JPH0536491Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wet flue gas desulfurization device, and particularly to a wet flue gas desulfurization device suitable for recovering by-product gypsum by a simple means.

[Conventional technology]

FIG. 3 shows a typical example of a conventional wet limestone-gypsum flue gas desulfurization system that uses limestone slurry as an absorbent to recover sulfur oxides in flue gas as gypsum.

In Figure 3, exhaust gas 5 generated from boilers etc.
flows from the side of the absorption tower 1 and comes into countercurrent contact with the absorbent slurry sprayed by the nozzle 3 by the circulation pump 2.

The exhaust gas 5 from which sulfur oxides have been absorbed and removed through this contact is discharged from the top of the absorption tower 1 to the outside of the system after the mist of absorbent slurry is removed by a mist eliminator 4.

On the other hand, the absorbent slurry that has absorbed sulfur oxides is
It falls and is temporarily stored in the circulation tank 21 provided at the bottom of the absorption tower 1. Then, the absorption treatment of the sulfur oxides sprayed by the nozzle 3 is repeated via the circulation pump 2. Here, since the absorbent slurry stored in the circulation tank 21 has a sedimentation property, a stirrer 8 (usually 3 to 8 units) is installed on the side wall of the circulation tank 21 to prevent solid matter from settling in the absorbent slurry. (Multiple units are installed.) In addition, air is supplied from the supply pipe 7 to the vicinity of the agitator 8, and the absorption products (mainly sulfites) generated by absorbing sulfur oxides in the circulation tank 21 are converted into safe sulfates (gypsum). A method has also been adopted to convert it into (Refer to Japanese Utility Model Application Publication No. 59-020608) A part of the reaction product slurry (hereinafter simply referred to as gypsum slurry) generated in the circulation tank 21 and converted into stable sulfate (gypsum) is removed by the extraction pump 9. The concentration (approximately 18~
After being concentrated to 38 Wt%), it passes through the gypsum separator supply tank 16, the gypsum separator supply pump 17, and the gypsum separator slurry supply valve 22 to the gypsum separator 1.
It is dehydrated at 0 and recovered as gypsum 11, which is a by-product.

The waste liquid from the gypsum separator 10 is collected into the gypsum concentrator 18 via the drain tank 12 and the drain pump 14, and is stored in the supernatant tank 15 together with the supernatant water produced when the gypsum slurry is concentrated.
It is reused as make-up water (dilution water) 13 for the absorbent in the wet flue gas desulfurization equipment.

Although the gypsum separator 10 performs batch processing, the gypsum separation supply pump 17 is provided with a gypsum separator slurry supply valve 22 and a slurry return pipe 23 for continuous operation, thereby dealing with batch processing.

A cross section of the circulation tank 21 is shown in FIG. 4, and the agitators 8 are arranged at an angle of inclination α of 10° to 20° with respect to the respective orthogonal axes passing through the center, and the settled solids 20 are placed in the central member. Deposited.

[The problem that the idea aims to solve]

In the conventional technology, in order to recover gypsum, which is a reaction product, it was necessary to send the gypsum slurry extracted from the circulation tank to a gypsum concentration chamber to obtain a concentration that can be supplied to a gypsum separator.

An object of the present invention is to provide a simplified wet flue gas desulfurization system that does not require a gypsum concentrator and supplies slurry with a concentration that can be supplied to a gypsum separator.

[Means to solve the problem]

In order to achieve the above object, the wet flue gas desulfurization equipment according to the present invention circulates an absorbent slurry in which limestone slurry absorbs sulfur oxides in the gas to be treated through a nozzle using a circulation pump to absorb the sulfur oxides. an absorption tower equipped with a circulation tank for agent slurry at the bottom and an agitator on the side thereof to prevent solid matter from settling and an air supply pipe for converting the absorbent slurry into gypsum slurry;
In a wet flue gas desulfurization system that is equipped with a gypsum separator that separates gypsum from gypsum slurry of a predetermined concentration, a extraction cone is installed at the bottom of the circulation tank at approximately the center, and high-concentration slurry is extracted from the extraction cone. A slurry extraction pipe and a slurry return pipe from the slurry extraction pipe are provided, and a make-up water cleaning line is connected to each slurry extraction pipe and return pipe.

