Heat engine system

Abstract

To provide a heat engine system capable of improving heat exchange efficiency when phase-changing a medium.SOLUTION: A heat engine system is equipped with a heat engine that is driven by gas fuel to generate exhaust gas, an exhaust heat recovery boiler that has a fuel heating line heating a liquid fuel by exchanging heat with the exhaust gas to generate the gas fuel, and recovers the exhaust heat of the exhaust gas, a liquid fuel supplying portion that supplies the liquid fuel to the fuel heating line, and a gas fuel compressor that compresses the gas fuel generated in the fuel heating line to supply it to the heat engine. At least a part of the fuel heating line is disposed in a range lower than a dew point that is a temperature range where the temperature of the exhaust gas passing through the exhaust heat recovery boiler is the dew point of moisture included in the exhaust gas or lower.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a heat engine system.

Background Art

[0002] There are engines (equipment, devices, etc.) that exhibit a predetermined function by introducing various media in a liquid state or a gaseous state from the outside. Prior to introducing the medium into such an engine, the medium may be subjected to a phase change. For example, a solid-state medium may be liquefied and then introduced into the engine. Alternatively, a liquid-state medium may be vaporized and then introduced into the engine.

[0003] For example, Patent Document 1 describes a gas turbine plant that introduces a medium in a liquid state into an engine after vaporizing it. This gas turbine plant includes a gas turbine, a heating device, and a cracked gas compressor. The gas turbine exhausts exhaust gas generated by burning fuel. The heating device heats ammonia gas generated by heating liquefied ammonia to produce a cracked gas containing hydrogen gas and nitrogen gas. The cracked gas compressor boosts the cracked gas from the heating device to a pressure higher than the input pressure that can be input into the gas turbine. In this gas turbine plant, liquid ammonia is vaporized using the exhaust gas from the gas turbine. The ammonia thus phase-changed from a liquid to a gas is used as fuel (input medium) to produce a cracked gas containing hydrogen gas and nitrogen gas and supplied to the gas turbine.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using a medium that undergoes a phase change, as described in Patent Document 1, it is always desirable to effectively supply the heat required for the phase change. Generally, when a medium undergoes a phase change to a phase with high enthalpy, such as vaporization or melting, a much larger amount of heat is required compared to simply increasing the temperature. Therefore, since a phase change to a phase with high enthalpy leads to increased energy consumption, effective heat supply is particularly important.

[0006] This disclosure has been made to solve the above problems and aims to provide a heat engine system that can effectively supply the large amount of heat necessary to change the input medium from a low-enthalpy phase to a high-enthalpy phase by effectively utilizing the waste heat generated when changing the phase of a heat medium from a high-enthalpy phase to a low-enthalpy phase. [Means for solving the problem]

[0007] To solve the above problems, the heat engine system according to the present disclosure comprises a heat engine driven by gaseous fuel to generate exhaust gas, a waste heat recovery boiler having a fuel heating line that heats liquid fuel by heat exchange with the exhaust gas to generate the gaseous fuel and recovers the waste heat from the exhaust gas, a liquid fuel supply unit that supplies the liquid fuel to the fuel heating line, and a gas fuel compressor that compresses the gaseous fuel generated in the fuel heating line and supplies it to the heat engine, wherein at least a part of the fuel heating line is located in the waste heat recovery boiler in a region below the dew point, which is a temperature range where the temperature of the exhaust gas passing through the waste heat recovery boiler is below the dew point of the water contained in the exhaust gas. The liquid fuel supply unit further includes a liquid fuel compression unit that compresses the liquid fuel supplied to the fuel heating line in a range where the saturation temperature of the liquid fuel is below the dew point of the water, and a gas fuel supply line that connects the fuel heating line and the gas fuel compressor and supplies the gas fuel generated by vaporizing the liquid fuel in the fuel heating line to the gas fuel compressor. Furthermore, the heat engine system according to this disclosure comprises a heat engine driven by gaseous fuel to generate exhaust gas, a fuel heating line that generates gaseous fuel by heating liquid fuel through heat exchange with the exhaust gas, and a waste heat recovery boiler that recovers waste heat from the exhaust gas, a liquid fuel supply unit that supplies the liquid fuel to the fuel heating line, and a gas fuel compressor that compresses the gaseous fuel generated in the fuel heating line and supplies it to the heat engine, wherein at least a portion of the fuel heating line is the waste heat that passes through the waste heat recovery boiler The exhaust gas is positioned in a region below the dew point, which is a temperature range where the temperature of the gas is below the dew point of the moisture contained in the exhaust gas. The exhaust heat recovery boiler has an evaporator that vaporizes the liquid fuel to produce the gaseous fuel by heat exchange with the exhaust gas and condenses the moisture contained in the exhaust gas. The fuel heating line heats the liquid fuel in the evaporator to produce the gaseous fuel, generates steam using the exhaust heat recovered by the exhaust heat recovery boiler, and heats the liquid fuel by heat exchange with the exhaust gas after the steam has been generated. Furthermore, the heat engine system according to this disclosure comprises a heat engine driven by gaseous fuel to generate exhaust gas, a heat recovery boiler having a fuel heating line that heats liquid fuel by heat exchange with the exhaust gas to generate the gaseous fuel and recovers the waste heat from the exhaust gas, a liquid fuel supply unit that supplies the liquid fuel to the fuel heating line, and a gas fuel compressor that compresses the gaseous fuel generated in the fuel heating line and supplies it to the heat engine, wherein at least a portion of the fuel heating line is located in the below-dew point region of the heat recovery boiler, which is a temperature region where the temperature of the exhaust gas passing through the heat recovery boiler is below the dew point of the water contained in the exhaust gas, and the heat recovery boiler recovers the liquid by heat exchange with the exhaust gas The fuel heating line has an evaporator that vaporizes the fuel to produce the gaseous fuel and condenses the moisture contained in the exhaust gas, and the fuel heating line heats the liquid fuel in the evaporator to produce the gaseous fuel and generates steam using the waste heat recovered by the waste heat in the waste heat recovery boiler, and the fuel heating line heats the liquid fuel by heat exchange with the exhaust gas after the steam has been generated, and the waste heat recovery boiler comprises a low-pressure evaporator and a high-pressure evaporator, which are arranged in the order of the low-pressure evaporator and the high-pressure evaporator from downstream to upstream in the direction in which the exhaust gas flows in the waste heat recovery boiler, and the low-pressure evaporator and the high-pressure evaporator each convert water into steam, and the evaporator is arranged downstream of the low-pressure evaporator in the direction in which the exhaust gas flows.

[0008] The heat engine system according to this disclosure is a heat engine system that heats and causes a phase change in an input medium before it is fed into a target engine, comprising: a heat exchange unit that causes a phase change in the heat medium and a phase change in the input medium by exchanging heat between the input medium and a heat medium discharged from the target engine and at a higher temperature than the input medium; and an input medium compression unit that compresses the input medium that has undergone a phase change in the heat exchange unit and supplies it to the target engine. A liquid input medium compression unit compresses the input medium, which is a liquid before it is supplied to the heat exchange unit, to a pressure lower than the pressure at which the saturation temperature or pseudocritical temperature of the input medium becomes the temperature at which the phase change occurs when the heat medium is supplied to the heat exchange unit. It is equipped with. [Effects of the Invention]

[0009] The heat engine system of this disclosure provides a heat engine system that can effectively supply the heat necessary to change the phase of a medium. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the configuration of a heat engine system according to the first embodiment of this disclosure. [Figure 2] This diagram functionally illustrates the flow of ammonia in the heat engine system described above. [Figure 3] This figure shows the correlation between the temperature of exhaust gas, ammonia, and steam and the amount of heat exchanged in the above-mentioned thermal core system. [Figure 4] This diagram functionally illustrates the configuration of a heat engine system according to the second embodiment of this disclosure. [Modes for carrying out the invention]

[0011] The embodiments for implementing the heat engine system according to this disclosure will be described below with reference to the attached drawings. However, this disclosure is not limited to these embodiments.

