KR20220117529A - Waste Gas Treatment Apparatus For Volatile Organic Compounds Gas containing Nitrogen Compound - Google Patents

Abstract

The present invention relates to a waste gas treatment method including the steps of: introducing waste gas containing a nitrogen compound and volatile organic compound gas from a pollutant source; branching the waste gas into two or more gas streams including a first gas stream and a second gas stream; oxidizing the branched first stream; and denitrifying the branched second stream by joining the branched second stream with the oxidized first stream.

Description

Waste Gas Treatment Apparatus For Volatile Organic Compounds Gas containing Nitrogen Compound

The present invention is a device capable of simultaneously adsorbing waste gas of volatile organic compounds containing nitrogen compounds using a concentrator such as a rotary adsorption concentrator, and concentrating and desorbing adsorbed nitrogen compounds and volatile organic compounds to perform catalytic oxidation treatment. it's about

Nitrogen compounds and volatile organic compounds (VOCs), which are widely used as raw materials for petroleum products, paint solvents, and semiconductor cleaners, etc., when leaked into the air, increase the defective rate of products and cause corrosion of production facilities. As a method for simultaneously removing gases containing volatile organic compounds including nitrogen compounds, an adsorption filter using activated carbon is commonly used. Apart from that, periodic replacement is necessary. In addition, when nitrogen compounds are combusted using heat or catalysts, they are converted to nitrogen compounds (NOx) during combustion and cause secondary gas pollution. to be. Accordingly, there is a need for a technology for effectively treating a gas containing volatile organic compounds including various nitrogen compounds at the same time.

(1) KR 2015-116865 A (2) KR 1139575 B

In order to solve the problems of the prior art, an object of the present invention is to provide a waste gas treatment method and a treatment device capable of simultaneously oxidizing and denitrifying waste gas containing nitrogen compounds and volatile organic compounds.

In addition, an object of the present invention is to provide a method and apparatus for self-denitrifying a secondary product by using a part of the concentrated gas of nitrogen oxide (NOx) generated as a secondary product during catalytic oxidation of nitrogen compounds as a reducing agent.

introducing waste gas containing nitrogen compound and volatile organic compound gas from a pollutant source; branching the waste gas into two or more gas streams comprising a first gas stream and a second gas stream; oxidizing the branched first stream; and combining the branched second stream with the oxidized first stream to denitrate.

In the present invention, the oxidation step is preferably a catalytic oxidation method.

In addition, the nitrogen compound includes ammonia (NH ₃ ) or urea.

In the present invention, the nitrogen compound in the second stream acts as a reducing agent for NOx in the first gas stream.

In addition, the present invention, a distributor for introducing a waste gas containing a nitrogen compound and a volatile organic compound gas and branching it into at least two streams including a first gas stream and a second gas stream; an oxidizer receiving a first gas stream from the distributor to oxidize a waste gas in the first gas stream; and a selective catalytic oxidizer for reducing NOx in the exhaust gas stream discharged from the oxidizer, wherein the second gas stream branched from the distributor is supplied to the selective catalytic oxidizer downstream of the oxidizer A waste gas treatment device is provided.

In the present invention, the oxidizing group is preferably a catalytic oxidizing group.

The apparatus of the present invention may further include a heat exchanger for exchanging heat between the first gas stream entering the oxidizer and the exhaust gas stream of the oxidizer.

In addition, in the present invention, the distributor may be a proportional distributor for controlling the flow rates of the first stream and the second stream.

In addition, the apparatus of the present invention further comprises a sensor for characterizing the NOx concentration in the exhaust gas stream of the oxidizer, the flow rate of the distributor being controllable by the output of the sensor.

In addition, the apparatus of the present invention may further include a concentrator for concentrating the waste gas from the pollutant in front of the distributor.

According to the present invention, it is possible to provide a method and apparatus capable of simultaneously treating oxidation and denitrification of nitrogen compounds and volatile organic compounds waste gases. The present invention can provide a waste gas treatment method and apparatus for simultaneously reducing the concentration of pollutants and the concentration of NOx in exhaust gas by using a nitrogen compound as a pollutant as a reducing agent in the denitrification process. According to an embodiment of the present invention, a catalytic oxidation device and a selective catalytic reduction device are configured in two stages in series for simultaneous catalytic oxidation of a volatile organic compound containing a nitrogen compound, and the concentrated gas is supplied to each catalyst layer. As it has the above pathway, it directly oxidizes volatile organic compounds containing nitrogen compounds through one pathway. By using it, it is possible to provide a removal device that can completely catalytically oxidize and reduce volatile organic compounds containing nitrogen compounds at the same time.

1 is a flowchart illustrating a waste gas treatment method according to an embodiment of the present invention.
2 is a view schematically showing a waste gas treatment apparatus according to an embodiment of the present invention.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.

