JP2015068505A - Ground flare - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an influence on surroundings due to low frequency vibration, with simpler means than conventional one.SOLUTION: A ground flare A includes: a windshield 2 provided upright on a ground with an upper end thereof being open; an air introduction section 3 through which combustion air can pass; a stack 4 provided upright on the air introduction section 3; and burners 5 provided within the stack 4. The ground flare A includes a plurality of acoustic pressure release holes 4a arranged in regions corresponding to a loop of a stationary wave of vibration generated in the windshield 2 and the stack 4, in a height direction of the windshield 2 or the stack 4, and for releasing an acoustic pressure to outside.

Description

  The present invention relates to a ground flare.

  In Patent Document 1 below, combustible exhaust gas is burned with a burner at the bottom of the chimney, and a low frequency generated from a ground flare tower composed of the chimney and the windshield in a ground flare surrounded by a windshield at the bottom of the chimney and the burner. Select at least one of the change of the natural frequency of vibration (acoustic vibration), multiple ground flare towers, and installation of low frequency vibration absorbers inside the ground flare tower. Reducing the frequency noise sound pressure level is disclosed.

  Further, in this Patent Document 1, as a specific means for realizing the above-described change of the natural frequency, that is, higher frequency of the low-frequency vibration, “Sound pressure mode generated by the resonance frequency in the height direction of the chimney” It is described that an opening (chimney opening) is provided at a position that becomes an “abdomen”. That is, the technique described in Patent Document 1 is a modification of the natural frequency of low-frequency vibration generated from a ground flare tower composed of a chimney and a windshield, that is, the low-frequency vibration is higher in frequency than the original natural frequency of the chimney. By shifting to, the surrounding objects are prevented from resonating and vibrating due to low frequency vibration.

JP 2010-156508 A

  By the way, in the above prior art, a comparatively wide range (90 ° to 360 °) in the circumferential direction of the chimney is compared with the position that becomes the “antinode” of the sound pressure mode in order to shift the frequency of the low frequency vibration to a high frequency. A chimney opening with a large opening area ratio (25% or more) is provided.

  However, since it is necessary to secure the mechanical strength of the chimney, the range and the opening area ratio of the chimney opening in the circumferential direction are naturally limited. For example, when applying the above prior art to an existing ground flare, in order to obtain a sufficient range or sufficient opening area ratio for the chimney opening, or to obtain a sufficient range or sufficient opening area ratio May require reinforcement of the chimney.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to reduce the influence on the surroundings due to low-frequency vibrations with simpler means than before.

  In order to achieve the above object, in the present invention, as a first solving means, a burner, a chimney erected so that the burner is located above or in the middle of the burner, a side of the burner or the A ground flare comprising at least a windshield that surrounds the lower end of the chimney, and corresponds to an antinode of a standing wave of acoustic vibration generated in the chimney and the windshield in the height direction of the chimney or the windshield. A means is adopted in which an opening for escaping the sound pressure to the outside is provided at the part to be operated.

  According to the present invention, as the second solving means, in the first solving means, the opening has the chimney and the windshield with the sum of the height of the chimney and the height of the windshield and the both ends. Is taken as a single open tube and is provided at a portion corresponding to the antinode of the standing wave of the acoustic vibration generated in the open tube.

  In the present invention, as a third solution, in the second solution, the portion corresponding to the antinode of the standing wave has an effective tube length obtained by performing open end correction on the open tube. The method of being set based on is adopted.

  In the present invention, as a fourth solving means, in any one of the first to third solving means, the opening corresponds to the antinode of the standing wave, and the opening is located around the chimney or the windshield. A means of providing a plurality of discretely in the direction is adopted.

  In the present invention, as a fifth solving means, in any one of the first to fourth solving means, in addition to a portion corresponding to the antinode of the standing wave in the height direction of the chimney or the windshield. Thus, a means of providing an auxiliary opening at a part away from the part by a certain distance is adopted.

  According to the present invention, the opening corresponding to the antinode of the standing wave of the acoustic vibration generated in the chimney and the windshield is provided with the opening for releasing the sound pressure to the outside. Therefore, the aperture area ratio can be reduced as compared with the opening for the purpose, and therefore the influence on the surroundings due to the acoustic vibration can be reduced by a simpler means than conventional.

It is a vertical sectional view showing the composition of ground flare A concerning one embodiment of the present invention. It is a horizontal sectional view showing the composition of ground flare A concerning one embodiment of the present invention. It is a schematic diagram which shows the sound field of the low frequency vibration (acoustic vibration) in the ground flare A which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The ground flare A according to the present embodiment is a facility for performing a combustion process on a combustible gas generated excessively in a plant as a processing target. The ground flare A is provided in, for example, an LNG base, and burns BOG gas (boil-off gas) inevitably generated in the LNG tank.

