JP4929188B2 - Geothermal power generation system, geothermal power generation apparatus and geothermal power generation method - Google Patents

Description

  The present invention relates to a power generation system, a power generation apparatus, and a power generation method using geothermal steam, and more particularly, to an apparatus and a method that take into account the response to aging of a steam turbine.

  In the geothermal power generation system, steam (geothermal steam) heated by underground magma is led to the ground by drilling a well, and this steam is directly introduced into the turbine to be used as a working fluid to obtain rotational power. is there. The energy of the geothermal steam is converted into velocity energy as the geothermal steam expands through a turbine stage composed of nozzles (stator blades) and moving blades. The geothermal steam having this speed acts on the rotor blades to generate a force for rotating the turbine rotor in which the rotor blades are implanted.

  Geothermal steam is generated when groundwater is heated by geothermal heat such as magma, so it contains corrosive components such as hydrogen sulfide and salt, scale components such as silica and calcium, and sand, mud, and iron oxide. Contains solid particles. In addition, since the geothermal steam is in a saturated state or a state close to saturation, the steam is highly humid inside the turbine, and the geothermal turbine is forced to be operated severely. Furthermore, the type and concentration of chemical components contained in geothermal steam, the size and amount of solids brought into the geothermal turbine, and the steam state of the geothermal steam vary depending on the geothermal zone and well where the geothermal turbine is installed, In addition, the fact that the same wells change over time makes the design of geothermal turbines more complex.

  The presence of corrosive gas such as hydrogen sulfide in the geothermal steam is due to the corrosion of the material and, over the years, deterioration and damage due to stress corrosion cracking and corrosion fatigue for the rotor blade, nozzle and turbine rotor. There are inherent factors that shorten the life of geothermal turbines. For example, damage due to corrosion fatigue generally occurs as a result of the superposition of the three elements of environment, material, and stress. It is difficult to completely avoid the superposition of these three elements for turbine parts that inevitably generate high stress because they rotate at high speed, such as nozzles, blades, and turbine rotors.

  Therefore, the materials and blade lengths used are naturally limited in practical use, and as a result, a certain upper limit is set for the output of the geothermal turbine. In other words, since the output scale per unit of the geothermal turbine is smaller than that of the thermal turbine, a plurality of small-sized turbines are often produced.

  On the other hand, there is a possibility that drain erosion and solid particle erosion will occur in the steam passages and seals of each part of the turbine due to the high wetness of the geothermal steam and the mixing of solid particles in the steam. In addition, wet steam and solid particles, combined with the presence of corrosive gas contained in geothermal steam, can cause a synergistic action of erosion and corrosion, and can further accelerate turbine damage. For this reason, a drain catcher is provided at the outlet of each turbine stage to discharge water droplets and solid particles out of the steam passage, and damage such as attaching an erosion shield to the tip of the final stage blade Preventive measures are taken.

  In an actual geothermal turbine plant, the corrosive environment may change in a more severe direction due to the secular change of the geothermal steam component due to long-term operation. There is an example of progress. Therefore, it is important for geothermal turbines to improve the operating rate while maintaining reliability and performance through efficient maintenance and maintenance against the progress of deterioration and corrosion over time. It has become a challenge.

  On the other hand, geothermal energy is clean energy that does not emit carbon dioxide, and improving the operating rate of geothermal plants leads to the suppression of power sources that emit carbon dioxide from thermal power plants, etc., so further expansion is desired from the viewpoint of environmental conservation. ing. Therefore, improving the plant performance and operating rate by improving the maintenance and maintainability of the geothermal turbine is an important theme that must be promoted from the viewpoint of protecting the global environment.

  In general, an axial flow turbine is adopted as a geothermal turbine, and it is composed of a casing, a turbine rotor built in the casing, and a multistage turbine stage structure in which nozzle blades that are stationary blades and rotating blades are combined. (See, for example, Patent Documents 1 and 2).

  The high-temperature and high-pressure geothermal steam expands through the nozzle blades to become high-speed steam, and this high-speed steam energy rotates the turbine rotor through the rotor blades. The turbine rotor is supported by front and rear bearings, coupled to the generator through a coupling at the shaft end, and transmits the rotational energy to the generator.

  Among the turbine stages, the moving blades in the plurality of stages including the final stage are operated under severe centrifugal stress due to rotation because the blade length is large. In order to maintain the reliability of the blade under such circumstances, the blade is designed to avoid blade resonance caused by the fact that the natural frequency of the blade matches an integer multiple of the rotational speed of the turbine rotor. For this reason, the blades of the rear multiple stages including these final stages are prepared as standard products of the turbine manufacturer, and are not designed for each turbine unit, but are designed according to the amount of exhaust steam and exhaust pressure of the turbine. Therefore, a method is adopted in which an appropriate one is selected and adopted from standard products.

  On the other hand, since the geothermal steam introduced to the geothermal turbine is natural energy generated by the groundwater being heated by geothermal heat such as magma, the steam conditions such as the pressure and temperature of the steam depend on the well depth at the site where the geothermal heat is excavated. However, it depends on other natural conditions, and this contributes to the hindrance to complete standardization of geothermal turbines.

  For this reason, the stage on the inlet side of the turbine, that is, the upstream side, is examined for the steam passage section so that the highest efficiency can be obtained according to the inlet steam conditions such as the inlet steam flow rate, pressure, and temperature of the turbine. Optimization design is made. That is, even if the turbine has the same output, if the steam conditions at the inlet are different, the shape and size of the nozzles and blades in the paragraph on the turbine inlet side are designed to have different shapes and values, and as a result, the same turbine will not be obtained. .

The bearing size for supporting the turbine rotor is set in consideration of the turbine rotor weight, the turbine rotor transmission torque, that is, the output, the critical speed of the turbine rotor, and the like. The coupling size is also determined from the output of the turbine rotor. Therefore, if the output of the turbine is different, these sizes are designed as different values.
JP-A-62-157207 JP 59-85402 A

  Some of the scale components such as silica and calcium contained in the geothermal steam, and solid particles such as sand, mud, and iron oxide are part of the surface of the nozzle and blades during the steam expansion process in the turbine steam passage. Adhere to. Accumulation of these scales on the blade surface reduces the effective throat area of the steam passage portion, and reduces the steam swallowing ability of the turbine, leading to a reduction in output.

