Combustion system

Abstract

This combustion system 100 is provided with: a vaporizer 2 that heats liquid ammonia with a heating medium; a boiler 3 that is connected to the vaporizer 2 and burns an ammonia-containing fuel coming from the vaporizer 2; an air preheater 4 that is arranged in a flue L4 connected to the boiler 3 and heats air with a discharged gas from the boiler 3; an induced draft fan 8 that is arranged downstream of the air preheater 4 in the flue L4 and guides the discharged gas; and a first heat exchanger 5 that is arranged downstream of the air preheater 4 and upstream of the induced draft fan 8 in the flue L4, wherein the first heat exchanger 5 is connected to the vaporizer 2 in a circulating manner through a circulating flow path L5, heats the heating medium by means of the discharged gas, and supplies the heated heating medium to the vaporizer 2.

Description

Technical Field

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[0001] The present disclosure relates to a combustion system. This application claims the benefit of priority based on Japanese Patent Application No. 2022-108341 filed on July 5, 2022, the content of which is incorporated herein by reference.

Background Art

[0002] Ammonia is known as a fuel that does not emit CO2. For example, Patent Documents 1 to 4 disclose power generation facilities that use ammonia as a fuel. In these documents, ammonia is stored in a liquid state. Liquid ammonia is vaporized before being burned and burned in a gaseous state. In these documents, the exhaust heat after combustion is used to vaporize ammonia.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the combustion system as described above, it is desired to further improve the energy efficiency.

[0005] An object of the present disclosure is to provide a combustion system capable of improving energy efficiency.

Means for Solving the Problems

[0006] A combustion system according to one aspect of the present disclosure includes a vaporizer that heats liquid ammonia with a heat transfer medium, a boiler connected to the vaporizer that burns fuel containing ammonia from the vaporizer, an air preheater located in a flue connected to the boiler that heats air with exhaust gas from the boiler, an induced draft fan located downstream of the air preheater in the flue that guides the exhaust gas, an electrostatic precipitator located downstream of the air preheater and upstream of the induced draft fan in the flue that removes particles from the exhaust gas, and a first heat exchanger located downstream of the air preheater and upstream of the electrostatic precipitator in the flue, the first heat exchanger being circulatingly connected to the vaporizer by a circulation path, the first heat exchanger heating a heat transfer medium with exhaust gas and supplying the heated heat transfer medium to the vaporizer, A second heat exchanger located downstream of the induced draft fan in the flue, the second heat exchanger located downstream of the vaporizer and upstream of the first heat exchanger in the circulation path, the second heat exchanger heats a heat transfer medium with exhaust gas and supplies the heated heat transfer medium to the first heat exchanger, It is equipped with.

[0008] The combustion system may include a flue gas desulfurization unit located downstream of the second heat exchanger in the flue to remove sulfur oxides from the exhaust gas.

[0009] The combustion system may include a bypass flow path in the circulation path that connects a first position downstream of the first heat exchanger and upstream of the vaporizer with a second position downstream of the vaporizer and upstream of the second heat exchanger.

[0010] The combustion system may include a valve provided in a bypass flow path, a first temperature sensor located downstream of a second position and upstream of a second heat exchanger in a circulation flow path for measuring the temperature of a heat transfer medium, and a control device that is communicatively connected to the valve and the first temperature sensor, wherein the control device is configured to open the valve and send at least a portion of the heat transfer medium from the first heat exchanger to the second heat exchanger via the bypass flow path, bypassing the vaporizer, if the temperature measured by the first temperature sensor is lower than a certain first threshold.

[0011] The combustion system may include a heater located downstream of the first heat exchanger and upstream of the vaporizer in the circulation path.

[0012] The combustion system may include a second temperature sensor located downstream of the vaporizer in the circulation path for measuring the temperature of the heat transfer medium, and a control device that is communicatively connected to a heater and the second temperature sensor, wherein the control device is configured to further heat the heat transfer medium heated in the first heat exchanger with the heater if the temperature measured by the second temperature sensor is lower than a certain second threshold.

