JP2001120949A - Hydrogen sulfide removing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen sulfide removing method capable of simplifying the removing process of the hydrogen sulfide and reducing the initial cost and the operation cost of a device. SOLUTION: The overflow waste water of a cooling tower is used at an absorption tower 112 as an absorbing solution, moreover, an oxidizing agent is added to the waste water to oxidize the hydrogen sulfide in noncondensing gas in the waste water in the absorption tower 112, and the waste water containing the formed sulfur is removed and returned under the ground together with hot water through a restoration well 105 to prevent the discharge of the hydrogen sulfide to the atmosphere. In such a way, the handling time of sulfur recovery, waste water retreatment, or the like, after decomposing the hydrogen sulfide is eliminated, and the device is simplified, and the state hardly releasing the hydrogen sulfide to the atmosphere and hardly exerting adverse influence on the surrounding atmosphere is realized with a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing hydrogen sulfide from uncondensed gas discharged to the outside in a geothermal power plant, and more particularly to a method for removing and installing hydrogen sulfide at low cost. About.

[0002]

2. Description of the Related Art In a geothermal power plant, a power generation turbine is driven by geothermal steam collected from underground to drive a generator to generate power. In this geothermal steam, non-condensation which is not condensed by a condenser is used. Contains gas. Conventionally, non-condensable gas is separated from condensed water by a condenser, separated from condensable vapor by a gas extractor, and sent to the top of the cooling tower for cooling condensed water (cooling air discharge side) and discharged. Is done. In the cooling tower, a large amount of air is used for cooling, and the used air is discharged into the atmosphere from the top, so the non-condensable gas is diluted by the exhaust from the cooling tower, and together with the exhaust in a state where the concentration is significantly reduced. Diffuses into the atmosphere. This non-condensable gas contains hydrogen sulfide, and since hydrogen sulfide has recently become a problem as a cause of offensive odor, various methods for removing hydrogen sulfide have been proposed. FIG. 3 shows an example of a geothermal power plant to which such a conventional hydrogen sulfide removal method is applied. FIG. 3 is a schematic configuration diagram of a geothermal power plant using a conventional hydrogen sulfide removal method.

As shown in FIG. 3, a geothermal power plant 100 using a conventional hydrogen sulfide removing method includes a production well 101 for extracting a geothermal fluid from underground, a separator 102 for separating the geothermal fluid into steam and hot water, A silencer 103 for reducing noise caused by a blast from the production well 101, a steam reservoir 104 for temporarily storing steam, a reduction well 105 for discharging hot water separated by the separator 102 to the underground, and power for power generation by the steam. Steam turbine 106 to be obtained, and generator 107 rotated by steam turbine 106 to generate electric power
A condenser 108 for condensing the steam, a cooling tower 109 for cooling the condensed water exiting the condenser 108, and a gas extraction for extracting non-condensable gas from the gas separated from the condensed water in the condenser 108. The apparatus includes a vessel 110 and a hydrogen sulfide removing device 111 for selectively removing hydrogen sulfide contained in non-condensable gas.

As a conventional hydrogen sulfide removing method in the hydrogen sulfide removing device 111 of the geothermal power plant 100, a wet method such as a low-cat method or a Stretford method is generally used. Among these wet methods, the low-cat method oxidizes hydrogen sulfide in an iron catalyst solution and collects and collects the generated solid sulfur in an aggregated state. In the Stretford method, hydrogen sulfide is oxidized in a vanadium catalyst solution, and the resulting solid sulfur is collected and collected in an aggregated state.

[0005] Further, as another method for removing hydrogen sulfide, a dry method is partially used. In this method, hydrogen sulfide is directly oxidized by an alumina and silica-based solid catalyst and converted into sulfur vapor, and finally recovered as molten sulfur.Since it is a dry system, operation and maintenance are simple, and the catalyst life is long, The operation cost can be reduced compared to other devices, and the space for installation can be reduced.

[0006] As a method for removing hydrogen sulfide used other than geothermal power generation, there are an amine claus method used in petroleum refining and a limestone-gypsum method used in thermal power generation.
In the former, a part of hydrogen sulfide is oxidized by using an alumina-based catalyst (solid) to be converted into sulfurous acid gas (SO2), and is recovered as molten sulfur by a Claus reaction (2H2S + SO2 → S + H2O). In the latter, hydrogen sulfide is converted into sulfur oxide by combustion, absorbed in limestone slurry, and further oxidized with the slurry to be recovered as gypsum.

