Waste heat recovery system

Abstract

This system provides a waste heat recovery system that can effectively utilize heat from different fluids, namely surplus steam and combustion gases, which are discarded in boiler equipment. [Solution] A waste heat recovery system comprising at least a boiler equipment 10 that discharges steam and combustion gas, a compressor 30b that generates pressurized air, and an ejector 20 through which the steam and the pressurized air pass, wherein the pressurized air is drawn in as the steam passes through the ejector 20.

Description

Technical Field

[0001] The present invention relates to a waste heat recovery system for recovering unused heat discarded in facilities within a workplace such as a factory.

Background Art

[0002] In recent years, in workplaces such as factories, efforts have been made to utilize unused heat discarded in various facilities for the purpose of reducing the emissions of carbon dioxide, which is a greenhouse gas. As such an effort, for example, an unused heat utilization system (feed water heating system) has been proposed that heats boiler feed water by a heat pump circuit using waste warm water as a heat source and reduces the fuel consumption of the boiler, as shown in Patent Document 1.

[0003] The feed water heating system described in Patent Document 1 has a configuration in which a heat source fluid (waste warm water) is circulated in the order of an evaporator and a waste heat recovery heat exchanger, and feed water (cold water) is circulated in the order of the waste heat recovery heat exchanger, a subcooler, and a condenser. With this configuration, the feed water heating system described in Patent Document 1 has succeeded in significantly increasing the COP (Coefficient of Performance: energy consumption efficiency) compared to a conventional heat pump system without a waste heat recovery heat exchanger and a subcooler.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Unused heat wasted in boiler facilities includes the heat from surplus steam that could not be used within the facility, as well as the heat from combustion gases produced by the burners used to generate the steam. However, it has been difficult to effectively utilize the heat from these two different fluids—surplus steam and combustion gases—wasted in boiler facilities.

[0006] This invention is proposed in consideration of these problems and aims to provide a waste heat recovery system that can effectively utilize heat from different fluids, namely surplus steam and combustion gases, which are discarded in boiler equipment. [Means for solving the problem]

[0007] To achieve the above objective, the present invention has the following features.

[0008] (Feature Configuration 1) The characteristic configuration of the waste heat recovery system according to the present invention is: Boiler equipment that discharges steam and combustion gases, A compressor that generates pressurized air, An ejector through which the steam and the pressurized air pass, A waste heat recovery system comprising at least the following: The pressurized air is drawn in as the vapor passes through the ejector. It's at a single point.

[0009] (Effect 1) This configuration allows for the effective utilization of heat from different fluids: surplus steam and combustion gases that are wasted in the boiler equipment.

[0010] (Feature Composition 2) The waste heat recovery system according to the present invention is as follows: The system includes a heat exchanger for heating the pressurized air, The heating of the pressurized air in the heat exchanger is performed by the combustion gas. In the ejector, when the steam passes through, the pressurized air heated by the heat exchanger is sucked in. This may be the case.

[0011] (Effect 2) With such a configuration, heat from different fluids, namely surplus steam and combustion gas, which are discarded in the boiler equipment, can be utilized more effectively.

[0012] (Characteristic Configuration 3) As the waste heat recovery system according to the present invention, it includes a generator, the compressor and the generator are driven by the steam, the generator is driven by the steam after driving the compressor. This may be the case.

[0013] (Effect 3) With such a configuration, the unused heat discarded in the boiler equipment can be utilized to drive the generator.

[0014] (Characteristic Configuration 4) As the waste heat recovery system according to the present invention, it includes a heat source for heating the combustion gas, the heat source is installed between the boiler equipment and the heat exchanger. This may be the case.

[0015] (Effect 4) With such a configuration, when the temperature of the combustion gas is lower than the desired temperature, it can be heated, so that the waste heat recovery system can operate with a stable output.

Effects of the Invention

[0016] According to the present invention, it is possible to provide a waste heat recovery system that can effectively utilize heat from different fluids, namely surplus steam and combustion gas, which are discarded in the boiler equipment.

