System and method for safely storing and combusting ammonia

Abstract

The present invention relates to a system capable of safely storing ammonia, supplying it to a combustion device, and combusting it well to reduce nitrogen oxides generated during combustion. **Solution**: 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. To reduce nitrogen oxides generated during combustion, a device that sucks the vaporized ammonia inside the tank and piping to maintain the pressure inside the tank and piping below atmospheric pressure, a device that compresses the sucked vaporized ammonia to increase the temperature and pressure and supplies it to a nitrogen oxide reduction device (SCR) installed in the exhaust pipe, a device that condenses and liquefies the gaseous ammonia whose temperature and pressure have increased by lowering the temperature, and a device that returns the liquefied ammonia to the tank. A system and method for safely storing and combusting ammonia are constituted by these devices.

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 worldwide. Therefore, research is being conducted to utilize 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 property 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 air-fuel mixture in a combustion chamber and burns it in a mixed manner, 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, and achieve CO 2 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 secondary 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 unburned hydrogen by the jet torch flame. Patent Document 3 describes a technique in which, in an internal combustion engine using ammonia as fuel, a part of the ammonia supplied to the combustion chamber may not be burned in the combustion chamber and may be discharged, and NOx may be generated along with the combustion of the air-fuel mixture in the combustion chamber. Therefore, a technique for favorably purifying unburned ammonia and NOx contained in the exhaust gas discharged from the combustion chamber by a post-treatment device is described.

[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 (NH 3 ) does not contain a carbon component (C). Therefore, during combustion (oxidation reaction), CO2 Although it is regarded as a non-discharging fuel, when comparing the combustion-related characteristics such as flammability, combustion rate, and the potential to generate a large amount of NOx, which is an air pollutant during combustion, with petroleum-based fuels, it has toxicity. Compared with fossil fuels, which are the main fuels of current diesel engines, boilers, and gas turbines, it not only has problems to be solved regarding combustion, such as poor ignitability, slow combustion rate, and a high potential to generate nitrogen oxides (NOx), which are other air pollutants during combustion, but also has a physical characteristic that the calorific value per unit mass (volume) is extremely small (about one-quarter of petroleum-based fuels). Therefore, there are many technical issues to be improved. Due to 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 aims to provide a system that can safely store and transfer ammonia in a tank and is applicable to combustion devices of existing diesel engines, boilers, and gas turbines, which has the following elements, 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 transferring 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, even when the pressure inside the ammonia tank and piping is set to a value lower than atmospheric pressure, ammonia can be kept in a liquefied state. 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 risen after compression by lowering the temperature, and a device that returns the liquefied ammonia to the ammonia tank is provided with a structure and function that can keep the 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 the petroleum-based fuel supplied from the auxiliary fuel tank to zero, the CO 2 emitted from a diesel engine, boiler, or gas turbine that uses ammonia as fuel is made zero. To achieve this, the combustion of ammonia is improved using the electrical energy supplied from a device that supplies electrical energy. 5. The outer periphery of the tank and piping for storing and transporting ammonia is made into a sealed double structure with a vacuum inside, and an ammonia leakage detection device is installed inside the double structure. This can prevent release to the outside including the atmosphere and enable quick response by knowing the leakage in real time with the ammonia leakage detector. 6. A vacuum insulation device is installed around the entire circumference or a part of the circumference of the tank for storing ammonia to form a sealed structure, and valves are installed at multiple locations in the sealed space formed between the tank and the vacuum insulation device. When all the valves are closed, the temperature inside the tank can be kept low, 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, the vaporization of the ammonia stored in the tank can be promoted. 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, nitrogen oxides (NOx) generated by the combustion of ammonia can be reduced. 8. While operating a pump (ammonia supply pump) for supplying ammonia to the combustion devices of a diesel engine, a boiler, and a gas turbine, 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 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. A heat exchanger capable of setting the temperature of the gas inside the sucked airtight container to an arbitrary value is provided, and an ammonia concentration meter is installed between the blower and the heat exchanger. This ensures the safety that even if ammonia leaks from the sealed ammonia supply system, it will not be released to the outside, and if ammonia leaks, it can be detected promptly.

