WASTE TO ENERGY
Schematic showing the shock pulse generator (SPG) and the real installation at a boiler
An expert in this technology, Explosion
Power, has developed a DCS-controlled, online boiler cleaning solution, automatically generating shock pulses (SPs) by shock waves. Due to the spherical impact of the shock wave, deposits are removed from wall surfaces and bundle tubes upstream and downstream of the installation location. Te shock waves are created by instant-combustion of a few grams each of a mixture of burnable gas (natural gas or methane) and pure oxygen. Tis act is carried out automatically and outside of the boiler in a pressure-resistant device. Te resulting shock wave is jet shot into the boiler. Locally the flue gas, the internal boiler tubes and walls are put into a short oscillation and the deposits are cleaned off. Te entire SP takes few milliseconds.
Te shock pulse generators (SPGs)
are designed for shock wave cleaning in a variety of industrial applications. Four different sizes can cover most
application cases. Te smallest unit of the EG series has a filling volume of the combustion chamber of 2.5 litres. Te filling volume of gas comprises 16g of methane and equivalently 34g of oxygen required for the ideal combustion per SP. Approximately 350 SPs can be generated from a standard 200 bar gas cylinder. If an SP is generated every two hours, the gas cylinders last for approximately one month before needing to be exchanged. Te SPG is mounted on the outside of the boiler wall. Installation is easy, because the unit is installed on a nozzle of DN 125 and the whole installation and maintenance space requires approx. 1.5m3
dismantled, and the boilers were since then cleaned by SPGs only and activated from the plant’s central control system. Te travelling time of the boilers increased, which means more energy may be used for power production and no manual intervention into the boiler for cleaning during operation is needed.
. Te larger units are designed with larger combustion chamber of 3.5 litres, 4.4 litres and 7.7 litres. Te power of the shock wave is effective between 3m and approximately 15m, meaning that one SPG can typically clean a complete radiation pass, or two neighbouring tube bundles. Should the boiler width be larger, then two SPGs can be installed at opposite walls and the SPs can be activated simultaneously or alternately.
THE INITIAL INSTALLATIONS Te first installation was carried out in 2009. At three boilers of the waste- to-energy (WtE) plant at Lucerne in Switzerland, the eight installed SPGs proved to clean the boilers to satisfaction. Due to this positive result, the previously installed cleaning systems were completely
ONGOING IMPROVEMENTS Since 2009 nearly 700 units have been installed worldwide for cleaning of different boiler types and sizes. Tey have been used for cleaning horizontally and vertically arranged tube bundles as well as finned tubes and boiler walls. Tere is no abrasion of the inside of the boiler. Even refractory-lined boiler internals are not damaged and can be efficiently cleaned. Explosion Power is continuously
improving the product. In 2017, a new development was initiated, where instead of oxygen, compressed air is used. Compressed air can either be supplied in gas cylinders or generated by an auxiliary air compressor unit in the plant itself. And in August 2020 new SPG types, SPGr10 and SPGr16, were launched.
Mirek Spicar is with Explosion Power.
www.explosionpower.ch
www.engineerlive.com 47
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