  Since the geothermal steam is in a state of saturation or near saturation, a wet steam flow containing a large amount of drain is generated inside the turbine. This high wetness and the presence of solid particles in the steam cause damage to the seals in each part of the turbine, as well as rough skin due to drain erosion and solid particle erosion on the nozzle surface and blade surface. This is a major factor in the decline.

  The presence of corrosive gas contained in the geothermal steam may cause damage to the rotor blade and the turbine rotor due to stress corrosion cracking and corrosion fatigue due to synergistic action with the wet steam. The damage caused by the corrosive components contained in the steam is unique to each geothermal site because the chemical composition and concentration contained in the steam vary depending on the geothermal zone and well and change over time. Is required.

  In order to overcome the problems inherent to these geothermal turbines, the turbine is opened periodically, the nozzle blades, moving blades are scaled and polished, damaged seal packings are replaced, or each part is replaced. Inspection to confirm the soundness is performed. However, frequent turbine opening causes a decrease in the operation rate of the plant, which is not preferable from the viewpoint of improving the total efficiency including geothermal plant operation.

  For example, if it takes 25 days for one periodic turbine opening inspection of a single casing geothermal turbine, if this is done every two years, the annual average downtime will be 12.5 days. That is, the reduction in the operation rate for this inspection is a large value of 12.5 / 365 = 3.4%.

  In addition, if damage is found in the rotor blades, turbine rotors, or other large parts during open inspection, it will take a long time to procure and assemble the parts, greatly reducing plant downtime. The economic loss will be quite large.

  As a method for suppressing a decrease in the turbine operation rate due to the periodic turbine opening inspection, there is a method of preparing spare parts of a turbine such as a turbine rotor and a nozzle diaphragm. In other words, as soon as the turbine is opened, the contents are replaced with spare parts, and they are immediately assembled and put into operation. As a result, the downtime of the turbine can be minimized. The removed old product can be maintained, inspected and repaired until the next regular turbine opening.

  For example, if a spare turbine rotor or nozzle diaphragm is prepared and replaced, the number of days required to disassemble and assemble a single casing turbine is 7 days. Takes 3.5 days. The effect on the operating rate is 3.5 / 365 = 1.0%, which is a large improvement of 2.4% compared to the case without spare parts.

  However, as mentioned above, the inlet steam conditions of geothermal turbines vary widely for each steam well at the site, so it is impossible to cope with geothermal turbines at different sites with the same standard turbine. As a natural consequence, optimal design for each site has been carried out. That is, since the dimensions of the nozzle blades and the moving blades are different for each unit, provision of a spare turbine rotor or the like is required for each unit, which is difficult to realize from the viewpoint of economy.

  In view of the above circumstances, it is an object of the present invention to facilitate maintenance in a geothermal power generation system and improve economy.

  The present invention achieves the above object, and in one aspect, a plurality of multi-stage shafts each having a separate turbine rotor built in a separate turbine casing and designed for different steam conditions. A flow steam turbine, at least one generator coupled to at least one of the multi-stage axial steam turbines, and at least one auxiliary turbine rotor that can be commonly used for the plurality of multi-stage axial steam turbines; The multi-stage axial flow steam turbine includes a turbine casing, a plurality of bearings fixed to the turbine casing, and rotationally supported by the bearings and accommodated in the turbine casing. Turbine rotors and spare turbines in each turbine casing. Each of the rotors is disposed at both ends and can be coupled to other turbine rotors and generators, a plurality of rotor blades, and a plurality of bearing supports that can be supported by the bearings in contact with the plurality of bearings About the turbine rotor and the spare turbine rotor built in the turbine casing, the distance between the bearing support portions, the distance between the couplings, the maximum height of the moving blades and the coupling The dimensions of the blades in the turbine inlet side stage of the preliminary turbine rotor are the same as the height of the blades in the turbine inlet side stage of the plurality of multistage axial steam turbines. It is equal to.

In another aspect of the present invention, a plurality of multistage axial steam turbines, at least one generator coupled to the multistage axial steam turbines, and the multistage axial steam turbine and the generator are coupled. A multistage axial-flow steam turbine, each of which has a turbine casing, a plurality of bearings fixed to the turbine casing, and is rotatably supported by these bearings. A turbine rotor housed in a turbine casing, each of the turbine rotor and the spare turbine rotor in each turbine casing being disposed at both ends and coupled to another turbine rotor and a generator. A plurality of moving blades and a plurality of blades that are in contact with the plurality of bearings and can be supported by the bearings. Has a bearing support portion, said about the turbine rotor and the spare turbine rotor in each turbine casing, the distance between the bearing support portion, the distance between the coupling, the maximum height and the coupling of the rotor blade Are common to each other, and are configured to be operable by exchanging one of the turbine rotors in each turbine casing and the spare turbine rotor.

  According to still another aspect of the present invention, a plurality of multi-stage axial flow steam turbines each having a separate turbine rotor housed in a separate turbine casing and designed for different steam conditions are operated. A geothermal power generation method for storing at least one spare turbine rotor that can be commonly used in a multistage axial steam turbine of the present invention outside a turbine casing, the last stage of the plurality of multistage axial steam turbines and the spare turbine rotor. The blade length, the coupling dimension, the coupling span, the bearing dimension, and the bearing span of the blades are equal to each other, and the height of the moving blade in the turbine inlet-side stage of the preliminary turbine rotor is set to be equal to that of the plurality of multistage axial steam turbines. The plurality of multi-stage axial steam turbines equal to the largest of the rotor blade heights of the turbine inlet side paragraph; For what maintenance is required among the turbine rotor, and wherein, to replace them with the spare turbine rotor is removed from the turbine casing.

  According to this invention, the maintenance in the geothermal power generation system becomes easy, the operation rate of the geothermal power generation system can be improved, and the economic efficiency can be improved.

  Embodiments of a geothermal power generation system according to the present invention will be described below with reference to the accompanying drawings.

  First, a first embodiment will be described with reference to FIGS. FIG. 1 is an upper half longitudinal sectional view of one multistage axial flow turbine of the geothermal power generation system according to the first embodiment of the present invention, and FIG. 2 is an upper half longitudinal sectional view different from FIG. is there. 3 is a partial vertical sectional view of the first stage of the multistage axial flow turbine of FIG. 1, and FIG. 4 is a partial vertical sectional view of the first stage of the multistage axial turbine of FIG. Further, FIG. 5 is an upper half longitudinal sectional view of the spare turbine rotor in the first embodiment.