Means for Solving the Problems

[0008] Ammonia not only has problems to be solved regarding combustion, such as being toxic, having 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, 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 a system as follows.

[0009] The invention according to claim 1 is characterized in that, in a diesel engine, boiler, or gas turbine that uses 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 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, boiler, or gas turbine that uses 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 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 be able to keep ammonia in a liquefied state even when the pressure inside the ammonia tank and piping is made lower than 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 atmospheric pressure.

[0013] The invention according to claim 5 is an apparatus installed in a diesel engine, a boiler, or a gas turbine that uses ammonia as fuel, a tank and piping for storing and transferring ammonia, and by setting the pressure inside the ammonia tank and piping to a value lower than atmospheric pressure, in order to prevent ammonia from leaking from the tank and piping to the outside including the atmosphere, an apparatus that sucks the vaporized ammonia inside the ammonia tank and piping to maintain the pressure inside the ammonia tank and piping below atmospheric pressure, an apparatus that compresses the sucked vaporized ammonia to increase the temperature and pressure, an apparatus that condenses and liquefies the gaseous ammonia whose temperature and pressure have increased after compression by lowering the temperature, and an apparatus that returns the liquefied ammonia to the ammonia tank are installed.

[0014] The invention according to claim 6 is an apparatus installed in a diesel engine, a boiler, or a gas turbine that uses ammonia as fuel, a tank and piping for storing and transferring ammonia, an apparatus that sucks the vaporized ammonia inside the ammonia tank and piping to maintain the pressure inside the ammonia tank and piping below atmospheric pressure, an apparatus that compresses the sucked vaporized ammonia to increase the temperature and pressure, an apparatus that condenses and liquefies the gaseous ammonia whose temperature and pressure have increased after compression by lowering the temperature, and an apparatus that returns the liquefied ammonia to the ammonia tank are installed, and by using the method of 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 difference between the 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 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 the 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 the density difference. By using this characteristic, a device 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 in a combustion device installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel. By setting the co-combustion rate of the fuel containing carbon (C) supplied from an auxiliary fuel tank to zero, in order to make the CO 2 emitted from a diesel engine, boiler, or gas turbine that uses ammonia as fuel zero, a device for improving the combustion of ammonia using the electrical energy supplied from a device for supplying electrical energy is installed.

[0018] The invention according to claim 10 is in a combustion device installed in a diesel engine, boiler, or gas turbine that uses ammonia as fuel. By using the method of improving the combustion of ammonia using the electrical energy supplied from a device for supplying electrical energy and setting the co-combustion rate of the fuel containing carbon (C) supplied from an auxiliary fuel tank to zero, the CO2 It is characterized in that it can be set to 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. 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, the vaporization of the ammonia stored in the tank can be promoted.

[0020] In addition, the invention according to claim 11 can also be applied to a method for 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, the vaporization of the ammonia stored in the tank can be promoted".

[0021] The invention according to claim 12 is characterized in that in order to reduce nitrogen oxides (NOx) generated by the combustion of ammonia, a device is provided 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] Incidentally, the invention described in claim 12 can also be applied to a method for safely storing and burning ammonia, which is "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 becomes possible to reduce nitrogen oxides (NOx) generated by the combustion of ammonia."

[0023] The invention described in 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 a combustion device of a diesel engine, a boiler, or 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] Incidentally, the invention described in claim 13 can also be applied to a system for safely storing and burning ammonia, which is "by using a 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 a combustion device of a diesel engine, a boiler, or 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 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 the leakage. A part of the portion where the internal pressure is higher than atmospheric pressure is covered with a container and the interior is sealed, and a part thereof is sucked by a blower, and a heat exchanger capable of setting the temperature of the gas in the sucked sealed 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, covering a portion where the internal pressure is higher than atmospheric pressure with a container, sealing the interior, sucking a part thereof by a blower, providing a heat exchanger capable of setting the temperature of the gas in the sucked sealed container to an arbitrary value, and installing an ammonia concentration meter between the blower and the heat exchanger. By using this method, when the pressure inside the ammonia supply system becomes higher than 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 the leakage."

