KR102474635B1 - Exhaust gas treatment liquid for simultaneous reduction sulfur oxide and nitrogen oxide in exhaust gas, and exhaust gas treatment method using same - Google Patents

Abstract

The present invention is to provide an exhaust gas treatment liquid and an exhaust gas treatment method capable of simultaneously removing sulfur oxides and nitrogen oxides from exhaust gas in a desulfurization facility.
The present invention is a mixture of a desulfurization agent and a metal chelating agent containing at least one compound selected from the group consisting of Mg(OH) ₂ , Ca(OH) ₂ , CaCO ₃ and NaOH, for simultaneous reduction of sulfur oxides and nitrogen oxides in exhaust gas. Flue gas treatment liquid is provided.

Description

Exhaust gas treatment liquid for simultaneous reduction of sulfur oxides and nitrogen oxides in exhaust gas and exhaust gas treatment method using the same

The present invention relates to an exhaust gas treatment liquid for simultaneously reducing sulfur oxides and nitrogen oxides in exhaust gas and an exhaust gas treatment method using the same.

Exhaust gas generated from a heat source contains harmful components such as sulfur oxides (SOx), nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO ₂ ), hydrogen cyanide (HCN), and hydrogen chloride (HCl).

Recently, due to climate change caused by ozone depletion, regulations on the emission of such harmful components are being strengthened worldwide. In Korea, since January 2020, a law that has strengthened the air pollutant emission concentration standard by 30% has been in effect. In addition, as the total air pollutant management system was expanded to the whole country following the metropolitan area from April, 600 mid- to large-sized businesses, such as chemical, steel, and power generation, were subject to additional management, and it is expected to expand to small businesses.

More than 95% of sulfur oxides in exhaust gas are removed by spraying a desulfurizer in a wet scrubber. In the early 2000s, we manufactured and sold magnesium hydroxide (Mg(OH) ₂ ) for desulfurization using seawater, and our Mg(OH) ₂ is silicon dioxide that causes clogging of spray nozzles by scale (SiO ₂ ) content is lower than that of natural Mg(OH) ₂ .

On the other hand, in order to remove nitrogen oxides (NOx) from exhaust gas, a selective catalytic reduction (SCR) or a non-selective catalyst reduction (SNCR) is generally used, and in this way, more than 90% of nitrogen Oxides can be removed. However, the above method requires an expensive catalyst and requires a lot of cost because the exhaust gas temperature must be raised. Recently, academia has actively conducted research on nitrogen oxide removal using plasma or ozone in addition to the above-described method, but this also requires a lot of equipment investment and operating costs, making it difficult to apply to the industry.

The industry is investing in various environmental pollution prevention facilities along with technology development to minimize the concentration of pollutants in exhaust gas, but this is reflected in cost and becomes a factor that weakens competitiveness. In particular, when there is no separate denitrification facility, it is necessary to introduce a new denitrification facility to meet the strengthened law, but excessive cost is required for facility investment, and it is difficult to prepare a facility site in the factory. Accordingly, an attempt was made to reduce the concentration of pollutants in the exhaust gas by changing the combustion conditions, but this method is also not a fundamental solution. On the other hand, companies operating denitrification facilities additionally require expensive catalysts or chemicals, and additional energy costs are incurred, increasing the burden.

Korean Patent Publication No. 10-2016-0084527

The present invention is to solve the above problem, and to provide an exhaust gas treatment liquid and an exhaust gas treatment method capable of simultaneously removing sulfur oxides and nitrogen oxides from exhaust gas in a single desulfurization facility.

In addition, the present invention is to provide an exhaust gas treatment liquid and an exhaust gas treatment method that can reduce costs by treating exhaust gas in a single desulfurization facility without using an expensive catalyst.

One aspect of the present invention is a mixture of a desulfurization agent and a metal chelating agent containing at least one compound selected from the group consisting of Mg(OH) ₂ , Ca(OH) ₂ , CaCO ₃ and NaOH, sulfur oxides and nitrogen oxides in flue gas An exhaust gas treatment liquid for simultaneous reduction is provided.

Another aspect of the present invention, in the reactor, Mg (OH) ₂ , Ca (OH) ₂ , CaCO ₃ and a metal chelating agent containing at least one compound selected from the group consisting of a mixed exhaust gas treatment liquid containing a mixture Provided is an exhaust gas treatment method for simultaneously reducing sulfur oxides and nitrogen oxides in exhaust gas, including the step of bringing gas-liquid contact with exhaust gas.

According to the present invention, it is possible to simultaneously treat sulfur oxides and nitrogen oxides in exhaust gas in a single reactor by using an exhaust gas treatment liquid in which a desulfurization agent and a metal chelating agent are mixed.

In addition, according to the present invention, the catalyst cost can be reduced by treating nitrogen oxides using a metal chelating agent without using an expensive catalyst.

