JP7783128B2 - Steam generating device and steam generating method - Google Patents

Description

The present invention relates to a steam generating device and a steam generating method.

Patent Document 1 discloses a technology in which hot water is used as a heat source to heat feedwater in a heat exchanger to generate low-pressure steam, and the low-pressure steam is then compressed in a compressor to obtain high-pressure steam. The technology in this document aims to improve energy efficiency by combining a portion of the high-pressure steam separated by a gas-liquid separator and high-temperature water with the hot water that serves as the heat source for the heat exchanger.

JP 2011-64417 A

In factories and other facilities, low-temperature fluids such as steam and hot water after being used for process heating are generally discharged without being used. Even if they are used, low-temperature fluids, particularly those below 100°C, are limited to applications such as hot water supply and heating, and the lower the temperature, the more difficult it is to economically recover the heat. If it were possible to obtain high-temperature fluids above 100°C using low-temperature fluids below 100°C as a heat source, it would be possible to propose an energy-saving measure by reusing waste heat that has not been used until now.

The technology in Patent Document 1 above attempts to recover heat by using a portion of the high-pressure steam separated in the gas-liquid separator and high-temperature water as the heat source for the heat exchanger, but because a heat exchanger is used for heat recovery, energy efficiency is limited by the thermal resistance of the heat exchanger.

The object of the present invention is to provide a steam generating device and a steam generating method that can generate high-pressure steam with high efficiency from the waste heat of a low-pressure fluid.

In order to achieve the above object, the present invention provides a compressor that takes in steam and compresses it, a condensate pipe that merges water separated from steam discharged from the compressor with steam taken into the compressor, a pressure reducer that is provided in the condensate pipe and reduces the pressure of water flowing through the condensate pipe, a first gas-liquid separator that separates water from the steam taken into the compressor, a second gas-liquid separator that separates water from the steam discharged from the compressor and supplies the water to the condensate pipe, a water injection pipe that supplies the water separated from the steam in the first gas-liquid separator to the compressor, and a pressure sensor that measures the pressure of the second gas-liquid separator. a pressure sensor, a temperature sensor for measuring the outlet steam temperature of the second gas-liquid separator, a first control valve provided in the water injection pipe, and a computer for controlling the first control valve in accordance with measurement values output from the pressure sensor and the temperature sensor, wherein the computer calculates a saturation temperature of the steam discharged from the compressor based on the measurement value output from the pressure sensor, compares the measurement value output from the temperature sensor with the saturation temperature, and controls the first control valve so that the measurement value output from the temperature sensor becomes the saturation temperature .

According to the present invention, high-pressure steam can be generated highly efficiently from the waste heat of low-pressure fluid.

1 is a schematic diagram of an example of a steam generating device according to an embodiment of the present invention; 1 is a schematic diagram of another example of a steam generating device according to an embodiment of the present invention; 2 is a flowchart showing an example of a control procedure for a pressure reducing valve by a computer provided in the steam generating device shown in FIG. 2 is a flowchart showing an example of a control procedure of a control valve by a computer provided in the steam generating device shown in FIG.

The following describes an embodiment of a steam generating device and steam generating method according to the present invention, using the drawings.

(composition)
1 and 2 are schematic diagrams of a steam generating device according to one embodiment of the present invention.

In the steam generating device and steam generating method of this embodiment, low-temperature water is heated using the waste heat from low-temperature fluids such as steam or hot water after use for process heating in factories, etc., as a heat source, and the low-pressure steam generated as a result is compressed to generate high-pressure steam that is supplied to users.

The steam generating system shown in FIG. 1 includes a low-pressure steam generating system 40A, gas-liquid separators 4 and 5, a low-temperature water circulation pump 10, a low-temperature water supply pump 11, compressors 1 and 2, pressure reducing valves 7 and 8, control valves 12 and 13, a medium-temperature water heat recovery heat exchanger 9, and a computer 50. In this embodiment, the low-pressure steam generating system 40A is configured to include an exhaust heat recovery heat exchanger 6 and a gas-liquid separator 3. The steam generating system shown in FIG. 2 has a configuration in which the low-pressure steam generating system 40A of the steam generating system shown in FIG. 1 is replaced with a low-pressure steam generating system 40B, and is otherwise configured similarly to the steam generating system shown in FIG. 1.

Each element will be explained in turn below.