[0012] <First Embodiment> (Configuration of a heat engine system) The heat engine system 100 heats the input medium before it is fed into the target engine, causing a phase change. In the first embodiment, the heat engine system 100 is a combined cycle plant that drives a steam turbine 120 with the exhaust gas EG of a gas turbine 110, while simultaneously heating ammonia (NH3), the input medium to the gas turbine 110, with the exhaust gas EG. As shown in Figure 1, the heat engine system 100 comprises a gas turbine (heat engine, target engine) 110, a steam turbine 120, a waste heat recovery boiler (heat exchange unit) 130, a liquid fuel supply unit 145, and a gas fuel compressor 148. In other words, the heat engine system 100 heats liquid ammonia (ammonia in liquid state) FL, the input medium before it is fed into the target engine, the gas turbine 110, causing a phase change to ammonia gas (ammonia in gaseous state) FG.

[0013] (Gas turbine configuration) The gas turbine 110 is driven by ammonia gas FG, which is a gaseous fuel, to produce exhaust gas EG. In the heat engine system 100 of this embodiment, the exhaust gas EG discharged from the gas turbine 110 is used as a heat transfer medium. The gas turbine 110 comprises an air compressor 112, a combustor 113, and a turbine 114.

[0014] The air compressor 112 compresses air taken in from the outside. The combustor 113 generates combustion gas by burning ammonia gas FG in the air compressed by the air compressor 112. The ammonia gas FG is compressed by the gas fuel compressor 148 (described later) and supplied to the combustor 113.

[0015] The turbine 114 is driven by high-temperature, high-pressure combustion gases generated in the combustor 113. The turbine rotor of the turbine 114 and the compressor rotor of the air compressor 112 are interconnected to form a gas turbine rotor 115. A generator 117, for example, is connected to the gas turbine rotor 115. The exhaust gas EG discharged from the turbine 114 is supplied to the heat recovery boiler 130.

[0016] (Configuration of the steam turbine) The steam turbine 120 is driven by utilizing the exhaust heat of the exhaust gas EG recovered by the exhaust heat recovery boiler 130. Specifically, the steam turbine 120 is driven by the steam generated by the exhaust heat recovery boiler 130. The steam turbine 120 includes a high-pressure steam turbine 121, an intermediate-pressure steam turbine 122, a low-pressure steam turbine 123, a condenser 125, and a feed water pump 127.

[0017] The high-pressure steam turbine 121, the intermediate-pressure steam turbine 122, and the low-pressure steam turbine 123 are each driven by the steam generated in the first exhaust heat recovery boiler 131 of the exhaust heat recovery boiler 130. The turbine rotor of the high-pressure steam turbine 121, the turbine rotor of the intermediate-pressure steam turbine 122, and the turbine rotor of the low-pressure steam turbine 123 are interconnected to form a single steam turbine rotor 124. This steam turbine rotor 124 is connected to the generator 128.

[0018] The high-pressure steam turbine 121 is driven by the steam superheated by the high-pressure superheater 138 of the first exhaust heat recovery boiler 131 described below. The intermediate-pressure steam turbine 122 is driven by the steam discharged from the high-pressure steam turbine 121. The low-pressure steam turbine 123 is driven by the steam superheated by the low-pressure superheater 135 described below and the steam discharged from the intermediate-pressure steam turbine 122.

[0019] The condenser 125 returns the steam discharged from the low-pressure steam turbine 123 to water. The feed water pump 127 returns the water in the condenser 125 to the first exhaust heat recovery boiler 131 described below. Specifically, the feed water pump 127 returns the water in the condenser 125 to the low-pressure economizer 132 described below.

[0020] (Configuration of the exhaust heat recovery boiler) The exhaust heat recovery boiler 130 recovers the exhaust heat (thermal energy) of the exhaust gas EG discharged from the gas turbine 110. The exhaust heat recovery boiler 130 has a first exhaust heat recovery boiler 131 and a second exhaust heat recovery boiler 141.

[0021] The first waste heat recovery boiler 131 utilizes the thermal energy of the exhaust gas EG discharged from the gas turbine 110 to generate steam for driving the steam turbine 120. The first waste heat recovery boiler 131 includes a low-pressure economizer (ECO-LP) 132, a low-pressure evaporator (EVA-LP) 133, a high-pressure pump 134, a low-pressure superheater (SH-LP) 135, a high-pressure economizer (ECO-HP) 136, a high-pressure evaporator (EVA-HP) 137, and a high-pressure superheater (SH-HP) 138. Note that the configuration of the first waste heat recovery boiler 131 is merely an example and can be changed as appropriate.

[0022] Here, in the direction in which the exhaust gas EG flows in the first waste heat recovery boiler 131, the side closer to the gas turbine 110 is defined as the upstream side, and the opposite side, closer to the second waste heat recovery boiler 141, is defined as the downstream side. Inside the first waste heat recovery boiler 131, the low-pressure economizer 132, low-pressure evaporator 133, low-pressure superheater 135, high-pressure economizer 136, high-pressure evaporator 137, and high-pressure superheater 138 are arranged in that order from downstream to upstream.

[0023] The low-pressure economizer 132 heats the water supplied from the condenser 125 of the steam turbine 120. The low-pressure evaporator 133 turns the water heated in the low-pressure economizer 132 into steam. The low-pressure evaporator 133 illustrated in this embodiment is a natural circulation boiler with a drum positioned on top (the same applies to the high-pressure evaporator 137). The high-pressure pump 134 pressurizes the water heated in the low-pressure economizer 132 and supplies it to the high-pressure economizer 136. The low-pressure superheater 135 superheats the steam generated in the low-pressure evaporator 133. The steam superheated by the low-pressure superheater 135 is supplied to the low-pressure steam turbine 123.

[0024] The high-pressure economizer 136 heats the water pressurized by the high-pressure pump 134. The high-pressure evaporator 137 heats the water heated by the high-pressure economizer 136 to produce steam. The high-pressure evaporator 137 is an evaporator with a higher pressure than the other evaporators in the waste heat recovery boiler 130, namely the low-pressure evaporator 133. In other words, the high-pressure evaporator 137 is the evaporator with the highest pressure in the waste heat recovery boiler 130. The high-pressure superheater 138 superheats the steam generated in the high-pressure evaporator 137. The steam superheated by the high-pressure superheater 138 is supplied to the high-pressure steam turbine 121.

[0025] The second waste heat recovery boiler 141 utilizes the thermal energy of the exhaust gas EG discharged from the gas turbine 110 to produce ammonia gas (gas fuel) FG, which is used as fuel for the gas turbine 110. The second waste heat recovery boiler 141 utilizes the thermal energy of the exhaust gas EG to cause a phase change in liquid ammonia (liquid fuel, input medium) FL to produce ammonia gas FG. The exhaust gas EG that has been used for steam generation in the first waste heat recovery boiler 131 is supplied to the second waste heat recovery boiler 141. In other words, the second waste heat recovery boiler 141 utilizes the thermal energy of the exhaust gas EG, which has cooled down after being used for steam generation in the first waste heat recovery boiler 131.

