A low-resistance high-efficiency return air shaft silencer for large air volume

Abstract

This invention discloses a low-resistance, high-efficiency return air shaft silencing device for large air volumes, consisting of a matrix silencing system and a frame support system. The matrix silencing system includes an outer ring sound-absorbing barrier (2) and rectangular silencing columns (1), with adjacent rows of rectangular silencing columns (1) staggered. The outer ring sound-absorbing barrier (2) is a frustum-shaped diffuser with a larger top and smaller bottom, and the rectangular silencing columns (1) are horizontally arranged within it. The frame support system includes steel column supports (3) and column concrete foundations (7). The lower part of the steel column supports (3) is mounted on the column concrete foundations (7), and the upper part is connected to the outer wall (9) of the outer ring sound-absorbing barrier through stiffening plates (6). A tie brace (4) is provided between the steel column supports (3) and the shaft sidewall (8). This invention has the advantages of simple structure, significant silencing and noise reduction performance, low resistance and low disturbance, wide applicable sound source frequency band, and low friction loss characteristics, achieving an overall noise reduction of 21~28 dB(A) at the shaft outlet, with a significant noise reduction effect.

Description

Technical Field

[0001] This invention belongs to the field of noise reduction technology for mine return air shafts, specifically relating to a noise reduction device for mine return air shafts, which is particularly suitable for noise reduction treatment of mine return air shafts with large air volume, high-speed airflow, high noise (100-120 dB(A)), wide frequency band, and prominent low frequency. Background Technology

[0002] Mine ventilation systems are core infrastructure for ensuring safe production in mines. Return air shafts, as crucial channels for discharging polluted air from underground to the surface, typically feature ventilation fans with large air volume, high air pressure, and adaptability to various operating conditions. The continuous, high noise generated by these fans not only causes excessive noise emissions at the mine boundary but may also lead to complaints and disputes from nearby residents due to their wide radiation range and long-distance impact, becoming a prominent challenge in mine environmental management.

[0003] The noise generated during the operation of a ventilation fan mainly consists of the following three parts:

[0004] Aerodynamic noise, generated by airflow turbulence, vortex pulsation, and blade rotation at the air inlet and outlet, is the core source of fan noise. Noise levels typically reach 100–120 dB(A), exceeding mechanical and electromagnetic noise by 10–20 dB(A). This type of noise is characterized by a wide bandwidth, a high proportion of mid-to-low frequency energy, and slow propagation attenuation. It is also accompanied by a distinct rotating discrete tone, making it extremely difficult to control.

[0005] Mechanical noise. Generated by the vibration and friction of the fan casing, bearings, and transmission components. The noise intensity is relatively low, but it can still cause interference to operators at close range.

[0006] Electromagnetic noise. It is generated by the vibration of the stator and rotor caused by the magnetic field pulsation when the motor is running. It usually manifests as a low-frequency hum and accounts for a small proportion of the total noise of the fan.

[0007] Currently, noise control in mine return air shafts mainly employs the following four technical measures:

[0008] One method is resistive noise reduction technology. This relies on the viscous resistance and heat exchange of porous sound-absorbing materials to convert sound energy into heat energy, offering some attenuation for mid-to-high frequency broadband noise. However, its noise reduction efficiency is very limited for low-frequency aerodynamic noise, which is predominant in return air shafts. Furthermore, the harsh environment of underground mines, characterized by dampness and corrosive gases, causes sound-absorbing materials to quickly absorb moisture and corrode, resulting in a service life typically less than one year.

[0009] Second is resistance-based noise reduction technology. By inducing sound wave reflection and interference through abrupt changes in pipe cross-section and resonant cavities, it can effectively control low-frequency noise at specific frequencies. However, it has poor adaptability to broadband noise, and the excitation of higher-order sound modes can severely weaken its noise reduction performance. Furthermore, the complex structure can easily increase airflow resistance.

[0010] Thirdly, sound insulation enclosure technology. By setting up sound barriers or soundproof rooms around the fan and duct to block the noise propagation path, the control efficiency of mechanical noise and electromagnetic noise can reach more than 60%. However, for aerodynamic noise radiated outward through the airflow channel, it can only play a role by blocking the indirect propagation path and cannot directly attenuate the noise energy in the airflow, so the treatment effect is limited.

[0011] Fourth, optimize the fan structure. Noise can be reduced at the source by adjusting the blade angle, optimizing the impeller surface, and using high-damping materials. However, it is difficult to fundamentally eliminate the aerodynamic noise generated in the airflow channel. Moreover, the modification cost is high, the cycle is long, and it is difficult to adapt to the existing mine ventilation system.

