KR20220086306A - 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

An object of 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 in the exhaust gas in a desulfurization facility.
The present invention is Mg(OH) ₂ , Ca(OH) ₂ , CaCO ₃ For simultaneous reduction of sulfur oxides and nitrogen oxides in flue gas, in which a desulfurization agent and a metal chelating agent are mixed containing at least one compound selected from the group consisting of An exhaust gas treatment solution is provided.

Description

Flue gas treatment liquid for simultaneous reduction of sulfur oxides and nitrogen oxides in flue gas and a method for treating flue gas using the same

The present invention relates to an exhaust gas treatment liquid for simultaneous reduction of sulfur oxides and nitrogen oxides in the exhaust gas, and an exhaust gas treatment method using the same.

The exhaust gas generated from the 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, worldwide, due to climate change caused by ozone depletion, there is a trend to strengthen the emission regulations of these harmful substances. In Korea, from January 2020, a 30% stricter air pollutant emission concentration standard has been in effect. In addition, as the total amount of air pollutant management system has been expanded nationwide following the metropolitan area from April, more than 600 medium-to-large business sites such as chemical, steel and power generation are subject to additional management, and it is expected to expand to small business sites.

Most of the sulfur oxides in the flue gas are removed more than 95% by spraying a desulfurization agent in a wet scrubber. In the early 2000s, our company manufactures and sells magnesium hydroxide for desulfurization (Mg(OH) ₂ ) using seawater _. (SiO ₂ ) There is an advantage that the content is lower than that of natural Mg(OH) ₂ .

On the other hand, in order to remove nitrogen oxides (NOx) from the exhaust gas, in general, selective catalyst reduction (SCR) or non-selective catalyst reduction (SNCR) is used, and in this way, more than 90% nitrogen Oxides can be removed. However, the above-described method requires an expensive catalyst and requires a lot of cost because the temperature of the exhaust gas needs to be raised. Recently, academic circles have been actively conducting research on nitrogen oxide removal using plasma or ozone in addition to the above-described methods, but this also requires a lot of facility investment and operation cost, so it is difficult to apply to the industry.

In order to minimize the concentration of pollutants in the flue gas, the industry is investing in various environmental pollution prevention facilities along with technological development, but this is reflected in the cost and weakens competitiveness. In particular, if there is no separate denitrification facility, a new denitrification facility needs to be introduced in order to satisfy the strengthened law, but it takes excessive cost 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 also 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 in the exhaust gas in a single desulfurization facility.

In addition, an object of the present invention is to provide an exhaust gas treatment solution and an exhaust gas treatment method that do not use an expensive catalyst and can reduce costs by treating the exhaust gas in a single desulfurization facility.

One aspect of the present invention, Mg(OH) ₂ , Ca(OH) ₂ , CaCO ₃ A desulfurization agent and a metal chelating agent including at least one compound selected from the group consisting of NaOH are mixed, sulfur oxides and nitrogen oxides in the exhaust 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 desulfurization agent and a metal chelating agent containing at least one compound selected from the group consisting of NaOH mixed flue gas treatment liquid It provides an exhaust gas treatment method for simultaneously reducing sulfur oxides and nitrogen oxides in the exhaust gas, including the step of contacting the exhaust gas with gas-liquid contact.

According to the present invention, it is possible to simultaneously treat sulfur oxides and nitrogen oxides in the flue gas in a single reactor 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 the flue gas can be simultaneously treated without a separate denitrification facility, it is possible to reduce the cost required to prepare a denitration facility.

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

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiment of the present invention may be modified in various other 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 the exhaust gas, and an exhaust gas treatment method using the flue gas treatment liquid.

flue gas treatment liquid

In the present invention, the exhaust gas means that it is emitted from an air pollutant generating source such as a kiln, an incinerator, or a heating furnace, and such exhaust gas contains a large amount of air pollutants such as carbon monoxide, sulfur oxides, nitrogen oxides, volatile organic compounds, fine dust, etc. .

