KR20210106045A - The apparatus of multi-stage scrubber exhaust gas treatment and the method thereof - Google Patents

Abstract

The present invention relates to an exhaust gas treatment apparatus and method of a multi-stage scrubber, in which a scrubber is configured with two channels capable of individualizing solvent injection, so that a reducing agent and a neutralizing agent do not mix with each other, thereby using only 1.5 to 1.7 times the amount of the reducing agent compared to the theoretical amount in order to maintain the NO_x removal rate of 80% or more, and significantly reduce the generation amount of H_2S.

Description

Apparatus and method for treating exhaust gas of a multi-stage scrubber

The present invention relates to an exhaust gas treatment apparatus and method for a multi-stage scrubber, and more particularly, to a multi-stage scrubber exhaust gas treatment apparatus and method capable of suppressing the generation of hydrogen sulfide while reducing the amount of reducing agent used in the treatment of exhaust gas containing nitrogen dioxide it's about

In general, gases used in semiconductor, LED, and LCD manufacturing processes are very diverse, and F-gas such as NH3 or NF3 is used as a gas containing an N component.

Various gas components used in the manufacturing process in the electronics industry are treated by a scrubber device (pyrolysis, combustion, plasma method), and only harmless gases are finally discharged.

However, there are components that cannot be completely treated by this method and can be discharged. In the case of thermal decomposition, NOx in which oxygen and N components in the exhaust gas react, and in the case of combustion, NOx due to injection of oxidizing air, plasma In the case of corrosion protection, NOx by decomposition of NH3 or NF3 is not completely treated.

In order to treat such NOx, a wet scrubber device or the like is used to treat NOx. In the case of using the existing wet scrubber apparatus, a reducing agent is added to remove NOx, but there is a problem in that the generation of _{H 2 S according to the reducing agent is rapidly increased.}

1. Republic of Korea Patent No. 10-1300482 "Air pollutant treatment system and method using medium metal ions and reducing agents" 2. Republic of Korea Patent No. 10-1890165 "Scrubber device for reducing n2o contained in waste gas"

An object of the present invention is to solve the conventional problems as described above, and a multi-stage scrubber exhaust gas treatment apparatus and method capable of suppressing hydrogen sulfide generation by individually and sequentially applying a reducing agent and a neutralizing agent to an exhaust gas containing nitrogen dioxide aims to provide

In addition, by sequentially applying a reducing agent and a neutralizing agent to each channel of the scrubber, it is an object to provide an exhaust gas treatment apparatus and method of a multi-stage scrubber that can significantly reduce the amount of reducing agent while suppressing the generation of hydrogen sulfide.

Another object of the present invention is to provide an apparatus and method for treating exhaust gas of a multi-stage scrubber in which each channel through which a reducing agent and a neutralizing agent are injected is disposed in a transverse direction so that the solvent of each channel may not be mixed with each other.

The above object, according to the present invention, in the exhaust gas treatment apparatus of the multi-stage scrubber, the exhaust gas including NOx is introduced, the first channel through which the reducing agent is injected; and a second channel, located on the side of the first channel, through which the exhaust gas passing through the first channel is introduced, and through which the neutralizing agent is injected so as not to be mixed with the reducing agent. can be achieved.

Here, a gas analyzer for measuring the concentration _{of NOx and H 2} S of the exhaust gas discharged to the outside from the second channel; a first storage tank positioned under the first channel to store the reducing agent; a first water tank installed to supply the reducing agent to the first storage tank; ORP sensor for measuring the ORP of the reducing agent stored in the first storage tank; a second storage tank positioned below the second channel to store the neutralizing agent; a second water tank installed to supply the neutralizing agent to the second storage tank; a pH sensor for measuring the pH of the neutralizing agent stored in the second storage tank; And, calculates the NOx removal efficiency based on the measured value of the ORP sensor according to the NOx concentration of the gas analyzer _{, outputs the concentration of H 2} S based on the measured value of the pH sensor, and generates the set NOx removal rate reference value or the set H ₂ S It can be achieved by the exhaust gas treatment apparatus of the multi-stage scrubber comprising; a control unit for controlling the input timing and the input amount of the reducing agent and the neutralizing agent according to the reference value of the concentration.

