Carbon monoxide and nitric oxide concentrations in flue gas during combustion of agricultural biomass in the residental boiler

Concentrations of carbon monoxide and nitric oxide (in mg/m3 and presented for 10% O2) in the flue gas from firing hay and palm kernel shell pellets, as well as a mixture of coffee husk pellets and wood pellets at the weight ratios of 70:30 and 30:70 in a rotary furnace with a 20 kW nominal heat output amounted to: 695.102; 3492.271; 2921.165; 18344.244; 5297.315, respectively, for the boiler operating with minimum heat output, and 568.192; 2400.341; 4065.275; 20696.380 and 2272.123, respectively, for the boiler operating at a heat output close to maximum. The value of carbon monoxide concentration was proportional to the amount of slag generated during the combustion process and the value of nitric oxide concentration was proportional to the nitrogen content in the fuel. Variation of parameters in time: temperature in the combustion chamber, carbon monoxide and nitric oxide concentrations, oxygen concentration and air excess ratio while firing wood and agricultural biomass pellets were indicated. Correlation between nitric oxide and carbon monoxide concentrations as well as carbon monoxide and nitric oxide concentration versus oxygen concentration and temperature in the combustion chamber were presented. Agricultural biomass pellets should be mixed with wood pellets to improve combustion process and reduce carbon monoxide and nitric oxide concentrations. Pollutant concentration measurements were performed in real-life conditions resembling the ones experienced by boiler end-users.