JP7650786B2 - Self-ignition prevention device - Google Patents

Description

This disclosure relates to a self-ignition prevention device that prevents the spontaneous ignition of flammable gas in a pipe.

For example, dust contained in the exhaust gas from waste incinerators, integrated coal gasification combined cycle (IGCC) plants, and power generation boilers adheres to the inner walls of the furnace and the outer surfaces of heat transfer tubes. Dust that adheres to the inner walls of the furnace and the outer surfaces of heat transfer tubes reduces the heat transfer coefficient, worsening the heat recovery efficiency, and creates resistance to the flow of exhaust gas, reducing the performance of the furnace.

One example of a device for removing dust that has adhered to the inner walls of a furnace or the outer surfaces of heat transfer tubes is described in Patent Document 1 below. The dust removal device described in Patent Document 1 fills flammable gas into piping that connects to the inside of the furnace, and ignites the flammable gas to generate shock waves through detonation. With this dust removal device, the shock waves act on the inner walls of the furnace and the outer surfaces of the heat transfer tubes, blowing away and removing the adhered dust.

US Patent Application Publication No. 2005/0126594

Conventional dust removal devices have multiple gate valves arranged in the piping, and when not in operation, the gate valves are moved to a closed position to prevent spontaneous ignition of the flammable gas filled in the piping. However, if the inner diameter of the piping is large, the valves become large, which creates an issue of increased parts and maintenance costs. In addition, because the gate valves are placed in a high-temperature environment, there is a risk of malfunction, making it difficult to adequately prevent spontaneous ignition of the flammable gas.

The present disclosure aims to solve the above-mentioned problems by providing an autoignition prevention device that appropriately suppresses the autoignition of flammable gas while suppressing increases in parts and maintenance costs.

To achieve the above object, the self-ignition prevention device disclosed herein comprises a pipe that can be filled with flammable gas and can be connected to a target area, an expansion pipe that is provided between the pipe and the target area and has an inner diameter larger than the inner diameter of the pipe, and an ejection part that ejects non-flammable gas from the outer periphery of the expansion pipe toward the center.

The self-ignition prevention device disclosed herein can prevent increases in parts costs and maintenance costs, while also appropriately preventing self-ignition of flammable gases.

FIG. 1 is a cross-sectional view of a furnace illustrating a self-ignition prevention device according to a first embodiment. FIG. 2 is a front view of the self-ignition prevention device as seen from the furnace side. FIG. 3 is a cross-sectional view of a furnace illustrating the auto-ignition prevention device according to the second embodiment. FIG. 4 is a cross-sectional view of a furnace illustrating a self-ignition prevention device according to the third embodiment. FIG. 5 is a front view of the self-ignition prevention device as seen from the furnace side. FIG. 6 is a cross-sectional view of a furnace illustrating a self-ignition prevention device according to a fourth embodiment. FIG. 7 is a cross-sectional view of a furnace illustrating a self-ignition prevention device according to the fifth embodiment.

Below, a preferred embodiment of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the various embodiments. Furthermore, the components in the embodiments include those that a person skilled in the art would easily imagine, those that are substantially the same, and those that are within the so-called equivalent range.

[First embodiment]
<Configuration of the self-ignition prevention device>
FIG. 1 is a cross-sectional view of a furnace showing a self-ignition prevention device of a first embodiment, and FIG. 2 is a front view of the self-ignition prevention device from the furnace side.

The spontaneous ignition prevention device of the first embodiment is applied to a dust removal device that removes dust adhering to the inner wall surfaces and outer surfaces of heat transfer tubes of furnaces such as waste incinerators, integrated coal gasification combined cycle power plants, and power generation boilers (hereinafter referred to as boilers). The dust removal device supplies combustible gas into the furnace through piping that communicates with the inside of the furnace, and generates shock waves due to detonation by igniting the combustible gas. The dust removal device blows away and removes the adhering dust by the shock waves caused by the detonation acting on the inner walls of the furnace and the outer surfaces of the heat transfer tubes.

The self-ignition prevention device is installed in the dust removal device and prevents the spontaneous ignition of flammable gases that fill the piping due to the heat of the exhaust gases rising inside the furnace while the boiler is in operation.

As shown in Figures 1 and 2, the self-ignition prevention device 10 includes a pipe 11, an expansion pipe 12, and an ejection section 13.