Advantages of the Invention

[0027] By using the present invention, in a diesel engine, boiler, or 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 the vaporized ammonia to make the pressure inside the ammonia tank (1) and / or (2) and the pipe 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 selective catalytic 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) surrounded 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 again after passing 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 perforation, cracking, loosening, etc. of the packing 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, a stable state can be maintained by a system that sucks the vaporized ammonia with the device (3), condenses it with the device (4), and returns it to the tank (2). 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 event that ammonia leaks due to perforation, cracking, loosening, etc. of the packing installed in the joints and valves installed in the tanks and pipes of the ammonia storage and supply system, it is possible to avoid a situation where ammonia leaks to the outside by sucking outside air (air) from that location.

[0031] When using devices (3) and (4) installed in 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, without operating these devices, a method for keeping the pressure in the ammonia tank and supply system lower than atmospheric pressure using the system shown in Fig. 1 will be described. In Fig. 1, the ammonia supplied to the combustion device is sucked 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 is high enough not to vaporize even when the temperature of ammonia is increased in the combustion device. Therefore, 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. In this way, 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 of 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 to maintain the pressure and supply amount of the ammonia supplied to the combustion device (7), 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) can be made lower than atmospheric pressure, and it is possible to prevent 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, the ammonia discharged from the tank (2) that supplies ammonia reaches the combustion device (7) of the diesel engine, boiler, and gas turbine through the pipe that transfers ammonia. Since ammonia has 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, in the combustion device (7), light oil, heavy oil, LNG, etc. transferred from the tank (12) that stores petroleum-based fuels that serve as combustion aids for ammonia are mixed, injected in layers, and independently injected, whereby it becomes possible to improve the ignitability and combustion speed of ammonia. At this time, whether the state of the ammonia injected in the combustion device (7 ) is liquid or gas is determined by the form of the combustion device that has a structure and function to improve combustion by mixing, injecting in layers, and independently injecting petroleum-based fuels.

[0033] The object of the present invention is to safely supply ammonia, a fuel that does not contain a carbon component, to a diesel engine, boiler, and gas turbine, effectively and efficiently burn it in the combustion chamber, and reduce nitrogen oxides generated during combustion, thereby contributing to the prevention of global warming. However, since fuels such as light oil, heavy oil, and LNG, which serve as combustion aids for ammonia, contain carbon, it becomes a technical problem to reduce the co-combustion rate of these fuels as much as possible, but it is difficult to make it zero. To solve this problem, 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 emission amount 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, which has poor ignitability and a slow combustion rate. Note that the electricity supplied to the device (12) that supplies electrical energy is generated 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, thereby making it 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 rate compared to fossil fuels, which are the main fuels of current diesel engines, boilers, and gas turbines. However, ensuring safety during the storage and transfer 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 a high energy density, it is necessary to keep the temperature below that under atmospheric pressure. Also, in order to maintain a 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 diesel engines, boilers, and gas turbines, 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 from the joints in the tank for storing ammonia or the pipes for supplying ammonia, the ammonia will vaporize and eject in a gaseous state. The vaporized ammonia (NH 3) has a molecular weight of 17 and is lighter than the approximate molecular weight of air, which is 29. Therefore, in the atmosphere, it will move upward. For this reason, when the installation location of the equipment for storing and transporting ammonia is outdoors, safety issues are reduced. However, when it is installed at the bottom of an indoor facility, especially in 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. As a result, 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 at approximately 2250 kJ / kg, by using the property that it shows a higher value than other substances, a device and method are used to lower the temperature of ammonia itself by utilizing the heat of vaporization (latent heat of evaporation) when ammonia evaporates to maintain a liquid state. Even when cracks, holes, or leaks occur at the joints of the tank for storing ammonia or the pipes for supplying ammonia, if the pressure of the tank for storing ammonia or the pipes for supplying ammonia is the same as the atmospheric pressure, there will be no jetting. Compared with the tank for storing ammonia or the pipes for supplying ammonia in a liquid state below -33°C, since the external temperature including the atmosphere is higher than that, the leaked ammonia vaporizes, thereby lowering the temperature of the vaporized ammonia and its surrounding area, and the jetting (leakage) of ammonia is suppressed.