-Low pressure steam generating devices 40A, 40B-
The low-pressure steam generator 40A (FIG. 1) and the low-pressure steam generator 40B (FIG. 2) each heat water flowing in from the gas-liquid separator 4 via a water supply pipe 20 to generate steam that is compressed by the compressor 1. The water supply pipe 20 is provided with a pressure reducing valve 7.

The low-pressure steam generator 40A illustrated in Figure 1 includes the exhaust heat recovery heat exchanger 6 and the gas-liquid separator 3 as described above.

Low-temperature water is supplied to the exhaust heat recovery heat exchanger 6 from the gas-liquid separator 3 via piping 23 and low-temperature water circulation pump 10. The exhaust heat recovery heat exchanger 6 illustrated in Figure 1 is a plate heat exchanger that uses waste heat (e.g., around 80°C) from low-temperature fluids such as steam or hot water used for process heating in factories, etc., as a heat source to heat the low-temperature water circulating between it and the gas-liquid separator 3. In the exhaust heat recovery heat exchanger 6, part of the heated low-temperature water vaporizes and becomes low-pressure steam at sub-atmospheric pressure. The low-pressure steam, together with the low-temperature water, is guided to the gas-liquid separator 3 via piping 24.

The gas-liquid separator 3 separates low-temperature water from the low-pressure steam introduced from the exhaust heat recovery heat exchanger 6. When the steam generating system is operating, the inside of the gas-liquid separator 3 is evacuated. Therefore, the gas-liquid separator 3 is manufactured to be strong enough to withstand a vacuum state inside. In the gas-liquid separator 3, gas and liquid are separated under vacuum, allowing the low-temperature water to evaporate at sub-atmospheric pressure. The low-pressure steam from which the low-temperature water has been separated in the gas-liquid separator 3 is guided to the compressor 1 through piping 14. A portion of the low-temperature water separated from the low-pressure steam in the gas-liquid separator 3 is sent back to the exhaust heat recovery heat exchanger 6 by the low-temperature water circulation pump 10. In addition, a portion of the low-temperature water inside the gas-liquid separator 3 is sent to the compressors 1 and 2 by the low-temperature water supply pump 11.

Note that while Figure 1 illustrates an example in which the low-pressure steam generator 40A includes a waste heat recovery heat exchanger 6, which is a plate heat exchanger, the low-pressure steam generator is not limited to the configuration illustrated in Figure 1. The configuration illustrated in Figure 2 is an example in which the low-pressure steam generator 40B is configured with a falling film shell-and-tube type waste heat recovery heat exchanger, and as an example, the low-pressure steam generator 40B can also replace the low-pressure steam generator 40A.

The low-pressure steam generator 40B (shell-and-tube type exhaust heat recovery heat exchanger) includes a tube group 42 consisting of multiple heat transfer tubes, and a low-temperature water spray device 41. In the low-pressure steam generator 40B, low-temperature water inside its body (container) is pumped up by a low-temperature water circulation pump 10 and guided to the low-temperature water spray device 41 via piping 23. The low-temperature water is sprayed inside the body by the low-temperature water spray device 41 and flows down the surfaces of the heat transfer tubes of the tube group 42. The inside of the body of the low-pressure steam generator 40B may be configured to be in a vacuum state when the steam generator is operating.

Cryogenic fluid used for process heating in factories and the like flows through the heat transfer tubes of tube group 42, and the low-temperature water flowing down the surface of the heat transfer tubes is heated by the exhaust heat of the low-temperature fluid, causing some of the low-temperature water to evaporate and generate low-pressure steam. The low-pressure steam generated in low-pressure steam generator 40B is guided to compressor 1 through piping 14, as in the example of Figure 1. As mentioned above, part of the low-temperature water that accumulates within the body of low-pressure steam generator 40B is supplied to low-temperature water spray device 41, and part is sent to compressors 1 and 2 by low-temperature water supply pump 11, as in the example of Figure 1.

A water supply pipe 25 is connected to the body of the gas-liquid separator 3 and the low-pressure steam generator 40B. Low-temperature water (e.g., tap water) is supplied to the gas-liquid separator 3 and the low-pressure steam generator 40B via this water supply pipe 25. In the example shown in Figures 1 and 2, the water supply pipe 25 passes through a medium-temperature water heat recovery heat exchanger 9, which uses the medium-temperature water from the gas-liquid separator 4 flowing through the water supply pipe 20 as its heat source. The supply water flowing through the water supply pipe 25 recovers heat from the medium-temperature water in the medium-temperature water heat recovery heat exchanger 9. However, the medium-temperature water heat recovery heat exchanger 9 can be omitted if not required.

