JP5578125B2 - Non-condensable gas processing equipment - Google Patents

Description

  The present invention relates to a non-condensable gas processing apparatus, and more particularly to a non-condensable gas processing apparatus suitable for application when reducing non-condensable gas ejected together with steam in geothermal power generation into the ground through a reduction well.

  Conventionally, in geothermal power generation, a production well is excavated from the ground with respect to a high-temperature geothermal fluid layer in the deep underground, and the accumulated geothermal fluid is self-injected to the ground through this production well, and the geothermal fluid holds it. Electricity is generated by rotating the turbine with thermal energy.

  At that time, the geothermal fluid may be separated into steam and hot water by a steam separator, and the steam turbine may be directly rotated by the steam, or the steam and the hot water may be heat exchanged with another working medium. In some cases, the stored energy is transferred to the working medium and the turbine is rotated by the working medium. In addition, condensate condensed with hot water or steam is often returned to the ground via a reduction well.

  In such a geothermal power generation facility, the non-condensable gas contained in one steam separated from the water is generally separated and extracted and released to the atmosphere because it hinders power generation. As a result of this increase, a method has been proposed for underground reduction while maintaining a predetermined pressure together with the other hot water.

  For example, in Patent Document 1, as shown in FIG. 1, drainage Qe discharged from the underground is supplied from above to a reduction well 101 made of a vertical downcomer by a pump 102, and above the ground surface 103. A technique is disclosed in which non-condensable gas Qg is supplied to the ground portion by a blower 104 and is accompanied by drainage (liquid phase) to reduce the depth to the deep underground. In this case, the supply pressure of the non-condensable gas is approximately the top pressure of the reducing well.

  Thus, when entraining the non-condensable gas in the drainage, it is important to prevent the non-condensable gas (gas phase) from flowing back upward in the reduction well. By maintaining the apparent flow velocity of the gas phase in a specified relationship, the flow mode after the gas-liquid mixing point is changed from a floss flow having a large gas phase volume to a slag flow, as shown in FIG. It is said that the gas phase can be entrained in the descending liquid phase so that the flow becomes a thin bubble flow.

  Further, in Patent Document 2, in order to supply the non-condensed gas in a compressed state to the deep depth of the reduction well, as shown in FIG. 3, the ejector 202 is lowered to the deep underground as shown in FIG. A technique for injecting into a deep position as close as possible to the reducing layer is disclosed.

Japanese Patent Laid-Open No. 2-101351 JP-A-9-177507

“Two-Phase Flow Patterns and Void Fractions in Downward Flow”, Int. J. Multiphase Flow Vol.11, No.6, 1985

  However, the technique disclosed in Patent Document 1 has the following problems.

  In general, the flow rates and ratios of steam, hot water, and non-condensable gas in geothermal production wells are different for each power plant and for each well, but the temporal fluctuations in each well are relatively small. Therefore, the value is roughly determined for each well.

  Therefore, when the amount of liquid phase (reduced water) to be reduced to the underground is determined, the liquid phase reduction flow rate can be kept above the specified flow rate by properly selecting the diameter of the reduction well. The flow velocity of the gas phase entrained at that time is uniquely determined by the ratio of the geothermal fluid in each well (the amount of steam, the amount of hot water, the amount of non-condensed gas) in the configuration of the technique disclosed in Patent Document 1. Therefore, it is impossible to perform control so as to maintain the prescribed relationship as shown in Patent Document 1.

  In Patent Document 1, the apparent flow velocity Veo of the waste water is set to 1 m / s or more, and the apparent flow velocity Vgo of the gas is further suppressed to a range of Vgo <1.33Veo−0.41. The apparent flow velocity Vgo of gas, that is, the upper limit of the amount of non-condensable gas that can be reduced, is determined according to the amount of reducing water. For example, in the case of a geothermal power plant with a high ratio of non-condensable gas, Therefore, the flow rate condition of cannot be satisfied.

  To avoid this, it may be possible to increase the liquid flow rate by adding insufficient water, but it is easy to secure additional water from wells due to geothermal power plant location constraints. Another problem arises.

  Further, in the technique of Patent Document 2, it is assumed that the injection is performed at a deep position as close as possible to the reducing layer, but the deeper the position is, the higher the water pressure is applied. There is a problem of requiring power.