The furnace 101 has a furnace wall 102. The furnace 101 has an internal space 103 defined by the inner wall surface 102a of the furnace wall 102. In the internal space 103 of the furnace 101, a heat transfer tube constituting a heat exchanger (not shown) is arranged. In the internal space 103 of the furnace 101, high-temperature exhaust gas G1 flows in a predetermined direction. The flow direction of the high-temperature exhaust gas G1 varies depending on the position of the internal space 103 and the surrounding shape, but the following describes the case where the high-temperature exhaust gas G1 rises in the internal space 103.

The pipe 11 is capable of supplying the flammable gas G2 to the internal space 103, which is the target area. The pipe 11 is, for example, cylindrical in shape and has the same inner diameter in the longitudinal direction. However, the pipe 11 is not limited to a cylindrical shape and may be a polygonal tube shape. A supply device (not shown) for the flammable gas G2 is connected to one axial end of the pipe 11, and an expansion tube 12 is connected to the other end.

The diffuser 12 is provided between the pipe 11 and the furnace wall 102 (internal space 103) of the furnace 101. The inner diameter of the diffuser 12 on the furnace wall 102 side is larger than the inner diameter of the pipe 11. The diffuser 12 expands continuously and uniformly from the pipe 11 side toward the furnace wall 102 (internal space 103) side. That is, one end of the diffuser 12 in the axial direction has the same diameter as the pipe 11, and is connected to the other end of the pipe 11. The diffuser 12 gradually expands in diameter from one end to the other end in the axial direction and is connected to the furnace wall 102. Note that the diffuser 12 is subjected to a recoil due to a shock wave caused by the detonation of the combustible gas G2 inside the diffuser 12, so the connection part of the diffuser 12 to the furnace wall 102 may be made movable.

The ejection section 13 ejects non-flammable gas G3 from the outer periphery of the diffuser 12 toward the center. The ejection section 13 is provided on the other end side of the diffuser 12, that is, on the furnace 101 (internal space 103) side.

The outer cylinder pipe 21 is disposed on the outside of the other end of the diverter 12. The outer cylinder pipe 21 has a cylindrical shape with a larger diameter than the diverter 12, and like the diverter 12, expands uniformly from one end to the other end in the axial direction. The inner circumferential surface of the outer cylinder pipe 21 is disposed with a gap from the outer circumferential surface of the diverter 12, and the outer circumferential surface is fitted and fixed in the through hole 102b of the furnace wall 102. Therefore, the other end side of the diverter 12 is disposed inside the furnace wall 102, and the entire outer cylinder pipe 21 is disposed inside the furnace wall 102. The outer cylinder pipe 21 may also be connected to the furnace wall 102 so as to be freely movable, like the diverter 12.

The outer tube 21 has an outer tube portion 21a and a flange portion 21b. The outer tube portion 21a is disposed with a gap from the outer peripheral surface of the expander tube 12. The flange portion 21b is disposed on the other axial end side of the outer tube 21, with its outer peripheral portion connected to the other end of the outer tube portion 21a and its inner peripheral portion connected to the other end of the expander tube 12. Therefore, a cylindrical gas flow portion 22 is formed between the expander tube 12 and the outer tube 21.

The header 23 is disposed on one end of the outer tube 21 in the axial direction. The header 23 is ring-shaped and has an L-shaped cross section. One end of the header 23 in the width direction is fixed to the outer wall surface 102c of the furnace wall 102, and the other end is fixed to the outer peripheral surface of the diffuser 12. Therefore, the header 23 defines a ring-shaped gas space 24 between the furnace wall 102 and the diffuser 12. The gas space 24 is connected to one end of the gas flow section 22. The header 23 may be connected to the furnace wall 102 in a freely movable manner, like the diffuser 12 and the outer tube 21. The header 23 may be fixed to the outer tube 21 to define the gas space 24.

The ejection section 13 has multiple (eight in this embodiment) ejection holes 31 that eject the non-flammable gas G3. The multiple ejection holes 31 are formed on the other axial end side of the expander tube 12, that is, on the side of the internal space 103 of the furnace 101. The multiple ejection holes 31 are slit-shaped openings along the circumferential direction of the expander tube 12. However, the number of ejection holes 31 is not limited. In addition, the ejection holes 31 are not limited to slit shapes, and may be circular holes.

The multiple ejection holes 31 constituting the ejection section 13 eject non-combustible gas G3 in an inclined direction inclined toward the internal space 103 of the furnace 101 with respect to the radial direction of the expander tube 12. That is, the expander tube 12 expands in diameter from one end toward the other end. The multiple ejection holes 31 are holes that penetrate in a direction perpendicular to the expanding other end of the expander tube 12. Therefore, the multiple ejection holes 31 eject non-combustible gas G3 from the outer periphery of the expander tube 12 toward the internal space 103.

