JPS62282625A - Agitating circulation apparatus - Google Patents

Abstract

PURPOSE:To carry out the continuous operation of a circulating pump and the stable treatment operation of a waste gas by providing an opening of gas supply pipe in the stream just behind agitating blades, a partition plate which is also served as a support of the supply pipe, and a discharge stud on the tank wall behind the partition plate. CONSTITUTION:Air 103 supplied through an oxidizing air supply 102 near agitating blades 105 of an air blowing agitator 101 is changed into fine bubbles by the shearing force generated by the rotation of the agitating blades, and a mixed stream of slurry and the bubbles are dispersed by the propelling force of the agitator toward the center part of a corculating tank 104. In the rear part of the agitating blades least bubbles are contained thereby, concretely, speaking the bubbles are scarest in the near part of the discharge stud 107 of the circulating slurry. Moreover, as the partition plate 106 is provided in front of the discharge stud 107 of the circulating slurry, bubbles are not contained in the slurry discharged from the discharge stud 107 of the circulating slurry, and the cavitation in a pump does not therefore occur.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a desulfurization device, and more particularly, to a stirring circulation device for a single-column wet flue gas desulfurization device that recovers gypsum as a by-product. It is something.

[Conventional technology]

The mainstream wet flue gas desulfurization equipment currently in practical use uses a calcium-based absorbent and recovers gypsum as a byproduct.

FIG. 5 is a flow sheet for recovering gypsum using a calcium-based absorbent, and the prior art will be explained with reference to the same figure. Exhaust gas 201' from a boiler or the like is led to a dust removal tower 203 through a dust removal tower inlet duct 202, where the dust removal tower 1i m! Slurry from 204 is sent to spray nozzle 20
5 to remove dust and cool it, and then sent to an absorption tower 206. In the absorption tower 206, the absorption tower circulation tank 2
Calcium-based absorbent slurry is supplied from 07 through an absorption tower circulation pump 208 to a pipe 209 to a nozzle 21.
It is sprayed from zero to absorb and remove sulfur oxides in the exhaust gas. Entrained mist in the exhaust gas is removed by a demister 211, and clean gas 212 is guided to a flue (not shown) via a duct 213. On the other hand, the circulating fluid slurry containing the calcium-based absorbent that has absorbed sulfur oxides is stored in the absorption tower 206.
It changes into calcium sulfite in the absorption tower circulation tank 207, but a part of this is oxidized by oxygen in the exhaust gas in the absorption tower 206 and becomes gypsum. This absorbent slurry is transferred to the absorption tower 20 from a pipe 209 via an absorption tower circulation pump 208.
6 or through the connecting pipe 214 to the dust removal tower circulation tank 20.
4. The slurry in the dust removal tower circulation tank 204 comes into contact with exhaust gas in the dust removal tower 203, and by removing sulfur oxides from the exhaust gas, the amount of unreacted limestone in the slurry is reduced, and the slurry is extracted to the by-product gypsum recovery system. It will be done. That is, it is first sent to a reaction tank 215, where the unreacted calcium carbonate contained therein is converted into gypsum by adding sulfuric acid 216, and the pH is adjusted to a value suitable for oxidizing calcium sulfite.

This slurry is supplied to the oxidation tower 21 by the oxidation tower supply pump 217.
8, where the calcium sulfite is converted to gypsum by air 219. The obtained gypsum slurry is led to Shirafuna 220, where it is separated into solid and liquid, and then sent to a centrifuge 22.
], and gypsum 222 is recovered. The filtered water 223 during solid-liquid separation and dewatering is reused to prepare limestone slurry. Note that the limestone slurry, which is an absorbent for sulfur oxides, is adjusted in a limestone slurry tank 224 with limestone 225, filtered water 223, and make-up water 226, and is circulated in the absorption tower by a bleed pump 227. 207.

In this way, in the conventional method, it is difficult to completely obtain gypsum in the process of absorbing sulfur oxides, so a method is usually adopted in which sulfites generated in the absorption system are turned into gypsum in a separate oxidation tower 218. It's here. However, in recent years oxidation tower 21
Many methods have been proposed in which oxidation of sulfur oxides to sulfates is proceeded in the absorption section by omitting step 8. These methods utilize oxidation catalysts (Japanese Patent Publication No. 58-36619
No.), a method of blowing air into the absorption tower circulation tank 207 or a separately provided reaction tank (JP-A-58-92452, same <95
543) or two-stage desulfurization method (JP-A-58-74126)
) etc. However, the method using a catalyst is not economically viable unless it is efficiently (recovered), and the air blowing method cannot replace the conventional oxidation tower 218 unless a large amount of air is supplied as fine bubbles. It was difficult to oxidize sulfite at a rate of .

In response, the present inventors proposed a new process with the aim of streamlining the wet flue gas desulfurization method, but this
4, 111 is the exhaust gas inflow direction, 1
12 is a dust remover, 113 is an absorption section, 114 is a demister, 1
15 is a limestone slurry supply pipe, 116 is an absorption section circulation tank, 1
17 is an absorption section circulation pump, 119 is a dust removal section circulation tank, 12
2 is a slurry discharge pipe, 123 is a water collector, 101 is an air blowing agitator, 102 is an air supply pipe, 103 is an air inflow direction, 104 is a dust removal section circulation tank, 105 is an agitation blade, and 108 is a slurry delivery direction. . Dust removal, which was conventionally carried out using a venturi type, has been changed to a spray method and incorporated into the lower part of the absorption tower.
2 is provided, and the bottom of the tower is used as a circulation tank 104 for dust removal, and the slurry used for dust removal is directly dropped into this circulation tank 104. Further, the exhaust gas after dust removal reaches the absorption section 113 in the upper part of the tower, and the sulfur oxides contained therein are removed by self-flow contact with the sprayed calcium-based slurry. The slurry in the absorption section 113 is collected by a water collector 123 and returned to the absorption section circulation tank 116 provided separately. Air is supplied into the dust removal tower circulation tank 104 to generate gypsum, and a dedicated oxidation tower is omitted. Limestone slurry, which is an absorbent, is supplied to the absorption section circulation tank 116, and a part of the slurry in this tank is extracted and supplied to the dust removal section circulation tank 104.

