Method and apparatus for purging a combustion furnace

Abstract

To provide a purging method and a purging apparatus for a combustion furnace that can reduce purging costs in the combustion furnace that burns a fuel containing a hydrogen gas.SOLUTION: An example of a method for purging a combustion furnace comprises: temporarily storing a combustion gas, which is discharged from a combustion furnace 2 that burns a fuel containing a hydrogen gas, in a combustion gas tank 20 such that the combustion gas is compressed to a predetermined standard pressure; and then purging the combustion furnace 2 while supplying the combustion furnace 2 with the combustion gas stored in the combustion gas tank 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a purging method and a purging device for a combustion furnace.

Background Art

[0002] In recent years, hydrogen has attracted attention as a fuel with a low environmental impact and clean because the product of combustion is only water and no CO2 is emitted. On the other hand, hydrogen has a high risk of explosion because it has a wider flammable range compared to other gas fuels. It also has characteristics such as a small specific gravity and high diffusibility.

[0003] Conventionally, in a combustion furnace provided in a boiler or the like, if unburned gas remains in the furnace, there is a risk of explosion when ignition occurs. Therefore, before combustion starts or after combustion ends, a purge gas such as air is sent into the furnace to expel the unburned gas, that is, purging is performed. The purge before combustion starts is called pre-purge, and the purge after combustion ends is called post-purge.

[0004] When hydrogen gas is used as fuel in the above combustion furnace, if air is supplied into the furnace as the purge gas, the hydrogen remaining as unburned gas has a wide flammable range and there is a risk of explosion. Therefore, usually, an inert gas such as nitrogen is used as the purge gas.

[0005] Patent Document 1 describes a purging method for a gasification facility comprising a gasifier that gasifies raw materials to produce gasified gas and combustible solids, and a combustion furnace that burns the combustible solids produced in the gasifier. In Patent Document 1, when purging the gasifier, if the O2 concentration of the combustion gas discharged from the combustion furnace is below a set value, the combustion gas is supplied to the gasifier as purge gas. On the other hand, if the O2 concentration of the combustion gas exceeds the set value, an inert gas is mixed with the combustion gas to reduce the O2 concentration to below the set value, and this mixture is supplied to the gasifier as purge gas. In the case of Patent Document 1, the amount of inert gas used can be reduced, but since an inert gas is mixed with the combustion gas when the O2 concentration of the combustion gas exceeds the set value, it is necessary to store the inert gas in a gas tank. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-222295 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, purging the aforementioned combustion furnace typically requires a large amount of purge gas, usually more than four times the volume of the combustion furnace. Therefore, when using hydrogen gas as fuel for the combustion furnace, constantly having a large amount of inert gas on hand as purge gas will lead to increased purging costs.

[0008] This disclosure was made to solve the above-mentioned problems and aims to provide a purging method and purging apparatus for a combustion furnace that can reduce purging costs in a combustion furnace that burns fuel containing hydrogen gas. [Means for solving the problem]

[0009] To achieve the above objective, a combustion furnace purging method according to one aspect of the present disclosure involves compressing the combustion gas discharged from a combustion furnace that burns a fuel containing hydrogen gas to a predetermined reference pressure and storing it in a combustion gas tank, and supplying the combustion gas stored in the combustion gas tank to the combustion furnace when purging the combustion furnace.

[0010] A combustion furnace purging device according to one aspect of the present disclosure includes a combustion gas tank that temporarily stores combustion gas discharged from a combustion furnace that burns a fuel containing hydrogen gas, compressed to a predetermined reference pressure, and a purge gas supply unit that supplies the combustion gas stored in the combustion gas tank to the combustion furnace when purging the combustion furnace. [Effects of the Invention]

[0011] This disclosure provides a combustion furnace purging method and purging apparatus having the configuration described above, which can reduce purging costs in a combustion furnace that burns a fuel containing hydrogen gas. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram of the entire combustion system, including the purging device of the combustion furnace, in an embodiment of the present disclosure. [Modes for carrying out the invention]

[0013] Preferred embodiments of this disclosure will be described below with reference to the drawings. However, this disclosure is not limited to the embodiments described below.

