NOx emission characteristics of fluidized bed combustion in atmospheres rich in oxygen and water vapor for high-nitrogen fuel

The figure clarifies that the added steam obviously decreased the NOx emission, shown with NOx concentration in flue gas, at relatively low O2 content, such as below 40 vol.% in the figure, because of its diluting the O2 concentration in the combustion atmosphere, shortening the gas-solid reaction time inside the reactor and suppressing the release of volatile and N species from fuel particles. At excessively high O2 content in the combustion agent, say, above 40 vol.%, however, the added steam would be oxidized to form more OH radicals, which thus increased the oxidation capability of the combustion atmosphere to cause conversely the higher NOx emission than the case without steam addition.154