System and method for storing and burning ammonia safely

Abstract

To provide a system capable of storing ammonia safely and supply it to a combustor, and capable of efficiently burning the ammonia to reduce a nitrogen oxide generated in the combustion.SOLUTION: A system and method for safely storing and burning ammonia, comprises: a device that suctions vaporized ammonia in an ammonia tank and a pipe and keeps a pressure in the tank and the pipe below the atmospheric pressure, to prevent ammonia from leaking from the tank and the pipe to the outside, including the atmosphere, and to reduce a nitrogen oxide generated during combustion by keeping the pressure in the tank and the pipe lower than the atmospheric pressure; a device that compresses the suctioned, vaporized ammonia to increase the temperature and pressure, and supplies it to a nitrogen oxide reduction device (SCR) installed in an exhaust pipe; a device that lowers a temperature of gaseous ammonia whose temperature and pressure have been increased through compression, to condense and liquefy the ammonia; and a device that returns the liquefied ammonia to the tank.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a system and method comprising an apparatus for safely supplying ammonia having toxicity stored in a tank to a diesel engine, a boiler, and a gas turbine, effectively and efficiently combusting the ammonia in a combustion chamber, and reducing nitrogen oxides generated during combustion.

Background Art

[0002] From the perspective that the combustion of fossil fuels containing a large amount of carbon component (C) promotes global warming, hydrogen and ammonia have attracted attention as fuels that do not contain a carbon component. Although hydrogen has many problems to be solved in terms of storage and transportation, ammonia is mainly used as a raw material for fertilizers, and technologies related to production, transportation, and storage have already been established and are distributed globally. Therefore, research has been conducted on utilizing ammonia as a fuel for diesel engines, boilers, and gas turbines. However, ammonia is toxic, and compared with fossil fuels, which are the main fuels of current diesel engines, boilers, and gas turbines, it has problems to be solved regarding combustion, such as poor ignitability, slow combustion speed, and a high possibility of generating nitrogen oxides (NOx), which are other air pollutants during combustion. In addition, it has a physical characteristic that the calorific value per unit mass (volume) is extremely small (about one-quarter of petroleum-based fuels). Therefore, many technical problems need to be overcome to make it usable as a fuel for diesel engines, boilers, and gas turbines.

[0003] For example, Patent Document 1 describes "a technique related to a diesel engine that forms a premixed ammonia mixture in a combustion chamber and combusts it by mixing, having fuel injection means for injecting fuel oil serving as an ignition source and gaseous ammonia into the combustion chamber in order to increase the combustion rate of ammonia and reduce unburned ammonia, thereby achieving CO2 reduction." Patent Document 2 describes a technique in which, in order to efficiently burn ammonia in an ammonia combustion engine, ammonia gas decomposed using an ammonia decomposition catalyst is adjusted so that the equivalent ratio of hydrogen contained in the ammonia decomposition gas is equal to or higher than a predetermined lower limit value, and then provided to a sub-combustion chamber communicated with a main combustion chamber through an ejection hole, ignited and burned under fuel-rich conditions, and a combustible gas mixed with unburned hydrogen is ejected from the ejection hole as a jet torch flame into the main combustion chamber, and the ammonia and air premixed gas supplied to the main combustion chamber is ignited and burned by the combustion of the unburned hydrogen by the jet torch flame. Patent Document 3 describes a technique in which, in an internal combustion engine using ammonia as fuel, since part of the ammonia supplied to the combustion chamber may be discharged without being burned in the combustion chamber and NOx may be generated along with the combustion of the air-fuel mixture in the combustion chamber, an aftertreatment device is used to effectively purify the unburned ammonia and NOx contained in the exhaust gas discharged from the combustion chamber.

[0004] However, none of these techniques address the fundamental problems that "ammonia is toxic and has poor ignitability and a slow combustion rate compared to fossil fuels, which are the main fuels of current diesel engines, boilers, and gas turbines."

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] Ammonia (NH3) does not contain a carbon component (C), so it is regarded as a fuel that does not emit CO2 during combustion (oxidation reaction). However, when comparing the combustion-related characteristics such as flammability, combustion rate, and the possibility of generating a large amount of NOx, which is an air pollutant during combustion, with petroleum-based fuels, it is toxic and has poor flammability, a slow combustion rate, and a high possibility of generating nitrogen oxides (NOx), which are other air pollutants during combustion, compared to fossil fuels, which are the main fuels of current diesel engines, boilers, and gas turbines. In addition, it has a physical characteristic that the calorific value per unit mass (volume) is extremely small (about one-quarter of petroleum-based fuels), so there are many technical issues to be improved. As a result of this, since the calorific value per unit mass is significantly less, about 40% (one-quarter) of petroleum-based fuels (light oil and A heavy oil), in order to obtain the same performance (output) in a diesel engine or boiler, a fuel tank and fuel injection device about 2.5 times larger are required.

