KR102349120B1 - Exhaust gas purifying agent and exhaust gas purifying method using the same - Google Patents

Abstract

The present invention uses an exhaust gas purifying agent containing CKD, a by-product generated in the cement manufacturing process, to remove sulfur oxides and nitrogen oxides present in the exhaust gas, thereby recycling by-products generated in the cement industry to solve the problem of waste resource treatment Disclosed are an exhaust gas purifier that can reduce the cost required for maintaining alkalinity and prevent environmental pollution and an exhaust gas purification method using the same .

Description

Exhaust gas purifying agent and exhaust gas purifying method using the same

The present invention relates to an exhaust gas purification agent and an exhaust gas purification method using the same, and more particularly, to an exhaust gas purification agent using a by-product generated in a cement manufacturing process and an exhaust gas purification method using the same.

_{With the development of modern industry, harmful gases such as SO X} and NO _X emitted from various factories, thermal power plants, and incinerators cause serious air pollution, causing various diseases such as respiratory diseases, asthma, and lung cancer in our body. In particular, sulfur dioxide (SO ₂ ) is the main cause of air pollution, and many methods are being studied in countries around the world to remove these harmful gases.

As the flue gas sulfur oxide removal method, it is classified into a wet method and a dry method according to the type and use form of the absorption treatment agent for exhaust gas. The dry method is a method to remove sulfur dioxide by contacting particles and powders such as activated carbon or carbonate with the exhaust gas and adsorbing or reacting sulfur dioxide. Although the efficiency is somewhat lower, it is mainly used in small incinerators, etc. because equipment such as absorption towers or scrubbers are unnecessary, so equipment costs are low.

_{The wet method absorbs SO 2} in the gas phase using an absorbent of water or alkaline solution to produce a neutralization reaction and salt (Ca, Na, etc.) As a method, it has a high removal efficiency of 90% or more.

In the wet method, caustic soda (NaOH), etc., is widely used as an absorbent. It has the _{advantage of excellent reactivity with SO 2} , but has a problem in that the cost of the removal of flue gas sulfur oxide is high because the price is high.

In the case of the flue gas sulfur oxide removal facility, which is currently mainly used in Korea, the wet limestone-gypsum method is adopted, which uses limestone as an absorbent and gypsum as a by-product. However, economic and operational problems occur because mechanical problems such as aging of equipment, equipment failure, and improper operation, problems in the mass balance, problems in pH control, and process problems such as limestone utilization continue to appear.

Korea Patent No. 1626532 discloses a seawater treatment apparatus using limestone, but employs a limestone supply process to increase the alkalinity of seawater, and has high SO ₂ removal efficiency at low pH (acidity) as in the present invention. The indicated absorbent is not described.

The present invention uses an exhaust gas purifying agent containing CKD, a by-product generated in the cement manufacturing process, to remove sulfur oxides present in the exhaust gas, thereby reusing the by-product generated in the cement industry to solve the problem of waste resource treatment and , to provide an exhaust gas purifying agent and an exhaust gas purification method using the same, which can reduce the cost required to maintain alkalinity and prevent environmental pollution by exhibiting a high sulfur oxide removal effect, especially under low pH conditions (acidic).

In order to solve the above problems, the present invention provides an exhaust gas purifying agent containing CKD.

In addition, the exhaust gas purification agent provides an exhaust gas purification agent characterized in that it further comprises water.

In addition, the exhaust gas purification agent provides an exhaust gas purification agent, characterized in that the _{SO 2 conversion rate is 90% or more in acidity of less than pH 7.}

In addition, there is provided a method for purifying exhaust gas comprising a step of preparing a harmful gas absorbent for preparing a harmful substance absorbent by adding the exhaust gas purifying agent to water and stirring, and a contacting step of bringing the exhaust gas into contact with the harmful substance absorbent.

In addition, there is provided an exhaust gas purification method for removing harmful substances from the exhaust gas by contacting the exhaust gas purification agent containing the water with the exhaust gas.

Therefore, the present invention uses an exhaust gas purifying agent containing CKD, a by-product generated in the cement manufacturing process, to remove sulfur oxides present in the exhaust gas, thereby recycling by-products generated in the cement industry to solve the problem of waste resource treatment In particular, it has the advantage of reducing the cost required for maintaining alkalinity and preventing environmental pollution by exhibiting a high sulfur oxide removal effect even under low pH conditions (acidic).