In addition, when the calculated NOx removal rate is smaller than the set NOx removal rate, the control unit preferably controls to supply the reducing agent of the first water tank to the first channel to be greater than or equal to the set NOx removal rate.

Further, the control unit to the feed to the second channel the neutralizing agent in the second tank to fall, less than or equal to the concentration of the set H ₂ S, if greater the concentration of H ₂ S measured than the concentration of a predetermined H ₂ S It is desirable to control

In addition, it further includes an electric dust collecting unit installed at the rear end of the second channel including a discharge unit and a dust collecting unit to receive the exhaust gas treated in the second channel, and the dust collecting unit may be formed of a water film using the neutralizing agent. .

In addition, the reducing agent is sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium sulfite (Na ₂ SO ₃ ) mixed in a one-to-one ratio, and the neutralizing agent may be NaOH.

In addition, the reducing agent may be Na ₂ S, and the neutralizing agent may be NaOH.

The exhaust gas treatment method using the multi-stage scrubber exhaust gas treatment apparatus includes: removing nitrogen oxides by spraying a reducing agent into the exhaust gas including nitrogen dioxide flowing into a first channel; and, removing nitrogen oxides by spraying a neutralizing agent into the exhaust gas flowing into the second channel through the first channel, wherein the reducing agent controls the input timing and input amount according to the set NOx removal rate reference value, It is preferable to control the input timing and input amount of the neutralizing agent according to the set _{reference value of the H 2 S generation concentration.}

According to the present invention, there is provided an exhaust gas treatment apparatus and method of a multi-stage scrubber in which hydrogen sulfide can be remarkably reduced by individually and sequentially applying a reducing agent and a neutralizing agent to an exhaust gas containing nitrogen dioxide.

In addition, by sequentially applying a reducing agent and a neutralizing agent to each channel of the scrubber, an apparatus and method for treating exhaust gas of a multi-stage scrubber that can significantly reduce the amount of reducing agent while reducing the amount of hydrogen sulfide generated are provided.

In addition, there is provided an apparatus and method for treating exhaust gas of a multi-stage scrubber in which each channel through which a reducing agent and a neutralizing agent are injected is disposed in a transverse direction so that the solvent of each channel may not be mixed with each other.

1 is a schematic diagram of an exhaust gas treatment apparatus of a multi-stage scrubber according to a first embodiment of the present invention;
2 is a graph showing the relationship between the total amount of the reducing agent per minute and the mixing ratio of the reducing agent.

Prior to the description, in various embodiments, components having the same configuration are typically described in the first embodiment using the same reference numerals, and in other embodiments, configurations different from those of the first embodiment will be described. do.

Hereinafter, an exhaust gas treatment apparatus of a multi-stage scrubber according to a first embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of an exhaust gas treatment apparatus of a multi-stage scrubber according to a first embodiment of the present invention. 1, the exhaust gas treatment apparatus of the multi-stage scrubber according to the first embodiment of the present invention is a multi-stage scrubber including an ozone generator 10, a first channel 20 and a second channel 30, and an electric dust collector (40), is configured to include a gas analyzer 50 and a control unit (not shown).

The ozone generator 10 generates ozone (O ₃ ) by using a dielectric barrier discharge or the like, and the generated ozone (O ₃ ) is injected into the exhaust gas flowing into the multi-stage scrubber. When ozone (O ₃ ) is injected into the exhaust gas, NO, the main component of NOX, is oxidized to _{NO 2 as shown in the following chemical formula.}

(Formula 1) NO + O ₃ -----> NO ₂ + O ₂

That is, the exhaust gas is introduced into the multi-stage scrubber including _{nitrogen dioxide (NO 2 ).}

The multi-stage scrubber is configured to include a first channel 20 and a second channel 30 disposed in the transverse direction. Each channel is formed in the form of a long box in one direction, and spray nozzles 22 , 32 are installed on the inner upper side of each.

The multi-stage scrubber is configured to include a first channel 20 and a second channel 30 . First, the first channel 20 is formed with an inlet through which exhaust gas containing nitrogen dioxide is introduced from the side, and an outlet through which the exhaust gas is discharged through the second channel 30 is formed on the upper side.

