Dongdong Feng

Effects of Water Molecule on CO Oxidation by OH: Reaction Pathways, Kinetic Barriers, and Rate Constants

The water dilute oxy-fuel combustion is a clean combustion technology for near-zero emission power; and the presence of water molecule could have both kinetic and dynamic effects on combustion reactions. The reaction OH + CO → CO2 + H, one of the most important elementary reactions, has been investigated by extensive electronic structure calculations. And the effects of a single water molecule on CO oxidation have been studied by considering the preformed OH(H2O) complex reacts with CO. The results show little change in the reaction pathways, but the additional water molecule actually increases the vibrationally adiabatic energy barriers (VaG). Further thermal rate constant calculations in the temperature range of 200 to 2000 K demonstrate that the total low-pressure limit rate constant for the water assisted OH(H2O) + CO → CO2 + H2O + H reaction is 1-2 orders lower than that of the water unassisted one, which is consistent with the change of VaG. Therefore, the hydrated radical OH(H2O) would actually slow down the oxidation of CO. Meanwhile, comparisons show that the M06-2X/aug-cc-pVDZ method gives a much better estimation in energy and thus is recommended to be employed for direct dynamics simulations.

Experimental study of cyclone pyrolysis – Suspended combustion air gasification of biomass

Based on the original biomass cyclone gasifier, the cyclone pyrolysis-suspension combustion gasification technology was constituted with a bottom wind ring to build the biochar suspension combustion zone. This technology decouples the biomass pyrolysis, gasification (reduction reaction) and combustion (oxidation reaction) within the same device. With the feed amount and total air fixed, the effect of air rate arrangement on temperature distribution of the gasifier, syngas components and gasification parameters was studied. With the secondary air rate (0.20) and bottom air rate (0.50), the gasification efficiency was best, with gas heating value of 5.15MJ/Nm3, carbon conversion rate of 71.50%, gasification efficiency of 50.80% and syngas yield of 1.29Nm3/kg. The device with biochar for the tar catalytic cracking was installed at the gasifier outlet, effectively reducing the tar content in syngas, with a minimum value of 1.02g/Nm3.