  The present invention has been made to solve the above-mentioned conventional problems, and in any geothermal production well, non-condensable gas can be reduced to the deep part of the reduction well with as little power as possible without adding new water. It is an object of the present invention to provide a non-condensable gas treatment apparatus that can be used.

The present invention is to supply non-condensable gas separated from steam produced together with hot water from a geothermal production well to the reducing water through the opening of the supply pipe, and then descend the reducing well together with the reducing water to underground. in the non-condensable gas treatment device for reducing the opening of the supply pipe, the non-condensable gas of the gas phase discharged from the opening portion, under mixed gas-liquid mixed phase with reduced water liquid phase, The above-mentioned problem is solved by installing the gas- liquid volume ratio (gas phase volume / (gas phase volume + liquid phase volume)) at a water depth where water pressure is 20% or less.

In the present invention, the upstream position before Symbol reinjection wells, the non-condensable gas is passed through, may also be absorption tower to remove the absorbing component contained in the non-condensable gas is disposed, In that case, you may make it the said absorption tower have at least one absorption ability of a physical absorption and a chemical absorption. Furthermore, the reduced water may include condensed water obtained by condensing the hot water and / or the steam.

  According to the present invention, the opening of the supply pipe that supplies the non-condensable gas to the reducing water in the reducing well can be reliably accompanied by the reducing water flowing down the non-condensed gas discharged and supplied from the opening. Since the geothermal fluid having an arbitrary gas-liquid ratio, that is, the geothermal fluid produced from an arbitrary production well, non-condensable gas separated from the steam is installed. Without adding water, it is possible to reliably return to the deep underground with as little power as possible.

Explanatory drawing which shows the outline | summary of the reduction | restoration well currently disclosed by patent document 1 Explanatory drawing which shows the effect | action and effect by patent document 1 Explanatory drawing which shows the outline | summary of the reduction | restoration well currently disclosed by patent document 2 The schematic block diagram which shows the principal part of the geothermal power generation equipment containing the non-condensable gas processing apparatus of one Embodiment which concerns on this invention. Flow chart showing an example of the procedure for determining the water depth

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 4 is a schematic configuration diagram showing an outline of a non-condensed gas processing apparatus according to an embodiment of the present invention together with peripheral equipment.

  The non-condensed gas processing apparatus of the present embodiment is configured so that the non-condensed gas G separated from the steam produced together with hot water from a geothermal production well (not shown) is supplied to the reducing water H containing the hot water. After being discharged / supplied, it has a function of lowering the inside of the reduction well 4 together with the reduced water H and returning it to the underground.

  In this embodiment, after the hot water 10 produced from the production well is supplied to the mixing tank 16 to which the alkaline solution 14 is poured and prepared into the alkaline mixed water H ′, the hot water 10 is upstream of the reducing well 4. Introduced into an absorption tower 18 having both physical and chemical absorption capabilities. Here, in addition to the hot water 10, the additional water 12 may be added as part of the reduced water as indicated by a two-dot chain line.

  Further, the steam 20 produced from the production well is sequentially supplied to, for example, two-stage heat exchangers 24A and 24B installed in the geothermal power generation facility 22, and rotates a power generation turbine (not shown). After being used as a heat source for converting a working medium made of an organic solvent such as pentane into a gas from a liquid, it becomes condensed water H ″ and is discharged from the heat exchanger 24B and is not contained in the vapor 20 The condensed gas G ′ is extracted from the heat exchanger 24A, where the non-condensed gas G ′ contains an absorbed component.

  The non-condensed gas G ′ extracted is passed through the alkaline mixed water H ′ supplied to the absorption tower 18 under a gauge pressure of 0.6 MPa, 160 ° C., for example, and is absorbed by physical absorption and chemical absorption. As the non-condensable gas G from which absorbed components such as sulfur dioxide, carbon dioxide gas, hydrogen sulfide and the like are removed, the compressor 26 is supplied by being press-fitted into the supply pipe 2 from above at a gauge pressure of, for example, 3.0 MPa. The

  On the other hand, the condensed water H ″ is mixed with the mixed water H ′ discharged from the absorption tower 18 as condensate and introduced into the reducing well 4 by the pump 28 as the reducing water H.