The diffuser 12 is set to a predetermined expansion ratio. For example, when the inside diameter of one end of the diffuser 12 is R1 and the inside diameter of the other end of the diffuser 12 is R2, the area ratio is preferably set to (R2/2) ² π/(R1/2) ² π = 1.4 to 4.0. The angle α of the inner surface of the diffuser 12 with respect to the center line is preferably set to 10 degrees to 50 degrees. The ejection hole 31 is preferably set to an ejection angle β of the non-flammable gas G3 with respect to the radial direction of the diffuser 12 = 0 degrees to 45 degrees.

One end of a gas supply line 26 is connected to the header 23 via a port 25. A gas supply source 27 is connected to the other end of the gas supply line 26, and an on-off valve 28 is provided in the middle. Here, the gas supply source 27 is, for example, a blower or a compressor, and supplies air or compressed air as the non-flammable gas G3. However, the gas supply source 27 is not limited to this configuration. For example, the non-flammable gas G3 may be a gas with a lower oxygen fraction than air or an inert gas (such as nitrogen or argon) instead of air, and the gas supply source 27 may be a tank for storing these gases.

Therefore, when the on-off valve 28 is opened, non-flammable gas G3 is supplied from the gas supply source 27 to the gas supply line 26 and then supplied to the gas space portion 24 via the port 25. The non-flammable gas G3 supplied to the gas space portion 24 flows through the gas flow portion 22 to the other end side of the expansion tube 12 and is ejected from the multiple ejection holes 31 to the center side of the expansion tube 12.

<Function of the self-ignition prevention device>
When dust adheres to the inner wall surface 102a of the furnace wall 102 or the heat transfer tube (not shown) of the heat exchanger due to long-term use in the furnace 101, the dust removal device is operated. That is, the combustible gas G2 is supplied to the pipe 11 by the supply device to fill it, and the combustible gas G2 is ignited. Then, the combustible gas G2 burns inside the pipe 11 and generates a shock wave due to detonation. The generated shock wave is transmitted to the internal space 103 through the pipe 11 and the expansion tube 12, and acts on the inner wall surface 102a of the furnace wall 102 and the outer surface of the heat transfer tube, and the attached dust is blown off and removed. At this time, the shock wave due to the detonation generated in the pipe 11 is transmitted to the internal space 103 of the furnace 101 through the expanding expansion tube 12, so that the supersonic flow ejected together with the blast can be expanded at an appropriate area ratio to efficiently introduce the blast and jet into the internal space 103. When the dust removing device has removed the dust adhering to the inner wall surface 102a of the furnace wall 102 and the outer surfaces of the heat transfer tubes, the operation of the dust removing device is stopped.

When dust is removed by the dust removal device described above, the combustible gas G2 filled inside the pipe 11 and the expander tube 12 may spontaneously ignite. Therefore, when the dust removal device is operating, the spontaneous ignition prevention device 10 is operated. That is, the on-off valve 28 is opened, and non-combustible gas G3 is supplied from the gas supply source 27 to the gas space portion 24 through the gas supply line 26. Then, the non-combustible gas G3 filled in the gas space portion 24 flows through the gas flow portion 22 to the other end side of the expander tube 12 and is ejected from the multiple ejection holes 31 toward the center side of the expander tube 12.

At this time, the blowing section 13 blows non-flammable gas G3 from the multiple blowing holes 31 toward the center of the diffuser 12, forming an air curtain between the inside of the diffuser 12 and the internal space 103 of the furnace 101. The air curtain of non-flammable gas G3 separates the inside of the diffuser 12 from the internal space 103, so that, for example, the rising exhaust gas G1 is prevented from penetrating the internal space 103 into the inside of the diffuser 12. Therefore, spontaneous ignition of the combustible gas G2 filled in the piping 11 due to contact with the high-temperature exhaust gas G1 is prevented.

However, due to the flow velocity and drift of the exhaust gas G1 rising in the internal space 103, some of the exhaust gas G1 may slip through the air curtain of the non-flammable gas G3 and enter the diffuser 12. At this time, since the inner diameter (area) of the diffuser 12 on the furnace wall 102 side is larger than that on the piping 11 side, the exhaust gas G1 that has entered the diffuser 12 from the internal space 103 becomes a secondary flow F that swirls counterclockwise in FIG. 1 inside the diffuser 12. Therefore, the exhaust gas G1 that has entered the diffuser 12 becomes the secondary flow F and swirls and stagnates inside the diffuser 12, making it difficult to flow toward the piping 11 side, suppressing the spontaneous ignition of the combustible gas G2 filled in the piping 11.

