Conversion Characteristics of Aromatic Hydrocarbons in Simulated Gaseous Atmospheres in Reducing Section of Two-Stage Entrained-Flow Coal Gasifier in Air- and O2/CO2-Blown Modes

摘要

Conversion of refractory aromatic hydrocarbons was studied with an atmospheric flow reactor that simulated the reducing section of a two-stage entrained-flow coal gasifier in air-blown and O2/CO2-blown (CO, recycling) modes at temperatures of 1100—1400 °C. Mixed vapors of benzene and naphthalene (7/3 on a carbon basis) were fed into the reactor at total concentration in a range from 3.7 to 37 g·Nm~(-3) together with a CO—CO2-H2-H2O mixture in the O2/CO2-blown mode or CO—CO2—H2—H2O—N2 mixture in the air-blown mode. Soot was the major fate of the aromatics at the inlet benzene/ naphthalene concentration of 35—37 g·Nm~(-3), and its yield was not influenced significantly either by the mode of gasification or temperature at 1200—1400 °C. The contribution of gas-phase reforming to the conversion of the aromatics became more important as their inlet concentration decreased. At the inlet concentration of 3.7—7.5 g·Nm~(-3), the O2/CO2-blown mode was clearly more effective in reducing the soot yield than the air-blown mode and increasing the gas yield. It was explained on the basis of a detailed chemical kinetic model that the increased partial pressure of CO2 induced a higher concentration of key active species such as hydroxyl radicals that initiated the oxidative decomposition of the aromatics.