The limitation of noise emissions is a problem that is, fortunately, increasingly taken into account during the construction of industrial sites.
In an air separation plant, the basic components of the atmosphere are separated (by means of various complex manufacturing processes involving in particular cryogenic distillations and heat exchangers) to obtain pure gases: mainly oxygen and nitrogen, secondarily rare inert gases such as argon.
These distillation products are widely used in various industrial sectors e.g. chemistry, metallurgy, pharmacy, food industry and also have medical applications.
Obtaining them involves specific equipment combining different pressure equipment: control valves are associated with them, especially when it is necessary to carry out depressurizations, which are accompanied by noise emissions that must be controlled from a perspective of limiting the noise exposure of site workers and maintaining a sufficiently quiet environment for the neighborhood.
ITS was involved in the construction of discharge silencers for an air separation plant in Eastern Europe, in teh context of an industrial soundproofing project.
For one of the silencers the fluid to be considered was a mixture of oxygen, nitrogen and argon, for the second silencer it was pure oxygen while for the third silencer the gas was pure nitrogen.
Upstream of each of the soundproofing devices were provided several (2 to 3) control valves, of which the prediction of aerodynamic noise for ITS was a key stage of the project, since the propagation of noise downstream of the valves was a source of nuisance to be quantified with sufficient accuracy before anything else.
Such a calculation has resorted to sophisticated modeling, taking into account not only the intrinsic characteristics of each valve, but also the different operating regimes related to the thermodynamic conditions of the transported fluid, resulting in particular from the pressure differential to be considered for several conditions of services, and to which were associated flow values sometimes varying in large proportions, all of what being essentially likely to impact the noise emitted.
The values of the acoustic power spectrum (calculated by 1/3 octave frequency band from 20 to 20000 Hz) influenced the design of the expansion device (single or multi-stage diffuser), as well as the silencers dissipative section for which taking into account the risks of combustion in the case of operation with pure oxygen was necessary for the selection of a suitable lining, whhat imposed specific constructive provisions, in addition to (for the partner of ITS having built the silencers) those related to the consideration of equipment subject to significant pressure.
The computing resources available at ITS for acoustics and fluid dynamics, developed to enable performance analysis and evaluation for such applications, have once again been widely used in this project related to discharge silencers for an air separation unit that are high performing industrial silencers, which are quite widely used in the context of monitoring noise emissions from installations.