[0013] Furthermore, in an embodiment comprising a first temperature sensor and a control device, the combustion system may also include a second temperature sensor located downstream of the vaporizer in the circulation path for measuring the temperature of the heat transfer medium, and the control device may be communicatively connected to the heater and the second temperature sensor, and may be configured to further heat the heat transfer medium heated in the first heat exchanger by the heater if the temperature measured by the second temperature sensor is lower than a certain second threshold. [Effects of the Invention]

[0014] According to this disclosure, energy efficiency can be improved. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic diagram showing a combustion system according to an embodiment. [Modes for carrying out the invention]

[0016] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. The specific dimensions, materials, and numerical values ​​shown in these embodiments are merely illustrative for ease of understanding and do not limit this disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to this disclosure are omitted from the illustrations.

[0017] Figure 1 is a schematic diagram showing a combustion system 100 according to an embodiment. Hereinafter, the combustion system 100 may also be simply referred to as the "system". For example, the system 100 includes a tank 1, a vaporizer (EVA) 2, a boiler 3, an air preheater (GAH) 4, a first heat exchanger (HEX) 5, a gas-gas heater (GGH) 6, an electrostatic precipitator (ESP) 7, an induced draft fan (IDF) 8, a second heat exchanger (HEX) 9, a flue gas desulfurization unit (FGD) 10, a booster fan (BUF) 11, a chimney 12, a steam turbine 13, a generator 14, and a control device 90. The gas-gas heater 6 also includes a heat recovery unit 61 and a reheater 62. The components of the system 100 are not limited to these, and the system 100 may further include other components. Furthermore, system 100 does not necessarily have to include at least one of the above-mentioned components.

[0018] Tank 1 stores ammonia. Specifically, Tank 1 stores liquid ammonia. Tank 1 is connected to vaporizer 2 by a flow path L1. The liquid ammonia in Tank 1 is supplied to vaporizer 2. For example, a pump P1 for supplying liquid ammonia is provided in flow path L1. Pump P1 may be connected to a control device 90 via wired or wireless communication, and the control device 90 may control the operation of pump P1.

[0019] The vaporizer 2 heats the liquid ammonia from tank 1 with a heat transfer medium heated by the first heat exchanger 5 and the second heat exchanger 9. In other words, in vaporizer 2, the heat transfer medium is cooled by the liquid ammonia. The heated liquid ammonia vaporizes into gaseous ammonia. The vaporizer 2 is connected to boiler 3 by a flow path L2.

[0020] The boiler 3 includes a combustor 31 that burns fuel containing gaseous ammonia from the vaporizer 2. For example, the combustor 31 may burn a mixed fuel containing ammonia and other fuels such as pulverized coal. Also, for example, the combustor 31 may burn only ammonia. Further, for example, the combustor 31 may burn only other fuels other than ammonia as needed. The boiler 3 heats water by the heat generated by combustion and generates steam. In the combustor 31, exhaust gas is generated by combustion.

[0021] The steam turbine 13 is connected to the boiler 3 by a flow path L3. The steam generated in the boiler 3 is supplied to the steam turbine 13 through the flow path L3. The steam turbine 13 is rotated by the steam from the boiler 3. The generator 14 rotates together with the steam turbine 13 and generates electricity.

[0022] In the present embodiment, an air preheater 4, a first heat exchanger 5, a heat recovery device 61, an electrostatic precipitator 7, an induced draft fan 8, a second heat exchanger 9, a flue gas desulfurization device 10, a booster fan 11, and a reheater 62 are arranged in this order from the boiler 3 in a flue L4 connecting the boiler 3 and the chimney 12. In the flue L4, the exhaust gas generated in the boiler 3 flows from the boiler 3 toward the chimney 12.

[0023] The air preheater 4 is connected to the boiler 3. The air preheater 4 is arranged downstream of the boiler 3 in the flue L4. The air preheater 4 heats air with the exhaust gas from the boiler 3. The heated air is supplied to the boiler 3 through a flow path (not shown) and used for combustion.

[0024] The first heat exchanger 5 is connected to the air preheater 4. The first heat exchanger 5 is arranged downstream of the air preheater 4 in the flue L4. The first heat exchanger 5 is connected to the vaporizer 2 in a circulating manner by a circulation flow path L5. A heat medium (first heat medium) flows in the circulation flow path L5. The first heat exchanger 5 heats the heat medium flowing in the circulation flow path L5 with the exhaust gas flowing in the flue L4. In other words, in the first heat exchanger 5, the exhaust gas is cooled by the heat medium. The first heat medium can be various fluids, for example, water.