[0026] The second waste heat recovery boiler 141 includes a fuel heating line 140, a preheater 142, an evaporator (heat exchange section) 143, and a superheater 144. Here, the side closer to the first waste heat recovery boiler 131 is considered the upstream side, and the opposite side closer to the chimney 150 is considered the downstream side, in the direction in which the exhaust gas EG flows in the second waste heat recovery boiler 141. Inside the second waste heat recovery boiler 141, the preheater 142, evaporator 143, and superheater 144 are arranged in that order from downstream to upstream.

[0027] The fuel heating line 140 recovers waste heat from the exhaust gas EG and generates ammonia gas FG by heating liquid ammonia FL through heat exchange with the exhaust gas EG. Liquid ammonia FL is supplied to the fuel heating line 140 from the liquid fuel supply unit 145. The liquid fuel supply unit 145 includes a liquid fuel compression unit 146. The liquid fuel compression unit 146 compresses the liquid ammonia FL supplied from a liquid ammonia supply source (not shown), such as a liquid ammonia tank, while it remains in a liquid state. In this embodiment, the liquid fuel compression unit 146 is a pump. As will be described in detail later, the liquid fuel compression unit 146 compresses the liquid ammonia FL supplied to the fuel heating line 140 within a range where the saturation temperature of the liquid ammonia FL is below the dew point of the water contained in the exhaust gas EG sent to the second waste heat recovery boiler 141. In other words, if Tegdp is the dew point temperature of the moisture contained in the exhaust gas EG sent to the second waste heat recovery boiler 141, the liquid fuel compression unit 146, i.e., the pump, compresses the liquid ammonia FL to a pressure lower than the pressure at which the saturation temperature of liquid ammonia FL becomes Tegdp.

[0028] Furthermore, the fuel heating line 140 is positioned so that it passes through a location in the second waste heat recovery boiler 141 where the temperature of the exhaust gas EG passing through the second waste heat recovery boiler 141 is below the dew point of the water contained in the exhaust gas EG, which is the below-dew point region 141a. Therefore, the fuel heating line 140 heats the supplied liquid ammonia FL by heat exchange with the exhaust gas EG after steam is generated in the first waste heat recovery boiler 131. The fuel heating line 140 uses the exhaust gas EG to supply ammonia gas FG generated from the liquid ammonia FL to the gas fuel compressor 148.

[0029] The preheater 142 heats (preheats) the liquid ammonia FL compressed in the liquid fuel compression section 146 using the thermal energy of the exhaust gas EG. The preheater 142 is supplied with exhaust gas EG that has passed through the evaporator 143. The preheater 142 heats the liquid ammonia FL in its liquid state through heat exchange with the exhaust gas EG. In other words, the preheater 142 heats the liquid ammonia FL without causing a phase change. The exhaust gas EG that has passed through the evaporator 143 has decreased in temperature due to heat exchange with the liquid ammonia FL in the evaporator 143. In this embodiment, the preheater 142 is supplied with the exhaust gas EG with the lowest temperature in the second waste heat recovery boiler 141.

[0030] The evaporator 143 vaporizes the liquid ammonia FL heated in the preheater 142 using the thermal energy of the exhaust gas EG to produce ammonia gas FG. The evaporator 143 produces ammonia gas FG by changing the phase of liquid ammonia FL. In other words, the evaporator 143 changes the phase of ammonia, which is a liquid fuel, from a liquid state to a gaseous state. The evaporator 143 is supplied with exhaust gas EG that has passed through the superheater 144. The evaporator 143 condenses the water contained in the exhaust gas EG that has passed through the superheater 144 by exchanging heat between the liquid ammonia FL and the exhaust gas EG. In other words, the evaporator 143 causes a phase change in the exhaust gas EG and a phase change in the liquid ammonia FL simultaneously by exchanging heat between the exhaust gas EG, which is at a higher temperature than the liquid ammonia FL, and the liquid ammonia FL. The evaporator 143 is located in the second waste heat recovery boiler 141 at a position where the temperature of the exhaust gas EG is below the dew point region 141a. In the second waste heat recovery boiler 141 of this embodiment, only the preheater 142 and the evaporator 143 are positioned in a region 141a where the temperature of the exhaust gas EG is below the dew point.

[0031] The superheater 144 raises the temperature of the ammonia gas FG produced in the evaporator 143 by heat exchange with the exhaust gas EG supplied to the evaporator 143. The exhaust gas EG that has passed through the superheater 144 has its temperature lowered by heat exchange with the ammonia gas FG in the superheater 144. The exhaust gas EG discharged from the gas turbine 110 and passing through the first waste heat recovery boiler 131 is supplied to the second waste heat recovery boiler 141 first. In other words, the superheater 144 in this embodiment is supplied with the hottest exhaust gas EG in the second waste heat recovery boiler 141. The superheater 144 heats the ammonia gas FG to a temperature slightly lower than the temperature of the exhaust gas EG (for example, around 5°C to 15°C). The superheater 144 heats the ammonia gas FG in a gaseous state by heat exchange with the exhaust gas EG. In other words, the superheater 144 heats the ammonia gas FG without causing a phase change.

[0032] The fuel heating line 140 passes ammonia through the preheater 142, evaporator 143, and superheater 144 in that order. The ammonia gas FG generated in the fuel heating line 140 is supplied to the gas fuel compressor (input medium compression unit) 148 via the gas fuel supply line 147. The gas fuel compressor 148 compresses the ammonia gas FG generated in the fuel heating line 140 and supplies it to the gas turbine 110. In other words, the gas fuel compressor 148 pressurizes the ammonia gas FG just before it is supplied to the gas turbine 110 after passing through the second waste heat recovery boiler 141. The gas fuel compressor 148 pressurizes the ammonia gas FG in its gaseous state to the input pressure to the combustor 113. The ammonia gas FG pressurized by the gas fuel compressor 148 is supplied directly to the combustor 113 without passing through any other devices.

[0033] As shown in Figures 2 and 3, the exhaust gas EG generates steam in the first waste heat recovery boiler 131 through heat exchange with water. During the steam generation process, the temperature of the exhaust gas EG gradually decreases (points P10 to P11 in Figure 3). The water supplied from the condenser 125 to the first waste heat recovery boiler 131 via the feedwater pump 127 is heated and turned into steam through heat exchange with the exhaust gas EG in the first waste heat recovery boiler 131. As a result, the temperature of the water (steam) gradually increases, contrary to the temperature of the exhaust gas EG (points P20 to P21 in Figure 3; in reality, it is more complex due to water evaporation, etc. Here, for simplicity, points P20 and P21 are connected by a straight line (dashed line)). The exhaust gas EG, whose temperature has decreased in the first waste heat recovery boiler 131, is supplied to the second waste heat recovery boiler 141.

[0034] The exhaust gas EG passes sequentially through the superheater 144, evaporator 143, and preheater 142 in the second waste heat recovery boiler 141. During this process, the temperature of the exhaust gas EG decreases further due to heat exchange with liquid ammonia FL or ammonia gas FG (points P11 → P12 → P13 → P14 in Figure 3). After passing through the second waste heat recovery boiler 141, the exhaust gas EG is discharged into the atmosphere from the chimney 150.

[0035] Liquid ammonia FL is compressed in the liquid fuel compression section 146 (up to point P1 in Figure 3) as it is supplied from the liquid ammonia source to the fuel heating line 140. The liquid ammonia FL is compressed in the liquid fuel compression section 146 to a extent that the saturation temperature of the liquid ammonia FL is below the dew point Pr of the water contained in the exhaust gas EG (see Figure 3).

