Patent Application
20250146717
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2023-188454 filed on Nov. 2, 2023; the entire contents of which are incorporated herein by reference.
The present disclosure relates to a gas compression device.
In general, low-pressure steam generated by an exhaust heat recovery unit using low-temperature exhaust heat of 100° C. or less as a driving heat source may be heated and pressurized to a high temperature exceeding 100° C. by a compressor. When heat is dissipated due to a temperature difference between the low-pressure steam (about 70° C.) and outside-air temperature (e.g., 20° C.), the low-pressure steam is partially condensed to become a drain in a pipe connecting the exhaust heat recovery unit and the compressor as described above. The drain unexpectedly flowing into the compressor inhibits stable supply of high-pressure steam using the compressor.
Heat pump systems have been conventionally known in which a superheater is provided above an exhaust heat recovery unit that feeds low-pressure steam to a compressor so that high-pressure steam boosted by the compressor partially flows into the superheater (e.g., see PTL 1: JP 2009-103423 A).
This system causes the superheater to form superheated steam from saturated low-pressure steam generated in the exhaust heat recovery unit. This kind of system allows the superheated steam to flow in the pipe connecting the exhaust heat recovery unit and the compressor, so that a drain can be prevented from occurring in the pipe.
Unfortunately, the conventional system described in PTL 1 uses partially high-pressure steam boosted by the compressor as a heat source for generating superheated steam from saturated low-pressure steam. Thus, this system causes reduction in a feed rate of the high-pressure steam boosted by the compressor to a use side.
It is an object to provide a gas compression device capable of preventing condensation of gas in a pipe connecting an exhaust heat recovery unit and a compressor without reducing a feed rate of high-pressure gas boosted by the compressor to a use side.
A gas compression device includes: a gas-liquid separator that evaporates liquid to generate gas and separates the gas from the liquid; a heat recovery unit that supplies the liquid heated by a heat medium to the gas-liquid separator; a compressor that compresses the gas supplied from the gas-liquid separator; and a superheater that heats the gas by heat exchange between the heat medium supplied to the heat recovery unit and the gas supplied from the gas-liquid separator to the compressor, in which the heat medium flows through the superheater and the heat recovery unit in this order.
The gas compression device enables preventing condensation of gas in the pipe connecting the exhaust heat recovery unit and the compressor without reducing a feed rate of high-pressure gas boosted by the compressor to a use side.
Hereinafter, modes (embodiments) for implementing the gas compression device of the present invention will be described in detail with reference to the drawings as appropriate.
The present invention will be here described by taking a steam compression device as an example in which boosts pressure of low-pressure water vapor (referred to below as low-pressure steam) is boosted to high-pressure water vapor (referred to below as high-pressure steam) by a compressor to be fed to a use side.
The steam compression device is configured by assuming that low-temperature exhaust heat is recovered from hot water discharged from a steam-use facility such as a factory and the recovered heat is used again during generation of high-pressure steam to be fed to the steam-use facility. However, the use side of the high-pressure steam generated from the low-pressure steam is not limited to the steam-use facility such as a factory. Additionally, a supply source of exhaust heat is not limited to the steam-use facility such as a factory.
As described later, a gas compression device is not limited to water vapor as an object to be compressed, and is also applicable to compression of other gas capable of gas-liquid conversion, such as Freon and hydrocarbon gas having a low carbon number.
As illustrated in
The second gas-liquid separator 3 here corresponds to a “gas-liquid separator”. The exhaust heat recovery heat exchanger 4 corresponds to a “heat recovery unit”.
The first gas-liquid separator 2 constitutes a feedwater system for the second gas-liquid separator 3 (gas-liquid separator) together with a feedwater heat exchanger denoted by the reference numeral 6 and a pressure reducing valve denoted by the reference numeral 10 in
The compressor 1 raises temperature and pressure of low-pressure steam supplied from the superheater 5 to be described later. The compressor 1 discharges and supplies high-pressure steam to the use side through the first gas-liquid separator 2.
Although not illustrated, the compressor 1 in the present embodiment is assumed to be a screw compressor including a male rotor and a female rotor. Between the male rotor and the female rotor, water is supplied.
As a result, the compressor 1 efficiently compresses the low-pressure steam due to enhanced sealability between the male rotor and the female rotor. In the present embodiment, water in the second gas-liquid separator 3 described later is used as the water to be supplied between the male rotor and the female rotor.