The second channel 30 is formed with a communication port communicating with the outlet of the first channel 20 on the upper side, and the outlet port communicating with the electric dust collecting unit 40 is formed on the lower side.

The positions of the inlet, outlet and communication port may be changed according to the shape of the channel.

A first reservoir 21 in which a reducing agent is stored is provided below the first channel 20 , and the first spray nozzle 31 is connected to spray the neutralizing agent stored in the first reservoir 21 . With the same structure in the second channel 30 , a second reservoir 31 in which the neutralizing agent is stored is provided on the lower side of the second channel 30 , and the second spray nozzle 32 is stored in the second reservoir 31 . connected to spray the neutralizer.

The first storage tank 21 and the second storage tank 31 are connected to the first water tank 23 and the second water tank 33 provided separately and are installed to receive the solution.

_{Na 2} S as a reducing agent is stored in the first water tank 23 , and NaOH as a neutralizing agent is stored in the second water tank 33 .

In addition, an ORP sensor 23 for measuring ORP (Oxidation-Reduction Potential) of the reducing agent is installed in the first storage tank 21, and a pH sensor 24 for measuring the pH of the neutralizing agent in the second storage tank 31, etc. is installed

The ORP sensor 23 is a device for sensing the redox potential, and the pH sensor 24 is a device for measuring the concentration _{of H 2 S.} In addition, the measured values of the ORP sensor 23 and the pH sensor 24 are installed to be transmitted to the control unit.

The first nozzle 22 and the second nozzle 32 are installed to spray the reducing agent and the neutralizing agent provided at the upper side inside each channel. The reducing agent and the neutralizing agent are circulated between the respective nozzles and the storage tank through the pump, and their amounts are gradually decreased through the reaction with the exhaust gas, so a predetermined amount may be periodically supplied by the control unit to be described later through the corresponding water tank.

_{The gas analyzer 50 measures the NOx concentration and the H 2} S concentration of the exhaust gas that has passed through the electrostatic precipitation unit 40 to be described later, and the measured values are installed to be transmitted to the control unit.

The control unit (not shown) is provided to calculate the NOx removal rate by receiving the NOx _{concentration, the concentration of H 2} S provided from the gas analyzer 50, each provided from the pH sensor 34 and the ORP sensor 24 The measurement value is provided, and the input timing and input amount of the reducing agent or neutralizing agent stored in each tank can be controlled according to the preset NOx removal rate reference value or the preset H _{2 S generation concentration reference value.}

For example, when the calculated NOx removal rate is smaller than the set NOx removal rate, the control unit controls to supply the reducing agent of the first water tank 23 to the first channel 20 to be greater than or equal to the set NOx removal rate.

In addition, the control case increases the concentration of the predetermined H ₂ S a H ₂ S measured than the concentration of the neutralization agent in the second water tank 33 to become less than or equal to the concentration of a predetermined H ₂ S to the second channel 30 control to supply.

On the other hand, the control unit calculates the NOx removal rate through the measured value of the ORP sensor 24, and is provided to measure the concentration of _{H 2 S through the measured value of the pH sensor (34).}

The electrostatic precipitator 40 receives the exhaust gas from which NOx has been removed from the main chamber 20 and receives and discharges the dust collector chamber 41, the discharge unit 42 for discharging by high voltage discharge, and the discharged particles. It is configured to include a dust collecting unit 43 to collect.

Here, the dust collecting unit 43 is provided in a water film type that forms a water film inside the wall of the dust collecting unit chamber 41 by a neutralizing agent circulated by a pump. A specific configuration of the water film type dust collecting unit may be provided in the form disclosed in Korean Patent Registration No. 10-1173496 or No. 1967985 registered by the present applicant.

Since the dust collecting part 43 is composed of a water film formed by a neutralizing agent, it collects and treats acidic substances among the introduced exhaust gas particles.

Hereinafter, a method for removing nitrogen oxides from exhaust gas using the above-described apparatus for removing nitrogen oxides from exhaust gas will be described.

