JPH1054338A - Desulfurization method in geothermal power generation facility and desulfurization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate hydrogen sulfide from discharge steam by using hydrogen sulfide included in noncondensable gas as sulfur dioxide gas in a combustion stroke, and absorbing its sulfur dioxide gas to absorbent slurry in an absorption reaction stroke. SOLUTION: Noncondensable gas E is burnt by a combustion furnace 11, and thereby, hydrogen sulfide in noncondensable gas E becomes sulfur dioxide gas. Combustion gas G including sulfur dioxide gas generated by burning noncondensable gas E is blown from a gas blow-in pipe 16 into the slurry in a reactor 12 as multiple fine bubbles, sulfur dioxide gas is absorbed being brought into contact with a calcium compound including slurry H in the reactor 12, it becomes purified desulfurization exhaust gas N in which sulfur dioxide gas is little included, and it is dispersed from the upper part of a cooling tower 7 into the atmosphere by a fan 7c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for removing harmful hydrogen sulfide from exhaust steam after use for power generation in a geothermal power plant, thereby contributing to environmental preservation. The present invention relates to a desulfurization method and a desulfurization device capable of recovering useful by-products.

[0002]

2. Description of the Related Art In geothermal power generation, geothermal steam ejected from wells using high heat stored inside the earth is introduced into a steam turbine for power generation, and is driven to generate power. It is regarded as an important energy source after hydropower, thermal power and nuclear power. By the way, geothermal steam usually contains a relatively large amount of carbon dioxide and a small amount of hydrogen sulfide,
In conventional general geothermal power generation equipment, the steam discharged from the turbine is cooled in a condenser and separated into condensed water and non-condensed gas, and the condensed water is returned to the reduction well or reused as cooling water, The non-condensable gas containing the hydrogen sulfide was released to the atmosphere as it was.

[0003] For this reason, hydrogen sulfide contained in the geothermal steam is contained in the non-condensable gas and is released to the atmosphere as it is, causing a problem of air pollution. Therefore, in recent years, as shown in, for example, JP-A-60-201011 and JP-A-64-8363, a configuration has been proposed in which a desulfurization device is provided to remove hydrogen sulfide in the non-condensable gas. . However, in such a conventional desulfurization apparatus, no consideration is given to the treatment and reuse of the removed sulfur, and the practical use is poor in terms of the easiness of the treatment of the desulfurization by-product and the recovery of the operating cost. Met.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention removes harmful hydrogen sulfide from steam discharged from a geothermal power plant after power generation, thereby contributing to environmental protection.
Generate and collect useful by-products from the removed sulfur,
It is an object of the present invention to provide a desulfurization method and a desulfurization apparatus capable of facilitating a process for treating a desulfurization by-product and reducing operating costs.

[0005]

In order to achieve the above object, a desulfurization method for a geothermal power plant according to claim 1 is provided.
In a geothermal power generation facility for generating electricity by driving a turbine with geothermal steam, a desulfurization method for removing hydrogen sulfide from non-condensable gas in steam discharged from the turbine and separated by a condenser, wherein the non-condensable gas is burned A combustion step of converting the hydrogen sulfide contained in the non-condensable gas into a sulfurous acid gas, and a combustion gas containing the sulfurous acid gas that has exited the combustion step.
Gas-liquid contact is made with an absorbent slurry containing a calcium compound and / or a sodium compound as an absorbent, and air is brought into gas-liquid contact with the absorbent slurry, thereby absorbing, oxidizing and neutralizing the sulfurous acid gas. And discharging the desulfurized exhaust gas, and converting the absorbent slurry into a sulfate slurry.

According to a second aspect of the present invention, there is provided a desulfurization method for a geothermal power plant, wherein a calcium compound is used as the absorbent, and in the absorption reaction step, gypsum slurry is generated as the sulfate slurry. A gypsum separation step for obtaining a gypsum cake by solid-liquid separation of the obtained gypsum slurry is provided.

[0007] A desulfurization method for a geothermal power plant according to a third aspect is characterized in that a gypsum heating step is provided in which the gypsum cake obtained in the gypsum separation step is heated to form hemihydrate gypsum.

According to a fourth aspect of the present invention, there is provided a desulfurization method for a geothermal power plant, wherein a sodium compound is used as the absorbent, and a slurry containing sodium sulfate is produced as the sulfate slurry in the absorption reaction step. And

Further, the desulfurization method for a geothermal power plant according to claim 5 is characterized in that a solid matter separation step of separating a suspended solid matter by filtering a sulfate slurry obtained in the absorption reaction step is provided. .