[0025] As the amount of ammonia burned in boiler 3 increases, the temperature of the exhaust gas at the outlet of air preheater 4 rises. In this embodiment, the first heat exchanger 5 is located immediately downstream of air preheater 4. Therefore, when ammonia is used as fuel, the first heat exchanger 5 can efficiently heat the heat transfer medium with the higher temperature exhaust gas. In addition, the vaporizer 2, which receives the heat transfer medium from the first heat exchanger 5, can efficiently vaporize the ammonia.

[0026] The heat recovery unit 61 is connected to the first heat exchanger 5. The heat recovery unit 61 is located downstream of the first heat exchanger 5 in the flue L4. The heat recovery unit 61 is circulatingly connected to the reheater 62 by a circulation channel L6. A gas, which serves as a heat transfer medium (second heat transfer medium), flows through the circulation channel L6. The second heat transfer medium may be, for example, air. The heat recovery unit 61 heats the heat transfer medium flowing through the circulation channel L6 with the exhaust gas flowing through the flue L4. In other words, in the heat recovery unit 61, the exhaust gas is cooled by the heat transfer medium. The heat transfer medium heated in the heat recovery unit 61 is sent to the reheater 62 via the circulation channel L6.

[0027] The electrostatic precipitator 7 is connected to the heat recovery unit 61. The electrostatic precipitator 7 is positioned downstream of the heat recovery unit 61 in the flue L4. The electrostatic precipitator 7 removes particles (soot) from the exhaust gas. Specifically, the electrostatic precipitator 7 applies a high voltage between the discharge electrode and the dust collection electrode to generate a corona discharge. Ions are generated by the corona discharge. Particles in the exhaust gas that are charged by these ions are attracted to the dust collection electrode by electrostatic attraction. The particles collected at the dust collection electrode are removed.

[0028] In the electrostatic precipitator 7, an increase in the amount of liquid water in the exhaust gas increases the electrical conductivity and improves the dust collection efficiency. In this embodiment, as described above, the exhaust gas is cooled in the first heat exchanger 5 and the heat recovery unit 61 before it enters the electrostatic precipitator 7. Therefore, some of the water vapor in the exhaust gas condenses into liquid before it enters the electrostatic precipitator 7. As a result, the amount of liquid water in the exhaust gas increases, and the dust collection efficiency in the electrostatic precipitator 7 improves.

[0029] The induced draft fan 8 is connected to the electrostatic precipitator 7. The induced draft fan 8 is positioned downstream of the electrostatic precipitator 7 in the flue L4. The induced draft fan 8 guides the exhaust gas from the boiler 3 to the chimney 12. The induced draft fan 8 maintains negative pressure in the boiler 3. The exhaust gas is pressurized in the induced draft fan 8. The temperature of the exhaust gas also rises in the induced draft fan 8 as it is pressurized.

[0030] When the volume of exhaust gas flowing into the induced draft fan 8 decreases, the energy efficiency of the induced draft fan 8 improves. In this embodiment, as described above, the exhaust gas is cooled in the first heat exchanger 5 and the heat recovery unit 61 before entering the induced draft fan 8. Therefore, the volume of exhaust gas decreases before it enters the induced draft fan 8. In addition, as the volume of exhaust gas decreases, the boiler 3 becomes easier to maintain under negative pressure. Thus, the load on the induced draft fan 8 can be reduced, and energy efficiency can be further improved.

[0031] The second heat exchanger 9 is connected to the induced draft fan 8. The second heat exchanger 9 is located downstream of the induced draft fan 8 in the flue L4. The second heat exchanger 9 is circulatingly connected to the vaporizer 2 and the first heat exchanger 5 by a circulation channel L5. The heat transfer medium flows through the circulation channel L5 in the order of the second heat exchanger 9, the first heat exchanger 5, and the vaporizer 2 (counterclockwise in Figure 1). The second heat exchanger 9 heats the heat transfer medium flowing through the circulation channel L5 with the exhaust gas flowing through the flue L4. In other words, in the second heat exchanger 9, the exhaust gas is cooled by the heat transfer medium.

