JPS59153200A - Method of cleaning off-gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying exhaust gas. More specifically, the present invention relates to a method for purifying exhaust gas comprising: irradiating the exhaust gas containing NOx and/or 802 with ionizing radiation in the presence of powder having adsorbed water on its surface.

Some of the inventors have already filed a patent application for an exhaust gas purification method in which NOx and/or S02 are recovered as solid products by adding an alkaline substance, such as ammonia. [Patent Application No. 1973-106701 (
Japanese Patent Publication No. 50-39377) 1. Exhaust gas adjustment method by adding alkaline substance to exhaust gas in radiation irradiation exhaust gas purification process"] The present invention is a further improvement of this conventional method.

Therefore, the main purpose of the present invention is to maintain the copper removal and desulfurization rate even at temperatures of 120°C or higher, thereby effectively reducing the exhaust gas containing NOx and/or S02, such as coal combustion exhaust gas. According to the present invention, a powder having adsorbed water on the surface is added to an exhaust gas containing NOx and/or S02, and then the exhaust gas is purified by irradiation with separable radiation glands. Ru.

The powder used in carrying out the present invention is preferably one having an adsorbed water amount of 2.5 to 10 times the dry powder weight at 100°C. Examples include white carbo/(fine hydrated silica) bentonite, acid clay. Hereinafter, the structure and effects of the present invention will be specifically explained with reference to FIG. 1, which shows one aspect of the process of the present invention.

In Figure 1, if powder is not added, NOx from the emission source
, SO□ decreases due to the action of the electron beam from the electron beam irradiation device placed inside the irradiation chamber.

This mist changes into NO2, nitric acid, and sulfuric acid mist,
It is collected by a dust collector and removed from the exhaust gas. The exhaust gas from which NOx and S02 have been removed in this way is
A blower releases it into the atmosphere from the chimney.

As mentioned above, when the exhaust gas is irradiated with an electron beam in the irradiation container, the radiation chemical reaction of the mixed gas of N2.02°N20, which is the main component of the exhaust gas, produces o atoms and OH radicals.
H02 radicals are generated, and these chemical species oxidize No, which accounts for more than 95% of the NOx in the exhaust gas, and S02, and finally nitric acid, t! #, becomes acid mist (reaction 1υ and (wholesale.

0H1O 802□ SO3-embryo-)12 SO4(21 reaction (
In Il, the rate of the first stage oxidation process (No→NO□) is very high, while the second stage oxidation process (NO2→H
The speed of N03) is small.

In Figure 1, a powder addition port is installed in front of the entrance of the irradiation container.
A powder addition device sprays and adds powder at a set flow rate to a powder exhaust gas containing adsorbed water on one surface, thereby adjusting the exhaust gas in which a fixed concentration of powder is dispersed.

When this is irradiated with an electron beam, the N02 generated by the rapid oxidation reaction of 1 reaction + 11 quickly reacts with the adsorbed water on the powder surface to become nitric acid. (3)).

3NO2+ )120-→2HNO3+No (31
This gift 1 skin response (as shown by 31, N(
Some of the J2 becomes NO and is re-emitted into the gas phase.

Like the NO originally contained in the exhaust gas, this No is quickly oxidized to N (J2) by reaction (1) that occurs under electron beam irradiation, and can be fixed in the adsorbed water. The nitric acid mist produced in step 11) can also be easily fixed in the adsorbed water.

On the other hand, the sulfuric acid mist and some S02 generated by reaction (2) can also be fixed as sulfuric acid and sulfurous acid in the adsorbed water on the powder surface. NOx due to adsorption water pressure mentioned above
, S 02 removal rate increases with the amount of adsorbed water, regardless of whether the powder itself is alkaline or not. [7 Therefore, the method of the present invention not only converts NOx and SO2 into nitric acid mist and sulfuric acid mist, respectively, but also converts NOx and SO2 into NO2
And can it be removed from exhaust gas as S02? 7), it is possible to reduce the radiation edge required for denitrification and denitrification. Furthermore, NOx.

