Influence of ammonium dihydrogen phosphates additive on potassium fixation capacity and ash fusibility for rice straw combustion in an O2/CO2 atmosphere
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Graphical Abstract
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Abstract
Particle agglomeration, fouling on the heating surface and other issues are closely related to the alkali metals during biomass thermo-chemical conversion. The potassium fixation ability and ash fusing characteristics in the combustion of rice straw (RS) added with ammonium dihydrogen phosphate (NH4H2PO4) were studied in a 21%O2/79%CO2 atmosphere. The reaction residue from the experiment in a drop tube furnace was analyzed with inductively coupled plasma atomic emission spectrometer (ICP-AES), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The potassium retention ratio of co-combustion of RS and NH4H2PO4 is higher than that of RS alone, especially at 900℃, and the retention ratio increases from 14.65% to 68.79%. The reaction between NH4H2PO4 and alkali metals in rice straw leads to the formation of KPO3 at 700 ℃ and K2CaP2O7 at 900℃, which is a high melting point compound. SEM analysis on residue indicates the agglomeration is inhibited, and the ash fusion temperature of RS is increased by adding NH4H2PO4. These results can be helpful to the research and development of high-alkali biomass clean utilization process.
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