed exhaust gas W is discharged. The exhaust gas W is desulfurized by the carbonaceous adsorbent A (SO 2) while flowing across the inside of the reaction tower 110.
₍₂ ) adsorption of SOx gas such as gas), adsorption of organic chlorine compounds such as dioxins, dust removal, etc., and treated gas Ws
Is sent from the exhaust gas discharge unit 20 to the stack (chimney) 140 and exhausted. The NOx contained in the exhaust gas W
When performing gas removal (denitration), together with exhaust gas W,
Alternatively, reduced nitrogen such as ammonia N is supplied to the reaction tower 110.

The carbonaceous adsorbent A having adsorbed the components to be removed in the exhaust gas W in the regeneration tower 120 is sent out to the regeneration tower 120 by the transfer device 131, and is heated in the regeneration tower 120 by heating.
Components to be removed such as x gas are desorbed, or organic chlorine compounds such as dioxins are decomposed. Thereby, the regeneration of the carbonaceous adsorbent A is performed. The gas component desorbed from the carbonaceous adsorbent A is discharged from the regeneration tower 120 as a desorbed gas, and is collected in an absorbent such as an alkali agent in the collection unit 150. The absorbent that has absorbed the desorbed gas components is neutralized
After being oxidized, it is sent to a recovery system (not shown) using, for example, gypsum or magnesium sulfate.

The exhaust gas W connected to the reaction tower 110
The sample supply unit S1 for measuring the concentration of SOx gas in the exhaust gas W, the sample collection unit S2 for measuring the concentration of NOx gas, and the concentration of dioxins in the supply pipe 30 Of the sample is connected.

In the exhaust gas treatment method according to the present invention,
The reaction tower 1 of the exhaust gas treatment device 100 thus configured
The exhaust gas W is supplied to the reaction tower 110 while circulating and transferring the carbonaceous adsorbent A between the reactor 10 and the regeneration tower 120. The exhaust gas W flows from the exhaust gas supply unit 18 into the reaction tower 110,
While passing across the inside of the reaction tower 110, it comes into contact with the carbonaceous adsorbent A. At this time, ammonia N is supplied to the reaction tower 110. Thus, the SOx gas, NOx gas and dioxins contained in the exhaust gas W are adsorbed by the carbonaceous adsorbent A. The exhaust gas W from which the components to be removed have been removed is discharged from the stack 140 as a treated gas Ws.

Further, the carbonaceous adsorbent A having adsorbed SOx gas or the like is transferred to the regeneration tower 120. In the regeneration tower 120, the carbonaceous adsorbent A is heated, retained, and cooled to desorb the adsorbed component from the carbonaceous adsorbent A or decompose the adsorbed component. As a result, the carbonaceous adsorbent A is regenerated, and the regenerated carbonaceous adsorbent A is returned to the reaction tower 110 after sieving based on the particle size.

Here, the following three types of exhaust gas W are used: (A) one that satisfies the relationship represented by the above formulas (1) and (2), (B) one that satisfies the above formulas (3) and (4) And (C) one satisfying the relationships represented by the above-described equations (2), (4) and (5).

Here, FIG. 2 is a graph showing the relationship between the concentration of SO ₂ gas in the exhaust gas W and the allowable concentration of dioxins in the exhaust gas W. This is a corresponding range, which is a range indicated by oblique lines in the figure. In FIG. 2, a curve L1 indicates the upper limit (allowable upper limit) of the concentration of dioxins as the organic chlorine compound in the formula (2).

According to such an exhaust gas treatment method, the dioxin concentration with respect to the SO ₂ gas concentration in the exhaust gas is
By defining the value within the range represented by the formulas (1) and (2) (the range shown by hatching in FIG. 2), the desulfurization rate and the removal rate of dioxins in the exhaust gas W can be sufficiently increased. Therefore, the SO ₂ component and dioxins can be almost completely removed and decomposed, respectively. Therefore, the concentration of SO _{2 and the} concentration of dioxins in the treated gas Ws can be simultaneously and sufficiently reduced.

