KR100406510B1 - Method and system for removing nitrogen oxide using oxidation catalyst - Google Patents

Abstract

The present invention provides a nitrogen oxide that is discharged so that the exhaust gas containing nitrogen oxide is discharged to the atmosphere as a harmless gas through a chemical treatment consisting of an oxidation step in a catalytic reactor and a reduction / neutralization step using a direct oxidation method using an oxidation catalyst. An apparatus for removing and a method of removing using the apparatus.

The present invention provides a catalytic reactor for oxidizing nitrogen oxide (NO) with an oxidation catalyst to oxidize to nitrogen dioxide (NO ₂ ); A first semi-dry scrubber for sprinkling reduction / neutralization of a reducing agent and a neutralizing agent in an acid gas included in nitrogen dioxide (NO ₂ ) and flue gas generated in the catalytic reactor; And a filter device for filtering the neutralized salts of the acid gases in the reduced by-product and flue gas by the first semi-dry scrubber.

In addition, the present invention comprises the oxidation step of oxidizing the nitrogen oxide introduced into the catalytic reactor using an oxidation catalyst; A reduction / neutralization process of sprinkling together with a reducing agent and a neutralizing agent on the oxidized nitrogen oxides and by-products; And a filtration process for filtration and exhausting the neutralized salt of acid gas in the reduced and neutralized reduced by-product and flue gas.

Description

NOx removal device using oxidation catalyst and its removal method {METHOD AND SYSTEM FOR REMOVING NITROGEN OXIDE USING OXIDATION CATALYST}

The present invention relates to a nitrogen oxide removal device for removing nitrogen oxides in the exhaust gas and a method for removing the same using the apparatus, and more particularly, the exhaust gas containing nitrogen oxides in the catalytic reactor using a direct oxidation method using an oxidation catalyst. Nitrogen produced to remove nitrogen oxide and acid gas in the exhaust gas and reducing by-products and neutralized salts through the chemical treatment process of oxidation and reduction / neutralization step A removal apparatus for removing an oxide and a removal method using the apparatus.

Nitrogen oxides are emitted in the form of NO and NO2, and their sources are largely divided into heating, industrial, transportation and power generation.

In the industrial sector, it is generated from precious metal melting, electronics, electricity, chemicals, ceramics, steel mills, power generation facilities, and various incinerators.

In the power generation sector, most of the nitrogen compounds contained in raw materials are emitted by combustion in thermal power plants and large buildings.

For example, in the process of producing products from raw metal melting and dissolved melting, several tens of times (4000 to 6000 ppm) of nitrogen oxides are emitted to the air emission standard, and in power generation facilities using liquid and gaseous fuels, there is no reduction measures. More than 500ppm is emitted during power generation. In some large buildings and industrial facilities, it is reasonable to see that yellow-red or yellow-brown fumes are emitted mainly from nitrogen oxides.

This nitrogen oxide (NOχ) has a great effect on ozone generation, which is often generated in large cities, it is desirable to remove it from the source.

Conventionally, NOx removal techniques using a catalyst include (1) catalytic decomposition (2) and (2) catalytic reduction (3) and (3) selective catalytic reduction (4).

Nitrogen oxide removal by the Selective Non-catalytic Reduction (SNCR) has a disadvantage that the reaction rate is too slow. Other methods include NH ₃ containing -NH and -CN radicals. , Urea, and so on,

4NH ₃ + 4NO + 0 ₂ → 4N ₂ + 6H ₂ O － ①

4NH ₃ + 5O ₂ → 4NO + 6H ₂ O － ②

The method by ① requires high temperature (700 ~ 1100 ℃) and needs to control the reducing agent injection amount according to NOχ amount, but there is a problem that unreacted substance is released into the air because the technology to control is not completed.

In the method described in ②, ammonia reacts directly with oxygen when the temperature is high, thereby increasing the ammonia loss rate and generating NO.

Furthermore, selective catalytic reduction with NH ₃ (SCR: Selective Catalytic Reduction) method is inde the following steps NOχ reduction reaction as the main reaction the key reaction NH ₃ oxidation reaction on the other hand, required in this technique is the reaction can be preferably suppressed The NH ₃ oxidation reaction is active when the reaction temperature is high.

6NO + 4NH ₃ + O ₂ → 5N ₂ + 6H ₂ O

↑

catalyst

6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O

↑

catalyst

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O

↑

catalyst

Becomes

On the other hand, in the reaction at high temperature, ammonia is excessively consumed by reacting ammonia, which is a reducing agent, with oxygen as follows.

