JPH10216470A - Spray method and device of powdery reaction agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably spray a powdery reaction agent to an exhaust gas treating device. SOLUTION: In a method for spraying the powdery reaction agent containing an alkali absorber and a powdery adsorbent in order to remove harmful substance in exhaust gas, the air adjusted relative humidity by adjusting the humidity with a humidity controller 1 (a dehumidifier or a humidifier), is used as transportation air of the powdery reaction agent. In a transportation path 3, the humidity controller 1 for adjusting relative humidity of the transportation air is provided on an upstream side position of a powdery reaction agent feed device 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating an exhaust gas containing harmful gas discharged from a combustion device or the like, and more particularly to a method of purifying an exhaust gas by spraying a powder reactant onto the exhaust gas. The present invention relates to a method and apparatus for spraying an agent.

[0002]

2. Description of the Related Art Exhaust gas discharged from incinerators and the like contains harmful substances such as dust, acid gas, mercury, and dioxins. As a method for treating acidic gases such as HCl and SOx in exhaust gas, a dry method, a semi-dry method, and a wet method have been widely used.

[0003] The dry method is a method in which a powdery alkaline absorbent such as slaked lime is sprayed onto a flue or a reactor, the semi-dry method is a method in which a slaked lime slurry is sprayed on a reactor, and the wet method is a method such as caustic soda. Is sprayed into the reactor.

[0004] Among them, the dry method has recently been able to remove highly acidic gas by using a bag filter as a dust collector. Further, by spraying a carbon-based porous adsorbent such as powdered activated carbon into exhaust gas upstream of the dust collector, mercury and dioxins contained in the exhaust gas can be removed.

[0005] In this dry method, a powdered reactant such as slaked lime or activated carbon is generally quantitatively cut out by a powder supply device, and is passed through a transfer tube by a transfer tube guided by a blower or an air compressor. It is conveyed to the reactor and sprayed.

[0006] Conventionally, in the dry method, the carrier air for carrying the powder is often used without temperature adjustment and without dehumidification.

[0007]

When a powdered reactant such as slaked lime or activated carbon is conveyed by carrier air, if the carrier air is used without humidity control, the process is continuously carried out.
The powder reactant accumulates in the transfer tube by absorbing the water in the transfer air and aggregating, or by the condensation of the water due to the decrease in the temperature of the transfer air in the transfer tube. However, there has been a problem that stable conveyance becomes difficult. In addition, stable transport throughout the year was often not possible due to the effects of seasonal changes in summer and winter, when the temperature and humidity of air differed greatly. Also, when the relative humidity of the carrier air is low and extremely dry,
When transported in a dry state, combustible powder such as activated carbon generates static electricity due to mechanical friction between the activated carbon and the transport tube in the transport tube, and there is a risk that the activated carbon may ignite in the transport tube. Was.

The present invention has been made to overcome these problems, and has the following features.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for spraying a powdered reactant. In order to remove harmful substances in exhaust gas, the present invention relates to a method for spraying a powdered reactant containing an alkaline absorbent and a powdered adsorbent by air conveyance. In the method of spraying exhaust gas,
Air whose humidity is adjusted by a dehumidifier or a humidifier to adjust the relative humidity is used as carrier air for the powdered reactant. In this case, it is possible to use slaked lime as an alkaline absorbent and a carbon-based porous material such as activated carbon as a powder adsorbent.

According to the method of the present invention, since the carrier air is dehumidified by a dehumidifier or the like, the powder reactant does not absorb moisture, and therefore the powder reactant does not agglomerate, and the powder reactant is kept in the transfer tube. Since there is no accumulation, stable conveyance becomes possible.

When the transport air is dried below the allowable value and the humidity is low, the air is humidified by a humidifier or the like. Can be prevented, and further, ignition of the powder reactant can be prevented.