As a specific example, an exhaust gas W containing about 200 (ppm) of SO ₂ gas and about 3.2 (ng-TEQ / m ³ ) or less of dioxins is used. 5-
8.5 mm) of carbonaceous adsorbent A, and when the carbonaceous adsorbent A adsorbing these components to be removed is heated and regenerated at a regeneration temperature of 400 ° C. in the regeneration tower 120, the desulfurization rate is about 100%. Approximately 99% of dioxin decomposition rate
It has been confirmed that can be achieved.

In other words, if the exhaust gas treatment is performed at the SOx concentration of the formula (1), the organic chlorine compounds such as dioxins are almost completely decomposed, but the dioxin reaches the upper limit concentration (curve L1) in the formula (2). It is acceptable to include these types. The details of the mechanism by which the high decomposition rate of dioxins is achieved in each concentration range of SO ₂ and dioxins are unknown, but organic chlorine compounds generally considered to act as an oxidizing agent by SOx gas. It is presumed that one factor is the improvement of the reaction kinetic parameters such as the equilibrium constants and activation energies of various elementary reactions in the decomposition reaction of water into lower hydrocarbons and water. However, the operation is not limited to this.

FIG. 3 is a graph showing the relationship between the concentration of SO ₂ gas in the exhaust gas W and the allowable concentration of NOx gas in the exhaust gas W. The range in which the method of the present invention is carried out (the range corresponding to the above (B)) (The range indicated by oblique lines in the figure). In FIG. 3, a curve L2 represents NOx in equation (4).
Indicates the upper limit (allowable upper limit) of the gas concentration.

According to such an exhaust gas treatment method, the ratio of the NOx gas concentration to the SO ₂ gas concentration in the exhaust gas is
By defining the values within the range represented by the formulas (3) and (4) (the range indicated by hatching in FIG. 3), the desulfurization rate and the denitration rate in the exhaust gas W can be sufficiently increased. Therefore, SO
_{The two} components can be removed almost completely, and the NOx component can also be removed with high efficiency. Therefore, SO ₂ in the treated gas Ws
The concentration and the NOx concentration can be reduced simultaneously and sufficiently.

As a specific example, an exhaust gas W containing about 200 (ppm) SO ₂ gas and about 145 (ppm) NOx gas
(Temperature 130 ° C.) with a particle size of 1 to 9 mm (average particle size 6.5).
(〜7.5 mm) of carbonaceous adsorbent A, it was confirmed that a desulfurization rate of about 100% and a desulfurization rate of about 40% could be achieved.

FIG. 4 shows the SO ₂ gas concentration in the exhaust gas W, the allowable concentration of dioxins in the exhaust gas W, and the N concentration in the exhaust gas W.
4 is a graph showing a relationship with the allowable concentration of Ox gas, showing a range in which the method of the present invention is performed (a range corresponding to the above (C), and two ranges indicated by oblique lines in the drawing). Note that the overlapping area of the two different hatched ranges is not necessarily the execution range of the present exhaust gas treatment operation. This is because the NOx gas concentration and the dioxin concentration are not uniquely determined, in other words, they are not necessarily correlated. Therefore, the scale of the two vertical axes in FIG. 4 may be arbitrary, and the apparent (looking) shape of the illustrated overlapping region differs depending on how to take the scale.

According to such an exhaust gas treatment method, the dioxin concentration and the NOx gas concentration with respect to the SO ₂ gas concentration in the exhaust gas are set to values within the range represented by the equations (2), (4) and (5). , The desulfurization rate in the exhaust gas W, the decomposition rate of dioxins, and the denitration rate can be sufficiently increased. Therefore, the SO ₂ component and dioxins can be almost completely removed and decomposed, and the NOx component can be removed with high efficiency. Therefore, the concentration of SO _{2, the} concentration of dioxins, and the concentration of NOx gas in the treated gas Ws can be simultaneously and sufficiently reduced.

