Kockum Sonics' SONOFORCE for audible sound.

Over the years the number and variety of acoustic or sonic cleaning installations have increased dramatically. The reported benefits include higher boiler availability, reduced maintenance required, reduced tube erosion, etc.
For marine applications, the technique specifically prevents stack fires in exhaust gas boilers and the occurrence of soot flakes in the exhaust funnel. The increasing marine use of catalytic reduction of NOx-content in the exhaust puts focus on an interesting application now in use on board LPG/C “Navion Dania”.

History records differ much in describing the actual invention of sonic cleaning, but a fact of the matter is that long time ago a gunshot through the stack was recognized as a method to clean the inner surfaces of the boiler.
It was well known already then that the sound waves were responsible for the cleaning effect.
   Another fact of the matter is that Kockum Sonics started to develop this method in the late 60’s based on the company’s deep knowledge in the field of acoustics and in developing equipment for extreme high sound pressure-levels (TYFON). Since then, the method has been developed in all aspects. Today, Kockum Sonics can offer “multi-spectral” cleaning (both audible and infrasound) together with an unsurpassed sound pressure-level of well over 150 dB.
Together with a deep understanding of the customer’s process, it has resulted in a huge number of installations and a variety of applications that stands second to none.
   The basic principle behind sonic cleaning is rather simple: The sound waves make the particles oscillate and thus make them more accessible to gravity and flue gas. Furthermore, the sound waves reduce the boundary layer, which in turn leads to an increase in flue gas velocity closer to the surface. As a result of combining these factors, ash and particle deposits are loosened and dislodged from surfaces along the flue gas pathway.

No wear or damage
It is important to point out that sonic cleaning causes no wear or damage to the surfaces and structure. As mentioned above, it is the particle that oscillate, not the structure itself. Being a completely dry method, there is of course no erosion of the surfaces. In addition, and caused by the high reflectivity factor, sound waves fill a volume more efficiently than other methods and thus leave no “blind spots”.
   The method is continuous and must be used constantly in intervals. It will then keep surfaces clean. In many cases the original method of cleaning has been dismounted and sonic cleaning has become the sole method. In other cases the methods run parallel, but the other method is used as supplement and intervals are kept longer.

Important enviromental factors
Please note that sonic cleaning is not a method for cleaning surfaces where deposits have been allowed to grow freely for a longer time with hardened or sintered outer surfaces as result. But preventing this build-up from happen is exactly what sonic cleaning do best!
   Clean surfaces gives more efficient heat transfer, which in turn results in more economical utility of the boiler. In addition, sonic cleaning equipment is favourable from an investors perspective due to a large number of other advantages, such as:
Low investment costs
Low Maintenance costs
No corrosion
Longer between shutdowns.

Selective Catalytic Reactors
More efficient heat transfer also results in a more favourable process from an environmental point of view. Other important environmental factors are the prevention of stack fires in exhaust gas boilers and the reduction of soot accumulation, which excludes the occurrence of soot flakes on deck.
The soot flakes are especially not wanted on cruise vessels and/or in the Alaskan archipelago.
   An application with strong environmental connection is the use of sonic cleaning for SCR (Selective Catalytic Reactors, used to reduce NOx-content in the exhaust). It has proven to be a very efficient combination, even though the catalyst cell is designed more or less as a sound damper. Actually this has proven to be a fact for many of the sound frequencies.
   Kockum Sonics has carried out an extensive research to find the optimum frequency and sound pressure level for SCR’s. Catalysts are now becoming favourable for ship owners, since harbour charges more commonly are reduced when SCR are in operation.
   Based on an order from Haldor Topsoe A/S, Kockum Sonics has installed sonic cleaning for the SCR onboard LPG/C Navion Dania.
The SCR is installed directly between the exhaust gas receiver and the turbocharger. With the sonic cleaning in use, the pressure-drop over the reactor can be kept within limits and thus reduce the need for other cleaning-methods dramatically. The result is a much higher availability of the system, which in turn leads to better production economy together with the saving in harbour charges.

//Vice President Christian Wildstam, Kockum Sonics AB, Malmö, Sweden
christian.wildstam@kockumsonics.com

Back to SSG 18, 3 October

Latest update 3-10-2006 16:37

All material © Scandinavian Shipping Gazette.

Scandinavian Shipping Gazette | www.shipgaz.com | info@shipgaz.com | webmaster | Contact us | Cookie information