JPS6051533A - Dry removal method for harmful gases - Google Patents

Abstract

PURPOSE:To efficiently remove noxious gas in exhaust gas in a dry system, by simple operation such that an alkali powder is sprayed and mixed in exhaust gas to be reacted with noxious gas, and guiding the treated gas to a dust collector through a blower. CONSTITUTION:Exhaust gas containing noxious gas from a waste material incinerator is guided to a reaction chamber 11 and an alkali powder such as slaked lime is sprayed and mixed in the exhaust gas by compressed air to be reacted with noxious gas such as HCl. This powder mixed gas is guided to a blower 12 where the gas and the powder are again mixed under stirring and reacted. Thereafter, the exhaust gas is guided to a dust collecting apparatus 13 to perform dust collection while the purified gas is exhausted from a chimney 14. By this method, noxious gas can be removed with good efficiency by the reduced addition amount of the alkali powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing harmful gases from exhaust gas generated from a waste incinerator or the like by a dry method.

In the exhaust gas from waste incinerators, etc., I]C8+ SOx
*Contains harmful gas components such as NOx. The emission concentrations of these harmful gases are regulated by laws or ordinances, and these regulatory values have been tightened in recent years.

There are three methods for removing harmful gases: dry, semi-dry, and wet. The dry method has the advantage of having lower equipment costs and easier operation and maintenance than the semi-dry method and the wet method, but has the disadvantage of poor performance in removing harmful gases.

[21J] In the conventional dry method, the exhaust gas from the incinerator 1 is passed through the boiler 2 and is led to the reaction chamber 3, where an alkali powder (for example, Ca(OH)z) is spray-mixed and reacted with the harmful gas. The dust is collected by a dust collector 4 and discharged from a chimney 6 through a blower 5 (suction fan).However, in this method, alkaline powder is entrained in the flow of exhaust gas inside most of the ducts. The relative velocity between the exhaust gas and the alkali powder is low.Therefore, the probability that the alkali powder will encounter harmful gases in the exhaust gas is low, and it is necessary to input excess alkali powder to increase the removal rate of harmful gases.For example, the removal rate In the case of 50 inches, it is necessary to use an alkaline agent in a molar ratio of about 1.0.In addition, in the case of a removal rate of 70%, a molar ratio of about 2.0 is required.

On the other hand, within the normal economical range of the amount of alkali agent used, the limit of the removal rate is 80%, and even if the amount of the alkali agent is increased, the removal rate will not increase much.

For this reason, some systems have reversed the shape of the exhaust gas duct into a U-shape to enhance the mixing effect, but this is not necessarily sufficient.

Another method is to use C as a drug in a ceramic ball.
There is a method in which a packed layer is formed by coating a(OH)2 slurry, and exhaust gas is passed through the packed layer while circulating the ceramic balls to cause the chemical and harmful gas to react. According to this method, since the exhaust gas is passed through the packed bed, the relative velocity between the drug and the exhaust gas is high, and new exhaust gas is easily supplied to the boundary layer. Therefore, the reaction efficiency is high, and even if the d molar ratio is about 2, the removal rate is 90% or more, and the P degree at the outlet is 50 ppm or less. However, the structure of the equipment used to carry out this method is complicated and causes many troubles, and there are problems in that the operating rate is low.

Furthermore, a packed bed of CaQ is formed, and while the CaO in the packed bed is sequentially replaced, the exhaust gas is passed through to remove harmful gases and C from the exhaust gas.
There is a method of reacting with aO.

Also in this method, since the exhaust gas is passed through the packed bed, the relative velocity between CaO and the exhaust gas is high, and new exhaust gas is easily supplied to the boundary layer. Therefore, the reaction efficiency is high, and for example, a removal rate of 9096 or more is obtained at a molar ratio of 25. However, this method also has the problem of a complicated structure and a low operating rate.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to efficiently remove harmful gases using a small amount of alkali powder by increasing the relative velocity between the alkali powder and the harmful gas using a blower. The object of the present invention is to provide a dry method for removing harmful gases that can remove harmful gases and has a simple device structure.

That is, the method of the present invention is characterized in that alkali powder is injected into the exhaust gas containing harmful gases, the powder-containing exhaust gas is introduced to a blower, and then the dust is collected by a collector and then released into the atmosphere.

The present invention will be described below with reference to illustrative embodiments. First, as shown in Fig. 2, exhaust gas generated from a waste incinerator, etc. is led to the reaction chamber 11, where an alkali powder such as slaked lime is sprayed and mixed with pressurized air steam, etc.
1 (reacts with a harmful gas such as JU).The harmful gas mixed with the alkali powder is further guided to the blower 12.
2. The harmful gas and the alkali powder are stirred and mixed again, and the alkali powder is reacted with the harmful gas.

Thereafter, the exhaust gas is guided to a dust collector 13 and discharged from a chimney 14.

In this case, the type of air blower Ft12 may be C1, centrifugal type, or axial flow type, but the centrifugal type is preferable in consideration of ease of installation. In addition, in the case of a centrifugal type, the blades of the blower 12 are of the radial tip type (curved blades 12 made of steel plate).
It can be used as an impeller-type blade with ~30 straight blades attached in the radial direction or as a straight type (impeller-type blade with 6 to 12 straight steel plate blades installed in the radial direction) to prevent exhaust gas with a large amount of dust. It is preferable to do so.

Further, if dust adheres to the blades of the blower 12, a spare fan may be provided to perform switching operation.

Note that the static pressure of the blower 12 may be about 70 to 100 ruAF, and at such a static pressure there is no particular need to consider wear.

In addition, in the method shown in Fig. 24J2, ζl! Between 12 and 1 (44 dust machine will not be installed.

However, according to the present invention, the alkali powder and the harmful gas in the exhaust gas are sufficiently stirred by the centrifugal force inside the blower 12, and the relative velocity between the alkali powder and the harmful gas is increased.

Moreover, inside the blower 12, it is expected that the alkaline powder will be destroyed and a new reaction surface of the alkaline powder will be created. Therefore, the reaction efficiency can be significantly increased compared to the one shown in FIG. 1, and the reaction efficiency can be equivalent to the method of passing the exhaust gas through the circulating packed F1 layer.

In addition, since the blower 12 is used to stir and mix the mixture, the structure is simpler and less troublesome, and the operating rate is higher than that using a packed bed.

In the present invention, the alkali powder spraying location is not limited to the front stage of the blower 12, but may be provided inside the blower KjQ1:z.

As explained above, according to the present invention, since the relative velocity between the alkali powder and the exhaust gas is increased by stirring with the fan,
The reaction efficiency is significantly improved, harmful gases can be removed efficiently with a small amount of alkali powder added, and the method of the present invention can be carried out with a simple configuration of changing the arrangement of the blower and dust collector, making it easy to operate and improve the operating rate. It has remarkable effects such as high

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing a conventional dry removal method for harmful gases;
FIG. 2 is a diagram of a dry method for removing harmful gases showing an example of the present invention. 11... Reaction chamber, 12... Feed F@, 枦, 13...
Dust collector, 14...chimney.

Claims (1)

[Claims] Alkaline powder is sprayed into the exhaust gas containing harmful gases,
A dry method for removing harmful gases, characterized in that the exhaust gas mixed with the powder is introduced into a blower, and then discharged into the atmosphere by a dust collector.