4NH ₃ + 40 ₂ → 2N ₂ + 6H ₂ O

4NH ₃ + 50 ₂ → 4N ₂ + 6H ₂ O

4NH ₃ + 70 ₂ → 4N ₂ + 6H ₂ O

The reaction of 4NH ₃ + 30 ₂ → 4N ₂ + 6H ₂ O takes place.

The additional reaction in this process is as follows when the temperature is lowered below about 200 ℃.

2NH ₃ + H ₂ O + 2N0 ₂ → NH ₂ NO ₃ or NH ₄ NO ₂

Nitrate and sulphate are produced and there exists a possibility of clogging a reaction apparatus or reducing catalyst activity.

Finally, the method of using spherical activated alumina in the nitrogen oxide removal technique by the absorption (wet oxidation) method, as shown in Figure 1, in the first column (1) directly to the nitrogen oxide (NOχ) The removal is carried out together, and NaClO ₂ and NaOH are adsorbed in a semi-dry state on the spherical activated alumina of the second column 2.

4NO + 3NaClO ₂ + 4NaOH → 4NaNO ₃ + 3NaCl + 2H ₂ O

4NO + NaClO ₂ + 4NaOH → 4NaNO ₃ + NaCl + 2H ₂ O

In addition to the above reaction, some NaClO ₂ is decomposed and ClO ₃ and Cl ₂ are removed in the third column (3), but in order to complete the reaction in the first tower, the reaction tower is large and ClO ₂ , Cl ₂ Removal requires special expensive equipment.

In addition, absorbents include CO ₂ , H ₂ O, SO ₂ , HF, SiF ₄ , HCI, NH _3, etc., but the reaction rate and reaction rate are low.

The present invention in consideration of this point is to be an improvement of the conventional method, the exhaust gas with nitrogen then oxidizes NO of oxides to NO ₂ by the oxidation catalyst, the nitrogen to NO ₂ with a reducing agent (N ₂₎ contained in the The present invention proposes a removal apparatus for removing nitrogen oxide and a method of removing the same by reducing.

1 is a block diagram of a nitrogen oxide removal device using a conventional spherical activated alumina

2 is a view showing an experimental tool for explaining a method for removing nitrogen oxides according to the present invention.

3 is a block diagram showing a nitrogen oxide removal device of the present invention

Figure 4 is a block diagram showing a nitrogen oxide removal device as another embodiment of the present invention

Figure 5 is a schematic view showing a nitrogen oxide removal device as another embodiment of the present invention.

6 is a process chart showing a method for removing nitrogen oxides of the present invention.

* Description of the symbols for the main parts of the drawings *

100: catalytic reactor 110: first semi-dry scrubber

120: second semi-dry scrubber 130: filter device

140: blower 150: chimney

160: water tower

The present invention provides a catalytic reactor for oxidizing nitrogen oxide (NO) with an oxidation catalyst to oxidize to nitrogen dioxide (NO ₂ ); A first semi-dry scrubber for sprinkling reduction / neutralization of a reducing agent and a neutralizing agent in an acid gas included in nitrogen dioxide (NO ₂ ) and flue gas generated in the catalytic reactor; And a filter device for filtering the neutralized salts of the acid gases in the reduced by-product and flue gas by the first semi-dry scrubber.

Installed to be connected to the filter device for filtering the reduced by-products and neutralized salt discharged from the first semi-dry scrubber and to remove the contaminated gas (ammonia, chlorine group, etc.) not removed from the first semi-dry scrubber to discharge to the outside Characterized in that further comprises a water tower.

The first semi-dry scrubber 114 neutralizes nitrogen oxides, and is connected between the first semi-dry scrubber and the filter device to reduce nitrogen dioxide (NO ₂ ), which is a byproduct after neutralization, to nitrogen (N ₂ ). It characterized in that it further comprises a semi-dry scrubber.

The temperature of the catalytic reactor is characterized in that 150 ℃ ~ 700 ℃.

In addition, the present invention comprises the oxidation step of oxidizing the nitrogen oxide introduced into the catalytic reactor using an oxidation catalyst; A reduction / neutralization process of sprinkling together with a reducing agent and a neutralizing agent on the oxidized nitrogen oxides and by-products; And a filtration process for filtration and exhausting the neutralized salt of acid gas in the reduced and neutralized reduced by-product and flue gas.

Hereinafter, a preferred method for removing nitrogen oxides of the present invention and their removal apparatus will be described in detail.

