Xi Zeng

Kinetics and mechanism of direct reaction between CO2 and Ca(OH)2 in micro fluidized bed.

Even at present it is still difficult to characterize the reaction between CO2 and Ca(OH)2 at high temperature and atmospheric pressure using traditional instruments such as thermogravimetric analyzer and differential scanning calorimeter. This study was devoted to characterizing such a reaction in a newly developed micro fluidized bed reaction analyzer (MFBRA) under isothermal conditions in the temperature range of 773-1023 K. The results indicated that the MFBRA has not only a good adaptability for characterizing the above-mentioned reaction but enables as well a new insight into the mechanism of the reaction. An obvious time delay was identified for the release of the formed steam (H2O) in comparison with the onset of its CO2 absorption, which might be attributed to the formation of an unstable intermediate product Ca(HCO3)2 in the reaction process between CO2 and Ca(OH)2. The activation energy for forming Ca(HCO3)2 was found to be about 40 kJ/mol, which is much lower than that of the reaction between CO2 and CaO.

Industrial demonstration plant for the gasification of herb residue by fluidized bed two-stage process.

A fluidized bed two-stage gasification process, consisting of a fluidized-bed (FB) pyrolyzer and a transport fluidized bed (TFB) gasifier, has been proposed to gasify biomass for fuel gas production with low tar content. On the basis of our previous fundamental study, an autothermal two-stage gasifier has been designed and built for gasify a kind of Chinese herb residue with a treating capacity of 600 kg/h. The testing data in the operational stable stage of the industrial demonstration plant showed that when keeping the reaction temperatures of pyrolyzer and gasifier respectively at about 700 °C and 850 °C, the heating value of fuel gas can reach 1200 kcal/Nm(3), and the tar content in the produced fuel gas was about 0.4 g/Nm(3). The results from this pilot industrial demonstration plant fully verified the feasibility and technical features of the proposed FB two-stage gasification process.

A novel Ag3PO4/Nb2O5 fiber composite with enhanced photocatalytic performance and stability

A novel Ag3PO4/Nb2O5 fiber composite was fabricated through depositing Ag3PO4 nanoparticles on Nb2O5 fiber surfaces through a facile depositing precipitation approach. The as-prepared Ag3PO4/Nb2O5 photocatalyst was characterized through XRD, SEM, XPS and UV-Vis measurements. SEM results show that biomorphic Nb2O5 fibers have a wrinkled surface and porous walls. The special morphology of the Nb2O5 fibers provided a large amount of voids and interfaces in favor of decorating with Ag3PO4 nanocrystals. The Ag3PO4/Nb2O5 composite photocatalyst exhibits much higher photocatalytic activity for the degradation of rhodamine B than pure Ag3PO4 under simulated sunlight. Such superior photocatalytic activity is mainly attributed to enhanced visible light absorption and effective separation of photogenerated electron–hole pairs derived from the Ag3PO4/Nb2O5 heterojunction. No loss of photocatalytic activity has been observed after four recycles. Moreover, the large size of the Ag3PO4/Nb2O5 composite allows it to be easily separated from the solution.