  In a geothermal turbine 10a shown in FIG. 1, a turbine stage 13a is arranged in a multistage structure and concentrically in a turbine casing 12a. The turbine stage 13a includes a plurality of nozzle blades 16a that are integrated with a nozzle diaphragm 15a fixed to the turbine casing 12a, and a plurality of blades 14a that are implanted in the turbine rotor 11a and disposed downstream of the nozzle blades 16a. It is configured by combining.

  The nozzle diaphragm 15a has a nozzle diaphragm outer ring 151a outside the nozzle blade 16a and a nozzle diaphragm inner ring 152a inside the nozzle blade 16a. The nozzle diaphragm outer ring 151a is supported and fixed inside the turbine casing 12a and arranged concentrically with the turbine rotor 11a, and the nozzle diaphragm inner ring 152a is arranged concentrically with the turbine rotor 11a inside the nozzle blade 16a.

  The turbine rotor 11a is rotatably supported by bearings 21a and 22a before and after the turbine. The distance between the centers of these bearings 21a and 22a is a bearing span L1a. Couplings 24a and 25a are provided at the shaft end of the turbine rotor 11a, and one of these couplings is coupled with a coupling of a generator (see FIGS. 12 to 14) to transmit rotational power to the generator. The distance between the outer surfaces of the couplings 24a and 25a is the coupling span L2a.

  The high-temperature and high-pressure steam guided from the geothermal well to the turbine enters the turbine steam chamber 17a and expands through the first stage nozzle blades 18a to become high speed steam, and this high speed steam energy is converted into the first stage rotor blades 19a. Rotational power is given to the turbine rotor 11a when passing through. The steam that has worked in the first paragraph performs work while being expanded in the succeeding paragraph in sequence, exits the final stage rotor blade 20a, and is then discharged to a condenser (not shown).

  The symbol of each component of the turbine 10b shown in FIG. 2 is shown by replacing the end “a” of the corresponding component symbol of the turbine 10a shown in FIG. 1 with “b”. In the geothermal turbines 10a and 10b, some of the steam conditions of the turbine, that is, the turbine inlet pressure, temperature, flow rate, or exhaust pressure of the geothermal steam obtained from the steam well, or the pressure of the two-stage flash steam, or the presence or absence thereof, etc. Is different.

  Here, the case where the turbine inlet steam volume flow rate of the geothermal turbine 10a is larger than the turbine inlet steam volume flow rate of the geothermal turbine 10b will be described as an example.

  As described above, the rotor blades in the last few stages including the final stage of the steam turbine are prepared as a standard design product of the turbine manufacturer in order to prevent the blades from resonating due to the excitation force related to the rotation of the turbine rotor. . The geothermal turbines 10a and 10b employ the last stage blade series having the same blade length in a plurality of rear stages including the last stage rotor blades 20a and 20b. The stationary part such as the casing of the geothermal turbine 10b has substantially the same size as the casing of the geothermal turbine 10a shown in FIG.

  Further, couplings 24a and 24b, 25a and 25b, and coupling spans L2a and L2b, which are basic dimensions of the turbine rotors 11a and 11b, are designed to have the same dimensions. Further, the bearings 21a and 21b and 22a and 22b and the bearing spans L1a and L1b before and after the turbine are respectively designed to have the same dimensions.

  Since the nozzle blades and rotor blades of the first stage of the turbine inlet, or a plurality of inlet side stages including the first stage, are designed to meet respective turbine inlet steam conditions, i.e., pressure, temperature and flow rate, In the turbines 10a and 10b, the sizes of the nozzle blades and the moving blades in these stages are different from each other.

  As a specific example, looking at the first stage, in FIG. 3, the outlet height (length) L3a of the first stage nozzle blade 18a of the geothermal turbine 10a having a large turbine inlet steam volume flow rate and the outlet of the rotor blade 19a. The height (length) L4a is designed to be larger than the outlet height (length) L3b of the first stage nozzle blade 18b of the geothermal turbine 10b and the outlet height (length) L4b of the rotor blade 19b in FIG. Is done.

  In the first embodiment, a spare turbine rotor 11c that can be replaced with a plurality of turbine rotors 11a and 11b is prepared. In the preliminary turbine rotor 11c shown in FIG. 5, the blade blade lengths of the plurality of rear stages including the final stage moving blades 20c are the number of rear stage blades including the final stage moving blades 20a and 20b used in the plurality of geothermal turbines 10a and 10b. Same as blade length.

  Further, the couplings 24c and 25c of the spare turbine rotor 11c and the coupling span L2c have the same dimensions as the couplings 24a, 24b and 25a and 25b and the coupling spans L2a and L2b of the turbine rotors 11a and 11b, respectively. Further, the bearings 21c and 22c and the bearing span L1c of the spare turbine rotor have the same dimensions as the bearings 21a and 21b and 22a and 22b and the bearing spans L1a and L1b of the turbine rotors 11a and 11b, respectively.

  On the other hand, the blade size of the first stage or multiple stages of the turbine inlet side of the spare turbine rotor 11c is the same among the plurality of geothermal turbines having different steam conditions, with the largest blade size of these stages on the turbine inlet side. Alternatively, a value close to that is set. The spare turbine rotor 11c can be operated to substantially satisfy the original planned output regardless of which geothermal turbine is inserted.

  As a specific example, consider the case where the moving blade size of the turbine inlet-side stage of the spare turbine rotor 11c is the same as that of the turbine rotor 11a among the plurality of geothermal turbines, that is, the turbine rotor 11a. Try it.

  FIG. 6 shows the maximum turbine output in a geothermal plant system in which geothermal water heated by underground magma is guided to a flasher and the geothermal turbine is driven by saturated steam generated by depressurizing the flasher to generate power. It is an example of the characteristic curve for examining optimization of the flasher pressure for obtaining. In FIG. 6, the flasher pressure and the turbine output are each dimensionlessly displayed as maximum values. The flasher pressure may be re-read as the turbine inlet steam pressure.