[0007] Therefore, the present invention provides a system that can be applied to combustion devices of existing diesel engines, boilers, and gas turbines, which has the following elements, safely stores and transports ammonia in a tank, improves the combustion of ammonia in the combustion devices of diesel engines, boilers, and gas turbines, and reduces nitrogen oxides (NOx) contained in the exhaust gas. 1. In the tank and piping for storing and transporting ammonia installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel, by setting the pressure inside the ammonia tank and piping to a value lower than atmospheric pressure, leakage of ammonia from the tank and piping to the outside including the atmosphere is prevented. 2. By using the heat of vaporization when ammonia evaporates to lower the temperature of ammonia itself, it is possible to keep ammonia in a liquefied state even when the pressure inside the ammonia tank and piping is set to a value lower than atmospheric pressure. 3. A system composed of a device that sucks vaporized ammonia inside an ammonia tank and piping to keep the pressure inside the ammonia tank and piping below atmospheric pressure, a device that compresses the sucked vaporized ammonia to increase the temperature and pressure, a device that condenses and liquefies the gaseous ammonia whose temperature and pressure have increased after compression by lowering its temperature, and a device that returns the liquefied ammonia to the ammonia tank is provided with a structure and function to keep ammonia in a liquefied state even when the pressure inside the ammonia tank and piping is lower than atmospheric pressure. 4. In a combustion device installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel, by setting the co-firing rate of petroleum-based fuel supplied from an auxiliary fuel tank to zero, the combustion of ammonia is improved using electrical energy supplied from a device that supplies electrical energy in order to make the CO2 emissions from the diesel engine, boiler, or gas turbine that uses ammonia as fuel zero. 5. By making the outer periphery of a tank and piping for storing and transporting ammonia a sealed double structure with a vacuum inside and installing an ammonia leakage detection device inside the double structure, it is possible to prevent release to the outside including the atmosphere and to quickly respond by knowing the leakage in real time with the ammonia leakage detector. 6. By installing a vacuum insulation device on the entire circumference or a part of the periphery of a tank for storing ammonia to form a sealed structure and installing valves at multiple locations in the sealed space formed between the tank and the vacuum insulation device, it becomes possible to keep the temperature inside the tank low when all the valves are closed, and when the valves are opened and a fluid at a temperature higher than the boiling point of the ammonia stored in the tank is made to flow, it becomes possible to promote the vaporization of the ammonia stored in the tank. 7. By sucking and compressing the vaporized ammonia inside the ammonia tank and piping to increase the temperature and pressure and supplying it to a nitrogen oxide reduction device (SCR) installed in the exhaust pipe, it is possible to reduce nitrogen oxides (NOx) generated by the combustion of ammonia. 8. With the pump (ammonia supply pump) for supplying ammonia to the combustion devices of diesel engines, boilers, and gas turbines in operation, by adjusting the opening degree of the supply source valve of the ammonia storage tank, the pressure inside the ammonia supply system from the ammonia storage tank to the ammonia supply pump is maintained at a value lower than atmospheric pressure, it becomes possible to prevent leakage from the ammonia supply system. 9. In the ammonia supply system, a part of the portion where the internal pressure becomes higher than atmospheric pressure is covered with a container and made airtight, and a part of it is sucked by a blower, and a heat exchanger capable of setting the temperature of the gas in the sucked airtight container to an arbitrary value is provided, and an ammonia concentration meter is installed between the blower and the heat exchanger, so that even if ammonia leaks from the airtight ammonia supply system, it is ensured that it will not be released to the outside, and when ammonia leaks, it becomes possible to detect it promptly.

Means for Solving the Problems

[0008] Ammonia not only has problems to be solved regarding combustion such as being toxic, having poor ignitability, having a slow combustion rate, and having a high possibility of generating nitrogen oxides (NOx), which are other air pollutants during combustion, compared to fossil fuels, which are the main fuels of current diesel engines, boilers, and gas turbines, but also has a physical property that the calorific value per unit mass (volume) is extremely small (about one - quarter of petroleum - based fuels). Also, since there is a possibility of generating a large amount of nitrogen oxides (NOx) during combustion, it is necessary to develop corresponding technologies. In order to solve these problems, the present invention provides the following system.

[0009] The invention according to claim 1 is characterized in that, in a diesel engine, a boiler, or a gas turbine using ammonia as fuel, in a tank and piping for storing and transferring ammonia installed therein, a device is installed to make the pressure inside the ammonia tank and piping lower than the atmospheric pressure in order to prevent ammonia from leaking from the tank and piping to the outside including the atmosphere.

[0010] The invention according to claim 2 is characterized in that, in a diesel engine, a boiler, or a gas turbine using ammonia as fuel, in a tank and piping for storing and transferring ammonia installed therein, a method is used to make the pressure inside the ammonia tank and piping lower than the atmospheric pressure in order to prevent ammonia from leaking from the tank and piping to the outside including the atmosphere.

[0011] The invention according to claim 3 is characterized in that a device is installed to keep ammonia in a liquefied state even when the pressure inside the ammonia tank and piping is made lower than the atmospheric pressure by using the heat of vaporization when ammonia evaporates to lower the temperature of ammonia itself.

