The benefits of infrasound as acoustic soot cleaning method

Unique knowledge

The first installation of an Infrafone Sonic Soot Cleaner with the purpose to keep an industrial boiler clean from soot was carried out in 1978. The boiler was an MgO boiler in a paper mill at Stora Enso in Hyltebruk, Sweden. The success of that installation taught us about the power of infrasound. The experience that we have obtained over the years has taught us how to create value with infrasound.

The properties of sound differ substantially depending on the frequency range. Sound can be divided into infrasound, audible sound and ultrasound. Infrafone harnesses the power of infrasound, which is sound with frequencies below 30 Hz.

Infrasound waves have many properties that make them suitable for soot cleaning applications:

  • Infrasound waves have a long wavelength. The acoustic power can reach areas far away from the acoustic source, unlike conventional soot cleaning methods.
  • Infrasound waves are omni-directional. This means that they spread in all directions with the same intensity, which implies installation flexibility. The Sonic Soot Cleaner does not necessarily need to be installed in the area to be cleaned.
  • Infrasound waves have low absorption. Consequently very little energy is lost. The energy is instead transmitted to the flue gas flow, preventing soot accumulation.

The Infrafone soot cleaning method is based on infrasound which causes oscillations within the flue gas flow. The turbulence created by the oscillations prevents accumulation of soot deposits on heat exchange surfaces.

Why infrasound is more efficient than audible sound in preventing soot build-ups

The video below shows how the grade of turbulence increases with lowered frequency. Increased turbulence reduces the areas with low gas velocity.

Tailor-made

Generating infrasound is however not enough in order to obtain the desired cleaning effect. The success of our infrasound cleaning system lies in the unique knowledge gathered during more than 30 years of experience. Our continuous development has ultimately led to unique acoustic modeling software which simulates the behavior of infrasound waves in the customer’s application. Taking into account the dimensions and operational parameters of the boiler or the exhaust gas duct, the acoustic modeling software calculates the optimal installation location and parameter settings of each Infrafone Sonic Cleaner in order to get the desired cleaning effect. Therefore every Sonic Cleaner is tailor-made for each specific application and every customer’s individual needs.

The optimal installation location is not always straightforward to determine. For successful results it is therefore crucial to have the knowledge and capability to calculate where each Sonic Cleaner needs to be located, what size of Sonic Soot Cleaner is necessary and which operating frequency it should have. The figures on the right show two Infrafone Sonic Soot Cleaning installations on an industrial and a marine boiler. Although the installation locations seem odd they are optimal from an acoustic point of view for the desired cleaning area. Each sonic cleaner operates on a different frequency that is optimal for each cleaning area.