The gas-liquid separator 3 and the low-pressure steam generator 40B are also equipped with a water level sensor 30 that measures the level of the low-temperature water stored in the body of the gas-liquid separator 3 and the low-pressure steam generator 40B. There are no limitations on the type of water level sensor 30. The measurement value from this water level sensor 30 is sent to the computer 50.

-Compressor 1-
The compressor 1 shown in Fig. 1 is a screw compressor including a male rotor and a female rotor. The compressor 1 takes in low-pressure steam (e.g., about 50 kPa) generated in a low-pressure steam generator 40A (low-pressure steam generator 40B in Fig. 2), compresses it, and increases the pressure (e.g., to about 200 kPa). In the example of Fig. 1 and Fig. 2, multiple-stage (two-stage in this embodiment) compressors 1 and 2 are used, so the compressor 1 corresponds to a front-stage compressor that compresses the steam taken in by the compressor 2, which serves as a rear-stage compressor.

In addition, low-temperature water separated from low-pressure steam in a gas-liquid separator 3 (low-temperature steam generator 40B in the example of Figure 2) and discharged from a low-temperature water supply pump 11 is supplied to the compressor 1 via a water injection pipe 21. The water injection pipe 21 is equipped with a control valve (flow rate adjustment valve) 12 that controls the amount of low-temperature water supplied to the compressor 1.

The low-temperature water introduced through the water injection pipe 21 is sprayed into the inside of the casing of the compressor 1, sealing the gap between the male and female rotors of the compressor 1 and cooling the steam during the compression process so that the medium-pressure steam obtained by compressing the low-pressure steam in the compressor 1 becomes saturated steam. Meanwhile, the low-temperature water heated by cooling the steam during the compression process becomes medium-temperature water (e.g., approximately 120°C) that is higher in temperature than low-temperature water (e.g., approximately 80°C) and is discharged from the compressor 1, and some of it evaporates during the heating process to become medium-pressure steam. This medium-pressure steam is discharged from the compressor 1 together with the medium-pressure steam obtained by compressing the low-pressure steam from the low-pressure steam generator 40A (or 40B), and is guided to the gas-liquid separator 4 via pipe 15.

-Gas-liquid separator 4-
The gas-liquid separator 4 separates medium-temperature water from the medium-pressure steam discharged from the compressor 1 and sucked into the compressor 2. The medium-pressure steam from which the medium-temperature water has been separated in the gas-liquid separator 4 is guided to the compressor 2 through a pipe 16. The medium-temperature water separated from the medium-pressure steam in the gas-liquid separator 4 passes through a water pipe 20 and is guided to the gas-liquid separator 3 via the medium-temperature water heat recovery heat exchanger 9 and the pressure reducing valve 7. By passing the water pipe 20 through the medium-temperature water heat recovery heat exchanger 9 and the pressure reducing valve 7, the medium-temperature water is supplied to the gas-liquid separator 3 with its temperature and pressure reduced to the same levels as those of the low-temperature water.

The gas-liquid separator 4 is also equipped with a water level sensor 31 that measures the level of the medium-temperature water stored in the body of the gas-liquid separator 4. The gas-liquid separator 4 is also equipped with a pressure sensor 35 that measures the pressure inside the body of the gas-liquid separator 4. Furthermore, the pipe 16 connecting the gas-liquid separator 4 to the compressor 2 is equipped with a temperature sensor 33 that measures the outlet steam temperature of the gas-liquid separator 4. The measured values of the water level sensor 31, pressure sensor 35, and temperature sensor 33 are sent to the computer 50. There are no particular limitations on the type of the water level sensor 31, temperature sensor 33, and pressure sensor 35.

-Compressor 2-
The compressor 2 is a screw compressor including a male rotor and a female rotor, similar to the compressor 1. The compressor 2 takes in medium-pressure steam (e.g., about 200 kPa) introduced from the gas-liquid separator 4 via a pipe 16, compresses it, and increases the pressure (e.g., to about 600 kPa).