[0014] (Embodiment) Figure 1 is a schematic diagram of the entire combustion system, including the purging device of the combustion furnace, in an embodiment of the present disclosure.

[0015] The combustion system shown in Figure 1 comprises a boiler 1 and a purge device 10. This boiler 1 uses hydrogen gas as fuel. Hydrogen gas is supplied to the boiler 1 from the fuel supply line 3, and combustion air is supplied from the combustion air supply line 4, and the fuel is burned in the combustion furnace 2. The combustion gas discharged from the combustion furnace 2 after the fuel is burned is discharged into the atmosphere through the chimney 9 via the combustion gas discharge line 5, which consists of a flue. A shut-off valve 6 is installed in the middle of the fuel supply line 3. Combustion air is supplied to the wind box of the boiler 1 by a forced-air blower 7 in the combustion air supply line 4. A combustion air damper 8 is installed in the middle of the combustion air supply line 4 to adjust the flow rate of combustion air. An induced draft blower may be installed in front of the chimney 9 in the combustion gas discharge line 5.

[0016] The purge device 10 comprises a combustion gas tank 20, a combustion gas inlet 30A, a purge gas supply unit 40A, and a controller 50. The combustion gas tank 20 is equipped with a pressure gauge 21 for measuring the pressure of the combustion gas stored in the tank, and the measured value from the pressure gauge 21 is output to the controller 50.

[0017] The combustion gas introduction section 30A includes a combustion gas introduction line 30, a combustion gas damper 31, a cooling device 32, a mist separator 33, a compressor 34, a combustion gas shut-off valve 35, and a check valve 36.

[0018] The combustion gas introduction line 30 is connected to the combustion gas discharge line 5 and consists of gas pipes, etc., for introducing a portion of the combustion gas passing through the combustion gas discharge line 5 into the combustion gas tank 20. The combustion gas introduction line 30 is equipped with, in order from the upstream side in the direction of combustion gas flow, a combustion gas damper 31, a cooling device 32 for cooling the combustion gas, a mist separator 33 for removing moisture from the combustion gas, a compressor 34, a combustion gas shut-off valve 35, and a check valve 36. The compressor 34 pressurizes the combustion gas from which moisture has been removed by the mist separator 33 and sends it to the combustion gas tank 20.

[0019] The purge gas supply unit 40A includes a purge gas line 40, a purge gas shut-off valve 41, a check valve 42, and a purge gas flow meter 43.

[0020] The purge gas line 40 extends from the combustion gas tank 20 and is connected to the middle of the combustion air supply line 4 in order to supply the combustion gas once stored in the combustion gas tank 20 to the combustion furnace 2. The purge gas line 40 is provided with a purge gas shut-off valve 41, a check valve 42, and a purge gas flow meter 43 in order from the combustion gas tank 20 side. The purge gas flow meter 43 measures the flow rate of the combustion gas, which is the purge gas flowing through the purge gas line 40, and the measured value is output to the controller 50.

[0021] The controller 50 can be composed of, for example, a microcontroller, MPU, PLC (Programmable Logic Controller), logic circuit, etc. Here, the controller 50 controls the entire combustion system shown in FIG. 1. That is, in addition to the purge device 10, the controller 50 controls the boiler 1, the shut-off valve 6, the forced draft fan 7, the combustion air damper 8, etc. Here, the controller 50 controls the combustion gas damper 31, the cooling device 32, the compressor 34, and the combustion gas shut-off valve 35 in the purge device 10. Note that the controller 50 may be composed of a single controller for centralized control, or may be composed of a plurality of controllers that cooperate with each other for distributed control.

[0022] Next, the operation of the combustion system having the purge device 10 will be described.

[0023] During the operation of the boiler 1, that is, when hydrogen gas fuel is burned in the combustion furnace 2 of the boiler 1, the shut-off valve 6 of the fuel supply line 3 is opened and hydrogen gas is supplied to the burner of the boiler 1, the forced draft fan 7 is operated, and combustion air is sent into the combustion air supply line 4. The flow rate is adjusted by the combustion air damper 8 and supplied to the wind box of the boiler 1. Thereby, the combustion gas generated by burning the fuel in the combustion furnace 2 of the boiler 1 is discharged into the atmosphere from the chimney 9 through the combustion gas discharge line 5.