Brief Description of the Drawings

[0017] [Figure 1] It is a block diagram showing the configuration of the waste heat recovery system according to the first embodiment. [Figure 2] It is a diagram showing the configuration of the boiler equipment according to the first embodiment. [Figure 3] It is a diagram showing the configuration of the ejector according to the first embodiment. [Figure 4] It is a diagram showing a flowchart of the waste heat recovery system according to the first embodiment and the second embodiment. [Figure 5] It is a block diagram showing a part of the configuration of the waste heat recovery system according to the second embodiment. [Figure 6] It is a block diagram showing the configuration of the generator according to another embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0021] 1.1.1. Boiler Equipment 10

[0022] As shown in Figure 2, the boiler equipment 10 according to the first embodiment mainly consists of a first water pipe 11, a feedwater pump 12, a second water pipe 13, a combustion chamber 14, a burner 15, and a steam-water separator 16. The first water pipe 11 is a flow path through which water from a water source (not shown) and water from the steam-water separator 16 pass. The water supply pump 12 is for pushing water from the water source into one end of the second water pipe 13 in the combustion chamber 14. A check valve 17 is provided upstream of the water supply pump 12 to prevent water from the boiler equipment 10 from flowing back into the water source. The second water pipe 13 has one end connected to the first water pipe 11 downstream of the feedwater pump 12, and the other end connected to the steam separator 16. It serves as a passage through which water from the first water pipe 11, pushed in by the feedwater pump 12, passes, and steam generated by heating by the burner 15 is supplied to the other end.

[0023] The combustion chamber 14 houses the second water pipe 13 and the burner nozzle 15a of the burner 15, and is a space for heating the water passing through the second water pipe 13 with the burner 15 to generate steam. The combustion gas generated in the combustion chamber 14 is discharged from the exhaust port 14a. The burner 15 has its nozzle 15a housed within the combustion chamber 14 and is used to heat the water passing through the second water tube 13.

[0024] The steam-water separator 16 separates steam and water from the high-temperature water-steam mixture generated in the second water tube 13 within the combustion chamber 14. The steam separated by the steam-water separator 16 is discharged from the steam outlet 16a, and the separated water is supplied to the first water tube 11. The method for separating the mixture is not particularly limited. For example, a "baffle type" can be used, which uses baffle plates to reduce the flow velocity of the incoming mixture, or a "cyclone type" can be used, which swirls the incoming mixture to shake off heavier water droplets. Furthermore, the gas-liquid separator 16 has a water level detector that detects the water level inside the gas-liquid separator 16. The configuration of the water level detector is not particularly limited, but in order to obtain stable and highly accurate information, it is preferable to use a contact-type water level detector such as a pressure-type or float-type detector.

[0025] The boiler equipment 10 according to the first embodiment uses a so-called "once-through boiler," but any steam boiler is acceptable. For example, a "fire-tube boiler" has a structure in which water is stored in a drum, and a combustion chamber and numerous fire tubes are provided inside, with combustion exhaust gas passing through them to heat the water and generate steam. Alternatively, a "water-tube boiler" has drums at the top and bottom, connected by numerous water tubes. 1.1.2. Ejector 20 The ejector 20 is designed to draw in and discharge air supplied from the compressor 30b (described later) by utilizing the power of relatively high-pressure surplus steam, without relying on mechanical drives such as pumps. As shown in Figure 3, the ejector 20 mainly consists of an inlet 21, a nozzle 22, an air intake 23, and a mixing section 24. Inlet 21 is where excess steam, which has been discharged from steam outlet 16a and passed through flow path a, passes through. The nozzle 22 reduces the pressure and accelerates the excess steam that has passed through the inlet 21, and has a tapered shape in which the cross-section becomes smaller towards the downstream side. The intake port 23 is where the combustion gas, which is discharged from the exhaust port 14a and has passed through the flow path e, is drawn in by the effect of the nozzle 22. The mixing unit 24 mixes the excess steam that has passed through the nozzle 22 with the combustion gas that has passed through the intake port 23.

[0026] 1.1.3. Gas Turbine 30 The gas turbine 30 comprises a turbine 30a and a compressor 30b. The mixture discharged from the mixing section 24 of the ejector 20 and passing through the flow path b drives the turbine 30a, and the compressor 30b drives through the shaft 30c to pressurize the air introduced into the intake port 23 of the ejector 20. Specifically, the mixture that has passed through flow path b enters the turbine 30a of the gas turbine 30 and drives the turbine 30a by hitting the blades of the turbine 30a. This drives the compressor 30b via shaft 30c, which then takes in air and discharges compressed air. Furthermore, the mixture that flows into the turbine 30a is discharged toward the turbine generator 40, which will be described later.