[0036] Compressed liquid ammonia FL is supplied to the fuel heating line 140. In the fuel heating line 140, liquid ammonia FL first passes through the preheater 142 and is heated by heat exchange with the exhaust gas EG, and its temperature is raised while remaining in a liquid state (point P1 → point P2 in Figure 3). The temperature of the heated liquid ammonia FL (point P2 in Figure 3) is set to be lower than the dew point Pr of the water contained in the exhaust gas EG by a predetermined temperature difference. Meanwhile, the exhaust gas EG passes through the first waste heat recovery boiler 131, superheater 144, and evaporator 143, and its temperature drops to below the dew point Pr of the water contained in the exhaust gas EG (point P13 in Figure 3). In the preheater 142, the exhaust gas EG drops to an even lower temperature (point P14 in Figure 3) by heat exchange with the liquid ammonia FL.

[0037] The liquid ammonia FL, heated in the preheater 142, is further heated in the evaporator 143 through heat exchange with the exhaust gas EG. The evaporator 143 heats the liquid ammonia FL until it is vaporized, producing ammonia gas FG (points P2 to P3 in Figure 3). In other words, the evaporator 143 converts liquid ammonia FL into a gas to produce ammonia gas FG. On the other hand, when the exhaust gas EG is supplied to the evaporator 143, its temperature has decreased due to passing through the first waste heat recovery boiler 131 and the superheater 144, but it is still higher than the dew point Pr of the water contained in the exhaust gas EG (point P12 in Figure 3). Subsequently, the exhaust gas EG cools down to the dew point Pr of the water contained in the exhaust gas EG through heat exchange with the liquid ammonia FL in the evaporator 143. As a result, the water contained in the exhaust gas EG condenses (points P12 to Pr to P13 in Figure 3).

[0038] The ammonia gas FG generated in the evaporator 143 is further heated by heat exchange with the exhaust gas EG in the superheater 144 (point P3 → point P4 in Figure 3). In the superheater 144, the ammonia gas FG is heated without undergoing a phase change while remaining in a gaseous state. After passing through the superheater 144, the temperature of the ammonia gas FG (point P4 in Figure 3) is slightly lower than the temperature of the exhaust gas EG (point P11 in Figure 3). On the other hand, the temperature of the exhaust gas EG decreases due to heat exchange with the ammonia gas FG in the superheater 144 (point P11 → point P12 in Figure 3). The temperature of the exhaust gas EG discharged from the superheater 144 and supplied to the evaporator 143 (point P12) is higher than the dew point Pr of the water contained in the exhaust gas EG.

[0039] The ammonia gas FG, having passed through the superheater 144, is sent to the gas fuel compressor 148 via the gas fuel supply line 147. In the gas fuel compressor 148, the ammonia gas FG is pressurized to the pressure required to feed into the combustor 113. The ammonia gas FG, pressurized in the gas fuel compressor 148, is then supplied to the gas turbine 110 without passing through any other equipment. The gas turbine 110 is driven by the supplied ammonia gas FG as fuel to produce exhaust gas EG. The exhaust gas EG is then supplied to the first waste heat recovery boiler 131.

[0040] (Effects and Benefits) In the heat engine system 100 with the above configuration, the gas turbine 110 is driven by ammonia gas FG to generate exhaust gas EG. The exhaust gas EG generated by the gas turbine 110 is supplied to the first waste heat recovery boiler 131. The first waste heat recovery boiler 131 uses the thermal energy of the exhaust gas EG to generate steam from water. The exhaust gas EG used to generate steam is supplied to the second waste heat recovery boiler 141 at a reduced temperature. Liquid ammonia FL is also supplied from the liquid fuel supply unit 145 to the fuel heating line 140. In the second waste heat recovery boiler 141, the liquid ammonia FL supplied from the liquid fuel supply unit 145 is heated by heat exchange with the exhaust gas EG. The second waste heat recovery boiler 141 heats the liquid ammonia FL to cause a phase change and generates ammonia gas FG. The ammonia gas FG generated in the second waste heat recovery boiler 141 is supplied from the fuel heating line 140 to the gas fuel compressor 148. The gas fuel compressor 148 compresses ammonia gas FG and supplies it to the gas turbine 110. The fuel heating line 140 is located in the dew point region 141a, which is the temperature range where the temperature of the exhaust gas EG passing through the second waste heat recovery boiler 141 is below the dew point Pr of the water contained in the exhaust gas EG. Therefore, when heating liquid ammonia FL in the fuel heating line 140 by heat exchange with the exhaust gas EG, the latent heat, which is the thermal energy released when the water contained in the exhaust gas EG condenses, can be utilized. In this way, when heating liquid ammonia FL to change its phase and generate ammonia gas FG, it is possible to utilize not only the sensible heat of the exhaust gas EG that is normally used in heat exchange, but also the latent heat released when the water contained in the exhaust gas EG condenses. This allows for the efficient and complete utilization of the thermal energy of the exhaust gas EG. Consequently, it is possible to effectively utilize the large amount of heat generated when changing the phase of water in the exhaust gas EG, which was previously often discarded along with the exhaust gas EG, and to effectively supply the large amount of heat necessary to change the phase of liquid ammonia FL.In other words, by effectively utilizing the waste heat generated when the water in the exhaust gas EG, which is the heat transfer medium, undergoes a phase change from a high-enthalpy phase (gas) to a low-enthalpy phase (liquid), it becomes possible to effectively supply the large amount of heat required when the liquid ammonia FL, which is the input medium, undergoes a phase change from a low-enthalpy phase (liquid) to a high-enthalpy phase (gas).

[0041] Furthermore, in the heat engine system 100, the liquid fuel compression unit 146 compresses the liquid ammonia FL before it is supplied to the fuel heating line 140 to a range where the saturation temperature of the liquid ammonia FL is below the dew point Pr of the water contained in the exhaust gas EG. Therefore, when ammonia gas FG is generated from liquid ammonia FL in the fuel heating line 140, the latent heat generated when the water contained in the exhaust gas EG condenses is not prevented from being utilized. As a result, the water in the exhaust gas EG is condensed, heat exchange occurs between the exhaust gas EG and the liquid ammonia FL, and the liquid ammonia FL can be vaporized. Therefore, a large amount of heat necessary to vaporize the liquid ammonia FL can be supplied using the latent heat generated when the water in the exhaust gas EG condenses. Moreover, because the liquid ammonia FL is pressurized, the ammonia gas FG supplied from the fuel heating line 140 to the gas fuel compressor 148 is also pressurized. Therefore, the power required by the gas fuel compressor 148 to pressurize the ammonia gas FG to the input pressure to the combustor 113 can be reduced. This reduces the installation cost of the gas fuel compressor 148.

[0042] Furthermore, in the heat engine system 100, the evaporator 143 exchanges heat between liquid ammonia FL and exhaust gas EG. As a result, liquid ammonia FL vaporizes into ammonia gas FG. At the same time, the water contained in the exhaust gas EG condenses. In this way, by utilizing the evaporator 143 in the fuel heating line 140, a structure can be easily installed that generates ammonia gas FG from liquid ammonia FL using the latent heat of the water contained in the exhaust gas EG.

[0043] Furthermore, in the heat engine system 100, the preheater 142 heats the liquid ammonia FL while it remains in a liquid state by exchanging heat with the exhaust gas EG, whose temperature has decreased after heat exchange with the liquid ammonia FL in the evaporator 143. This allows for further utilization of the thermal energy of the exhaust gas EG that has exchanged heat with the liquid ammonia FL to generate ammonia gas FG. In addition, as the temperature of the liquid ammonia FL rises in the preheater 142, the amount of thermal energy required to vaporize the liquid ammonia FL in the evaporator 143 is reduced. Therefore, the heat exchange efficiency when changing the phase of liquid ammonia FL can be further increased.