[0012] Therefore, developing a noise reduction device that combines high noise reduction efficiency, low airflow resistance, and strong environmental adaptability has become a critical technical bottleneck in this field, given the high flow rate, high speed of airflow, wide frequency band, and prominent low frequency noise characteristics of mine return air shafts. Summary of the Invention

[0013] The purpose of this invention is to address the noise characteristics of large flow rates, high-speed airflow, and wide-bandwidth, low-frequency noise in underground mine return air shafts, as well as the technical challenges of existing silencing technologies, such as low low-frequency noise reduction efficiency, high airflow resistance, short service life in humid and corrosive environments, and poor wide-bandwidth noise adaptability. The invention provides a low-resistance, high-efficiency silencing device for large airflow return air shafts that is simple in structure, has significant noise reduction performance, and features low flow resistance and low friction loss.

[0014] To achieve the above-mentioned objectives of the present invention, the present invention provides a low-resistance, high-efficiency return air shaft silencing device for large air volumes, which is implemented using the following technical solution.

[0015] This invention discloses a low-resistance, high-efficiency silencing device for large-volume return air shafts, comprising a matrix silencing system and a frame support system. The matrix silencing system covers the return air shaft inlet and consists of an outer ring sound-absorbing barrier and 4-8 rows of rectangular silencing columns connected together. Adjacent rows of rectangular silencing columns are staggered, avoiding direct sound transmission and transforming noise propagation from straight-line to diffraction. Simultaneously, the array structure forms multiple parallel small channels, resulting in strong rectification and avoiding turbulence and flow deviation that might occur with large, sheet-like channels, thus reducing eddy current noise and regenerated noise. The outer ring sound-absorbing barrier is a frustum-shaped diffuser structure, larger at the top and smaller at the bottom, with 4-8 rows of rectangular silencing columns horizontally arranged within it. The frame support system... The support system includes steel column supports and concrete foundations for the columns. The lower part of the steel column supports is installed on the concrete foundations, and the upper part of the steel column supports is connected to the outer wall support of the outer ring sound-absorbing barrier via stiffening plates. Tie bracing is provided between the steel column supports and the side wall of the well shaft. The outer ring sound-absorbing barrier is made of the following materials from the inside out: a 0.8~1.5mm thick perforated plate, a layer of 0.6~1.0mm diameter galvanized wire mesh, a 0.1~0.2mm thick alkali-free hydrophobic glass cloth, an 80~90mm ultrafine glass wool, a 2~4mm thick asphalt-based high-damping cloth, and a 1~2mm thick galvanized outer protective plate. The longitudinal arrangement height H of the matrix sound-absorbing columns and the sound attenuation ΔdB are calculated using the following empirical formula:

[0016] ΔdB≈(0.3~0.6)*P / S*H;

[0017] Where ΔdB is the noise reduction amount, dB(A); P / S is the shape factor, which is the ratio of the perimeter of the airflow channel interface to the cross-sectional area; H is the longitudinal arrangement height of the muffler.

[0018] Preferably, the rectangular silencer column is made of the following materials from the inside out: 1.0~1.6mm thick 80mm×80mm~150mm×150mm galvanized keel, 20~30mm thick ultrafine glass wool, a layer of alkali-free water-repellent glass fiber cloth, a layer of 0.6mm~1.0mm diameter galvanized wire mesh, and an outer layer of 0.8~1.5mm thick perforated plate. The rectangular silencer columns are arranged in a staggered pattern along the airflow direction to form a silencer matrix, overcoming the high-frequency efficiency reduction problem of traditional plate silencers. Simultaneously, diffraction propagation reduces direct sound, significantly improving low-frequency noise reduction.

[0019] Preferably, the longitudinal spacing S1 of the rectangular sound-absorbing columns is 1.5~2.0d. e d eThe cross-sectional area of ​​the rectangular silencing column is the equivalent diameter; the lateral spacing S2 of the rectangular silencing columns is 100mm~250mm. The smaller the lateral spacing, the higher the high-frequency failure frequency (upper limit frequency); the array-type rectangular silencing columns are arranged more closely, and the perimeter of the exposed sound-absorbing surface is much larger than that of the plate-type, increasing the sound-absorbing area by 30%~50%. Here, the lateral spacing S1 refers to the vertical spacing between adjacent upper and lower rows, and the lateral spacing S2 refers to the horizontal spacing between adjacent rectangular silencing columns in the same row.