3 is a block diagram showing a nitrogen oxide removal device of the present invention, Figure 4 is a block diagram showing a nitrogen oxide removal device as another embodiment of the present invention, Figure 5 is a nitrogen as another embodiment of the present invention A schematic diagram showing an oxide removal device.

6 is a flowchart illustrating a method of removing nitrogen oxides of the present invention.

First, the nitrogen oxide removal apparatus of the present invention will be described with reference to FIGS.

First, as shown in FIG. 3, the present invention includes a catalytic reactor 100, a first semi-dry scrubber 110, a filter device 130, a blower 140, and a chimney 150.

The catalytic reactor 100 is connected to the first semi-dry scrubber 110 by the pipe 92, the first semi-dry scrubber 110 and the filter device 130 is connected to the pipe 92, the blower ( 140 and the chimney 150 are also connected by the piping 92, respectively.

In addition, a burner 90 is installed on the left side of the catalytic reactor 100 to increase the temperature when the temperature of the discharged gas is low, and nitrogen oxide is discharged from the burner 90. At this time, when the temperature of the flue gas is always discharged to 150 ~ 700 ℃ burner 90 is not necessary.

The catalytic reactor 100 is preferably maintained at 150 ℃ ~ 700 ℃, the oxidation catalyst is equipped with a fixed facility.

When the temperature is 150 degrees or less at the temperature of the catalytic reactor 100, the reaction rate is not good, and when the temperature is 700 degrees or more, the oxidation catalyst is sintered, so that the reaction is performed within a predetermined range.

Nitrogen oxide discharged from the industrial flue gas and the burner 90 oxidizes nitrogen monoxide (NO) in the nitrogen oxide to nitrogen dioxide (NO ₂ ) by an oxidation catalyst fixedly added to the catalytic reactor (100).

The reaction formula when oxidized by the oxidation catalyst is as follows.

That is, (Scheme 1) 2NO + O ₂ → 2NO _{2 It} becomes.

↑

Oxidation catalyst

In the catalytic reactor 100, moisture is not generated, evaporation occurs, and nitrogen dioxide (NO ₂ ), which is a by-product after the reaction is performed by an oxidation catalyst, passes through the pipe 92 to the first semi-dry scrubber 110. Flows into.

The reducing agent and the neutralizing agent are added to the first semi-dry scrubber 110 together.

The reducing agent uses various reducing agents, and in the embodiment of the present invention, Na ₂ S and a strong reducing agent are used.

The neutralizing agent is used a variety of neutralizing agents, in the embodiment of the present invention is mainly used NaOH, Ca (OH) ₂ .

Nitrogen dioxide (NO ₂ ) introduced into the first semi-dry scrubber 110 is reduced to nitrogen (N ₂ ) by the sprinkling reducing agent and neutralizing agent.

At this time, the reaction formula is as follows.

That is, (Scheme 2) 2NO ₂ + Na ₂ S → N ₂ + Na ₂ SO ₄ .

Nitrogen (N ₂ ) and chlorine group (-Cl) reduced by the reducing agent as described above enters the filter device 130 along the pipe 92.

The filter device 130 preferably uses a conventional electrostatic precipitator and a bag filter having excellent performance.

Nitrogen (N ₂ ) and chlorine (-Cl) introduced into the filter device 130 are filtered by the filter device 130, and the cleanly treated gas is sucked by the blower 140 installed at one side. .

Then, the neatly treated gas sucked by the blower 140 is discharged to the outside air through the chimney 150.

Nitrogen oxide removal device using the oxidation catalyst of the present invention as described above does not cause pollution because secondary pollutants are not discharged because the denitrification rate is very high.

Subsequently, FIGS. 4 to 5 will be described.

First, Figure 4 is filtered by the filter device 130 in the nitrogen oxide removal device of the present invention shown in Figure 3, and is further provided with a sprinkling tower 160 to enable the reprocessing of by-products.

That is, the spray tower 160 is provided between the blower 140 and the chimney 150 for discharging the reduced by-product and the neutralized salt introduced into the filter device 130.

Alternatively, the chimney 150 may be provided with a spray tower 160 integrally.

The spray tower 160 installed as described above reprocesses ammonia, chlorine, and the like introduced by the blower 140. In other words, the nitrogen monoxide in the nitrogen oxides is fixed by the oxidation catalyst fixed in the catalytic reactor 100 ( NO) is oxidized to nitrogen dioxide (NO ₂ ).

The reaction formula when oxidized by the oxidation catalyst is as follows.

That is, (Scheme 1) 2NO + O ₂ → 2NO _{2 It} becomes.