The water is supplied through a pipe 18, and has a flow rate adjusted by a supply pump 8 and a flow regulating valve 9. As described later, the water cools superheated low-pressure steam supplied from the superheater 5 when the low-pressure steam becomes high-pressure steam in the compressor 1, thereby forming saturated high-pressure steam.
The compressor 1 discharges high-temperature water together with the saturated high-pressure steam toward a pipe 15.
The second gas-liquid separator 3 (gas-liquid separator) evaporates water to generate gas (water vapor) and separates the gas and liquid. The water here corresponds to “liquid”. The water vapor corresponds to “gas”.
The second gas-liquid separator 3 (gas-liquid separator) has internal pressure maintained in a state close to vacuum by suction during operation of the compressor 1.
The second gas-liquid separator 3 stores a predetermined amount of low-temperature water. The low-temperature water partially circulates between the second gas-liquid separator 3 and the exhaust heat recovery heat exchanger 4 (heat recovery unit) to be described later through a pipe 19 and a pipe 20. Specifically, a predetermined amount of the low-temperature water is circulated by a low-temperature water circulation pump 7 provided in the pipe 19. As a result, the low-temperature water fed from the second gas-liquid separator 3 is heated by the exhaust heat recovery heat exchanger 4 (heat recovery unit) as described later and then returned to the second gas-liquid separator 3.
In the present embodiment, temperature of the returned low-temperature water is assumed to be about 70° C., but the temperature is not limited thereto. The temperature of the low-temperature water can be appropriately set in accordance with temperature of saturated water vapor to be fed to the superheater 5, the temperature of the saturated water vapor being determined in advance at the time of design.
The second gas-liquid separator 3 (gas-liquid separator) evaporates the returned low-temperature water under substantially vacuum. The second gas-liquid separator 3 (gas-liquid separator) generates low-pressure steam in a saturated state at a low temperature (about 70° C. in the present embodiment). The second gas-liquid separator 3 (gas-liquid separator) separates low-temperature water having not evaporated in the returned low-temperature water again as stored water. The generated saturated low-pressure steam is fed to the superheater 5 described later.
The amount of water corresponding to the low-temperature water evaporated and consumed by the second gas-liquid separator 3 (gas-liquid separator) and the water fed to the compressor 1 through the pipe 18 is supplemented by feedwater using a feedwater heat exchanger 6 described later and return water from the first gas-liquid separator 2.
The exhaust heat recovery heat exchanger 4 (heat recovery unit) heats low-temperature water (liquid) by heat exchange between hot water supplied from the superheater 5 to be described later and the low-temperature water (liquid) supplied from the second gas-liquid separator 3 (gas-liquid separator) through the pipe 19. The heated low-temperature water is partially vaporized into low-pressure steam under atmospheric pressure or less, and the vaporized low-pressure steam is fed to the second gas-liquid separator 3 together with the low-temperature water. The hot water supplied from the superheater 5 here corresponds to a “heat medium”.
Outlet temperature of the low-temperature water (liquid) close to the pipe 20 in the exhaust heat recovery heat exchanger 4 (heat recovery unit) configured as described above is lower than outlet temperature of hot water (heat medium) in the exhaust heat recovery heat exchanger 4 (heat recovery unit) due to thermal resistance of the exhaust heat recovery heat exchanger 4.
As illustrated in
As described above, the hot water (heat medium) here is assumed to be hot water at 100° C. or lower discharged from a steam use facility such as a factory. Specifically, hot water at a temperature of about 80° C. is assumed, but the temperature is not limited thereto.
The hot water (heat medium) is supplied to the superheater 5 through a pipe 12. The saturated low-pressure steam (gas) from the second gas-liquid separator 3 (gas-liquid separator) is supplied to the superheater 5 through a pipe 22. The hot water (heat medium) after heat exchange with the low-pressure steam (gas) in the superheater 5 is supplied to the exhaust heat recovery heat exchanger 4 (heat recovery unit) through a pipe 14.
The low-pressure steam (gas) superheated after the heat exchange with the hot water (heat medium) in the superheater 5 is supplied to the compressor 1 through a pipe 13 as described above.
The superheater 5 in the present embodiment is disposed above the second gas-liquid separator 3 (gas-liquid separator) in a vertical direction.