[0032] The flue gas desulfurization unit 10 is connected to the second heat exchanger 9. The flue gas desulfurization unit 10 is located downstream of the second heat exchanger 9 in the flue L4. The flue gas desulfurization unit 10 removes sulfur oxides (SOx) from the exhaust gas. The flue gas desulfurization unit 10 may be, for example, a wet desulfurization unit. Specifically, the flue gas desulfurization unit 10 may use a liquid containing, for example, lime or magnesium hydroxide as an adsorbent. The flue gas desulfurization unit 10 drops the adsorbent into the exhaust gas. SOx in the exhaust gas is taken up by the adsorbent and removed from the exhaust gas. In other embodiments, the flue gas desulfurization unit 10 may be a dry desulfurization unit.

[0033] In the flue gas desulfurization system 10, if the temperature of the exhaust gas is high, the adsorbent is more likely to evaporate, requiring more adsorbent. In this embodiment, as described above, the exhaust gas pressurized and heated by the induced draft fan 8 is cooled in the second heat exchanger 9 before entering the flue gas desulfurization system 10. Therefore, evaporation of the adsorbent can be reduced in the flue gas desulfurization system 10. Thus, the desulfurization efficiency in the flue gas desulfurization system 10 can be improved.

[0034] The booster fan 11 is connected to the flue gas desulfurization unit 10. The booster fan 11 is located downstream of the flue gas desulfurization unit 10 in the flue L4. The booster fan 11 pressurizes the exhaust gas after it has passed through the flue gas desulfurization unit 10.

[0035] The reheater 62 is connected to the booster fan 11. The reheater 62 is positioned downstream of the booster fan 11 in the flue L4. The reheater 62 heats the exhaust gas flowing through the flue L4 with a heat transfer medium flowing through the circulation channel L6. This vaporizes the liquid water in the exhaust gas heading towards the chimney 12 (preventing white smoke). Therefore, corrosion of the chimney 12 can be prevented.

[0036] The chimney 12 is connected to the reheater 62. The chimney 12 is located downstream of the reheater 62 in the flue L4. The chimney 12 discharges exhaust gas to the outside.

[0037] A pump P2 for circulating the heat transfer medium is provided in the circulation channel L5. The pump P2 is connected to the control device 90 via wired or wireless communication. The control device 90 controls the operation of the pump P2.

[0038] A valve V1 is provided in the circulation channel L5. Valve V1 is located downstream of the vaporizer 2 and upstream of the second position C2, which will be described later. For example, valve V1 is connected to the control device 90 via wired or wireless communication. The control device 90 adjusts the flow rate of the heat transfer medium flowing through the circulation channel L5 by controlling the opening degree of valve V1.

[0039] A bypass channel L7 is connected to the circulation channel L5. The bypass channel L7 is positioned to bypass the vaporizer 2. Specifically, the bypass channel L7 connects a first position C1 downstream of the first heat exchanger 5 and upstream of the vaporizer 2 in the circulation channel L5 to a second position C2 downstream of the vaporizer 2 and upstream of the second heat exchanger 9.

[0040] A valve V2 is provided in the bypass channel L7. For example, valve V2 is connected to the control device 90 via wired or wireless communication. The control device 90 adjusts the flow rate of the heat transfer medium flowing through the bypass channel L7 by controlling the opening degree of valve V2. Specifically, by fully or partially opening valve V2, the control device 90 can send all or part of the heat transfer medium from the first heat exchanger 5 directly to the second heat exchanger 9, bypassing the vaporizer 2.

[0041] System 100 is equipped with a temperature sensor (first temperature sensor) S1 in the circulation channel L5. The temperature sensor S1 is positioned to measure the temperature of the heat transfer medium entering the second heat exchanger 9. For example, in the circulation channel L5, the temperature sensor S1 is positioned downstream of the second position C2 and upstream of the second heat exchanger 9.

[0042] System 100 is equipped with a temperature sensor (second temperature sensor) S2 in the circulation channel L5. The temperature sensor S2 is positioned to measure the temperature of the heat transfer medium cooled in the vaporizer 2. For example, in the circulation channel L5, the temperature sensor S2 is positioned downstream of the vaporizer 2 and upstream of the valve V1.