1 is a flowchart illustrating a waste gas treatment method according to an embodiment of the present invention.

Referring to FIG. 1 , a waste gas including nitrogen compounds and volatile organic compounds (VOCs) is introduced from a pollutant source (S110).

In the present invention, the nitrogen compound in the waste gas may include NH ₃ or urea (H2NCONH2) (or urea). In addition, the volatile organic compounds in the waste gas refer to liquid gaseous organic compounds that easily evaporate into the atmosphere due to high vapor pressure, such as benzene, toluene, ethylbenzene, xylene, acetaldehyde, acetylene, and 1,3-butadiene.

In the present invention, the concentration of the waste gas generated from the pollutant may vary. Additionally, when the concentration of the waste gas discharged from the pollutant is low, the method may further include the step of concentrating the waste gas to a high concentration (S120). In the present invention, the concentration of the waste gas may be performed by a concentration means such as a known rotary adsorption rotor.

Then, the waste gas from the pollutant source is branched into two or more gas streams (S130). A portion of the branched gas, for example, the first stream may be transferred to an oxidizer and oxidized (S150). Illustratively, the oxidizer may be an oxidizer such as a catalytic oxidizer (CO), a thermal oxidizer (RTO), a thermal catalytic oxidizer (RCO), or a combination thereof that removes polluting gas by combustion. Preferably, the oxidizer may be a catalytic oxidizer.

The oxidation process of the volatile organic compound in the waste gas generated in an oxidation apparatus such as a catalytic oxidation apparatus can be described by Formula 1 below.

(Formula 1)

On the other hand, ammonia, a type of nitrogen compound, undergoes a series of chemical reactions as shown in Chemical Formula 2 below in the oxidizing device to generate NOx, a secondary by-product.

(Formula 2)

2NH ₃ + 2O ₂ → N ₂ O + 2H ₂ O

2NH ₃ + 5/2O ₂ → 2NO + 3H ₂ O

4NH ₃ + 7O ₂ → 4NO ₂ + 6H ₂ O

Next, a denitration process for removing NOx in the waste gas generated in the oxidation device is performed (S170). In the present invention, the denitration process is performed by joining another branch gas, such as the second gas stream, in step S130. At this time, the nitrogen compound of the second gas stream acts as a reducing agent in the denitrification process. This series of denitrification processes can be described by the following formula (3).

(Formula 3)

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O

2N ₂ O + 4NH ₃ +O ₂ → 3N ₂ +6H ₂ O

6NO ₂ + 8NH ₃ → 7N ₂ +12H ₂ O

2 is a view schematically showing the configuration of a waste gas treatment apparatus according to an embodiment of the present invention.

Referring to FIG. 2 , polluting components or harmful components, that is, nitrogen compounds and volatile organic compounds, included in the waste gas flowing from the discharge source are adsorbed to the adsorption member of the concentrator 10 while passing through the concentrator 10 . The concentrator 10 may be, for example, a rotor-type adsorption concentrator capable of adjusting the rotational speed according to the concentration of contaminants in the inflowing waste gas. For example, the concentrator 10 may rotate at a rotation speed of 2 to 20 rph.

The adsorption member of the adsorption concentrator has a number of passages in the form of honeycomb, and one or more metals such as Fe, Ag, Ca, Sr, etc. It is preferable to have an exchanged adsorbent, and in this case, the SiO ₂ /Al ₂ O ₃ molar ratio of the zeolite is preferably 5 or less.

The volatile organic compound contained in the waste gas of the discharge source flows into the adsorption area of the concentrator 10 and is adsorbed by the adsorption member. As the rotor rotates, the adsorption member adsorbing the pollutants enters the desorption region and is desorbed by the desorption gas. At this time, the desorption gas is used with a flow rate lower than the flow rate of the adsorbed waste gas. Preferably, the flow rate of the desorption gas is 1/3 to 1/30 of the flow rate of the adsorption gas. A desorption means (not shown) such as a heater, a heating device such as microwave or plasma, or a vibration means such as an ultrasonic vibrator may be added to the concentrator 10 to facilitate desorption of contaminants from the adsorption member in the desorption region. can

As described above, the waste gas treatment apparatus of FIG. 2 describes a case in which the concentrator 10 is used, but the present invention is not limited thereto. It goes without saying that a concentrator may be unnecessary for the treatment of waste gas of high concentration pollutants discharged from the emission source, and in some cases, the waste gas treatment apparatus of the present invention may also be used for the treatment of waste gas of low concentration without going through the concentrator.

Referring back to FIG. 2 , the waste gas having a high concentration of pollutants is preferably introduced into the distributor 110 . The distributor 110 divides the introduced waste gas into at least two gas streams.