[0020] Preferably, the concrete foundation of the column is provided with embedded iron plates for welding and fixing the steel column support.

[0021] Preferably, a stiffening plate is provided at the connection between the embedded iron sheet and the lower part of the steel column support, and stiffening plates are also provided at the connection between the tie cross brace and the steel column support, and at the connection between the tie cross brace and the well wall.

[0022] Preferably, the average airflow velocity at the outlet section of the outer ring sound-absorbing barrier is controlled within the range of 5~10m / s, and the outer ring sound-absorbing barrier is a frustum-shaped diffuser with a larger top and a smaller bottom. The overall airflow resistance of the noise reduction system is between 120~180Pa, and the reduction rate of the total return air volume in the well is ≤5%.

[0023] Preferably, the perforated plate inside the outer ring sound barrier has a hole diameter of 4-6 mm and a perforation rate of 30%-36%, arranged in equilateral triangles or rectangles; the galvanized wire mesh inside the outer ring sound barrier has a mesh size of 10-20 mm; and the ultrafine glass wool inside the outer ring sound barrier has a density of 40-60 kg / m³. 3 .

[0024] Preferably, the density of the ultrafine glass wool inside the rectangular sound-absorbing column is selected to be 60~80 kg / m³. 3 The perforated plate has a hole diameter of 3~5mm and a perforation rate of 25%~35%.

[0025] This invention discloses a low-resistance, high-efficiency return air shaft silencing device for large air volumes. By employing the above technical solution, it broadens the silencing frequency band through outer ring resistive silencing and inner ring resistive silencing, significantly reducing noise levels by 21-28 dB(A). Specifically, it has the following beneficial effects:

[0026] (1) This invention integrates resistive and reactive noise reduction principles to achieve precise control of broadband noise of 100~120dB(A) in mine return air shafts, especially low-frequency aerodynamic noise: through the diffraction propagation design of staggered rectangular noise reduction columns, the pain point of low-frequency noise reduction efficiency of traditional plate silencers is solved; combined with the array structure with high sound absorption area, the attenuation effect of mid-to-high frequency noise is simultaneously improved, and finally the overall noise at the shaft outlet is reduced by 21~28dB(A), which fully covers the control needs of aerodynamic, mechanical and electromagnetic noise.

[0027] (2) This invention adopts a combination structure of frustum-shaped diffuser and staggered matrix silencing columns. It reduces the outlet airflow velocity through the diffuser (controlled at 5~10m / s) and avoids turbulence and deflection by utilizing the rectification effect of the matrix channels. The overall airflow resistance of the silencing system is controlled within the range of 120~180Pa, and the total return air volume in the mine is reduced by ≤5%. While achieving efficient noise reduction, it does not affect the air pressure and air volume supply of the mine ventilation system, ensuring the core needs of safe production in the mine.

[0028] (3) The entire structure of this invention uses galvanized keel, perforated plate, water-repellent glass wool and other moisture-resistant and corrosion-resistant materials, which are suitable for the harsh environment of high humidity and corrosive gas in underground mines. The service life of the core sound-absorbing components can reach more than 5 years, which is more than 3 times that of traditional resistive sound-absorbing materials.

[0029] (4) The present invention adopts a modular matrix silencing column design, which can be disassembled and cleaned and damaged parts can be replaced separately. Maintenance operations do not require overall shutdown, which greatly reduces operation and maintenance costs and time. The frame support system can resist the long-term impact of high-speed airflow in the return air shaft through the reinforced structure of pre-embedded iron plates and stiffening plates, and has strong operational stability. Attached Figure Description

[0030] Figure 1 This is an external structural diagram of a low-resistance, high-efficiency return air shaft silencing device for large air volume according to the present invention;

[0031] Figure 2 This is a structural diagram of the outer ring sound-absorbing barrier designed for this invention;

[0032] Figure 3 A structural diagram of the rectangular sound-absorbing column designed for this invention;

[0033] Figure 4 This is a comparison diagram showing the effects of implementing this invention before and after implementation at an iron mine in Lujiang.