In addition, medium-temperature water separated from medium-pressure steam in the gas-liquid separator 4 is supplied to the compressor 2 as low-temperature water via the gas-liquid separator 3, the low-temperature water supply pump 11, and the water injection pipe 22. The water injection pipe 22 is equipped with a control valve (flow rate adjustment valve) 13 that controls the amount of low-temperature water supplied to the compressor 2.

The low-temperature water introduced through the water injection pipe 22 is sprayed into the inside of the casing of compressor 2, sealing the gap between the male and female rotors of compressor 2 and cooling the steam during compression so that the high-pressure steam obtained by compressing the medium-pressure steam in compressor 2 becomes saturated steam. Meanwhile, the medium-temperature water heated by cooling the steam during compression becomes high-temperature water (e.g., 150-160°C) that is warmer than the medium-temperature water and is discharged from compressor 2, and some of it evaporates during the heating process to become high-pressure steam. This high-pressure steam is discharged from compressor 2 together with high-pressure steam obtained by further compressing the medium-pressure steam from compressor 1, and is guided to gas-liquid separator 5 via pipe 17.

-Gas-liquid separator 5-
The gas-liquid separator 5 separates high-temperature water from the high-pressure steam discharged from the compressor 2. The high-pressure steam from which the high-temperature water has been separated in the gas-liquid separator 5 is supplied to users through a pipe 18. The high-temperature water separated from the high-pressure steam in the gas-liquid separator 5 is supplied to a condensate pipe 19 and guided to the gas-liquid separator 4 via a pressure reducing valve 8 provided in the condensate pipe 19, where it joins the steam taken into the compressor 2. The high-temperature water flowing through the condensate pipe 19 is reduced in pressure via the pressure reducing valve 8, and a portion of it flashes and evaporates, reaching a temperature level similar to that of the medium-temperature water (i.e., medium-temperature water), which then joins the medium-temperature water inside the gas-liquid separator 4. Meanwhile, the steam generated by the flash evaporation of the high-temperature water joins the medium-pressure steam inside the gas-liquid separator 4 and is supplied to the compressor 2.

The gas-liquid separator 5 is also equipped with a water level sensor 32 that measures the level of high-temperature water stored within the body of the gas-liquid separator 5. The gas-liquid separator 5 is also equipped with a pressure sensor 36 that measures the pressure within the body of the gas-liquid separator 5. Furthermore, the piping 18 that supplies high-temperature steam from the gas-liquid separator 5 to users is equipped with a temperature sensor 34 that measures the outlet steam temperature of the gas-liquid separator 5. The measured values of the water level sensor 32, pressure sensor 36, and temperature sensor 34 are sent to the computer 50. There are no particular limitations on the type of the water level sensor 32, temperature sensor 34, and pressure sensor 36.

-Computer 50-
The computer 50 is a control device that controls the pressure reducing valves 7, 8, the control valves 12, 13, etc. The computer 50 has a function of controlling the control valve 13 in accordance with the measured values output from the pressure sensor 36 and the temperature sensor 34, for example, and adjusting the amount of water injected into the compressor 2 to make the steam compressed by the compressor 2 saturated steam. Similarly, the computer 50 also has a function of controlling the control valve 12 in accordance with the measured values output from the pressure sensor 35 and the temperature sensor 33, and adjusting the amount of water injected into the compressor 1 to make the steam compressed by the compressor 1 saturated steam.

The computer 50 also has the function of controlling the pressure reducing valve 8 in accordance with the measurement value output from the water level sensor 32, thereby maintaining the water level within the body of the gas-liquid separator 5. Similarly, the computer 50 also has the function of controlling the pressure reducing valve 7 in accordance with the measurement value output from the water level sensor 31, thereby controlling the water level within the body of the gas-liquid separator 4. The computer 50 also has the function of controlling a control valve (not shown) provided in the water supply pipe 25 in accordance with the measurement value output from the water level sensor 30, thereby controlling the water level within the body of the gas-liquid separator 3.

The following explains the control of the amount of water injected into compressors 1 and 2, and the water level control of gas-liquid separators 3, 4, and 5, using Figures 3 and 4, respectively.

(Water injection amount control)
FIG. 3 is a flowchart showing an example of a control procedure for the control valve 13 by the computer 50.