  1 and 2, the ground flare A includes a foundation 1, a windshield 2, an air introduction unit 3, a chimney 4, a plurality of burners 5, a supply pipe 6, a first control valve 7, and a second control. At least a valve 8, a third control valve 9, and a pilot burner 10 are provided. The windshield 2 is generally called a “fence”, and the chimney 4 is also called a “stack”.

  The foundation 1 is a concrete structure constructed on the ground such that the upper surface is a horizontal plane. The windshield 2 is a cylindrical body erected on the ground with the upper end open. More specifically, the windshield 2 is a cylindrical body that is installed on the foundation 1 in a vertical state with no gap between the windshield 2 and the upper surface of the foundation 1. Further, the lower end of the windshield 2 is in contact with the upper surface of the foundation 1 all around, but the upper end of the windshield 2 is completely open.

  The air introduction part 3 is a substantially cylindrical opening constructed concentrically with the windshield 2 inside the windshield 2. For example, the air introduction part 3 is comprised by the several support | pillar arrange | positioned at predetermined intervals at the annular | circular shape, it is for combustion over the predetermined height from the upper surface of the foundation 1, and substantially the perimeter. Air can pass freely.

  The chimney 4 is a cylindrical body provided on the air introduction part 3 in a vertical posture. The chimney 4 has the same diameter as the air introduction part 3 and has a predetermined length. The length (height) of the chimney 4 is set so that the flame generated in the plurality of burners 5 cannot be visually recognized from the outside, that is, the upper end of the chimney 4 is higher than the upper end of the flame.

  A plurality of burners 5 are provided in the chimney 4 and at a position (horizontal position) slightly higher than the upper end of the air introduction part 3 in the chimney 4 with a predetermined interval. Such a plurality of burners 5 are taken into the windshield 2 from the upper end of the windshield 2, and further, the combustion air taken into the chimney 4 through the air introduction part 3 is used as an oxidant to combustible gas ( To be treated.

  The supply pipe 6 is a pipe that supplies a plurality of burners 5 with a combustible gas (processing target). The supply pipe 6 passes through the windshield 2 and is drawn into the windshield 2 and is further drawn into the chimney 4 through the air introduction part 3. However, as shown in FIG. Thus, the first branch pipe 6a, the second branch pipe 6b, and the third branch pipe 6c are branched into the windshield 2.

  A plurality of burners 5a constituting the first group (first stage) are connected to the tip of the first branch pipe 6a, and a plurality of burners 5a constituting the second group (second stage) are connected to the tip of the second branch pipe 6b. A burner 5b is connected, and a plurality of burners 5c constituting a third group (third stage) are connected to the tip of the third branch pipe 6c. In FIG. 2, the windshield 2 is omitted for convenience.

  The supply pipe 6 is provided with a first control valve 7, the second branch pipe 6b is provided with a second control valve 8, and the third branch pipe 6c is provided with a third control valve 9. Yes. The first control valve 7 is set to an open state when a combustible gas needs to be combusted in the ground flare A, and is set to a closed state when a combustible gas treatment is not required in the ground flare A. Is done.

  The 2nd control valve 8 and the 3rd control valve 9 are control valves opened and closed according to the quantity of combustible gas processed with grand flare A. That is, the second control valve 8 and the third control valve 9 are closed when the amount of combustible gas is relatively small, and are opened when the amount of combustible gas increases. The first control valve 7, the second control valve 8, and the third control valve 9 are controlled to be opened and closed by a control device (plant control device) that controls the operation of the plant.

  The pilot burner 10 is an ignition dedicated burner provided separately to ignite the first stage burner 5a, and is provided in the vicinity of the burner 5a. The second stage burner 5b and the third stage burner 5c are not provided with an ignition dedicated burner. The ignition of the burner 5b of the second stage and the burner 5c of the third stage is started by supplying the combustible gas (processing target) to the burner 5b of the second stage and the burner 5c of the third stage. This is done by the flame of the first stage burner 5a being burned out. The pilot burner 10 is also controlled by the plant control device.