  In the present embodiment, the supply pipe 2 discharges and supplies the non-condensable gas G to the reduced water H at a position at a water depth L below the surface of the reduced water H introduced into the reducing well 4. It arrange | positions in this reducing well 4 so that the opening part 2A may correspond.

  Therefore, since the water pressure corresponding to the water depth L is applied as the head pressure to the opening 2A of the supply pipe 2, the non-condensable gas G is discharged from the opening 2A against the head pressure. Therefore, it is supplied into the reduction well 4 in a state compressed to be equal to or higher than the head pressure.

  In the present embodiment, the water depth L of the opening 2A of the supply pipe 2 is determined according to the ratio of the volume of the non-condensable gas G to be reduced in the standard state to the volume of the reduced water H. Specifically, when the non-condensable gas G is a gas phase and the reduced water H is a liquid phase, the volume ratio (void ratio) of the gas and liquid expressed by the following equation is set.

    Void ratio = gas phase volume / (gas phase volume + liquid phase volume) (1)

  Now, a calculation method of the water depth L when the void ratio = α will be described.

Even if the water depth changes, that is, the water pressure changes, the volume of the liquid phase constituting the gas-liquid mixed phase state does not change. Therefore, assuming that the volume of the liquid phase is 1, and the volume at the water depth L of the gas phase separated from the reduced water (hot water + condensed water) of volume 1 is _VP , the equation (1) is The following formula.

V _P / (V _P +1) = α (2)

From this equation (2), V _P = α / (1-α). Therefore, in order to make the void ratio less than α, the volume of the gas phase at the water depth L is α / (1-α) of the liquid phase. Must be:

Accordingly, if the volume in the standard state of the gas phase separated from the volume of reducing water (1 atm = 0.1013 MPa) is V _S , this is expressed as α / (1-α) (= V compression ratio for compressing the _{P) n = (V S /} V P) becomes a _{V P = V S / n =} α / (1-α), n = V S (1-α) / α .

  Further, since the water pressure increases by 1 atmosphere every 10 m, the water depth L is set by the following equation.

L = [V _S (1−α) / α] × 10 [m] (3)

Assuming that 1 m ³ of non-condensable gas is separated from 1 m ³ of reduced water in a standard state, the opening 2A is installed at a depth of [(1-α) / α] × 10 m or less.

  Therefore, for the non-condensable gas (gas phase) separated from the geothermal fluid produced at any geothermal power plant, the water depth L corresponding to the void ratio = α can be determined according to the flowchart of FIG.

First, the produced geothermal fluid is separated into a gas phase and a liquid phase (hot water + condensed water) (step S1), and a volume V _S under the standard state of the gas phase with respect to the liquid phase per unit volume is calculated (Step S2).

Next, the volume V _P of the gas phase when the void ratio is α is calculated from the equation (2) (step S3), the compression rate n is calculated from the obtained V _P (step S4), and the compression rate n is calculated from the compression rate. The water depth L is calculated from the equation (3) (step S5).

  Next, a specific example will be described.

  When the void ratio is set to 20% or less, the above expression (3) becomes the following expression (3 ').

L = 4V _S × 10 [m] (3 ′)

Thus, if 1 m ³ of non-condensable gas is separated from 1 m ³ of reduced water in a standard state, the opening 2A is installed at a depth of 4 × 10 m or less.

  Next, the operation of this embodiment will be described.

  The volume (volume) of the non-condensed gas G discharged from the opening 2A of the supply pipe 2 to the reduced water H decreases according to the head pressure (water pressure). Therefore, the volume ratio (void ratio) of the gas phase discharged into the liquid phase to the liquid phase can be controlled by this head pressure.

  This corresponds to controlling the apparent flow velocity of the gas phase in the technique disclosed in Patent Document 1. Therefore, by appropriately setting the water depth L of the opening 2A of the supply pipe 2, the gas phase (non-condensable gas G) can be brought into a gas-liquid mixed phase state without causing a backflow of the non-condensable gas G in the reduction well 4. It becomes possible to reduce to the deep underground while being accompanied by the liquid phase.