According to a sixth aspect of the present invention, there is provided a desulfurization apparatus for a geothermal power plant, wherein a non-condensed gas in steam discharged from the turbine and separated by a condenser is used in a geothermal power plant for driving a turbine with geothermal steam to generate power. A combustion furnace for burning the non-condensable gas, and a combustion gas containing a sulfurous acid gas discharged from the combustion furnace containing a calcium compound and / or a sodium compound as an absorbent. Gas-liquid contacting means for bringing the slurry into gas-liquid contact with the agent slurry, and air supplying means for supplying air to the gas-liquid contacting means and bringing the absorbent into the gas-liquid contact with the absorbent slurry absorbing the sulfurous acid gas. It is characterized by.

According to a seventh aspect of the present invention, there is provided a desulfurization apparatus for a geothermal power plant, wherein the non-condensed gas in the steam discharged from the turbine and separated by a condenser in a geothermal power plant for driving a turbine by geothermal steam to generate power. A desulfurization apparatus for removing hydrogen sulfide from a combustion furnace for burning the non-condensable gas, and a reactor for desulfurization by bringing a combustion gas containing sulfurous acid gas emitted from the combustion furnace into gas-liquid contact with a calcium compound-containing slurry. Air supply means for supplying air into the reactor and bringing the calcium compound-containing slurry having absorbed the sulfurous acid gas into gas-liquid contact, and solid-liquid separation means for performing solid-liquid separation on the gypsum slurry extracted from the reactor And characterized in that:

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First Example First, a first example using a calcium compound (in this case, limestone) as an absorbent will be described. FIG. 1 is a diagram showing an example of the configuration of a geothermal power plant equipped with the desulfurization device of the present embodiment. This geothermal power generation equipment uses a geothermal fluid A
, A gas-liquid separator 1 for separating water into geothermal steam B and hot water C, a turbine 3 driven by the geothermal steam B to operate a generator 2, and a geothermal steam B discharged from the turbine 3 by a pump 4. A condenser 5 for cooling by the supplied cooling water D to condense water, a cooling tower 7 for cooling water at the bottom in the condenser 5 extracted by the pump 6 and discharging the water as cooling water D; And a desulfurization device 10 for removing hydrogen sulfide from the non-condensable gas E in the geothermal steam B led out by the bleeding pump 8 from the upper part of the pump 5.

In this case, the condenser 5 has a spray nozzle 5a for spraying the cooling water D, and the geothermal steam B discharged from the turbine 3 comes into contact with the cooling water D sprayed from the spray nozzle 5a to condense. The water collects at the bottom together with the cooling water D and is led out by the pump 6. The cooling tower 7 is provided with a spray nozzle 7a for spraying water drawn out of the condenser 5 by the pump 6, a filler 7b for bringing the water into efficient contact with the outside air taken from the outer periphery and cooling it, And a fan 7c for generating a negative pressure for releasing the air upward from the upper portion and taking in the outside air.

Incidentally, a part of the water collected at the bottom of the condenser 5 may be returned to the ground through a reduction well. Also,
Part of the hydrogen sulfide contained in the steam B dissolves into the water accumulated at the bottom of the condenser 5 and becomes considerably acidic when left undisturbed. An alkaline agent such as caustic soda may be added to the water derived from. Further, a mist separator for removing mist may be provided on a pipe line for leading out the non-condensable gas E from the condenser 5. The hot water C separated by the gas-liquid separator 1 may be returned to the ground through a reducing well, but before returning to the ground, heat is recovered and used for a heated water pool, district heating, and the like. can do.

The desulfurization unit 10 includes a combustion furnace 11 for reacting the non-condensable gas E with air F and burning it, and a combustion gas G produced by burning the non-condensable gas E in the combustion furnace 11 and containing a calcium compound containing calcium gas therein. A reactor 12 (gas-liquid contacting means) for absorbing sulfuric acid gas by gas-liquid contact with a slurry H (absorbent slurry) and discharging desulfurized exhaust gas N, and a lot of air I in the slurry in the reactor 12 An air blowing pipe 13 (air supply means) for injecting as fine air bubbles, a solid-liquid separation means 14 such as a centrifugal separator for solid-liquid separation of a slurry J (gypsum slurry) extracted from the reactor 12, and The solid content K (gypsum cake of gypsum dihydrate) obtained by the solid-liquid separation means 14 is converted to 120
A gypsum heating device 15 such as a combustion furnace which is heated to about 150C to about 150C to form hemihydrate gypsum L.

