COMBUSTION AND FUEL FLEXIBILITY DURING CO-FIRING OF FOSSIL FUELS WITH BIOMASS FOR SUSTAINABLE POWER GENERATION

On 23rd Oct. 2014, EU leaders committed by 2030 to reduce greenhouse gas emissions by at least 40%, and increase energy efficiency and renewable energy by at least 27%. At the same time, European electricity sector is striving to reach a carbon-neutral power supply by 2050. But many challenges are still ahead on the road to "zeroemission year 2050". Growing share of the renewable energy sources (RES) brings about far-reaching consequences that affect the way electricity systems are operated. The following questions are raised, among others: How can the electricity system balance variable RES? How flexible is the existing generation park? Research described in this paper focuses on the co-combustion process carried out at different fuels types and process regimes that are flexibly changed during real time of the process without the loss of stability and process shut down. Investigation results are presented for two types of combustors: fluidized-bed (BFB) combustor and pulverized fuel (PF) combustor. Combustion performance and emission issues are presented during flexible change of combustion regimes from air-into oxy-combustion regime in fluidized bed auto-thermal combustor with different fuels, including biomass. Moreover, impact of flexible change of co-fired biomass type on combustion performance and emission issues are presented and discussed during co-combustion of pulverized coal with biomass willow (salix viminalis), Mass fraction of biomass in the total fuel flow was kept at 15%. Flexible change of combustion regime or/and fuel type resulted not only change in emission but also influenced such technical issue as feeding process, temperature profile in the combustion chamber and other process parameters. The results of the research confirmed the readiness of BFB technology as well as PF multifuel combustion as a base for flexible power units fired with fossil fuels and biomass. Fuel flexibility as well as flexibility of the operation conditions (different load ratios, dynamic characteristics, atmospheric and pressurized combustion conditions) was reached and documented. Additionally, Flexi-burn (TM) procedure has been successfully tested for pressurized combustion and biomass co-firing under BFB conditions.