↑

Oxidation catalyst

In the catalytic reactor 100, moisture is not generated, evaporation occurs, and nitrogen dioxide (NO ₂ ), which is a by-product after the reaction is performed by an oxidation catalyst, passes through the pipe 92 to the first semi-dry scrubber 110. Flows into.

After the first semi-dry scrubber 114 reduces / neutralizes the by-product discharged from the catalytic reactor 100, the by-products (ammonia, chlorine group, etc.) that are not treated in the first semi-dry scrubber 114 are filtered. After filtering by the device 130, the neutralizing agent is sprinkled and retreated to a gas having a small amount of ammonia, chlorine groups, etc. flowing through the filter device 130 to the water tower 160.

As the neutralizer used as the treatment agent for the gas having ammonia, chlorine group, etc., NaOH or Ca (OH) ₂ is used.

Subsequently, the nitrogen oxide removal apparatus of the present invention may be installed as shown in FIG. 5.

That is, the catalyst reactor 100 and the first semi-dry scrubber 114 are installed to communicate with each other by the pipe 92, and the second semi-dry scrubber 120 communicating with the first semi-dry scrubber 114 is continuously provided. Install it if possible.

Then, the second semi-dry scrubber 120 is connected to the pipe 92 so as to communicate with the filter device 130 is installed. Since the neutralized by-products are exhausted as described in FIG. 3.

Nitric oxide (NO) in the nitrogen oxide is oxidized to nitrogen dioxide (NO ₂ ) by the oxidation catalyst fixedly added to the catalytic reactor (100).

The reaction formula when oxidized by the oxidation catalyst is as follows.

That is, (Scheme 1) 2NO + O ₂ → 2NO ₂

3NO ₂ + Na ₂ S + O ₂ → 1/2 N ₂ + ₂ NaNO ₃ + S

2NO ₂ + 2Na ₂ S + O ₂ → N ₂ + 2Na ₂ SO ₃ .

In the catalytic reactor 100, moisture (waste water) does not occur, evaporation occurs, and nitrogen dioxide (NO ₂ ), which is a by-product after the reaction is performed by an oxidation catalyst, passes through the pipe 92 in the first semi-dry scrubber. Flows into 110.

Subsequently, the first semi-dry scrubber 114 sprinkles a reducing agent to reduce nitrogen oxides, and the second semi-dry scrubber 120 sprinkles a neutralizing agent to neutralize the reduced nitrogen oxides.

The neutralized nitrogen oxide is discharged through the chimney 150 using the blower 140 after being filtered through the filter device 130.

Referring to the operation of the present invention having such a configuration as follows.

First, the material used in the above-described catalytic reactor is an oxidation catalyst, the reducing agents supplied and sprinkled on the first semi-dry scrubber 110 are Na ₂ S and a strong reducing agent, and the neutralizer supplied and sprinkled on the second semi-dry scrubber 120. Is NaOH or slaked lime.

And, Figure 6 is a process chart showing a method for removing the nitrogen oxides of the present invention, first, the nitrogen oxide gas is discharged from the industrial equipment, the discharged nitrogen oxide is introduced into the catalytic reactor is oxidized (oxidation process).

Then, the oxidized nitrogen oxides are moved to the first semi-dry scrubber 110, and the nitrogen oxides are reduced by sprinkling a reducing agent. At this time, by simultaneously sprinkling the reducing agent and the neutralizing agent is reduced and at the same time the neutralization (reduction / neutralization process).

Then, the filter is filtered using the filter device 130 (filtration step). In this case, an electrostatic precipitator and a bag filter are used.

Subsequently, the clean gas, which has passed through the filter device 130 and completed the filtration process, is discharged to the chimney 150 using the blower 140 (exhaust process).

Looking at the nitrogen oxide removal device of the present invention in more detail, generally using an oxidation catalyst in the catalytic reactor 100,

2NO + O ₂ → becomes 2NO ₂ .

↑

Oxidation catalyst

When the oxidation catalyst is used in the catalytic reactor 100 as described above, it does not generate waste water, and as a result of the experiment, it can be seen that the treatment efficiency is increased.

<Table 1> Removal status of nitrogen oxide when using the oxidation catalyst of the present invention

NO Generation amount Occurrence after passing through oxidation catalyst After chemical treatment NO NO2 NOχ NO NO2 NOχ NO NO2 NOχ 1 2 3 4 5 40.45688.7784.21223.81727.4 26.336.559.479.5115.7 520.8725.2843.61303.31843.1 8.110.311.822.025.9 512.7714.9831.81281.31817.2 520.8 725.2843.61303.31843.1 3.23.84.17.88.3 2427233438 27.230.827.141.846.3

Since the catalytic reactor 100 is generally high in the range of about 150 to 700 ° C., as illustrated, it is preferable to use a heating means such as the burner 90, but the discharge heat is high when the discharge facility is operated. By specifying the appropriate location, waste heat can be used to increase efficiency without additional heat supply.