[0027] 1.1.4. Turbine Generator 40 The turbine generator 40 comprises a turbine 40a and a generator 40b. The turbine 40a is driven by a mixture that has passed through the turbine 30a, and the generator 40b is driven through the shaft 40c. The turbine 40a can be the same as the turbine 30a of the gas turbine 30, and the generator 40b can be a well-known generator. Furthermore, the mixture flowing into the turbine 40a is discharged through the flow path d to a chimney (not shown). To reduce the possibility of air pollution, dust collectors or the like may be installed in the chimney or the like.

[0028] 1.1.5.Heat exchanger 50 The heat exchanger 50 has a passage 50a through which compressed air discharged from the compressor 30b of the gas turbine 30 passes, and a passage 50b through which combustion gas discharged from the exhaust port 14a of the boiler equipment 10 passes, and is configured to exchange heat with each other. Due to this structure, the compressed air discharged from the compressor 30b of the gas turbine 30 is heated by the combustion gas discharged from the exhaust port 14a of the boiler equipment 10, and the heated compressed air is supplied to the intake port 23 of the ejector 20. As a result, the ejector 20 can utilize preheated compressed air, allowing it to use excess steam without lowering its temperature. Furthermore, the combustion gas that has passed through the flow path 50b is discharged through the flow path f toward a chimney (not shown).

[0029] 1.2. Waste Heat Recovery Method Hereinafter, a waste heat recovery method according to the first embodiment of the present invention will be described with reference to Figure 4. As shown in Figure 4, the waste heat recovery method includes a water supply process S1, a heating process S2, a gas-water separation process S3, a compressed air generation process S4, a heat exchange process S5, a mixture generation process S6, a power generation process S7, and an exhaust process S8.

[0030] 1.2.1. Water supply process S1 The water supply process S1 is a process of supplying water to the second water pipe 13 in the boiler equipment 10 using a water supply pump 12. In this process, first, with water being supplied from the water source to the first water pipe 11, the water supply pump 12 is driven. This supplies water into the second water pipe 13, and the water that has passed through the second water pipe 13 is supplied to the gas-liquid separator 16. Then, the water supplied to the gas-liquid separator 16 is supplied to the first water pipe 11. In other words, in the water supply process S1, the water supply pump 12 ensures that a predetermined amount of water is present in the first water pipe 11, the second water pipe 13, and the gas-liquid separator 16 (the water level detector in the gas-liquid separator 16 detects the predetermined water level). In each process of the waste heat recovery method, when the water level detector detects that the water level has dropped to the replenishment level, the water supply pump 12 is activated and water is supplied up to the predetermined level.

[0031] 1.2.2.Heating process S2 The heating process S2 is a process in which the burner 15 is ignited in the combustion chamber 14 and the water in the second water tube 13 is heated. In this process, first, the burner 15 is ignited in the combustion chamber 14. Once the burner 15 is ignited, a predetermined amount of water is present in the second water pipe 13 after the water supply process S1, and this predetermined amount of water is gradually heated. The heated water then turns into steam and is supplied to the gas-water separator 16. Furthermore, the combustion gases in the combustion chamber 14 are discharged from the exhaust port 14a toward the heat exchanger 50.

[0032] 1.2.3. Steam / water separation process S3 The steam-water separation step S3 is a process in which water is separated from the steam generated in the second water tube 13 within the steam-water separator 16. The following explanation assumes that a "baffle type" steam-water separator 16 is used. In this process, first, the steam generated in the second water tube 13 is directed against a baffle plate (not shown). By directing the steam against the baffle plate, the steam flow velocity decreases. As the flow velocity decreases, the steam and water are separated, the steam is discharged from the steam outlet 16a, and the separated water is supplied to the first water tube 11.

[0033] 1.2.4. Compressed air generation process S4 The compressed air generation process S4 is a process that generates compressed air using the steam discharged from the steam outlet 16a after the steam-water separation process S3. The steam discharged from the steam outlet 16a enters the turbine 30a of the gas turbine 30 via flow path a, ejector 20, and flow path b, and drives the turbine 30a by striking the blades of the turbine 30a. When the turbine 30a is driven, the compressor 30b is driven via shaft 30c, and the compressor 30b takes in air and discharges the compressed air towards the heat exchanger 50 via flow path g. Furthermore, the steam that flows into the turbine 30a is discharged towards the turbine generator 40 through the flow path c. Furthermore, after the mixture formation process S6 described later, the fluid entering the turbine 30a of the gas turbine 30 is not just steam, but a mixture of heated compressed air and excess steam.

