An industrial chimney (aka stack) can constitute a source of very powerful noise potentially causing noise pollution for the environment, near or far, a fortiori if it is very high.
In the case of hot gases, the exhaust of gas turbines or combustion engines is often the source of a noise which, if not sufficiently attenuated by the components of the network, is present at the outlet of the chimney (stack) in an undesirable manner.
Hot or cold, gas flows are also often vented to the atmosphere by means of a chimney (stack) located downstream of a ventilator, and can also give cause inconvenience for local residents.
In some cases, insufficient chimney (stack) diameter may cause gas velocities sufficiently high to generate aerodynamic noise at a location in the aeraulic network downstream of which nothing is provided to attenuate it.
In the field of industrial soundproofing, the noise reduction of an industrial chimney (stack) occupies a special place, given the multidisciplinary know-how required to succesfully carry out this kind of project.
ITS participated in the reduction of the noise emmitted by an industrial chimney (stack) near Grenoble, France, in the Rhône-Alpes region.
This chimney (stack), about thirty meters high, had been equipped, by others, with a dissipative silencer, at the discharge of a fan (air and effluents at a temperature above 150 ° C, flow rate exceeding 160000 m3 / h), which proved to be insufficient since nuisance was observed in the environment, in the far field, particularly in relation to the significant height of the structure (and in relation to the noise emitted in the upper part of the chimney).
In the context of this project of noise reduction of an industrial chimney (stack), it was decided to retain the existing silencer, and as a result, the total pressure loss available for other soundproofing equipment (although necessary) was very limited, even though the velocity of the gases in the upper section of the chimney (stack) was opposed to the generation of a sound power level at the outlet of the chimney (self noise) sufficiently low to not cause environmental pollution.
A quite complex design study was carried out (by ITS) to satisfy the ambitious acoustic & aerodynamic objectives of this project.
The upper section of the chimney (stack) has been replaced by a new section (with a diameter of about 2.2 m i.e. greater than the existing one), with a height close to 10 m, with an absorbent lining capable of providing the acoustic attenuation required, and with dimensions such that the self-noise of the soundproofing device can be sufficiently low.
Made of stainless steel to guarantee a good resistance with time, with an upstream flange interfacing perfectly with the existing one, with orifices allowing measurements of gaseous discharges by the operator, with - in the upper part - rings to allow guying (for wind stability) & lifting lugs, this silencer was installed on site (with a crane) in record time.
Mission accomplished for ITS: in terms of sound environment, there is no obstacle any more to the quietness of nearby residents, near or far from this industrial site.