INFRASON : industrial boilers soot cleaning by infrasound, low frequency sound

Velocity and amplitude

Acoustic pressure is :

P = Pmsin wt

And involves an oscillation of the gas, if the wave is plane :

P = cu and
u = P/ rc = (Pm / rc ) sinwt

Amplitude x is maximal with :

x =u/w = Pm/ rcw = Pm / 2 pr cf

Which gives with the previous case :

acoustic pressure	sound level	velocity	amplitude of the particules at 20 Hz	amplitude at 2000HZ
2	100	0.007	0.055	0.00055
20	120	0.07	0.55	0.005
35.6	125	0.122	1	0.0097
63.2	130	0.22	1.7	0.0173
112	135	0.38	3.1	0.0306
200	140	0.68	5.5	0.055
356	145	1.22	9.7	0.097

When looking at this table it is obvious that it is very important to produce low frequency sound. Also to be noted , is that low frequency sound is not so disturbing to humans.

Infrasound:

Infrasounds are very low frequency sounds, their frequency is less than 30Hz.

Their wave lengths are about 30 m (in the boilers )

Sound levels in the boilers are about 140 db.

Infrasounds can produce high particle velocity rates , to avoid the sticking of these particles on the boiler tubes.

Damping effects on infrasounds are much smaller than damping of other ranges of sounds, so a single soot cleaner can keep a whole boiler clean.

Humans do not really "hear" infrasounds, so infrasounds between 15 and 30 Hz are not dangerous, as are normal range sounds at high decibel levels.

Soot cleaning efficiency in boilers:

Efficiency of the cleaning is related to :

the amplitude of the pulsation of the gas dans les zones concernées
how the particles are sticking on the tubes depending on :
temperature of the area
chemical composition of the smoke

Boiler managers know that many boilers can get dirty very, very quickly… In these cases, infrasounds can help very well in keeping these units in operation for longer runs, and in this way saving a lot of money…

Infrason - La Lucaciaire ROUFFIGNY - 50800 VILLEDIEU LES POELES

tél : 02 33 91 13 91 - fax : 02 33 91 13 92