[0012] The invention according to claim 4 is characterized in that a method is used to lower the temperature of ammonia itself by using the heat of vaporization when ammonia evaporates so that ammonia can be kept in a liquefied state even when the pressure inside the ammonia tank and piping is made lower than the atmospheric pressure.

[0013] The invention according to claim 5 is characterized in that in a diesel engine, boiler, or gas turbine using ammonia as fuel, in a tank and piping for storing and transferring ammonia installed therein, in order to prevent ammonia from leaking from the tank and piping to the outside including the atmosphere by setting the pressure inside the ammonia tank and piping to a value lower than atmospheric pressure, there is installed a device for sucking the vaporized ammonia inside the ammonia tank and piping to keep the pressure inside the ammonia tank and piping below atmospheric pressure, a device for compressing the sucked vaporized ammonia to increase the temperature and pressure, a device for condensing and liquefying the gaseous ammonia whose temperature and pressure have increased after compression by lowering the temperature, and a device for returning the liquefied ammonia to the ammonia tank.

[0014] The invention according to claim 6 is characterized in that in a diesel engine, boiler, or gas turbine using ammonia as fuel, in a tank and piping for storing and transferring ammonia installed therein, by using the method of installing a device for sucking the vaporized ammonia inside the ammonia tank and piping to keep the pressure inside the ammonia tank and piping below atmospheric pressure, a device for compressing the sucked vaporized ammonia to increase the temperature and pressure, a device for condensing and liquefying the gaseous ammonia whose temperature and pressure have increased after compression by lowering the temperature, and a device for returning the liquefied ammonia to the ammonia tank, and setting the pressure inside the ammonia tank and piping to a value lower than atmospheric pressure, it is possible to prevent ammonia from leaking from the tank and piping to the outside including the atmosphere.

[0015] The invention according to claim 7 is characterized in that when cracks, holes or gaps occur at joints in a tank for storing ammonia or a pipe for supplying ammonia and air flows in, due to the density differences among liquid ammonia, vaporized ammonia, and the inflowing outside air (air) in the tank, layers of vaporized ammonia, inflowing air, and liquefied ammonia are formed in this order from the upper part of the tank inside the tank. By using this characteristic, a system is provided that can detect cracks, holes or gaps generated at joints in a tank for storing ammonia or a pipe for supplying ammonia by means of an oxygen concentration sensor installed near the liquid level inside the ammonia tank.

[0016] The invention according to claim 8 is characterized in that outside air flowing in from cracks, holes or gaps at joints in a pipe for supplying ammonia stays in the middle between the liquid ammonia at the lower part of the tank and the gaseous ammonia at the upper part of the tank inside the tank due to its density difference. By using this characteristic, an apparatus is provided that continuously sucks in the outside air flowing into the ammonia storage and supply system and continuously discharges it into the atmosphere as it is or after some post-treatment.

[0017] The invention according to claim 9 is characterized in that in a combustion device installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel, in order to make the CO2 emissions from the diesel engine, boiler, or gas turbine that uses ammonia as fuel zero by setting the co-firing rate of the fuel containing carbon (C) supplied from an auxiliary fuel tank to zero, a device for improving the combustion of ammonia is installed using the electrical energy supplied from a device for supplying electrical energy.

[0018] The invention according to claim 10 is characterized in that, in a combustion device installed in a diesel engine, a boiler, or a gas turbine that uses ammonia as fuel, by using a method of improving the combustion of ammonia using electrical energy supplied from a device that supplies electrical energy and reducing the co-combustion rate of a fuel containing carbon (C) supplied from an auxiliary fuel tank to zero, it is possible to make the CO2 emissions from the diesel engine, boiler, or gas turbine that uses ammonia as fuel zero.

[0019] The invention according to claim 11 is characterized in that a vacuum insulation device is installed on the entire circumference or a part of the periphery of a tank for storing ammonia to form a sealed structure, and valves are installed at a plurality of locations in the sealed space formed between the tank and the vacuum insulation device. When all the valves are closed and the vacuum insulation device is operated, the temperature inside the tank can be kept low, and when some of the valves are opened and a fluid at a temperature higher than the boiling point of the ammonia stored in the tank is allowed to flow, it is possible to promote the vaporization of the ammonia stored in the tank.

[0020] Note that the invention according to claim 11 can also be applied to a method of safely storing and burning ammonia, which is "by using a method of installing a vacuum insulation device on the entire circumference or a part of the periphery of a tank for storing ammonia to form a sealed structure and installing valves at a plurality of locations in the sealed space formed between the tank and the vacuum insulation device, when all the valves are closed and the vacuum insulation device is operated, the temperature inside the tank can be kept low, and when some of the valves are opened and a fluid at a temperature higher than the boiling point of the ammonia stored in the tank is allowed to flow, it is possible to promote the vaporization of the ammonia stored in the tank."

[0021] The invention according to claim 12 is characterized in that, in order to reduce nitrogen oxides (NOx) generated by the combustion of ammonia, it is equipped with a device for sucking and compressing the vaporized ammonia inside the ammonia tank and the piping to increase the temperature and pressure, and supplying it to a nitrogen oxide reduction device (SCR) installed in the exhaust pipe.