In addition, even if a portion of the exhaust gas G1 that has entered the diffuser 12 comes into contact with the flammable gas G2 filling the piping 11, the temperature of the exhaust gas G1 drops as it flows through the diffuser 12. That is, the flammable gas G2 in the piping 11 is mixed with the exhaust gas G1, which has been cooled, and is diluted, so that the concentration of the flammable gas G2 in the piping 11 drops without spontaneous ignition. Therefore, even if the mixed gas of the flammable gas G2 and the exhaust gas G1 returns to the internal space 103 through the diffuser 12, spontaneous ignition of the flammable gas G2 is suppressed.

In the above description, the self-ignition prevention device 10 is configured to operate when the dust removal device removes dust adhering to the inner wall surface 102a of the furnace wall 102 or the outer surface of the heat transfer tube, but this configuration is not limited to this. The self-ignition prevention device 10 may be kept operating at all times.

[Second embodiment]
3 is a cross-sectional view of a furnace showing a self-ignition prevention device according to a second embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed description thereof will be omitted.

In the second embodiment, as shown in FIG. 3, the self-ignition prevention device 10A includes a pipe 11, an expansion pipe 12, and an ejection section 13A.

The expansion pipe 12 is provided between the pipe 11 and the internal space 103 of the furnace 101. The expansion pipe 12 has one end with the same diameter as the pipe 11, is connected to the other end of the pipe 11, and the diameter gradually expands toward the other end, and is connected to the furnace wall 102. The ejection section 13A ejects non-combustible gases G3 and G4 from the outer periphery of the expansion pipe 12 toward the center. The ejection section 13 has a plurality of first ejection holes 31 and a plurality of second ejection holes 32. The first ejection holes 31 are provided on the furnace 101 (internal space 103) side of the expansion pipe 12, and eject non-combustible gas G3. The second ejection holes 32 are provided on the pipe 11 side of the expansion pipe 12, and eject non-combustible gas G4. The multiple first and second nozzles 31 and 32 that make up the nozzle section 13 spray non-flammable gas G3 in a direction that is inclined toward the internal space 103 of the furnace 101 relative to the radial direction of the expansion pipe 12.

An outer tube 21 is disposed on the outside of the other end of the expander 12, and a cylindrical gas flow section 22 is formed between the expander 12 and the outer tube 21. A header 23 is disposed on one axial end of the outer tube 21. The header 23 defines a gas space section 24 that communicates with the gas flow section 22 and the second ejection hole 32. The header 23 is connected to one end of a gas supply line 26 via a port 25. The gas supply line 26 is connected to a gas supply source 27 at the other end, and an opening/closing valve 28 is provided midway.

Therefore, when the self-ignition prevention device 10 is operated, non-flammable gas G3 is supplied from the gas supply line 26 to the gas space 24 and is ejected from the multiple second ejection holes 32 toward the center of the expander tube 12. In addition, non-flammable gas G3 flows from the gas space 24 through the gas flow section 22 toward the other end of the expander tube 12 and is ejected from the multiple first ejection holes 31 toward the center of the expander tube 12.

At this time, the first nozzle 31 ejects non-combustible gas G3 toward the center at the other end of the diffuser 12, forming an air curtain between the inside of the diffuser 12 and the internal space 103 of the furnace 101. Also, the second nozzle 32 ejects non-combustible gas G4 toward the center at one end of the diffuser 12, forming an air curtain between the inside of the diffuser 12 and the inside of the piping 11. The two air curtains of non-combustible gas G3 separate the inside of the piping 11, the inside of the diffuser 12, and the internal space 103. The air curtain of non-combustible gas G3 separates the inside of the diffuser 12 from the internal space 103. Also, the air curtain of non-combustible gas G4 separates the inside of the piping 11 from the internal space 103 of the diffuser 12. Then, the air curtain of non-combustible gas G3 prevents the exhaust gas G1 rising in the internal space 103 from penetrating into the inside of the diffuser 12. In addition, the air curtain of non-flammable gas G4 prevents the flammable gas G2 in the pipe 11 from penetrating into the diffuser 12. Therefore, spontaneous ignition of the flammable gas G2 filled in the pipe 11 by the exhaust gas G1 is suppressed.

In the above description, the ejection section 13 is provided with the first ejection hole 31 and the second ejection hole 32, but is not limited to this configuration. For example, the ejection section 13 may be configured with only the second ejection hole 32.