As shown, a first gas stream of the branch gas is supplied to the oxidizer 130 , and a second gas stream is supplied to the denitrator 150 . The distributor 110 is preferably a proportional distributor capable of controlling the flow rate ratio of the first gas stream and the second gas stream. For example, the waste gas treatment apparatus may control the ratio of the first gas stream and the second gas stream by monitoring the NOx concentration in the exhaust gas of the oxidizer 130 with the sensor S and then controlling the proportional distributor. For example, in the waste gas treatment apparatus, when the concentration of NOx in the waste gas discharged from the oxidizer increases, the proportional distributor increases the flow rate of the second gas stream, and when the concentration of NOx decreases, the proportional distributor decreases the flow rate of the second gas stream. can As another example, the distributor 110 may control the flow rates of the first and second gas streams according to the type and concentration of contaminants in the waste gas flowing into the distributor 110 . Of course, it goes without saying that the flow rate can be controlled by reflecting all of the types and concentrations of the oxidizer exhaust gas and the distributor inlet gas.

A first gas stream from the distributor enters an oxidizer 130, such as a catalytic oxidizer (CO). As shown, the first gas stream may pass through a heat exchanger 140 disposed in front of the oxidizer 130 . The heat exchanger 140 may use the exhaust gas of the oxidizer 130 as a heat source.

The oxidizer 130 may include a single catalytic oxidation type catalytic oxidizer for the simultaneous removal of volatile organic compounds containing nitrogen compounds. The catalytic oxidizer may be used in which an oxidation catalyst is coated on a support having a plurality of through-hole channels in the form of honeycomb or beads. The support may be formed of a material including alumina, magnesium oxide, or cordierite. As the oxidation catalyst, noble metals such as palladium and platinum or transition metals such as copper, manganese, iron, and nickel may be used.

The waste gas oxidized in the oxidizer 130 is supplied to the selective catalytic reducer 150 through a heat exchanger. The selective catalytic reducer 150 is composed of alumina (Al ₂ O ₃ ), titanium oxide (TiO ₂ ) as a main catalyst on a support in which a through-hole channel is formed in a honeycomb or bead form, and vanadium, tungsten, cerium, and manganese as auxiliary catalysts. , may have a structure in which two or more catalysts selected from the group consisting of copper are coated.

The selective catalytic reducing group may further include an oxidation catalyst. In this case, the selective catalytic reducer may be composed of a laminated honeycomb support, the upper support may have a stacked structure including a catalytic reduction layer coated with a reduction catalyst, and the lower support may include a catalytic oxidation layer coated with an oxidation catalyst. When the selective catalytic reducing group includes a catalytic oxidation layer, it can act as a two-stage reactor for treating residual VOCs in addition to the reduction effect by the SCR catalyst.

A second gas stream branched from the distributor 110 is introduced into the selective catalytic reducer 150 . The second gas stream contains nitrogen compounds in the waste gas, and these nitrogen compounds act as a reducing agent for NOx in the first gas stream that has passed through the oxidizer 130 . Of course, if necessary, the selective catalytic reducer may be additionally supplied with a separate reducing agent.

The waste gas discharged from the selective catalytic reducer 150 is discharged into the atmosphere.

Of course, in the present invention, the oxidizer 130 may further include an LEL sensor for controlling the upper concentration limit for safe operation at the front end to control the flow rate of the distributor.

Hereinafter, preferred embodiments of the present invention will be described.

<Example>

As for the rotary adsorption rotor, a support body having a thickness of 400 mm and a diameter of 500 mm was prepared by rolling a honeycomb-structured polarized molded body into a circle, and a synthetic zeolite was coated to prepare an adsorption rotor. As exhaust gas, IPA (isopropyl alcohol) containing ammonia, toluene, and MEK (methyl ethyl ketone) were selected and evaluated as in Experimental Examples 1, 2, and 3.

Table 1 below summarizes the types and concentrations of gases desorbed from the rotary adsorption rotor.

division mixed gas Desorption concentration (O') One ammonia 300 ppm IPA 300 ppm 2 ammonia 310 ppm Toluene 266 ppm 3 ammonia 310 ppm MEK 304 ppm

Table 2 is a table showing the removal rate, NOx generation rate, and NOx removal rate for the gases before and after each catalyst layer using the mixed gas presented in Table 1 as the evaluation conditions of Experimental Examples 1, 2, and 3.

division Desorption gas distribution ratio (path) gas type Catalyst layer rear end removal rate (%) NOx production rate (%) Experimental Example 1 VOCs oxidation catalyst 70%
(A) NH3 100 - IPA 99.7 - NOx - 38.0 Selective Catalytic Reduction 30%
(B) NH3 100 - IPA 98.0 - NOx 98.7 - Experimental Example 2 VOCs oxidation catalyst 85%
(A) NH3 100 - Toluene 100 - NOx - 14.2 Selective reduction catalyst 15%
(B) NH3 100 - Toluene 100 - NOx 99.7 - Experimental Example 3 VOCs oxidation catalyst 92.5%
(A) NH3 100 - MEK 100 - NOx - 6.5 Selective reduction catalyst 7.5%
(B) NH3 100 - MEK 98.0 - NOx 98.1 -

The desorbed gas is distributed and injected at a certain ratio to the VOC oxidation catalyst device and the selective catalytic reduction device through the A and B paths as shown in [Table 2].

