JPS6113857B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing corrosion of an acid gas removal device for removing acid gases such as hydrogen chloride contained in exhaust gas.

Exhaust gas from garbage incinerators and the like contains acidic gases such as hydrogen chloride, and if these are released into the atmosphere as they are, they will cause pollution problems. Therefore, removing such acid gas from exhaust gas is
This is extremely important from the standpoint of pollution prevention.

Methods for removing hydrogen chloride contained in exhaust gas include dry, semi-dry, and wet methods, but recently the semi-dry method has been used in terms of hydrogen chloride removal efficiency, construction costs, maintenance costs, etc. is being implemented as a preferred method in various fields.

The semi-dry method is a method in which a drug for removing acidic gases, such as slaked lime, is made into a slurry with water, the exhaust gas is brought into contact with the slurry-like drug, and the acidic gases are removed by this contact reaction.

The above-mentioned means for contacting the exhaust gas with the slurry-like chemical includes a filling contact method in which the packing in the reaction tower is sprinkled with the slurry-like chemical and the exhaust gas is blown into the packing to contact with the chemical; There is a spray contact method in which a slurry-like chemical is injected into a reaction tower and brought into contact with the exhaust gas, and the spray contact method is superior in terms of reaction efficiency.

FIG. 1 is a schematic vertical cross-sectional view showing an example of an apparatus used in the above-mentioned spray contact method, in which 1 is a reaction tower, 2 is an exhaust gas inlet provided on the upper side wall of the reaction tower 1, and 3 is a lower part of the reaction tower 1. An exhaust gas outlet provided on the side wall; 4 is a chemical supply nozzle of a predetermined length provided on the top wall 1a of the reaction tower 1 along the axial direction toward the inside of the reaction tower; 5 is a nozzle at the lower end of the nozzle 4; A rotating disk 5 is provided at a facing position, and the rotating disk 5 has a support shaft 6 inserted through the nozzle 4 so as to be rotatable along its axis.
Its center is fixed to the bottom edge of. 7 is the spindle 6
A driving motor 8 is a dust outlet provided at the lower end of the reaction tower 1.

In the above-described apparatus, the exhaust gas enters the reaction tower 1 through the exhaust gas inlet 2, descends while swirling inside the tower, and is discharged through the exhaust gas outlet 3. On the other hand, in the reaction tower 1, a rotating disk 5 is rotating at a position facing the lower end of the drug supply nozzle 4 provided at the top thereof, so that the slurry-like drug flowing down from the nozzle 4 is It collides with the disk 5 and is sprayed into the reaction tower 1. Therefore, the exhaust gas that descends while swirling inside the reaction tower 1 comes into contact with the above-mentioned sprayed chemical, and the acidic gas in the exhaust gas can be removed.

However, in the above-mentioned device, the rotating disk 5
As mentioned above, the chemical sprayed and scattered in the reaction tower 1 is in the form of a slurry, so the atmosphere around the rotating disk 5 becomes an atmosphere containing water droplets, and furthermore, a vortex as shown in the figure is generated near the bottom of the rotating disk 5. , the lower surface of the rotating disk 5 is in a wet state.

As a result, a corrosive liquid that has absorbed hydrogen chloride in the exhaust gas is generated in the humid atmosphere of the rotating disk 5, causing strong corrosion. As shown in Fig. 2, this corrosion occurs in the form of linear marks radiating from the center to the outer circumference on the lower surface of the rotating disk 5, and even if the material of the rotating disk 5 is SUS316, for example, it will occur within a few days. Occur.

Therefore, the rotating disk 5 must be replaced frequently or its material must be made of an expensive special alloy with high corrosion resistance.

From the above-mentioned viewpoint, this invention aims to prevent corrosion of a rotating disk for spraying a chemical in an acid gas removal device.
This provides a corrosion prevention method for acid gas removal equipment that can accurately prevent corrosion without using special materials. Exhaust gas containing acid gas is blown into the reaction tower and discharged from the reaction tower. In the meantime, the rotating disk of the acid gas removal device that removes acidic gas from the exhaust gas is brought into contact with the scattered chemicals by a rotating disk provided at the upper part of the reaction tower, and is cleaned toward the bottom surface thereof. inject gas,
The present invention is characterized in that corrosion of the rotating disk is prevented by purging the lower surface of the rotating disk with the clean gas.