1 is a graph showing the pH and SO _{2 conversion over time of CKD.}
Figure 2 is a graph showing _{the pH, SO 2} conversion rate and NO ₂ conversion rate over time of the exhaust gas purifier.
3 is a schematic process diagram of a bubble reactor in which a reaction for removing harmful substances from exhaust gas is carried out.
4 is a graph showing the results of X-ray fluorescence analysis of the product according to the reaction of _{CKD and SO 2 .}
5 is a graph showing a comparison of changes _{in SO 2} concentration of CKD and NaOH in a pilot exhaust gas purification device.
6 is a photograph of a pilot exhaust gas purification device.
7 is a graph showing _{the SO 2} conversion over time of CKD and sodium hydroxide.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are given to similar parts throughout the specification, and the detailed configuration direction of the present invention will be described with reference to the drawings. Also, throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

The inventors of the present inventors have repeatedly studied to solve the problem that the pH is lowered as the reaction to remove harmful substances in the exhaust gas proceeds in the case of the existing exhaust gas purifier used in the sulfur oxide removal process. As a result, the by-product CKD ( Cement Kiln Dust) was found to maintain the effect of removing sulfur oxides even when the pH is lowered when used as an exhaust gas purifier, leading to the present invention.

Accordingly, the present invention discloses an exhaust gas purifying agent comprising CKD.

The CKD (Cement Kiln Dust) is a by-product in the form of fine powder generated in the cement manufacturing process, which is mainly an environmental pollutant that is released into the atmosphere. It lowers the efficiency of manufacturing equipment.

The component composition of the CKD (Sample 1, 2) was analyzed and shown in Table 1 below.

CKD, a by-product of the cement manufacturing process, exhibits various ionic compositions including Ca in addition to the components in Table 1 above.

1 and 2, it can be seen that the exhaust gas purifying agent of the present invention can be used as a sulfur oxide and nitrogen oxide absorbent. The sulfur oxide is not particularly limited, but _{may be SO, SO 2} , SO ₃ , and the nitrogen oxide is not particularly limited, but NO, NO ₂ , N ₂ O ₃ , N ₂ O, N ₂ O ₄ , N ₂ O ₅ , It may be _{HNO 3 .}

In the exhaust gas purifier, _{a gas containing SO 2} reacts with Ca in the exhaust gas purifier _{to convert SO 2} to CaSO ₃ , and is dissolved in water to be converted _{into SO 3 form.}

When the exhaust gas purifying agent of the present invention is used, an additional process for increasing alkalinity in a state in which the pH is reduced according to the removal reaction of exhaust gas harmful substances such as sulfur oxides and nitrogen oxides is not required, thereby reducing cost and time.

The exhaust gas purifying agent treatment step is a step of discarding after undergoing post-treatment such as an evaporation treatment method, which is an absorbent treatment method generally used in the related industry.

In addition, the exhaust gas purification agent preferably contains 0.1 to 100 g of CKD per 1 L of the water. In the case of the exhaust gas purifier, if CKD per 1 liter of water is more than 100 g, it does not dissolve in water and precipitates, so there is no significant increase in the effect of absorbing sulfur oxides and nitrogen oxides. and nitrogen oxide absorption effect is insignificant. More preferably, the exhaust gas purifying agent preferably contains 0.1 to 50 g of CKD per 1 L of the water. Even more preferably, the exhaust gas purifying agent contains 0.1 to 20 g of CKD per 1 L of the water.

In the case of the exhaust gas purifier, as the amount of CKD per 1 liter of water increases, the absorption effect of sulfur oxides and nitrogen oxides, which are harmful substances in exhaust gas, is improved, and the duration of the absorption effect increases. That is, the time for maintaining high conversion rates of sulfur oxides and nitrogen oxides is increased.

The exhaust gas purifying agent of the present invention _{may have an SO 2} conversion rate of 90% or more at an acidity of less than pH 7.

The present invention provides an exhaust gas purification method comprising the steps of preparing a harmful gas absorbent by adding the exhaust gas purifying agent to water and stirring to prepare a harmful substance absorbent, and a contacting step of bringing the exhaust gas into contact with the harmful substance absorbent.

In addition, there is provided an exhaust gas purification method in which an exhaust gas purification agent containing water is brought into contact with the exhaust gas to remove harmful substances from the exhaust gas.

Since the exhaust gas purification method as described above _{can maintain a high SO 2} removal efficiency even at a low pH, it is possible to maintain the sulfur oxide and nitrogen oxide removal reaction even at an acidity of less than pH 7, thereby reducing the cost used for maintaining the pH.

Hereinafter, the present invention will be described in detail through specific examples.