[0043] System 100 is equipped with a temperature sensor (third temperature sensor) S3 in the flow path L2. The temperature sensor S3 is positioned to measure the temperature of the ammonia heated in the vaporizer 2. For example, the temperature sensor S3 is positioned between the vaporizer 2 and the boiler 3.

[0044] The temperature sensors S1, S2, and S3 can be various types of sensors, such as a TIC (Thermal Imaging Camera). The temperature sensors S1, S2, and S3 are connected to the control device 90 via wired or wireless communication and transmit the measured data to the control device 90.

[0045] System 100 includes a heater (first heater) H1 in the circulation channel L5. Heater H1 is positioned to heat the heat transfer medium from the first heat exchanger 5. For example, in the circulation channel L5, heater H1 is positioned downstream of the first heat exchanger 5 and upstream of the first position C1.

[0046] System 100 includes a heater (second heater) H2 in the circulation channel L5. Heater H2 is positioned to heat the heat transfer medium entering the second heat exchanger 9. For example, in the circulation channel L5, heater H2 is positioned downstream of the second position C2 and upstream of the second heat exchanger 9.

[0047] Heaters H1 and H2 can be various types of heaters, such as heat exchangers. For example, heaters H1 and H2 may heat the first heat transfer medium flowing through the circulation channel L5 with a third heat transfer medium. The third heat transfer medium may be auxiliary steam, such as extracted steam from the boiler 3 or the steam turbine 13. The third heat transfer medium is not limited to this and may be other heat transfer mediums.

[0048] Valves V3 and V4 are provided in the flow paths connected to heaters H1 and H2, respectively. For example, valves V3 and V4 are connected to the control device 90 via wired or wireless communication. The control device 90 adjusts the flow rate of the third heat transfer medium flowing through the flow paths connected to heaters H1 and H2 by controlling the opening degree of valves V3 and V4.

[0049] The control device 90 controls all or part of the system 100. For example, the control device 90 may include one or more computers. For example, the operation of the control device 90 described in this disclosure may be performed by one computer or divided among multiple computers. The control device 90 includes components such as a processor 90a, a storage device 90b, and a connector 90c, which are connected to each other via a bus. For example, the processor 90a includes a CPU (Central Processing Unit), etc. For example, the storage device 90b includes a hard disk, a ROM for storing programs, etc., and RAM as a work area, etc. The control device 90 is connected to the components of the system 100 via the connector 90c so as to be able to communicate by wire or wirelessly. For example, the control device 90 may further include other components such as a display device such as a liquid crystal display or a touch panel, and an input device such as a keyboard, buttons, or a touch panel. For example, the operation of the control device 90 described in this disclosure may be achieved by having the processor 90a execute a program stored in the storage device 90b.

[0050] Next, the operation of the control device 90 will be explained.

[0051] As described above, the control device 90 receives measurement data from the temperature sensor S1. As described above, the temperature sensor S1 measures the temperature of the heat transfer medium entering the second heat exchanger 9. If this temperature is lower than a certain value, the exhaust gas may be excessively cooled by the heat transfer medium in the second heat exchanger 9. In this case, the second heat exchanger 9 may corrode due to the sulfuric acid solution in the exhaust gas (this may also be called low-temperature corrosion).

[0052] In this embodiment, if the temperature measured by the temperature sensor S1 is lower than a certain first threshold, the control device 90 opens the valve V2 and sends at least a portion of the heat transfer medium from the first heat exchanger 5 to the second heat exchanger 9 via the bypass flow path L7, bypassing the vaporizer 2. For example, the first threshold may be pre-stored in the storage device 90b. For example, the first threshold may be the temperature at which corrosion begins to occur in the second heat exchanger 9, or a higher temperature with an additional safety factor.

[0053] With this configuration, the heat transfer medium bypassing vaporizer 2 is not used for vaporizing liquid ammonia. In other words, the heat transfer medium bypassing vaporizer 2 is not cooled by liquid ammonia. Therefore, the temperature of the heat transfer medium entering the second heat exchanger 9 rises. With this configuration, corrosion of the second heat exchanger 9 can be prevented.

