JPS5843332B2 - Oxidation tower for flue gas desulfurization gypsum recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxidation tower for a flue gas desulfurization gypsum recovery method that makes it possible to recover only high-quality coarse-grained gypsum.

The flue gas desulfurization gypsum recovery method collects SO2 from combustion flue gas from boilers, etc.
The gas is absorbed and removed using lime slurry, and the generated calcium sulfite (CaSO3-!-H20) is oxidized by introducing air into an oxidation tower to form gypsum (CaSO4.2H20).
This is what is collected.

The reaction is as follows.

CaCO3+5O2-+CaSO3・-H2O・・・・
...SO2 absorption 1 l 2 CaS03--H3O+-i:02→CaSO4"2H
20.--Oxidation If the particle size of the gypsum obtained by this gypsum recovery method is small, it is difficult to remove water in a post-processing thickener or centrifugal separator, and therefore, a large amount of moisture adheres to the gypsum.

If there is a lot of moisture attached, gypsum not only becomes sticky and difficult to transport, but also requires extra heat when mixing with cement and manufacturing boards, which is disadvantageous in terms of thermoeconomics. It is unsuitable for use because it deteriorates the quality of other materials, and it may solidify during firing.

Therefore, in the gypsum recovery method, it is necessary to increase the gypsum particle size and improve the quality using an oxidation tower.

However, the oxidation tower used in the conventional gypsum recovery method only oxidizes CaSO3.--HH2O, and it has not been considered to selectively extract gypsum with large crystal grain sizes.

Furthermore, when the oxidation rate in conventional absorption towers is low, the crystal grains of gypsum cannot be made large, which poses a problem.

The present invention solves the drawbacks of the conventional equipment described above and provides an oxidation tower for the flue gas desulfurization gypsum recovery method that makes it possible to recover only high-quality coarse-grained gypsum. In an oxidation tower for the flue gas desulfurization gypsum recovery method that oxidizes air to produce gypsum, a plurality of bubble dispersers for oxidizing air are arranged around the bottom of the oxidation tower main body, and a plurality of bubble dispersers for oxidizing air are installed in the classification body provided at the center of the bottom. An oxidation tower for flue gas desulfurization gypsum recovery method, characterized in that an air disperser for classification is attached and a gypsum slurry outlet is provided in the classification body.

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

Fig. 1 is an overall view of an embodiment of the present invention, Fig. 2 is a detailed view of the main parts of the embodiment of Fig. 1, and Fig. 3a is an example of a bubble disperser used in the embodiment of Fig. 1. Longitudinal cross-sectional view, b is A- of a
It is a view from arrow A.

1 and 2, this embodiment shows the oxidation tower main body 1
A plurality of bubble dispersers 15 for oxidizing air are arranged around the bottom, and a bubble disperser 14 for classification is installed in the classification body 17 provided at the center of the bottom, and a gypsum slurry outlet 3 is provided in the classification body 17. The configuration is as follows.

In this configuration, calcium sulfite (hereinafter, CaS
The CaS Os slurry supplied into the oxidation tower main body 1 from the slurry liquid population 2 (indicated by Os) passes through the air inlet pipe 16 and is oxidized by fine bubbles ejected from the oxidation air bubble disperser 15 to become gypsum. However, at this time, only the coarse crystal gypsum settles out by overcoming the upward flow of fine bubbles from the classification body 17 and the classification bubble disperser 14 provided at the center of the bottom of the tower, and the settled coarse crystal gypsum is transferred to the classification body 17. The gypsum slurry is extracted from the gypsum slurry outlet 3 provided inside.

That is, the gypsum crystal grains can be classified by the quiet upward flow of fine bubbles from the classification body 17 and the classification bubble disperser 14.

The air bubbles from the air bubble disperser 14 for classification are small in quantity, and the design is such that no oxidation effect is expected.Therefore, the amount of air fed can be adjusted arbitrarily, and it can be adjusted as appropriate depending on the situation of the gypsum crystals to be taken out. good.

On the other hand, the amount of air fed from the oxidizing air bubble disperser 15 is large, and as the fine bubbles rise, an upward flow occurs in the periphery of the column, and a downward flow occurs in the center of the column. Regular convection occurs.

At this time, since the air from the classification bubble disperser 14 in the center of the column is small, it does not provide much resistance.