Experimental Example 1

In order to compare the sulfur oxide removal effect of the exhaust gas purifier and the existing absorbent, 1L of water and 0.1 g of CKD (dust generated from the kiln during the cement manufacturing process) were added to the stirrer, and then 10 at 20℃, 100rpm. stirred for minutes. Then absorber 0.9 L, an absorbing solution temperature 40 ℃, SO ₂ concentration of 500 ppm, a gas flow rate, and injected into a 500 cc / min measuring the SO ₂ concentration in the gas to be passed through the sorbent discharge the bubble reactor (Bubble reactor) of Figure 3 _{The SO 2} conversion according to the reaction time was calculated according to Equation 1 below, and the pH change inside the reactor was measured, and the results are shown in FIGS. 1 and 2 .

[Equation 1]

SO ₂ Conversion(η) =

C _in = Initial SO ₂ concentration (ppm)

C _{out = SO 2} concentration (ppm) after passing through the absorbent

1 is a graph showing the pH and SO ₂ conversion of the exhaust gas purifier, FIG. 2 is a graph showing the pH, SO ₂ conversion, and NO ₂ conversion of the exhaust gas purifier.

Referring to FIG. 2 , in the case of an absorbent in which 1 g/L of CKD is dissolved, almost 100% SO ₂ conversion is exhibited at the initial stage of the reaction. The NO ₂ conversion rate dropped to about 70% at the beginning of the reaction, and then started to gradually increase, reaching about 80% at 180 minutes, showing almost the same conversion rate _{as the SO 2 conversion rate.}

Referring to FIG. 1 , in the case of an absorbent in which 0.1 g/L of CKD was dissolved, a high SO ₂ conversion rate was exhibited at the beginning of the reaction, and the pH decreased sharply after 30 minutes and decreased to pH 2 after 50 minutes, but _{maintaining a high SO 2} conversion rate. Able to know.

Referring to FIG. 2 , in the case of an absorbent in which 1 g/L of CKD is dissolved, almost 100% SO ₂ conversion is exhibited at the initial stage of the reaction. The NO ₂ conversion rate dropped to about 70% at the beginning of the reaction, and then started to gradually increase, reaching about 80% at 180 minutes, showing almost the same conversion rate _{as the SO 2 conversion rate.}

Therefore, the wet sulfur oxide removal method according to the present invention is characterized in that the SO ₂ conversion rate is 90% or more or 95% or more in acidity of less than pH 7 or less than pH 3.

Experimental Example 2

In order to confirm that the exhaust gas purification agent of the present invention can be used in actual field, the exhaust gas purification agent and the NaOH absorbent prepared in Experimental Example 1 were respectively applied to the pilot sulfur oxide removal device of FIG. The sulfur oxide removal performance was compared by measuring the _{SO 2} concentration of the gas discharged through the absorbent while injecting at a _{SO 2} concentration of 50 ppm, a gas flow rate of 162 m ³ /h, and an absorbent injection rate of 6 m ^{3 /h.} 5 is shown.

4 is a graph showing the XRF analysis result of the product according to the reaction of CKD and SO ₂ , and FIG. 5 is a graph showing the comparison _{of SO 2 conversion rates of CKD and NaOH in the pilot sulfur oxide removal device.} 4 and 5, it can be seen that the exhaust gas purifier _{absorbs a large amount of sulfur ions after reacting with the SO 2} gas, and the exhaust gas purifier exhibits sulfur oxide removal performance equivalent to that of the NaOH absorbent actually used in the industry. _{The exhaust gas purifier showed a lower SO 2} emission concentration than the NaOH absorbent at the beginning of the reaction time, _{indicating that the SO 2} absorption rate was superior.

7 is a graph showing _{the SO 2} conversion over time of CKD and sodium hydroxide. Referring to FIG. 7 , it can be seen that when 1 g of CKD is included, SO _{2 conversion rate similar to that of sodium hydroxide is exhibited.} When 5 g of CKD is included, it can be confirmed that the _{SO 2 conversion rate is higher than that of sodium hydroxide.}

Above, preferred embodiments of the present invention have been described in detail with reference to the drawings. The description of the present invention is for illustrative purposes, and those skilled in the art to which the present invention pertains will understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention.

Accordingly, the scope of the present invention is indicated by the following claims rather than the description of the invention, and all changes or modifications derived from the meaning, scope, and equivalent concept of the claims are interpreted as being included in the scope of the present invention. should be

Claims (1)

preparing a harmful gas absorbent at a concentration of 0.1 to 1 g/L by adding a CKD (Cement Kiln Dust) exhaust gas purifying agent to water and stirring; and
Including; injecting the noxious gas absorbent and the exhaust gas into a bubble reactor to contact the noxious gas absorbent with the exhaust gas;
An exhaust gas purification method such that the _{SO 2} conversion rate in the exhaust gas is 95% or more in the condition of pH less than 3 after 50 minutes of the contact.

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