[0007]

The conventional method for removing hydrogen sulfide is constituted as described above. In the low-cat method of the wet method, when the amount of discharged hydrogen sulfide is large, the consumption of the catalyst is severe, There is a problem that continuous replenishment or regeneration of the catalyst is required, and the operation cost becomes enormous. In addition, the Stretford method is often treated as industrial waste because the purity of the generated sulfur is low and it is difficult to reuse the sulfur, but there is a problem that the disposal cost is high. Was.

Further, the above-mentioned dry method has a problem that the operating cost can be reduced, but the equipment cost is relatively high. In addition, the Amine Claus method of petroleum refining and the limestone-gypsum method of thermal power generation require large-scale facilities, complicated processing systems, and are not suitable for unmanned operation. Therefore, there was a problem that introduction into a geothermal power plant was difficult.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a method for removing hydrogen sulfide, which simplifies a process for removing hydrogen sulfide and reduces initial costs and operation costs of equipment. .

[0010]

According to the present invention, there is provided a method for removing hydrogen sulfide, comprising the steps of extracting a geothermal fluid from a geothermal fluid in a condenser of the geothermal power plant using a geothermal fluid as energy for power generation. In the hydrogen sulfide removal method for removing hydrogen sulfide contained in the non-condensed gas, the overflow wastewater in a cooling tower that cools the condensed water condensed in the condenser is allowed to flow down from a predetermined absorption tower upper part, and the wastewater is discharged to the wastewater. While supplying a predetermined oxidizing agent, the non-condensable gas is blown from the lower part of the absorption tower, and the drainage and the hydrogen sulfide in the non-condensable gas are brought into contact inside the absorption tower, and the hydrogen sulfide is oxidized by the oxidizing agent. It converts sulfur into sulfur, extracts wastewater containing the sulfur from the absorption tower, and discharges it underground through a reduction well. As described above, in the present invention, the overflow wastewater of the cooling tower is used in the absorption tower as an absorbing solution, an oxidizing agent is further added to the wastewater, and the hydrogen sulfide in the non-condensable gas is oxidized in the wastewater by the absorption tower to produce Sulfur-containing wastewater is taken out and returned to the basement through a reducing well together with hot water to prevent the emission of hydrogen sulfide into the atmosphere, eliminating the need for sulfur recovery after decomposing hydrogen sulfide and reprocessing wastewater. In addition, the equipment can be simplified, and a state in which hydrogen sulfide is not released into the atmosphere and the surrounding environment is not adversely affected can be realized at lower cost.

In the method for removing hydrogen sulfide according to the present invention, if necessary, the oxidizing agent is iron (III) ion. As described above, in the present invention, by using iron (III) ions generated by acid-treating scrap iron and soil containing iron as the oxidizing agent, the oxidizing agent having excellent oxidizing power to hydrogen sulfide can be reduced. The cost can be obtained, and the operation cost of the hydrogen sulfide removal treatment can be significantly reduced.

In the method for removing hydrogen sulfide according to the present invention, if necessary, the oxidizing agent is hypochlorous acid. As described above, in the present invention, by using hypochlorous acid, which can be generated by electrolyzing hot water obtained together with geothermal steam, as an oxidizing agent, an oxidizing agent having excellent oxidizing power to hydrogen sulfide can be produced at low cost. Thus, the operation cost of the hydrogen sulfide removal treatment can be significantly reduced.

In the method for removing hydrogen sulfide according to the present invention, the oxidizing agent is, if necessary, fine air bubbles. As described above, in the present invention, as an oxidizing agent, a special oxidizing agent is separately applied to the absorption tower by generating microbubbles of air having an oxidizing power for hydrogen sulfide and bringing the air into contact with hydrogen sulfide in the absorption tower. This eliminates the need for a facility for producing and supplying the oxidizing agent, so that the oxidizing agent can be obtained at a lower cost, and the operating cost of the hydrogen sulfide removing treatment can be greatly reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram of a geothermal power plant using the hydrogen sulfide removal method according to the present embodiment, and FIG. 2 is a schematic configuration diagram of an absorption tower in the geothermal power plant using the hydrogen sulfide removal method according to the present embodiment.

