Industrial Noise & Vibration Centre

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Biomass Power Station Fan Noise: silencer deleted, improved efficiency, less noise

Schiller biofuel power station fan noise attenuation

The noise from a 3m, 1.5MW wood-burning biomass boiler combustion ID fan installed at the Schiller power station in New Hampshire (one of the largest renewable energy projects in the U.S.) was dramatically reduced using innovative technology to replace the traditional silencer fitted to the power station fan. Our aerodynamic noise control technology not only cut the noise at source, but also substantially increased the fan efficiency.

Schiller ID fan remote control of noise.jpg

The ID fan feeds a stack through a system that included a very large conventional silencer to prevent noise complaints from local residents. As this muffler had a drastic impact on fan efficiency, it had to be removed. This had a serious impact on the local environment, generating a host of complaints for which a very urgent solution was required.

Our aerodynamic source control technology was retrofitted instead of the attenuator within an incredibly short 12-hour downtime window. This not only eliminated the low-frequency tonal noise problem from this large industrial boiler system at a minute fraction of the cost of the silencer it had usurped, but as it also reduced the fan power consumption, the project was self-financing.

"The ID combustion fan created a low frequency tonal noise that could be heard on the other side of the river and was the cause of complaints. The installation process took only 12 hours, after which we recorded a huge 10dB drop in noise and measured a reduction in the power used by the ID fan.."  Jim Granger, Senior Engineer, Schiller

This international project was managed remotely from our UK offices. By analysing and interpreting data acquired locally to our specifications, we were able to dispense with site visits and reduce the entire process, from initial contact to problem solved, to a matter of a few weeks.

cfd fan system flow and efficiency noise control model

Filtration (bag filters etc) and conventional attenuators reduce fan efficiency by adding back pressure. We use Computational Fluid Dynamics (CFD) modeling and past experience to determine exactly where changes can be made to reduce back pressure and hence improve system efficiency. For example, it is often possible to modify existing silencers to reduce back pressure - or even to eliminate these attenuators altogether by using alternative techniques to cut broadband noise without the hit on fan efficiency associated with conventional noise control measures..

The approach not only reduces noise, but it also cuts running costs and increases productivity. This renders noise control projects of this type highly profitable so that implementing the modifications would be a valuable exercise, even if there was no noise issue...