Gases for Life
PRACTICAL FOCUS
Shock pulse with cleaning effect
By the Editorial Team
Smoke and ash are unavoidable products in any combustion process. The generation of larger quantities results in the formation of deposits. In boiler facilities, these layers can be removed with a shock pulse.
In many industrial processes, the hot flue gas from combustion is used to generate energy in boiler facilities. For example, these facilities have built-in heat exchangers that are used to generate turbine steam or district heating. Such boilers are found in waste incineration plants, coking plants, cement works and elsewhere. However, the flue gas contains greater or lesser amounts of soot and ash particles. As they flow past, they are deposited on the boiler walls and built-in elements such as the heat exchanger. Deposits of this kind hinder heat transfer, gradually reducing the efficiency of “heat generation”.
Cleaning with shock pulses instead of steam
The Shock Pulse Generator (SPG) produced by Swiss manufacturer Explosion Power is capable of removing deposits from large areas or entire boiler facilities. The device is installed in an existing boiler opening such as a connecting piece or a manhole. As the latter’s name suggests, it is used as an access hatch by engineers when carrying out inspections inside the boiler. Conventional cleaning systems have their shortcomings. The burned-on layers often have to be removed manually – with the boiler process disrupted to some extent during cleaning. The soot blowers that are frequently used for this are not very flexible and less efficient. One can think of them as oversized steam jet cleaners that are permanently installed in the boiler wall. The discharge nozzles for the hot cleaning steam are housed in a movable part such as a lance. This means that they can only steam-clean a very limited area. Numerous soot blowers are therefore required for larger facilities and installations.
Elegant vibration
The SPG uses a very simple physical principle: solids can be made to vibrate, for example by strong shock pulses. These pulses induce a sound wave in the solid caking, generating a short-localized suction effect and causing the contaminated pipes to vibrate briefly. When a boiler wall or heat exchanger starts to vibrate in this way, it causes the deposits to come off the surfaces. This method of cleaning is not only much more elegant and straightforward than the use of soot blowers, it is also much more effective. This was demonstrated, for example, at the Cokenergy coking plant in East Chicago (USA), where 192 soot blowers on 16 heat recovery boilers were recently replaced by 32 SPGs; the plant’s efficiency was also increased as a result. The process involves shock pulses being generated by means of controlled combustion. This is achieved by introducing small amounts of methane and oxygen into the SPG’s combustion chamber and igniting them. The shock pulses are not generated in the boiler itself but outside it in a robust, pressure-resistant vessel, the Shock Pulse Generator. The shock pulses are instantaneously guided through a discharge nozzle to the “target area”, where they can deliver their cleaning effect. This takes place while the boiler process is running, on average once an hour – depending on the level of contamination in the boiler. Since cleaning is thus continuous, no significant deposits can form in the first place where surfaces are treated in this way. This in turn helps to optimize boiler efficiency. Cleaning does not involve the use of steam, thereby avoiding the erosion and corrosion that would be encouraged by the steam jet. Explosion Power has now installed more than 600 SPGs worldwide.