FIG. 2 is a flowchart of a method for removing nitrogen oxides from exhaust gas using the apparatus of FIG. 1 . Referring to FIG. 2 , in the method for removing nitrogen oxides from exhaust gas according to the present invention, ozone generated from the ozone generator 10 before the exhaust gas discharged from a process such as a semiconductor is introduced into the first channel 20 . is injected into the exhaust gas (S10).

The injected ozone reacts with nitrogen monoxide contained in the exhaust gas as shown in (Formula 1) above to generate nitrogen dioxide.

And, when the exhaust gas containing nitrogen dioxide is introduced into the first channel 20, and Na ₂ S as a reducing agent is injected from the first nozzle 22 installed in the first channel 20 (S20), the injected Na ₂ S reacts with nitrogen dioxide in the exhaust gas, respectively, according to the formula below.

(Formula 2) 2NO ₂ + Na ₂ S -----> N ₂ + Na ₂ SO ₄

At this time, when most of the reducing agent Na ₂ S is consumed, NO ₂ is _{not reduced to N 2} and nitric acid (HNO ₃ ) is generated by the reaction below.

(Formula 3) NO ₂ + H ₂ O -----> HNO ₃ + NO

Here, the first channel and an exhaust gas containing nitrogen dioxide flowing in the unit 20 to respond only Na ₂ S, Na ₂ S, and the exhaust gas phase reaction is over the second channel 30 in a state including HNO ₃ is introduced into

In the second channel 30, NaOH as a neutralizing agent is injected to the exhaust gas introduced from the first channel 20 through the second nozzle 32 (S30).

The NaOH neutralizing agent is reacted according to the general formula HNO ₃ and the bottom of the exhaust gas to neutralize the HNO _3.

(Formula 4) HNO ₃ + NaOH -----> NaNO ₃ + H ₂ O

In the same way, the first channel 20 _{removes NO 2} to increase the NOx removal rate, and the second channel 30 _{removes HNO 3} to control the pH.

Next, the exhaust gas discharged from the second channel 30 moves to the electrostatic precipitator 40 to process the acidic material (S40). Specifically, the exhaust gas particles flowing into the dust collecting chamber 41 of the electric dust collecting unit 40 are discharged by the high voltage discharge of the electric discharge unit 41, and the acid material particles among the discharged particles are formed by a neutralizing agent. It is collected by the dust collector 42 .

Then, the exhaust gas from which the acidic material is removed is discharged to the outside of the device, and at this time, the NOx concentration and the pH concentration of the exhaust gas discharged through the gas analyzer 50 are measured.

On the other hand, the control unit receives the NOx concentration from the gas analyzer 50 to calculate the NOx removal rate, and controls the input timing and input amount of the reducing agent and the neutralizing agent according _{to the preset NOx removal rate reference value or the preset H 2 S generation concentration reference value.} can do.

In this case, the NOx removal rate is calculated from the ORP measurement value transmitted from the ORP sensor 24 , and the H ₂ S generation concentration can be measured from the pH measurement value transmitted from the pH sensor 34 .

_{Using the above method, it is possible to significantly reduce the NOx removal rate and the generation of hydrogen sulfide (H 2} S) by performing individual and sequential chemical reactions, and at the same time, the amount of the reducing agent used can be significantly reduced.

Next, an apparatus and method for treating exhaust gas of a multi-stage scrubber according to a second embodiment of the present invention will be described.

In the second embodiment, in the first channel 20, sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium sulfite (Na ₂ SO ₃ ) mixed in a one-to-one ratio as a reducing agent are sprayed, and in the second channel 30 , NaOH is sprayed as a neutralizer. Other than that, since the entire device is the same as that of the first embodiment described above, a description of the device is omitted.

The reducing agent injected from the first channel 20 is sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium sulfite (Na ₂ SO ₃ ) mixed one-to-one, and reacts with nitrogen dioxide of the exhaust gas according to the following chemical formula, respectively.

(Formula 5)

2NO ₂ + 4Na ₂ SO ₃ →4Na ₂ SO ₄ + N ₂

(Formula 6)

2NO ₂ + Na ₂ S ₂ O ₃ + H ₂ O → Na ₂ S ₂ O ₄ + 2HNO ₂ + S

Here, NO ₂ is _{removed while Na 2} S ₂ O ₄ is generated, and HNO ₂ is generated as a by-product.

