KR19990050193A - Continuous processing method of air pollutant in combustion flue gas and apparatus used therein - Google Patents

Abstract

It is an object of the present invention to provide a method for continuously treating air pollutants in flue gas generated in various combustors and a continuous treatment apparatus used therein.

In the treatment method of the present invention for achieving the above object, the combustion flue gas is cooled to room temperature, and then passed through the activated carbon layer to remove SOx in the flue gas, dehumidifying the moisture in the flue gas, and then dehumidified flue gas to the combustion flue. Heated to a temperature of 70-150 ° C. by gas, and then passed through an activated carbon layer with a reducing agent to remove NOx in exhaust gas; And,

The continuous processing apparatus 100 used for this is located between the combustor 11 and the cooler 30, the heat exchanger 20 configured to pass the dehumidified exhaust gas, the cooler 30 for cooling the exhaust gas to room temperature, the upper portion Is connected to the first activated carbon supply tank 41 and the lower part is connected to the first activated carbon recovery tank 43 and the sulfuric acid storage tank 44 while the first reactor 40 having the activated carbon layer 41 embedded therein, The dehumidifier 50 for removing moisture in the flue gas treated in the first reactor and the activated carbon layer 61 through which the hot flue gas flowing through the dehumidifier 50 and the heat exchanger 20 pass are inherent. A second reactor 60 connected to the second activated carbon supply tank 61 and the reducing agent supply tank 65 and connected to the second activated carbon recovery tank 63 and the chimney 70 through which exhaust gas is discharged; It is configured to include.

Description

Continuous processing method of air pollutant in combustion flue gas and apparatus used therein

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously treating air pollutants in flue gas generated in various combustors and a continuous treatment apparatus used therein.

Recently, various types of combustors including waste incinerators, steel mills, sintering furnaces, and the like, along with sulfur compounds and nitrogen oxides, have been known to generate compounds such as dioxins and furans, which are highly toxic substances. In the process of purifying air pollutants present in the combustion flue gas, sulfur compounds and nitrogen oxides are the main removal targets. This has been used mainly.

For example, FIG. 1 shows a selective reduction catalyst device 10 for selectively reducing and removing nitrogen oxides using a catalyst. In the selective reduction catalyst method, as shown in FIG. 1, the exhaust gas generated in the combustor 11 and maintained at a temperature of about 200 ° C. is passed through a heat exchanger 12 to raise the temperature to about 250 ° C., and then the temperature is increased. The exhaust gas is heated to a temperature of about 350 ° C. by the heater 13, and the hot exhaust gas is reacted in the catalytic reactor 14 with the reducing agent introduced from the reducing agent supply tank 15 to selectively remove nitrogen oxides, and then treated. Due to the exhaustion of the exhaust gas, the exhaust gas newly introduced from the heat exchanger 12 is heated and discharged to the chimney 17. The selective catalytic reduction method is useful for the selective removal of nitrogen oxides, but the reaction temperature is high, requires a lot of energy and has a relatively low removal efficiency of sulfur dioxide.

On the other hand, in addition to the above method, there is a method of treating air pollutants in a single process, which is a method of removing contaminants by reacting with gas using activated coke as an adsorbent (VGB Kraftwerkstechnik 72, p.572, 1992, No .7). However, this method has a disadvantage in that the volume of the adsorbent layer must be very large because the space velocity cannot be maintained at 500 / hr or more during the reaction in the adsorption tower (NKK Technical Review No. 74, p. 53, 1996).

The present invention has been proposed for the improvement of the conventional activated coke process, and the continuous treatment of volatile organic compounds, sulfur compounds, nitrogen compounds sequentially and continuously, but can be treated with high efficiency due to the improvement of the space reaction rate of continuous treatment method The purpose is to provide.

Another object of the present invention is to provide an apparatus that can be used in such a continuous processing process.

1 is a block diagram of a flue gas continuous processing apparatus that is compatible with a conventional selective reduction catalyst

2 is a configuration diagram of the exhaust gas continuous treatment apparatus of the present invention

3 is a detailed structural diagram of the reactor of FIG.