[0044] Furthermore, in the heat engine system 100, the superheater 144 further increases the temperature of the ammonia gas FG produced in the evaporator 143 by exchanging heat with the exhaust gas EG before it is supplied to the evaporator 143. This allows the superheater 144 to obtain thermal energy from the exhaust gas EG before it is supplied to the evaporator 143, thereby increasing the temperature of the ammonia gas FG produced in the evaporator 143. By exchanging heat with the ammonia gas FG in the superheater 144, the temperature of the exhaust gas EG supplied to the evaporator 143 decreases. This prevents the temperature of the exhaust gas EG supplied to the evaporator 143 from becoming excessively high, making it easier to achieve the dew point region 141a within the second waste heat recovery boiler 141, which is the temperature range where the temperature of the exhaust gas EG is below the dew point Pr of the water contained in the exhaust gas EG. In addition, the temperature of the ammonia gas FG supplied from the fuel heating line 140 to the gas fuel compressor 148 is higher. Therefore, the temperature of the ammonia gas FG at the outlet of the gas fuel compressor 148, i.e., at the inlet of the combustor 113, also increases. Therefore, the heat content of the ammonia gas FG introduced into the combustor 113 increases, and the consumption of the ammonia gas FG fuel can be reduced. Consequently, the efficiency of the heat engine system 100 can be improved.

[0045] Furthermore, in the heat engine system 100, the waste heat from the exhaust gas EG discharged from the gas turbine 110 is used to generate steam for driving the steam turbine 120 in the first waste heat recovery boiler 131 through a phase change. Subsequently, in the fuel heating line 140, the waste heat from the exhaust gas EG, whose temperature has decreased after being used to generate steam in the first waste heat recovery boiler 131, is used to generate ammonia gas FG. In this way, the thermal energy of the exhaust gas EG is used to generate steam and ammonia gas FG, making efficient use of the thermal energy of the exhaust gas EG without waste.

[0046] (Modification of the first embodiment) In the first embodiment described above, the fuel heating line 140 for vaporizing liquid ammonia FL was located only in the second waste heat recovery boiler 141, which is located downstream of the first waste heat recovery boiler 131 in the flow direction of the exhaust gas EG. However, the configuration of the fuel heating line 140 is not limited to this form. For example, if the dew point region, which is the temperature range in which the temperature of the exhaust gas EG is below the dew point Pr of the water contained in the exhaust gas EG, is located within the first waste heat recovery boiler 131, the fuel heating line 140 may be arranged to pass through the first waste heat recovery boiler 131. In that case, for example, the low-pressure economizer 132 may be divided into two, and a device for vaporizing liquid ammonia FL may be separately placed between them.

[0047] Furthermore, in the first embodiment described above, the fuel heating line 140 directly exchanged heat between liquid ammonia FL and exhaust gas EG. However, the configuration of the fuel heating line 140 is not limited to this form. For example, liquid ammonia FL may be heated and vaporized using an intermediate heat transport medium heated by exhaust gas EG. As the intermediate heat transport medium, for example, water, various oils, various alcohols, etc., can be used.

[0048] Furthermore, in the first embodiment described above, a gas turbine 110 was given as an example of a heat engine driven by ammonia gas FG to generate exhaust gas EG, but other devices may be used. Examples of heat engines driven by ammonia gas FG to generate exhaust gas EG include reciprocating engines and fuel cells.

[0049] Furthermore, in the first embodiment described above, liquid ammonia FL was used as the liquid fuel and ammonia gas FG as the gaseous fuel, but other fluids may be used. Examples of liquid and gaseous fuels that undergo phase change include methanol, ethanol, dimethyl ether, and the like.

[0050] <Second Embodiment> Next, a second embodiment of the heat engine system according to this disclosure will be described. In the second embodiment described below, components common to the first embodiment are denoted by the same reference numerals in the figures and their descriptions are omitted.

[0051] As shown in Figure 4, the heat engine system 200 of the second embodiment is a urea synthesis plant that synthesizes urea (NH2CONH2) by chemical reaction between ammonia (NH3) and carbon dioxide (CO2). The heat engine system 200 comprises a urea synthesis facility 210, a first heat exchange section (heat exchange unit) 243, a second heat exchange section 245, a first compression section 247, a second compression section 248, and a gas compression section (input medium compression section) 249. In other words, the heat engine system 200 heats liquid ammonia (ammonia in liquid state) FL, which is the input medium before it is fed into the urea synthesis facility 210, which is the engine to be fed into, to change its phase to ammonia gas (ammonia in gaseous state) FG.

[0052] As shown in equation (1) below, the urea synthesis equipment 210 chemically synthesizes ammonia gas (ammonia in gaseous state) FG and carbon dioxide gas CG, which are input media, to produce liquid urea (NH2CONH2)M. 2NH3+CO2→NH2CONH2+H2O…(1) In the heat engine system 200 of this embodiment, liquid urea M produced in the urea synthesis facility 210 according to equation (1) above is used as the heat transfer medium. Liquid urea M is at a higher temperature than ammonia gas FG and carbon dioxide gas CG before the synthesis reaction.

[0053] The first heat exchange unit 243 and the second heat exchange unit 245 recover the waste heat (thermal energy) of the liquid urea M produced in the urea synthesis equipment 210. The first heat exchange unit 243 exchanges heat between the liquid urea M, which is discharged from the urea synthesis equipment 210 and is at a higher temperature than liquid ammonia FL, and liquid ammonia FL. The first heat exchange unit 243 causes a phase change in both the liquid urea M and liquid ammonia FL through heat exchange between the liquid urea M and liquid ammonia FL. Specifically, in the first heat exchange unit 243, liquid ammonia FL undergoes a phase change and vaporizes, generating ammonia gas FG. On the other hand, in the first heat exchange unit 243, liquid urea M undergoes a phase change and solidifies, generating solid urea. The first heat exchange unit 243 supplies the generated ammonia gas FG to the gas compression unit 249.

[0054] The first compression unit 247 compresses the liquid ammonia FL before it is supplied to the first heat exchange unit 243. The first compression unit 247 compresses the liquid ammonia FL supplied from a liquid ammonia supply source (not shown), such as a liquid ammonia tank, while it is still in a liquid state. In this embodiment, the first compression unit 247 is a pump. The first compression unit 247 compresses the liquid ammonia FL supplied to the first heat exchange unit 243 to a range where the saturation temperature of the liquid ammonia FL is below the freezing point of the liquid urea M supplied to the first heat exchange unit 243 (for example, 133-135°C). In other words, if the freezing point of the urea M supplied to the first heat exchange unit 243 is Tms, the first compression unit 247, i.e., the pump, compresses the liquid ammonia FL to a pressure lower than the pressure at which the saturation temperature of the liquid ammonia FL becomes Tms.

[0055] The gas compression unit 249 compresses the ammonia gas FG, which has undergone a phase change from liquid to gaseous state in the first heat exchange unit 243, and supplies it to the urea synthesis plant 210. In other words, the gas compression unit 249 increases the pressure of the ammonia gas FG just before it is supplied to the urea synthesis plant 210 after passing through the first heat exchange unit 243. The gas compression unit 249 increases the pressure of the ammonia gas FG in its gaseous state to the input pressure to the urea synthesis plant 210. The ammonia gas FG, which has been increased in pressure by the gas compression unit 249, is supplied directly to the urea synthesis plant 210 without passing through any other devices.

[0056] Meanwhile, the liquid carbon dioxide (CL) supplied to the urea synthesis equipment 210 is supplied from the second heat exchange unit 245. The second heat exchange unit 245 exchanges heat between liquid urea (M), which is discharged from the urea synthesis equipment 210 and is at a higher temperature than the liquid carbon dioxide (CL), and liquid carbon dioxide (CL). The second heat exchange unit 245 causes phase changes in both liquid urea (M) and liquid carbon dioxide (CL) through heat exchange between liquid carbon dioxide (CL) and liquid urea (M). Specifically, in the second heat exchange unit 245, liquid carbon dioxide (CL) undergoes a phase change and vaporizes, producing carbon dioxide gas (CG). Meanwhile, in the second heat exchange unit 245, liquid urea (M) undergoes a phase change and solidifies, producing solid urea.

