Co-combustion of biomass and gaseous fuel in a novel configuration of fluidized bed: Combustion characteristics

Experimental study on co-combustion of rice straw and natural gas has been performed in a bubbling fluidized bed. The used combustor allows a novel jetting-fountain configuration and the conventional operation as well. In the jetting-fountain configuration, natural gas premixed with the air sufficient for combustion proceeds through the jet pipe to create a jet-fountain zone. Whereas only the air required for rice straw combustion passes through the gas distributor. The findings of the experiments confirm that smooth combustion of natural gas with rice straw can be performed in the novel jetting-fountain fluidized bed. This avoids acoustic effects and explosions of burning bubbles that occurs in the conventional operation. Natural gas contribution had a major impact on combustion characteristics and the performance of the combustor has been found to be much better when applying the jetting-fountain configuration. There are considerable reductions (up to 64%, 28% and 34%) in CO, NOx and SO2 emissions, respectively. The fixed carbon loss reduces (up to 65%) as well. Combustion efficiency records generally higher values with the jetting-fountain configuration. Combustion efficiency steadily improves with increasing natural gas contribution (up to 99.8%). Increasing bed temperature (up to 900 °C) is beneficial for reducing CO, decreasing fixed carbon loss and improving combustion efficiency. The existence of an optimum bed temperature for sulfur retention has been confirmed. As normal, NOx increases with bed temperature.