[0022] In addition, the invention according to claim 12 can also be applied to a method of safely storing and burning ammonia, which is "by sucking and compressing the vaporized ammonia inside the ammonia tank and the pipes to increase the temperature and pressure, and supplying it to the nitrogen oxide reduction device (SCR) installed in the exhaust pipe, it becomes possible to reduce the nitrogen oxides (NOx) generated by the combustion of ammonia."

[0023] The invention according to claim 13 is characterized by comprising a device that, in order to prevent leakage from the ammonia supply system, while operating a pump (ammonia supply pump) for supplying ammonia to the combustion devices of a diesel engine, a boiler, and a gas turbine, adjusts the opening degrees of the supply source valve of the ammonia storage tank and the pressure regulating valve installed on the discharge side of the ammonia supply pump, and maintains the pressure inside the ammonia supply system from the ammonia storage tank to the ammonia supply pump at a value lower than atmospheric pressure.

[0024] In addition, the invention according to claim 13 can also be applied to a system for safely storing and burning ammonia, which is "by using the method of adjusting the opening degrees of the supply source valve of the ammonia storage tank and the pressure regulating valve installed on the discharge side of the ammonia supply pump while operating a pump (ammonia supply pump) for supplying ammonia to the combustion devices of a diesel engine, a boiler, and a gas turbine, and maintaining the pressure inside the ammonia supply system from the ammonia storage tank to the ammonia supply pump at a value lower than atmospheric pressure, it becomes possible to prevent leakage from the ammonia supply system."

[0025] In the invention according to claim 14, in the ammonia supply system, when the internal pressure becomes higher than the atmospheric pressure, even if ammonia leaks from the ammonia supply system, it is ensured that the ammonia is not released to the outside, and when ammonia leaks, it is possible to quickly detect it. A part where the internal pressure is higher than the atmospheric pressure is covered with a container and the inside is made airtight, and a part of it is sucked by a blower, and a heat exchanger capable of setting the temperature of the gas in the sucked airtight container to an arbitrary value is provided, and an ammonia concentration meter is installed between the blower and the heat exchanger.

[0026] Note that the invention according to claim 14 is also applicable to a method of safely storing and burning ammonia, which is "in the ammonia supply system, a part where the internal pressure is higher than the atmospheric pressure is covered with a container and the inside is made airtight, and a part of it is sucked by a blower, and a heat exchanger capable of setting the temperature of the gas in the sucked airtight container to an arbitrary value is provided, and an ammonia concentration meter is installed between the blower and the heat exchanger. By using this method, when the internal pressure of the ammonia supply system becomes higher than the atmospheric pressure, even if ammonia leaks from the ammonia supply system, it is ensured that the ammonia is not released to the outside, and when ammonia leaks, it is possible to quickly detect it."

Effects of the Invention

[0027] By using the present invention, in a diesel engine, a boiler, and a gas turbine using ammonia as fuel, it becomes possible to safely store and transfer ammonia and efficiently burn it in a combustion device, and it also becomes possible to reduce NOx generated by the combustion of ammonia in a NOx reduction device installed in the exhaust pipe.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0029] First, the outline of this system will be described with reference to FIG. 1. In FIG. 1, ammonia stored in the ammonia storage tank (1) reaches the ammonia supply tank (2) through the ammonia supply source valve "V-1". In the ammonia supply tank (2), there is a device (3) that sucks vaporized ammonia to make the pressure inside the ammonia tank (1) and / or (2) and the piping lower than atmospheric pressure, and compresses the sucked ammonia to increase the temperature and pressure, and a device (4) that cools and condenses the ammonia with increased temperature and pressure. Also, the gaseous ammonia with increased temperature and pressure discharged from the device (3) is utilized as a reducing agent in the NOx reduction device (5) through the flow rate adjustment valve "V-2". The ammonia in the ammonia supply tank (2) is supplied to the combustion device (7) installed in the diesel engine, boiler, and gas turbine by the ammonia supply pump (6), and is injected into the combustion chambers (8) of the diesel engine, boiler, and gas turbine. In FIG. 1, the space including the devices (3), (4), pump (6) and device (7) enclosed by the dashed line is a closed and sealed space. In this sealed space, a blower (9), an ammonia detector (10), and a heat exchanger (11) are installed. The gas in the sealed space is sucked by the blower (9) and repeats a closed-loop circulation of returning through the ammonia detector (10) and the heat exchanger (11), thereby enabling temperature control of the gas in the sealed space and confirmation of its properties (presence or absence of ammonia leakage).