In addition, according to the present invention, since sulfur oxides and nitrogen oxides in exhaust gas can be simultaneously treated without a separate denitrification facility, costs required for preparing denitration facilities can be reduced.

Various advantageous advantages and effects of the present invention are not limited to the above description, and will be more easily understood in the process of describing specific embodiments of the present invention.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified in various forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention provides an exhaust gas treatment liquid capable of simultaneously reducing sulfur oxides and nitrogen oxides in exhaust gas and an exhaust gas treatment method using the exhaust gas treatment liquid.

flue gas treatment liquid

In the present invention, flue gas means emissions from air pollutant sources such as calcination furnaces, incinerators, and heating furnaces, and these flue gases contain a large amount of air pollutants such as carbon monoxide, sulfur oxides, nitrogen oxides, volatile organic compounds, and fine dust. .

In the present invention, sulfur oxides and nitrogen oxides may be expressed as SOx and NOx, respectively. Examples of sulfur oxides include SO, SO ₂ , SO ₃ and the like, examples of nitrogen oxides include NO, NO ₂ , N ₂ O ₅ and the like, but are not limited thereto.

Among nitrogen oxides, NO is known as the most difficult material to remove because it has a stable chemical structure and low solubility. In order to remove these nitrogen oxides, as described above, a selective catalytic reduction (SCR) or a non-selective catalytic reduction (SNCR) is used. However, since a separate denitrification facility is required to remove nitrogen oxides by the selective catalytic reduction method or the non-selective catalytic reduction method, it is difficult to simultaneously remove sulfur oxides and nitrogen oxides.

In the present invention, sulfur oxides and nitrogen oxides can be simultaneously removed in a single reactor by using an exhaust gas treatment liquid in which a metal chelating agent is mixed with a desulfurization agent. In general, a wet scrubber is used to remove sulfur oxides, and when the exhaust gas treatment liquid according to the present invention is used, sulfur oxides and nitrogen oxides can be removed in a wet scrubber.

The type of desulfurization agent that can be used in the present invention is not particularly limited, and for example, at least one compound selected from the group consisting of Mg(OH) ₂ , Ca(OH) ₂ , CaCO ₃ and NaOH may be used. In the case of using such a desulfurization agent, more than 95% of sulfur oxides in exhaust gas can be removed. The desulfurization agent may be mixed with water and used in the form of a slurry.

In the present invention, the metal chelating agent can convert NO having low solubility into a metal complex compound having high solubility.

The metal chelating agent may be a complex compound or a coordination compound in which a central metal atom is attached to a large molecule called a ligand (ligand) to form a ring structure. Examples of the ligand include EDTA (Ethylenediaminetetraacetic acid, C ₁₀ H ₁₆ N ₂ O ₈ ) and NTA (Nitriloriacetic acid, C ₆ H ₉ NO ₆ ). Examples of the EDTA include EDTA-2Na and EDTA-Fe , EDTA-Cu, and EDTA-Ca. Since EDTA is poorly soluble in water, EDTA-2Na with Na groups can be used.

In addition, the metal atom in the metal chelating agent may include iron (Fe), manganese (Mn), nickel (Ni), zinc (Zn), molybdenum (Mo), magnesium (Mg), etc., preferably iron ( Fe) may be.

The mechanism of nitrogen oxide removal reaction in exhaust gas using a metal chelating agent is shown in Schemes 1 to 3 below.

[Scheme 1] NO + M ⁺ Ln ^- → M ⁺ Ln ^- NO

[Scheme 2] SO ₂ → SO ₃ ^2-

[Scheme 3] 2M ⁺ Ln ^- NO + 2SO ₃ ^2- → 2M ⁺ Ln ^- + N ² + 2SO ₄ ^2-

In Schemes 1 to 3, M ⁺ Ln ^- is a metal chelating agent, M is a metal atom, and Ln is a ligand.

As described in Scheme 1, NO reacts with the metal chelating agent to form the M ⁺ Ln ^- NO intermediate compound. Referring to Scheme 3, the M ⁺ Ln ^- NO intermediate compound is reduced to harmless N ₂ by contacting an aqueous solution in which SO ₂ is dissolved, and then discharged into the atmosphere. Meanwhile, SO ₄ ^2- formed by the reaction between the M ⁺ Ln ^- NO intermediate compound and SO ₃ ^2- is discharged into water after reacting with the desulfurization agent. For example, when Mg(OH) ₂ is used as a desulfurization agent, SO ₄ ^2- may react with Mg(OH) ₂ to be discharged in the form of a MgSO ₄ compound.