[Effect]

According to the present invention, suspended solids in the gypsum slurry in the circulation tank are deposited at the center of the bottom of the circulation tank of the absorption tower by the interference portion of the slurry flow generated by the agitator.

Therefore, the central part of the bottom of the circulation tank has the function of locally concentrating the slurry, and by adjusting the intensity of the agitation flow, a suitable amount of gypsum slurry is deposited in the extraction cone.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the gas to be treated (exhaust gas) 5 generated in a boiler or the like flows in from the side of the absorption tower 1 and comes into countercurrent contact with the absorbent slurry sprayed from the nozzle 3 by the circulation pump 2. The treated gas 5 from which sulfur oxides have been absorbed and removed is discharged from the top of the absorption tower 1 to the outside of the system after the mist of absorbent slurry is removed by a mist eliminator 4.

On the other hand, the sulfur oxides in the gas to be treated 5 are absorbed into the limestone slurry 6 to become an absorbent slurry, and the absorbent slurry is once stored in the circulation tank 21 and then sprayed from the nozzle 3 again via the circulation pump 2. The absorption process for sulfur oxides is repeated, and the slurry is stored in a circulation tank 21 with a flat bottom. 8 units)
an absorption tower 1 equipped with a stirrer 8 and an air supply pipe 7 for converting the absorbent slurry into gypsum slurry in a lower circulation tank 21; and a gypsum separator 10 for separating gypsum 11 from the gypsum slurry of a predetermined concentration. In the installed wet flue gas desulfurization equipment, circulation tank 2
A slurry extraction pipe 24 corresponding to the absorption pipe of the gypsum separator supply pump 17 that extracts high-concentration slurry from the extraction cone 28 is provided at approximately the center of the bottom of the slurry extraction pipe 24, and In addition to providing a slurry return 23 that returns to the extraction cone 28, a supernatant water buffer 25 and a supernatant water intake weir 26 are provided inside the absorption tower 1, and each of the slurry extraction pipe 24 and the slurry return pipe 23 is connected to makeup water 13. This configuration includes a cleaning line 29 for cleaning.

In addition, the supernatant water buffer 25 is provided at a level where the slurry flow above the agitator 8 does not act.
The width of the surrounding liquid surface is determined by the permissible sedimentation rate of solid particles in the supernatant water. A vent hole is provided above the liquid surface of the supernatant water baffle 25 to allow gas mixed in the slurry and oxidizing air to escape to the absorption tower 1.

The solids settled and deposited at the center of the bottom of the circulation tank 21 have a solid content concentration of 40 to 80% (the average slurry concentration in the circulation tank is about 9 to 10%), and can be reduced by adjusting the intensity of the stirring flow. , it is possible to obtain a concentration of 18 to 35% that can be supplied to the gypsum separator 10,
The withdrawal pump, gypsum concentrator and gypsum separator feed tank of conventional equipment can be omitted.

In addition, the drained liquid from the gypsum separator 10 is collected into the circulation tank 21 via the drain tank 12 and the drain pump 14, and the supernatant water that has passed through one supernatant water intake weir 26 is stored in the supernatant tank 15. The water is then reused within the apparatus as make-up water (dilution water) 13 for the absorbent (limestone slurry) 6 via the supernatant water pump 19.

Next, the operation of this embodiment will be explained.

When stirring the gypsum slurry in the circulation tank 21 with the agitator 8 installed on the side wall of the circulation tank 21 of the absorption tower 1, by adjusting the capacity of the agitator 8, the gypsum slurry is placed in the center of the bottom of the circulation tank 21. It is possible to deposit the necessary amount of solid content in the slurry, and after adjusting in this way, the gypsum slurry is extracted from the bottom part of the circulation tank 21 with the gypsum separation supply pump 17, thereby removing the gypsum separator 10. It is possible to obtain a gypsum slurry with a concentration that can be directly supplied to

In addition, the solids in the gypsum slurry that accumulates in the bottom part of the circulation tank 21 are collected especially those having a large particle size (the larger the gypsum particle size, the better the quality of the gypsum).