Here, for example, a calcium compound M (absorbent) such as limestone (CaCO ₃ ) is appropriately supplied to the reactor 12 from a silo (not shown), and the combustion gas G is supplied to the bottom of the reactor 12. Gas injection pipe 16 provided in
From a large number of fine bubbles are blown into the slurry. In this case, the desulfurization exhaust gas N led out from the upper part of the reactor 12 is led to the upper part of the cooling tower 7 and
It is configured to be diffused into the atmosphere by c.

The supply amount of the calcium compound M is determined according to the amount of the sulfurous acid gas to be absorbed. In an actual operation, for example, the pH of the slurry in the reactor 12 is detected, and this pH value is determined. The supply amount may be controlled so as to be maintained in the weakly acidic region. Further, the calcium compound M may be supplied to the reactor 12 in a form of a slurry previously prepared in a separate slurry tank. Further, instead of the air blowing pipe 13 or the gas blowing pipe 16, a rotary atomizer or an arm-rotating sparger may be provided. Needless to say, the reactor 12 may be provided with a stirrer for promoting gas-liquid contact and preventing precipitation of solids.

Further, since the concentration of hydrogen sulfide in the non-condensable gas E is usually about 4%, and most of the remainder is carbon dioxide, the combustion furnace 11 is supplied with an auxiliary agent such as natural gas. Alternatively, for example, it is preferable to adopt a configuration in which a platinum-based catalyst is loaded so that the combustion reaction is sufficiently promoted. Further, the gypsum heating device 15 may be configured to burn a fuel such as natural gas to heat the gypsum cake K of gypsum, but for example, the geothermal fluid A as a heat source.
Alternatively, the gypsum cake K may be heated using the heat of the hot water C, or a combination of both may be used. If the heat of the geothermal fluid A or the hot water C is used, there is no need to secure a fuel such as natural gas, so that effective use of geothermal heat and reduction of operation costs can be achieved.

Next, the operation of the desulfurization device 10 in the above-described geothermal power generation facility, that is, an example of the desulfurization method of the present invention performed by the desulfurization device 10 will be described. First, by burning the non-condensable gas E in the combustion furnace 11,
According to the following reaction formula (1), hydrogen sulfide (H
₂ S) becomes sulfurous acid gas (SO ₂ ) (combustion step).

[0020]

Embedded image H ₂ S + 3 / 2O ₂ → SO ₂ + H ₂ O (1)

Next, a combustion gas G containing sulfurous acid gas produced by burning the non-condensable gas E is blown into the slurry in the reactor 12 as a large number of fine bubbles from a gas injection pipe 16, The sulfuric acid gas is absorbed by contacting with the slurry H containing calcium compound, and becomes a clean desulfurized exhaust gas N containing almost no sulfurous acid gas. In this case, the exhaust gas is diffused into the atmosphere from the upper part of the cooling tower 7 by the fan 7c. On the other hand, the calcium compound-containing slurry H in the reactor 12 is
While absorbing the sulfurous acid gas in the blown combustion gas G, it is further oxidized by contacting with a large number of bubbles blown from the air blowing pipe 13, and further causes a neutralization reaction to form gypsum (gypsum). Generated (absorption reaction step). The main reactions occurring during these processes are represented by the following reaction formulas (2) to (4).

[0022]

Embedded image SO ₂ + H ₂ O → H ⁺ + HSO ₃ ⁻ (2) H ⁺ + HSO ₃ ⁻ + 1 / 2O ₂ → 2H ⁺ + SO ₄ ²⁻ (3) 2H ⁺ + SO ₄ ²⁻ + CaCO ₃ + H ₂ O → CaSO _{4 · 2H 2 O + CO 2} (4)

Thus, in the steady state, the reactor 12
Inside, gypsum and a small amount of limestone are suspended,
These are supplied to the solid-liquid separation means 14 as a gypsum slurry J, and are dehydrated and taken out as a gypsum cake K of gypsum with little water (gypsum separation step). On the other hand, the filtrate O from the solid-liquid separation means 14 is sent to the reactor 12 in this case,
Circulated and used as the water that makes up the slurry. And
In this case, the gypsum cake K of dihydrate gypsum derived from the solid-liquid separation means 14 is heated to, for example, about 120 to 150 ° C. under normal pressure by the gypsum heating device 15 and attached water is evaporated,
The following reaction (5) gives β-type hemihydrate gypsum L (gypsum heating step).