The control procedure for control valve 12 by computer 50 is the same as the control procedure for control valve 13. In the following explanation of the control procedure for control valve 13, the explanation of the control procedure for control valve 12 will be replaced by replacing compressor 2, control valve 13, pressure sensor 36, temperature sensor 34, and high temperature with compressor 1, control valve 12, pressure sensor 35, temperature sensor 33, and medium temperature, respectively.

The control shown in Figure 3 is repeatedly executed by the computer 50 at a predetermined cycle time (e.g., every 1 second) during operation of the steam generating device shown in Figure 1 or Figure 2, for example.

Step S11
First, the computer 50 inputs the current measured values P and T of the pressure and temperature of the high-temperature steam outputted from the pressure sensor 36 and the temperature sensor 34 (step S11).

Step S12
Next, the computer 50 calculates the saturation temperature T1 of the high-temperature steam discharged from the compressor 2 based on the measurement value P (i.e., the actual pressure of the high-temperature steam) output from the pressure sensor 36 (step S12).

Steps S13 to S15
The computer 50 compares the measured value T (i.e., the actual temperature of the high-temperature steam) output from the temperature sensor 34 with the saturation temperature T1 (step S13) and controls the control valve 13 so that the measured value T becomes equal to the saturation temperature T1 (steps S14 and S15). Specifically, if the measured value T is higher than the saturation temperature T1, the computer 50 increases the aperture of the control valve 13 and increases the flow rate of low-temperature water supplied to the compressor 1, thereby lowering the measured value T (step S14). Conversely, if the measured value T is lower than the saturation temperature T1, the computer 50 decreases the aperture of the control valve 13 and decreases the flow rate of low-temperature water supplied to the compressor 1, thereby raising the measured value T (step S15). After executing the processes of steps S14 and S15, the computer 50 returns to step S11.

(Water level control)
4 is a flowchart showing an example of a control procedure for the pressure reducing valve 8 by the computer 50. The computer 50 controls the pressure reducing valve 8 according to the procedure shown in FIG. 4 so that the measurement value L output from the water level sensor 32 (i.e., the actual water level in the gas-liquid separator 5) falls within a set range L1-L2. L1 is the lower limit of the set range, and L2 (>L1) is the upper limit of the set range, which are set in advance and stored in the memory of the computer 50.

The control procedure for pressure reducing valve 7 by computer 50 is the same as the control procedure for pressure reducing valve 8. In the following explanation of the control procedure for pressure reducing valve 8, the terms pressure reducing valve 8, gas-liquid separator 5, water level sensor 32, and high temperature will be replaced with the terms pressure reducing valve 7, gas-liquid separator 4, water level sensor 31, and medium temperature, respectively, and this will replace the explanation of the control procedure for pressure reducing valve 7. The control procedure for the control valve (not shown) provided in the water supply pipe 25 is also the same as the control procedure for pressure reducing valve 8. In the following explanation of the control procedure for pressure reducing valve 8, the terms pressure reducing valve 8, gas-liquid separator 5, water level sensor 32, and high temperature will be replaced with the terms control valve (not shown), gas-liquid separator 3 (or low-pressure steam generator 40B), water level sensor 30, and low temperature, respectively, and this will replace the explanation of the control procedure for the control valve (not shown).

The control of Figure 4 is executed in parallel with the control of Figure 3, and like the control of Figure 3, it is repeatedly executed by the computer 50 at a predetermined cycle time (e.g., every 1 second) while the steam generating device of Figure 1 or Figure 2 is in operation.

Step S21
First, the computer 50 inputs the current measured value L of the water level inside the gas-liquid separator 5 output from the water level sensor 32 (step S21).

Steps S22 and S23
Next, the computer 50 compares the measurement value L output from the water level sensor 32 with the lower limit value L1 of the set range (step S22). If the measurement value L is lower than the lower limit value L1, the computer 50 decreases the opening of the pressure reducing valve 8 to reduce the outflow rate of high-temperature water from the gas-liquid separator 5, thereby increasing the measurement value L (step S23). After executing the process of step S23, the computer 50 returns the procedure from step S23 to step S21. If the measurement value L is equal to or greater than the lower limit value L1, the computer 50 moves the procedure from step S22 to step S24.