The exhaust gas treatment liquid according to the present invention may be prepared by dissolving and reacting a metal compound and a chelate in an aqueous solution or slurry of a desulfurization agent. At this time, the concentration of the metal chelating agent in the exhaust gas treatment liquid may be 0.03 to 0.1M, preferably 0.03 to 0.07M, and more preferably 0.03 to 0.05M. If the concentration of the metal chelating agent is 0.03 M or less, the initial nitrogen oxide removal rate is greatly reduced, and if the concentration is 0.1 M or more, excessive cost is required, which is undesirable in terms of economic efficiency.

As an example, when the desulfurization agent is Mg(OH) ₂ and the metal chelating agent is an iron (II) chelating agent, FeSO ₄ 7H ₂ O and EDTA so that the concentration of the iron (II) chelating agent in Mg(OH) ₂ is 0.03M -2Na can be melted and reacted for a certain period of time to produce an exhaust gas treatment liquid.

Exhaust gas treatment method

Hereinafter, an exhaust gas treatment method using the above-described exhaust gas treatment liquid will be described.

In the conventional desulfurization process, the input amount of the desulfurization agent was determined according to the pH value of the desulfurization treated water. For example, since the removal rate of sulfur oxides increases as the pH of the desulfurization treatment water increases, in order to prevent the removal rate of sulfur oxides from rapidly decreasing, a desulfurization agent is injected into the scrubber when the pH of the desulfurization treatment water is below a certain value. . When the desulfurization agent is introduced, the pH of the desulfurization treated water gradually increases, and when the pH reaches a specific value, the introduction of the desulfurization agent is stopped. However, when the exhaust gas treatment liquid according to the present invention is introduced in the above-described method, there is a problem in that the denitrification effect is not exhibited due to a very small input amount.

In the present invention, the exhaust gas treatment liquid may be injected into the reactor desulfurization agent input pipe, and, for example, may be injected into the pipe through a desulfurizer nozzle provided in the desulfurization agent input pipe. In this way, the flue gas treatment liquid introduced into the reactor is in countercurrent contact with the flue gas introduced into the lower part of the reactor to remove sulfur oxides and nitrogen oxides from the flue gas.

The input amount of the exhaust gas treatment liquid may be adjusted according to the exhaust gas inflow amount, the nitrogen oxide concentration in the exhaust gas, the nitrogen oxide inflow amount, or the contact temperature between the exhaust gas and the exhaust gas treatment liquid.

For example, when the concentration of nitrogen oxides in the exhaust gas is 100 ppm, the inflow of the exhaust gas is 1 L/min, and the concentration of the metal chelating agent solution in the exhaust gas treatment liquid is 0.03M, the input amount of the gas treatment liquid is 0.001 kg/min or more, preferably may be greater than or equal to 0.005 kg/min. If the exhaust gas treatment liquid is injected too little, the nitrogen oxide removal efficiency is lowered, which is not preferable.

On the other hand, as the exhaust gas input increases, the nitrogen oxide removal rate increases, but when a certain amount is reached, the nitrogen oxide removal rate does not increase any more. Considering this, the input amount of the flue gas treatment liquid may be 0.007 kg/min or less under the above conditions, and if it exceeds this, it is not preferable from an economic point of view.

In addition to the above-mentioned exhaust gas inflow, nitrogen oxide concentration or nitrogen oxide inflow, the burner capacity, reactor (scrubber) specifications, filling type and amount, environmental facility operating conditions such as wastewater treatment process, contact temperature of exhaust gas and exhaust gas treatment liquid can be adjusted according to

Example

Hereinafter, embodiments of the present invention will be described in detail. The following examples are only for understanding of the present invention, but do not limit the present invention.

[Example 1]

_{FeSO 4 7H 2} O and _EDTA- After adding 2Na, it was dissolved and mixed to prepare 1 ton of exhaust gas treatment liquid. Using a metering pump, the exhaust gas treatment liquid was introduced into a pipe for supplying a desulfurization agent connected to the reactor at a rate of 0.075 kg/min to countercurrently contact the exhaust gas flowing into the bottom of the reactor. At this time, the exhaust gas was introduced at a rate of 15 L / min, the concentration of NOx in the exhaust gas was 90 ppm, the concentration of SOx was 800 ppm, and the gas-liquid contact temperature was about 80 to 100 ° C.

[Example 2]

_{FeSO 4 7H 2} O and _EDTA- After adding 2Na, it was dissolved and mixed to prepare 5 kg of exhaust gas treatment liquid. Using a metering pump, the flue gas treatment liquid was introduced into the upper part of the reactor through the desulfurizer supply pipe at a flow rate of 0.02 kg/min, and the flue gas containing 150 ppm of NOx and 700 ppm of SOx was introduced into the lower part of the reactor to obtain the flue gas treatment liquid and anticurrent contact. At this time, the exhaust gas input flow rate was 15 L/min, and the gas-liquid contact temperature in the reactor was room temperature. Inside the reactor, 80 MESH SIEVE and Pauling were filled to make the gas-liquid contact area as large as possible.