[0030] Next, by keeping the pressure in the ammonia tank and the supply system lower than atmospheric pressure, A device and method for preventing ammonia from leaking outside the storage and transfer system due to perforations, cracks, looseness, etc. in the gaskets installed in the joints and valves installed in the tank and pipes will be described. In the ammonia supply tank (2), ammonia is supplied from the ammonia storage tank (1) so that the liquid level of the liquid ammonia becomes constant. At the same time, the vaporized ammonia is sucked using the device (3) so that the pressure in the pipe from the ammonia storage tank (1) to the ammonia supply pump (6) becomes lower than atmospheric pressure. As a result, the temperature of the liquid ammonia becomes lower than about -33.34°C, which is the boiling point under atmospheric pressure. In such a state, if a part of it evaporates due to heat input from the outside, the temperature of the liquid ammonia itself decreases due to the heat of vaporization. Therefore, by inhaling the vaporized ammonia with the device (3), condensing it with the device (4), and returning it to the tank (2), a stable state can be maintained. In this way, by using the device (3) to keep the pressure in the ammonia storage and supply system from the ammonia storage tank (1) to the ammonia supply pump below atmospheric pressure, In the case where ammonia leaks due to perforations, cracks, looseness, etc. in the gaskets installed in the joints and valves installed in the tanks and pipes of the ammonia storage and supply system, outside air (air) can be inhaled from that location to avoid a situation where ammonia leaks to the outside.

[0031] When using devices (3) and (4) installed in the tank (2) to keep the pressure in the ammonia tank and supply system lower than atmospheric pressure, power is required to operate devices (3) and (4). However, a method of keeping the pressure in the ammonia tank and supply system lower than atmospheric pressure using the system shown in Fig. 1 without operating these devices will be described. In Fig. 1, the ammonia supplied to the combustion device is inhaled from the ammonia storage tank (1) through the ammonia supply source valve V-1 and the ammonia supply tank (2) to the ammonia supply pump (6). Due to the pipeline resistance of these supply systems, it is usually lower than atmospheric pressure. On the other hand, the discharge pressure of the pump (6) requires a high pressure (for example, about 2 MPa, which is the saturated vapor pressure at 50°C) that does not vaporize even when the temperature of ammonia is increased in the combustion device. For this reason, in this system, a branch pipe connected to the suction side of the pump (6) is provided in the middle of the pipe connecting the pump (6) and the combustion device (7), and a pressure regulating valve is installed in the middle. Thus, ammonia can be supplied to the combustion device (7) at a stable pressure. In this system, by reducing the opening degree of the ammonia supply source valve, the pressure in the ammonia supply system from the ammonia supply source valve to the pump (6) is set to a value lower than atmospheric pressure, and by reducing the opening degree of the pressure regulating valve V-3, the pressure and supply amount of ammonia supplied to the combustion device (7) are maintained. During the operation of the ammonia supply pump (6), even without operating the devices (3) and (4) installed in the tank (2), the pressure in the pipe from the ammonia storage tank (1) to the ammonia supply pump (6) is made lower than atmospheric pressure, preventing ammonia from leaking due to causes such as perforation, cracking, and loosening of the packing installed in the joints and valves installed in the tank and pipes.

[0032] Fig. 2 shows an example of the basic configuration according to an embodiment of the present invention. In the figure, ammonia exiting from the tank (2) that supplies ammonia reaches the combustion device (7) of a diesel engine, a boiler, and a gas turbine via a pipe that transfers ammonia. Since ammonia has combustion characteristics such as poor ignitability and a slow combustion rate compared to fossil fuels, which are the main fuels of current diesel engines, boilers, and gas turbines, in the combustion device (7), fuels such as light oil, heavy oil, and LNG transferred from the tank (12) that stores petroleum-based fuel, which serves as an auxiliary fuel for ammonia, are mixed, injected in a stratified manner, or independently injected, making it possible to improve the ignitability and combustion rate of ammonia. At this time, whether the ammonia injected in the combustion device (7 ) is in a liquid state or a gaseous state is determined by the form of the combustion device having a structure and function to improve combustion by mixing, injecting in a stratified manner, or independently injecting petroleum-based fuel.

[0033] The object of the present invention is to contribute to preventing global warming by providing a system and method for safely supplying ammonia, a fuel that does not contain a carbon component, to a diesel engine, a boiler, and a gas turbine, effectively and efficiently burning it in a combustion chamber, and reducing nitrogen oxides generated during combustion. However, since fuels such as light oil, heavy oil, and LNG, which serve as auxiliary fuels for ammonia, contain carbon, it becomes a technical issue to minimize the co-combustion rate of these fuels as much as possible, but it is difficult to make it zero. To solve this issue, in the present invention, an apparatus and method for improving the ignition and combustion characteristics of ammonia using electrical energy are used to make the emissions of GHG (greenhouse gas) zero.

[0034] The electricity transmitted from the device (12) that supplies electrical energy forms a high-temperature region by means of a discharge device installed in the combustion device (7) and / or a heating device, and helps the combustion of ammonia, thereby making it possible to improve the combustion characteristics of ammonia, such as poor ignitability and slow combustion speed. In addition, by generating electricity using renewable energy, ammonia that does not generate GHG, a diesel engine equipped with a combustion device that uses only hydrogen as fuel, a boiler, or a gas turbine to supply the electricity to the device (12) that supplies electrical energy, it is also possible to reduce the GHG emissions of the entire system to zero.