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

Among nitrogen oxides, NO is known as the most difficult substance to remove because it has a stable chemical structure and low solubility. In order to remove such nitrogen oxides, as described above, selective catalyst reduction (SCR) or non-selective catalyst reduction (SNCR) is used. However, since a separate denitration facility is required to remove nitrogen oxides by the selective catalytic reduction or non-selective catalytic reduction method as described above, 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 solution in which a metal chelating agent is mixed with a desulfurization agent. In general, a wet scrubber is used to remove sulfur oxides, and by using the flue gas treatment liquid according to the present invention, sulfur oxides and nitrogen oxides can be removed in the 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. When such a desulfurization agent is used, more than 95% of sulfur oxides in the flue 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, which has low solubility, into the form of a metal complex with high solubility.

The metal chelating agent may be a complex or 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 Ethylenediaminetetraacetic acid (EDTA, C ₁₀ H ₁₆ N ₂ O ₈ ), NTA (Nitriloriacetic acid, C ₆ H ₉ NO ₆ ), and the like, and the EDTA includes, for example, EDTA-2Na, EDTA-Fe , EDTA-Cu, EDTA-Ca, and the like. EDTA is poorly soluble in water, so EDTA-2Na having a Na group attached thereto 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).

The mechanism of the nitrogen oxide removal reaction in the 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 a metal chelating agent to form an M ⁺ Ln ^- NO intermediate compound. Referring to Scheme 3, the M ⁺ Ln ^- NO intermediate compound is reduced to harmless N ₂ in contact with an aqueous solution in which SO ₂ is dissolved, and then discharged to the atmosphere. On the other hand, SO ₄ ^2- formed by the reaction of the M ⁺ Ln ^- NO intermediate compound with SO ₃ ^2- is discharged into water after the reaction 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 flue gas treatment solution according to the present invention can 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 flue gas treatment liquid may be 0.03 to 0.1M, preferably 0.03 to 0.07M, more preferably 0.03 to 0.05M. If the concentration of the metal chelating agent is less than 0.03M, the initial nitrogen oxide removal rate is greatly reduced, and if it is more than 0.1M, the cost is excessive, which is not preferable in terms of economical efficiency.

As an example, when the desulfurizing 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 After dissolving -2Na, it is allowed to react for a certain period of time to prepare an exhaust gas treatment solution.

How to deal with flue gas

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 desulfurized water. For example, since the removal rate of sulfur oxides increases as the pH of the desulfurized water increases, in order to prevent a sharp decrease in the removal rate of sulfur oxides, if the pH of the desulfurized water is less than a specific value, the desulfurization agent is introduced into the scrubber. . When the desulfurizing agent is added, the pH of the desulfurized water gradually rises, and when the pH reaches a certain value, the desulfurization agent input is stopped. However, when the exhaust gas treatment liquid according to the present invention is added in the above-described manner, there is a problem in that the amount of input is very small and the denitrification effect is not exhibited.

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

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

For example, when the nitrogen oxide concentration in the flue gas is 100 ppm, the flue gas inflow rate is 1 L/min, and the metal chelating agent solution concentration in the flue 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. When the amount of the flue gas treatment liquid is too small, the nitrogen oxide removal efficiency is lowered, which is not preferable.

On the other hand, the nitrogen oxide removal rate increases as the amount of exhaust gas input 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 under the above-described conditions may be 0.007 kg/min or less, and if it exceeds this, it is not preferable from an economic point of view.

In addition to the exhaust gas input amount, the nitrogen oxide concentration or nitrogen oxide input amount in the exhaust gas described above, the amount of exhaust gas input includes burner capacity, reactor (scrubber) specifications, filling type and amount, environmental facility operating conditions such as wastewater treatment process, contact temperature of exhaust gas and flue 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 the understanding of the present invention, but do not limit the present invention.

