Dr. Christian Steiner

Dr. Christian Steiner

Sales, Deputy Chief Executive Officer

How an intelligent retrofit has permanently reduced slag in a biomass power plant’s furnace – part 1 of 2

The Silbitz biomass power plant in Thuringia, Germany, produces 5.5 MW of electricity and 3 MW of district heat [a year] from waste wood. In order that production remains competitive, a high degree of availability at the plant is required. This was not satisfactory in Silbitz. The reason for this was the furnace: heavy slagging on the walls resulted in short traveling periods and frequent downtimes. Since 2011 four shock pulse generators have been cleaning the plant during ongoing operation. This has enabled the amount of slagging to be minimized and traveling periods to be lengthened in the long term.

Andree Michaelis, operations manager at the biomass power plant in Silbitz, comes straight to the point. “Since we started cleaning the furnace and radiation and convection passes regularly with our Shock Pulse Generators, we’ve kept boiler efficiency at a constantly high level throughout the entire traveling period.”

The biomass power plant went into operation in 2003. The vertical boiler consists of a furnace, radiation pass, convection pass and eco pass (see Figure 1). Engineering company Standardkessel Baumgarte did not envisage installing a system in the furnace and radiation pass for the removal of deposits during operation. From the start the superheater and eco passes were equipped with steam sootblowers (rotary and retractable soot blowers by Rosink).

Shock Pulse GeneratorFigure 1: boiler overview and installation positions of the Shock Pulse Generators at the Silbitz biomass power plant.

Boiler fouling caused frequent downtimes

After just a short period of operation the boiler showed signs of heavy fouling, however. In the furnace slagging and fouling often reached such a high level (see Figure 2) that the sheer weight caused it to fall away from the sides, dropping down and blocking the ash discharge or damaging the grate. As a result, the boiler had to be shut down for cleaning and repair respectively.

“The frequent downtimes massively reduced our boiler operating times. This was an untenable situation and we had to come up with some solutions,” states Mr. Michaelis. The plant operator found the answer at Explosion Power. Since October 2011 four EG10 Shock Pulse Generators have been up and running at the plant.

Shock pulse interval of 24 hours instead of eight sootblowers

The four Shock Pulse Generators (SPGs) cater for the entire boiler. The first prevents slagging and fouling in the furnace (see Figure 2), with the second tasked with cleaning the radiation pass. The third supplements the sootblowers in the convection pass and the fourth makes the sootblowers in the eco pass redundant.

By using SPGs in the furnace and radiation pass the flue gas temperature can be kept at a constantly low level at the convection pass inlet. This reduces the level of corrosion in the superheater bundles and improves the cleanability of the bundles.

In the convection pass only the sootblower between the two superheaters and the one between the superheater and evaporator are still in use. Thanks to the lower inlet temperatures the deposits left on the superheaters are less sticky. The tubes can be cleaned more easily and the sootblowers have to be used less frequently. For the first six weeks following a boiler overhaul the sootblowers in the convection pass do not have to be used at all.

The plant could fully retire the eight sootblowers in the economizer as a single Shock Pulse Generator with a shock pulse interval of 24 hours now does the job of all eight.

Marked increase in availability …

As the boiler is now automatically cleaned by the Shock Pulse Generators system availability has considerably increased, with downtimes reduced to a minimum. Mr. Michaelis says, “Between cleaning intervals the plant now always runs in the nominal load range. We’ve also been able to reduce the flue gas temperature at the furnace ceiling to a maximum of 850°C.” 

… and other considerable benefits

The shock pulse generators also lengthen the service life of the boiler and simplify the maintenance thereof. Mr. Michaelis explains further. “Unlike the sootblowers the shock pulse generators don’t cause any abrasion on the pipe surfaces. This meant that we could remove the protective shells on the eco tubes.”

As the sootblowers are used much less often, this has an effect on the overall balance of the biomass power plant. Electricity production has thus risen by 2%. In addition, less demineralized water has to be prepared. “As our sootblowers are being used much less frequently, we’ve been able to halve our water consumption,” smiles Mr. Michaelis.

Simple maintenance – by the customer on site

The biomass power plant in Silbitz has had its own service technicians trained in the maintenance of the Shock Pulse Generators. Thus means that they are able to carry out servicing of the SPGs themselves. This is due after 3,000 shock pulses or every twelve months. Spare and wear parts are bought directly from Explosion Power GmbH.

In part 2 you can read about how the plant operator tests the Shock Pulse Generators’ various modes of operation (single mode, pulse mode, etc.) and discover why the customer recently decided to install a fifth SPG

Biomass power plant in Silbitz

  • Boiler output: max. 27 MWth
  • Fuel input: approx. 55,000 t/a (waste wood A1–A4)
  • Gross electrical output: 5.6 MW
  • Annual net electricity output: 39,660 MWh/a

The power plant was built by Standardkessel Baumgarte and has been operated by PNE Biomasse GmbH since 2003. Four EG10 shock pulse generators have been in operation here since 2011, with a further SPGs added in 2017.

Biomass power plant in Silbitz

  • Boiler output: max. 27 MWth
  • Fuel input: approx. 55,000 t/a (waste wood A1–A4)
  • Gross electrical output: 5.6 MW
  • Annual net electricity output: 39,660 MWh/a

The power plant was built by Standardkessel Baumgarte and has been operated by PNE Biomasse GmbH since 2003. Four EG10 shock pulse generators have been in operation here since 2011, with a further SPGs added in 2017.

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