In other words, the circulation tank 21 also has the function of gypsum concentration, and by being able to supply gypsum slurry at a supplyable concentration (18 to 35%) from the circulation tank 21 to the gypsum separator 10, it is possible to concentrate the gypsum. Yes, the gypsum separator supply tank and extraction pump are no longer necessary, and the system for recovering gypsum, a by-product, can be simplified.

Details of the bottom central portion of the circulation tank 21 in FIG. 1 are shown in FIG. 2.

A conical extraction cone 28 is provided at the tip of the slurry extraction pipe 24 with a gap between it and the bottom plate of the circulation tank 21, and the slurry return pipe 23 is also inserted into the circulation tank 21 and connected to the top 27 of the extraction cone 28. They are stacked one on top of the other, and the slurry is discharged from the slurry return pipe 23 in the direction of the arrow and used to prevent the formation of deposited solids.

The gypsum slurry is supplied to the gypsum separator supply pump 17
By suction, the slurry flows into the extraction cone 28 through the gap between the extraction cone 28 and the bottom plate of the circulation tank 21, and is sent to the gypsum separator 10 via the slurry extraction pipe 24.

When stopping the wet flue gas desulfurization equipment, stirrer 8,
The gypsum separator supply pump 17 continues to operate even when it is stopped, and the solid content in the absorbent slurry is transferred to the circulation tank 21.
Although this prevents the accumulation of the slurry on the bottom or inside the slurry extraction pipe 24, a cleaning line 29 and a cleaning valve 30 are provided in case of an unexpected loss of power. 17, when restarting, the cleaning valve 30 is opened to allow makeup water 13 to flow into the cleaning line 29 and the extraction cone 28, and the accumulated solids in the pipes are flushed out into the circulation tank 21 and resuspended. By doing so, troubles such as clogging of the slurry extraction pipe 24 are prevented when restarting the apparatus.

[Effect of idea]

According to the present invention, slurry of a predetermined concentration can be extracted from the extraction cone installed at the bottom of the circulation tank of the absorption tower of the wet flue gas desulfurization equipment, so that the gypsum can be concentrated.
The gypsum separator supply tank and extraction pump are not required, simplifying the equipment.

Furthermore, since gypsum concentration, which requires a large installation area, is not necessary, the apparatus can be arranged compactly.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
The figure is a circuit diagram showing details of the slurry extraction pipe in the center of the bottom of the circulation tank in Figure 1, Figure 3 is a circuit diagram showing a conventional desulfurization device, and Figure 4 is a cross-sectional view of the circulation tank in Figure 3. It is. 1... Absorption tower, 2... Circulation pump, 3... Nozzle, 5... Gas to be treated, 6... Limestone slurry, 7
... Supply pipe, 8 ... Stirrer, 10 ... Gypsum separator, 11 ... Gypsum, 13 ... Make-up water, 23 ...
Slurry return pipe, 24... Slurry return pipe, 28...
Extraction cone, 29...washing line.

Claims (1)

[Scope of utility model registration request] An absorbent slurry in which the limestone slurry absorbs sulfur oxides in the gas to be treated is circulated through a nozzle by a circulation pump, and a circulation tank for the absorbent slurry is provided at the bottom, and solids are allowed to settle on the side of the slurry. In the wet flue gas desulfurization equipment, the wet flue gas desulfurization equipment is equipped with an absorption tower equipped with an agitator for preventing the absorption, an air supply pipe for converting the absorbent slurry into a gypsum slurry, and a gypsum separator for separating gypsum from the gypsum slurry of a predetermined concentration. ,
An extraction cone is provided inside the circulation tank at approximately the center of the bottom, and the extraction cone is provided with a slurry extraction pipe for extracting high concentration slurry, a slurry return pipe from the slurry extraction pipe, and a slurry extraction pipe for each slurry extraction. A wet flue gas desulfurization device characterized in that a make-up water cleaning line is connected to a pipe and a return pipe.