[0057] The second compression unit 248 compresses the liquid carbon dioxide CL before it is supplied to the second heat exchange unit 245. The second compression unit 248 compresses the liquid carbon dioxide CL supplied from a liquid carbon dioxide supply source (not shown), such as a carbon dioxide tank, while it remains in a liquid state. In this embodiment, the second compression unit 248 is a pump. The second compression unit 248 compresses the liquid ammonia FL supplied to the second heat exchange unit 245 within a range where the saturation temperature of the liquid carbon dioxide CL is below the freezing point of the liquid urea M supplied to the second heat exchange unit 245 (for example, 133-135°C). In other words, if the freezing point of the urea M supplied to the second heat exchange unit 245 is Tms2, the second compression unit 248, i.e., the pump, compresses the liquid ammonia FL to a pressure lower than the pressure at which the pseudocritical temperature of the liquid carbon dioxide CL becomes Tms2.

[0058] (Effects and Benefits) According to the heat engine system 200 described above, the liquid ammonia FL compressed in the first compression section 247 undergoes a phase change (vaporization) in the first heat exchange section 243 through heat exchange with liquid urea M discharged from the urea synthesis facility 210. The liquid urea M also undergoes a phase change (solidification) through heat exchange with the liquid ammonia FL. The gas compression section 249 compresses the ammonia gas FG generated by the phase change in the first heat exchange section 243 and feeds it into the urea synthesis facility 210. Therefore, when heating and vaporizing the liquid ammonia FL through heat exchange with liquid urea M, the heat of solidification, which is the thermal energy released when the liquid urea M solidifies, can be utilized. In this way, by using the heat of solidification released when liquid urea M undergoes a phase change to induce the phase change of liquid ammonia FL, the thermal energy of the liquid urea M, including its latent heat, can be effectively utilized without waste. Therefore, by effectively utilizing the waste heat generated when urea M, which is in liquid state and acts as a heat transfer medium, undergoes a phase change from a high-enthalpy phase (liquid) to a low-enthalpy phase (solid), it becomes possible to effectively supply the large amount of heat required when liquid ammonia FL, which is the input medium, undergoes a phase change from a low-enthalpy phase (liquid) to a high-enthalpy phase (gas).

[0059] (Other embodiments) Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure.

[0060] It should be noted that the input medium in this embodiment is not limited to ammonia; the input medium can be any medium that is introduced into the target engine, such as a gaseous fuel that drives a heat engine. In other words, the input medium may be a substance other than ammonia. Similarly, the heat transfer medium is not limited to exhaust gas EG or urea; it can be any medium that is discharged from the target engine and is at a higher temperature than the input medium. In other words, the heat transfer medium may be a substance other than exhaust gas EG or urea.

[0061] Furthermore, one form of "phase change" of the input medium in the above embodiment is "vaporization," 1) When heating an input medium at saturation temperature at a pressure below critical pressure (subcritical pressure), 2) When heating an input medium below the critical temperature at critical pressure to bring it above the critical temperature, 3) This includes cases where an input medium below a pseudocritical temperature is heated to a temperature above the pseudocritical temperature under supercritical pressure. In the case of heating the input medium under supercritical pressure as described in (3) above, the pseudocritical temperature is the temperature at which the specific heat at constant pressure is maximum.

[0062] Specifically, if the pressure of the input medium to be heated (e.g., liquid ammonia) is at the critical pressure, the input medium is heated from a temperature below the critical temperature (temperature at which the specific heat at constant pressure is maximum) to a temperature above the critical temperature. If the pressure of the input medium to be heated is higher than the critical pressure, the input medium is heated from a temperature below the pseudocritical temperature (temperature at which the specific heat at constant pressure is maximum) to a temperature above the pseudocritical temperature. If the pressure of the input medium to be heated is lower than the critical pressure, the input medium is heated from a temperature below the saturation temperature (temperature at which the specific heat at constant pressure is maximum) to a temperature above the saturation temperature. Therefore, the gas produced by vaporizing the input medium (for example, ammonia gas) includes a fluid in which, at critical pressure, the input medium, which is at a temperature below the critical temperature, reaches a temperature above the critical temperature; or, at supercritical pressure, the input medium, which is at a temperature below the pseudocritical temperature, reaches a temperature above the pseudocritical temperature; and, at subcritical pressure, the input medium, which is at a temperature below the saturation temperature, reaches a temperature above the saturation temperature.

[0063] Furthermore, "condensation," which is one form of "phase change" of the heat transfer medium in the above embodiment, 1) When cooling an input medium at saturation temperature at a pressure below critical pressure (subcritical pressure), 2) When using critical pressure to cool an input medium above critical temperature to below critical temperature, 3) This includes cases where an input medium above a pseudocritical temperature is cooled to below a pseudocritical temperature under supercritical pressure. In the case of heating the input medium under supercritical pressure as described in (3) above, the pseudocritical temperature is the temperature at which the specific heat at constant pressure is maximum.

[0064] Specifically, if the pressure of the heat transfer medium being cooled (e.g., gaseous ammonia) is at the critical pressure, the heat transfer medium is cooled from a temperature above the critical temperature (temperature at which the specific heat at constant pressure is maximized) to a temperature below the critical temperature. If the pressure of the heat transfer medium being cooled is higher than the critical pressure, the heat transfer medium is cooled from a temperature above the pseudocritical temperature (temperature at which the specific heat at constant pressure is maximized) to a temperature below the pseudocritical temperature. If the pressure of the heat transfer medium being cooled is lower than the critical pressure, the heat transfer medium is cooled from a temperature above the saturation temperature (temperature at which the specific heat at constant pressure is maximized) to a temperature below the saturation temperature. Therefore, the liquid produced by condensing a heat transfer medium (for example, liquid ammonia) includes a fluid in which, at critical pressure, a heat transfer medium at a temperature above the critical temperature becomes a fluid below the critical temperature, or, at supercritical pressure, a heat transfer medium at a temperature above the pseudocritical temperature becomes a fluid below the pseudocritical temperature, and at subcritical pressure, a heat transfer medium at a temperature above the saturation temperature becomes a fluid below the saturation temperature.

[0065] <Note> The heat engine system 100 described in each embodiment can be understood, for example, as follows:

[0066] (1) The heat engine system 100 according to the first embodiment includes a heat engine 110 driven by gas fuel FG to generate exhaust gas EG, a fuel heating line 140 that generates gas fuel FG by heating liquid fuel FL through heat exchange with the exhaust gas EG, a waste heat recovery boiler 141 that recovers waste heat from the exhaust gas EG, a liquid fuel supply unit 145 that supplies the liquid fuel FL to the fuel heating line 140, and a gas fuel compressor 148 that compresses the gas fuel FG generated in the fuel heating line 140 and supplies it to the heat engine 110, wherein at least a portion of the fuel heating line 140 is located in the waste heat recovery boiler 141 in a region below the dew point, which is a temperature region where the temperature of the exhaust gas EG passing through the waste heat recovery boiler 141 is below the dew point Pr of the water contained in the exhaust gas EG. Examples of heat engines 110 include gas turbines, reciprocating engines, and fuel cells. Examples of gaseous fuels (FG) and liquid fuels (FL) include ammonia, methanol, ethanol, and dimethyl ether.

