Xue-min Yang

Emissions of SO2, NO and N2O in a circulating fluidized bed combustor during co-firing coal and biomass

This paper presents the experimental investigations of the emissions of SO2, NO and N20 in a bench scale circulating fluidized bed combustor for coal combustion and co-firing coal and biomass. The thermal capacity of the combustor is 30 kW. The setup is electrically heated during startup. The influence of the excess air, the degree of the air staging, the biomass share and the feeding position of the fuels on the emissions of SO2, NO and N2O were studied. The results showed that an increase in the biomass shares resulted in an increase of the CO concentration in the flue gas, probably due to the high volatile content of the biomass. In co-firing, the emission of SO2 increased with increasing biomass share slightly, however, non-linear increase relationship between SO2 emission and fuel sulfur content was observed. Air staging significantly decreased the NO emission without raising the SO2 level. Although the change of the fuel feeding position from riser to downer resulted in a decrease in the NO emission level, no obvious change was observed for the SO2 level. Taking the coal feeding position R as a reference, the relative NO emission could significantly decrease during co-firing coal and biomass when feeding fuel at position D and keeping the first stage stoichiometry greater than 0.95. The possible mechanisms of the sulfur and nitrogen chemistry at these conditions were discussed and the ways of simultaneous reduction of SO2, NO and N20 were proposed.

HREM observations of the synthesized process of nano-sized SiC by ball milling of Si and C mixed powders

Abstract The synthesis of nano-sized SiC through ball milling (BM) of elemental Si and graphite mixed powders at room temperature has been reported, and detailed reaction process has been characterized by high-resolution electron microscopy (HREM). High-resolution electron microscopy (HREM) observations presented herein suggest that amorphous graphite (a-graphite), amorphous silicon (a-Si) and nano-sized crystalline Si (c-Si) with many defects are produced during BM, which is prerequisite to the reaction. In some areas, SiC is synthesized through a diffusion of C atoms into the a-Si/and c-Si. In the former, a-Si(C) forms, and then mechanically-driven crystallization of the a-Si(C) occurs to form SiC. In the latter, C atoms directly replace Si atoms to form SiC with an orientation relationship of (111)SiC//(111)Si. In other areas, localized self-sustained reaction occurs to form slightly larger SiC grains.

Calculating models of mass action concentrations for NaBr（aq）, LiNO3（aq）, HNO3（aq）, and KF（aq） binary solutions

The calculating models of mass action concentrations for electrolyte aqueous solutions NaBr-H2O, LiNO3-H2O, HNO3-H2O, and KF-H2O have been developed at 298.15 K and their molalities ranging from 0.1 mol/kg to saturation according to the ion and molecule coexistence theory as well as mass action law. The calculated mass action concentration is based on pure species as the standard state and the mole fraction as the concentration unit, and the reported activities are usually based on infinite dilution as the standard state and molality as the concentration unit. Hence, the calculated mass action concentration must be transformed to the same standard state and concentration unit. The transformation coefficients between calculated mass action concentrations and reported activities of the same component fluctuate in a very narrow range. Thus, the transformed mass action concentrations not only agree well with reported activities, but also strictly obey mass action law. The calculated results show that the new developed models can embody the intrinsic structure of investigated four electrolyte aqueous solutions. The results also indicate that mass action law has its widespread applicability to electrolyte binary aqueous solutions.

Critical Evaluation of Prediction Models for Phosphorus Partition between CaO-based Slags and Iron-based Melts during Dephosphorization Processes

According to the experimental results of hot metal dephosphorization by CaO-based slags at a commercial-scale hot metal pretreatment station, the collected 16 models of equilibrium quotient

Universal thermodynamic model of calculating the mass action concentrations of omponents in a ternary strong electrolyte aqueous solution and its application in the NaCl-KCl-H2O system

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Localized amorphization in SiC induced by ball milling

kP or phosphorus partition

High-resolution electron microscopy observations of microplastic fracture in SiC under ball milling at room temperature

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