  When considering the same amount of hot water, if the flasher pressure is set lower than the optimum value, the enthalpy of the generated saturated steam will be lower, so the amount of energy that can be extracted from the unit steam volume will decrease and the turbine output will decrease. It acts in the direction to do. However, on the other hand, when the enthalpy of the generated saturated steam is low, the flow rate of the saturated steam evaporated from the same hot water energy is increased, and this increase in the amount of steam acts in the direction of increasing the turbine output. For this reason, the decrease in the total turbine output is extremely small. This is a characteristic unique to the geothermal plant. By effectively utilizing this characteristic, a common spare turbine rotor can be prepared for a plurality of geothermal turbines having different turbine inlet steam conditions.

  As in this embodiment, as the moving blade size of the inlet side stage of the preliminary turbine rotor, a preliminary turbine rotor set to a value close to the maximum of these dimensions among a plurality of geothermal turbines having different steam conditions is used. Inserting and using a turbine having a side blade size corresponds to operating the flasher pressure at a value lower than the optimum value in FIG.

  On the other hand, on the other hand, a spare turbine rotor set to a value close to the minimum of these dimensions among a plurality of geothermal turbines having different steam conditions is assumed as the moving blade dimension of the inlet side stage of the spare turbine rotor. Assuming that it is inserted into a turbine having a larger inlet blade size, this corresponds to operating the flasher pressure at a value higher than the optimum value. In this case as well, as shown in FIG. 6, the decrease in turbine output is not large, but preparing a common spare turbine rotor using these characteristics means that when a common spare turbine rotor is inserted into an existing turbine, By increasing the main steam pressure higher than the turbine design conditions of the original turbine rotor, the turbine output will be secured, but the excessive pressure rise will affect the strength design of the equipment of the entire plant, It is not preferable.

  Now, a case where a spare turbine rotor 11c having the same dimensions as the turbine rotor 11a of the geothermal turbine 10a having a large moving blade size in the stage at the turbine inlet side is inserted into the geothermal turbine 10b having a small turbine inlet steam volume flow rate is considered. View.

  As a hypothetical example for ease of discussion, let us assume a case where the nozzle diaphragm at the turbine inlet side stage of the geothermal turbine 10a is also inserted into the geothermal turbine 10b together with the spare turbine rotor 11c. That is, it corresponds to operating the same thing as the geothermal turbine 10a under the steam conditions of the geothermal turbine 10b. In this state, since the geothermal turbine 10b is a turbine having a large steam swallowing capacity, it does not match the original steam conditions. As a result, the turbine inlet steam pressure is operated in a state lower than the original value.

  If it demonstrates with the characteristic curve of FIG. 6, the original geothermal turbine 10b is designed by the turbine inlet steam pressure 1.0, However, By inserting the spare turbine rotor 11c, turbine inlet steam pressure is changed. This corresponds to operation with a value smaller than 1.0. Even if the turbine inlet steam pressure is greatly reduced to 0.8, that is, 20%, the turbine output is reduced by less than 1%. This is a characteristic unique to the geothermal plant described above, and the change in output with respect to the fluctuation of the flasher pressure, that is, the turbine inlet pressure, is extremely small. This change in output is in a range that can be sufficiently covered within the design margin of a normal geothermal plant.

  As a practical example, when only the spare turbine rotor 11c is inserted into the geothermal turbine 10b and the nozzle diaphragm at the turbine inlet side stage is operated using the original one as it is, the dimensions of these nozzle blades are the geothermal turbine 10a. Therefore, the steam intake capacity is reduced from the above case to be closer to the original, and the turbine inlet steam pressure is reduced less. That is, the decrease in the turbine output is further reduced, and it is understood that the geothermal turbine 10b can sufficiently operate at the rated output even after the common spare turbine rotor 11c is inserted.

  According to this embodiment, it becomes possible to provide a common spare turbine rotor for a plurality of geothermal turbines designed under different steam conditions for each geothermal site, thereby improving the operating rate of the geothermal plant, It can contribute to improvement of maintainability.

  In this embodiment, the blade size of the first stage of the spare turbine rotor 11c is larger than that of the original turbine rotor 11b. However, as described above, the blade size of the final stage of the geothermal turbines 10a and 10b is as follows. Since they are common and the dimensions of the casing are almost the same, it is sufficiently possible to apply to the geothermal turbine 10b.

  Next, a second embodiment of the geothermal power generation system according to the present invention will be described with reference to FIGS. Here, the above-described configuration relating to FIGS. 1 to 5 and the first embodiment is common to the second embodiment, and therefore, a duplicate description is omitted.

  FIG. 7 is a cross-sectional view taken along the direction of flow in one stage of one multi-stage axial turbine of the second embodiment, and FIG. 8 is a cross-sectional view of the multi-stage axial turbine different from FIG. 7 of the second embodiment. It is sectional drawing which follows the direction of the flow in one paragraph.

  The second embodiment is characterized by the degree of reaction at the turbine inlet side stage. The turbine reaction rate represents the ratio of the heat drop in the rotor blades to the heat drop in the turbine stage. A positive reaction degree indicates that the heat drop in the rotor blade is positive, that is, the flow in the rotor blade is a speed-up flow. On the contrary, if the reaction degree is negative, the heat drop in the moving blade becomes negative and the flow becomes a decelerating flow, which leads to a reduction in paragraph efficiency. For this reason, in general, in the design of the turbine stage, a positive value is taken as the reaction degree.

  FIGS. 7 and 8 are diagrams for explaining the difference in reaction degree due to the difference between the throat areas S1a and S1b of the nozzle blades 29a and 29b in two paragraphs using the blades 30a and 30b having the same throat areas S2a and S2b. It is. In the nozzle blade 29a having the large throat area S1a, the nozzle blade outlet speed when the same flow rate is applied is slower than that of the nozzle blade 29b having the small throat area S1b. Therefore, the velocity energy at the nozzle blade 29a, that is, the heat drop is small, and the proportion of the heat drop of the moving blade 30a is relatively large in the stage heat drop, and FIG. 7 is a paragraph with a high degree of reaction. If this is viewed as a throat area ratio (= blade blade throat area S2 / nozzle blade throat area S1), FIG. 7 having a small throat area ratio is a paragraph with a high degree of reaction.

