Experimental study and demonstration of pilot-scale oxy-coal combustion at elevated temperatures and pressures

Highlights: • High pressure oxy-fuel firing of coal-water slurry was demonstrated up to 300 kW. • The combustor temperature significantly impacted the carbon burnout efficiency. • The radiative heat flux ranged from 108 to 279 kW/m². -- Abstract: High pressure oxy-fuel firing is a promising next-generation combustion technology for electricity generation, allowing net efficiency improvement compared to traditional oxy-fuel firing systems. Oxy-coal combustion has been extensively investigated at ambient pressure, but limited experimental data is available regarding this combustion method at elevated pressures at pilot or full scale. The study presented here investigates the operational performance of a high pressure, high temperature pilot-scale oxy-fuel combustor. Pulverized Utah bituminous coal in form of coal-water slurry was combusted at pressures up to 14 bar, temperatures up to 1600 °C and firing rates up to 300 kW. Eight different runs were selected for presentation and the measurements include flue gas composition (CO, CO₂, CH₄, SO₂, O₂), carbon and sulfur content of fly ash, combustor temperature profile and flame radiation profile. The flame radiation measurements were carried out with a novel narrow beam radiometer which measures local radiant heat flux at a specific location in the combustor. The radiation ranged from 108 to 279 kW/m² depending mainly on combustor temperature. Additionally, the temperature significantly impacted the carbon content of fly ash: 2.66% was measured near 1600 °C, while the concentration increased to 36.7% when the temperature was decreased to 1300 °C. The successful experimental demonstrations showed that increasing pressure is a viable combustion method and a step towards enhancing the efficiency in oxy-fuel firing based power plants.