As shown in the figures, a geothermal power plant 100 using the method for removing hydrogen sulfide according to the present embodiment has a configuration similar to that of the prior art. It is configured to have a tower 112,
The overflow wastewater in the cooling tower 109 is absorbed by the absorption tower 11
2 and a mechanism for sending the wastewater from the absorption tower 112 to the reduction well 105.

In the method for removing hydrogen sulfide according to the present embodiment, the non-condensable gas separated by the gas extractor 110 is blown from the lower part of the absorption tower 112, and the overflow wastewater of the cooling tower 109 is discharged from the upper part of the absorption tower 112. At the same time, the effluent is mixed with a predetermined oxidizing agent and the oxidizing agent is used to oxidize hydrogen sulfide contained in the noncondensable gas inside the absorption tower 112. The wastewater containing sulfur discharged from the absorption tower 112 is returned to the underground through the reduction well 105 together with the hot water.

The absorption tower 112 is a spray type well-known type, and is supplied with cooling tower wastewater from above and an uncondensable gas from below, and absorbs hydrogen sulfide contained in the noncondensable gas into the cooling tower wastewater. At the same time, hydrogen sulfide is oxidized in wastewater to obtain solid sulfur. The oxidizing agent is mixed with the cooling tower effluent, and oxidizes (takes hydrogen) from the hydrogen sulfide in contact with the cooling tower effluent in the absorption tower 112 to form solid sulfur. As the oxidizing agent, three types of hypochlorous acid, iron (III) ions, and fine air bubbles are used.

Hypochlorous acid is produced as an aqueous solution by electrolysis of hot water, taking advantage of the high chlorine ion concentration of hot water obtained from the production well 101 accompanying the steam. . Further, iron (III) ions are generated in a state of being contained in an aqueous solution by subjecting soil or the like containing scrap iron or iron to acid treatment. These are all added to the cooling tower drainage just before entering the absorption tower 112. On the other hand, fine air bubbles are generated by an air atomizer and sent from the lower part of the absorption tower 112.

Next, the operation of removing hydrogen sulfide from non-condensable gas by the method for removing hydrogen sulfide according to the present embodiment will be described. The overflow wastewater in the cooling tower 109 is introduced into the absorption tower 112, and flows down from above. This cooling tower drainage contains iron (II) obtained by acid-treating soil containing hypochlorous acid and scrap iron or iron obtained by electrolyzing hot water in advance.
I) Each aqueous solution of ions is mixed. Then, the non-condensable gas separated by the gas extractor 110 is blown from the lower part of the absorption tower 112, and at the same time, the fine bubbles of air generated by the air atomizer are blown.

While the cooling tower effluent flows down along the surface of the packed bed inside the absorption tower 112, hydrogen sulfide in the non-condensable gas contacts hypochlorous acid or iron (III) ions in the cooling tower effluent. Oxidized to form colloidal solid sulfur. Further, the hydrogen sulfide in the non-condensable gas is also oxidized by contacting with fine bubbles of air taken into the cooling tower drainage, and becomes colloidal solid sulfur, and the cooling tower drainage becomes a sulfur suspension. If necessary, the cooling tower drainage that has reached the lower part of the absorption tower 112 is again sent to the upper part of the absorption tower 112 by a pump and supplied to the inside, so that the oxidizing agent is effectively used.

The cooling tower wastewater, which contains hydrogen sulfide in a colloidal form and becomes a suspension, is discharged from the lower part of the absorption tower 112 and mixed with hot water to be reduced underground, and is reduced together with the hot water. It is discharged underground through the well 105. On the other hand, the remaining non-condensable gas (almost carbon dioxide gas) after the hydrogen sulfide has been absorbed into the wastewater as sulfur is discharged to the atmosphere from the upper part of the absorption tower 112 as it is.