And, _{the exhaust gas containing the by-product HNO 2} is removed by moving to the second channel 30 and reacting with NaOH as shown in Chemical Formula 7 below.

(Formula 7)

HNO ₂ + NaOH -----> NaNO ₂ + H ₂ O

On the other hand, in the control unit, as in the first embodiment, receives the NOx concentration from the gas analyzer 50 and calculates the NOx removal rate, and the reducing agent according _{to the preset NOx removal rate reference value or the preset H 2 S generation concentration reference value} And it is possible to control the input timing and amount of the neutralizing agent.

In this case, the NOx removal rate is calculated from the ORP measurement value transmitted from the ORP sensor 24 , and the H ₂ S generation concentration can be measured from the pH measurement value transmitted from the pH sensor 34 .

_{Using the above method, it is possible to significantly reduce the NOx removal rate and the generation of hydrogen sulfide (H 2} S) by performing individual and sequential chemical reactions, and at the same time, the amount of the reducing agent used can be significantly reduced.

Experimental example

The table below is a table of the results of experiments by changing the type of reducing agent and the material input to the exhaust gas to measure the amount of a reducing agent suitable for exhaust gas containing NOx.

All the experimental conditions of the above experiments were tested under the same conditions as the type of reducing agent, the use of sodium hydroxide (NaOH), NOx and other components included in the exhaust gas, and the exhaust gas injection rate, concentration, and operating time were the same. The set NOx removal rate (standard value) is 80%, and the generated H ₂ S concentration (standard value) is 0 ppm.

Experiment 1

In Experiment 1, exhaust gas containing NOx was introduced into a scrubber having a single channel, and Na ₂ S was used as a reducing agent, so that the average NOx removal rate was 67.0% and _{the concentration of generated H 2} S was 23.7ppm. At this time, _{the actual usage amount of Na 2} S was 0.58 (g/min), 2.52 times the theoretical usage amount of 0.23 (g/min) was used. Experiment 1 showed that the average NOx removal rate did not reach the NOx removal rate (80%) set as 67%, and _{the concentration of H 2} S (23.7ppm) was very high.

Experiment 2

Experiment 2 In order to suppress H ₂ S using the NaOH with Na with a Na ₂ S average NOx removal occurred in experiment 1, the concentration of H ₂ S 77.9%, were generated as 4.0ppm. At this time, _{the actual usage amount of Na 2} S is 1.46 (g/min), which is 5.11 times the theoretical usage amount of 0.29 (g/min), and the actual usage amount of NaOH is 0.12 (g/min), which is 0.47 of the theoretical usage amount 0.26 (g/min). boat was used. In Experiment 2, the average NOx removal rate increased to 77.9%, close to 80%, compared to Experiment 1, and the concentration (4.0 ppm) of _{H 2 S was lowered, but the amount of Na 2} S as a reducing agent increased more than twice. The average NOx removal rate and _{the concentration of H 2} S were still below the standard values, and only the amount of the reducing agent was increased.

Experiment 3

In Experiment 3, exhaust gas containing NOx and HCl was introduced into a scrubber having a single channel, and Na ₂ S and NaOH were used together as reducing agents, so that the average NOx removal rate was 81.0%, and _{the concentration of generated H 2} S was 1.0 ppm. At this time, _{the actual usage amount of Na 2} S is 1.88 (g/min), which is 6.2 times the theoretical usage amount of 0.30 (g/min), and the actual usage amount of NaOH is 0.30 (g/min), 0.60 of the theoretical usage amount 0.50 (g/min). boat was used. Experiment 3 assumes that HCl is included in the exhaust gas of the semiconductor process. Compared to Experiment 2, the average NOx removal rate (81.0%) has a lower H ₂ S concentration (1.0 ppm), but still the H ₂ S concentration was higher than the reference value, and _{the amount of Na 2} S, a reducing agent, was increased.