The carrier air is preferably at a temperature between 5 and 50.
In order to use the air whose temperature and humidity are controlled by dehumidifying the air at 80% or more and humidifying it at 20% or less so that the relative humidity is 20 to 80%, and the relative humidity is 20 to 80%. Is good.

When the temperature is 5 to 50 ° C. and the relative humidity is 2
When the carrier air of 0 to 80% is used, the carrier air does not reach the dew point, that is, the powder reactant does not wet due to the aggregation of water, and the powder reactant accumulates in the carrier tube. As a result, stable pneumatic conveyance of the powdered reactant becomes possible. Furthermore, long-term continuous stable air conveyance can be achieved without being affected by seasonal variations in the outside air temperature and relative humidity.

If the temperature is set to 5 ° C. or lower, the air tends to reach the dew point, that is, moisture may condense, which is not preferable. When the temperature is 50 ° C. or higher, the temperature difference from the outside temperature of the transfer tube becomes large, and in the process of transferring the powdered reactant, the temperature of the transfer air decreases due to the influence of the outside air temperature, and water condensation occurs due to the temperature decrease. Therefore, it is not preferable.

When the relative humidity is set to 20% or less, the carrier air is extremely dried, so that the combustible powder such as activated carbon easily generates a large amount of static electricity due to friction, and increases the risk of ignition of the powder due to the static electricity. Is not preferable because
It is not preferable because the powder easily aggregates due to the electrostatic force. If the relative humidity is set to 80% or more, even if the temperature is reduced to a small extent, the water will aggregate, which is not preferable. This is because in the transfer process, the temperature of the transfer air in the transfer tube is changed due to the influence of the outside air temperature and the change in the pressure inside the transfer tube due to the shape of the transfer tube.

Next, the present invention relates to an apparatus for performing the above method, wherein a flue or exhaust gas treatment apparatus and a conveying air supply apparatus are connected by a conveying path, and a powder reactant supplying apparatus is provided in the conveying path. In the apparatus, a humidity control device for adjusting the relative humidity of the transport air is provided at a position upstream of the powder reactant supply device on the transport path.

[0017]

FIG. 1 shows an embodiment of a method and apparatus for spraying a powdered reactant according to the present invention.

In FIG. 1, reference numeral 1 denotes a humidity controller, 2 a powder reactant silo as a powder reactant supply device and a cutting device, 3 a transport tube, 4 a blower, and 5 a flue or exhaust gas treatment device.

In the embodiment shown in FIG. 1, the blower 4 is connected to a flue or exhaust gas treatment device 5 by a conveyance tube 3 as a conveyance path, and conveys air to the flue or exhaust gas treatment device 5. sending. Transfer tube 3
Is connected to a powder reactant supply device 2 and a humidity controller 1 upstream of the device.

Exhaust gas discharged from an incinerator or the like (not shown) contains harmful substances such as dust, acid gas, mercury, and dioxins. As for these harmful substances, a powdered reactant containing slaked lime as a powdered alkaline absorbent and activated carbon as a powdered adsorbent is cut out by the powdered reactant supply device 2, and is cut out from a flue or exhaust gas treatment device 5.
To separate and remove from exhaust gas.

Therefore, in the present invention, when the above-mentioned powdered reactant is sprayed onto the flue or the exhaust gas treatment device 5, first, the carrier air discharged from the blower 4 is introduced into the humidity controller 1. The humidity of the carrier air is adjusted by the humidity controller 1 so that the temperature is in the range of 5 to 50 ° C. and the relative humidity is 20 to 80%. The carrier air after leaving the humidifier 1 transports the powdered reactant cut out from the powdered reactant supply device 2 in the transport tube 3 and introduces and sprays it into the flue or exhaust gas treatment device 5.

The blower 4 for generating the conveying air includes:
Other means may be used as long as an air flow rate capable of transporting the powder reactant can be secured.
Or the like may be used.

As the carrier gas, indoor and outdoor air can be used. It is conceivable to use an oxygen-free gas such as nitrogen or carbon dioxide, but it is not suitable because it is more expensive than air.