The pipe 22 through which the low-pressure steam (gas) flows from the second gas-liquid separator 3 (gas-liquid separator) to the superheater 5 is shorter than the pipe 13 through which the low-pressure steam (gas) flows from the superheater 5 to the compressor 1.
The superheater 5 configured as describe above is desirably disposed adjacent to the second gas-liquid separator 3 (gas-liquid separator).
Next, a feedwater system for the second gas-liquid separator 3 (gas-liquid separator) illustrated in
As illustrated in
The first gas-liquid separator 2 separates high-pressure steam in a saturated state and high-temperature water supplied from the compressor 1 through the pipe 15. The separated high-pressure steam in a saturated state is supplied to the use side through a pipe 16 as described above. The first gas-liquid separator 2 supplies the separated high-temperature water to the feedwater heat exchanger 6 through a pipe 17.
Besides this, water is supplied to the feedwater heat exchanger 6. This feedwater to the feedwater heat exchanger 6 cools the high-temperature water from the first gas-liquid separator 2. After that, the cooled high-temperature water is supplied to the second gas-liquid separator 3 (gas-liquid separator) through the pressure reducing valve 10. The water supplied to the feedwater heat exchanger 6 is raised in temperature to be substantially equal to that of the low-temperature water in the second gas-liquid separator 3 (gas-liquid separator) by heat exchange with the high-temperature water, and is supplied to the second gas-liquid separator 3 (gas-liquid separator).
Next, operation effect achieved by the steam compression device A1 (see
The steam compression device A1 includes the second gas-liquid separator 3 (gas-liquid separator) that evaporates water (liquid) to generate water vapor (gas) and separates the water vapor (gas) and the water (liquid), the exhaust heat recovery heat exchanger 4 (heat recovery unit) that supplies water (liquid) heated with hot water (heat medium) to the second gas-liquid separator 3 (gas-liquid separator), the compressor 1 that compresses the water vapor (gas) supplied from the second gas-liquid separator 3 (gas-liquid separator), and the superheater 5 that heats the water vapor (gas) by heat exchange between the hot water (heat medium) supplied to the exhaust heat recovery heat exchanger 4 (heat recovery unit) and the water vapor (gas) supplied from the second gas-liquid separator 3 (gas-liquid separator) to the compressor 1, in which the hot water (heat medium) flows through the superheater 5 and the exhaust heat recovery heat exchanger 4 (heat recovery unit) in this order.
The steam compression device A1 configured as described above causes hot water serving as a heat source to flow through the superheater 5 and the exhaust heat recovery heat exchanger 4 in this order, so that the low-pressure steam in a saturated state separated by the second gas-liquid separator 3 is heated by the hot water in the superheater 5. As a result, low-pressure steam in a dry superheated state is fed to the compressor 1.
Unlike the conventional system (e.g., see PTL 1), the steam compression device A1 enables preventing condensation of water vapor in the pipe 13 connecting the exhaust heat recovery heat exchanger 4 and the compressor 1 without reducing a feed rate of high-pressure steam boosted by the compressor 1 to the use side. The steam compression device A1 can supply the entire amount of high-pressure steam boosted by the compressor 1 to the use side.
The steam compression device A1 configured as described above includes the exhaust heat recovery heat exchanger 4 (heat recovery unit) constituting a heat exchanger that heats water (liquid) by heat exchange between hot water (heat medium) supplied from the superheater 5 and the water (liquid) supplied from the second gas-liquid separator 3 (gas-liquid separator).
The steam compression device A1 configured as described above causes the hot water serving as a heat source to first flow into the superheater 5 and then flow into the exhaust heat recovery heat exchanger 4. Thus, the hot water flowing into the exhaust heat recovery heat exchanger 4 decreases in temperature by the amount of heat exchange in the superheater 5. Low-temperature water heated by the hot water in the exhaust heat recovery heat exchanger 4 decreases in temperature by the thermal resistance of the exhaust heat recovery heat exchanger 4.
Specifically, when hot water at a temperature of 80° C. flows into the superheater 5, the hot water at a temperature of 79° C. reduced by heat exchange in the superheater 5 flows into the exhaust heat recovery heat exchanger 4, for example. Assuming that the hot water exchanges heat with the low-temperature water in the exhaust heat recovery heat exchanger 4 and flows out at a temperature of 72° C., the low-temperature water in a saturated state can be evaporated at a temperature of about 70° C. lower than the temperature of 72° C. of the hot water at an outlet of the exhaust heat recovery heat exchanger 4 due to the thermal resistance of the heat exchanger.
