JPH06262037A - Method for denitrification of exhaust gas from glass kiln - Google Patents

Abstract

PURPOSE:To prevent clogging and deterioration of a denitrification catalyst in a nitrogen oxide removing process from occurring and to perform denitrification of exhaust gas for a long time by holding a demister under a wet condition when SOx in the exhaust gas from a glass kiln is desulfurizated under wet condition and the treated gas is passed through the demister and then, reduction of NOx with ammonia is performed. CONSTITUTION:Exhaust gas from a glass kiln for producing sheet glasses etc., is at first introduced in a wet desulfurization apparatus and SOx in the exhaust gas is removed by transferring the exhaust gas from the lower part to the upper part while caustic soda water soln. is sprayed. Then, the exhaust gas is introduced into a demister and is brought into contact with water from a water spraying pipe to make the demister under a wet condition in such a way that waterdrops are dropped down with condensed water of steam in the exhaust gas and dust is removed thereby. Then, the exhaust gas from the demister is heated at about 350 deg.C and it is passed through a honeycomb catalyst after ammonia is incorporated to reduce nitrogen oxide to nitrogen gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for denitrifying exhaust gas from a glass kiln.

[0002]

Is first wet desulfurization the SO _x in the combustion exhaust gas of the Prior Art Glass furnace, then wet desulphurized gas passed through the demister and to remove dust in the gas and then feeding the gas to the denitration apparatus, NH ₃ A method is known in which NO _x in gas is reduced to N ₂ in the presence of a catalyst for blowing NO.

[0003]

However, in this method, dust that cannot be removed by the demister enters the denitration device and adheres to the surface of the denitration catalyst to reduce the NO _x removal efficiency, or the vent holes of the denitration catalyst are blocked. There was a problem to do. The present invention solves the above problems of the prior art, and dust adheres to the surface of the denitration catalyst to reduce the NO _x removal efficiency,
An object of the present invention is to provide a method for denitrifying exhaust gas from a glass kiln without blocking the vent holes of the denitration catalyst.

[0004]

According to the present invention, SO _{x in} the exhaust gas of a glass kiln is wet desulfurized, the wet desulfurized gas is then passed through a demister to remove dust in the gas, and then the gas is removed with NH _3. This is a method for denitration of exhaust gas, which is characterized in that a demister is kept in a wet state in reducing and removing NO _x therein.

[0005] In the present invention, the exhaust gas of the glass furnace is first SO _x in the exhaust gas by a wet desulfurization is removed. This wet desulfurization method can be used in a wide range such as a type in which exhaust gas is contacted with an aqueous solution of caustic soda, sodium carbonate or the like to absorb SO _x in the exhaust gas into the aqueous solution, and is recovered as Glauber's salt.

In this wet desulfurization process, dust is removed in addition to SO _x . Usually, in this process, the exhaust gas is cooled to about 60 to 70 ° C. Exhaust gas that has passed through this wet desulfurization process contains a small amount of SO _x dust (containing mainly alkali metal and sulfur compounds).

[0007] Then, gas containing SO _x dust of the small amount passes through the demister, traces of the SO _x dust is removed. This demister is always kept in a wet state by water condensed with water vapor contained in the exhaust gas, water supplied separately from the outside or the like. It is sufficient that the wet state is such that water drops are dropped from the demister.

Further, the through hole of this demister is 0.5 to
Those having an area corresponding to a circle of 20 μmΦ are preferable. If the through-holes are smaller than the lower limit of the above range, the resistance of exhaust gas becomes too large, which is not preferable, and if the through-holes are larger than the upper limit, the removal rate of SO _x dust decreases, which is not preferable. As the structure of the demister, a wide range of structures such as a wire mesh type are adopted.

When the exhaust gas passes through this demister,
Dust and SO _x are adsorbed or dissolved in the water adhering to the demister and removed from the exhaust gas. Furthermore, the mist is
It is captured in the through holes of the demister and removed from the exhaust gas.

Water containing dust, SO _x , and mist becomes water droplets, which are dropped from the demister and discharged from the exhaust gas flow path to the outside to undergo a predetermined treatment.

Next, the exhaust gas passing through the demister is 3
Heat to a temperature of 00-400 ° C. and add ammonia. Next, the exhaust gas containing this ammonia passes through the honeycomb catalyst, and the nitrogen oxides in the exhaust gas are reduced to nitrogen gas. As this catalyst, TiO ₂ —V ₂ O ₅
-Wide range of materials such as WO ₃ type are used.

Next, the exhaust gas from which the nitrogen oxides have been removed is subjected to heat recovery by the heat exchanger and discharged from the chimney to the outside. From the viewpoint of thermal efficiency, it is preferable to use the heat recovered by this heat exchanger for heating the exhaust gas that has passed through the demister.

[0013]

[Examples] Exhaust gas from a glass kiln producing sheet glass was first introduced into a wet desulfurization apparatus. In this wet desulfurization device, caustic soda water is sprinkled, and the exhaust gas is caused to flow upward from the lower part of the device to come into contact with the caustic soda water, and SO _x in the exhaust gas is removed. Next, the exhaust gas that passed through the wet desulfurization device was introduced into the EP device, and the dust in the exhaust gas was removed. The temperature of this exhaust gas was about 60 ° C.

Then, the exhaust gas was introduced into the demister.
In this demister, each wire mesh having a through hole of 1 μm in the lower part and a through hole of 10 μm in the upper part is provided, and a water spray pipe is provided between the two. The wire mesh was wet to the extent that water droplets dropped due to the condensation of water vapor contained in the exhaust gas and the water spray of the water spray pipe.

An exhaust gas was provided below the lower wire mesh to flow the exhaust gas from the lower side to the upper side, and discharged from an outlet provided above the upper wire mesh. Then
The exhaust gas discharged from the outlet of the demister was heated to 350 ° C., and ammonia was added. Next, the exhaust gas passed through the honeycomb catalyst, the nitrogen oxides in the exhaust gas were reduced to nitrogen gas, and the exhaust gas was discharged to the outside air.

In the treatment of the exhaust gas, the dust concentration (dust, SO _x ) was measured, and as a result, it was about 30 mg / Nm ^{3 at} the demister inlet and about 4 mg at the demister outlet.
/ Nm ³ .

For comparison, when the same exhaust gas treatment was performed without making the upper wire mesh wet, the dust concentration was about 30 mg / Nm ³ at the demister inlet,
It was 12 to 18 mg / Nm ³ at the demister outlet.
As described above, according to the present invention, since the removal rate of soot and dust is extremely high, the denitration catalyst is unlikely to be blocked or deteriorated in the subsequent nitrogen oxide removal step.

[0018]

EFFECTS OF THE INVENTION According to the present invention, since a small amount of dust and SO _x contained in the wet desulfurized exhaust gas are highly removed, clogging and deterioration of the denitration catalyst are prevented in the subsequent nitrogen oxide removal step. It is difficult to occur, and it is possible to denitrate the exhaust gas of the glass kiln continuously for a long period of time.

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Claims (1)

[Claims] 1. A the SO _x in the exhaust gas of the glass furnace and wet desulfurization, then wet desulfurized gas is passed through the demister,
A method for denitrification of exhaust gas, which comprises maintaining a demister in a wet state when removing dust in the gas and then reducing and removing NO _x in the gas with NH ₃ .