Steps S24 and S25
When the procedure proceeds to step S24, the computer 50 compares the measurement value L output from the water level sensor 32 with the upper limit value L2 of the set range. If the measurement value L is higher than the upper limit value L2, the computer 50 increases the aperture of the pressure reducing valve 8 to increase the outflow rate of high-temperature water from the gas-liquid separator 5, thereby decreasing the measurement value L (step S25). After executing the process of step S25, the computer 50 returns the procedure from step S25 to step S21. If the measurement value L is equal to or lower than the upper limit value L2, the computer 50 maintains the aperture of the pressure reducing valve 8 and proceeds from step S24 to step S21.

In the flowchart of Figure 4, the procedures of steps S22 and S23 and steps S24 and S25 may be reversed.

(effect)
(1) As described above, high-temperature water separated from the high-pressure steam discharged from the compressor 2 flows into the medium-pressure steam drawn into the compressor 2 via the pressure reducing valve 8. Comparing the inlet and outlet sides of the compressor 2 during operation of the steam generating apparatus, for example, the gas-liquid separators 4 and 5, the internal pressure of the gas-liquid separator 5 is higher than that of the gas-liquid separator 4. In other words, the high-temperature water inside the gas-liquid separator 5 has a higher temperature level than the medium-temperature water inside the gas-liquid separator 4. In this case, when the high-temperature water inside the gas-liquid separator 5 flows into the gas-liquid separator 4 via the pressure reducing valve 8, part of the high-temperature water flashes and evaporates, and the high-temperature water that has passed through the pressure reducing valve 8 drops in temperature, becoming medium-temperature water and joining the medium-temperature water inside the gas-liquid separator 4. Meanwhile, steam generated by the flash evaporation of the high-temperature water joins the medium-pressure steam inside the gas-liquid separator 4 and is supplied to the compressor 2.

At this time, when the high-temperature water is flash evaporated, the ratio of flash steam that joins the medium-pressure steam inside the gas-liquid separator 4 to the high-temperature water (flash steam ratio) is calculated by the following (Equation 1).
F=(h3-h2)/r2×100...(Formula 1)
F: Flash steam rate (wt%)
h3: specific enthalpy of high-temperature water (kJ/kg)
h2: specific enthalpy of medium temperature water (kJ/kg)
r2: latent heat of vaporization of flash steam (kJ/kg)

For example, if the high-temperature water is 150°C, the medium-temperature water is 120°C, and the absolute pressure inside gas-liquid separator 4 is 200 kPa, then h3 = 628 kJ/kg, h2 = 502 kJ/kg, and r2 = 2204 kJ/kg, and the flash steam rate F is 5.7 wt%. In other words, in this case, 5.7 wt% of the flow rate of high-temperature water flowing from gas-liquid separator 5 into gas-liquid separator 4 is recovered as medium-pressure steam.

As such, according to this embodiment, by decompressing the high-temperature water separated from the steam pressurized by the compressor 2 and returning it to the intake side of the compressor 2, the steam generated when the high-temperature water is decompressed can be directly merged with the steam being drawn into the compressor 2. In other words, heat other than the heat of the high-pressure steam supplied to users - in the specific examples of Figures 1 and 2, the heat of the medium-temperature water and high-temperature water - can be recovered within the thermal cycle of the steam generating device, allowing high-pressure steam to be generated efficiently relative to the heat source's heat capacity. Therefore, high-pressure steam can be generated highly efficiently even from the waste heat of low-pressure fluids below 100°C, such as steam or hot water used for process heating in factories, etc.

In addition, evaporation of hot water due to pressure reduction can also occur through the pressure reducing valve 7, just like steam. In other words, steam is generated when the medium-temperature water separated from the medium-pressure steam discharged by the compressor 1 is reduced in pressure through the pressure reducing valve 7, and the generated steam merges with the low-pressure steam being drawn into the compressor 1. This also achieves the same effect as above.

In addition, while this embodiment is configured to generate high-pressure steam from low-pressure steam using multiple compressors 1 and 2, it is also possible to generate high-pressure steam from low-pressure steam using a single high-compression ratio compressor. For example, if compressor 1 has a compression ratio that can boost low-pressure steam to the pressure level of high-pressure steam, compressor 2, gas-liquid separator 5, and associated equipment and piping can be omitted, and the high-pressure steam from which high-temperature water has been separated in gas-liquid separator 4 can be supplied to users. In this case, too, flash evaporation can occur when the high-temperature water flowing from gas-liquid separator 4 via water supply pipe 20 into gas-liquid separator 3 is decompressed by pressure reducing valve 7, and the flash steam can be merged with the low-pressure steam being drawn into compressor 1.