  When the spare turbine rotor 11c having the same dimensions as the turbine rotor 11a of the geothermal turbine 10a having a large moving blade size in the turbine inlet side stage is inserted into the turbine casing 12b of the geothermal turbine 10b and used in combination with the original nozzle blades of the geothermal turbine 10b. The nozzle blade dimensions of the geothermal turbine 10b are smaller than those of the geothermal turbine 10a, and as a result, the throat area ratio in these paragraphs is larger than the value of the geothermal turbine 10a. That is, the reaction degree is lowered. In this case, when the reaction degree becomes a negative value, the paragraph efficiency is lowered. However, in the second embodiment, the reaction degree of the turbine inlet side paragraph of the turbine 10a is set to be high in advance. This makes it possible to avoid falling into a negative reaction degree when using the spare turbine rotor and maintain high efficiency.

  The moving blades 30a and 30b shown here are assumed to have the same throat area S2a and S2b, that is, the same blade having the same blade length, but when viewed in terms of nozzles, the nozzle blade 29a of FIG. The throat area S1a is set larger than the throat area S1b of the nozzle blade 29b of FIG. Therefore, the paragraph 33a composed of the nozzle blades 29a and the moving blades 30a in FIG. 7 has a larger steam swallowing ability than the paragraph 33b shown in FIG. In terms of the throat area ratio, as described above, the paragraph 33a is a paragraph having a smaller value than the paragraph 33b, that is, a high degree of reaction in terms of the degree of reaction.

  In this way, by using a nozzle blade with a large throat area by reducing the throat area ratio and increasing the reaction rate, that is, by suppressing the increase in the blade length of the turbine stage having a large turbine inlet steam volume flow rate, It is possible to design a turbine rotor having moving blades having the same or equivalent dimensions as a turbine having a small inlet steam volume flow rate. That is, these turbine rotors can be interchanged, and it is easy to have a common spare turbine rotor.

  Next, a third embodiment of the geothermal power generation system according to the present invention will be described with reference to FIGS. Here, since the description regarding FIG.1, FIG.2, FIG.5 in description of 1st Embodiment is common also in 3rd Embodiment, duplication description is abbreviate | omitted. FIG. 9 is a partial longitudinal sectional view of one stage when a spare turbine rotor is inserted in one multi-stage axial turbine, and FIG. 10 is one paragraph when a spare turbine rotor is inserted in a multi-stage axial turbine different from FIG. FIG. 11 is a partial longitudinal sectional view of one stage when a spare turbine rotor and a spare nozzle diaphragm are inserted in a multistage axial flow turbine.

  Consider a case where the largest blade size of a plurality of geothermal turbines, that is, a size slightly smaller than the size of the turbine rotor 11a, is adopted as the moving blade size of the turbine inlet side stage of the preliminary turbine rotor 11c. In this case, as shown in FIGS. 9 and 10, when the preliminary turbine rotor 11c is inserted into the geothermal turbine 10a or 10b, there is a step between the nozzle blade heights L3a and L3b and the moving blade height L4c in the turbine inlet side stage. L7a and L7b are generated. If the steps L7a and L7b are excessive, energy loss occurs due to flow disturbance. However, the use of the spare nozzle diaphragm 15c suitable for the spare turbine rotor eliminates the adverse effect on the paragraph efficiency due to the step. Can do.

  For example, as shown in FIG. 9, when the blade height L4c of the rotor blade 19c of the spare turbine rotor is lower than the height L3a of the nozzle blade 18a, it is compatible with the blade as shown in FIG. A preliminary nozzle diaphragm 15c having a nozzle blade height L3c to be used is used. At this time, in order to prevent the steam swallowing ability from decreasing due to the preliminary nozzle blade height L3c being lower than the nozzle blade height L3a of the geothermal turbine 10a, the throat area of the nozzle blade 18c is reduced by increasing the mounting angle. It is better to set it equal to the throat area.

  As a result, the turbine equipped with the spare turbine rotor 11c maintains the same steam swallowing ability as the original turbine 10a. For this reason, the steam state at the turbine inlet when the planned amount of steam flows is equivalent to the original value, and the rated output operation is possible. At this time, the throat area ratio becomes smaller than the original by the amount that the height of the moving blade is lowered and the throat area of the moving blade is reduced.

  Further, as shown in FIG. 10, when the blade height L4c of the spare turbine rotor is too high compared to the nozzle blade height L3b, the nozzle blade height L3c suitable for the blade as shown in FIG. By using the spare nozzle diaphragm 15c having the above, it becomes a turbine having a larger steam swallowing ability than the original. The characteristics of the turbine in this case are as described above, and the rated output operation is possible. In this case, the steam swallowing ability of the turbine can be made equivalent to that of the original turbine 10b by reducing the throat area by reducing the mounting angle of the nozzle blades 18c of the spare nozzle diaphragm 15c. At this time, the throat area ratio becomes larger than the original by an amount corresponding to an increase in the throat area of the moving blade due to an increase in the height of the moving blade.

  The spare nozzle diaphragm 15c is supported and fixed to the turbine casing 12b that forms the original turbine 10b, and is arranged concentrically with the spare turbine rotor 11c, similarly to the original nozzle diaphragm 15b. Here, the size of the nozzle diaphragm outer ring 151b that forms the original nozzle diaphragm 15b is usually sufficiently large, and is replaced with the spare nozzle diaphragm outer ring 151c as shown in FIG. 11 to replace the original nozzle diaphragm outer ring. Even if the outer shape becomes larger than 151b, there is enough space to support and fix the spare nozzle diaphragm 15c to the turbine casing 12b. However, when there is not enough space in the outer space of the spare nozzle diaphragm outer ring 151c, the outer periphery may be shaped according to the turbine casing 12b, and no trouble occurs.

  Geothermal plants can undergo aging changes in their steam characteristics during many years of operation. In particular, when the steam well is depleted and the generated steam flow is reduced, not only the rated output is not obtained, but also the loss due to mismatch between the steam conditions and the turbine size cannot be ignored. The best solution to this is to modify the turbine to meet the changed steam conditions, but this may not be realized from an economic point of view.

  Therefore, as one of the countermeasures, it is possible to cope with the changed steam conditions by modifying the taken out original rotor or nozzle diaphragm. As the simplest method for remodeling the nozzle diaphragm, for example, there is a proposal of partially inserting a plug or lid into a part of the flow path of the nozzle blade. However, this method is not preferable from the viewpoint of reliability because it increases the steam excitation force on the rotor blade.