[0024]

Embedded image CaSO ₄ .2H ₂ O → CaSO ₄ .1 / 2H ₂ O + 3 / 2H ₂ O (5)

It should be noted that hemihydrate gypsum itself has a relatively high commercial value, but when it is supplemented with water of crystallization, it changes into gypsum gypsum. Storage and transportation in consideration of moisture resistance are required. On the other hand, dihydrate gypsum is generally relatively low in commercial value at present, but it has sufficient properties as a cement raw material etc. with a large market scale, and it can be handled in an open stack. Is easy. Therefore, in some cases, the gypsum heating step may be omitted and the gypsum cake K of gypsum dihydrate may be carried out as a by-product as it is. In this case, the gypsum heating device 15 becomes unnecessary.

As described above, according to the above desulfurization apparatus or desulfurization method, harmful hydrogen sulfide in the non-condensed gas separated from the steam discharged from the geothermal power plant is removed, and it is industrially extremely useful as a by-product. Gypsum is obtained. For this reason,
It not only contributes to environmental preservation, but also eliminates the need for troublesome detoxification of by-products (for example, by diluting with a large amount of water), simplifies driving operations, and operates on the sales profit of gypsum, a by-product The industrially extremely practical advantage that the cost can be recovered is obtained. Further, as the gypsum heating device 15 for heating the dihydrate gypsum K, the geothermal fluid A
Alternatively, the use of the heat of the hot water C enables effective use of geothermal heat and further reduction in operation cost.

Second Example Next, a second example using a sodium compound (in this case, sodium hydroxide) as an absorbent will be described. FIG.
FIG. 3 is a diagram illustrating a configuration example of a geothermal power generation facility including the desulfurization device of the present example, and FIG. 3 is a diagram illustrating a detailed configuration example of the desulfurization device of the present example. The same components as those in the first example shown in FIG. 1 described above are denoted by the same reference numerals, and description thereof will be omitted.

This geothermal power generation equipment includes a gas-liquid separator 1 for separating geothermal fluid A jetted from a well into geothermal steam B and hot water C, as in the first example shown in FIG. A turbine 3 that is driven to operate the generator 2, and a condenser 5 that condenses water by cooling the geothermal steam B discharged from the turbine 3 with cooling water D sent from a pump 4.
A cooling tower 7 for cooling water at the bottom of the condenser 5 extracted by the pump 6 and discharging the water as cooling water D;
Desulfurizer 10a for removing hydrogen sulfide from the non-condensable gas E in the geothermal steam B led out by the bleeding pump 8 from above
And

The desulfurizer 10a converts the non-condensed gas E into air F
Furnace 11 for reacting and burning
The combustion gas G produced by burning the non-condensable gas E at
1 (sodium hydroxide) -containing absorbent slurry H1 is brought into gas-liquid contact, and furthermore, air I is brought into gas-liquid contact with the slurry to cause an oxidation reaction device 20 to proceed with the oxidation reaction. And a filtration facility 30 for solid-liquid separation of suspended solids from the sulfated slurry J1 (slurry containing sodium sulfate).

Here, the absorption reaction facility 20 comprises, for example, an absorption tower 21 and an oxidation tower 22 as shown in FIG. 3, for example. The detailed structure of the absorption reaction facility 20 will be described below with reference to FIG. The absorption tower 21 introduces the combustion gas G from the gas introduction section 21a on the lower side surface, and the gas outlet section 2 on the upper side.
1b is a counter-current type that is discharged as clean exhaust gas N, and a tank 21c for storing the absorbent slurry H1 is provided at the bottom.
Are formed. An absorbent M1 made of sodium hydroxide (Na (OH)) is appropriately supplied to the tank 21c from the silo 23.

The absorbent slurry H1 in the tank 21c
Is efficiently sucked up by the circulation pump 24, injected from the nozzles of the spray pipe 21d disposed above the absorption tower 21, and efficiently mixed with the combustion gas G introduced when flowing down through the filler 21e. It is configured to be in gas-liquid contact. Further, from the spray pipes 21f and 21g provided in the gas introduction part 21a or the gas derivation part 21b, make-up water W composed of industrial water or the condensed water in the condenser 5 is sprinkled, and the water content of the absorbent slurry H1 is reduced. Along with the replenishment, cooling of the combustion gas G and the above-mentioned reaction formula (2),
It is configured so that a part of the sulfurous acid gas absorption reaction shown in (3) is performed.