[0035] When using ammonia as fuel, it is necessary to solve the problems in combustion characteristics such as poor ignitability and slow combustion speed compared to fossil fuels, which are the main fuels of current diesel engines, boilers, and gas turbines. However, ensuring safety during the storage and transportation of ammonia is also an important issue. Since the boiling point of ammonia under atmospheric pressure is approximately -33°C, in order to transport and store it in a liquid state with high energy density, it is necessary to keep the temperature below that under atmospheric pressure. Also, in order to maintain the liquid state at atmospheric temperature, high pressures are required, such as 0.43 MPa at 0°C, 0.86 MPa at 20°C, and 1.55 MPa at 40°C. Therefore, when using liquid ammonia as fuel for a diesel engine, boiler, or gas turbine, a heat-insulated low-temperature storage container and fuel supply system, or a pressurized storage container and fuel supply system are required.

[0036] Since the boiling point of ammonia under atmospheric pressure is approximately -33°C, when stored under pressure, if cracks, holes, or leaks occur at the joints in the tanks storing ammonia or the pipes supplying ammonia, the ammonia will vaporize and jet out in a gaseous state. The molecular weight of vaporized ammonia (NH3) is 17, which is lighter than the molecular weight of air, approximately 29, so it will move upward in the atmosphere. Therefore, if the installation location of the equipment for storing and transporting ammonia is outdoors, the safety issues are reduced. However, if it is installed indoors, especially at the bottom of a confined space such as a ship, it will spread throughout the entire confined space (engine room), and ammonia will continue to jet out from the bottom, so there is a high possibility of a major disaster.

[0037] In contrast, although the heat of vaporization (latent heat of evaporation) of ammonia is approximately 1370 kJ / kg, which is less than that of water, approximately 2250 kJ / kg, by using a device and method that utilize the heat of vaporization (latent heat of evaporation) when ammonia evaporates to lower the temperature of ammonia itself and maintain it in a liquid state, even if cracks, holes, or leaks occur at the joints in the tanks storing ammonia or the pipes supplying ammonia, as long as the pressure in the tanks storing ammonia or the pipes supplying ammonia is the same as atmospheric pressure, there will be no jetting. Compared to the tanks storing ammonia or the pipes supplying ammonia in a liquid state below -33°C, since the external temperature, including the atmosphere, is higher than that, the leaked ammonia will vaporize, lowering the temperature of the vaporized ammonia and its surrounding area, thus suppressing the jetting (leakage) of ammonia.

[0038] Taking advantage of such characteristics, in the present invention, by installing a device (3) that sucks the vaporized ammonia inside the ammonia tank and piping to keep the pressure inside the ammonia tank and piping below atmospheric pressure, the heat of vaporization (latent heat of evaporation) when ammonia evaporates is utilized to lower the temperature of the ammonia itself and maintain it in a liquid state. At the same time, by keeping the pressure in the tank (2) that supplies ammonia and the piping for transfer below atmospheric pressure, even if cracks, holes, or gaps occur at the joints in the tank or piping that stores or supplies ammonia, ammonia will not leak to the outside. Instead, outside air will be inhaled. Since the inhaled outside air has a lower density than liquid ammonia, it will stay at a position higher than the liquid level in the tank (2) that supplies ammonia and will not mix into the piping installed at the bottom of the tank (2) that supplies ammonia to a diesel engine, boiler, or gas turbine.

[0039] When the pressure in the tank (2) that supplies ammonia and the piping for transfer is kept below atmospheric pressure and cracks, holes, or gaps occur at the joints in the tank or piping that stores or supplies ammonia, allowing outside air to flow in and stay in the tank, due to the density differences among the liquid ammonia, vaporized ammonia, and the incoming outside air (air) in the tank, in the tank, a layer of vaporized ammonia, incoming outside air (air), and liquefied ammonia will be formed in that order from the upper part of the tank. By utilizing this characteristic and installing a sensor that detects the gas that has flowed in slightly above the liquid level of the liquid ammonia, for example, an oxygen concentration sensor when targeting air, it becomes possible to detect when cracks, holes, or gaps occur at the joints in the tank or piping that stores or supplies ammonia, allowing outside air to flow in.

[0040] Since a large amount of nitrogen oxides are generated from the combustion devices (7) of a diesel engine, a boiler, and a gas turbine that use ammonia as fuel, a nitrogen oxide reduction device (5) is required to convert these into nitrogen and water using a catalyst and a reducing agent. Currently, ammonia produced from urea is used as the reducing agent in the nitrogen oxide reduction device. However, in this system, by using a device (3) that sucks in vaporized ammonia, compresses it, and raises its temperature and pressure, and directly using the vaporized ammonia with increased temperature and pressure discharged from this device as the reducing agent, there is no longer a need for a urea tank, a urea injection device, or a device for converting urea into ammonia.