[Third embodiment]
Fig. 4 is a cross-sectional view of a furnace showing the self-ignition prevention device of the third embodiment, and Fig. 5 is a front view of the self-ignition prevention device from the furnace side. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions are omitted.

In the third embodiment, as shown in Figures 4 and 5, the self-ignition prevention device 10B includes a pipe 11, an expansion pipe 12, and an ejection section 13B.

The expansion pipe 12 is provided between the pipe 11 and the internal space 103 of the furnace 101. The expansion pipe 12 has one end with the same diameter as the pipe 11, is connected to the other end of the pipe 11, and the diameter gradually increases toward the other end, and is connected to the furnace wall 102. The ejection section 13B ejects non-combustible gases G3a and G3b from the outer periphery of the expansion pipe 12 toward the center. The ejection section 13B has a plurality of upstream ejection holes (upstream ejection section) 31a and a plurality of downstream ejection holes (downstream ejection section) 31b. The upstream ejection holes 31a and the downstream ejection holes 31b are provided on the furnace 101 side of the expansion pipe 12, and eject non-combustible gases G3a and G3b, respectively.

The upstream ejection holes 31a are arranged on the upstream side (lower side in FIG. 4) of the flow direction of the exhaust gas G1 rising in the internal space 103 of the furnace 101. The downstream ejection holes 31b are arranged on the downstream side (upper side in FIG. 4) of the flow direction of the exhaust gas G1 rising in the internal space 103 of the furnace 101. In this embodiment, the upstream ejection holes 31a are arranged in four on the lower side of the expansion pipe 12, and the downstream ejection holes 31b are arranged in four on the upper side of the expansion pipe 12, but the number is not limited and does not have to be the same. The amount of non-combustible gas G3b ejected from the downstream ejection holes 31b is greater than the amount of non-combustible gas G3a ejected from the upstream ejection holes 31a. Specifically, it is preferable to set the deviation in the dynamic pressure of the air curtain, which is the deviation in the flow rates of the non-flammable gases G3a and G3b, in the internal space 103 to, for example, 0.5 times or more the dynamic pressure of the rising exhaust gas G1.

The outer tube 21 is disposed on the outside of the other end of the expanding pipe 12, and cylindrical gas flow sections 22a, 22b are formed between the expanding pipe 12 and the outer tube 21. The outer tube 21 is provided with partition plates 21c on both horizontal inner surfaces, which divide the lower gas flow section 22a and the upper gas flow section 22b. The outer tube 21 is also provided with a header 23 at one axial end. The header 23 divides gas space sections 24a, 24b that communicate with the gas flow sections 22a, 22b. The header 23 is provided with partition plates (not shown) on both horizontal inner surfaces, which divide the lower gas space section 24a and the upper gas space section 24b. The gas flow section 22a communicates with the gas space section 24a, and the gas flow section 22b communicates with the gas space section 24b. One end of a gas supply line 26a is connected to the header 23 via a port 25a that communicates with the gas space portion 24a, and the other end is connected to a gas supply source 27. One end of a gas supply line 26b is connected to the header 23 via a port 25b that communicates with the gas space portion 24b, and the other end is connected to the gas supply source 27. Opening and closing valves 28a and 28b are provided in the middle of the gas supply lines 26a and 26b. The opening and closing valves 28a and 28b are flow rate adjustment valves.

Therefore, when the self-ignition prevention device 10 is operated, the non-flammable gases G3a and G3b are supplied from the gas supply lines 26a and 26b to the gas space portions 24a and 24b, and flow through the gas flow portions 22a and 22b to the other end side of the expansion tube 12. Then, the non-flammable gas G3a is ejected from the multiple upstream ejection holes 31a toward the center side of the expansion tube 12, and the non-flammable gas G3b is ejected from the multiple downstream ejection holes 31b toward the center side of the expansion tube 12.

That is, the upstream nozzle 31a ejects non-combustible gas G3a along the exhaust gas G1 rising in the internal space 103, and the downstream nozzle 31b ejects non-combustible gas G3a opposite the exhaust gas G1 rising in the internal space 103. At this time, the opening of the opening/closing valves 28a, 28b is adjusted so that the amount of non-combustible gas G3b ejected from the downstream nozzle 31b is greater than the amount of non-combustible gas G3a ejected from the upstream nozzle 31a.