In the tank 21c of the absorption tower 21, a part of the air discharged from the blower 25 is blown into the slurry as many fine bubbles from the air blowing pipe 21h. This promotes the oxidation reaction described below. The slurry in the tank 21c is sent to the oxidation tower 22 as a slurry J0 containing a sulfate and a sulfite, in this case, by a piping line branched from the discharge side of the circulation pump 24. Further, in the case of FIG. 3, a mist eliminator 21i is installed in the gas outlet 21b of the absorption tower 21 to remove mist in the exhaust gas N discharged. Further, the derived desulfurization exhaust gas N is guided to the upper portion of the cooling tower 7 (shown in FIG. 2) and diffused into the atmosphere by the fan 7c as described above.

The supply amount of the absorbent M1 is determined according to the amount of sulfurous acid gas to be absorbed. In an actual operation, for example, the pH of the slurry circulating in the absorption tower 21 is detected and the pH value is determined. The supply amount may be controlled so that is maintained in the weakly acidic region. The supply amount of the makeup water W depends on the concentration of the slurry circulating in the absorption tower 21 and the tank 21c.
The liquid level may be detected and adjusted so as to maintain the concentration and the liquid level within an allowable range. Also, the absorbent M1 may be supplied to the absorption tower 21 in a form of a slurry previously prepared in a separate slurry tank. Further, instead of the air blowing pipe 21h, a rotary atomizer or an arm rotating sparger may be provided. The tank 21
It goes without saying that a stirrer for promoting gas-liquid contact and preventing precipitation of solids may be installed in c.

The oxidation tower 22 is configured such that the slurry J0 introduced from the absorption tower 21 stays therein for a predetermined time and then is discharged and sent to a drain filter supply pit 31 described later. A part of the air I is blown into the slurry as a large number of fine bubbles from the air blowing pipe 22a, whereby the oxidation reaction shown in a reaction formula (8) described below is sufficiently performed.

Next, the filtering equipment 30 comprises, for example, a drain filter supply pit 31 and a drain filter 32 as shown in FIG. 3, for example. The detailed configuration of the filtering equipment 30 will be described below with reference to FIG. The drain filter supply pit 31 is provided with a stirrer 31a and stores the sulfate slurry J1 discharged from the oxidation tower 22 and the diatomaceous earth Q supplied from the silo 33 while mixing and stirring. Slurry R in 31 is sent to drain filter 32 at a predetermined flow rate by slurry pump 34.
In this case, the diatomaceous earth Q functions as a filter aid in the filtration treatment in the drain filter 32.

In this case, the drain filter 32 adheres and filters suspended solids in the slurry R to the surface of the filter cloth of a filter element (not shown), and discharges the liquid as drain liquid P.
The removed suspended solids are dried by intermittent air blow with compressed air T, and are discharged as wet powders S via the hopper 35.

Next, the operation of the desulfurization device 10a in the above-described geothermal power plant, that is, an example of the desulfurization method of the present invention performed by the desulfurization device 10a will be described.
First, when the non-condensable gas E is burned in the combustion furnace 11, the hydrogen sulfide (H ₂ S) in the non-condensable gas E becomes sulfurous acid gas (SO ₂ ) according to the above-mentioned reaction formula (1) (combustion step). .

Next, the combustion gas G containing the sulfurous acid gas produced by burning the non-condensable gas E is supplied to the absorption tower 21 in the absorption tower 21.
The sulfuric acid gas is absorbed by coming into contact with the absorbent slurry H1 sprayed from the spray pipe 21d and the water W sprinkled from the spray pipes 21f and 21g, resulting in clean exhaust gas N containing almost no sulfurous acid gas. In this case, the air is diffused into the atmosphere from the upper part of the cooling tower 7 by the fan 7c. On the other hand, the absorbent slurry H1 circulating in the absorption tower 21 is oxidized while absorbing sulfurous acid gas in the blown combustion gas G, and further comes into contact with a large number of bubbles blown from the air blowing pipe 21h. Causes a neutralization reaction to cause sulfate (Na ₂ SO ₄ ) and sulfite (Na ₂ SO ₃ )
Is generated.