[0041] In Fig. 2, by sucking in vaporized ammonia to make the pressure inside the ammonia tank and the piping lower than atmospheric pressure, and making the temperature of the ammonia at the outlet of the device that compresses the sucked ammonia to raise its temperature and pressure higher than atmospheric temperature and the pressure higher than atmospheric pressure, it becomes possible to directly use the vaporized ammonia as the reducing agent for the nitrogen oxide reduction device (5). In the present invention, by installing a flow rate adjustment valve V-2 for the vaporized ammonia between the device (3) that sucks in vaporized ammonia, compresses it, and raises its temperature and pressure, and the nitrogen oxide reduction device (5), an optimal amount of vaporized ammonia is supplied to the nitrogen oxide reduction device (5) for the nitrogen oxides contained in the exhaust gas.

[0042] Fig. 3 shows an example of a detection and discharge function in the case of inhaling air due to damage to the ammonia supply system installed inside the ammonia tank according to an embodiment of the present invention. In FIG. 3, by installing an oxygen concentration sensor (14) several centimeters above the liquid level of ammonia, it becomes possible to detect cracks, holes, or gaps at joints in the tank storing ammonia or the pipes supplying ammonia when air flows in due to such defects. The oxygen concentration sensor (14) floats a float with the sensor installed at the liquid level of ammonia, so that even when the liquid level changes due to replenishment or consumption of liquid ammonia, it can always detect the presence of air staying near the liquid level. This is because when cracks, holes, or gaps occur at joints in the tank (1) storing ammonia, the supply tank (2) for ammonia, or the pipes supplying ammonia, and outside air flows in and stays inside the tank, due to the density differences among the liquid ammonia, vaporized ammonia, and the inflowing outside air (air) inside the tank, layers of vaporized ammonia, inflowing air, and liquefied ammonia are formed in this order from the upper part of the tank inside the tank. In addition, the outside air flowing in through cracks, holes, or gaps at joints in the tank and the pipes supplying ammonia stays in the middle between the liquid ammonia at the lower part of the tank and the gaseous ammonia at the upper part of the tank inside the tank. Therefore, by continuously sucking this air and discharging it into the atmosphere as it is or after some post-treatment, it becomes possible to continuously discharge the outside air that has flowed into the ammonia storage and supply system and continue the operation.

[0043] FIG. 4 shows an example of a specific configuration according to an embodiment of the present invention. In FIG. 4, the tank (2) for supplying ammonia is surrounded by a sealable double structure, and the inside of this double structure is connected to a vacuum pump (15) and a blower (16). The vacuum pump and the double structure can be separated using an on-off valve V-4. Also, the blower (16) and the double structure can be separated using an on-off valve V-5. An on-off valve V-6 is installed on the opposite side of the on-off valve V-5 installed in the double structure. When the on-off valve V-6 is opened, the double structure becomes open to the outside, and when the on-off valve V-6 is closed, the double structure becomes closed to the outside, that is, a sealed space.

[0044] This device is used when it is necessary to increase the amount of ammonia supplied to the nitrogen oxide reduction device (5) shown in FIG. 1. In FIG. 4, by closing the on-off valves V-5 and V-6 and operating the vacuum pump (15) by opening the on-off valve V-4, the inside of the sealed double space becomes vacuum, and the temperature inside the ammonia supply tank (2) can be maintained. Note that when the pressure inside the sealed double space reaches the set value, the operation of the vacuum pump (15) is stopped, and by closing the on-off valve V-4, the pressure of the sealed double space is maintained.

[0045] In FIG. 4, with the on-off valve V-4 closed and the on-off valves V-5 and V-6 open, by operating the blower (16), outside air (air) flows into and out of the inside of the double structure formed around the ammonia supply tank (2), which is at a higher temperature than the temperature of the ammonia stored in the tank (about minus 33 °C or lower), promoting the vaporization of the ammonia stored in the tank. Thereby, it becomes possible to increase the amount of ammonia supplied to the nitrogen oxide reduction device (5) shown in FIG. 1.

[0046] FIG. 5 shows an example of a device for effectively evaporating ammonia in a fuel supply tank according to an embodiment of the present invention. In FIG. 5, by installing a heating device (17) between the blower (16) and the double structure, the vaporization of the ammonia stored in the ammonia supply tank (2) is promoted, and it becomes possible to increase the amount of ammonia supplied to the nitrogen oxide reduction device (5) shown in FIG. 1. Also, as shown in FIG. 5, by providing a partition inside the tank to increase the area of contact and the residence time of the air that has flowed into the double structure with the double structure, the vaporization of the ammonia stored in the supply tank (2) is further promoted, and it becomes possible to further increase the amount of ammonia supplied to the nitrogen oxide reduction device (5) shown in FIG. 1.

Industrial Applicability

[0047] By installing the present invention in a diesel engine, a boiler, or a gas turbine, it becomes possible to safely store and supply ammonia, burn it effectively and efficiently in the combustion chamber, and reduce nitrogen oxides generated during combustion.