Due to flow speed and drift, some of the exhaust gas G1 rising in the internal space 103 may slip through the air curtain of the non-combustible gas G3 and enter the diffuser 12. The exhaust gas G1 that enters the diffuser 12 from the internal space 103 becomes a secondary flow F that rotates counterclockwise in FIG. 4 within the diffuser 12. Here, the downstream ejection hole 31b ejects a large amount of non-combustible gas G3b so as to face the flow of the exhaust gas G1 entering the diffuser 12 from the internal space 103. Therefore, the large amount of non-combustible gas G3b obstructs the flow of the exhaust gas G1 entering the diffuser 12 from the internal space 103, suppressing the intrusion of the exhaust gas G1 into the diffuser 12, and suppressing the spontaneous ignition of the combustible gas G2 filled in the piping 11.

In the above description, multiple upstream ejection holes 31a and multiple downstream ejection holes 31b are provided as the ejection section 13B, and the ejection amounts of non-flammable gas G3a from the upstream ejection holes 31a and non-flammable gas G3b from the downstream ejection holes 31b are different, but this configuration is not limited to this. For example, the types of ejection holes that have different ejection amounts are not limited to two types, and may be three or more types.

[Fourth embodiment]
6 is a cross-sectional view of a furnace showing a self-ignition prevention device according to a fourth embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed description thereof will be omitted.

In the fourth embodiment, as shown in FIG. 6, the self-ignition prevention device 10C includes a pipe 11, an expansion pipe 12, and a blowing unit 13. The self-ignition prevention device 10C can adjust the flow rate of the non-flammable gas G3 sprayed by the blowing unit 13 depending on the properties of the flammable gas G2. Here, the properties of the flammable gas G2 refer to, for example, the flow rate of the flammable gas G2 flowing through the pipe 11.

The piping 11 is provided with a flow sensor 41 that measures the flow rate of the flammable gas G2 inside. The control unit 42 adjusts the opening of the on-off valve 28 based on the flow rate of the flammable gas G2 detected by the flow sensor 41. The control unit 42 adjusts the opening of the on-off valve 28 to a larger value as the flow rate of the flammable gas G2 flowing through the piping 11 increases. In other words, the greater the flow rate of the flammable gas G2 flowing through the piping 11, the greater the flow rate of the non-flammable gas G3 sprayed from the multiple ejection holes 31 by the ejection unit 13.

In the above description, the detection unit that detects the properties of the combustible gas G2 is not limited to the flow sensor 41. As a detection unit that detects the properties of the combustible gas G2, such as the flow rate and concentration, a speed sensor that detects the flow rate of the combustible gas G2, a concentration sensor that detects the concentration of the combustible gas G2, a supply amount setting value or valve opening sensor in the supply device of the combustible gas G2, a sampling measurement device for the combustible gas G2, a laser instrumentation device, etc. may be applied. In addition, a map in which the injection amount of the non-combustible gas G3 relative to the supply amount setting value in the supply device of the combustible gas G2 is set may be prepared in advance, and the opening of the opening valve 28 may be adjusted based on the map.

[Fifth embodiment]
7 is a cross-sectional view of a furnace showing a self-ignition prevention device according to a fifth embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed description thereof will be omitted.

In the fifth embodiment, as shown in FIG. 7, the self-ignition prevention device 10D includes a pipe 11, an expansion pipe 12, and an ejection unit 13. The self-ignition prevention device 10C can adjust the flow rate of the non-flammable gas G3 ejected by the ejection unit 13 depending on the properties of the exhaust gas G1. Here, the properties of the exhaust gas G1 are, for example, the temperature of the exhaust gas G1 entering the pipe 11.

The expander 12 is provided with a temperature sensor 43 inside that measures the temperature of the exhaust gas G1. The control unit 42 adjusts the opening of the on-off valve 28 based on the temperature of the exhaust gas G1 detected by the temperature sensor 43. The control unit 42 adjusts the opening of the on-off valve 28 to a larger degree as the temperature of the exhaust gas G1 that has entered the expander 12 increases. In other words, the higher the temperature of the exhaust gas G1 that has entered the expander 12, the more the ejection unit 13 increases the flow rate of the non-flammable gas G3 that is ejected from the multiple ejection holes 31.

In the above description, the detection unit for detecting the properties of the exhaust gas G1 is not limited to the temperature sensor 43. As the detection unit for detecting the properties of the exhaust gas G1, a temperature sensor for detecting the temperature of the inner circumferential surface of the diffuser 12, a temperature sensor for detecting the temperature of the exhaust gas G1 rising in the internal space 103, a temperature sensor for detecting the temperature of the inner wall surface 102a of the furnace wall 102, a flow rate sensor (velocity sensor) for detecting the flow rate (flow rate) of the exhaust gas G1 that has entered the diffuser 12, etc. may be applied. In addition, a map in which the injection amount of the non-combustible gas G3 relative to the temperature of the exhaust gas G1 that has entered the diffuser 12 is set may be prepared in advance, and the opening degree of the opening valve 28 may be adjusted based on the map. In addition, the opening degree of the opening valve 28 may be adjusted by performing PID control based on the detected properties of the exhaust gas G1.