Thus, in the steady state, the absorption tower 21
In the tank 21c, the above-mentioned sulfates and sulfites and a small amount of unreacted absorbents and impurities are suspended and sent to the oxidation tower 22 as a slurry J0. And the oxidation tower 22
Then, an oxidation reaction is further performed to completely oxidize the sulfites in the slurry J0 to sulfates, thereby completely eliminating the sulfites that cause COD (chemical oxygen demand) (absorption reaction step). .

During these treatments, the main reactions occurring in the gas-liquid contact of the combustion gas G in the absorption tower 21 are the reactions of the above-mentioned reaction formulas (2) and (3).
The main reactions occurring in the first tank 21c and the oxidation tower 22 are represented by the following reaction formulas (6) to (8).

[0041]

(Reaction in the absorption tower tank) H ⁺ + HSO ₃ ⁻ + 2Na (OH) → Na ₂ SO ₃ + 2H ₂ O (6) 2H ⁺ + SO ₄ ²⁻ + 2Na (OH) → Na ₂ SO ₄ + 2H ₂ O (7) (Reaction in oxidation column) Na ₂ SO ₃ + 1 / 2O ₂ → Na ₂ SO ₄ (8)

Thus, the sulfate slurry J1 discharged from the oxidation tower 22 becomes a slurry containing the above-mentioned sulfate, a small amount of the unreacted absorbent and a small amount of impurities. The above sulfate (Na
₂ SO ₄ ) has a high solubility and is mostly dissolved in the liquid, and the suspended solids in the sulfate slurry J1 contain impurities (Al ₂ O ₃ , Fe ₂ O ₃₎ mixed in the absorbent M1 and the like. Etc.) and undissolved unreacted absorbent. Then, such suspended solids are separated by the drain filter 32 together with the diatomaceous earth Q as a filter aid, and are discarded as wet powder S. On the other hand, the above-mentioned sulfate (Na ₂ SO ₄ ) is dissolved in the drainage liquid P from the drain filter 32, but since this sulfate is harmless, it can be disposed of very easily by discharging water.

As described above, according to the above desulfurization apparatus or desulfurization method, harmful hydrogen sulfide in the non-condensed gas separated from the steam discharged from the geothermal power plant is removed, and the by-product (sodium sulfate) is removed. Can be treated as drainage as it is. This contributes to environmental preservation, and eliminates the need for troublesome detoxification of by-products, simplifies driving operations, and provides industrially extremely practical advantages. In particular, in the case of this example, a large-sized solid-liquid separation device (for example, a centrifugal separator) is unnecessary as compared with the above-described embodiment in which gypsum is used as an absorbent as gypsum (first example), In addition, since there is no need to handle (transport and store) by-products, there is an advantage that facility costs and operation costs are lower.

It should be noted that the present invention is not limited to the above two embodiments, and various embodiments are possible. For example, the absorbent may be used in combination with a calcium compound and a sodium compound. In this case, since each sulfate containing gypsum is generated, it is necessary to provide a solid-liquid separation step using a centrifugal separator or the like and separate the generated gypsum. Since it contains sodium sulfate, it may be treated by water discharge or the like without reuse.
In this case, the solid content separated by solid-liquid contains an unreacted absorbent and impurities in the above-mentioned absorbent in addition to gypsum, but this is not a problem because the amount is small compared to the amount of gypsum.

Further, in the configuration example shown in FIG. 3, the oxidation tower 22 is provided separately from the absorption tower 21. However, depending on the amount of air blown into the absorption tower tank 21c and the setting of the blowing method, the absorption tower is set. The oxidation tank 22 may be omitted so that the sulfite is entirely oxidized in the tower tank 21c. In addition, when the amount of impurities in the absorbent, which is a source of suspended solids in the slurry, is small, or when there is no problem even if these impurities are contained in the discharged liquid, the structure shown in FIG. The drainage filter supply pit 31 and the drainage filter 32 in the example, and the devices such as the silo 33 and the hopper 35 (that is, the filtration equipment 30) can be omitted.

[0046]

According to the desulfurization method for a geothermal power plant according to the present invention, hydrogen sulfide contained in the non-condensable gas is converted into sulfurous acid gas in the combustion step, and the sulfurous acid gas is absorbed by the absorbent slurry in the absorption reaction step. . For this reason, the discharged gas becomes a clean gas from which hydrogen sulfide has been removed.