Explanation of Signs

[0048] 1. Ammonia storage tank 2. Ammonia supply tank 3. Device that sucks vaporized ammonia to make the pressure inside the ammonia tank and piping lower than atmospheric pressure, and compresses the sucked ammonia to increase the temperature and pressure 4. Device that cools and condenses ammonia with increased temperature and pressure 5. Nitrogen oxide reduction device 6. Ammonia supply pump 7. Combustion device for diesel engine, boiler, and gas turbine 8. Combustion chamber of diesel engine, boiler, and gas turbine 9. Blower 10. Ammonia detector 11. Heat exchanger 12. Fuel (fuel for assisting combustion of ammonia) tank 13. Device that supplies electric energy 14. Oxygen concentration sensor 15. Vacuum pump 16. Blower 17. Heater V-1. Ammonia supply source valve V-2. Flow rate adjustment valve for ammonia supplied to nitrogen oxide reduction device V-3. Pressure adjustment valve V-4. Communication valve with vacuum pump V-5. Communication valve with blower

Claims

1. A system for safely storing ammonia, comprising: a device for reducing the pressure inside an ammonia tank to a value lower than atmospheric pressure in order to prevent ammonia from leaking from the tank to the outside, including the atmosphere, and which is installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel; and a system for detecting cracks, holes, or gaps in the tank that stores ammonia using an oxygen concentration sensor installed near the liquid level inside the ammonia tank, taking advantage of the characteristic that when a crack, hole, or gap occurs in the tank that stores ammonia and air flows in, layers of vaporized ammonia, the flowed-in air, and liquefied ammonia are formed in the tank from the top, in that order, due to the density difference between the liquid ammonia, vaporized ammonia, and the flowed-in air.

2. 2. The system for safely storing ammonia according to claim 1, characterized in that in a system in which a device is installed for reducing the pressure inside the ammonia piping to a value lower than atmospheric pressure in order to prevent ammonia in the tank and piping for storing and transporting ammonia installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel from leaking from the piping to the outside, including the atmosphere, the system comprises a system capable of detecting cracks, holes, and gaps in the tank for storing ammonia and the piping for supplying ammonia by an oxygen concentration sensor installed near the liquid level inside the ammonia tank, utilizing a characteristic that when a crack, hole, or gap occurs in the piping for supplying ammonia and air flows in due to a crack, hole, or gap in a joint of the piping for supplying ammonia, layers of vaporized ammonia, the flowing in air, and liquefied ammonia are formed in the tank in this order from the top of the tank due to the density difference between the liquid ammonia, vaporized ammonia, and the flowing in air in the tank.

3. 2. The system for safely storing ammonia as described in claim 1, characterized in that in the system, a device is installed for making the pressure inside the ammonia tank lower than atmospheric pressure in order to prevent ammonia from leaking from the tank to the outside, including the atmosphere, in a tank that stores ammonia and is installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel, the system further comprising a device that continuously sucks in the air that has flowed into the ammonia tank and continuously releases it into the atmosphere either as is or after some kind of post-treatment, utilizing a characteristic in which air that has flowed in through cracks, holes, or gaps in the ammonia tank remains somewhere between the liquid ammonia in the lower part of the tank and the gaseous ammonia in the upper part of the tank due to a difference in density.

4. 2. The system for safely storing ammonia according to claim 1, wherein a device is installed for reducing the pressure inside the ammonia tank and the ammonia piping to a value lower than atmospheric pressure in order to prevent ammonia in the tank and piping for storing and transporting ammonia installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel from leaking from the piping to the outside, including the atmosphere, the system comprising a device for continuously sucking in air that has flowed into the ammonia storage and supply system and continuously releasing it into the atmosphere as is or after some kind of after-treatment, utilizing a characteristic that air that has flowed in through a crack, hole, or gap in a joint of the piping that supplies ammonia remains in the tank between the liquid ammonia in the lower part of the tank and the gaseous ammonia in the upper part of the tank due to a difference in density.

5. 2. A system for safely storing ammonia as described in claim 1, in which a device is installed to make the pressure inside the ammonia tank lower than atmospheric pressure in order to prevent ammonia from leaking from the tank to the outside, including the atmosphere, in a tank that stores ammonia and is installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel, the system being characterized in that the entire circumference or part of the circumference of the tank that stores ammonia is made into a sealed space with a double structure, the inside of this double structure is connected to a vacuum pump and a blower, and valves are installed at multiple points in the sealed space, so that when all valves are closed and the vacuum pump is operated, it is possible to keep the temperature inside the tank low, and when a fluid with a temperature higher than the boiling point of the ammonia stored in the tank is circulated with some of the valves open, it is possible to promote vaporization of the ammonia stored in the tank.

6. A method for safely storing ammonia, comprising: a system in which a device is installed for reducing the pressure inside an ammonia tank to a value lower than atmospheric pressure in order to prevent ammonia from leaking from the tank to the outside, including the atmosphere, in which the entire periphery or a part of the periphery of the tank for storing ammonia is made into a sealed space with a double structure, the inside of this double structure is connected to a vacuum pump and a blower, valves are installed at multiple points in the sealed space, and when the vacuum pump is operated with all valves closed, it is possible to maintain the temperature inside the tank at a low temperature; and when the blower is operated with some of the valves open to flow a fluid at a temperature higher than the boiling point of the ammonia stored in the tank, it is possible to promote the vaporization of the ammonia stored in the tank.

Images