  Therefore, as an example, by remodeling the height L3c of the nozzle blade at one stage or a plurality of stages on the turbine inlet side to be lower than the original value, it is possible to reduce the steam swallowing ability and cope with the new steam condition. As another example, there is a method of reducing the nozzle throat area by reducing the mounting angle of the nozzle blades in these paragraphs. As a specific form thereof, in the first embodiment (FIGS. 1 to 5) or the third embodiment (FIGS. 9 to 11) of the geothermal turbine, the preliminary turbine rotor 11c is used as the moving blade in the turbine inlet side stage. This is the same as when inserted into a small geothermal turbine.

  Thereby, the geothermal turbine can be efficiently operated by adjusting the nozzle diaphragm in response to the change of the steam condition for the geothermal turbine whose turbine inlet steam condition has changed over time.

  In the embodiment described above, when the spare turbine rotor 11c is used by replacing the original turbine rotor of one existing geothermal turbine, after repairing / repairing the original turbine rotor taken out from the geothermal turbine, It can also be used as a new spare turbine rotor for geothermal turbines.

  For example, when the height of the turbine inlet stage rotor blade of the new spare turbine rotor is larger than the rotor blade height of the geothermal turbine into which this spare turbine rotor is inserted next, the first embodiment (FIG. 1 to FIG. In the case of 5) and vice versa, the third embodiment (FIGS. 9 to 11) can be applied.

  Next, a fourth embodiment of the geothermal power generation system according to the present invention will be described with reference to FIG. FIG. 12 is a schematic layout diagram showing a geothermal power generation system according to the fourth embodiment.

  In general, in a turbine composed of a plurality of casings, the design dimensions of the turbine rotor incorporated in each casing are different. An example of a geothermal turbine consisting of two casings shown in FIG. 12 will be described. The turbine rotor 37a built in the casing 35a is coupled to the turbine rotor 37b built in the casing 35b via a coupling 38a. The turbine rotor 37b is coupled to the generator 36 via a coupling 38b. The coupling 38a only transmits the output (torque) of the turbine rotor 37a, whereas the coupling 38b transmits the total output (torque) of the turbine rotor 37a and the turbine rotor 37b to the generator 36. The size required for it will inevitably increase. Similarly, regarding the shaft diameter of the turbine rotor and the bearing size, the turbine rotor 37b is required to be larger than the turbine rotor 37a. On the other hand, the thrust bearing may be provided only in one turbine rotor.

  In the fourth embodiment, regarding a geothermal turbine composed of a plurality of turbine rotors, the coupling dimensions at both shaft ends of each turbine rotor are matched with the dimensions of the coupling at the shaft end of the turbine rotor directly connected to the generator. Unify and unify the main dimensions of each turbine rotor, such as coupling span, bearing dimensions, and bearing span, to match the main dimensions of the turbine rotor directly connected to the generator. This makes it possible to provide compatibility between the respective turbine rotors.

  For example, in FIG. 12, the front coupling 38, the intermediate coupling 38a, and the generator coupling 38b of the turbine rotor 37a have the same dimensions, so that they can be coupled to each other even if the turbine rotor 37a and the turbine rotor 37b are replaced. It is. Further, since the dimensions of the coupling 38b directly connected to the generator 36 are unified, there is no problem in power transmission. The same applies to the strength of the turbine rotor. By unifying the main dimensions of the turbine rotor 38b directly connected to the generator 36, all strength problems can be cleared. Thus, the common spare turbine rotor can be applied.

  In this embodiment, the turbine rotor 37a that is not directly connected to the generator 36 is designed to be able to transmit a torque larger than the actual torque, so that the turbine rotor 37a itself has an excessive margin and is uneconomical. It can be said that there is. However, considering the convenience and cost of maintenance of the entire geothermal power generation system, efficient operation can be realized at low cost as a whole.

  Next, a fifth embodiment of the geothermal power generation system according to the present invention will be described with reference to FIGS. 13 and 14. FIG. 13 is a schematic layout diagram showing a geothermal power generation system according to the fifth embodiment, and FIG. 14 is a schematic layout diagram showing a case where the geothermal power generation system according to this embodiment is operated with a reduced output. .

  In general, a geothermal turbine with a small output, for example, a 40 MW class geothermal turbine, is constituted by a single-flow turbine. When the output becomes large, for example, an 80 MW class geothermal turbine, there is a strictness of strength to cover a single flow, and a double flow turbine is usually adopted. For example, FIG. 12 shows a turbine in which two casings are connected, but each casing is constituted by a double-flow turbine that forms a counterflow. Such a double flow structure that forms a counter flow in one casing has the advantage of balancing the thrust force, and is generally employed in large steam turbines.

  In this fifth embodiment, in a geothermal turbine requiring double flow, two single-flow turbines having the same flow direction are connected to each other instead of being combined as a counterflow in one casing as is normally done. It is configured to do. In this configuration, since the thrust force of each turbine rotor is added, it is preferable to set the reaction degree of each turbine stage to be low for the purpose of reducing the thrust force.

  FIG. 13 shows a turbine having a large output among the geothermal turbines of the fifth embodiment. Here, the casing 40a and the casing 40b are arranged so as to have the same flow direction, and the dimensions of the couplings 43, 43a, and 43b at both shaft ends of the turbine rotors 42a and 42b built in the casing 40a and the casing 40b are determined. They are unified according to the dimension of the coupling 43b at the shaft end of the turbine rotor 42b directly connected to the generator 41. Furthermore, by making the main dimensions of each turbine rotor such as the coupling span, the bearing dimensions and the bearing span the same as the main dimensions of the turbine rotor 42b directly connected to the generator 41, compatibility between the turbine rotors is achieved. It is possible to have it.

  That is, since the coupling 43 and the intermediate coupling 43a on the front side of the turbine rotor 42a and the coupling 43b on the generator 41 side have the same dimensions, they can be coupled to each other even if the turbine rotor 42a and the turbine rotor 42b are replaced. In addition, since the coupling dimensions directly connected to the generator 41 are unified, there is no problem in power transmission. The same applies to the strength of the turbine rotor. By unifying the main dimensions of the turbine rotor directly connected to the generator, all strength problems are cleared.