(2) By providing a gas-liquid separator 4 on the suction side of compressor 2, medium-temperature water can be efficiently separated from the medium-pressure steam supplied to compressor 2. At the same time, by providing a gas-liquid separator 5 on the discharge side of compressor 2, high-temperature water can be efficiently generated as medium-pressure steam for heat recovery. The same applies to gas-liquid separators 3 and 4 before and after compressor 1.

However, it is possible to separate water from steam without using the gas-liquid separators 4, 5, and if there is no need to use the gas-liquid separators 4, 5, it is possible to adopt a configuration in which at least one of the gas-liquid separators 4, 5 is omitted or replaced with another element. The same applies to the gas-liquid separators 3, 4 before and after the compressor 1.

(3) By providing water injection pipes 21, 22 that supply water separated from steam in gas-liquid separators 4, 5 to compressors 1, 2 as seal water to seal the gap between the male and female rotors, the compression efficiency of compressors 1, 2 can be improved by utilizing the low-temperature water obtained within the system. In addition, by compressing steam in compressors 1, 2 while cooling it with low-temperature water, it is possible to prevent the compressed steam from becoming superheated. This allows saturated steam to be discharged from compressors 1, 2. Furthermore, by adding low-temperature water to the steam during the compression process in compressors 1, 2, it is possible to discharge steam containing a large amount of moisture from compressors 1, 2. This makes it possible to efficiently obtain high-temperature water that can be vaporized in pressure reducing valves 7, 8 and used for heat recovery.

(4) The amount of low-temperature water supplied to compressors 1 and 2 is controlled so that the temperature of the steam discharged from compressors 1 and 2 measured by temperature sensors 33 and 34 becomes the saturation temperature calculated based on the measurements of pressure sensors 35 and 36. As a result, even if the operating conditions of the steam generating device fluctuate, the amount of low-temperature water supplied to compressors 1 and 2 can be flexibly adjusted to follow the fluctuations in the operating conditions, and the effect of saturating the steam discharged from compressors 1 and 2 can be more rationally achieved.

(5) The water levels in the gas-liquid separators 4 and 5 are controlled within a set range based on the measurements of the water level sensors 31 and 32. This maintains the water levels in the gas-liquid separators 4 and 5, preventing steam from leaking through the separators 4 and 5.

(6) Compressor 1 compresses the steam drawn into compressor 2. By increasing the pressure of low-pressure steam using two stages of compressors 1 and 2, low-pressure steam can be easily compressed to high-pressure steam at a high compression ratio.

Furthermore, if the supply flow rate of high-pressure steam to users is kept constant, the compression rate of low-pressure steam required of the compressor 1 is reduced by the combined flow rate of steam generated by flash evaporation of high-temperature water. Since the shaft power W of the compressor 1 is calculated using the following (Equation 2), the shaft power W can be reduced in proportion to the reduction in the low-pressure steam flow rate D.
W=(hv2-hv1)×D (Formula 2)
W: Shaft power (kW)
hv2: specific enthalpy of discharge steam from compressor 1 (kJ/kg)
hv1: specific enthalpy of intake steam of compressor 1 (kJ/kg)
D: Low pressure steam volume (kg/s)

(7) In the example of Figure 1, the low-pressure steam generator 40A heats low-temperature water supplied from the gas-liquid separator 4 via the water supply pipe 20 and pressure reducing valve 7 to generate low-pressure steam that is compressed by the compressor 1, and is equipped with a gas-liquid separator 3 that separates the low-pressure steam into gas and liquid under vacuum. Because the interior of the gas-liquid separator 3 is maintained in a vacuum state during operation of the steam generator, a sufficient amount of low-pressure steam can be obtained by evaporating low-temperature water at or below atmospheric pressure.

(Modification)
1 and 2, the pressure reducing valves 7 and 8 are controlled to control the water levels in the gas-liquid separators 4 and 5, but the discharge volumes of the gas-liquid separators 4 and 5 can be adjusted by other types of control valves such as flow control valves instead of the pressure reducing valves 7 and 8. Therefore, instead of or in addition to the pressure reducing valves 7 and 8, other types of control valves such as flow control valves can be provided in the water supply pipe 20 and the condensate pipe 19, and a configuration can be adopted in which these control valves are controlled by the computer 50.