The humidifier 1 may have both functions of dehumidification and humidification, or may be a combination of a dehumidifier and a humidifier, and may be of any type such as an air-cooled type, a water-cooled type, and a desiccant type. Desirably, it is desirable to be able to display the temperature and the relative humidity and to control the temperature and the relative humidity continuously. If the temperature and the relative humidity cannot be controlled, as shown in FIG. 2, a thermometer 6 and a relative humidity meter 7 are separately installed, and an electric signal 8 of these indicated values is transmitted to the humidity controller 1 for control. Is also good. In addition, when a dehumidifier is used instead of the humidity controller 1, humidification cannot be performed. However, when the humidity of the conveying air is high, dehumidification is effective.

Since the carrier air used for carrying the powdered reactant is a carrier air having a temperature of 5 to 50 ° C. and a relative humidity of 20 to 80%, the carrier air does not reach the dew point. The powder reactant does not wet due to the aggregation of the powder reactant, and the powder reactant does not accumulate in the transfer tube 3, so that the stable pneumatic transfer of the powder reactant is possible. Furthermore, long-term continuous stable air conveyance can be achieved without being affected by seasonal variations in the outside air temperature and relative humidity.

If the temperature is 5 ° C. or lower, the air tends to reach the dew point, that is, moisture may condense, which is not preferable. When the temperature is 50 ° C. or more, the temperature difference from the outside temperature of the transfer tube becomes large, and the temperature of the transfer air decreases due to the outside air temperature in the process of transferring the powdered reactant, and the condensation of moisture due to the temperature decrease occurs. Therefore, it is not preferable. Desirably, the temperature of the carrier air is in the range of 5 to 50C, and the upper limit of the carrier air is 10C higher than the outside air temperature. With this setting, the difference between the temperature of the outside air and the temperature of the carrier air is reduced, and in the carrying process, the carrier air is cooled by the influence of the outside air, so that the water in the carrier air can be prevented from condensing.

When the relative humidity is set to 20% or less, the carrier air is extremely dried, so that the combustible powder such as activated carbon easily generates a large amount of static electricity due to friction and increases the risk of ignition of the powder due to the static electricity. Is not preferable because
It is not preferable because the powder easily aggregates due to the electrostatic force. When the relative humidity is 80% or more, even if the temperature is reduced slightly, the water is aggregated, which is not preferable. This is because, in the transfer process, the temperature of the transfer air in the transfer tube 3 changes due to the influence of the outside air temperature and the pressure change in the transfer tube 3 due to the shape of the transfer tube.

The powdered reactant supply device 2 is filled with powdered slaked lime as an alkaline agent for removing acid gas. The number of powdered reactant supply devices 2 is not limited to one, but may be two or more in series or in parallel. In this case, one may be filled with slaked lime and the other with powdered activated carbon.

[0029] The powder reactant is HCl or SOx in the exhaust gas.
Powdered slaked lime can be used as an alkali agent for neutralizing and removing acidic components such as calcium carbonate, but other alkali agents may be used as long as powders such as calcium carbonate can be carried by air. In addition, the powdered reactant also uses powdered activated carbon as an adsorbent for removing mercury and dioxins in exhaust gas, but if it is a powdered carbon-based porous adsorbent, it has a high level of adsorption performance, Other adsorbents may be used. Further, the powdered reactant may be used as an auxiliary, such as a powdered catalyst or a stripping agent such as powdered diatomaceous earth.

The material of the transport tube 3 is not particularly limited.
A flexible material such as polyethylene, which generates less static electricity due to friction between the powder and the tube, can stably convey with less powder attached to the tube. In order to suppress the generation of static electricity, a grounding tube may be used. However, when the humidity of the conveying air is as low as 20% or less, it is needless to say that the humidity needs to be humidified to 20% or more as shown in the present invention. Further, since the present invention regulates the temperature and humidity of the transport air in consideration of the influence of the outside air temperature, it is not necessary to apply a heat insulating agent or the like to the transport tube 3 to keep the temperature.