  On the other hand, FIG. 14 shows a turbine with a small output, but the turbine has a single flow configuration, and the main dimensions of this turbine rotor are the same as the turbine rotor 42b directly connected to the generator 41 of the geothermal turbine with a large output. Set to That is, the coupling 431c on the front side of the turbine rotor 42c built in the casing 40c and the coupling 432c coupled to the generator 41c are both directly connected to the generator 41 of the geothermal turbine having a large output. The same dimension as that of the coupling 43b at the shaft end. The main dimensions of the turbine rotor 42c, such as the coupling span, the bearing dimensions, and the bearing span, are also the same as the dimensions of the turbine rotor 42b of the turbine having a large output. By doing in this way, it becomes possible to provide a common spare turbine rotor for all turbine rotors for a plurality of turbines having greatly different outputs.

  In the fifth embodiment, the turbine rotor 42a that is not directly connected to the generator 41 and the turbine rotor 42c that is connected to the small output generator 41c are designed to transmit a torque larger than the actual torque. In itself, it can be said that it is an uneconomical design with excess margin. However, considering the convenience and cost of maintenance of the entire geothermal power generation system, efficient operation can be realized at low cost as a whole.

  Heretofore, various embodiments of the geothermal power generation system according to the present invention have been described. According to these embodiments, the following effects can be obtained.

  Geothermal turbines contain corrosive components, moisture, solid particles, and other impurities in the steam and operate in harsh environments. To maintain turbine reliability and performance, regular maintenance and maintenance However, in the geothermal turbine of the embodiment shown here, by improving the maintainability, it is possible to improve the operation rate and high efficiency operation of the geothermal plant through shortening the overhaul period for periodic inspection. Become.

  In geothermal plants, the quality and quantity of geothermal steam due to long-term operation changes over time, but the geothermal turbine of the embodiment shown here is effective against such changes in turbine inlet steam conditions. Therefore, efficient utilization of geothermal energy resources and improvement of plant performance can be achieved.

  Furthermore, geothermal energy is clean energy that does not emit carbon dioxide gas, and the improvement in the operating rate of the geothermal plant leads to the suppression of the power source that emits carbon dioxide directly from the thermal power plant, etc. Improving plant performance and availability will contribute to global environmental protection.

  In addition, embodiment shown here is only an illustration, Comprising: This invention is not limited to these embodiment.

The upper half longitudinal cross-sectional view of one multistage axial flow turbine of the geothermal power generation system which concerns on the 1st Embodiment of this invention. The upper half longitudinal cross-sectional view of the multistage axial flow turbine different from FIG. 1 of the geothermal power generation system which concerns on the 1st Embodiment of this invention. The partial longitudinal cross-sectional view of the 1st paragraph of the multistage axial flow turbine of FIG. The fragmentary longitudinal cross-section of the 1st paragraph of the multistage axial flow turbine of FIG. The upper half longitudinal cross-sectional view of the backup turbine rotor of the geothermal power generation system which concerns on the 1st Embodiment of this invention. The characteristic curve figure which shows the output characteristic of the multistage axial flow turbine of the geothermal power generation system which concerns on this invention. Sectional drawing which follows the direction of the flow in one paragraph of one multistage axial flow turbine of the geothermal power generation system which concerns on the 2nd Embodiment of this invention. Sectional drawing in alignment with the direction of the flow in one stage of the multistage axial flow turbine different from FIG. 7 of the geothermal power generation system which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the geothermal power generation system which concerns on the 3rd Embodiment of this invention, Comprising: The partial longitudinal cross-sectional view of one paragraph at the time of inserting a preliminary | backup turbine rotor with one multistage axial flow turbine. It is a figure for demonstrating the geothermal power generation system which concerns on the 3rd Embodiment of this invention, Comprising: The partial longitudinal cross-section of one paragraph at the time of inserting a preliminary | backup turbine rotor with the multistage axial flow turbine different from FIG. The fragmentary longitudinal cross-section of one paragraph at the time of inserting a backup turbine rotor and a backup nozzle diaphragm with the multistage axial flow turbine of the geothermal power generation system which concerns on the 3rd Embodiment of this invention. The typical arrangement figure showing the geothermal power generation system concerning a 4th embodiment of the present invention. The typical arrangement figure showing the geothermal power generation system concerning a 5th embodiment of the present invention. The typical layout figure which shows the case where it operates by making an output small in the geothermal power generation system which concerns on the 5th Embodiment of this invention.

Explanation of symbols

10a, 10b ... Geothermal turbines 11a, 11b, 11c ... Turbine rotors 12a, 12b ... Turbine casings 13a, 13b ... Turbine stages 14a, 14b ... Rotor blades 15a, 15b, 15c ... Nozzle diaphragms 16a, 16b ... Nozzle blades 17a, 17b ... Turbine steam chambers 18a, 18b ... first stage nozzle blades 19a, 19b, 19c ... first stage blades 20a, 20b, 20c ... last stage blades 21a, 21b, 21c ... front bearings 22a, 22b, 22c ... rear bearings 24a, 24b, 24c ... front couplings 25a, 25b, 25c ... rear couplings 29a, 29b ... nozzle blades 30a, 30b ... rotor blades 33a, 33b ... paragraphs 35a, 35b ... casing 36 ... generators 37a, 37b ... turbine Rotor 38, 38a, 38b ... Coupling 40a, 4 b, 40c ... casing 41,41C ... generators 42a, 42b, 42c ... turbine rotor 43,43a, 43b, 431c, 432c ... coupling L1a, L1b, L1c ... bearing span (distance between the bearing support portion)
L2a, L2b, L2c ... Coupling span (distance between couplings)
L3a, L3b, L3c ... Nozzle blade height (length)
L4a, L4b, L4c ... Rotor blade height (length)
L7a, L7b ... steps S1a, S1b ... nozzle blade throat area S2a, S2b ... moving blade throat area

Claims (13)

