Polaniec (PO) is the World’s largest 100% solid biomass firing CFB boiler operating today (190 MW el. gross, 447 MWth) . Previously owned by ENGIE, it is now managed by the Polish state (ENEA).
The plant uses agricultural biomass in addition to virgin biomass and the combustion technology is a Circulating Fluidized Bed boiler . The steam cycle has a single reheat, for 175 MWel. net/447 MWth, SH/RH 158/135 kg/s, SH/RH 535/535ºC and 127/20 bar . Steam temperature is limited to reduce potential issues of hot temperature corrosion.
To cope with agglomeration, fouling and corrosion, typical concerns with in agro biomass combustion, the boiler technology was adapted as follows :
- use of active bed materials and application of additives with worst quality agro (kaolin and elementary sulphur may be fed into the combustor to control agglomeration, fouling and hot corrosion )
- conservative flue gas velocities,
- effective temperature control (homogenous) in the combustion chamber,
- correct flue gas temperature (to avoid ash melting) in the convective sections, to reduce fouling and corrosion,
- proper design for the convective heat transfer surfaces (spacing, pitch etc.),
- proper fuel quality management and boiler diagnostic tools,
- in the combustion chamber: use of a step grid, use of the wall kick out at fuel inlet, use of the final SH and RH as Intrex (TM): integrated steam cooled solid separator and return leg.
The plant operates with a range of biomass according to the mix: 80% clean forestry wood chips and 20% of agro-fuels such as PKS, straw, sunflower pellets, dried fruit (marc).
The Design Fuel Mixture was analysed with BIOFACT, in order to evaluate operational risks (especially related to inorganic matter).
The result is presented below.
The Design Fuel Mixture is expected to induce relatively low high temperature fouling on heat exchangers (6/100) and a relatively low agglomeration risk (8/100). High temperature corrosion (19/100, low with respect to 100% agro-firing) still shall be monitored (e.g. evaluate KCl presence in flue gases). Emissions are not expected to be a problem (primary and secondary reduction measures can be defined). Fuel logistic can be critical for high moisture wood chips and depending, for example, on the physical properties of the agro-fuels used in the fuel mix.
The same boiler manufacturer shall provide a 299 MWel CHP plant (Tees Renewable Energy Project) to MGT Teesside (U. K.), therefore larger than Polaniec boiler, but operated with virgin wood pellets (70%) and wood chips (30%, forest by products from North America) . Differently from Polaniec, this boiler design has been developed to fire “easy-to-burn biomass” . Steam data are 229/205 kg/s, SH/RH 176/43 bar, 568/568°C. The plant shall be in operations in 2020 . Fuel data are not yet available.
 Natunen et al., First operating experiences of 55 MWel Konin and 205 MWel Polaniec CFB boilers firing 100% biomass, Amec Foster Wheeler Energia Oy.
 Barišić et al., Modeling of Fouling in CFB Boilers, Foster Wheeler Energia Oy, Presented at 11th International Conference on Fluidized Bed Technology Beijing China 14 – 17 May, 2014.
 Nuortimo et al., Large scale utility CFB technology in worlds largest greenfield 100% biomass power plant, Amec Foster Wheeler Energia Oy, Presented at 25th European Biomass Conference and Exhibition, 12-15 June 2017.