Experiment 4

_{In Experiment 4, exhaust gas containing NOx and SO 2} was introduced into a scrubber having a single channel _{, and Na 2} S and NaOH were used together as reducing agents, so that the average NOx removal rate was 82.9%, and _{the concentration of generated H 2} S was 1.8ppm. At this time, _{the actual amount of Na 2} S used is 2.17 (g/min), which is 5.84 times the theoretical amount of 0.37 (g/min), and the actual amount of NaOH used is 0.56 (g/min), which is 0.71 of the theoretical amount of 0.56 (g/min). boat was used. _{Experiment 4 assumes that SO 2} is included in the exhaust gas of the semiconductor process. Compared to Experiment 3, the average NOx removal rate (82.9%) increased while _{the amount of Na 2} S used was relatively decreased, but the amount of H ₂ S was still increased. The concentration (1.8ppm) was higher than the reference value.

Experiment 5

In Experiment 5, exhaust gas containing NOx, HCl, and SO _{2 was introduced into a scrubber having a single channel, and Na 2} S and NaOH were used together as reducing agents, so that the average NOx removal rate was 83.0%, and _{the concentration of H 2} S was 1.2 ppm. . At this time, _{the actual usage amount of Na 2} S is 2.50 (g/min), which is 7.25 times the theoretical usage amount of 0.34 (g/min), and the actual usage amount of NaOH is 1.04 (g/min), 1.09 of the theoretical usage amount 0.95 (g/min). boat was used. Experiment 5 assumes that HCl and SO ₂ are contained in the exhaust gas of the semiconductor process. Compared to Experiment 4, the average NOx removal rate (83.0%) was increased, but _{the concentration of H 2} S (1.2ppm) was still higher than the reference value. high, and _{the amount of Na 2} S used increased by 7.25 times.

Experiment 6

In Experiment 6, exhaust gas containing NOx was introduced into a scrubber formed of two channels, and Na ₂ S was used as a reducing agent only in the first channel. At this time, the average NOx removal rate was 84.1%, _{the concentration of H 2} S was 12.2 ppm, and _{the actual amount of Na 2} S was 0.53 (g/min), which was 1.40 times the theoretical amount of 0.38 (g/min). In Experiment 6, the theoretical amount of reducing agent used was lower than in Experiment 1, and the average NOx removal rate rose to an appropriate level of 84.1%, but _{the concentration of H 2} S was still maintained at a high level of 12.2 ppm.

Experiment 7

In Experiment 7, exhaust gas containing NOx was introduced into a scrubber formed of two channels, Na ₂ S was used as a reducing agent in the first channel, and NaOH as a neutralizer was used in the second channel. At this time, the average NOx removal rate was 82.6%, _{the concentration of H 2} S was 1.3 ppm, and _{the actual amount of Na 2} S was 0.49 (g/min), 1.67 times the theoretical amount of 0.29 (g/min), and the actual amount of NaOH. The dose was 0.15 (g/min), which was 0.58 times the theoretical dose of 0.26 (g/min). _{In Experiment 7, compared to Experiment 2 in which Na 2} S and NaOH were used together in a single channel, the average NOx removal rate was increased to a suitable level to 82.6% while lowering the amount of the reducing agent to a very low level compared to the theoretical level, and the concentration of _{H 2 S} It was reduced to a very low level to 1.3 ppm in FIG.

_{That is, it was confirmed that the use of Na 2} S and NaOH by separating each of the two channels significantly reduced the amount of reducing agent and also reduced the concentration of _{H 2 S.}

Experiment 8

In Experiment 8, exhaust gas containing NOx was introduced into a scrubber formed of a single channel, and Na ₂ S ₂ O ₃ was used as a reducing agent, so that the average NOx removal rate was 77.9% and _{the concentration of H 2} S was 0ppm. At this time, _{the actual usage amount of Na 2} S ₂ O ₃ was 80.9 (g/min), which was 80.9 times the theoretical usage amount of 1.54 (g/min). Experiment 8 was confirmed that the H ₂ S does not occur as the concentration of H ₂ S 0ppm compared with experiments 1-7 one ideal form though there is a problem that the reducing agent amount 80.9 times that appears over theoretical amount.