  Properly setting the water depth L is to set the water depth at which the head pressure (water pressure) is applied such that the volume ratio of the gas and liquid is 20% or less in the opening 2A. It is considered that the apparent flow velocity of the gas phase referred to in Patent Document 1 can be made sufficiently small, and the (c) bubble flow state shown in FIG. 2 can be maintained as the flow state. For example, Non-Patent Document 1 describes that setting the gas-liquid volume ratio to 20% or less is effective for maintaining the bubble flow state.

  In addition, it is effective for the backflow suppression of the non-condensed gas G, so that a gas-liquid volume ratio is made smaller than 20%, for example, like the technique currently disclosed by the said patent document 2, it is in the well bottom of the reduction well 4. If the non-condensable gas G is compressed to such a pressure, it is naturally possible to reduce it underground by gas injection, but in this case, a large amount of power is required to compress the gas. Therefore, it is effective to avoid excessive consumption of power by setting the gas / liquid volume ratio to a lower limit of up to about 5%.

  In this embodiment, according to the flow rate and gas-liquid ratio of the geothermal fluid for each power plant and each well, the non-condensable gas G is compressed to a water pressure of a water depth that can be transported downward in the gas-liquid mixed phase state and reduced water. By supplying it into the (liquid phase), it is possible to keep the compression to a minimum, so that the total amount of non-condensable gas can be reduced underground while reducing the gas compression power.

Further, in the present embodiment, since a part of the non-condensable gas is physically absorbed and chemically absorbed in the previous stage of the compressor 26, the absorbed component gas such as carbon dioxide gas can be removed thereby, so that the compressor the amount of gas treated by 26 further can be reduced, also the (3) also lead to a reduction in the compression ratio because it is equivalent to reducing the V _S in the equation, it is possible to significantly reduce the compression power It has become. In addition, since a corrosive gas such as sulfur dioxide or hydrogen sulfide can be selectively absorbed in the physical / chemical absorption step, the advantage that corrosion of the compressor 26 can be suppressed is also obtained.

  In addition, although the example which uses hot water and condensed water as reduced water was shown in the said embodiment, it is good also considering only hot water or only condensed water as reduced water. Further, it is of course possible to add well water or the like as the additional water shown together with a two-dot chain line in FIG. Moreover, although the example which provides an absorption tower upstream of a reduction well, ie, the front | former stage of a compressor, was shown, it is not limited to this. Furthermore, although the example in which the produced steam is used for heating the working medium that rotates the power generation turbine has been shown, it goes without saying that the steam may be directly supplied to the rotation of the power generation turbine.

DESCRIPTION OF SYMBOLS 2 ... Supply pipe 2A ... Opening part 4 ... Reduction well 10 ... Hot water 12 ... Additional water 14 ... Alkaline solution 16 ... Mixing tank 18 ... Absorption tower 20 ... Steam 22 ... Geothermal power generation equipment 24A, 24B ... Heat exchanger 26 ... Compressor 28 ... Pump G ... Non-condensable gas H ... Reduced water H '... Alkaline mixed water H "... Condensed water

Claims (4)

The non-condensable gas separated from the steam produced with the hot water from the geothermal production well is supplied to and mixed with the reduced water from the opening of the supply pipe, and then the reduced well is lowered with the reduced water and reduced to the underground. In the condensed gas processing device,
The gas- liquid volume ratio (gas phase volume / (gas phase volume / ()) is formed in the opening of the supply pipe under a gas-liquid mixed phase state in which a gas phase non-condensable gas discharged from the opening is mixed with liquid reducing water. A non-condensed gas processing apparatus, characterized in that it is installed at a water depth position where water pressure is applied so that the gas phase volume + liquid phase volume)) is 20% or less. 2. The non-condensation tower according to claim 1, wherein an absorption tower that allows the non-condensable gas to pass therethrough and removes the components to be absorbed contained in the non-condensed gas is disposed upstream of the reducing well. Condensed gas treatment device. The non-condensable gas processing apparatus according to claim 2 , wherein the absorption tower has at least one of absorptivity of physical absorption and chemical absorption. The non-condensed gas processing apparatus according to any one of claims 1 to 3 , wherein the reducing water includes condensed water obtained by condensing the hot water and / or the steam.

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