  Further, the characteristic configuration of the ground flare A will be described. The chimney 4 has a low-frequency vibration in order to reduce low-frequency vibration (acoustic vibration) generated when the windshield 2 and the chimney 4 resonate. A sound pressure relief hole 4a (opening) for letting out the sound pressure to the outside is formed. The low-frequency vibration resonates at the natural frequency of the windshield 2 and the chimney 4 where the combustion sound generated by the plurality of burners 5 is a main sound source and the windshield 2 and the chimney 4 can be regarded as one open tube B as a whole. Is an acoustic vibration generated by

  As shown in FIG. 3, the open tube B composed of the windshield 2 and the chimney 4 has both ends of the chimney 4 with reference to the foundation 1 as well as the height H1 of the windshield 2 with reference to the foundation 1. It is a sound field having the pipe length as the sum of the height H2. That is, the open tube B has a shape obtained by folding the windshield 2 on the upper surface of the foundation 1. In such an open tube B (sound field), when the open tube B (sound field) resonates, a standing wave of a fundamental wave having a tube length of half wavelength and “nodes” at both ends is generated. To do.

  Here, in the open tube B (sound field), harmonic standing waves can be generated in addition to the fundamental standing wave. However, the low-frequency vibration having the greatest influence on the surrounding environment is the fundamental wave, and thus the sound pressure relief hole 4a is located in the height direction of the chimney 4 at a position corresponding to the “antinode” of the standing wave of the fundamental wave ( Part). For example, when the height H1 is 10 m and the height H2 is 30 m, the harmonic frequency is about 4 Hz. Although such extremely low frequency vibrations are out of the audible range, they have the greatest impact on the surrounding environment and are required to be reduced.

  The sound pressure relief holes 4 a are provided in a discrete manner in the circumferential direction of the chimney 4. For example, the intervals of the sound pressure relief holes 4a in the circumferential direction of the chimney 4 are not different locally but are constant intervals. Furthermore, the plurality of sound pressure relief holes 4a arranged in the circumferential direction of the chimney 4 are all the same shape and the same size, and are not different shapes or different sizes. When a plurality of sound pressure relief holes 4 a are provided in the circumferential direction of the chimney 4, the mechanical strength of the portion of the chimney 4 where the sound pressure relief holes 4 a are annularly lowered is reduced, so that the sound pressure relief holes 4 a About a shape, the shape (for example, circular shape) which suppresses the fall of the said mechanical strength as much as possible is preferable.

Next, functions and effects of the present ground flare A will be described in detail.
In the present ground flare A, when a combustible gas combustion process is required, the first control valve 7 is set from the closed state to the open state by the plant control device, and the pilot burner 10 is operated by the plant control device. As a result, the burner 5a of the first stage is worn. When the amount of combustible gas is relatively large, the plant control device sets the second control valve 8 and the third control valve 9 to the open state in addition to the first control valve 7, and the second stage. The burner 5b and the third stage burner 5c are also ignited.

  Thus, when this grand flare A starts operation, the plurality of burners 5 burn the combustible gas (processing target) using the combustion air taken from the outside air through the air introduction unit 3 as an oxidant. However, noise (combustion noise) is generated in the chimney 4 with this combustion. Then, mainly due to this combustion noise, the windshield 2 and the chimney 4 resonate at their own natural frequencies and emit low frequency vibrations.

  Here, as described above, the windshield 2 and the chimney 4 are the sum of the height H1 of the windshield 2 with respect to the foundation 1 and the height H2 of the chimney 4 with reference to the foundation 1 when viewed as a vibrating body. Can be regarded as a single open tube B having a tube length. Since this open tube B is composed of the windshield 2 and the chimney 4 having different diameters, more accurately, it is an open tube whose thickness changes along the way, but this change in thickness is the wavelength of the low frequency vibration ( The frequency (frequency) of the low-frequency vibration mainly depends on the tube length of the open tube B.

  In more detail, since the open tube B is open at both ends, unlike the closed tube, the open tube correction is performed for each open end, so that the actual tube length of the open tube B is slightly shorter than the actual tube length. It is necessary to estimate the wavelength (frequency) of the low frequency vibration based on the tube length. Such an open end correction amount is obtained by multiplying the open end radius of the open tube B by, for example, 0.6. Since the open end correction depends on the pipe diameter as is well known, the lower end of the open pipe B corresponding to the upper end of the windshield 2 is corrected based on the radius of the windshield 2, while the chimney On the upper end of the open tube B corresponding to the upper end of 4, an open end correction is performed based on the radius of the chimney 4.

  In such an open tube B, as shown in the schematic diagram on the right side of FIG. 3, an acoustic standing wave (wavelength (frequency) based on the above-described effective tube length) and both ends that are open ends become “nodes” ( A fundamental wave is generated. And in this grand flare A, in the height direction of the open tube B (the height direction of the windshield 2 and the chimney 4), at the position (height) corresponding to the “antinode” of the acoustic standing wave (fundamental wave). A plurality of sound pressure relief holes 4a are formed in a tubular shape.