In the absorption reaction step, the absorbent slurry is oxidized by gas-liquid contact with air after absorbing the sulfurous acid gas, and further causes a neutralization reaction to cause a sulfate (gypsum or / and sodium sulfate). ). And, among the above-mentioned sulfates contained in the sulfate slurry, sodium sulfate is a harmless substance and has a high solubility, so that it can be directly disposed of in the form of a liquid contained in the sulfate slurry. On the other hand, gypsum among the sulfates can be easily taken out as a useful by-product by, for example, solid-liquid separation of the slurry.
That is, the sulfate slurry can be easily treated anyway.

Therefore, according to the present invention, harmful hydrogen sulfide in the non-condensed gas separated from the steam discharged from the geothermal power plant is removed, and a sulfate slurry which can be easily treated as a by-product is produced. As a result, it can contribute to environmental conservation,
(Detoxification treatment such as dilution with a large amount of water) is not required, and an industrially practical advantage is obtained in that the driving operation is facilitated.

Further, in the desulfurization method for a geothermal power plant according to the second aspect, a gypsum slurry containing gypsum as a sulfate is produced using a calcium compound as an absorbent, and the gypsum slurry is solidified in a gypsum separation step. After the liquid separation, gypsum industrially useful as a raw material for building materials and the like is collected as a cake. That is, according to this desulfurization method, harmful hydrogen sulfide in the non-condensed gas separated from the steam discharged from the geothermal power plant is removed, and gypsum industrially extremely useful as a by-product in the form of a cake that is easy to handle. can get. For this reason, it can contribute to environmental preservation, eliminates the need for troublesome detoxification of by-products, simplifies driving operations, and easily recovers operating costs due to the sales profit of gypsum, a by-product. Industrially very practical advantages are obtained.

Further, in the desulfurization method for a geothermal power plant according to claim 3, in the gypsum heating step, the gypsum cake obtained in the gypsum separation step is heated to form hemihydrate gypsum. For this reason, hemihydrate gypsum of higher commercial value is obtained as a by-product.

Further, in the desulfurization method for a geothermal power plant according to the fourth aspect, a slurry containing sodium sulfate is produced as the sulfate slurry, particularly using a sodium compound as an absorbent. For this reason, the produced sulfate slurry can be easily disposed of as a slurry mainly containing only harmless sodium sulfate. That is, according to this desulfurization method, harmful hydrogen sulfide in the non-condensed gas separated from the steam discharged from the geothermal power plant is removed, and the sulfate as a by-product can be easily disposed of as a harmless slurry. This contributes to environmental preservation, and eliminates the need for troublesome detoxification of by-products, as well as solid-liquid separation, transport, and storage of by-products using large-scale equipment (such as a centrifuge). As a result, there is obtained an industrially practical advantage that the driving operation is significantly facilitated.

Further, in the desulfurization method for a geothermal power plant according to the fifth aspect, a solid separation step of filtering a sulfate slurry obtained in the absorption reaction step to separate suspended solids is provided. Therefore, even when impurities contained in the absorbent or the like are mixed, these impurities are removed as the suspended solids, and the filtrate can be easily disposed of as a harmless waste liquid rather than containing only sodium sulfate.

In the desulfurization apparatus for a geothermal power plant according to the sixth and seventh aspects, the hydrogen sulfide contained in the non-condensed gas is converted into sulfurous acid gas by combustion in the combustion furnace, and the sulfurous acid gas is supplied to the gas-liquid contact means (or the reaction vessel). Is absorbed by the absorbent slurry in the gas-liquid contact with the absorbent slurry.
For this reason, the gas discharged from the gas-liquid contact means is clean from which hydrogen sulfide has been removed. The absorbent slurry is
The sulfurous acid gas is absorbed, oxidized by gas-liquid contact with the air supplied by the air supply means, and further causes a neutralization reaction, thereby producing a sulfate corresponding to the type of the absorbent (gypsum or / and sodium sulfate). Is a slurry containing

[0054] Among the above-mentioned sulfates contained in the slurry, sodium sulfate is a harmless substance and has a high solubility, so that it can be directly discarded as it is contained in the liquid in the slurry. On the other hand, gypsum of the sulfate is, for example, by solid-liquid separation of the slurry,
It can be easily extracted as a useful by-product. That is, the slurry can be easily processed anyway.

Therefore, according to the present invention, the harmful hydrogen sulfide in the non-condensed gas separated from the steam discharged from the geothermal power generation facility is removed, and a slurry which can be easily treated as a by-product is produced, and the harmless hydrogen is produced. A plaster that can be disposed of as a wastewater or that is industrially very useful. This contributes to environmental preservation, and eliminates the need for troublesome detoxification of by-products (for example, detoxification by diluting with a large amount of water, etc.), and facilitates driving operations.
In addition, when the by-product is gypsum, an extremely practical industrial advantage is obtained that the operating cost can be recovered by the sales profit.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an entire geothermal power generation facility according to a first example of the present invention.