[Effects of this embodiment]
The spontaneous ignition prevention device according to the first aspect includes a pipe 11 that can be filled with a combustible gas G2 and can communicate with an internal space (target area) 103 of a furnace 101, an expansion pipe 12 that is provided between the pipe 11 and a furnace wall 102 (internal space 103) and has an inner diameter larger than the inner diameter of the pipe 11, and ejection parts 13, 13A, 13B that eject a non-combustible gas G3 from the outer periphery of the expansion pipe 12 toward the center.

According to the spontaneous ignition prevention device of the first aspect, when the piping 11 is filled with flammable gas G2, the ejection parts 13A and 13B eject non-flammable gas G3 from the outer periphery of the diffuser 12 toward the center, forming an air curtain between the diffuser 12 and the internal space 103 of the furnace 101. The air curtain of non-flammable gas G3 separates the inside of the diffuser 12 from the internal space 103, thereby suppressing the intrusion of exhaust gas G1 into the inside of the diffuser 12 and suppressing spontaneous ignition of the flammable gas G2 filled in the piping 11 by the exhaust gas G1.

In addition, there is a risk that part of the exhaust gas G1 will slip through the air curtain of the non-flammable gas G3 and enter the inside of the diffuser 12. This exhaust gas G1 will form a secondary flow F that swirls inside the diffuser 12 and will stagnate inside the diffuser 12. As a result, the exhaust gas G1 will be less likely to flow toward the pipe 11, which will suppress spontaneous ignition of the flammable gas G2 filled in the pipe 11.

Furthermore, even if a portion of the exhaust gas G1 that has entered the expanding tube 12 comes into contact with the flammable gas G2 filled in the piping 11, the flammable gas G2 is diluted by being mixed with the exhaust gas G1 whose temperature has been reduced, and the concentration of the flammable gas G2 decreases. Therefore, even if the flammable gas G2 diluted by being mixed with the exhaust gas G1 returns to the internal space 103 through the expanding tube 12, spontaneous ignition of the flammable gas G2 can be suppressed.

As a result, large valves and the like are not required, and increases in parts costs and maintenance costs can be suppressed. In addition, the air curtain for non-flammable gas G3 that separates the expander 12 from the internal space 103 can be achieved by simply providing the outlet 13 on the expander 12, and there is no risk of malfunction even when placed in a high-temperature environment, and spontaneous ignition of the flammable gas G2 can be appropriately suppressed.

In the second embodiment of the self-ignition prevention device, the expansion pipe 12 expands continuously from the pipe 11 toward the internal space 103. As a result, the inner surface of the expansion pipe 12 expands without any steps, so that the exhaust gas G1 that has entered the expansion pipe 12 can be appropriately swirled and turned into a stagnant secondary flow F, thereby suppressing the self-ignition of the flammable gas G2 filled in the pipe 11.

In the third embodiment of the self-ignition prevention device, the ejection parts 13, 13A, and 13B eject non-flammable gas G3 in an inclined direction inclined toward the internal space 103 with respect to the radial direction of the diffuser 12. This forms an air curtain of non-flammable gas G3 that protrudes toward the internal space 103, effectively preventing the intrusion of exhaust gas G1 from the internal space 103 into the diffuser 12 and piping 11.

In the fourth aspect of the self-ignition prevention device, the blowing portion 13 is provided on the internal space 103 side of the diffuser 12. This allows the air curtain of non-flammable gas G3 to appropriately suppress the intrusion of exhaust gas G1 from the internal space 103 into the diffuser 12.

In the fifth aspect of the self-ignition prevention device, the blowing section 13A is provided on the piping 11 side of the diffuser 12. This allows the air curtain of non-flammable gas G3 to appropriately suppress the intrusion of exhaust gas G1 from the diffuser 12 into the piping 11.

The self-ignition prevention device according to the sixth aspect has an upstream nozzle (upstream nozzle) 31a arranged upstream in the flow direction of the exhaust gas G1 flowing through the internal space 103, and a downstream nozzle (downstream nozzle) 31b arranged downstream in the flow direction of the exhaust gas G1 in the internal space 103, as the nozzle 13B, and the amount of non-combustible gas G3b emitted from the downstream nozzle 31b is greater than the amount of non-combustible gas G3a emitted from the upstream nozzle 31a. As a result, a large amount of non-combustible gas G3b emitted from the downstream nozzle 31b faces the flow of the exhaust gas G1 attempting to enter the internal space 103, and the intrusion of the exhaust gas G1 from the internal space 103 into the expansion pipe 12 and the piping 11 can be appropriately suppressed.