[Example 3]

The flue gas was treated in the same manner as in Comparative Example 2, except that the flue gas treatment liquid was introduced into the top of the reactor through the desulfurizer supply pipe at a flow rate of 0.04 kg/min.

[Example 4]

The exhaust gas was treated in the same manner as in Comparative Example 2, except that the exhaust gas treatment liquid was introduced into the top of the reactor through the desulfurization agent supply pipe at a flow rate of 0.06 kg/min.

[Example 5]

The flue gas was treated in the same manner as in Comparative Example 2, except that the flue gas treatment liquid was introduced into the top of the reactor through the desulfurization agent supply pipe at a flow rate of 0.08 kg/min.

[Example 6]

The flue gas was treated in the same manner as in Comparative Example 2, except that the flue gas treatment liquid was introduced into the top of the reactor through the desulfurization agent supply pipe at a flow rate of 0.10 kg/min.

[Comparative Example 1]

_{FeSO 4 7H 2} O and _EDTA- After adding 2Na, it was dissolved and reacted to prepare 10 tons of exhaust gas treatment liquid. When the pH of the desulfurization treatment water in the reactor is 7 or less, the exhaust gas treatment liquid is injected by nozzle spraying, and when the pH is 9 or more, the introduction of the flue gas treatment liquid is stopped. At this time, the exhaust gas was introduced into the reactor at a rate of 15 L/min, the concentration of NOx in the exhaust gas was 90 ppm, the concentration of SOx was 800 ppm, and the gas-liquid contact temperature was about 80 to 100 °C.

[Comparative Example 2]

In the same manner as in Comparative Example ₂ , except that Mg(OH) ₂ slurry (POSCO Chemical Co.) containing 32% by weight of Mg(OH) 2 and 68% by weight of water was introduced into the reactor at a rate of 0.06 kg/min. flue gas was treated.

[Exhaust gas treatment result]

Using a gas concentration analyzer (TESTO 350K), the NOx and SOx concentrations in the exhaust gas discharged from the top of the reactor were measured, and the SOx and NOx removal rates were calculated and listed in Table 1 below.

division Example
One Example
2 Example
3 Example
4 Example
5 Example
6 comparative example
One comparative example
2 Composition of flue gas treatment liquid Mg(OH) ₂ + Fe-EDTA Mg(OH) ₂ flue gas
treatment liquid
input
[kg/min] 0.075 0.02 0.04 0.06 0.08 0.10 Desulfurized water
Input below pH 7,
pH 9 or higher
stop input 0.06 flue gas
Flow rate [L/min] 15 15 15 15 15 15 15 15 gas-liquid contact
Temperature [℃] 85 30 30 30 30 30 85 85 NOx
density
[ppm] input 90 150 150 150 150 150 90 150 dispose 32 120 100 80 75 70 90 150 NOx inflow
Kg/per minute
Flue gas treatment liquid input [kg/min] 55.56 8.89 17.78 26.67 35.56 44.44 - - NOx removal rate [%] 64 20 33 47 50 53 0 0 SOx removal rate [%] 99 95 95 95 95 95 99 95

Referring to Table 1, it can be seen that nitrogen oxides and sulfur oxides were simultaneously removed in a single reactor when the exhaust gas treatment liquid was introduced into the desulfurization agent supply pipe connected to the reactor as in Examples 1 to 6.

On the other hand, when the exhaust gas treatment liquid was input according to the pH of the desulfurization treatment water in the reactor as in Comparative Example 1, nitrogen oxides were not removed because the input amount of the flue gas treatment liquid was too small. Also, as in Comparative Example 2, nitrogen oxides were not removed even when only Mg(OH) ₂ desulfurization agent was added.

Claims (7)

delete delete delete In the reactor, the step of gas-liquid contacting the flue gas treatment liquid containing a mixture of a desulfurizer and a metal chelator containing at least one compound selected from the group consisting of Mg(OH) ₂ , Ca(OH) ₂ , CaCO ₃ and NaOH with the exhaust gas include,
The exhaust gas treatment method for simultaneously reducing sulfur oxides and nitrogen oxides in exhaust gas, wherein the exhaust gas treatment liquid is introduced into a desulfurization agent input pipe.
delete According to claim 4,
The metal chelating agent is at least one metal selected from the group consisting of iron (Fe), manganese (Mn), nickel (Ni), zinc (Zn), molybdenum (Mo) and magnesium (Mg); and at least one ligand selected from the group consisting of ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA).
According to claim 4,
An exhaust gas treatment method for simultaneous reduction of sulfur oxides and nitrogen oxides in exhaust gas, wherein the concentration of the metal chelating agent in the exhaust gas treatment liquid is 0.03 to 0.1M.