[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 temperature of the ammonia itself is lowered by utilizing the heat of vaporization (latent heat of vaporization) when the ammonia evaporates to maintain the 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 for storing ammonia or the piping for supplying 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 of 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 the 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 for storing ammonia or the piping for supplying ammonia, allowing outside air to flow in and stay inside the tank, due to the density difference between the liquid ammonia, vaporized ammonia, and the inflowing outside air (air) inside the tank, a layer of vaporized ammonia, inflowing outside air (air), and liquefied ammonia will be formed in the tank in 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 for storing ammonia or the piping for supplying ammonia, allowing outside air to flow in.

[0040] Since a large amount of nitrogen oxides are generated from the combustion devices (7) of diesel engines, boilers, and gas turbines 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 generated from urea is used as the reducing agent in nitrogen oxide reduction devices. However, in this system, an apparatus (3) that sucks in vaporized ammonia, compresses it, and raises its temperature and pressure is used, and the vaporized ammonia discharged from this apparatus, with its increased temperature and pressure, is used directly as the reducing agent, eliminating the need for a urea tank, a urea injection device, and a device for converting urea to ammonia.

[0041] In Fig. 2, by sucking in vaporized ammonia to make the pressure inside the ammonia tank and piping lower than atmospheric pressure, and by making the temperature of the ammonia at the outlet of the apparatus 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 use the vaporized ammonia directly 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 apparatus (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 the detection and discharge functions 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 when cracks, holes, or gaps occur at the joints in the tank storing ammonia or the pipes supplying ammonia, allowing air to flow in. The oxygen concentration sensor (14) floats a float with the sensor installed at the liquid level of ammonia, enabling it to always detect the presence of air remaining near the liquid level even when the liquid level changes due to the replenishment or consumption of liquid ammonia. This is because when cracks, holes, or gaps occur at the joints in the tank (1) storing ammonia, the supply tank (2) for ammonia, or the pipes supplying ammonia, allowing outside air to flow in and stay 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 order from the upper part of the tank inside the tank. Note that the outside air flowing in through the cracks, holes, or gaps at the 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) 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 disconnected using an on-off valve V-4. Also, the blower (16) and the double structure can be disconnected 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. 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, the blower (16) is operated, so that 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 temperature higher 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. As a result, 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 flowing 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, ammonia can be safely stored and supplied, efficiently burned in the combustion chamber, and nitrogen oxides generated during combustion can be reduced.

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 the nitrogen oxide reduction device V-3. Pressure adjustment valve V-4. Communication valve with the vacuum pump V-5. Communication valve with the 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. A system for safely storing ammonia as described in claim 1, characterized in that it is equipped with a system that can detect cracks, holes or gaps that occur in the tank for storing ammonia or in the piping for supplying ammonia by an oxygen concentration sensor installed near the liquid level inside the ammonia tank, taking advantage of the characteristic that if a crack, hole or gap occurs in the piping that supplies ammonia and air flows in, layers of vaporized ammonia, the flowing in air and liquefied ammonia will be formed in the tank from the top down due to the density difference between the liquid ammonia, vaporized ammonia and the flowing in air.

3. A system for safely storing ammonia as described in claim 1, characterized in that the system is equipped with a device which 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-processing, taking advantage of the characteristic that air that has flowed in through cracks, holes or gaps in the joints of the ammonia tank remains somewhere between the liquid ammonia at the bottom of the tank and the gaseous ammonia at the top of the tank due to the difference in density.

4. A system for safely storing ammonia as described in claim 1, characterized in that the system is equipped with a device which continuously sucks in air that has flowed into the ammonia storage and supply system and continuously releases it into the atmosphere either as is or after some kind of post-treatment, taking advantage of the characteristic that air that has flowed in through cracks, holes or gaps in the joints of the piping that supplies ammonia 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 the difference in density.

5. A system for safely storing ammonia as described in claim 1, characterized in that the entire circumference or part of the circumference of a tank for storing ammonia is made into a double-structured sealed space, 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 the blower is operated with some of the valves open to circulate a fluid at a temperature higher than the boiling point of the ammonia stored in the tank, it is possible to promote the evaporation 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.

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