[0067] As a result, the fuel heating line 140 is positioned in the dew point region 141a, which is the temperature range where the temperature of the exhaust gas EG passing through the waste heat recovery boiler 141 is below the dew point Pr of the water contained in the exhaust gas EG. Therefore, when heating the liquid fuel FL in the fuel heating line 140 by heat exchange with the exhaust gas EG, the latent heat, which is the thermal energy released when the water contained in the exhaust gas EG condenses, can be utilized. In this way, when heating the liquid fuel FL to change its phase and generate gaseous fuel FG, it is possible to utilize not only the sensible heat of the exhaust gas EG used in normal heat exchange, but also the latent heat released when the water contained in the exhaust gas EG condenses. This allows for the efficient and complete utilization of the thermal energy of the exhaust gas EG. In other words, it is possible to provide a heat engine system 100 that can effectively supply the large amount of heat required to change the phase of liquid ammonia FL, the input medium, from a low-enthalpy phase (liquid) to a high-enthalpy phase (gas), by effectively utilizing the waste heat generated when the water in the exhaust gas EG, which is the heat transfer medium, changes its phase from a high-enthalpy phase (gas) to a low-enthalpy phase (liquid).

[0068] (2) A heat engine system 100 according to a second embodiment is the heat engine system 100 of (1), wherein the liquid fuel supply unit 145 includes a liquid fuel compression unit 146 that compresses the liquid fuel FL supplied to the fuel heating line 140 in a range in which the saturation temperature of the liquid fuel FL is less than the dew point Pr of the water.

[0069] Therefore, when gas fuel FG is generated from liquid fuel FL in the fuel heating line 140, the latent heat of the water contained in the exhaust gas EG condenses and is not prevented from being utilized. As a result, the water in the exhaust gas EG condenses while heat exchange occurs between the exhaust gas EG and liquid ammonia FL, and the liquid ammonia FL can be vaporized. Therefore, the latent heat generated when the water in the exhaust gas EG condenses can be used to supply the large amount of heat necessary to vaporize the liquid ammonia FL. Furthermore, because the liquid fuel FL is pressurized, the gas fuel FG supplied from the fuel heating line 140 to the gas fuel compressor 148 is also pressurized. Therefore, the power required by the gas fuel compressor 148 to pressurize the gas fuel FG to the input pressure to the gas turbine 110 can be reduced. This reduces the installation cost of the gas fuel compressor 148.

[0070] (3) The heat engine system 100 according to the third embodiment is the heat engine system 100 of (1) or (2), wherein the waste heat recovery boiler 141 has an evaporator 143 that vaporizes the liquid fuel FL to produce the gas fuel FG by heat exchange with the exhaust gas EG and condenses the water contained in the exhaust gas EG, and the fuel heating line 140 heats the liquid fuel in the evaporator 143 to produce the gas fuel FG.

[0071] As a result, the liquid fuel FL is vaporized by the evaporator 143 to become gaseous fuel FG. At the same time, the water contained in the exhaust gas EG is condensed by the evaporator 143. In this way, by utilizing the evaporator 143 in the fuel heating line 140, a structure can be easily installed that generates gaseous fuel FG from liquid fuel FL using the latent heat of water contained in the exhaust gas EG.

[0072] (4) The heat engine system 100 according to the fourth embodiment is the heat engine system 100 of (3), wherein the waste heat recovery boiler 141 has a preheater 142 that heats the liquid fuel FL in a liquid state by heat exchange with the exhaust gas EG, which has been cooled by heat exchange with the liquid fuel FL in the evaporator 143, and the fuel heating line 140 heats the liquid fuel in the preheater 142 before it is heated in the evaporator 143.

[0073] This allows for further utilization of the thermal energy of the exhaust gas EG, which has undergone heat exchange with the liquid fuel FL to generate the gaseous fuel FG. Furthermore, the increase in the temperature of the liquid fuel FL in the preheater 142 reduces the thermal energy required to vaporize the liquid fuel FL in the evaporator 143. Therefore, the heat exchange efficiency during the phase change of the liquid fuel FL can be further improved.

[0074] (5) The fifth heat engine system 100 is the heat engine system 100 of (3) or (4), wherein the waste heat recovery boiler 141 has a superheater 144 that raises the temperature of the gas fuel FG by heat exchange with the exhaust gas EG supplied to the evaporator 143, and the fuel heating line 140 heats the gas fuel generated in the evaporator 143 with the superheater 144.

[0075] This allows thermal energy to be obtained from the exhaust gas EG before it is supplied to the evaporator 143, thereby increasing the temperature of the gas fuel FG produced in the evaporator 143. Heat exchange with the gas fuel FG in the superheater 144 lowers the temperature of the exhaust gas EG supplied to the evaporator 143. This prevents the temperature of the exhaust gas EG supplied to the evaporator 143 from becoming excessively high, making it easier to achieve the dew point region 141a within the waste heat recovery boiler 141, which is the temperature range where the temperature of the exhaust gas EG is below the dew point Pr of the water contained in the exhaust gas EG. Furthermore, the temperature of the gas fuel FG supplied from the fuel heating line 140 to the gas fuel compressor 148 is higher. As a result, the temperature of the ammonia gas FG at the outlet of the gas fuel compressor 148, i.e., at the inlet of the combustor 113, also increases. Consequently, the amount of heat contained in the ammonia gas FG fed into the combustor 113 increases, and the consumption of the fuel ammonia gas FG can be reduced. Therefore, the efficiency of the heat engine system 100 can be increased.

[0076] (6) The heat engine system 100 according to the sixth embodiment is any one of the heat engine systems 100 of (1) to (5), wherein the heat engine 110 is a gas turbine 110, and further comprises a steam turbine 120 driven by steam generated by the waste heat recovered by the waste heat recovery boiler 141, and the fuel heating line 140 heats the liquid fuel by heat exchange with the exhaust gas EG after the steam has been generated.

[0077] This method utilizes the waste heat from the exhaust gas EG, whose temperature has been reduced by its use in steam generation, to produce gaseous fuel FG. By using the thermal energy of the exhaust gas EG to generate steam and gaseous fuel FG in this way, the thermal energy of the exhaust gas EG can be used effectively without waste.

[0078] (7) The seventh embodiment of the heat engine system 100 is a heat engine system 100, 200 that heats and changes the phase of an input medium FL before it is fed into the target engines 110, 210, and comprises heat exchange units 143, 243 that cause a phase change of the heat transfer mediums EG, M and the input medium FL by exchanging heat between the input medium FL and the heat transfer mediums EG, M discharged from the target engines 110, 210 and at a higher temperature than the input medium FL, and input medium compression units 148, 249 that compress the input medium FL that has undergone a phase change in the heat exchange units 143, 243 and supply it to the target engines 110, 210.

