The direct deoxygenation effect of CaO on bio-oil during biomass pyrolysis in a fluidized-bed reactor was studied. Bio-oils were produced from white pine in the presence and absence of CaO at 520 °C and a carrier gas flow rate of 50 L/min (standard temperature and pressure). The results showed that the oxygen content of the organic components in the bio-oils was 39, 39, 39, 36, 32, and 31 wt % for white pine alone and white pine accompanied with CaO at CaO/biomass mass ratios of 1, 2, 3, 4 and 5, respectively. At a CaO mass ratio of 5, the relative reduction of oxygen content in the bio-oil reached 21%. Detailed gas chromatography−mass spectrometry analysis showed that the relative abundances of high oxygen content laevoglucose, formic acid, and acetic acid were highly reduced by CaO, indicating direct fixation of “the active quasi-CO2 intermediates” produced during biomass pyrolysis. Furthermore, the relative abundances of furfural, furfuryl alcohol, etc., mainly derived from dehydration reactions, all increased, showing that CaO addition could also catalyze dehydration reactions. X-ray diffraction and Fourier transform infrared analyses of the solid residues prepared by a thermal balance confirmed the direct fixation of the active quasi-CO2 intermediates and showed that some organic calcium salts appeared at 350 °C, which would decompose below 400 °C to form easily regenerated CaCO3. This further confirmed the feasibility of CaO recycling for in situ deoxygenation of bio-oil.

No abstract

Experiments were carried out in a multipath air inlet one-dimensional furnace to assess NO x emission characteristics of the staged combustion of anthracite coal. These experiments allowed us to study the impact of pulverized coal fineness and burnout air position on emission under both deep and shallow air-staged combustion conditions. We also studied the impact of char-nitrogen release on both the burning-out process of the pulverized coal and the corresponding carbon content in fly ash. We found that air-staged combustion affects a pronounced reduction in NO x emissions from the combustion of anthracite coal. The more the air is staged, the more NO x emission is reduced. In shallow air-staged combustion (f M ) 0.85), the fineness of the pulverized coal strongly influences emissions, and finer coals result in lower emissions. Meanwhile, the burnout air position has only a weak effect. In the deep air-staged combustion (f M ) 0.6), the effect of coal fineness is smaller, and the burnout air position has a stronger effect. When the primary combustion air is stable, NO x emissions increase with increasing burnout air. This proves that, in the burnout zone, coal char is responsible for the discharge of fuel-nitrogen that is oxidized to NO x . The measurement of secondary air staging in a burnout zone can help inhibit the oxidization of NO caused by nitrogen release. Air-staged combustion has little effect on the burnout of anthracite coal, which proves to be suitable for air-staged combustion.

No abstract