The flow rate of the carrier air by the blower 4 is affected by the powder particle size of the powdered reactant and the shape of the carrier tube 3. Should be given. For example, in the case of powdered slaked lime or activated carbon, a carrier air flow rate of 10 m / s or more may be given.

The mounting position of the tip of the transfer tube, that is, the spray position of the powdered reactant is preferably in the flue or the exhaust gas treatment device upstream of the exhaust gas treatment device in the existing facility, but is not particularly limited because it is not the main object of the present invention. is not.

[0033]

【Example】

<Example 1> The test results obtained by carrying out the method of spraying a powdered reactant according to the present invention are shown.

FIG. 4 is a diagram showing the result of examining the amount of the powdered reactant remaining in the transfer tube by changing the relative humidity of the transfer air.

FIG. 5 is a diagram showing the result of examining the amount of static electricity generated due to friction between slaked lime and the transfer tube by changing the relative humidity of the transfer air.

The test conditions were as follows: powdered slaked lime (JIS special name) was used as the powder reactant, and the transfer tube was made of polyethylene. The transfer air temperature was 20 ° C, the outside air temperature was 18 ° C, and the transfer air speed was 20 m / m. s, transfer tube length 3
The length was set to 0 m, and the transfer tube was provided with gentle curved portions at five locations.

FIG. 4 shows that the amount of slaked lime remaining in the transfer tube is extremely small when the relative humidity is in the range of 20 to 80%, and that the slaked lime can be stably transferred in the same humidity range. Is shown.

According to FIG. 5, when the relative humidity is 20% or less, slaked lime and the tube generate extremely large amounts of static electricity.
% Or more, the amount of static electricity generated stably decreases,
This shows that slaked lime can be transported stably in the range of the relative humidity of 20% or more.

When the relative humidity is 20% or less, the amount of slaked lime remaining (deposited amount) in the transport tube increases because the humidity is extremely low, and a large amount of static electricity is generated due to friction between the slaked lime and the transport tube. This is because agglomeration of the slaked lime powder has occurred.

When the relative humidity is 80% or more, the amount of slaked lime remaining in the transfer tube is increased because the slaked lime powder absorbed a large amount of water in the transfer air because the humidity was extremely high. This is because agglomeration of the slaked lime powder occurred due to condensation of moisture due to a decrease in the temperature of the carrier air due to pressure fluctuations in the tube and the like.

It should be noted that the same results as in FIG. 4 were obtained in the range of the carrier air temperature of 5 to 50. Further, the same test was performed on the powdered activated carbon.

<Example 2> Next, the test results obtained by carrying out the spraying method of the powdered reactant according to the present invention in a garbage incineration plant over a long period of time are compared with the test results of the comparative example and shown in Table 1. .

As the test conditions in Example 2, the humidity conditioner shown in FIG. 1 was used, and the powdered reactant was powdered slaked lime (JIS special number).
The transfer tube is made of polyethylene and the transfer air speed is 20 m / s and the transfer tube length is 5
The length was set to 0 m, and the transfer tube was provided with a gentle curved portion at several places for the sake of the test, and had a vertical drop of 5 m from the discharge port to the spray port by the blower. Furthermore, a continuous test was performed for two weeks each in June, when the humidity was high in summer and in dry January in winter.

The test conditions of the comparative example were the same as in Example 2. However, in the comparative example, a powder reactant spraying device without a humidity controller shown in FIG. 3 was used as a conventional example.

In the test, the discharge pressure of the blower was used as an index for stable transport of the powdered reactant by the transport air. The discharge pressure of the blower indicates the degree of deposition of the powdered reactant in the transfer tube, that is, the degree of clogging in the transfer tube. When the discharge pressure of the blower becomes twice the initial value, it is determined that the blower is closed. When it was determined that the tube was clogged, the tube was immediately restored by cleaning the tube, and the test was continued.