S02 can be completely removed by a dust collector, not as a mist (but as nitric acid/sulfuric acid (or sulfurous acid) in the adsorbed water) together with the powder.
The removal rate of Ox + b O2 is independent of whether the powder itself is alkaline or not, and depends only on the amount of adsorbed water. In other words, the removal rate increases as the amount of adsorbed water increases.

In addition, the powder collected by the dust collector can be reused by separating adsorbed water containing high concentrations of nitric acid and sulfuric acid in a powder purification device and then filling it into the powder addition device again.

EXAMPLES The present invention will be specifically explained below with reference to Examples.

Examples 1 to 4 No (240 ppm) -) 120 (8%) - ○. (1
After irradiating a mixed gas of
51 glass fibers are filled into a container with an internal volume of
and powder (neutral or acidic) IP of the types shown in Table 1.
The concentration of N02 before and after passing through a state where N02 was dispersed was compared. As is clear from Table 1, the NO2 concentration after contact with any of the powders was reduced to half the value before contact. The amount of adsorbed water on the surface of the powder listed in Table 1 was -9 times higher than the adsorption amount at 25°C (5 times higher than the dry powder weight) even at the powder temperature of 100°C in the five experiments. Ta.

Table 1 2 White carbon (TokusilUR) 18
0 706 White Carbon (Tokusil
NR) 18 D 70 Example 5-B Coal combustion υ1・Smoke simulating No. (6[10ppm)
-302 (100-1000ppm) 1000pp%
)-02 (12%)-N2 (8D%) mixed gas at 12
A container with an internal volume of 56°C was filled with 25F glass fiber at 0°C, and 1ooy of white carb:y (To
The concentration of SO2 was compared before and after passing through a place where kusil NR+neutral) was passed for 1 J minutes. The results are shown in Table 2. In any case of primary degree, the SO2 degree is approximately 2
5 o ppm The reason for this decrease is Toku
This shows that S02 is removed by contact with the powder s i l CU.

Clothing 2 5 100 [1 630050 7600350 8100075O NO (250ppm) H2O (8.4%) -02 (12
%) - N2 (79.6%) mixed gas '&120'C when irradiated with O~3 Mrad 1゛ electron beam and white carbon (Tokusil NB + neutral) 6
The NOx level was compared with 9 degrees when the sample was passed through a container with an internal volume of 250 tm3 filled with a mixture of 1 and 1 dispersed therein. As is clear from Table 6, h NOx 8 degrees is
By passing the white carbon layer, f was significantly reduced.

Table 6 90250250 10 1.5 202 11O After electron beam irradiation with a mixed gas of N2 (79.6%) at 120°C and 200°C, white carbon was deposited on a 255' glass fiber whose temperature was adjusted to 120°C and 200°C. (Tok
The NOx concentration was compared when the sample was passed through a container with an internal volume of 5 tons filled with a dispersion of usil NFt + neutral) 10[154]. As is clear from Table 4, the NOx removal rate at 120°C is maintained even at a temperature of 2DO°C. In an example, according to the present invention, by adding powder whose adsorbed water content is 2.5 to 10% of the amount of dry powder wheel at 100°C to the plowing gas and irradiating it with ionizing radiation (
b) Improves denitrification and desulfurization efficiency, thus achieving the required 'a
It has been revealed that it is possible to reduce the amount of trapping radiation and (b) completely collect the mist generated by ionizing radiation irradiation.

[Brief explanation of the drawing]

The figure is a flow sheet showing one embodiment of the method of the present invention.

Claims (1)

[Claims] 1) A method for purifying exhaust gas, which comprises adding powder having adsorbed water on the surface to exhaust gas containing NOx and/or S02, and irradiating the exhaust gas and the powder coexisting with ionizing radiation. . 2) The method according to claim 1, wherein the amount of water adsorbed by the powder is 2.5 to 10 inches of the dry powder weight at 100°C. 3) The method according to claim 1, wherein the powder is finely powdered hydrated limestone, bentonite, or acid clay.