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

100 ..... Continuous Processing System 11 ..... Combustor

20 ..... Heat Exchanger 30 ..... Chiller

40 ..... First Reactor 50 ..... Dehumidifier

60 ..... Second Reactor 70 ..... Chimney

In order to achieve the above object, the present invention provides a method for treating an air pollutant in a combustion flue gas.

Cooling the combustion flue gas to room temperature;

Passing the cooling exhaust gas through the activated carbon layer to remove SOx in the exhaust gas;

Dehumidifying moisture in the exhaust gas from which SOx is removed;

Heating the dehumidified exhaust gas to a temperature of 70 to 150 ° C. by the combustion exhaust gas;

Passing the heated exhaust gas through a activated carbon layer together with a reducing agent to remove NOx; And

Exhausting flue gas from which NOx has been removed; It relates to an air pollutant continuous treatment method of a combustion flue gas comprising a.

In addition, the present invention is an apparatus for treating air pollutants in the combustion flue gas,

A heat exchanger located between the combustor and the cooler, the heat exchanger configured to pass dehumidified exhaust gas;

A cooler cooling the exhaust gas introduced from the heat exchanger to room temperature;

A first reactor positioned subsequent to the cooler, the upper portion of which is connected to the first activated carbon supply tank side and the lower portion of which is connected to the first activated carbon recovery tank and sulfuric acid storage tank while having an activated carbon layer embedded therein;

A dehumidifier positioned subsequent to the first reactor to remove moisture in the exhaust gas treated in the first reactor; And

The second reactor is connected to the activated carbon layer through which the hot exhaust gas flowing through the dehumidifier and the heat exchanger passes, the upper portion is connected to the second activated carbon supply tank and the reducing agent supply tank, and the lower portion is connected to the second activated carbon recovery tank and the chimney from which the exhaust gas is discharged. ; It relates to an air pollutant continuous processing apparatus of a combustion flue gas comprising a.

First, the continuous processing apparatus of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 2, the combustion exhaust gas continuous processing apparatus of the present invention includes a heat exchanger 20, a cooler 30, a first reactor 40, a dehumidifier 50, and a second reactor 60; It is configured to include.

The heat exchanger 20 is located between the combustor 11 and the cooler 30, and is configured to pass through the dehumidified exhaust gas. The heat exchanger 20 lowers the concentration of the gas discharged from the combustor 11 to facilitate the removal of sulfur compounds and volatile organic compounds (hereinafter, only 'VOC') and at the same time removes the VOCs and sulfur compounds. This serves to easily remove the nitrogen oxides by raising the temperature of the completed gas, that is, the dehumidified gas. The heat exchanger 20 of the present invention may use a gas-gas heat exchanger.

In addition, the cooler 30 serves to facilitate the removal of VOC and sulfur compounds by further cooling the exhaust gas that is primarily cooled in the heat exchanger 20 to near room temperature. The cooler 30 of the present invention may be a gas cooler that is usually used.

The first reactor 40, which is located after the cooler 30, has an upper portion connected to the first activated carbon supply tank 41 side, and a lower portion thereof in the first activated carbon recovery tank 43 and sulfuric acid storage tank 44. Connected. In addition, the activated carbon layer 41 is filled therein to remove VOC and sulfur compounds. 3 shows the detailed structure of the first reactor 40. As shown in FIG. 3, a first activated carbon supply tank 42 is provided at an upper portion of the first reactor 40 so that activated carbon is continuously supplied through a feed feeder 46. As the activated carbon is continuously supplied, the first activated carbon recovery tank 43 is installed at the lower portion of the first reactor 40 so that the activated carbon can be continuously removed. The upper and lower sides of the activated carbon layer filled in the first reactor 40 are provided with network meshes 47 and 48 having a network structure and configured to allow exhaust gas to pass therethrough. Sulfur compounds are reacted by activated carbon to generate sulfuric acid from the water vapor and oxygen in the flue gas passing through the activated carbon layer. At this time, sulfuric acid storage tank 44 capable of discharging sulfuric acid, which is a by-product of the reaction, under the netting 48. Is disposed on the lower side of the first reactor (40). In addition, the exhaust gas from which the VOC and sulfur compound reactions are removed is discharged to the dehumidifier 50 side.