The seventh aspect of the self-ignition prevention device sets the flow rate of the non-flammable gas G3 ejected from the ejection parts 13, 13A, and 13B according to the properties of the flammable gas G2. This allows the flow rate of the non-flammable gas G3 to be set according to the flow rate, concentration, and other properties of the flammable gas G2, and therefore the air curtain of the non-flammable gas G3 can appropriately suppress the intrusion of the exhaust gas G1 from the internal space 103 into the expansion pipe 12 and piping 11.

The self-ignition prevention device according to the eighth aspect sets the flow rate of the non-flammable gas G3 ejected from the ejection parts 13, 13A, 13B according to the properties of the exhaust gas G1 in the internal space 103. This allows the flow rate of the non-flammable gas G3 to be set according to the properties of the exhaust gas G1, such as the temperature and flow rate, and therefore the air curtain of the non-flammable gas G3 can appropriately suppress the intrusion of the exhaust gas G1 from the internal space 103 into the expansion pipe 12 and the piping 11.

In the above embodiment, the expansion pipe 12 is configured to expand continuously and uniformly from one end connected to the pipe 11 to the other end connected to the furnace 101, but this is not limited to the configuration. For example, the expansion pipe 12 may be configured to expand discontinuously in stages from one end to the other end.

In the above-described embodiment, the spontaneous ignition prevention devices 10, 10A, 10B, 10C, and 10D are applied to dust removal devices such as waste incinerators, integrated coal gasification combined cycle power generation facilities, and power generation boilers, but they can also be applied to various plants that handle flammable gas G2.

REFERENCE SIGNS LIST 10, 10A, 10B, 10C, 10D Self-ignition prevention device 11 Pipe 12 Expander 13, 13A, 13B Jet section 21 Outer cylinder pipe 22, 22a, 22b Gas flow section 23 Header 24, 24a, 24b Gas space section 25, 25a, 25b Port 26, 26a, 26b Gas supply line 27 Gas supply source 28, 28a, 28b Opening/closing valve 31 Jet hole, first jet hole 32 Second jet hole 31a Upstream jet hole 31b Downstream jet hole 41 Flow rate sensor 42 Control unit 43 Temperature sensor 101 Furnace 102 Furnace wall 103 Internal space (target area)
G1 Exhaust gas G2 Combustible gas G3, G3a, G3b, G4 Non-combustible gas F Secondary flow

Claims (8)

A spontaneous ignition prevention device applied to a dust removal device that removes dust attached to the inner wall of a furnace or the outer surface of a heat transfer tube,
A pipe capable of being filled with a flammable gas and being connected to a target area;
an expansion pipe provided between the pipe and the target area and having an inner diameter larger than an inner diameter of the pipe;
a blowout section that blows out a non-flammable gas from an outer periphery of the diffuser toward a center portion of the diffuser to form an air curtain ;
Equipped with
The air curtain separates the expansion tube from the target area .
Self-ignition prevention device. The expansion pipe continuously expands in diameter from the pipe toward the target area.
The autoignition prevention device according to claim 1 . The ejection section ejects the non-flammable gas in an inclined direction inclined toward the target area with respect to a radial direction of the diffuser.
The self-ignition prevention device according to claim 1 or 2. The ejection portion is provided on the target area side of the diffuser.
The self-ignition prevention device according to any one of claims 1 to 3. The jetting portion is provided on the piping side of the diffuser.
The self-ignition prevention device according to any one of claims 1 to 4. The ejection section has an upstream ejection section arranged on the upstream side of the flow direction of the gas flowing through the target area, and a downstream ejection section arranged on the downstream side of the flow direction of the gas in the target area, and an ejection amount of the non-combustible gas from the downstream ejection section is greater than an ejection amount of the non-combustible gas from the upstream ejection section.
The self-ignition prevention device according to any one of claims 1 to 5. The flow rate of the non-combustible gas ejected from the ejection portion is set according to the properties of the flammable gas.
The self-ignition prevention device according to any one of claims 1 to 6. The flow rate of the non-flammable gas ejected from the ejection portion is set according to the properties of the gas flowing through the target area.
The self-ignition prevention device according to any one of claims 1 to 7.

Images