As a result, a heat gradient during heat exchange between hot water and low-pressure steam in the superheater 5 can be set large, and thus the superheater 5 can be made more compact.
The steam compression device A1 as described above is configured to have a heat transfer area of heat exchange in the superheater 5 that is smaller than a heat transfer area of heat exchange in the exhaust heat recovery heat exchanger 4 (heat recovery unit).
Here, a comparison between the amounts of heat exchange of the exhaust heat recovery heat exchanger 4 and the superheater 5 will be first described. For example, the amount Q1 of heat exchange required to convert low-temperature water (hw=293 KJ/kg) at 70° C. at a flow rate of 0.1 kg/s into saturated steam (hs=2627 KJ/kg) at 70° C. can be calculated by (Expression 1) and is about 233 kW.
In contrast, the amount Q2 of heat exchange is required to convert saturated steam at 70° C. with a flow rate of 0.1 kg/s under the same pressure into superheated steam at 80° C. (hv=2646 KJ/kg), and is about 2 kW that can be calculated by (Expression 2).
Thus, the heat transfer area required for the superheater 5 can be relatively reduced as compared with the exhaust heat recovery heat exchanger 4.
The steam compression device A1 as described above enables achieving compactness of the superheater 5. This compactness causes a more advantageous effect in a configuration in which the superheater 5 is disposed adjacent to the second gas-liquid separator 3 (gas-liquid separator).
The steam compression device A1 as described above (see
The superheater 5 requires a sensible heat quantity for a temperature difference necessary for overheating saturated low-pressure steam at a predetermined temperature. Additionally, assumption that a drain flows into the superheater 5 along with the low-pressure steam requires the drain having flowed to be evaporated to be in a superheated state. This case requires sensible heat for bringing steam of the drain into the superheated state in addition to latent heat during evaporation of the drain to supply the low-pressure steam in the superheated state to the compressor 1. Thus, the superheater 5 of the steam compression device A1 increases in size. When the drain cannot be completely evaporated in the superheater 5, the drain may flow into the compressor 1.
For this problem, the steam compression device A1 includes the superheater 5 positioned above the second gas-liquid separator 3 in the vertical direction, so that drain generated in the pipe 22 is less likely to flows into the compressor 1.
The steam compression device A1 as described above (see
The steam compression device A1 allows a drain to return to the second gas-liquid separator 3 through the short pipe 22 by its own weight even when the drain occurs in the pipe 22. Thus, the drain is more reliably prevented from flowing into the superheater 5.
The steam compression device A1 as described above (see
The steam compression device A1 allows the pipe 22 to be eliminated or to be further reduced in length, and thus more reliably prevents generation of a drain between the second gas-liquid separator 3 and the superheater 5.
Next, a steam compression device according to a second embodiment will be described.
As illustrated in
That is, the pipe 30 forms a bypass flow path for hot water (heat medium) connecting an upstream side of the superheater 5 and a downstream side of the superheater 5 with respect to a flow path for hot water (heat medium) formed by the pipe 12, the superheater 5, and the pipe 14.
The pipe 12 is provided with a hot water flow regulating valve 31 at a position between a connection part between the pipe 30 and the pipe 12, and an inlet of hot water (heat medium) of the superheater 5.
As illustrated in
As illustrated in
As illustrated in
The controller 34 according to the present embodiment adjusts an opening degree of the hot water flow regulating valve 31 based on the respective temperature detection signals output from the temperature sensor 32 and the temperature sensor 33.
The controller 34 can be configured to include a read only memory (ROM) that stores a control program for the opening degree of the hot water flow regulating valve 31 and the like, a random access memory (RAM) that reads and develops the control program stored in the ROM, and a central processing unit (CPU) that executes the developed control program and outputs a drive command to a valve body driving unit (not illustrated) of the hot water flow regulating valve 31.
As illustrated in
The degree of superheat ΔT′ as described above is determined in advance as a target value of a necessary and sufficient degree of superheat at which no drain occurs in the pipe 13.