As described above, in the method for removing hydrogen sulfide according to the present embodiment, the overflow effluent of the cooling tower 109 is used as the absorbing solution of the absorption tower 112, and the hydrogen sulfide in the non-condensable gas is oxidized in the absorption tower 112. The cooling tower wastewater, which has been oxidized by hypochlorous acid, iron (III) ions as an agent and fine bubbles of air, and has taken in the generated sulfur, is reduced to a reduction well 105
Return to the basement, eliminating the need for sulfur recovery and wastewater reprocessing associated with the removal of hydrogen sulfide, simplifying the processing equipment, and significantly reducing the overall removal of hydrogen sulfide from uncondensed gas released into the atmosphere. Cost can be reduced.

In the method for removing hydrogen sulfide according to the embodiment, hypochlorous acid, iron (II)
I) Ion and air microbubbles are used, respectively, but the configuration is not limited to this. Of the above three, one that uses low cost and high desulfurization efficiency is used. And the equipment and processing steps can be further simplified.

[0024]

As described above, according to the present invention, the overflow wastewater of the cooling tower is used as the absorbent in the absorption tower, and an oxidizing agent is added to the wastewater, and the hydrogen sulfide in the non-condensable gas is removed by the absorption tower. It oxidizes in the wastewater, takes out the wastewater containing the generated sulfur, returns it to the basement through a reduction well together with hot water, and prevents the discharge of hydrogen sulfide into the atmosphere. This eliminates the need for reprocessing and the like, simplifies the equipment, and has the effect of reducing the cost of achieving a state in which hydrogen sulfide is not released into the atmosphere and does not adversely affect the surrounding environment.

Further, according to the present invention, by using an iron (III) ion generated by acid-treating soil containing scrap iron or iron as an oxidizing agent, an oxidizing agent having an excellent oxidizing power to hydrogen sulfide can be obtained. The agent can be obtained at low cost, and there is an effect that the operation cost of the hydrogen sulfide removal treatment can be significantly reduced. Further, according to the present invention, by using hypochlorous acid that can be generated by electrolyzing hot water obtained together with geothermal steam as an oxidizing agent, an oxidizing agent excellent in oxidizing power to hydrogen sulfide can be produced at low cost. Thus, the operation cost of the hydrogen sulfide removal treatment can be significantly reduced.

Further, according to the present invention, as an oxidizing agent, fine bubbles of air having an oxidizing power for hydrogen sulfide are generated and brought into contact with hydrogen sulfide in the absorption tower, so that a special special treatment is applied to the absorption tower. This eliminates the need for an oxidizing agent generating / supplying facility, allows the oxidizing agent to be obtained at a lower cost, and has the effect of greatly reducing the operating cost of the hydrogen sulfide removal treatment.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a geothermal power plant using a hydrogen sulfide removal method according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an absorption tower in a geothermal power plant using the hydrogen sulfide removal method according to one embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a geothermal power plant using a conventional hydrogen sulfide removal method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Geothermal power plant 101 Production well 102 Separator 103 Silencer 104 Steam reservoir 105 Reduction well 106 Steam turbine 107 Generator 108 Condenser 109 Cooling tower 110 Gas extractor 111 Hydrogen sulfide removal device 112 Absorption tower

Claims (4)

[Claims] 1. A geothermal power plant that uses a geothermal fluid as energy for power generation, and removes hydrogen sulfide contained in an uncondensable gas extracted from a geothermal fluid in a condenser of the geothermal power plant by a gas extractor. In the hydrogen removal method, the overflow wastewater in the cooling tower that cools the condensed water condensed in the condenser flows down from the upper part of the predetermined absorption tower, and supplies a predetermined oxidizing agent to the wastewater, and from the lower part of the absorption tower. The non-condensable gas is blown, the waste water and the hydrogen sulfide in the non-condensable gas are brought into contact inside the absorption tower, and the hydrogen sulfide is converted into sulfur by oxidation with the oxidizing agent, and the waste water containing the sulfur is taken out of the absorption tower. A method for removing hydrogen sulfide, which is discharged underground through a reducing well. 2. The hydrogen sulfide removing method according to claim 1, wherein the oxidizing agent is iron (III) ion. 3. The method for removing hydrogen sulfide according to claim 1, wherein the oxidizing agent is hypochlorous acid. 4. The method for removing hydrogen sulfide according to claim 1, wherein the oxidizing agent is fine air bubbles.