  In the acoustic standing wave (fundamental wave), “antinode” is a portion where the sound pressure level is the highest, while “node” is a portion where the sound pressure level is the lowest. Since the plurality of sound pressure relief holes 4a are open, the sound pressure is released from the “abdomen” of the acoustic standing wave (fundamental wave) where the sound pressure level is maximized to the outside of the open tube B (outside the chimney 4). That is, the sound pressure of the acoustic standing wave (fundamental wave) in the “antinode” is lowered to lower the vibration level of the low frequency vibration.

  That is, according to this grand flare A provided with such a plurality of sound pressure relief holes 4a, the sound pressure is not increased from the open tube B (the chimney 4 of the chimney 4), instead of increasing the frequency of the low frequency vibration as in the prior art. Since the vibration level of the low-frequency vibration is lowered by letting it escape to the outside, the opening area ratio of the sound pressure relief hole 4a can be made smaller than in the prior art. Therefore, according to the present ground flare A, the necessity for the reinforcement process of the chimney 4 is also reduced, so that the influence on the surroundings due to the low frequency vibration can be reduced by a simpler means than before.

In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, a plurality of sound pressure reliefs are provided along the circumferential direction of the chimney 4 only at a position (height) corresponding to the “antinode” of the acoustic standing wave (fundamental wave) generated in the open tube B. Hole 4a was provided. However, since the sound pressure level of the acoustic standing wave (fundamental wave) gradually decreases as the distance from the “abdomen” increases in the height direction of the open tube B, the sound pressure level of the acoustic standing wave (the fundamental wave) A sound pressure relief hole may be provided as an auxiliary opening. For example, there are a plurality of locations along the circumferential direction of the chimney 4 at two upper and lower positions sandwiching a portion corresponding to the “belly” in the height direction of the open tube B, both in the upper and lower vicinity away from the “belly” by a certain distance. It is conceivable to provide an auxiliary opening.

(2) In the above embodiment, the position (height) corresponding to the “antinode” of the acoustic standing wave (fundamental wave) generated in the open tube B is the position corresponding to the chimney 4, so Although the sound pressure relief hole 4a is provided, the present invention is not limited to this. For example, when the height of the windshield 2 is higher than the height of the chimney 4, the position (height) corresponding to the “antinode” of the acoustic standing wave (fundamental wave) may be a position corresponding to the windshield 2. Therefore, in such a case, the sound pressure relief hole is formed in the windshield 2.

(3) In the above embodiment, a plurality of sound pressure relief holes 4 a are formed along the circumferential direction of the chimney 4 at a position (height) corresponding to the “antinode” of the acoustic standing wave (fundamental wave) generated in the open tube B. However, the present invention is not limited to this. The sound pressure relief hole 4 a may be provided as a single long hole that continuously extends along the circumferential direction of the chimney 4.

(4) In the above embodiment, the plurality of burners 5 are grouped into the first to third groups (first to third stages) by providing the first to third branch pipes 6a to 6c. It is not limited to this. The plurality of burners 5 may constitute one group as a whole, or may be grouped into two or four or more groups.

  A ground flare, B open pipe, 1 foundation, 2 windshield, 3 air introduction part, 4 chimney, 4a sound pressure relief hole (opening), 5 burner, 6 supply pipe, 7 first control valve, 8 second control valve, 9 Third control valve, 10 Pilot burner

Claims (5)

A windshield erected on the ground with the upper end open, an air introduction part provided inside the windshield through which combustion air can pass, a chimney erected on the air introduction part, and the chimney In a ground flare comprising a burner provided inside,
A ground flare comprising an opening for releasing sound pressure to the outside in a portion corresponding to an antinode of a standing wave of vibration generated in the chimney and the windshield in the height direction of the chimney or the windshield.   The opening regards the chimney and the windshield as a single open pipe with both ends opened and the sum of the height of the chimney and the height of the windshield, and the vibration generated in the open pipe. The ground flare according to claim 1, wherein the ground flare is provided at a portion corresponding to an antinode of standing waves.   The ground flare according to claim 2, wherein a portion corresponding to the antinode of the standing wave is set based on an effective tube length obtained by performing open end correction on the open tube.   The ground according to any one of claims 1 to 3, wherein a plurality of the openings are discretely provided in a circumferential direction of the chimney or the windshield at a portion corresponding to the antinode of the standing wave. Flare. The auxiliary opening is provided in the site | part away from the said site | part in addition to the site | part corresponded to the antinode of the standing wave in the height direction of the said chimney or the said windshield. The ground flare as described in one item.

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