JPH06277442A - Treatment of exhaust gas - Google Patents

Abstract

PURPOSE:To provide an exhaust gas treatment method capable of certainly treating exhaust gas with a small amt. of a neutralizing agent such as slaked lime, facilitating the maintenance of an apparatus and low in running cost. CONSTITUTION:In an exhaust gas treatment method wherein the exhaust gas discharged from a furnace is brought into contact with a slurry of a neutralizing agent such as slaked lime in a reactor, a grinding treatment part by ultrasonic irradiation is arranged to the passage of the slurry of the neutralizing agent from a neutralizing agent slurry tank to the reactor to finely grind the neutralizing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment method capable of efficiently treating exhaust gas containing an acidic component discharged from a refuse incinerator or the like.

[0002]

Exhaust gas from refuse incinerators, etc. contains a large amount of acidic components such as sulfur oxides and hydrogen chloride. Therefore, it is necessary to bring the sulfates into contact with a neutralizing agent slurry such as slaked lime in the reactor. An exhaust gas treatment method is known in which powders of chlorides and chlorides are separated by a bag filter and then released into the atmosphere. However, when a commercially available industrial slaked lime or the like, which is usually commercially available, is used as the neutralizing agent, the reaction between the neutralizing agent and the acidic component in the exhaust gas is a particle because the average particle diameter of the neutralizing agent is as large as 15 to 30 μm. It occurs only near the surface, and most of the neutralizing agent is discharged as unreacted dust. For this reason, it was necessary to add a neutralizing agent in a molar ratio of 2 to 3 times that of the acidic component. Further, since the particle size is large, the spray nozzle is often clogged, which may cause precipitation and blockage during transportation in the pipe.

Therefore, the present inventors reduced the consumption of the neutralizing agent and clogging of the spray nozzle by atomizing the commercially available neutralizing agent such as industrial slaked lime by using some method to increase the specific surface area. We tried to prevent and improve transportation in pipes. However, in the case of a method in which a neutralizing agent such as slaked lime is pulverized using a mechanical pulverizer such as a ball mill or a sandblast type that is usually used, and this is made into a slurry and sprayed, there are some problems as described below. There is. [1] Of the energy consumed during crushing, less than 5% is actually used for crushing, and most of it consumes frictional heat, resulting in poor energy efficiency. Therefore, much power is consumed for crushing. It costs. [2] The crushing part of the crusher is heavily worn due to friction with the neutralizing agent, which requires frequent replacement of the crushing part and other maintenance work. [3] A cooling device dedicated to the crusher is required to prevent overheating due to heat generated mainly by friction during crushing. Due to these various problems, in the case of introducing a mechanical crusher, its running cost and initial equipment investment are high, so that it is difficult to put it into practical use.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and can reliably treat exhaust gas with a small amount of a neutralizing agent such as slaked lime, and the maintenance of the device is easy and the running cost is low. Was completed in order to provide an inexpensive exhaust gas treatment method.

[0005]

The present invention made to solve the above problems is an exhaust gas for removing an acidic component in exhaust gas by contacting the exhaust gas from a furnace with a neutralizing agent slurry such as slaked lime. In the treatment method, a thin tube portion is provided in the flow path of the neutralizing agent slurry such as slaked lime, and the thin tube is irradiated with ultrasonic waves from an ultrasonic oscillator to pulverize the neutralizing agent particles in the slurry to an average particle size of 5 μm or less. Then, the slurry is sprayed to remove acidic components and the like in the exhaust gas.

[0006]

According to the present invention, the neutralizing agent is efficiently atomized by irradiating the flow path of the neutralizing agent slurry such as slaked lime with ultrasonic waves by using the method shown in the preceding stage, and its specific surface area is It can be increased several times. This is because when neutralizer slurry is irradiated with ultrasonic waves of 10 kHz or more, the neutralizer particles in the slurry violently vibrate, causing the particles themselves to self-disintegrate, resulting in the atomization of the particles. . Therefore, it is important that effective ultrasonic waves are effectively applied to the neutralizer particles. Therefore, the ultrasonic wave is preferably 10 kHz or more. This is because the neutralizer particles cannot be effectively vibrated below 10 kHz, and effective pulverization is difficult. The inner diameter of the thin tube provided in the slurry channel is 5
It is preferably -100 mm, particularly preferably 5-50 mm. This is because when the thickness is 5 mm or less, the narrow tube portion is clogged with the neutralizing agent particles, and when the distance between the ultrasonic oscillator and the neutralizing agent particles becomes large, the attenuation of ultrasonic waves in the slurry becomes remarkable. is there.