[0024] During the operation of this boiler 1, the controller 50 closes the purge gas shut-off valve 41. When the pressure of the combustion gas in the combustion gas tank 20 measured by the pressure gauge 21 is less than a predetermined reference pressure, the controller 50 opens the combustion gas damper 31 and the combustion gas shut-off valve 35, and operates the cooling device 32 and the compressor 34. On the other hand, when the pressure of the combustion gas in the combustion gas tank 20 measured by the pressure gauge 21 becomes equal to or higher than the reference pressure, the controller 50 closes the combustion gas damper 31 and the combustion gas shut-off valve 35, and stops the operation of the cooling device 32 and the compressor 34. As a result, the combustion gas compressed to the reference pressure is stored in the combustion gas tank 20.

[0025] In addition, when the controller 50 purges the combustion furnace 2, that is, when performing pre-purge before fuel combustion starts and post-purge after combustion stops in the combustion furnace 2, the shut-off valve 6 of the fuel supply line 3 is in a closed state, the push blower 7 of the combustion air supply line 4 is in a stopped state, and the combustion air damper 8 is in a closed state. Also, the combustion gas damper 31 and the combustion gas shut-off valve 35 are in a closed state.

[0026] When performing the purge, the controller 50 opens the purge gas shut-off valve 41 to supply the combustion gas stored in the combustion gas tank 20 to the combustion furnace 2 through the purge gas line 40 and the combustion air supply line 4. Then, the controller 50 grasps the amount of the combustion gas supplied to the combustion furnace 2 based on the measured value of the purge gas flow meter 43, and when this amount reaches a predetermined amount, closes the purge gas shut-off valve 41 to end the purge.

[0027] Note that even if the purge gas line 40 does not have a purge gas flow meter 43, and the purge gas shut-off valve 41 is closed after a predetermined time has elapsed since the purge gas shut-off valve 41 was opened, the combustion gas of the above-mentioned predetermined amount may be configured to be supplied to the combustion furnace 2.

[0028] As described above, during the combustion operation of boiler 1, combustion gas compressed to a reference pressure is stored in the combustion gas tank 20. This allows combustion gas to flow out of the combustion gas tank 20 into the purge gas line 40 when purging is performed by opening the purge gas shut-off valve 41, and is supplied to the combustion furnace 2 through the purge gas line 40 and the combustion air supply line 4, enabling purging of the combustion furnace 2. The reference pressure may be set to, for example, several times atmospheric pressure.

[0029] The purge device 10 for the combustion furnace 2 in this embodiment includes a combustion gas tank 20 that temporarily stores combustion gas discharged from the combustion furnace 2, which burns hydrogen gas fuel, in a compressed state at a predetermined reference pressure, and a purge gas supply unit 40A that supplies the combustion gas stored in the combustion gas tank 20 to the combustion furnace 2 when purging the combustion furnace 2. With this configuration, only combustion gas is stored in the combustion gas tank 20, and only combustion gas is supplied to the combustion furnace 2 as purge gas when purging the combustion furnace 2, so an inert gas is not required as purge gas, and purging costs can be reduced. In addition, since the oxygen concentration of combustion gas is much lower than that of air, the risk of explosion of hydrogen contained in unburned fuel that has remained in the combustion furnace 2 during purging can be reduced.

[0030] Furthermore, in the combustion gas introduction section 30A, a cooling device 32, a mist separator 33, and a compressor 34 are installed in the combustion gas introduction line 30. Since water is produced when hydrogen gas is burned, the combustion gas contains moisture. In the combustion gas introduction section 30A, the combustion gas is cooled by the cooling device 32 and moisture is removed from the combustion gas by the mist separator 33, thereby preventing failure of the compressor 34.

