JPS61278331A - Desulfurizing method for exhaust gas containing trace so2 - Google Patents

Abstract

PURPOSE:To perform the desulfurization of an exhaust gas in an extremely easy means by spraying a dilute alkali liquid in the exhaust gas contg. SO2 in the ppm order and bringing it into contact with the exhaust gas. CONSTITUTION:An alkali liquid having about 7-15% concn. and about 20 deg.C temp. is blown in an exhaust gas contg. SO2 in the concn. (about 100ppm in an embodied example) of the ppm order with a spray by applying a jet process. Still more as the alkali liquid, caustic soda liquid is usually used and the spray conditions are selected so that the spray consisting of 10-400mu liquid droplet high in the absorption effect of SO2 is obtained. In the above operation, SO2 contained in the exhaust gas is excellently absorbed in the alkali liquid and the liquid droplets absorbed with SO2 are no carried away together with the gas and SO2 contained in the exhaust gas can be easily decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a desulfurization method for absorbing and removing sulfur dioxide gas (SO2) contained in exhaust gas at a concentration on the order of ppm.

Previously, in most wet flue gas desulfurization methods, a special SO2 absorption zone (absorption tower, packed layer, venturi throat, etc.) was provided, and desulfurization was carried out through gas-liquid contact. I am doing it. Therefore, in the conventional method, the equipment for the above-mentioned absorption band is large-sized, and the cost thereof is unavoidably high.

The inventor of the present invention investigated a method for desulfurizing exhaust gas by a simple means without the need to provide a special absorption zone, and found that 502 was desulfurized at a concentration on the order of ppm. It was discovered that when the exhaust gas containing S02 is brought into contact with a spray of dilute alkaline liquid, the 302 in the exhaust gas is well absorbed by the alkaline liquid, and the droplets that have absorbed S02 are not carried away with the gas, leading to the present invention. .

Therefore, an object of the present invention is to provide a method that can desulfurize exhaust gas containing 502 at a concentration on the order of ppm by extremely simple means without using a special absorption zone.

The present invention will be explained in detail below.

A feature of the present invention is that a dilute alkaline liquid is blown into the exhaust gas containing sulfur dioxide gas at a concentration on the order of ppm in the form of a spray.

To inject dilute alkaline liquid into the above exhaust gas in a spray state, apply the jet method to spray the alkaline liquid, then introduce compressed air from around the nozzle to adjust the pressure of this compressed air and the flow rate of the alkaline liquid. Do it while doing it. In this case, the mounting position of the nozzle and the air blowing hole are selected so that the gas flow is turbulent, preferably a swirling turbulence.

When the alkaline liquid spray is injected into the exhaust gas as described above, the mixture and contact between the exhaust gas and the alkaline liquid spray improves, and the SO2 in the exhaust gas is quickly absorbed by the relatively fine droplets of the alkaline liquid. .

In addition, since the spray condition varies slightly depending on the concentration and temperature of the alkaline liquid, it is preferable to select the spray condition so as to obtain a spray consisting of droplets of 10 μ to 400 μ, which is a spray condition that has a high absorption effect of S02.

As the alkaline liquid used here, a caustic soda solution is usually suitable, but any alkaline liquid that can absorb SO2 in the exhaust gas may be used, and examples thereof include caustic potash, calcium hydroxide, magnesium hydroxide, and the like.

Further, the concentration and temperature of the alkaline solution are suitably about 7% to about 15% and about 20°C.

According to the present invention, it is possible to reduce SOx in the exhaust gas by simply spraying the alkaline liquid into the exhaust gas path as described above.

and 9 The present invention and its effects will be explained in more detail with reference to Examples below.

Example 1 Exhaust gas containing 502 at a concentration of 100 ppra (gas amount 7
3ONn? A 13% concentration caustic soda aqueous solution (liquid temperature 20°C) was added at a flow rate of 70 N/h to a gas salt temperature of 13°C) via compressed air at a pressure of 3.0 kg/cnl.
It was injected into a spray using KI Jet. In addition,
The gas flow rate at the spray position was 11 m/sec.

The removal rate of SO2 in the exhaust gas and the utilization efficiency of caustic soda are as shown in Table 1 below.

Example 2 A 15% concentration caustic soda aqueous solution (liquid temperature 20°C) was added to SO2 containing a concentration of 120 ppm as exhaust gas.
0 I! Desulfurization was carried out in the same manner as in Example I, except for spraying at a liquid volume of /h. The removal rate of 502 in the exhaust gas and the utilization efficiency of caustic soda are as shown in Table 1 below.

Example 3 Instead of using a 13% aqueous caustic soda solution,
% concentration of caustic soda aqueous solution (liquid temperature 20°C) and spraying at a liquid volume of 30 Il/h.
Desulfurization was carried out in the same manner. The removal rate of SO2 in the exhaust gas and the utilization efficiency of caustic soda are as shown in Table 1 below.

Example 4 A 15% aqueous solution of caustic soda (liquid temperature 20°C) was added at 30°C to exhaust gas containing SO2 at a concentration of 120 ppm.
Desulfurization was carried out in the same manner as in Example 1, except that the solution was sprayed at a liquid volume of 1/h. The removal rate of 502 in the exhaust gas and the utilization efficiency of caustic soda are as shown in Table 1 below.

Example 5 This example shows the case where a caustic soda aqueous solution is sprayed at a low temperature of 15°C, and the exhaust gas is 50°C.
Desulfurization was carried out in the same manner as in Example 1, except that a 7% concentration aqueous solution of caustic soda (liquid temperature 15°C) was sprayed at a volume of 601 /h onto a sample containing 80 ppm of 2. The removal rate of SO2 in the exhaust gas and the utilization efficiency of caustic soda are shown in Table 1.

As shown in Table 1, the temperature of the caustic soda aqueous solution is 15
At temperatures as low as ℃, apart from the hourly absorption of SO2, Na
It can be seen that it is preferable to spray at a liquid temperature of about 20° C. since the OH utilization efficiency decreases.

It can also be seen that the absorption amount of S02 improves as the concentration of the caustic soda aqueous solution increases from about 10 to 15% and as the amount of the solution increases.

Claims (3)

[Claims] (1) The method for desulfurizing exhaust gas described above, which comprises blowing a dilute alkaline solution in a spray state into the exhaust gas containing sulfur dioxide gas at a concentration on the order of ppm. (2) The desulfurization method according to claim (1), wherein the alkaline liquid is an aqueous caustic soda solution having a concentration of about 7 to about 15%. (3) The desulfurization method according to claim (1), wherein the alkaline liquid is atomized using compressed air.