A new strategy for upgrading ventilation air methane emissions combining adsorption and combustion in a lean-gas turbine

Abstract

ABSTRACT This work evaluates the feasibility of harnessing a high-flow (4.4 Nm3/s) and low-concentrated (0.57% CH4) methane stream from a coal mine ventilation emission. Two consecutive processes have been coupled: a fixed bed adsorption used for methane concentration by temperature-swing adsorption, and a combustion process in a lean-gas turbine. Both processes have been simulated using rigorous mathematical model implemented in a commercial simulation package. Regarding the adsorption concentration step, optimized results showed the possibility of obtaining an outlet stream with 1.2% CH4 and a total flowrate of 3.8 Nm3/s. The gas turbine generates a net energy output of 490 kW and provides the heating required in the desorption step. The process design has been completed with an economic evaluation of the process. The estimated initial investment of the process is high (4.74 M€), and the return profitability depends a lot on the cost of the adsorbent material. The process would be profitable in a 20-year period with a 4.25% discount rate for an adsorbent cost lower than 0.6 €/kg.