As such, when the catalytic reactor 100 is provided, most of the nitrogen monoxide (NO) in the catalytic reactor 100 completes the oxidation reaction and has a capacity or performance of less than the exhaust gas standard value when treating the nitrogen oxide.

Compared to the selective catalytic reduction method (SCR) of the conventional nitrogen oxide removal method of the present invention as described above, the installation cost is only 60%, the reduction rate of the nitrogen oxide reaches 99%, the operating cost is the selective catalytic reduction method (SCR) It is very useful in terms of cost because it has the advantage of using about 70%.

The present invention by installing and operating the nitrogen oxide removal device of the present invention in the process of oxidizing nitrogen monoxide to nitrogen dioxide using an oxidation catalyst in the catalytic reactor by reducing the nitrogen oxide discharged from the plant by 99% or more, without generating waste water, Almost completely eliminated can contribute to pollution prevention.

The present invention automatically analyzes each sprinkler pump installed per semi-dry scrubber in an analyzer installed in the operating room, and after measuring the NOx concentration, it is possible to reduce the consumption of chemicals by adjusting the chemical according to the NOx generation concentration, analyzer and temperature, According to the analysis of NOx concentration, the quantitative amount of ammonia is supplied. However, when excessively added, secondary pollution due to ammonia leakage occurs, but the present invention does not have secondary pollution.

That is, the present invention has an effect that does not cause secondary pollution because there is no unreacted material than conventional methods.

In addition, the present invention has the effect of easy operation, very high denitrification rate, low operating cost (70% of SCR).

In addition, it is easy to remove when sulfur compound (S0x) is generated, and it is easy to remove VOC and organic substances, and the use of an oxidizing agent can reduce the chemical cost of the oxidant, which is very economical, and the structure of nitrogen oxide treatment process and device is simple. Inexpensive supply also contributes to economic development.

In addition, when using an oxidation catalyst, the monthly chemical fee is

Monthly NO ₂ emissions = 85,000 Nm ³ / hr X (1600-100) ppm X 46 / 22.4 X 10 ^-6 kg / mg X24hr / day X 30 days / month = 188,518 kg / month,

Na ₂ S requirement,

2 X 46: 78 = 188,518: X, so X = 159,830 kg.

This means that if the average inoculation concentration is 500ppm, 24 hours, and the monthly operation time is 25 days, it can be seen that the drug cost is about 15,247,565 won as the drug cost, and thus the operating cost is low. As a result, it was found that about 20,400,156 won was spent on drug costs, resulting in a lower operating cost.)

Claims (5)

A catalytic reactor for reacting nitrogen oxides (NO) with an oxidation catalyst to oxidize to nitrogen dioxide (NO ₂ ); A first semi-dry scrubber for sprinkling reduction / neutralization of a reducing agent and a neutralizing agent in an acid gas included in nitrogen dioxide (NO ₂ ) and flue gas generated in the catalytic reactor; And a filter device for filtering the neutralized salt of acid gas in the reduced by-product and flue gas by the first semi-dry scrubber. The method of claim 1, Installed to be connected to the filter device for filtering the reduced by-products and neutralized salt discharged from the first semi-dry scrubber and to remove the contaminated gas (ammonia, chlorine group, etc.) not removed from the first semi-dry scrubber to discharge to the outside Nitrogen oxide removal device characterized in that it further comprises a spray tower. The method of claim 1, The first semi-dry scrubber 114 neutralizes nitrogen oxides, and is connected between the first semi-dry scrubber and the filter device to reduce nitrogen dioxide (NO ₂ ), which is a byproduct after neutralization, to nitrogen (N ₂ ). Nitrogen oxide removal device characterized in that it further comprises a semi-dry scrubber. The nitrogen oxide removal device of claim 1, wherein the temperature of the catalytic reactor is 150 ° C to 700 ° C. An oxidation step of oxidizing nitrogen oxide introduced into the catalytic reactor by using an oxidation catalyst; A reduction / neutralization process of sprinkling together with a reducing agent and a neutralizing agent on the oxidized nitrogen oxides and by-products; And a filtration process for filtering and exhausting the reduced and neutralized reduced by-products and the neutralized salts of acid gases in the flue gas.