According to the findings of the present inventors, good oxidation results can generally be obtained by supplying air near the blades of an agitator installed in the circulation tank as a means for oxidizing sulfite in the circulation tank. At this time, in order to collect the spray or gypsum in the tower, the absorption liquid in which air bubbles are forcibly dispersed must be sent out from the circulation tank by a pump, but at this time, the pump sucks in air, which prevents it from idling (called cavitation). The problem arises. As is well known, when cavitation occurs in the pump, it becomes impossible to operate the pump, causing problems in the operation of the desulfurization equipment. As mentioned above, there have been several proposals to promote the oxidation of sulfites by supplying air into the circulation tank, but none have been found to take measures against cavitation. On the other hand, apart from pump cavitation, in order to reach the tip of the air supply pipe close to the agitator blade, a supply pipe with a length of 0.3 to 2 m is usually required, and there is a risk of vibration or damage due to the stirring flow in the tank. Therefore, it has been difficult to supply stable microbubbles.

[Problem that the invention seeks to solve]

As mentioned above, it was necessary to solve the problems of supplying stable microbubbles into the circulation tank and, on the other hand, feeding a fluid with few bubbles to the suction side of the pump in order to prevent cavitation of the pump. The present invention has been made to solve the above problems.

[Means for solving problems]

The purpose of the above is to install the air supply pipe immediately behind the stirrer blade, and to separate the absorbent liquid from the side wall of the circulation tank behind the stirrer with the least amount of microbubbles through a partition plate that also serves as support for the air supply pipe. This is accomplished by pumping the slurry out of the tank.

[Effect]

As a result of the above, air bubbles are constantly and stably supplied into the circulation tank, and since the partition plate is provided and the liquid is extracted from a position where there are few air bubbles, air bubbles are not caught in the circulation pump, and there is no fear of cavitation.

〔Example〕

FIGS. 1 and 2 are cross-sectional views of the area around the air blowing agitator 101 in the circulation tank 104 of a wet flue gas desulfurization apparatus showing an embodiment of the present invention.

101 is an air blowing agitator, 102 is an air supply pipe, 10
3 is an air inflow direction, 104 is a dust removal section circulation tank, 105 is an agitation blade, 106 is a partition plate, 107 is an extraction seat, and 108 is a slurry delivery direction.

Air 103 supplied from the oxidizing air supply pipe 102 near the stirring blades 105 of the air blowing stirrer 101 becomes fine bubbles due to the shear force generated by the rotation of the stirring blades, and the mixed fluid of slurry and bubbles is further circulated by the thrust of the stirrer. Since the air bubbles are dispersed toward the center of the tank 104, there are the fewest air bubbles behind the stirring blades 105. This was obtained by the inventors through experiments in a 0.8 m diameter tank and a 2.2 m diameter tank. In this way, the vicinity of the circulating slurry extracting seat 107 provided behind the stirring blade 105 has the least amount of air bubbles, and furthermore, in front of the circulating slurry extracting seat 107, there is a partition plate 106.
is installed, the circulation slurry extraction seat 107
There are no air bubbles in the slurry extracted from the
Pump cavitation does not occur. Also, the circulation tank 10
4 has an agitating flow to prevent slurry solids from settling at the bottom of the tank, and the air supply pipe 102 is subject to considerable fluid resistance, but because it is supported by this partition plate 106, vibration does not occur and the flow is smooth. 6. If there is no partition plate, vibrations will occur, and air cannot be stably supplied near the blades, resulting in the formation of coarse bubbles, which will significantly reduce the bubble dispersion efficiency.

〔Effect of the invention〕

By implementing the present invention, in a wet flue gas desulfurization system that performs absorption oxidation in one tower, the support of the air supply pipe is stable, cavitation of the circulation pump is eliminated, the circulation pump can be operated continuously, and the flue gas treatment operation is stable. The oxidation effect was significantly improved.

[Brief explanation of the drawing]

Figures 1 and 2 are a side view and a plan view showing an embodiment of the stirring circulation tank according to the present invention, Figures 3 and 4 are flow sheet diagrams of a flue gas desulfurization apparatus to which the present invention can be applied, and Figure 5. 1 is a diagram showing a flow sheet of a conventional flue gas desulfurization device. 1 shows a flow sheet of an apparatus to which the stirring circulation tank according to the present invention can be applied.

Claims (1)

[Claims] 1. A tank containing a slurry-like fluid, a supply pipe for supplying gas into the fluid, an agitator equipped with stirring blades for dispersing and stirring the fluid and the gas, and sending the fluid out of the tank. In the agitation circulation device comprising an extraction seat and a circulation pump, an opening of the gas supply pipe is provided in a flow path immediately behind the agitation blade, and a partition plate that also serves as support for the supply pipe;
A stirring circulation device characterized in that the extraction seat is provided on a tank wall further behind the partition plate.