Stone Dust Looping for Ventilation Air Methane Abatement: A 1 m3/s Pilot-Scale Study

Abstract

Ventilation air methane (VAM) emissions are a significant contributor to fugitive greenhouse gas emissions at underground coal mines. The stone dust looping (SDL) process is a novel technology developed at The University of Newcastle, Australia, for VAM abatement. The SDL process is a cyclic process in which calcium oxide (CaO) is first obtained from the calcination of limestone (CaCO₃). CaO is then used to simultaneously oxidize VAM (methane concentrations of 0.1–1 vol % in air) and capture carbon dioxide (CO₂) produced to form CaCO₃. The two cycles can be performed in a single reactor, or the process can be performed continuously in dual interconnected reactors. Preliminary experiments on the SDL process have previously been performed at laboratory scale. In this study, further laboratory-scale studies were conducted in conjunction with pilot-scale SDL investigations in a single 1 m³/s fluidized bed reactor. The effect of inventory size (1–2 tonnes of CaCO₃), operating temperature (565–700 °C), and flow rate (1–1.7 m³/s) on methane conversion was investigated. At temperatures of 600 °C and above, >99.5% methane conversion was achieved for all inventory sizes and flow rates examined. At temperatures of 565 and 575 °C, 41 and 70% methane conversions were achieved, respectively. VAM fluctuation experiments were performed, and it was shown that a fluid bed can act as a thermal mass to reduce fluctuations in the bed temperature as the VAM concentration changes.