A plurality of multi-stage axial steam turbines each having a separate turbine rotor housed in a separate turbine casing and designed for different steam conditions; and at least one of the multi-stage axial steam turbines A geothermal power generation system comprising: at least one generator coupled; and at least one auxiliary turbine rotor that can be commonly used for the plurality of multi-stage axial steam turbines;
Each of the multi-stage axial flow steam turbines has a turbine casing, a plurality of bearings fixed to the turbine casing, and a turbine rotor rotatably supported by these bearings and accommodated in the turbine casing,
Each of the turbine rotor and the spare turbine rotor in each turbine casing is in contact with a coupling disposed at both ends and connectable to another turbine rotor and a generator, a plurality of moving blades, and the plurality of bearings. A plurality of bearing supports that can be supported by the bearings,
About the turbine rotor built in the turbine casing and the spare turbine rotor, the distance between the bearing support portions, the distance between the couplings, the maximum height of the moving blades, and the dimensions of the coupling are common to each other. ,
The height of the moving blades in the turbine inlet side paragraph of the preliminary turbine rotor is equal to the maximum height of the moving blades in the turbine inlet side paragraph of the plurality of multi-stage axial flow steam turbines;
A geothermal power generation system characterized by   Among the plurality of multi-stage axial steam turbines, the reaction degree in at least one stage on the inlet side in a turbine having a relatively large turbine inlet steam volume flow rate is determined by turbine inlet steam volume among the plurality of multi-stage axial steam turbines. 2. The geothermal power generation system according to claim 1, wherein the flow rate is set to be larger than a reaction degree in a corresponding paragraph on an inlet side in a relatively small turbine.   The geothermal power generation according to claim 1, further comprising at least one auxiliary nozzle diaphragm that can be used in common for at least one paragraph on an inlet side of the plurality of multi-stage axial flow steam turbines. system. The preliminary turbine inlet side blade height of paragraph turbine rotor, the higher than blade height of turbines inlet side paragraphs of the plurality of multistage axial flow steam turbine, the preliminary turbine rotor and preliminary nozzle diaphragm Of the preliminary nozzle diaphragm so that the throat area ratio, which is the ratio of the throat area of the rotor blade to the throat area of the nozzle blade when replaced with the nozzle blade, is larger than the throat area ratio of the rotor blade and nozzle blade before replacement. The geothermal power generation system according to claim 3, wherein a nozzle blade throat area is set. Among the plurality of multi-stage axial flow steam turbines, a throat area ratio, which is a ratio of a throat area of a moving blade to a throat area of a nozzle blade in a turbine inlet side stage of a turbine having a relatively large turbine inlet steam volume flow rate, is a turbine inlet steam. The throat area of the rotor blade and the nozzle blade is set so that the volume flow rate is smaller than the throat area ratio of the rotor blade and the nozzle blade in the turbine inlet side paragraph of the turbine, and The geothermal power generation system according to claim 1, wherein the blade lengths are set to be equal to each other. Geothermal power generation having a plurality of multi-stage axial steam turbines, at least one generator coupled to the multi-stage axial steam turbines, and a standby turbine rotor not coupled to the multi-stage axial steam turbine and the generator A device,
Each of the multi-stage axial flow steam turbines has a turbine casing, a plurality of bearings fixed to the turbine casing, and a turbine rotor rotatably supported by these bearings and accommodated in the turbine casing,
Each of the turbine rotor and the spare turbine rotor in each turbine casing is in contact with a coupling disposed at both ends and connectable to another turbine rotor and a generator, a plurality of moving blades, and the plurality of bearings. A plurality of bearing supports that can be supported by the bearings,
For the turbine rotor and the spare turbine rotor in each turbine casing, the distance between the bearing support portions, the distance between the couplings, the maximum height of the moving blades, and the dimensions of the coupling are common to each other, A geothermal power generation apparatus configured to be operable by replacing one of the turbine rotors in each turbine casing with the spare turbine rotor. The height of the moving blades in the turbine inlet side paragraph of the preliminary turbine rotor is equal to the maximum height of the moving blades in the turbine inlet side paragraph of the plurality of multi-stage axial flow steam turbines;
The geothermal power generator according to claim 6 characterized by things. Among the plurality of multi-stage axial steam turbines, the reaction degree in at least one stage on the inlet side in a turbine having a relatively large turbine inlet steam volume flow rate is determined by turbine inlet steam volume among the plurality of multi-stage axial steam turbines. The geothermal power generation apparatus according to claim 7, wherein the flow rate is set to be larger than the degree of reaction in a corresponding paragraph on the inlet side in a relatively small turbine.   The geothermal power generation according to claim 7 or 8, further comprising at least one auxiliary nozzle diaphragm that can be used in common for at least one paragraph on an inlet side of the plurality of multi-stage axial steam turbines. apparatus. A plurality of multi-stage axial flow steam turbines, each having a separate turbine rotor housed in a separate turbine casing and designed for different steam conditions, are operated in common with the plurality of multi-stage axial flow steam turbines. A geothermal power generation method of storing at least one usable spare turbine rotor outside a turbine casing,
About the plurality of multi-stage axial flow steam turbines and the spare turbine rotor, the blade length of the final stage blade, the coupling dimension, the coupling span, the bearing dimension, and the bearing span are equal to each other,
The height of the moving blade of the turbine inlet side paragraph of the preliminary turbine rotor is equal to the maximum height of the moving blade of the turbine inlet side paragraph of the plurality of multi-stage axial steam turbines,
Of the turbine rotors of the plurality of multi-stage axial flow steam turbines, those requiring maintenance, take out from the turbine casing and replace with the spare turbine rotor,
A geothermal power generation method. Storing at least one spare nozzle diaphragm that can be commonly used for at least one paragraph on the inlet side of the plurality of multi-stage axial steam turbines outside the turbine casing;
Replacing a part of the nozzle diaphragm of the multi-stage axial steam turbine with the spare nozzle diaphragm when replacing the turbine rotor of the multi-stage axial steam turbine with the spare turbine rotor;
The geothermal power generation method according to claim 10.   The geothermal power generation method according to claim 10 or 11, wherein after maintaining the turbine rotor taken out of the turbine casing, the turbine rotor is reused as a spare turbine rotor. When the amount of steam supplied is reduced due to secular change of the earth Netsui, for at least one of the nozzle diaphragm, as in the throat area of at least one stage of the nozzle blade of the turbine inlet side is increased, the nozzle blade of the paragraph The geothermal power generation method according to claim 11, wherein the geothermal power generation method is adjusted.

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