As a specific example, an exhaust gas W (temperature: 130 ppm) containing about 200 (ppm) SO ₂ gas, about 3.2 (ng-TEQ / m ³ ) or less dioxins, and about 145 (ppm) NOx gas ° C) with a particle size of 1-9 mm (average particle size of 6.5-7.
5 mm) of carbonaceous adsorbent A, (a) a desulfurization rate of about 100%, a dioxin adsorption rate of about 95 to 97%, and a denitration rate of about 40% can be achieved;
(B) 4 carbonaceous adsorbents A adsorbing these components to be removed
When heated and regenerated at a regeneration temperature of 00 ° C., it was confirmed that the decomposition rate of dioxins could be at least 99%.

Further, as still another embodiment of the exhaust gas treatment method according to the present invention, the following method can be exemplified. In this method, in the supply pipe 30 of the exhaust gas treatment apparatus 100 shown in FIG. 1, the SOx gas and the NOx contained in the sample of the exhaust gas W sampled from the sampling units S1 to S3 of the exhaust gas W are used.
Analyze x gas and dioxins. Next, the concentrations of SOx gas, NOx gas and dioxins in the exhaust gas are calculated from the analysis values.

Next, the calculated values of these concentrations are defined by the above equations (1) and (2), the above equations (3) and (4), or the above equations (2), (4) and (5). A predetermined concentration range of each component (hereinafter, referred to as “predetermined concentration range”) is compared. Then, when the calculated concentration value is out of the predetermined concentration range, the concentration of the component contained in the exhaust gas W at the source of the exhaust gas W is set so that the concentration of the component in the exhaust gas W becomes a value within the predetermined concentration range. Control or adjust.

As a specific method of controlling or adjusting the concentration of the component in the source of the exhaust gas W as described above, for example, when the exhaust gas W is a sintering main exhaust gas, the following method can be mentioned. . That is, in order to control or adjust the concentration of SOx in the exhaust gas W, it is preferable to adjust the amount of coke or anthracite to be burned at the source of the exhaust gas W. According to the inventor's experience in manufacturing various actual devices, etc.,
The SOx component in the exhaust gas W mainly depends on the sulfur (S) content in the main combustion product. In addition, coke and anthracite are substantial main combustion products in the generation source, and the sulfur content contained in these has a significant difference, so that it is extremely effective for SOx component adjustment.

In order to control or adjust the concentration of organic chlorine compounds such as dioxins in the exhaust gas W, it is useful to adjust the amount of hydrocarbons (hydrocarbons) in the raw material for sintering. This is because the amount of hydrocarbons contained in the sintering raw material and the concentration of organic chlorine compounds such as dioxins generated by sintering are considered to have a substantially positive correlation.

Further, in order to control or adjust the NOx concentration in the exhaust gas W, it is desirable to adjust the amount of air per unit area of the sintering machine used. NOx in exhaust gas W
The concentration is generally considered to depend on the temperature of the sintering zone in sintering, and it is estimated that the temperature of the sintering zone is closely related to the amount of air supplied to the sintering machine.

According to such an exhaust gas treatment method, SO
The above concentration range suitable for high-efficiency treatment of not only x gas but also organic chlorine compounds and / or NOx gas (see FIGS. 2 to 4)
Is easily supplied to the reaction tower 110 easily. Therefore, even for various exhaust gases W having different concentration ratios of the components to be removed, high-efficiency processing can be performed without changing the specifications and scale of the exhaust gas processing apparatus 100. That is, there is an advantage that the versatility of the used exhaust gas treatment device 100 can be improved.

The reaction tower 110 constituting the exhaust gas treatment apparatus 100 is described in, for example,
The reactor described in 000-102719 may be used. Further, instead of the sampling sections S1 and S2 of the exhaust gas W sample, a SOx gas sensor such as gas chromatography and a NOx gas sensor may be provided, respectively. In this case, a control unit having an input interface connected to each sensor and a CPU connected to the input interface may be provided. This CPU, for example,
SOx gas and N output and input from each sensor
Based on the measurement signal of the Ox gas concentration, when these concentration values are out of the ranges defined by the above-described equations (2), (4) and (5), the fact is displayed on a display device, It is preferable to have a function of issuing an alarm.