When the slurry of the neutralizing agent finely divided into particles having an average particle diameter of 5 μm or less by using the method of the present invention is brought into contact with the exhaust gas discharged from the furnace, the reactivity with the acidic component is improved and the neutralizing agent is improved. It is possible to improve the removal rate of acidic components while reducing the consumption amount of. Moreover, since the finely-divided neutralizing agent slurry is unlikely to precipitate, it can be easily transported in the pipe, and it is possible to prevent abrasion of the pipe and clogging of the spray nozzle due to neutralizing agent particles such as slaked lime. Reliability is greatly improved. Moreover, unlike the case of using a mechanical crusher such as a ball mill or a sandblast type, it is not necessary to employ a complicated process such as crushing in advance and then making a slurry. The efficiency of energy required for pulverization is as high as 80% or more, and the heat generated is always naturally cooled because it is through the slurry, and no special cooling device or the like is required. Moreover, since there are no parts to be worn during crushing, there are almost no parts that require replacement. For these reasons, the present invention has many advantages, and the introduction of the present invention makes maintenance easy, and the effects thereof are immeasurable such as running cost and initial capital investment being low.

[0008]

The present invention will be described below in more detail with reference to the illustrated embodiments. FIG. 1 is a flow sheet of the exhaust gas treatment method of the present invention, in which 1 is a furnace for discharging exhaust gas containing an acidic component such as a refuse incinerator, and 2 is exhaust gas of this furnace 1 with a neutralizing agent slurry such as slaked lime. A reactor 3 for contacting the bag, a bag filter 4 for separating powders such as sulfates and chlorides produced by reaction of an acidic component in exhaust gas with a neutralizing agent such as slaked lime, and 4 a chimney. Further, 5 is a tank for neutralizing agent slurry such as slaked lime, and 6 is a pulverization section by ultrasonic waves installed in the flow path of the slurry for neutralizing agent such as slaked lime. In this example, an ultrasonic pulverizer was used for the ultrasonic pulverization processing unit 6, and 1 to 10% of slaked lime slurry most often used in ordinary exhaust gas treatment was used as a neutralizing agent.

FIG. 2 is a structural diagram of the crushing section of the ultrasonic crusher used in this embodiment. As shown in Fig. 2, the pulverizer was equipped with a rod-shaped ultrasonic oscillator with a diameter of 4 mm in a thin tube with the slurry channel narrowed to 10 mm. It is characterized by a method of irradiating sound waves to crush slaked lime particles. In addition, it is not necessary to use a complicated process such as crushing in advance and then making it into a slurry, as in the case of using a mechanical crusher such as a ball mill or a drumstick type, and the efficiency of energy required for crushing is extremely high. Since the generated heat is always naturally cooled because it is through the slurry, no special cooling device etc. is required, so the running cost is low, and there is no part to be worn during crushing, so it seems that replacement is especially required. It is characterized in that it has many advantages such as easy maintenance because there are not many parts. As the slaked lime, the first industrial grade was used.

FIG. 3 shows the particle size distribution of commercial industrial slaked lime, the average particle size of which is about 18 μm and the specific surface area is 6000 cm ^2.
/ cm ³ . On the other hand, FIG. 4 shows the particle size distribution of the slaked lime particles in the slaked lime slurry after passing through the ultrasonic crusher 6, having an average particle size of 3 μm and a specific surface area of 30,000 cm ^2.
/ cm ³ . By irradiating with ultrasonic waves in this way, the average particle size was reduced to about 1/6 and the specific surface area was increased to about 6 times that before pulverization.