[0046]

[Table 1] Comparison between Example 1 and Comparative Example (Confirmation test of blockage due to slaked lime in transport tube) Note: When the blower discharge pressure became twice the initial value, it was closed.

From Table 1, it was confirmed that Example 1 in which the present invention was carried out did not deposit slaked lime in the transport tube and could achieve stable slaked lime transport in the two-week period in both summer and winter. Further, in Example 2, a two-month test was performed. As a result, no blockage was observed, and stable conveyance of slaked lime was confirmed. Similar results were obtained when powdered activated carbon was used. In addition, ignition of the powder due to generation of static electricity did not occur.

That is, the present invention is carried out, that is, the temperature of the carrier air is 5 to 50 ° C. and the relative humidity is 2
It has been found that by adjusting to 0 to 80% using a humidity controller, long-term continuous stable transport of the powdered reactant without deposition of the powdered reactant in the transport tube can be obtained.

[0049]

According to the method of the present invention, a powdered reactant such as slaked lime or activated carbon is transported through a transport tube by a transport air whose temperature and humidity have been adjusted through a humidity controller.
Clogging of the powder in the transfer tube can be prevented, and stable transfer can be performed for a long period of time. That is, by a simple method of adjusting the temperature and relative humidity of the transport air using a humidity controller, the maintenance work for eliminating the clogging or blockage in the conventional transport tube can be omitted, and the transport air uses air. Provides an inexpensive, simple, and stable method for spraying powdered reactants, which is inexpensive, does not require heat retention in the transfer tube, and does not require additional measures to avoid ignition of powder due to the generation of static electricity. it can.

According to the apparatus of the present invention, the method of the present invention can be easily implemented.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a method for spraying a powdered reactant according to the present invention.

FIG. 2 is a view showing another embodiment of the method for spraying a powdered reactant according to the present invention, which is provided with a thermometer and a hygrometer separately from FIG.

FIG. 3 is a view showing a conventional method of spraying a powdered reactant.

FIG. 4 is a diagram showing a result of examining a relationship between a relative humidity of carrier air and an amount of powdered slaked lime remaining (accumulating) in a carrier tube.

FIG. 5 is a diagram showing a result of examining a relationship between a relative humidity of carrier air and an amount of generated static electricity due to friction between powdered slaked lime and a carrier tube.

[Explanation of symbols]

 Reference Signs List 1 Humidity control device (humidity control device) 2 Powder reactant supply device 3 Conveyance path (conveyance tube) 5 Flue or exhaust gas treatment device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01D 53/68 B01D 53/34 134A 53/64 136Z B01J 20/20 (72) Inventor Masaru Ayukawa 1-chome, Marunouchi, Chiyoda-ku, Tokyo No. 2 Nihon Kokan Co., Ltd.

Claims (4)

[Claims] 1. In order to remove harmful substances in exhaust gas,
In a method in which a powder reactant containing an alkaline absorbent and a powder adsorbent is sprayed on exhaust gas by air conveyance, the air whose relative humidity has been adjusted by controlling the humidity with a dehumidifier or a humidifier is used as the carrier air for the powder reactant. A method for spraying a powder carrier, comprising: 2. The method according to claim 1, wherein the alkaline absorbent is slaked lime and the powder adsorbent is a carbon-based porous material such as activated carbon. 3. The carrier air is air having a temperature of 5 to 50 ° C. and a relative humidity of 20 to 80%.
The method of spraying a powdered reactant according to claim 1, wherein the air is dehumidified when the amount is not less than 20%, and the air whose temperature is controlled by controlling the humidity is used when the amount is not more than 20%. 4. A method in which a flue or exhaust gas treatment device and a conveying air supply device are connected by a conveying path, and a powder reactant supplying device is provided on the conveying path. A spraying device for a powdered reactant, wherein a humidity control device for adjusting the relative humidity of transport air is provided at an upstream position.