[0054] Alternatively or additionally, the control device 90 may heat the heat transfer medium entering the second heat exchanger 9 with the heater H2 if the temperature measured by the temperature sensor S1 is lower than a first threshold. For example, the control device 90 may open valve V4 so that a third heat transfer medium is supplied to the heater H2. With such a configuration, the temperature of the heat transfer medium entering the second heat exchanger 9 rises. Therefore, corrosion of the second heat exchanger 9 can be prevented.

[0055] Next, we will describe other operations of the control device 90.

[0056] As described above, the control device 90 receives measurement data from the temperature sensor S2. As described above, the temperature sensor S2 measures the temperature of the heat transfer medium cooled in the vaporizer 2. If this temperature is lower than a certain value, there is a risk that the liquid ammonia will not be sufficiently vaporized in the vaporizer 2.

[0057] In this embodiment, if the temperature measured by the temperature sensor S2 is lower than a certain second threshold, the control device 90 further heats the heat transfer medium heated in the first heat exchanger 5 using the heater H1. For example, the control device 90 may open valve V3 so that a third heat transfer medium is supplied to the heater H1. For example, the second threshold may be pre-stored in the storage device 90b. For example, the second threshold may be the temperature at which ammonia begins to remain as a liquid, or a higher temperature that takes a safety factor into further consideration. With such a configuration, liquid ammonia can be sufficiently vaporized in the vaporizer 2.

[0058] Next, we will describe some other operations of the control device 90.

[0059] As described above, the control device 90 receives measurement data from the temperature sensor S3. As described above, the temperature sensor S3 measures the temperature of the ammonia heated in the vaporizer 2. If this temperature is lower than a certain value, there is a risk that the liquid ammonia will not be sufficiently vaporized in the vaporizer 2.

[0060] In this embodiment, if the temperature measured by the temperature sensor S3 is lower than a certain third threshold, the control device 90 controls the opening of the valve V1 to increase the flow rate of the heat transfer medium supplied to the vaporizer 2. For example, the third threshold may be pre-stored in the storage device 90b. For example, the third threshold may be the temperature at which ammonia begins to remain as a liquid, or a higher temperature that takes a further safety factor into consideration. With such a configuration, liquid ammonia can be sufficiently vaporized in the vaporizer 2.

[0061] The system 100 described above includes a vaporizer 2 that heats liquid ammonia with a heat transfer medium, a boiler 3 connected to the vaporizer 2 that burns fuel containing ammonia from the vaporizer 2, an air preheater 4 located in a flue L4 connected to the boiler 3 that heats air with exhaust gas from the boiler 3, an induced draft fan 8 located downstream of the air preheater 4 in the flue L4 that guides the exhaust gas, and a first heat exchanger 5 located downstream of the air preheater 4 and upstream of the induced draft fan 8 in the flue L4. The first heat exchanger 5 is circulatingly connected to the vaporizer 2 by a circulation path L5. The first heat exchanger 5 heats the heat transfer medium with the exhaust gas and supplies the heated heat transfer medium to the vaporizer 2. With this configuration, the first heat exchanger 5 is located relatively upstream in the flue L4. Therefore, the first heat exchanger 5 can heat the heat transfer medium with higher temperature exhaust gas. Furthermore, the vaporizer 2 can heat ammonia with a higher temperature heat transfer medium. Therefore, energy efficiency can be improved. Also, according to the above configuration, the first heat exchanger 5 is located upstream of the induced draft fan 8 in the flue L4. Therefore, the exhaust gas is cooled in the first heat exchanger 5 before entering the induced draft fan 8. As a result, the volume of exhaust gas entering the induced draft fan 8 can be reduced, making it easier to maintain negative pressure in the boiler 3. Therefore, the load on the induced draft fan 8 can be reduced, and energy efficiency can be further improved.

[0062] Furthermore, system 100 includes a second heat exchanger 9 located downstream of the induced draft fan 8 in the flue L4. The second heat exchanger 9 is located downstream of the vaporizer 2 and upstream of the first heat exchanger 5 in the circulation path L5. The second heat exchanger 9 heats the heat transfer medium with the exhaust gas and supplies the heated heat transfer medium to the first heat exchanger 5. As described above, in the induced draft fan 8, the temperature of the exhaust gas rises with pressurization. With the above configuration, since the second heat exchanger 9 is located downstream of the induced draft fan 8 in the flue L4, the heat transfer medium can be heated by the exhaust gas heated in the induced draft fan 8. Therefore, energy efficiency can be further improved.