Experiment 9

In Experiment 9, exhaust gas containing NOx was introduced into a scrubber formed of a single channel, and Na ₂ S ₂ O ₃ was used as a reducing agent, so that the average NOx removal rate was 69.0%, and _{the concentration of H 2} S was 0ppm. At this time, _{the actual usage amount of Na 2} S ₂ O ₃ was 57.3 (g/min), which was 42.7 times the theoretical usage amount of 1.34 (g/min). In Experiment 9, the concentration of H ₂ S was 0 ppm as compared to Experiments 1 to 7, and H ₂ S did not occur, and the amount of reducing agent was also reduced compared to Experiment 8, but it was confirmed that the amount of reducing agent was still 42.7 times higher than that of the theoretical amount. did.

mixing ratio experiment

Based on the experimental results of Experiment 8 and Experiment 9, sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium sulfite (Na ₂ SO ₃ ) H ₂ S was not generated. Accordingly, sodium thiosulfate (Na ₂ S ₂ O ₃ ) and sodium sulfite (Na ₂ SO ₃ ) were mixed and used as a reducing agent, and the following mixing ratio experiment was performed to find the optimal mixing ratio to minimize the amount of reducing agent used. Experimental conditions were set at 1CMM (m³/min), nitrogen monoxide (NO) concentration of 200ppm, and an average NOx removal rate of 90% for an average operating time of 1 hour.

3 is a graph showing the relationship between the total amount of the reducing agent per minute and the mixing ratio of the reducing agent. Referring to FIG. 3, the total amount of reducing agent used per minute (g/min) is shown as an approximately "U"-shaped graph when viewed as a whole. It was confirmed that it is the optimal mixing ratio that can be used.

Experiment 10

Experiment 10 introduced exhaust gas containing NOx into a scrubber with a single channel, and using Na ₂ SO ₃ + Na ₂ S ₂ O ₃ mixed in a one-to-one ratio as a reducing agent, the average NOx removal rate was 82.0% and that of H ₂ S The concentration was found to be 0 ppm. _{At this time, the actual amount of Na 2} SO ₃ + Na ₂ S ₂ O ₃ mixed in a one-to-one ratio was 7.90 (g/min), which was 5.45 times the theoretical amount of 1.45 (g/min). In Experiment 10, the concentration of H ₂ S was 0 ppm as compared to Experiments 1 to 7, and H ₂ S did not occur, and compared to Experiments 8 and 9, the amount of reducing agent used was also significantly reduced to 1/8 to 1/10 level. confirmed that.

Experiment 11

In Experiment 11, exhaust gas containing NOx was introduced into a scrubber formed of two channels, and in the first channel, Na ₂ SO ₃ + Na ₂ S ₂ O ₃ mixed in a one-to-one ratio as a reducing agent was used, and in the second channel, a neutralizing agent was used. NaOH was used. _{Experiment 11 assumes that HCl and SO 2} are contained in the exhaust gas of the semiconductor process as in Experiment 5. By using NaOH in the second channel, which was confirmed through Experiment 7, the _{reduction in H 2} S concentration and reduction in the amount of reducing agent was achieved. wanted to check.

As a result of Experiment 11, the average NOx removal rate was 81.0%, and _{the concentration of H 2} S was 0 ppm. _{And, the actual amount of Na 2} SO ₃ + Na ₂ S ₂ O ₃ mixed in a one-to-one ratio was 7.80 (g/min), 5.5 times the theoretical amount of 1.42 (g/min), and the actual amount of NaOH as a neutralizing agent was As 0.98 (g/min), 1.06 times the theoretical amount of 0.92 (g/min) was used. As a result, even under the same conditions as in the actual semiconductor process environment, H ₂ S was not generated while remarkably lowering the amount of reducing agent used.

Prepare a multi-stage scrubber having two channels as described above, use Na ₂ SO ₃ + Na ₂ S ₂ O ₃ mixed in a one-to-one ratio in the first channel, and use NaOH in the second channel, NOx removal rate While satisfying the set value, H ₂ S is not generated and the amount of reducing agent used can be significantly reduced.