[0079] This allows for the efficient and complete utilization of the thermal energy of the heat transfer fluids EG and M by using the thermal energy generated during the phase change of the heat transfer fluid FL to change its phase. Consequently, the waste heat generated during the phase change of the heat transfer fluids EG and M from a high-enthalpy phase to a low-enthalpy phase can be effectively used to supply the large amount of heat required to change the phase of the heat transfer fluid FL from a low-enthalpy phase to a high-enthalpy phase. Examples of input media include ammonia, methanol, ethanol, and dimethyl ether. Examples of heat transfer fluids include water contained in exhaust gases and urea. The types of equipment that can be used include gas turbines, reciprocating engines, fuel cells, and chemical synthesis equipment. [Explanation of symbols]

[0080] 100… Heat engine system 110... Gas turbine (heat engine, target engine) 112... Air compressor 113... Combustor 114... Turbine 115... Gas turbine rotor 117... Generator 120... Steam turbine 121... High-pressure steam turbine 122...Medium-pressure steam turbine 123... Low-pressure steam turbine 124... Steam turbine rotor 125...Condenser 127...Water supply pump 128... Generator 130... Waste heat recovery boiler (heat exchange section) 131...First waste heat recovery boiler 132... Low-pressure carbon saver 133... Low-pressure evaporator 134... High-pressure pump 135... Low-pressure superheater 136... High-pressure economizer 137... High-pressure evaporator 138... High-pressure superheater 140…Fuel heating line 141... Second waste heat recovery boiler 141a...Area below the dew point 142… Preheater 143... Evaporator (heat exchange section) 144...Superheater 145...Liquid fuel supply section 146...Liquid fuel compression section 147…Gas fuel supply line 148... Gas fuel compressor (input medium compression section) 150... Chimney 200… Heat engine systems 210… Institutions to be deployed 243...First heat exchange section (heat exchange section) 245...Second heat exchange section 247...First Compression Section 248...Second Compression Section 249...Gas compression section (input medium compression section) CG…Carbon dioxide gas CL…Liquid carbon dioxide EG... Exhaust gas (heat transfer medium) FG... Ammonia gas (gas fuel) FL...Liquid ammonia (liquid fuel, input medium) M…Urea Pr…Dew point

Claims

1. A heat engine that is driven by gaseous fuel and produces exhaust gas, A fuel heating line is provided to generate the gaseous fuel by heating the liquid fuel through heat exchange with the exhaust gas, and a heat recovery boiler is provided to recover the exhaust heat from the exhaust gas. A liquid fuel supply unit that supplies the liquid fuel to the fuel heating line, The system includes a gas fuel compressor that compresses the gaseous fuel generated in the fuel heating line and supplies it to the heat engine, At least a portion of the fuel heating line is located in the below-dew point region of the waste heat recovery boiler, where the temperature of the exhaust gas passing through the waste heat recovery boiler is below the dew point of the water contained in the exhaust gas. The liquid fuel supply unit includes a liquid fuel compression unit that compresses the liquid fuel supplied to the fuel heating line in a range where the saturation temperature of the liquid fuel is below the dew point of the water, A heat engine system further comprising a gas fuel supply line that connects the fuel heating line and the gas fuel compressor, and supplies the gas fuel generated by vaporizing the liquid fuel in the fuel heating line to the gas fuel compressor.

2. The aforementioned heat recovery boiler has an evaporator that vaporizes the liquid fuel to produce the gaseous fuel by heat exchange with the exhaust gas, and condenses the moisture contained in the exhaust gas. The heat engine system according to claim 1, wherein the fuel heating line heats the liquid fuel in the evaporator to produce the gaseous fuel.

3. The aforementioned heat recovery boiler has a preheater that heats the liquid fuel while it remains in a liquid state by exchanging heat with the exhaust gas, whose temperature has been lowered by heat exchange with the liquid fuel in the evaporator. The heat engine system according to claim 2, wherein the fuel heating line heats the liquid fuel in the preheater before heating it in the evaporator.

4. The aforementioned waste heat recovery boiler has a superheater that raises the temperature of the gas fuel by heat exchange with the exhaust gas supplied to the evaporator, The heat engine system according to claim 2 or 3, wherein the fuel heating line heats the gaseous fuel generated in the evaporator in the superheater.

5. The heat engine in question is a gas turbine, The boiler further comprises a steam turbine driven by steam generated from the waste heat recovered by the aforementioned waste heat recovery boiler. The heat engine system according to claim 1, wherein the fuel heating line heats the liquid fuel by heat exchange with the exhaust gas after generating the steam.

6. A heat engine system that heats the input medium before it is introduced into the target engine to cause a phase change, A heat exchange unit that causes a phase change in the heat medium and the input medium by exchanging heat between the input medium and a heat medium discharged from the input machine, which is at a higher temperature than the input medium, A feed medium compression unit compresses the feed medium that has undergone a phase change in the heat exchange unit and supplies it to the target engine, A heat engine system comprising: a liquid input medium compression unit that compresses the input medium, which is a liquid, to a pressure lower than the pressure at which the saturation temperature or pseudocritical temperature of the input medium becomes the temperature at which the heat medium supplied to the heat exchange unit undergoes a phase change.

7. A heat engine driven by gaseous fuel to generate exhaust gas, A fuel heating line has a fuel heating line that generates gaseous fuel by heating the liquid fuel through heat exchange with the exhaust gas, and a waste heat recovery boiler that recovers the waste heat from the exhaust gas, and a liquid fuel supply unit that supplies the liquid fuel to the fuel heating line, The system includes a gas fuel compressor that compresses the gaseous fuel generated in the fuel heating line and supplies it to the heat engine, At least a portion of the fuel heating line is located in the below-dew point region of the waste heat recovery boiler, where the temperature of the exhaust gas passing through the waste heat recovery boiler is below the dew point of the water contained in the exhaust gas. The aforementioned heat recovery boiler has an evaporator that vaporizes the liquid fuel to produce the gaseous fuel by heat exchange with the exhaust gas, and condenses the moisture contained in the exhaust gas. The fuel heating line generates gaseous fuel by heating the liquid fuel in the evaporator, and generates steam using the waste heat recovered in the waste heat recovery boiler. The fuel heating line is a heat engine system that heats the liquid fuel by heat exchange with the exhaust gas after generating the steam.

8. The liquid fuel has a lower boiling point than water. The heat engine system according to claim 7.

9. The liquid fuel is one of ammonia, methanol, ethanol, or dimethyl ether. The heat engine system according to claim 8.

10. A heat engine driven by gaseous fuel to generate exhaust gas, A fuel heating line has a fuel heating line that generates gaseous fuel by heating the liquid fuel through heat exchange with the exhaust gas, and a waste heat recovery boiler that recovers the waste heat from the exhaust gas, and a liquid fuel supply unit that supplies the liquid fuel to the fuel heating line, The system includes a gas fuel compressor that compresses the gaseous fuel generated in the fuel heating line and supplies it to the heat engine, At least a portion of the fuel heating line is located in the below-dew point region of the waste heat recovery boiler, where the temperature of the exhaust gas passing through the waste heat recovery boiler is below the dew point of the water contained in the exhaust gas. The aforementioned heat recovery boiler has an evaporator that vaporizes the liquid fuel to produce the gaseous fuel by heat exchange with the exhaust gas, and condenses the moisture contained in the exhaust gas. The fuel heating line generates gaseous fuel by heating the liquid fuel in the evaporator, and generates steam using the waste heat recovered in the waste heat recovery boiler. The fuel heating line heats the liquid fuel by heat exchange with the exhaust gas after generating the steam. The aforementioned waste heat recovery boiler comprises a low-pressure evaporator and a high-pressure evaporator. In the heat recovery boiler, the exhaust gas flows in the order of the low-pressure evaporator, the high-pressure evaporator, and so on, from downstream to upstream. The low-pressure evaporator and the high-pressure evaporator each convert water into water vapor, The evaporator is located downstream of the low-pressure evaporator in the direction of the exhaust gas flow in the heat engine system.

11. The waste heat recovery boiler further comprises a low-pressure economizer for heating water, The low-pressure evaporator converts the water heated in the low-pressure economizer into steam, In the direction of the exhaust gas flow, the low-pressure economizer and the low-pressure evaporator are arranged in that order from downstream to upstream. The evaporator is positioned downstream of the low-pressure economizer in the direction in which the exhaust gas flows. The heat engine system according to claim 10.

12. The liquid fuel has a lower boiling point than water. The heat engine system according to claim 10 or 11.

13. The liquid fuel is any of ammonia, methanol, ethanol, or dimethyl ether. The heat engine system according to claim 12.

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