[0063] Furthermore, system 100 includes a flue gas desulfurization unit 10 located downstream of the second heat exchanger 9 in the flue L4, which removes sulfur oxides from the exhaust gas. As described above, in the flue gas desulfurization unit 10, if the temperature of the exhaust gas is high, the adsorbent is more likely to evaporate, requiring more adsorbent. With the above configuration, the exhaust gas pressurized and heated by the induced draft fan 8 is cooled in the second heat exchanger 9 before entering the flue gas desulfurization unit 10. Therefore, evaporation of the adsorbent can be reduced in the flue gas desulfurization unit 10. Thus, the desulfurization efficiency can be improved.

[0064] Furthermore, the system 100 includes a bypass channel L7 in the circulation channel L5 that connects a first position C1 downstream of the first heat exchanger 5 and upstream of the vaporizer 2, and a second position C2 downstream of the vaporizer 2 and upstream of the second heat exchanger 9. As described above, if the temperature of the heat transfer medium entering the second heat exchanger 9 is low, the second heat exchanger 9 may corrode. However, with the above configuration, at least a portion of the heat transfer medium can be sent from the first heat exchanger 5 to the second heat exchanger 9 by bypassing the vaporizer 2 via the bypass channel L7. In other words, the heat transfer medium that bypasses the vaporizer 2 is not cooled by the liquid ammonia. Therefore, the temperature of the heat transfer medium entering the second heat exchanger 9 rises. With this configuration, corrosion of the second heat exchanger 9 can be prevented.

[0065] The system 100 also includes a valve V2 provided in the bypass channel L7, a first temperature sensor S1 located downstream of the second position C2 and upstream of the second heat exchanger 9 in the circulation channel L5 for measuring the temperature of the heat transfer medium, and a control device 90 that is communicatively connected to the valve V2 and the first temperature sensor S1. The control device 90 is configured to open the valve V2 when the temperature measured by the first temperature sensor S1 is lower than a first threshold, and to send at least a portion of the heat transfer medium from the first heat exchanger 5 to the second heat exchanger 9 via the bypass channel L7, bypassing the vaporizer 2. With this configuration, if the temperature of the heat transfer medium entering the second heat exchanger 9 is lower than a first threshold associated with corrosion, at least a portion of the heat transfer medium can be automatically sent to the bypass channel L7.

[0066] Furthermore, system 100 includes a heater H1 located downstream of the first heat exchanger 5 and upstream of the vaporizer 2 in the circulation channel L5. As described above, if the temperature of the heat transfer medium is low, there is a risk that the liquid ammonia may not be sufficiently vaporized in the vaporizer 2. However, with the above configuration, the heater H1 can further heat the heat transfer medium that has been heated in the first heat exchanger 5. Therefore, the liquid ammonia can be sufficiently vaporized in the vaporizer 2.

[0067] Furthermore, the system 100 is equipped with a second temperature sensor S2 located downstream of the vaporizer 2 in the circulation path L5 and which measures the temperature of the heat transfer medium. The control device 90 is communicatively connected to the heater H1 and the second temperature sensor S2. The control device 90 is configured to further heat the heat transfer medium heated in the first heat exchanger 5 with the heater H1 if the temperature measured by the second temperature sensor S2 is lower than a certain second threshold. With this configuration, if the temperature of the heat transfer medium cooled in the vaporizer 2 is lower than a second threshold associated with the vaporization of ammonia, the heat transfer medium can be automatically heated with the heater H1.

[0068] While embodiments have been described above with reference to the attached drawings, this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally fall within the technical scope of this disclosure.

[0069] For example, in the above embodiment, system 100 includes a second heater H2. In other embodiments, system 100 may not include a second heater H2. In yet another embodiment, system 100 may not include at least one of the above components other than the second heater H2.

