In response to the deposition problem in biomass-fired boiler, inert addictive was tested to inhibit the possibility of coking. The deposition samples collected from final and primary superheater of biomass-fired CFB (circulating fluidized bed) boiler were grinded into fine powder. The inhibitive ability of additive was tested by mixing the deposition sample with different proportions of inhibitor under high temperature. By means of scanning electron microscope (SEM), X-ray diffraction (XRD) and other analytical procedures, the properties of the samples with inhibitor such as microstructure, composition were studied. The inhibitor was also introduced to the industrial biomass CFB boiler to verify its inhibition effect on superheater deposition. Unfortunately, the effect of adding inhibitor in industrial boiler is not certain, though the inhibitor added to the samples is obviously effective in weakening coking in the laboratory scope.
As the first step in coal combustion and gasification, coal devolatilization has significant effect on reaction process. Previous coal devolatilization models have some disadvantages, such as poor flexibility, model complexity, and requirement of characterization parameters. Recently, Sommariva et al. have proposed a multi-step kinetic model of coal devolatilization. This model avoids the disadvantages mentioned above and can predict elemental composition of tar and char. In this paper, the mechanism of this model has been revised for simple application to Chemkin. Revision method is that some reactions are split into more reactions by using one pseudo-intermediate-product to replace several final products. Simulation results show that calculation results from revised mechanism compare quite well with that from original mechanism and have good agreement with experimental data. The revised mechanism is accurate and can be applied to Chemkin very easily, which gives it wide application to simulation of coal pyrolysis, gasification and combustion.
Using zinc chloride solution and ammonia (25%) as raw material, with the presence of surfactant (CTAB), the microrod ZnO material was synthesized by the hydrothermal method. The phase composition and microstructure of the prepared ZnO material were characterized with XRD and SEM. The results show that the ZnO material possesses a high degree of crystallization, its diameter below 4 μm, and its length about 35 μm. The gas sensing property of gas sensor fabricated with the prepared ZnO material was evaluated via the static volumetric method. At the operating temperature of 200°C, the gas sensor has high sensitivity and selectivity to CH3COCH3.The gas sensing characterization was also discussed.
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