[0031] In the above, boiler 1 is assumed to be a boiler exclusively burned with hydrogen gas, but any boiler that burns fuel containing hydrogen gas is acceptable. For example, it may be a boiler that co-fires hydrogen gas with other fuels such as heavy oil. In the case of a co-firing boiler, if the fuel contains corrosive components such as sulfur, a filtration device 37 for removing corrosive components from the combustion gas may be installed in the combustion gas introduction line 30 between the combustion gas damper 31 and the cooling device 32, as shown by the dashed line in Figure 1.

[0032] Furthermore, the combustion furnace 2 is not limited to a combustion furnace consisting of a boiler's combustion chamber; any combustion furnace that burns fuel containing hydrogen gas is acceptable.

[0033] From the above description, many improvements and other embodiments of the disclosure will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the disclosure. The details of its structure and / or function can be substantially modified without departing from the spirit of the disclosure.

[0034] (Summary of this disclosure) A purging method for a combustion furnace according to a first aspect of this disclosure involves compressing the combustion gas discharged from a combustion furnace that burns a fuel containing hydrogen gas to a predetermined reference pressure and storing it in a combustion gas tank, and supplying the combustion gas stored in the combustion gas tank to the combustion furnace when purging the combustion furnace.

[0035] According to this method, only combustion gas is stored in the combustion gas tank, and only combustion gas is supplied to the combustion furnace as purge gas when purging the furnace. This eliminates the need for inert gas as purge gas, thus reducing purging costs. Furthermore, since combustion gas has a much lower oxygen concentration than air, the risk of hydrogen explosion from unburned fuel remaining in the combustion furnace during purging can be reduced.

[0036] A combustion furnace purging method according to a second aspect of this disclosure is a combustion furnace purging method according to a first aspect, wherein the combustion gas discharged from the combustion furnace is cooled, and after this cooling, moisture is removed with a mist separator, and then the gas is pumped to the combustion gas tank with a compressor.

[0037] In this way, the combustion gas is cooled and moisture is removed from the combustion gas by the mist separator, which prevents compressor failure.

[0038] A combustion furnace purging device according to a third aspect of this disclosure includes a combustion gas tank that temporarily stores combustion gas discharged from a combustion furnace that burns a fuel containing hydrogen gas, in a compressed state at a predetermined reference pressure, and a purge gas supply unit that supplies the combustion gas stored in the combustion gas tank to the combustion furnace when purging the combustion furnace.

[0039] With this configuration, only combustion gas is stored in the combustion gas tank, and only combustion gas is supplied to the combustion furnace as purge gas when purging the furnace. This eliminates the need for inert gas as purge gas, thus reducing purging costs. Furthermore, since combustion gas has a much lower oxygen concentration than air, the risk of hydrogen explosion from unburned fuel remaining in the combustion furnace during purging can be reduced.

[0040] A combustion furnace purging device according to a fourth aspect of the present disclosure further comprises, in a combustion furnace purging device according to a third aspect: a combustion gas introduction line for introducing combustion gas discharged from the combustion furnace into the combustion gas tank; a cooling device installed in the combustion gas introduction line for cooling the combustion gas introduced into the combustion gas introduction line; a mist separator installed in the combustion gas introduction line for removing moisture from the combustion gas cooled by the cooling device; and a compressor installed in the combustion gas introduction line for pumping the combustion gas from which moisture has been removed by the mist separator to the combustion gas tank.

[0041] In this way, the combustion gas is cooled and moisture is removed from the combustion gas by the mist separator, which prevents compressor failure.

[0042] A purge device for a combustion furnace according to a fifth aspect of the present disclosure, in a purge device for a combustion furnace according to a fourth aspect, further comprising: a purge gas supply unit having a purge gas line extending from the combustion gas tank and connected in the middle of a combustion air supply line that supplies combustion air to the combustion furnace while fuel is burning; a purge gas shut-off valve installed in the purge gas line; a combustion gas damper installed upstream of the cooling device in the combustion gas introduction line; a combustion gas shut-off valve installed between the compressor and the combustion gas tank in the combustion gas introduction line; a pressure gauge for measuring the pressure of the combustion gas in the combustion gas tank; and a controller for controlling the combustion gas damper, the combustion gas shut-off valve and the purge gas shut-off valve, wherein the controller When combustion air is supplied from the combustion air supply line to the combustion furnace and fuel is burned in the combustion furnace, with the purge gas shutoff valve closed, if the pressure of the combustion gas in the combustion gas tank measured by the pressure gauge is below the reference pressure, the combustion gas damper and the combustion gas shutoff valve are opened. When the pressure of the combustion gas in the combustion gas tank becomes equal to or greater than the reference pressure, the combustion gas damper and the combustion gas shutoff valve are closed. When purging the combustion furnace, with the combustion gas damper and the combustion gas shutoff valve closed, the purge gas shutoff valve is opened to supply the combustion gas stored in the combustion gas tank to the combustion furnace through the purge gas line and the combustion air supply line.