[0070] This disclosure can promote the use of ammonia, which leads to a reduction in CO2 emissions, and thus can contribute, for example, to Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable and modern energy," Goal 12, "Ensure sustainable consumption and production patterns," and Goal 13, "Take urgent action to combat climate change and its impacts." [Explanation of Symbols]

[0071] 2. Vaporizer 3 Boiler 4. Air preheater 5 1st heat exchanger 8. Induced ventilation fan 9 Second heat exchanger 10 Flue gas desulfurization equipment 90 Control device 100 Combustion Systems C1 1st position C2 2nd position H1 heater H2 heater L4 flue L5 Circulation channel L7 Bypass Channel S1 First temperature sensor S2 Second temperature sensor V2 Valve

Claims

1. A vaporizer that heats liquid ammonia with a heat transfer medium, A boiler connected to the vaporizer and burning fuel containing ammonia from the vaporizer, An air preheater is placed in the flue connected to the boiler and heats the air with exhaust gas from the boiler, An induced draft fan is positioned downstream of the air preheater in the flue and guides the exhaust gas, An electrostatic precipitator is located in the flue downstream of the air preheater and upstream of the induced draft fan to remove particles from the exhaust gas, A first heat exchanger located downstream of the air preheater and upstream of the electrostatic precipitator in the flue, the first heat exchanger being circulatingly connected to the vaporizer by a circulation path, the first heat exchanger heating the heat transfer medium with the exhaust gas and supplying the heated heat transfer medium to the vaporizer, A second heat exchanger located downstream of the induced draft fan in the flue, the second heat exchanger located downstream of the vaporizer and upstream of the first heat exchanger in the circulation path, the second heat exchanger heats the heat transfer medium with the exhaust gas and supplies the heated heat transfer medium to the first heat exchanger, A combustion system equipped with the following features.

2. A flue gas desulfurization device is located downstream of the second heat exchanger in the flue and removes sulfur oxides from the exhaust gas. The combustion system according to claim 1, comprising:

3. In the circulation channel, a bypass channel connects a first position downstream of the first heat exchanger and upstream of the vaporizer and a second position downstream of the vaporizer and upstream of the second heat exchanger. A combustion system according to claim 1 or 2, comprising:

4. A valve provided in the bypass channel, A first temperature sensor is positioned downstream of the second position and upstream of the second heat exchanger in the circulation channel, and measures the temperature of the heat transfer medium. A control device that is communicatively connected to the valve and the first temperature sensor, wherein the control device is configured to open the valve and send at least a portion of the heat transfer medium from the first heat exchanger to the second heat exchanger via the bypass flow path, bypassing the vaporizer, when the temperature measured by the first temperature sensor is lower than a certain first threshold, The combustion system according to claim 3, comprising:

5. The combustion system according to claim 1 or 2, further comprising a heater located downstream of the first heat exchanger and upstream of the vaporizer in the circulation channel.

6. The combustion system according to claim 3, further comprising a heater located downstream of the first heat exchanger and upstream of the vaporizer in the circulation channel.

7. The combustion system according to claim 4, further comprising a heater located downstream of the first heat exchanger and upstream of the vaporizer in the circulation channel.

8. A second temperature sensor is positioned downstream of the vaporizer in the circulation channel and measures the temperature of the heat transfer medium. A control device that is communicatively connected to the heater and the second temperature sensor, wherein the control device is configured to further heat the heat transfer medium heated in the first heat exchanger with the heater if the temperature measured by the second temperature sensor is lower than a certain second threshold, The combustion system according to claim 5, comprising:

9. A second temperature sensor is positioned downstream of the vaporizer in the circulation channel and measures the temperature of the heat transfer medium. A control device that is communicatively connected to the heater and the second temperature sensor, wherein the control device is configured to further heat the heat transfer medium heated in the first heat exchanger with the heater if the temperature measured by the second temperature sensor is lower than a certain second threshold, The combustion system according to claim 6, comprising:

10. A second temperature sensor is positioned downstream of the vaporizer in the circulation channel and measures the temperature of the heat transfer medium. Equipped with, The combustion system according to claim 7, wherein the control device is communicably connected to the heater and the second temperature sensor, and is configured to further heat the heat transfer medium heated in the first heat exchanger with the heater if the temperature measured by the second temperature sensor is lower than a certain second threshold.

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