[0034] 1.2.5.Heat exchange process S5 The heat exchange step S5 is a step in which the heat from the combustion gas generated in the heating step S2 is transferred to the compressed air generated in the compressed air generation step S4. In the heat exchanger 50, compressed air that passes through flow path 50a and is discharged from the compressor 30b of the gas turbine 30 through flow path g is heated by the combustion gas that passes through flow path 50b and is discharged through flow path e, and the heated compressed air is discharged through flow path h toward the intake port 23 of the ejector 20. Furthermore, the combustion gas passing through the flow path 50b is discharged through the flow path f.

[0035] 1.2.6. Mixture generation step S6 The mixture formation step S6 is a step in which the steam generated in the gas-water separation step S3 is mixed with the heated compressed air generated in the heat exchange step S5. In this process, the steam generated in the gas-water separation process S3 is depressurized by the nozzle 22 of the ejector 20. Therefore, the heated compressed air generated in the heat exchange process S5 is drawn in through the intake port 23. The drawn-in heated compressed air is mixed with the excess steam that has passed through the nozzle 22 in the mixing section 24. The mixture of heated compressed air and excess steam is then supplied to the turbine 30a through the flow path b.

[0036] An ejector is generally a device that utilizes the force of a high-pressure fluid to draw in a low-pressure fluid and discharge it at an intermediate pressure, without relying on mechanical drives such as pumps. More specifically, the nozzle of the ejector reduces the pressure of the high-pressure fluid, thereby drawing in the low-pressure fluid. Therefore, if the only purpose of the ejector is to create a mixture of high-pressure and low-pressure fluids, there is no need to actively pressurize the low-pressure fluid. In the waste heat recovery system according to the present invention, compressed air can be easily generated during the process of generating electricity with the generator 40b, and this compressed air is used as a low-pressure fluid drawn into the ejector 20. As shown in Table 1 below, it was confirmed that the output (amount of air) at the outlet of the ejector 20 is improved by using compressed air. Table 1 shows experimental data illustrating the change in the amount of air (Nm3 / h) at the outlet of the ejector 20 when the gauge pressure (kPaG) of the fluid drawn into the ejector 20 is changed, with the gauge pressure at the inlet 21 fixed at 200 kPaG.

[0037] [Table 1]

[0038] 1.2.7. Power Generation Process S7 The power generation process S7 is a process in which power is generated using the steam discharged from the turbine 30a through the flow path c, or the mixture, in the compressed air generation process S4 or the mixture generation process S6. The steam or mixture that has passed through the flow path c drives the turbine 40a of the turbine generator 40, and drives the generator 40b through the shaft 40c. Furthermore, the steam or mixture that flows into the turbine 40a is discharged towards the chimney through the flow path d.

[0039] 1.2.8. Exhaust process S8 The exhaust process S8 is a process of discharging the combustion gas that has gone through the heat exchange process S5, and the steam or mixture that has gone through the power generation process S7, into the atmosphere through the chimney. The chimney has a dust collector that effectively separates fine particles contained in the combustion gas, etc., discharged from the heat exchanger 50 through the flow path f, and the combustion gas, etc., that has passed through the dust collector is discharged into the atmosphere from the chimney.

[0040] 1.3. Effects The waste heat recovery system of the first embodiment has the configuration described in detail above, and therefore can provide a waste heat recovery system that can effectively utilize heat from different fluids, namely surplus steam and combustion gas, which are discarded in the boiler equipment 10.

[0041] 2. Second Embodiment 2.1. Overall Structure The overall configuration of the waste heat recovery system according to the second embodiment will be described below with reference to Figure 5. As shown in Figure 5, this waste heat recovery system mainly consists of a boiler 10, an ejector 20, a gas turbine 30, a turbine generator 40, a heat exchanger 50, and a heat source 60. The second embodiment differs from the first embodiment in that a heat source 60 is provided in the flow path e. The other configurations are the same as in the first embodiment, and therefore will not be described further.