FIG. 5 is a graph in which the horizontal axis represents the particle size of slaked lime particles in the slurry and the vertical axis represents the removal rate of hydrogen chloride and sulfur oxides. When a commercially available product having an initial average particle size of 18 μm is used as it is as a slurry, the removal rates are 80% and 70%, respectively, while the slurry according to the present invention, which has been made into fine particles with an average particle size of 3 μm, was used. In this case, it can be seen that their removal rates can be improved to 90% and about 10 to 20%, respectively.

Further, FIG. 6 shows a constant removal rate (vs. HCl 80%, v
2 is a graph showing the molar ratio of slaked lime required to achieve SO _X 70%) on the vertical axis. Initial average particle size 18
When using a commercially available product of μm as it is,
According to the invention, an average particle size of 3
It can be seen that the required molar ratio can be reduced to 1.5, which is half that of the conventional case, when using a slurry with fine particles down to μm. Thus, the slaked lime slurry finely pulverized to 5 μm or less by the ultrasonic pulverizer 6 comes into contact with the acidic component in the exhaust gas in the reactor 2, but the specific surface area of the slaked lime slurry is increased, so that the reactivity is high and the consumption amount is high. Although the amount is small, the removal rate of acidic components can be improved.

[0013]

As described above, in the exhaust gas treatment method of the present invention, the flow path of the neutralizing agent slurry such as slaked lime is irradiated with ultrasonic waves to pulverize the neutralizing agent particles to obtain a fine powder. Since the additive slurry is brought into contact with the exhaust gas, it is possible to achieve a higher removal rate of acidic components than before with a smaller amount of neutralizing agent than before. Further, the exhaust gas treatment method of the present invention has the advantages that maintenance is easy and the running cost is low. Therefore, the present invention contributes greatly to industrial development as an exhaust gas treatment method that solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a flow sheet of an example of the present invention.

FIG. 2 is a cross-sectional view showing the structure of an ultrasonic crusher used in an example of the present invention.

FIG. 3 is a graph showing a particle size distribution of slaked lime particles when a commercially available industrial slaked lime is made into a slurry.

FIG. 4 is a graph showing a particle size distribution of slaked lime particles obtained by making commercially available slaked lime into slurry and irradiating it with ultrasonic waves.

FIG. 5 is a graph showing the relationship between the average particle size of slaked lime in the slurry and the removal rates of hydrogen chloride and sulfur oxides in the exhaust gas.

FIG. 6 is a graph showing the relationship between the average particle size of slaked lime in the slurry and the required molar ratio for the achieved removal rate.

[Explanation of symbols]

1 Reactor for discharging exhaust gas containing acidic components such as refuse incinerators 2 Reactor for contacting exhaust gas of furnace with neutralizing agent slurry such as slaked lime 3 Neutralizer such as slaked lime for acidic components in exhaust gas Bag filter for separating powders such as sulfates and chlorides generated by reaction 4 Chimney 5 Slurry tank of slaked lime etc. 6 Neutralizing agent such as slaked lime Smashing by ultrasonic wave installed in the flow path Processing unit

Claims (2)

[Claims] 1. A method for treating an exhaust gas in which an exhaust gas discharged from a furnace is brought into contact with a neutralizing agent slurry such as slaked lime to remove acidic components and the like in the exhaust gas, a thin tube portion is provided in a channel of the neutralizing agent slurry such as slaked lime. To irradiate ultrasonic waves from an ultrasonic oscillator into the narrow tube to pulverize the neutralizing agent particles in the slurry to an average particle size of 5 μm or less, and spray the slurry to remove acidic components in exhaust gas. An exhaust gas treatment method characterized by: 2. A method for treating an exhaust gas, wherein an exhaust gas discharged from a furnace is brought into contact with a neutralizing agent slurry such as slaked lime to remove acidic components and the like in the exhaust gas. The ultrasonic wave oscillator provided in the thin tube irradiates ultrasonic waves of 10 kHz or more to pulverize the neutralizing agent particles in the slurry to an average particle size of 5 μm or less, and atomize the slurry to produce exhaust gas. An exhaust gas treatment method characterized by removing acidic components and the like therein.