The dehumidifier 50 is positioned after the first reactor 40 to remove moisture in the exhaust gas treated in the first reactor. Dehumidifier 50 of the present invention can be used for all kinds of dehumidifiers commonly used as long as the part in contact with the gas is made so as not to be affected by corrosion.

The continuous processing apparatus 100 of the present invention is configured such that exhaust gas at room temperature exiting the dehumidifier 50 is introduced into the second reactor 60 through the heat exchanger 20.

Like the first reactor 40, the second reactor 60 is filled with an activated carbon layer 61 through which a high temperature flue gas heated in the heat exchanger 20 passes, and a second activated carbon supply tank at the top thereof. 61 is provided, and the second activated carbon recovery tank 63 is provided in the lower part. However, the second reactor 60 is provided with a reducing agent supply tank 65 in the upper portion to remove the nitrogen compound in the exhaust gas, the lower side is connected to the chimney 70 so that the treated exhaust gas is discharged after the reaction. Like the first reactor 40, the second reactor 60 is continuously supplied with activated carbon, and the used activated carbon is continuously discharged by the input amount. Unlike the first reactor 40, the second reactor 60 of the present invention is more preferably used in a cartridge type reactor. In this case, the exhaust gas is suitably configured to be drawn in from the lower part of the cartridge reactor and discharged to the upper side.

Hereinafter, the exhaust gas continuous treatment method of the present invention using the above-described continuous treatment apparatus will be described in detail.

As shown in FIG. 2, the flue gas generated in the combustor 11 is usually maintained at about 200 ° C., when passing through the heat exchanger 20, the temperature is lowered to about 150 ° C., and then cooled to room temperature in the cooler 30. In other words, the VOC and sulfur compounds in the flue-gases generated in the combustion process are easily removed in the presence of water to some extent, and more easily at room temperature than at high temperatures.

Passing the exhaust gas cooled to room temperature through the activated carbon layer in the first reactor 40 removes SOx in the exhaust gas. That is, when sulfur compound reacts with activated carbon from water vapor and oxygen in flue-gas, SOx is removed like sulfuric acid. At this time, the sulfuric acid generated as a by-product is discharged to the lower side of the first reactor 40 can be recovered into the sulfuric acid storage tank (44).

Then, the exhaust gas from which the SOx is removed dehumidifies moisture in the exhaust gas in the dehumidifier 50 and raises the dehumidified exhaust gas to a temperature of about 70 to 150 ° C. In order to increase the efficiency of removing nitrogen oxides in the second reactor (60), sulfur compounds are easily removed at room temperature with some moisture, but nitrogen oxides in the exhaust gas are easier to remove as the humidity is kept as low as possible at high temperatures. Dehumidification process and heating process are required.

Specifically, when the absolute humidity of the exhaust gas is maintained at less than 1%, the removal efficiency of the nitrogen oxides is improved. When the absolute humidity of the gas is 1% or more, the conversion rate of the reduction reaction of the nitrogen oxides decreases rapidly depending on the humidity, which is not preferable.

In addition, it is preferable to maintain the temperature of the exhaust gas to about 70 ~ 150 ℃, in the case of the present invention is characterized in that the temperature increase of the flue gas reacted in the second reactor 60 uses the sensible heat of the heat exchanger (20). In this case, when the reaction temperature is 70 ℃ or less, the nitride is generated by the reaction with the reducing agent may shorten the life of the activated carbon, and when it is maintained at 150 ℃ or more it becomes difficult to adsorb nitrogen oxide to the activated carbon to the nitrogen oxide It is difficult to remove because the reduction does not occur actively on the surface of activated carbon.

Passing the heated exhaust gas along with the reducing agent through the activated carbon layer increases the NOx removal efficiency in the exhaust gas. At this time, the input amount of the reducing agent supplied to the activated carbon is preferably adjusted to supply 1 to 1.5 times the concentration of nitrogen oxides in the flue gas. When the concentration of the reducing agent is less than one times the concentration of nitrogen oxides in the flue gas, the conversion rate of nitrogen oxides is lowered because it is not sufficiently reacted in the reduction reaction in the second reactor 60 which is reacted at the same amount as the nitrogen oxides. Even if a reducing agent of more than twice the temperature is added, there is no effect of increasing the reduction reaction, and thus secondary pollution is caused by the discharge of the reducing agent that does not participate in the reaction. In the case of the present invention, ammonia is preferable as the reducing agent.