In addition, while Figures 1 and 2 illustrate an example in which pressure reducing valves 7 and 8 are used as pressure reducers to reduce the pressure in the water supply pipe 20 and the condensate pipe 19, the pressure reducers are not limited to pressure reducing valves 7 and 8 as long as the desired pressure reducing effect is achieved. For example, other configurations that can achieve a pressure reducing effect, such as flow control valves or return flow paths, can also be used in place of pressure reducing valves 7 and 8.

1...Compressor (compressor, front-stage compressor), 2...Compressor, 3...Gas-liquid separator (first gas-liquid separator), 4...Gas-liquid separator (first gas-liquid separator, second gas-liquid separator), 5...Gas-liquid separator (second gas-liquid separator), 6...Waste heat recovery heat exchanger, 7...Pressure reducing valve (control valve), 8...Pressure reducing valve, 12, 13...Control valve, 19...Condensate piping, 20...Water supply pipe (condensate piping), 21, 22...Water injection piping, 30, 31, 32...Water level sensor, 33, 34...Temperature sensor, 35, 36...Pressure sensor, 40A, 40B...Low-pressure steam generator, 50...Computer, L...Measured value (water level), L1...Lower limit water level (set range), L2...Upper limit water level (set range), P...Measured value (pressure), T...Measured value (temperature), T1...Saturation temperature

Claims (8)

a compressor that sucks in and compresses steam;
a condensate pipe for allowing water separated from the steam discharged from the compressor to merge with the steam drawn into the compressor;
a pressure reducer provided in the condensate pipe to reduce the pressure of water flowing through the condensate pipe;
a first gas-liquid separator for separating water from steam drawn into the compressor;
a second gas-liquid separator that separates water from the steam discharged from the compressor and supplies the water to the condensate pipe;
a water injection pipe that supplies water separated from the steam in the first gas-liquid separator to the compressor;
a pressure sensor that measures the pressure of the second gas-liquid separator;
a temperature sensor that measures an outlet vapor temperature of the second vapor-liquid separator;
a first control valve provided in the water injection pipe;
a computer that controls the first control valve in response to measurement values output from the pressure sensor and the temperature sensor,
The computer
calculating a saturation temperature of the steam discharged from the compressor based on the measurement value output from the pressure sensor;
comparing the measurement value output from the temperature sensor with the saturation temperature;
The steam generating device controls the first control valve so that the measurement value output from the temperature sensor becomes the saturation temperature. 2. The steam generating device of claim 1,
a water level sensor that measures the water level of the second gas-liquid separator;
a second control valve provided in the condensate pipe;
The computer controls the second control valve so that the measurement value output from the water level sensor falls within a set range. The steam generating device of claim 1,
a water level sensor that measures the water level of the first gas-liquid separator;
a water pipe for sending water from the first gas-liquid separator;
a third control valve provided in the water supply pipe;
The computer controls the third control valve so that the measurement value output from the water level sensor falls within a set range. The steam generating device of claim 1,
A steam generating device including a pre-stage compressor that compresses steam drawn into the compressor. The steam generating device of claim 1,
a steam generating device including a front-stage compressor that compresses steam drawn into the compressor and supplies the steam to the first gas-liquid separator; The steam generating device of claim 5,
A steam generating device including a third gas-liquid separator for separating gas and liquid under vacuum . 7. The steam generating device of claim 6,
a water pipe for sending water from the first gas-liquid separator;
a low-pressure steam generator including the third gas-liquid separator and configured to generate steam to be compressed by a front-stage compressor;
a water supply pipe connected to the third gas-liquid separator;
a heat exchanger that heats water supplied to the third gas-liquid separator through the water supply pipe by using heat recovered from the water flowing through the water supply pipe;
A steam generating device comprising: reducing the pressure of water separated from the steam discharged from the compressor to cause flash evaporation;
The vapor produced by the flash evaporation is combined with the vapor drawn into the compressor,
supplying water separated from steam drawn into the compressor to the compressor;
calculating a saturation temperature of the steam discharged from the compressor based on the pressure of the steam discharged from the compressor;
comparing the temperature of the steam discharged from the compressor with the saturation temperature;
A steam generating method comprising controlling the amount of water separated from the steam drawn into the compressor and supplied to the compressor so that the temperature of the steam discharged from the compressor becomes the saturation temperature.