[Example 1]

FeSO ₄ .7H ₂ O and EDTA- so that the concentration of the iron (II) chelating agent in the Mg(OH) ₂ slurry (POSCO Chemicals) containing 32 wt% of Mg(OH) ₂ and 68 wt% of water is 0.03 M 2Na was added and then dissolved and mixed to prepare 1 ton of flue gas treatment solution. 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 make countercurrent contact with the exhaust gas flowing into the lower part 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- so that the concentration of the iron (II) chelating agent in the Mg(OH) ₂ slurry (POSCO Chemicals) containing 32 wt% of Mg(OH) ₂ and 68 wt% of water is 0.03 M After adding 2Na, it was dissolved and mixed to prepare 5 kg of an exhaust gas treatment solution. Using a metering pump, the flue gas treatment liquid is introduced to the upper part of the reactor through a desulfurization agent 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 is introduced into the lower part of the reactor, and the flue gas treatment liquid and constant current 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. The inside of the reactor was filled with 80 MESH SIEVE and fouling to increase the gas-liquid contact area as much 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 to the upper part of the reactor through a pipe for supplying the desulfurization agent at a flow rate of 0.04 kg/min.

[Example 4]

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

[Comparative Example 1]

FeSO ₄ .7H ₂ O and EDTA- so that the concentration of the iron (II) chelating agent in the Mg(OH) ₂ slurry (POSCO Chemicals) containing 32 wt% of Mg(OH) ₂ and 68 wt% of water is 0.03 M After adding 2Na, it was dissolved and reacted to prepare 10 tons of flue gas treatment solution. When the pH of the desulfurized water in the reactor was 7 or less, the flue gas treatment liquid was injected by nozzle injection, and when the pH was 9 or more, the input of the exhaust gas treatment liquid was 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 Chemicals) containing 32 wt% of Mg(OH) ₂ and 68 wt% of water was put into the reactor at a rate of 0.06 kg/min. The flue gas was treated.

[Result of exhaust gas treatment]

The concentration of NOx and SOx in the exhaust gas discharged from the upper part of the reactor was measured using a gas concentration analyzer (TESTO 350K), and the SOx and NOx removal rates were calculated and shown 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 of pH 7 or less,
pH 9 or higher
stop dosing 0.06 flue gas
Inflow [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
per kg/min
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, as in Examples 1 to 6, when the flue gas treatment liquid was introduced into the desulfurization agent supply pipe connected to the reactor, nitrogen oxides and sulfur oxides were simultaneously removed in a single reactor.

On the other hand, as in Comparative Example 1, when the flue gas treatment solution was added according to the pH of the desulfurized water in the reactor, the amount of the flue gas treatment solution was too small to remove nitrogen oxides. In addition, as in Comparative Example 2, even when only the Mg(OH) ₂ desulfurizing agent was added, nitrogen oxides were not removed.

Claims (7)

Mg(OH) ₂ , Ca(OH) ₂ , CaCO ₃ and a metal chelating agent mixed with a desulfurization agent and a metal chelating agent including at least one compound selected from the group consisting of, exhaust gas treatment solution for simultaneous reduction of sulfur oxides and nitrogen oxides .
The method of claim 1,
The metal chelating agent may include 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).
The method of claim 1,
The concentration of the metal chelating agent in the flue gas treatment solution is 0.03 to 0.1M, the flue gas treatment solution for simultaneously reducing sulfur oxides and nitrogen oxides in the flue gas.
In the reactor, Mg(OH) ₂ , Ca(OH) ₂ , CaCO ₃ and gas-liquid contacting the exhaust gas treatment liquid mixed with a desulfurization agent and a metal chelating agent containing at least one compound selected from the group consisting of NaOH and the exhaust gas An exhaust gas treatment method for simultaneously reducing sulfur oxides and nitrogen oxides in the exhaust gas, including.
5. The method of claim 4,
The flue gas treatment liquid is input to a pipe for desulfurization agent input, the flue gas treatment method for the simultaneous reduction of sulfur oxides and nitrogen oxides in the flue gas.
5. The method of claim 4,
The metal chelating agent may include 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).
5. The method of claim 4,
An exhaust gas treatment method for simultaneously reducing sulfur oxides and nitrogen oxides in the exhaust gas, wherein the concentration of the metal chelating agent in the flue gas treatment liquid is 0.03 to 0.1M.