Experimental study on co-cofiring of rice straw and natural gas has been performed in a fluidized bed. The used combustor allows the novel, jetting-fountain configuration and the conventional operation as well. The experimental apparatus is mainly a bubbling fluidized bed of 300 mm ID and 3300 mm height equipped with a 38.1 mm ID jet-pipe located at the combustor center. In jetting-fountain configuration, natural gas premixed with the air required for its combustion proceeds through the jet pipe to create jet-fountain zone. Whereas only the air required for rice straw combustion passes through a gas distributor.
The findings of the experiments confirm that smooth combustion of natural gas with rice straw can be performed in the jetting-fountain fluidized bed. This avoids acoustic effects and explosions of burning bubbles that occurs in conventional operation.
The performance of the combustor has been found much better when operates at the jetting-fountain configuration. Temperature measurements in the freeboard demonstrate that the jetting-fountain fluidized bed dampens greatly the freeboard overheating. The fountain-particles absorb a great part of heat released in freeboard and recover it back to the bed. The later hypothesis is confirmed by measuring the in-bed cooling load that was found considerably increase, in particular, at lower bed temperature.
There is also a considerable reduction in different emissions including carbon monoxide, nitric oxides and sulfur dioxide. The fixed carbon loss reduces as well. Combustion efficiency records higher values with jetting-fountain configuration.
Increasing bed temperature is beneficial for reducing carbon monoxide, decreasing fixed carbon loss and improving combustion efficiency. Existence of an optimum bed temperature for sulfur retention has been confirmed. As normal, nitric oxides has been found increases with bed temperature.