In addition, in the case of the present invention, the activated carbon is preferably carried out with activated coke having a specific surface area of 200 m ² / g or more at a space velocity of 500 / hr.

As described above, the exhaust gas continuous treatment process of the present invention basically removes sulfur compounds and nitrogen compounds in order to adsorb corresponding pollutants, and in particular, 90% or more of nitrogen oxides having a concentration of 400 ppm or more at a space velocity of 500 / hr or more It can be processed. For example, a space of 500 / hr in a 70-150 ° C. second reactor 60 filled with nitrogen oxide having an oxygen concentration of at least 5% and a concentration of 400 ppm and an activated coke having a specific surface area of 200 m ² / g or more. If passed at a rate, more than 90% of the nitrogen oxides can be removed.

The exhaust gas from which NOx is removed is removed from the air pollutant and finally discharged to the chimney 70. In order to use the above process to remove contaminants in a specific combustion flue gas, it is necessary to remove solid phase substances such as dust contained in the discharged gas in advance to extend the life of activated coke in each reactor. It is preferable to use a conventional bag filter, an electrostatic precipitator, a wet dust collector or the like. Thus, the capacity of the heat exchanger or the cooler may be determined according to the temperature of the pretreated exhaust gas, and according to the pressure of the exhaust gas, it is preferable to install a blower to maintain the gas flow smoothly if necessary.

As described above, unlike the conventional flue gas treatment method, the present invention can sequentially remove volatile organic compounds, sulfur compounds, and nitrogen compounds at a relatively low temperature as compared to the selective catalyst reduction method in a single process. While processing, there is an effect that can be processed with high efficiency due to the improvement of the space reaction speed.

Claims (7)

In the method of treating the air pollutants in the combustion flue gas, Cooling the combustion flue gas to room temperature; Passing the cooling exhaust gas through the activated carbon layer to remove SOx in the exhaust gas; Dehumidifying moisture in the exhaust gas from which SOx is removed; Heating the dehumidified exhaust gas to a temperature of 70 to 150 ° C. by the combustion exhaust gas; Passing the heated exhaust gas through a activated carbon layer together with a reducing agent to remove NOx; And Exhausting flue gas from which NOx has been removed; Air pollutant continuous treatment method of combustion flue gas comprising a The method of claim 1, wherein the moisture in the exhaust gas from which the SOx is removed in the dehumidification step is dehumidified to less than 1% absolute humidity. The continuous treatment method according to claim 1, wherein the input amount of the reducing agent in the NOx removal step is controlled to be adjusted to 1 to 1.5 times the concentration of nitrogen oxides in the exhaust gas. The method of claim 3, wherein the reducing agent is ammonia. The continuous processing method according to claim 1, wherein the activated carbon is introduced into a activated coke having a specific surface area of 200 m ² / g or more at a space velocity of 500 / hr. In the apparatus for treating air pollutants in combustion flue gas, A heat exchanger (20) located between the combustor (11) and the cooler (30) and configured to allow dehumidified exhaust gas to pass therethrough; A cooler 30 for cooling the exhaust gas introduced from the heat exchanger 20 to room temperature; Subsequent to the cooler 30, the upper portion is connected to the first activated carbon supply tank 41 side and the lower portion is connected to the first activated carbon recovery tank 43 and sulfuric acid storage tank 44, while the activated carbon layer 41 therein. A first reactor 40 incorporating); A dehumidifier (50) positioned subsequent to the first reactor (40) to remove moisture in the flue gas treated in the first reactor; And The activated carbon layer 61 through which the high-temperature exhaust gas flowing through the dehumidifier 50 and the heat exchanger 20 passes is embedded, and an upper portion thereof is connected to the second activated carbon supply tank 61 and the reducing agent supply tank 65. A lower portion of the second reactor 60 connected to the second activated carbon recovery tank 63 and the chimney 70 through which exhaust gas is discharged; Air pollutant continuous processing device of the combustion flue gas, characterized in that comprising a The continuous processing apparatus according to claim 6, wherein the second reactor (60) is a cartridge type reactor.