Next, the controller 34 measures a temperature difference ΔT (T2−T1) based on temperature detection signals from the temperature sensors 32 and 33 (step S101) as illustrated in
Subsequently, the controller 34 determines whether a relationship, “Δ>Δ′”, is satisfied (step S102) as illustrated in
When the hot water flow regulating valve 31 (see
When the controller 34 determines that the relationship, “ΔT>ΔT′”, is not satisfied in step S102 (No in step S102), the controller 34 determines whether a relationship, “ΔT<ΔT′”, is satisfied (step S104). When the relationship, “ΔT<ΔT′”, is satisfied (Yes in step S104), the controller 34 outputs a drive command to the hot water flow regulating valve 31 (see
When the hot water flow regulating valve 31 (see
When the controller 34 determines that the relationship, “ΔT<ΔT′”, is not satisfied in step S104 (No in step S104), the processing returns to step S101 again.
Then, returning to step S101 again after each of step S103, step S104, and step S105 allows a series of steps including step S101, step S102, and step S103 and a series of steps including step S101, step S102, step S104, and step S105 to be repeated. As a result, the controller 34 controls operation of the steam compression device A2 so that the temperature difference ΔT (T2−T1) reaches the target degree of superheat ΔT′.
The steam compression device A2 is operated to feed the amount of hot water, which is necessary and sufficient to prevent a drain from occurring in the pipe 13, to the superheater 5.
Next, operation effect achieved by the steam compression device A2 (see
The steam compression device A2 of the present embodiment includes the pipe 12 (first pipe) for supplying hot water (heat medium) to the superheater 5, the pipe 14 (second pipe) for supplying the hot water (heat medium) from the superheater 5 to the exhaust heat recovery heat exchanger 4 (heat recovery unit), and the pipe 30 (third pipe) that connects the pipe 12 (first pipe) and the pipe 14 (second pipe).
The steam compression device A2 enables only hot water at a flow rate necessary and sufficient for heating to be supplied to the superheater 5 while supplying remaining hot water to the exhaust heat recovery heat exchanger 4 (heat recovery unit). That is, the steam compression device A2 can function without causing the entire amount of hot water of the exhaust heat to flow to the superheater 5. Thus, the steam compression device A2 enables not only efficiently reusing exhaust heat, but also further downsizing the superheater 5.
The steam compression device A2 as described above also includes: the temperature sensor 32 (first temperature detector) that detects the first temperature T1 of low-pressure steam (gas) at the inlet of the superheater 5, the low-pressure steam being supplied from the second gas-liquid separator 3 (gas-liquid separator) to the compressor 1 through the superheater 5; the temperature sensor 33 (second temperature detector) that detects the second temperature T2 of the low-pressure steam at the outlet of the superheater 5; the hot water flow regulating valve 31 (flow rate regulating valve) that regulates a flow rate of hot water (heat medium) flowing through the superheater 5; and the controller 34 that controls an opening degree of the hot water flow regulating valve 31 (flow rate regulating valve) to cause a difference between the first temperature T1 detected by the temperature sensor 32 (first temperature detector) and the second temperature T2 detected by the temperature sensor 33 (second temperature detector) to be a predetermined temperature difference (degree of superheat ΔT′).
The steam compression device A2 includes the controller 34 that controls the amount of hot water to be fed to the superheater 5 so that the amount is necessary and sufficient to prevent a drain from occurring in the pipe 13, and thus exhaust heat can be more efficiently reused, and compactness of the superheater 5 can be more reliably achieved.
Although the first embodiment and the second embodiment have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.
The first embodiment and the second embodiment have been described for the steam compression devices A1 and A2 of an open-system in which high-pressure steam obtained by raising temperature and pressure of low-pressure steam in the compressor 1 is supplied to the use side (outside the system) and water is supplied from the outside (outside the system) for consumed water.
However, the gas compression device is not limited to an open system, and can also be applied to a sealed system such as a heat pump system in which high-pressure steam obtained by raising temperature and pressure of low-pressure steam by the compressor 1 is used in the device (in the system). That is, this sealed system is configured such that the second gas-liquid separator 3 generates low-pressure steam again using water condensed by using heat along with high-pressure steam in the system, and the compressor 1 raises temperature and pressure of the low-pressure steam through the superheater 5 again.
Besides water vapor, gas that can be converted into gas and liquid can be used as gas to be compressed in the gas compression device. Suitable available examples of the gas to be compressed include gases that can be used as refrigerants, such as fluorocarbon gas, hydrocarbon gas, ammonia gas, and another gas.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-188454 | Nov 2023 | JP | national |
