A sound solution to ash build up in biomass power plants

By Donald F Cameron

Established in 1998, Primasonics® International Ltd is the worldwide leader in design, manufacture and supply of Acoustic Cleaning Systems and Technologies. Based in Penrith, Cumbria, and augmented by a network of agents spanning the globe, our products are used in a variety of industries such as Power Generation, Cement, Petro Chemical, Food, Gypsum, Carbon Black, Chemical, and many more.

We design, manufacture and sell Acoustic Cleaners and Sonic Soot Blowers for the prevention of particulate build up and blockage in a wide range of industrial applications. As one of the few companies in the world that actually specialise in Acoustic Cleaning technology we offer the widest range of frequency models which can be tailor made to fit most installations and environments.

Acoustic Cleaning encompasses the realm of sound transmission through solids. It is best described by the creation of rapid pressure fluctuations. These pressure fluctuations are transmitted into the particulate matter or “bonded” dry material causing the solid particles to resonate and dislodge from the surface they are deposited on or bonded to. Once dislodged, the materials fall, either due to gravity or are carried away by the gas or air stream within the process.

The powerful sound waves are produced when the short bursts of standard plant compressed air enters the wave generator and force the only moving part, an aerospace grade titanium diaphragm, to flex creating the powerful “base” sound wave. This “base” tone is then transmitted by a range of different bell sections, depending on the application, into selected fundamental frequencies between 60 – 420Hz in our Audiosonic™ Acoustic Cleaner Range and 60 – 350Hz in our Quattrosonic Sonic Soot Blower Range.

This non-intrusive, affordable technology can be used to aid, and often replace, more damaging cleaning methods such as Steam Soot Blowers, Air Cannons, Mechanical Rapping Systems and Vibrators. They can increase the efficiency of process plant, provide improved thermal conductivity, prevent material blockage and remove particulate build up wherever ash, dust, powders or granular materials are processed, generated, stored or transported.

The Biomass industry is just one of many that can benefit from our sound solution, yet there is a unique synergy between the technologies that seems to make a perfect combination – Biomass a green, low carbon footprint alternative to burning coal in power generation plants and Primasonics Quattro range of Sonic Soot Blowers, a green, non-polluting efficient means to prevent ash build up – and it is certainly proving to be the case!

Ash build up is not just a problem for very large power generation plants like Drax in England which has converted three of its six coal fired plants to biomass. Smaller plants such as Claymark have exactly the same problem in their biomass boiler. Claymark based in Rotorua, New Zealand are specialists in milling, manufacturing and distribution of high quality timber products.

The problem was essentially fouling of the biomass/wood waste fired boiler which provided hot water to the timber drying kilns. Increasing production meant higher volumes of wood waste and biomass being burnt which reduced the cleaning time from every six weeks to every ten days. This was having a major adverse effect on drying schedules as the plant has to be shut down for ten hours per week as well as loss of efficiency of the boiler during operation. This reduction equated to 7Mw MCR (Maximum Continuous Rating) to 4.5 Mw.

The company needed to find an innovative, effective and environmentally friendly solution and so made initial contact with Primasonics International. Primasonics through their Australian & New Zealand agents, Bulk Materials Handling obtained the necessary technical information and boiler drawings. They recommended the installation of two Sonic Soot Blowers with a 230 Hz frequency to be sounded together. As Claymark had no experience in the use of sonic sound waves they initially opted for the Primasonics Monthly Rental Plan and the equipment was despatched and installed as shown below.

In addition, to comply with local plant noise regulations acoustic covers were designed and installed.

After three months operation an inspection was made and no ash build up was found on the boiler tubes. The total project cost was easily fully recouped within the first year of operation and Claymark now have an efficient, green and environmentally friendly solution to their previous serious ash build up.

Primasonics International has been solving particulate build up and material flow problems in a wide range of industries and applications in around 60 counties worldwide.