Further, as a method of measuring dioxins in the exhaust gas W sample sampled by the sampling section S3, a manual of the Ministry of Health and Welfare (notified on February 26, 1997)
(Alternatively, Japanese Industrial Standard JIS K0312 (199
9)) can be used, and a high-resolution gas chromatograph / high-resolution mass spectrometer (HRGC / HRMS) can be used.
Quantitative analysis is possible.

[0042]

As described above, according to the exhaust gas treatment method of the present invention, the organic chlorine compound and / or NOx gas can be sufficiently removed together with the SOx gas contained in the exhaust gas, and the treated exhaust gas can be treated. While sufficiently reducing the SOx gas concentration in the exhaust gas, the organic chlorine compound and / or
Alternatively, the NOx gas concentration can be sufficiently reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an embodiment of an exhaust gas treatment apparatus for effectively implementing an exhaust gas treatment method according to the present invention.

FIG. 2 is a graph showing the relationship between the concentration of SO ₂ gas in exhaust gas W and the allowable concentration of dioxins in exhaust gas W.

FIG. 3 shows SO ₂ gas concentration in exhaust gas W and N in exhaust gas W
It is a graph which shows the relationship with the allowable concentration of Ox gas.

FIG. 4 is a graph showing the relationship between the concentration of SO ₂ gas in exhaust gas W, the allowable concentration of dioxins in exhaust gas W, and the allowable concentration of NOx gas in exhaust gas W;

[Explanation of symbols]

100: exhaust gas treatment device, 110: reaction tower, 120: regeneration tower, A: carbonaceous adsorbent (medium), W: exhaust gas.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/86

Claims (4)

[Claims] An exhaust gas treatment method for removing at least SOx gas and organochlorine compounds among components to be removed contained in exhaust gas, wherein the following formula (1); 100 ≦ X (1), X: the exhaust gas The SOx gas having a concentration satisfying a relationship represented by the concentration (ppm) of the SOx gas therein, and the following formula (2): Cd: concentration of the organic chlorine compound in the exhaust gas (ng-T
EQ / m ³ ), the exhaust gas containing the organochlorine compound having a concentration satisfying the relationship represented by the following formula: is brought into contact with a medium having an adsorption ability or a resolution for the component to be removed. Exhaust gas treatment method. 2. An exhaust gas treatment method for removing at least SOx gas and NOx gas among components to be removed contained in exhaust gas, wherein the following formula (3): X ≦ 250 (3) X: The SOx gas having a concentration satisfying a relationship expressed by the concentration (ppm) of the SOx gas, and the following formula (4): Cn: the exhaust gas containing the NOx gas having a concentration satisfying a relationship represented by the following expression: the concentration (ppm) of the NOx gas in the exhaust gas, is brought into contact with a medium having an adsorption capacity or a resolution for the component to be removed. An exhaust gas treatment method comprising: 3. An exhaust gas treatment method for removing at least SOx gas, organochlorine compound and NOx gas among components to be removed contained in exhaust gas, wherein the following formula (5): 100 ≦ X ≦ 250 (5) X: the concentration of SOx gas in the exhaust gas (ppm), the SOx gas having a concentration satisfying the relationship represented by the formula, the organic chlorine compound having a concentration satisfying the relationship represented by the above formula (2), and The exhaust gas containing the NOx gas having a concentration satisfying the relationship represented by the above formula (4),
An exhaust gas treatment method characterized by contacting with a medium having an adsorption capacity or a resolution for the component to be removed. 4. The exhaust gas which comes into contact with the medium is expressed by the formulas (1) and (2), the formulas (3) and (4), or the formulas (2), (4) and (5). The exhaust gas according to any one of claims 1 to 3, wherein a concentration of the component to be removed contained in the exhaust gas is adjusted at a source of the exhaust gas so as to satisfy a relationship expressed by the exhaust gas. Processing method.