In Table 2, in the catalytic oxidation of IPA, toluene, and MEK used in Examples 1, 2, and 3, VOC gas is oxidized while passing through the oxidation catalyst layer as shown in Equation 1) to produce and remove CO ₂ , H ₂ O harmless to the human body. do.

IPA combustion reaction equation

(Formula 4)

C ₃ H ₈ O + 4.5O ₂ → 3CO ₂ + 4H ₂ O

Toluene combustion reaction equation

(Formula 5)

C ₇ H ₈ + 9O ₂ → 7CO ₂ + 4H ₂ O

MEK combustion reaction equation

(Formula 6)

C ₄ H ₈ O + 5.5O ₂ → 4CO ₂ + 4H ₂ O

In Table 2, the removal rate at the rear end of the catalyst layer is expressed as a percentage obtained by dividing the concentration at the front of the catalyst and the concentration at the rear. The nitrogen oxide (NOx) production rate refers to the production rate at which ammonia is oxidized while passing through the oxidation catalyst layer as shown in Formula 2, and NOx, a secondary by-product, is produced, and the value obtained by dividing the ammonia concentration at the front of the catalyst and the generated NOx concentration is expressed as a percentage. .

As in Examples 1, 2, and 3 of Table 2, when the desorbed gas is distributed in a certain ratio and put in front of the selective reduction catalyst, as shown in Chemical Formula 7, NH ₃ serves as a reducing agent and NOx can be completely treated.

(Formula 7)

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O

2N ₂ O + 4NH ₃ +O ₂ → 3N ₂ +6H ₂ O

6NO ₂ + 8NH ₃ → 7N ₂ +12H ₂ O

<Experimental Example 1>

Ammonia and IPA were mixed and the concentrated gas was uniformly distributed and input in a ratio of A passage: B passage = 7: 3 to proceed with evaluation.

<Experimental Example 2>

Ammonia and toluene were mixed and the concentrated gas was uniformly distributed and input in a ratio of A passage: B passage = 8.5: 1.5, and evaluation was carried out.

<Experimental Example 3>

Ammonia and MEK were mixed and the concentrated gas was uniformly distributed and input in a ratio of A passage: B passage = 9.25: 0.75 to proceed with evaluation.

110 divider
130 oxidizer
140 heat exchanger
150 reducer

Claims (10)

introducing waste gas containing nitrogen compound and volatile organic compound gas from a pollutant source;
branching the waste gas into two or more gas streams comprising a first gas stream and a second gas stream;
oxidizing the branched first stream; and
and denitrifying the branched second stream by joining the oxidized first stream. According to claim 1,
The oxidation step is a waste gas treatment method, characterized in that the catalytic oxidation method. According to claim 1,
The nitrogen compound is ammonia (NH ₃ ) Waste gas treatment method, characterized in that it comprises urea. According to claim 1,
and the nitrogenous compounds in the second stream act as a reducing agent for NOx in the first gas stream. a distributor for receiving a waste gas comprising nitrogenous compound and volatile organic compound gas and branching it into at least two streams comprising a first gas stream and a second gas stream;
an oxidizer receiving a first gas stream from the distributor to oxidize a waste gas in the first gas stream; and
a selective catalytic oxidizer for reducing NOx in the exhaust gas stream exiting the oxidizer;
The waste gas treatment apparatus according to claim 1, wherein the second gas stream branched from the distributor is supplied to the selective catalytic oxidizer after the oxidizer. According to claim 1,
The oxidizer is a waste gas processing apparatus, characterized in that the catalytic oxidizer. According to claim 1,
and a heat exchanger for exchanging heat between the first gas stream introduced into the oxidizer and the exhaust gas stream of the oxidizer. According to claim 1,
The distributor is a waste gas treatment apparatus, characterized in that the proportional distributor for controlling the flow rates of the first stream and the second stream. According to claim 1,
a sensor for specifying a NOx concentration in the exhaust gas stream of the oxidizer;
Waste gas treatment apparatus, characterized in that the flow rate of the distributor is controlled by the output of the sensor. According to claim 1,
Waste gas treatment apparatus, characterized in that it further comprises a concentrator for concentrating the waste gas from the pollutant in front of the distributor.

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