JPH02111420A - Stack gas desulfurizing device of wet system - Google Patents

Abstract

PURPOSE:To prevent clogging of an air supply nozzle by subjecting the air for oxidation discharged from the air supply nozzle to fining and dispersing by the impeller of a stirrer after this air is previously dispersed by an auxiliary impeller, etc., and is thereby given the thrust to the impeller of the stirrer. CONSTITUTION:The stirrer 6 is installed to the side face of a circulating tank 9 and a sleeve 11 is provided along the shaft 14 of the stirrer 6. The air 7 for oxidation is blown from the spacing between the shaft 14 and the sleeve 11 into a circulating slurry, by which the air is dispersed and supplied. The auxiliary stirring member 13 is provided to the shaft 14 in such a manner that the member is inserted at least partly to the side wall side of the tank 9 from the air outlet of the sleeve 11. Namely, the final fining and dispersing are executed after the predispersing of the air is executed and, therefore, the high gas- liquid contact is attained and the volume of the air for oxidation and the number of units of the stirrers for oxidation are reduced; in addition, the clogging of the air supply nozzle is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a wet flue gas desulfurization device, and particularly to a desulfurization device suitable for promoting oxidation of sulfite, which is an absorption product.

[Conventional technology]

Currently, the mainstream wet desulfurization equipment in practical use uses a calcium-based absorbent and recovers gypsum as a byproduct.
A limestone-gypsum method using quicklime and slaked lime is known.

FIG. 5 is an overall view of a conventional wet flue gas desulfurization device showing a typical example thereof. This device includes a desulfurization tower 2, a circulation tank 9 provided at the bottom of the desulfurization tower, an air supply pipe 10 that supplies air to the circulation tank, and a circulation pump 4 that transports circulating slurry from the circulation tank 9 to the desulfurization tower 2. It is mainly composed of. A plurality of oxidation stirrers 6 and, if necessary, a slurry stirrer 8 are provided on the side wall of the circulation tank 9. The oxidation stirrer 6 has a stirrer impeller 12 behind which an air supply nozzle 11 is provided surrounding a shaft 14 .

In FIG. 5, exhaust gas l generated from a boiler etc. is led to a desulfurization tower 2, where it comes into contact with circulating slurry, and is brought into contact with a demister 3.
The mist is removed in the desulfurization tower 2 and discharged from the desulfurization tower 2. on the other hand,
Limestone slurry 5, which is an absorbent slurry, is supplied to a circulation tank 9 located at the bottom of desulfurization tower 2 by a limestone slurry pump (not shown), and the slurry is supplied to a sprayer installed in desulfurization tower 2 by circulation pump 4. It is supplied to the nozzle 16, from where it is sprayed into the tower 2, comes into contact with the exhaust gas, removes dust and sulfur oxides from the exhaust gas, and naturally falls into the circulation tank 9. The oxidizing air 7 blown out from the air supply nozzle 11 of the oxidizing agitator 6 behind the agitator impeller 12 is atomized and dispersed by the agitator impeller 12 and supplied into the circulation tank 9. The absorption product sulfite in the circulation tank 9 is oxidized and becomes gypsum. The slurry containing gypsum is sent to a gypsum recovery process (not shown) to recover the gypsum.

[Problem to be solved by the invention]

However, when the air supply source that supplies air to the oxidizing agitator 6 used as a means of oxidizing sulfite is a compressor or a proir, the amount of air ejected is not necessarily constant even if it is operated at a constant speed due to its mechanism. However, by producing a certain amount of pulsation in the amount of air, the generated salt may solidify (scale) in the air discharge area. In order to prevent this, it is conceivable to throttle the discharge port of the air supply pipe 10 to increase the air discharge speed, but in this case as well, the time until scale generation is only slightly longer.

In addition, when air is blown onto the impeller of the oxidation agitator 6 to generate microbubbles suitable for oxidation, an air film is formed around the impeller, and the shearing force generated by the rotation of the impeller causes Air bubbles will be generated at the interface between the air and the slurry. However, the thickness of the air film that forms around the impeller is not uniform, so the air outlet and impeller are exposed to air and immersed in slurry (wet and dry repeatedly), causing scale to build up. This condition is likely to occur. In order to prevent this, if the air discharge port is installed at a position away from the impeller, the air will rise without contacting the impeller, and air bubbles will not be generated and the air will not be used effectively.

Furthermore, as the size of the device increases, the diameter of the impeller that blows air increases, and if air is blown into the impeller from one location, the thickness of the air film around the impeller will vary, reducing the bubble generation efficiency. On the other hand, if the number of air supply points is increased, the drifting flow will be reduced and the generation of single bubbles will be improved, but there is a drawback that clogging and scale will easily occur and the structure will be complicated.

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, to supply air without clogging the air outlet or generating scale, and to generate good fine bubbles.
An object of the present invention is to provide a wet flue gas desulfurization device suitable for oxidation.

