NUMERICAL ANALYSIS FOR THE LOW-EMISSION DUAL FUEL COMBUSTION IN A BOILER TYPE OP-230

This study focuses on a CFD modeling of co-firing environmentally friendly biomass-derived syngas with coal in an older PC-fired boiler of type OP-230 with low-emission burners on the front wall, still used in Poland as district heating units. The simulations were conducted to find the best technology to drive the boiler retrofit. Two types of syngas and natural gas, two heat replacements (5 and 15%) and two configurations (below and above boiler zone) of gas nozzles feeding the co-fuel into the boiler were modelled. The results were compared with the baseline values where a full load of coal is combusted. The most important results include (i) the NOx reductions relative to the baseline, their dependence on the nozzle configuration, heat replacement and the co-fuel type; (ii) the CO concentrations in the furnace; (iii) the co-fuel particles residence time in the combustion chamber; and (iv) the reduction in CO2 emissions. Greater NOx reductions at the furnace exit were achieved with nozzles located below the bottom row of burners and 15% heat replacement. The highest of them was 46%. For such an arrangement of nozzles, the syngas can be produced by gasification of waste containing such troublesome components as chlorine and alkali.