Hydrogen production from steam gasification of polyethylene using a two-stage gasifier and active carbon

Abstract

Steam gasification of polyethylene was conducted using a two-stage gasifier consisting of a fluidized bed gasifier and a tar-cracking reactor filled with active carbon. The main aim of the work was to produce H2-rich syngas and simultaneously reduce tar. The main reaction variable was the steam-to-fuel ratio. The possibility of gasification without using an electrostatic precipitator was also examined in the study. In addition, the effect of the type of distributor (hook-type and mesh-type distributor) located between the fluidized bed gasifier and tar-cracking reactor on coke formation was investigated. Finally, the possibility of in situ regeneration of active carbon with steam was explored. As a result, the syngas from the two-stage gasifier contained a maximum 66 vol% hydrogen and a minimum 0 mg/Nm3 tar. The syngas produced without using an electrostatic precipitator had similar quality to that obtained with an electrostatic precipitator, providing a positive indication for the implementation of the two-stage gasifier in commercial applications. Additionally, the mesh-type distributor was found to be excellent against coke formation. The in situ regeneration of active carbon with steam significantly recovered the textural properties of the original active carbon, yielding a surface area recovery rate of approximately 63%. A long-term gasification for 4 h with repetitive in situ regeneration of active carbon with steam produced a syngas having 55 vol% H2 on average and toluene as a tar component.