(Means for Solving the Problem) The above object is achieved by installing an auxiliary stirring member on the shaft near the discharge port of the air supply nozzle. That is, in the present invention, an agitator is installed on the side of the circulation tank, a sleeve is provided along the shaft of the B2 agitator, and oxidizing air is blown into the circulating slurry from the gap between the shaft and the sleeve. In the wet flue gas desulfurization device that supplies the flue gas in a dispersed manner, the shaft is provided with an auxiliary stirring member so that at least a portion thereof is inserted toward the side wall of the tank from the air outlet of the sleeve.

It is preferable to use an auxiliary impeller, a protrusion, or the like as the auxiliary stirring member in the present invention. The installation location is appropriately determined so that at least a portion of the sleeve is inserted closer to the side wall of the tank than the air outlet of the sleeve, and scale does not adhere to the inner wall of the sleeve when the shaft of the agitator rotates.

[Effect]

The oxidizing air discharged from the air supply nozzle is predispersed by an auxiliary impeller, etc., and after being given a driving force to the agitator impeller, it is atomized and dispersed by the agitator impeller, resulting in good gas-liquid contact. At the same time, even if scale grows on the inner surface of the nozzle outlet, it is removed by the auxiliary impeller, so the air supply nozzle will not be clogged.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is an overall view of a flue gas desulfurization apparatus showing one embodiment of the present invention, and FIG. 2 is a detailed view of the oxidation agitator shown in FIG. 1.

This device has an auxiliary impeller 13 installed on the shaft 14 behind the agitator impeller 12 so that a part of it enters the air outlet of the air supply nozzle 11, and the rest is the same as the conventional one shown in FIG. It has the same configuration as the desulfurization equipment.

In such a configuration, the oxidizing air 7 supplied from the air supply nozzle 11 is given a swirling flow by the auxiliary impeller 13 and is preliminarily dispersed, and then further passed through the agitator impeller 1.
It is finely dispersed in Step 2 and supplied to the absorbent slurry.

According to the embodiment described above, the provision of the auxiliary impeller 13 prevents the slurry from entering the air supply nozzle 11 due to the pulsation of air that stops due to the mechanism of the compressor or proer that is the air supply source, or repeating drying and wetting. The air supply nozzle 11 can be prevented from being clogged by the air supply nozzle 11, and even if scale occurs or grows, the auxiliary impeller 13 has the effect of scraping it off, so a minimum air passage area is ensured.
There is no possibility that the oxidizing air cannot be supplied.

In addition to the shape of the auxiliary impeller 13 shown in FIG.
As shown in the figure, the auxiliary impeller 13 may be twisted to increase the discharge force, or as shown in FIG. 4, a plurality of rod-shaped protrusions 13A may be attached to the shaft.

As a method for further improving the performance of the present device, water may be injected into the air supply nozzle 11 that supplies the oxidizing air 7, and a mixed fluid of water and air may be discharged from the air supply nozzle 11. As a result, scale will hardly occur in case of clogging, and the present invention can be carried out more effectively.

〔Effect of the invention〕

According to the present invention, by providing an auxiliary stirring means to the oxidizing stirrer, air is predispersed and then the final fine dispersion is performed, so that high gas-liquid contact can be obtained, and the amount of air for oxidizing In addition to reducing the number of oxidation agitators, it is possible to prevent the air supply nozzle from clogging, and there is no need to stop the device due to blockage, so it is possible to prevent the performance of the entire desulfurization device from deteriorating.

[Brief explanation of drawings]

FIG. 1 is an overall view of a desulfurization apparatus showing an embodiment of the present invention;
Fig. 2 is a detailed view of the oxidation agitator shown in Fig. 1, Figs. 3 and 4 are diagrams of the shape of an auxiliary impeller showing other embodiments of the present invention, and Fig. 5 is a conventional desulfurization device. This is an overall diagram. 1... Exhaust gas, 2... Desulfurization tower, 3... Demister,
4... Circulation pump, 5... Absorbent, 6... Stirrer for oxidation, 7... Air, 8... Stirrer for slurry, 9.
...Circulation tank, 10...Air supply piping, 11...
Air supply nozzle, 12... Stirrer impeller, 13...
- Auxiliary impeller, 14...Shaft, 15...Agitator seat, 16...Spray nozzle. Patent applicant: Habcock Hitachi Co., Ltd. Agent: Patent attorney Takeshi Kawakita

Claims (1)

[Claims] (1) A stirrer is installed on the side of the circulation tank, a sleeve is provided along the shaft of the stirrer, and oxidizing air is blown into the circulating slurry from the gap between the shaft and the sleeve to disperse and supply air. A wet type flue gas desulfurization device, characterized in that an auxiliary stirring member is provided on the shaft so that at least a part of the shaft is inserted toward the side wall of the tank from the air outlet of the sleeve.