[0034] The attached diagram is labeled as follows: 1-Rectangular sound-absorbing column; 2-Outer ring sound-absorbing barrier; 3-Steel column support; 4-Tie cross brace; 5-Embedded iron plate; 6-Stiffening plate; 7-Column concrete foundation; 8-Well shaft sidewall; 9-Outer ring sound-absorbing barrier outer wall. Detailed Implementation

[0035] The following will describe in more detail, with reference to the accompanying drawings of the embodiments of the present invention, a low-resistance, high-efficiency return air shaft silencing device for large air volumes. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] Depend on Figure 1 The diagram shown is an external structural diagram of a low-resistance, high-efficiency return air shaft silencing device for large air volumes, and is combined with the present invention. Figure 2 , Figure 3 As can be seen, the low-resistance, high-efficiency return air shaft silencing device of the present invention for large air volume is composed of a matrix silencing system and a frame support system connected and combined. The matrix silencing system reduces the noise value of the outlet airflow by performing impedance composite silencing treatment on the large flow and high speed return airflow, while the frame support system is used for support and fixation. The matrix silencing system covers the return air shaft inlet and consists of an outer ring sound-absorbing barrier 2 and 4-8 rows of rectangular silencing columns 1 connected together, with adjacent rows of rectangular silencing columns 1 staggered. The outer ring sound-absorbing barrier 2 is a frustum-shaped diffuser structure with a larger top and smaller bottom, and the 4-8 rows of rectangular silencing columns 1 are horizontally arranged within the outer ring sound-absorbing barrier 2. The frame support system includes steel column supports 3 and column concrete foundations 7. Embedded iron plates 5 for welding and fixing the steel column supports 3 are provided in the column concrete foundations 7. The lower part of the steel column supports 3 is welded to the embedded iron plates 5, and the upper part of the steel column supports 3 is supported and connected to the outer wall 9 of the outer ring sound-absorbing barrier via stiffening plates 6. A tie-bracing cross brace 4 is arranged between the shaft sidewall 8 and the shaft shaft sidewall 8; a stiffening plate 6 is provided at the lower connection between the pre-embedded iron plate 5 and the steel column support 3. Stiffening plates 6 are also provided at the connection between the tie-bracing cross brace 4 and the steel column support 3, and at the connection between the tie-bracing cross brace 4 and the shaft sidewall 8. The stiffening plate 6 is used to increase the contact area, disperse the concentrated force, transfer shear force and improve shear bearing capacity, and improve the fatigue performance of the weld. The steel column support 3 is mainly used to bear the vertical load of the matrix silencing system, and the tie-bracing cross brace 4 is mainly used to enhance the structural stability and wind resistance. The column concrete foundation 7 is used to transfer the vertical load of the system to the ground surface. The shaft sidewall 8 bears part of the vertical load on the one hand, and at the same time prevents surface water and debris from flowing into the return air shaft. The outer ring sound barrier 2 is made of the following materials from the inside out: a 0.8-1.5mm thick perforated plate, a layer of 0.6-1.0mm diameter galvanized wire mesh, a 0.1-0.2mm thick alkali-free hydrophobic glass cloth, an 80-90mm ultrafine glass wool, a 2-4mm thick asphalt-based high-damping cloth, and a 1-2mm thick galvanized outer protective plate; the rectangular sound-absorbing column 1 is made of the following materials from the inside out: a 1.0-1.6mm thick 80mm×80mm-150mm×150mm galvanized keel, a 20-30mm thick ultrafine glass wool, a layer of alkali-free hydrophobic glass fiber cloth, a layer of 0.6mm-1.0mm diameter galvanized wire mesh, and an outer layer of 0.8-1.5mm thick perforated plate; the longitudinal arrangement height H and the sound attenuation ΔdB of the matrix sound-absorbing column 1 are calculated according to the following empirical formula:

[0037] ΔdB≈(0.3~0.6)*P / S*H;

[0038] Where ΔdB is the noise reduction amount, dB(A); P / S is the shape factor, which is the ratio of the perimeter of the airflow channel interface to the cross-sectional area; H is the longitudinal arrangement height of the muffler.

[0039] In this embodiment, the relevant technical parameters of the low-resistance, high-efficiency return air shaft silencing device for large air volumes of the present invention are as follows: the longitudinal spacing S1 of the rectangular silencing columns 1 is 1.5~2.0d. e d e The equivalent diameter of the rectangular sound-absorbing column 1 is defined as follows: the transverse spacing S2 of the rectangular sound-absorbing column 1 is 100mm~250mm; the average airflow velocity at the outlet section of the outer ring sound-absorbing barrier 2 is controlled within the range of 5~10m / s; the perforated plate in the outer ring sound-absorbing barrier 2 has a hole diameter of 4~6mm, a perforation rate of 30%~36%, and is arranged in equilateral triangles or rectangles; the galvanized wire mesh in the outer ring sound-absorbing barrier 2 has a mesh size of 10~20mm; and the ultrafine glass wool in the outer ring sound-absorbing barrier 2 has a density of 40~60kg / m³. 3 The density of the ultrafine glass wool inside the rectangular sound-absorbing column 1 is selected to be 60~80 kg / m³. 3 The perforated plate has a hole diameter of 3~5mm and a perforation rate of 25%~35%.