Next, the present invention will be explained based on the drawings.

FIG. 3 shows a schematic vertical sectional view of an example of the apparatus used in the method of the present invention. In the drawings, parts that are the same as those of the conventional device are designated by the same reference numerals, and their explanations will be omitted.

In this invention, a nozzle 9 for injecting clean gas toward the lower surface of the rotating disk 5 is provided with its tip facing the lower surface of the rotating disk 5. 10 is a conduit that sends clean gas to the nozzle 9; a blower 11 is connected to one end of the conduit 10;
A heater 12 is provided in the middle.

Air, which is a clean gas, is guided into a conduit 10 by a blower 11, heated to 150° C. or higher by a heater 12, for example, with steam, and then injected from a nozzle 9 toward the lower surface of the rotating disk 5.

As a result, the lower surface of the rotating disk 5 is purged by the injected air, so a humid atmosphere is not created, and hydrogen chloride in the exhaust gas does not come into contact with it. Also,
Since the injected air is heated to 150° C. or higher, the temperature exceeds the acid dew point of hydrogen chloride, sulfur dioxide, etc. contained in the exhaust gas, and corrosion of the rotating disk 5 is thereby significantly reduced.

Note that the above-mentioned injection air does not necessarily need to be heated to 150°C or higher. In this case, adjust the amount of air jetted from the nozzle 9, or
The interval between the two is increased so that the dry high-temperature exhaust gas in the reaction tower 1 is drawn in, thereby raising the temperature of the air injected onto the lower surface of the rotating disk 5 to 150° C. or higher. In this case, the conduit 10 in the reaction tower 1 needs to be structured so that its outer surface does not fall below the acid dew point by heat insulation or other methods.

Note that the clean gas is not limited to air, and may be an inert gas or clean exhaust gas.

Next, the present invention will be explained with reference to examples.

Using the apparatus shown in FIG. 3, exhaust gas containing acidic gas was treated under the following conditions (average values for one month).

Exhaust gas inlet flow rate: ^1520Nm3 /H Exhaust gas inlet temperature: 380℃ Exhaust gas inlet HCl amount: 645ppm Chemical (slaked lime) supply amount: Slurry concentration 15% Slurry flow rate 33/H Rotating disk: Material SUS316, outer diameter 160mm, rotation speed 15000r. pm Injection air: Flow rate 30Nm ³ /H Temperature 230℃ (heated by steam) Nozzle diameter 32A Initial speed at injection 15.4m/sec Exhaust gas outlet flow rate: 1550Nm ³ /H Exhaust gas outlet temperature: 270℃ Exhaust gas outlet HCl amount: 80ppm HCl removal rate : 87.6% After operating for one month under the above conditions, no corrosion occurred on the lower surface of the rotating disk.

On the other hand, when the rotary disk was operated under the same conditions as above without air injection to the lower surface of the rotary disk, corrosion occurred in the rotary disk after only the second day.

As described above, according to the method of the present invention, corrosion of the rotating disk for spraying chemicals in an acid gas removal device can be prevented accurately and economically without using any special material. is brought about.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view showing an example of a conventional acid gas removal device, FIG. 2 is an explanatory diagram showing the corrosion state of a rotating disk, and FIG. 3 is a schematic diagram showing an example of the device used in the method of the present invention. FIG. In the drawings, 1... Reaction tower, 2... Exhaust gas inlet, 3... Exhaust gas outlet, 4... Drug supply nozzle, 5... Rotating disk, 6... Support shaft, 7... Motor, 8... Dust Discharge port, 9... nozzle, 10... conduit, 11... blower, 12... heater.

Claims (1)

[Claims] 1. While blowing exhaust gas containing acidic gas into the reaction tower and discharging it from the reaction tower, the acidic gas in the exhaust gas is brought into contact with a chemical agent scattered by a rotating disk provided in the reaction tower. Corrosion is prevented by injecting clean gas toward the lower surface of the rotating disk of the acid gas removal device to be removed, and purging the lower surface of the rotating disk with the clean gas. Corrosion prevention method for acid gas removal equipment.