As described above, the gypsum crystals generated by air oxidation of CaSO3 in the oxidation tower main body 1 are carried inside the tower by the upward flow of fine bubbles from the oxidation air bubble disperser 15 in the peripheral area of the tower. However, only the gypsum with coarse crystal grains overcomes the upward flow of fine bubbles from the classification bubble disperser 14 and settles into the classification body 17. Oxidation, crystal coarsening, and classification are performed in the gypsum, which makes it possible to extract only high-quality, coarse-grained gypsum.

Therefore, the gypsum particles are not crushed by the pump blades as seen in the conventional example.

The coarse-grained gypsum extracted from the gypsum slurry outlet 3 is then introduced into the thickener 11, where it is further classified into gypsum crystals of the required particle size. At this time, if the amount extracted is large, the gypsum slurry is circulated. It is also possible to return a portion of it to the oxidation tower main body 1 by adjusting the piping valve 4 .

The oxidizing air bubble disperser 15 and the classification bubble disperser 14
may be structurally identical, so there will be no cost increase.

The structure may be as shown in FIGS. 3a and 3b, for example.

This bubble disperser has already been disclosed in Japanese Patent Application No. 47-73569.

In the figure, 18 is a rotor, 19 is a stator, 21
are protruding rods radially attached to the upper part of the rotor 18.

This structure has the following characteristics: (1) Since there is no large stirring blade, fine bubbles can be generated quietly without causing large liquid flow; (2) Eyes caused by crystals deposited at the gas jetting part. Because it does not cause clogging, when combined with the classification body, it generates a quiet upward flow of fine bubbles, thereby making the above classification possible.

Through experiments, the superficial velocity inside the classification fuselage was reduced to 3crfL/5.
It has been confirmed that when ec = 0.03 m/s or less, coarse gypsum crystals of 70 μm or more begin to settle, so the gypsum crystals can be classified relatively easily by adjusting the air flow rate.

The present invention is suitable for cases where the oxygen concentration in the combustion exhaust gas is high or when SO
2 As in the case of low concentration, CaS produced in the absorption tower
This is particularly effective when the gas side conditions are so bad that most of Oa/ΣH20 is oxidized.

According to the invention, it is possible to reduce the residual amount of Ca SO
This is because -HH2O content can be effectively used to produce high-quality, coarse-grained gypsum crystals.

The effects of the present invention are as follows.

(1) Only gypsum with large particle size can be recovered.

This is particularly effective when the gas side conditions are bad, for example when the 02/SO2 ratio is large.

(2) Water can be easily separated using a centrifuge, and the amount of water adhering to gypsum can be reduced, making it possible to improve quality.

(3) Since there is not much difference from conventional equipment, increases in equipment costs and maintenance costs are extremely small.

As described above, the present invention provides an oxidation tower for a flue gas desulfurization gypsum recovery method that makes it possible to recover only high-quality, coarse-grained gypsum, and has great industrial value.

[Brief explanation of drawings]

Fig. 1 is an overall view of an embodiment of the present invention, Fig. 2 is a detailed view of the main parts of the embodiment of Fig. 1, and Fig. 3a is an example of a bubble disperser used in the embodiment of Fig. 1. Longitudinal cross-sectional view, b is A- of a
It is a view from arrow A. In the figure, 1... oxidation tower main body, 2...
・CaSO3 slurry liquid inlet, 3...Gypsum slurry outlet, 4...Gypsum slurry circulation piping valve, 5
...Gypsum slurry outlet, 6...Air inlet header, 7...Bubble disperser air inlet pipe control valve, 8...Air outlet, 9 ······Liquid surface,
10... Slurry pump, 11...
Thickener, 12... Concentrate outlet, 13...
... Filtrate outlet, 14... Bubble disperser for crystal classification, 15... Bubble disperser for oxidizing air, 16...
... Air inlet pipe, 17 ... Classification body, 18
...Rotor, 19 ...Stator, 2
0... Rectifier cylinder, 21... Protruding rod.

Claims (1)

[Claims] 1. In an oxidation tower for flue gas desulfurization gypsum recovery method in which calcium sulfite is air-oxidized to gypsum, a plurality of bubble dispersers for oxidizing air are arranged around the bottom of the oxidation tower main body, and at the center of the bottom. An oxidation tower for flue gas desulfurization gypsum recovery method, characterized in that a bubble disperser for classification is installed in the classification body, and a gypsum slurry outlet is provided in the classification body.