[0042] 2.1.1. Heat source 60 The heat source 60 is used when the temperature of the combustion gas falls below a predetermined temperature, making it difficult to drive the generator 40b stably. Typically, a known electric heater is used. By using an electric heater, electricity generated from renewable energy sources such as solar power can be utilized. While an electric heater is preferred for the heat source 60, it is not limited to this, and known burners or the like can also be used. Furthermore, thermometers are installed on the upstream and downstream sides of the heat source 60, and the temperature of the combustion gas is controlled by the temperatures measured by these thermometers.

[0043] 2.2. Waste Heat Recovery Method The waste heat recovery method according to the second embodiment of the present invention will be described below. The waste heat recovery method according to the second embodiment is similar to that of the first embodiment, and includes a water supply step S1, a heating step S2, a gas-water separation step S3, a compressed air generation step S4, a heat exchange step S5, a mixture generation step S6, a power generation step S7, and an exhaust step S8. The second embodiment differs from the first embodiment in that the heat exchange process S5 includes a step of heating the combustion air with a heat source 60. Other than this point, the configuration is the same as the first embodiment, and therefore, no further explanation is provided.

[0044] 2.2.1.Heat exchange process S5 The heat exchange step S5 is a step in which the heat from the combustion gas generated in the heating step S2 is transferred to the compressed air generated in the compressed air generation step S4. In the heat exchanger 50, compressed air that passes through flow path 50a and is discharged from the compressor 30b of the gas turbine 30 through flow path g is heated by the combustion gas that passes through flow path 50b and is discharged through flow path e, and the heated compressed air is discharged through flow path h toward the intake port 23 of the ejector 20. Furthermore, the combustion gas passing through the flow path 50b is discharged through the flow path f.

[0045] In the heat exchange process S5, if the reading on the thermometer upstream of the heat source 60 is lower than a predetermined temperature, the heat source 60 is controlled to heat the combustion gas so that the reading on the thermometer downstream of the heat source 60 reaches the predetermined temperature. This configuration allows the waste heat recovery system to operate with a stable output.

[0046] 2.3. Effects The waste heat recovery system of the second embodiment has the configuration described in detail above, and therefore can provide a waste heat recovery system that can effectively utilize heat from different fluids, namely surplus steam and combustion gas, which are discarded in the boiler equipment 10.

[0047] 3. Other Embodiments In the above embodiment, a configuration was adopted in which a turbine generator 40 is used to generate electricity in the waste heat recovery system. However, it is not limited to a configuration that generates electricity; it is also possible to construct a hot water supply system that generates hot water, a temperature control system that generates hot air, and a sterilization system that performs sterilization by high temperature. This makes it possible to use the combustion system of the present invention in a wide range of applications.

[0048] Furthermore, in the above embodiment, a configuration was adopted in which separate turbines were used for driving the compressor 30b and the generator 40b. However, the system is not limited to this configuration, and as shown in Figure 6, it is also possible to adopt a configuration in which the compressor 30b and the generator 40b are driven by a single turbine 30a. This simplifies the overall structure of the waste heat recovery system. [Explanation of symbols]

[0049] 10: Boiler equipment 11: 1st water pipe 12: Water supply pump 13:Second water pipe 14: Combustion chamber 14a: Exhaust port 15: Burner 15a: Crater 16:Sea water separator 16a: Steam outlet 17: Check valve 20: Ejector 21:Inlet 22: Nozzle 23: Air intake 24: Mixing section 30: Gas Turbine 30a: Turbine 30b: Compressor 30c: Shaft 40: Turbine generator 40a: Turbine 40b: Generator 40c: Shaft 50: Heat exchanger 50a: Flow channel 50b: Flow channel 60: Heat source

Claims

1. Boiler equipment that discharges steam and combustion gases, A compressor that generates pressurized air, An ejector through which the steam and the pressurized air pass, A waste heat recovery system comprising at least the following: The pressurized air is drawn in as the vapor passes through the ejector. A waste heat recovery system characterized by the following features.

2. The system includes a heat exchanger for heating the pressurized air, The heating of the pressurized air in the heat exchanger is performed by the combustion gas. As the steam passes through the ejector, the pressurized air heated in the heat exchanger is drawn in. The waste heat recovery system according to feature 1.

3. Equipped with a generator, The compressor and the generator are driven by the steam. The generator is driven by the steam after the compressor has been driven. The waste heat recovery system according to feature 2.

4. The combustion gas is provided with a heat source for heating the combustion gas, The heat source is installed between the boiler equipment and the heat exchanger. The waste heat recovery system according to feature 3.

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