Concept of co-firing coal with biomass and natural gas: On track of sustainable solution for future thermal power plants

This paper presents R&D project of multi fuel concept (MFC) for future coal-based power plants, demonstrated on example of cofiring Middle-Bosnia brown coal with waste woody biomass and natural gas. Pulverised Combustion (PC) lab-scale furnace has been used for the cofiring tests, varying up to 20%w portion of biomass and up to 10%th portion of natural gas in the fuel mix. Tests were purposed to optimize the combustion temperature, air distribution, including Over Fire Air System (OFAS), fuel combination and fuel distribution, including reburning concept, as function of emissions and combustion efficiency estimated through the ash deposits behaviours and unburnt. Considering application of proposed MFC in case of TPP Kakanj unit 6 (118 MWe) set here as a referent power plant, temperature levels and fuel distributions for lowest emissions of CO2 and NOx were found during lab tests, provided that combustion efficiency is at an acceptable level. Derived research results yield input data for calculation sustainability indicators of MFC for the referent power plant, considering 6 fuel options - different combinations of coal, biomass and natural gas. Single criteria analysis and multicriteria sustainability assessment have been done, giving an advantage to the options of cofiring coal with woody biomass and natural gas in the case demonstrated