The scope of the present invention is not limited to the above-described embodiments, but may be implemented in various forms of embodiments within the scope of the appended claims. Without departing from the gist of the present invention claimed in the claims, it is considered within the scope of the description of the claims of the present invention to various extents that can be modified by any person skilled in the art to which the invention pertains.

※Explanation of symbols for main parts of the drawing※
10: ozone generator
20: first channel 21: first storage tank
22: first spray nozzle 23: first water tank
24: ORP sensor
30: second channel 31: second storage tank
32: spray nozzle 33: second water tank
34: pH sensor
40: electric dust collector
41: dust collector chamber 42: discharge unit
43: dust collector 50: gas analyzer

Claims (10)

In the exhaust gas treatment apparatus of a multi-stage scrubber,
a first channel through which exhaust gas including NOx is introduced and a reducing agent is injected; and,
Exhaust gas treatment apparatus of a multi-stage scrubber comprising a; a second channel located on the side of the first channel, through which the exhaust gas passing through the first channel is introduced, and a neutralizing agent is injected so as not to be mixed with the reducing agent. According to claim 1,
a gas analyzer for measuring _{the NOx concentration and the H 2} S concentration of the exhaust gas discharged from the second channel;
a first storage tank positioned under the first channel to store the reducing agent;
a first water tank installed to supply the reducing agent to the first storage tank;
ORP sensor for measuring the ORP of the reducing agent stored in the first storage tank;
a second storage tank positioned below the second channel to store the neutralizing agent;
a second water tank installed to supply the neutralizing agent to the second storage tank;
a pH sensor for measuring the pH of the neutralizing agent stored in the second storage tank; and,
The NOx removal efficiency is calculated based on the measured value of the ORP sensor according to the NOx concentration of the gas analyzer, and the concentration of H ₂ S is output based on the measured value of the pH sensor, and the set NOx removal rate reference value or the set H ₂ S generation concentration. Exhaust gas treatment apparatus of a multi-stage scrubber comprising a; a control unit for controlling the input timing and input amount of the reducing agent and the neutralizing agent according to the reference value. 3. The method of claim 2,
When the calculated NOx removal rate is smaller than the set NOx removal rate, the control unit controls to supply the reducing agent of the first water tank to the first channel to be greater than or equal to the set NOx removal rate. 3. The method of claim 2,
If the control unit is the concentration of H ₂ S measured than the concentration of a predetermined H ₂ S increases, that controls to supply to the second channel the neutralizing agent in the second tank to become less than or equal to the concentration of the set H ₂ S Exhaust gas treatment device of multi-stage scrubber. According to claim 1,
It further includes an electric dust collecting unit installed at the rear end of the second channel, including a discharge unit and a dust collecting unit, to receive the exhaust gas treated in the second channel,
The dust collecting unit is an exhaust gas treatment device of a multi-stage scrubber formed of a water film using the neutralizing agent. According to claim 1,
_{The reducing agent is sodium thiosulfate (Na 2} S ₂ O ₃ ) and sodium sulfite (Na ₂ SO ₃ ) mixed in a one-to-one ratio, and the neutralizing agent is NaOH. According to claim 1,
The reducing agent is Na ₂ S, the neutralizing agent is NaOH exhaust gas treatment apparatus of a multi-stage scrubber. In the exhaust gas treatment method of a multi-stage scrubber,
removing nitrogen oxides by injecting a reducing agent into the exhaust gas containing nitrogen dioxide introduced into the first channel; and,
Including; spraying a neutralizing agent to the exhaust gas flowing into the second channel through the first channel to remove nitrogen oxides;
The reducing agent controls the input timing and input amount according to the set NOx removal rate reference value, and the neutralizing agent controls the input timing and input amount according to the set reference value of the H ₂ S generation concentration. Exhaust gas treatment method of a multi-stage scrubber. 9. The method of claim 8,
_{The reducing agent is sodium thiosulfate (Na 2} S ₂ O ₃ ) and sodium sulfite (Na ₂ SO ₃ ) mixed in a one-to-one ratio, and the neutralizing agent is NaOH. 9. The method of claim 8,
The reducing agent is Na ₂ S, the neutralizing agent is NaOH exhaust gas treatment method of a multi-stage scrubber.

Images