[0040] In practical applications, the aerodynamic noise of the return airflow discharged from the return air shaft of an underground mine is continuously absorbed and reflected by the matrix silencing system after flowing out of the shaft. The combined effect of the outer ring sound-absorbing barrier 2 (resistive silencing) and the matrix-arranged rectangular silencing columns 1 (resistive silencing) significantly reduces noise emissions. The frustum-shaped diffuser structure (larger at the top and smaller at the bottom) slows down the airflow velocity, thereby reducing aerodynamic noise and airflow resistance. In the matrix silencing column 1 structure, the keel ensures the structural strength and morphological stability of the silencing body. The porous ultra-fine glass wool material converts sound energy into heat energy through viscous friction, while the alkali-free hydrophobic glass fiber cloth protects the core sound-absorbing material (glass wool) from being blown away by the airflow. Simultaneously, it has high sound wave penetration and absorption rates. In the outer ring sound barrier 2 structure, galvanized steel wire mesh is used to fix the glass wool and prevent it from deforming and being damaged under strong airflow. Alkali-free water-repellent glass fiber cloth protects the sound-absorbing material without affecting the noise penetration and absorption rate. Ultrafine glass wool is mainly used to reduce mid-to-high frequency noise. Asphalt-based high-damping cloth can effectively suppress the resonance and "coincidence effect" that may be generated by the "panel-cavity-panel" structure and improve the mid-to-low frequency noise reduction value. The galvanized outer protective plate is used to prevent external damage and can also isolate some mid-to-high frequency noise.

[0041] In the frame support system, the steel column support 3 is mainly used to bear the vertical load of the matrix silencing system, while the tie cross brace 4 is mainly used to enhance structural stability and wind resistance. The embedded iron plate 4 is used to weld and fix the cross brace column, and the stiffening plate 6 is used to increase the contact area, disperse the concentrated force, transfer shear force and improve shear bearing capacity, and improve the fatigue performance of the weld.

[0042] This invention relates to a low-resistance, high-efficiency silencing device for large-volume return air shafts. It has been applied in the renovation of return air shafts at two iron mines, one in Baowu Resources and the other in Lujiang. The device significantly reduces airflow noise at the shaft outlet, featuring a simple structure, stable operation, remarkable effectiveness, and good technical and economic efficiency. Actual application results at the Baowu Resources and Lujiang iron mines demonstrate that the silencing device is reliable, effective, and operates stably. On-site testing by local environmental protection authorities shows that noise emissions at the plant boundary meet standards by 100%, and no further noise complaints have been received from nearby residents.

[0043] Depend on Figure 4 The comparison diagram of the implementation of the present invention before and after implementation in an iron mine in Lujiang shows that, before and after implementation, noise levels were measured at the return air shaft outlet, shaft side, upper surface of the return air duct, factory boundary wall, and near the residential area. The noise levels decreased from 115dB(A), 102dB(A), 92dB(A), 68dB(A), and 61dB(A) to 92dB(A), 84dB(A), 75dB(A), 52dB(A), and 48dB(A), respectively, achieving unexpected technical results.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-resistance, high-efficiency return air shaft silencing device for large air volumes, characterized in that: It includes a matrix silencing system and a frame support system; the matrix silencing system covers the return air shaft inlet and is composed of an outer ring sound-absorbing barrier (2) and 4 to 8 rows of rectangular silencing columns (1) connected together, with adjacent rows of rectangular silencing columns (1) staggered; the outer ring sound-absorbing barrier (2) is a frustum-shaped diffuser structure with a larger top and a smaller bottom, and 4 to 8 rows of rectangular silencing columns (1) are horizontally arranged in the outer ring sound-absorbing barrier (2); the frame support system includes steel column supports (3) and column concrete foundations (7), the lower part of the steel column supports (3) is installed on the column concrete foundations (7), and the steel column supports (3) The upper part of the outer ring sound-absorbing barrier (2) is supported and connected to the outer wall (9) of the outer ring sound-absorbing barrier by a stiffening plate (6). A tie cross brace (4) is arranged between the steel column support (3) and the well side wall (8). The outer ring sound-absorbing barrier (2) is made of 0.8~1.5mm thick perforated plate, a layer of 0.6~1.0mm diameter galvanized wire mesh, 0.1~0.2mm thick alkali-free water-repellent glass cloth, 80~90mm ultra-fine glass wool, 2~4mm thick asphalt-based high damping cloth, and 1~2mm thick galvanized outer protective plate. The longitudinal arrangement height H and the sound attenuation ΔdB of the matrix sound-absorbing column (1) are calculated according to the following empirical formula: ΔdB≈(0.3~0.6)*P / S*H; Where ΔdB is the noise reduction amount, dB(A); P / S is the shape factor, which is the ratio of the perimeter of the airflow channel interface to the cross-sectional area; H is the longitudinal arrangement height of the muffler.

2. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 1, characterized in that: The rectangular sound-absorbing column (1) is made of the following materials from the inside out: 1.0~1.6mm thick 80mm×80mm~150mm×150mm galvanized keel, 20~30mm thick ultrafine glass wool, a layer of alkali-free water-repellent glass fiber cloth, a layer of 0.6mm~1.0mm diameter galvanized wire mesh, and an outer layer of 0.8~1.5mm thick perforated plate.

3. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 1, characterized in that: The longitudinal spacing S1 of the rectangular sound-absorbing columns (1) is 1.5~2.0d. e d e The cross-sectional area of ​​the rectangular silencing column (1) is equivalent to the diameter; the lateral spacing S2 of the rectangular silencing column (1) is 100mm~250mm.

4. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 1, characterized in that: An embedded iron plate (5) for welding and fixing the steel column support (3) is provided in the concrete foundation (7) of the column.

5. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 4, characterized in that: A stiffening plate (6) is provided at the lower connection between the pre-embedded iron sheet (5) and the steel column support (3). A stiffening plate (6) is also provided at the connection between the tie cross brace (4) and the steel column support (3) and at the connection between the tie cross brace (4) and the well wall (8).

6. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 1, characterized in that: The average airflow velocity at the outlet section of the outer ring sound-absorbing barrier (2) is controlled within the range of 5~10m / s.

7. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 1, characterized in that: The perforated plate inside the outer ring sound barrier (2) has a hole diameter of 4~6mm and a perforation rate of 30%~36%, arranged in equilateral triangles or rectangles; the galvanized wire mesh inside the outer ring sound barrier (2) has a mesh size of 10~20mm; and the ultrafine glass wool inside the outer ring sound barrier (2) has a density of 40~60kg / m³. 3 .

8. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 2, characterized in that: The density of the ultrafine glass wool inside the rectangular sound-absorbing column (1) is selected to be 60~80 kg / m³. 3 The perforated plate has a hole diameter of 3~5mm and a perforation rate of 25%~35%.

9. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 2, characterized in that: The longitudinal spacing S1 of the rectangular sound-absorbing columns (1) is 1.5~2.0d. e d e The cross-sectional area of ​​the rectangular sound-absorbing column (1) is equivalent to the diameter; the horizontal spacing S2 of the rectangular sound-absorbing column (1) is 100mm~250mm; the concrete foundation (7) of the column is provided with embedded iron plates (5) for welding and fixing the steel column support (3); a stiffening plate (6) is provided at the connection between the embedded iron plate (5) and the lower part of the steel column support (3), and a stiffening plate (6) is provided at the connection between the tie cross brace (4) and the steel column support (3) and at the connection between the tie cross brace (4) and the well wall (8).

10. The low-resistance, high-efficiency return air shaft silencing device for large air volume as described in claim 9, characterized in that: The average airflow velocity at the outlet section of the outer ring sound barrier (2) is controlled within the range of 5~10m / s; the perforated plate inside the outer ring sound barrier (2) has a hole diameter of 4~6mm, a perforation rate of 30%~36%, and is arranged in equilateral triangles or rectangles; the galvanized wire mesh inside the outer ring sound barrier (2) has a mesh size of 10~20mm, and the ultrafine glass wool inside the outer ring sound barrier (2) has a density of 40~60kg / m³. 3 The density of the ultrafine glass wool inside the rectangular sound-absorbing column (1) is selected to be 60~80 kg / m³. 3 The perforated plate has a hole diameter of 3~5mm and a perforation rate of 25%~35%.

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