Mirek Spicar reveals how a Swiss WtE plant relies on the latest technology for boiler cleaning.
Renergia Luzern has gained the best operating experience with boiler cleaning by means of Shock Pulse Generators (SPG) and finally decided to upgrade the entire plant with the latest development of this technology.
A brief overview of the requirements
The Renergia Luzern WtE plant consists of two parallel lines, which were commissioned in 2015. The plant concept was designed for a capacity of 58 t/h steam at 410°C/41 bar for each of the boilers. As the WtE plant is located on the site of a paper mill, steam production was primarily focused on the generation of electricity and industrial steam. The low-pressure steam was used to supply district heating to a nearby residential area. Additional energy was required as district heating was gradually expanded to other areas. An increase to the current 2 x 70 t/h was only an option if the boiler would remain clean throughout the entire operating period.
Long-term experience with the setup
The operator decided to work closely with Explosion Power - which has commercialised over 1,000 units worldwide to date – to optimise boiler cleaning using an automated system from the latest development of SPGs. The four-pass boiler consists of three vertical passes and one horizontal pass. Proven experience with the initial development of the SPG series in the vertical passes, which at the time operated on natural gas and pure oxygen, encouraged the operator to continue the expansion with the updated SPGr series, which requires less maintenance and uses compressed air instead of oxygen for operation.
Satisfaction with the system
Since August 2021, three SPGr units per boiler have been installed in the horizontal pass. The task is to clean the convection evaporator and superheaters to minimise the pressure drop across the bundles and to keep the temperature of the last superheater below 625°C, i.e., to keep the bundles clean. All requirements are well met. The shock pulses (SP) – lasting for few milliseconds only – are generated sequentially about twice per hour. The SPGr are fed by a stoichiometric ratio of a few grams of natural gas and compressed air. After having only positive experience with the SPGr, the operator decided to replace the originally installed SPG in the vertical passes with the equivalent SPGr. The WtE plant is now equipped with a total of 12 SPGr units of the same type. All functions are generated automatically, and steam production remains at a constant level throughout the operating period. Each boiler operates for two years without manual cleaning.
The chief maintenance manager, Markus Benz summarises as follows: “The SPGr are reliable, easy to operate and cost-effective.”
Mirek Spicar is with Explosion Power.