[0043] This allows combustion gas at a standard pressure to be stored in a combustion gas tank while fuel is burning in the combustion furnace, and when purging is performed, the combustion gas stored in the combustion gas tank can be supplied to the combustion furnace by opening the purge gas shut-off valve. [Explanation of Symbols]

[0044] 1 Boiler 2 Combustion furnace 4. Combustion air supply line 10. Purge device 20 Combustion gas tanks 21 Pressure gauge 30 Combustion gas introduction line 31 Combustion gas damper 32 Cooling device 33 Mist Separator 34 Compressor 35 Combustion gas shutoff valve 40A Purge Gas Supply Unit 40 Purge gas line 41 Purge gas shutoff valve 50 Controllers

Claims

1. Cooling the combustion gases emitted from a combustion furnace that burns fuel containing hydrogen gas, After this cooling, the moisture is removed with a mist separator. The combustion gas, after the moisture has been removed, is pumped to a combustion gas tank by a compressor, and is temporarily stored in the combustion gas tank in a state where it has been compressed to a predetermined reference pressure. When purging the combustion furnace, the combustion gas stored in the combustion gas tank is supplied to the combustion furnace. Method for purging a combustion furnace.

2. A combustion gas tank that temporarily stores combustion gases discharged from a combustion furnace that burns fuel containing hydrogen gas, while compressed to a predetermined reference pressure, A purge gas supply unit that supplies combustion gas stored in the combustion gas tank to the combustion furnace when purging the combustion furnace, A combustion gas introduction line for introducing combustion gas discharged from the combustion furnace into the combustion gas tank, A cooling device installed in the combustion gas introduction line for cooling the combustion gas introduced into the combustion gas introduction line, A mist separator is installed in the combustion gas introduction line and removes moisture from the combustion gas cooled by the cooling device, The combustion gas introduction line is equipped with a compressor that is installed thereto and pumps the combustion gas from which moisture has been removed by the mist separator to the combustion gas tank. A purging device for a combustion furnace.

3. The purge gas supply unit includes a purge gas line that extends from the combustion gas tank and is connected to the combustion air supply line that supplies combustion air to the combustion furnace while fuel is burning, and a purge gas shut-off valve installed in the purge gas line. A combustion gas damper installed upstream of the cooling device in the aforementioned combustion gas introduction line, A combustion gas shut-off valve is installed between the compressor and the combustion gas tank in the combustion gas introduction line, A pressure gauge for measuring the pressure of the combustion gas in the aforementioned combustion gas tank, The system further comprises a controller for controlling the combustion gas damper, the combustion gas shutoff valve, and the purge gas shutoff valve, The controller is, When combustion air is supplied from the combustion air supply line to the combustion furnace and fuel is burned in the combustion furnace, with the purge gas shutoff valve closed, if the pressure of the combustion gas in the combustion gas tank measured by the pressure gauge is below the reference pressure, the combustion gas damper and the combustion gas shutoff valve are opened, and when the pressure of the combustion gas in the combustion gas tank becomes equal to or greater than the reference pressure, the combustion gas damper and the combustion gas shutoff valve are closed. When purging the combustion furnace, the combustion gas damper and the combustion gas shut-off valve are closed, and the purge gas shut-off valve is opened to supply the combustion gas stored in the combustion gas tank to the combustion furnace through the purge gas line and the combustion air supply line. A purging device for a combustion furnace according to claim 2.

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