FIG. 2 is a diagram showing an entire geothermal power generation facility as a second example of the present invention.

FIG. 3 is a diagram showing a detailed configuration of a desulfurization device according to a second example of the present invention.

[Explanation of symbols]

 Reference Signs List 3 Turbine 5 Condenser 10, 10a Desulfurizer 11 Combustion furnace 12 Reactor (gas-liquid contact means) 13 Air blowing pipe (air supply means) 14 Solid-liquid separation means 15 Gypsum heating device 21 Absorption tower (gas-liquid contact means) 21h Air blowing pipe (air supply means) 22 Oxidation tower 22a Air blowing pipe (air supply means) 30 Filtration facility 32 Drain filter H Absorbent slurry (calcium compound-containing slurry) H1 Absorbent slurry (sodium compound-containing slurry) J Sulfate slurry (gypsum slurry) J1 Sulfate slurry (slurry containing sodium sulfate) M Absorbent (calcium compound) M1 Absorbent (sodium compound) N Desulfurization exhaust gas

Claims (7)

[Claims] 1. A desulfurization method for removing hydrogen sulfide from non-condensable gas in steam discharged from the turbine and separated by a condenser in a geothermal power plant that generates electricity by driving a turbine with the geothermal steam. A combustion process in which the non-condensable gas is burned to convert the hydrogen sulfide contained in the non-condensed gas into a sulfurous acid gas; and a combustion gas containing the sulfurous acid gas that has exited the combustion process contains a calcium compound and / or a sodium compound as an absorbent. The absorbent slurry is brought into gas-liquid contact, and air is brought into gas-liquid contact with the absorbent slurry to absorb, oxidize and neutralize the sulfurous acid gas, discharge desulfurized exhaust gas, and discharge the absorbent slurry. A desulfurization method for a geothermal power plant, comprising: an absorption reaction step of converting a sulfuric acid slurry into a sulfuric acid slurry. 2. A calcium compound is used as the absorbent, a gypsum slurry is generated as the sulfate slurry in the absorption reaction step, and a gypsum cake obtained by solid-liquid separation of the gypsum slurry obtained in the absorption reaction step is obtained. 2. A desulfurization method for a geothermal power plant according to claim 1, further comprising a step of obtaining a gypsum. 3. A desulfurization method for a geothermal power plant according to claim 2, further comprising a gypsum heating step of heating the gypsum cake obtained in the gypsum separation step to form hemihydrate gypsum. 4. The desulfurization in a geothermal power plant according to claim 1, wherein a sodium compound is used as said absorbent and a slurry containing sodium sulfate is produced as said sulfate slurry in said absorption reaction step. Method. 5. The desulfurization method in a geothermal power plant according to claim 4, further comprising a solid separation step of filtering a sulfate slurry obtained in the absorption reaction step to separate suspended solids. 6. A desulfurization apparatus for removing hydrogen sulfide from non-condensed gas in steam discharged from the turbine and separated by a condenser, wherein the desulfurization apparatus includes: A combustion furnace for burning non-condensable gas, and a gas-liquid contact for desulfurization by bringing a combustion gas containing sulfurous acid gas from the combustion furnace into gas-liquid contact with an absorbent slurry containing a calcium compound and / or a sodium compound as an absorbent. A desulfurization apparatus for a geothermal power generation facility, comprising: means for supplying air to the gas-liquid contacting means, and air-liquid contacting the absorbent slurry absorbing the sulfurous acid gas. 7. A desulfurization apparatus for removing hydrogen sulfide from non-condensed gas in steam discharged from the turbine and separated by a condenser, wherein the desulfurization apparatus includes: A combustion furnace for burning the non-condensable gas, a reactor for desulfurizing the combustion gas containing the sulfurous acid gas coming out of the combustion furnace with a calcium compound-containing slurry in gas-liquid contact, and supplying air into the reactor to supply the air. Geothermal power generation, comprising: air supply means for bringing the calcium compound-containing slurry which has absorbed sulfurous acid gas into gas-liquid contact, and solid-liquid separation means for solid-liquid separation of the gypsum slurry extracted from the reactor. Desulfurization equipment in equipment.