Investigation of VPSA process with 13X and MIL-120(Al) for hydrogen purification from RDF gasification

Hydrogen is nowadays perceived as a clean and valuable fuel and feedstock for many industrial applications since it is used for many essential chemical processes, such as crude oil refining, synthesis of ammonia and methanol and also as a fuel for fuel cells in transportation. Currently, most of hydrogen (∼95%) is produced from fossil fuels by steam reforming of methane, partial oxidation of heavier hydrocarbons or coal gasification, respectively. Other production processes include water electrolysis and biomass gasification. Beside these processes, municipal waste is considered as potential source of high-energy fuel fraction in gasification processes. Indeed, municipal waste can be used to produce Refuse Derived Fuel (RDF) - an alternative, high-calorific solid fuel - which can be gasified to produce a gas mixture with a hydrogen concentration around 30%vol requiring separation processes to produce pure hydrogen.
In this study, we investigated the use of (V)PSA processes to purify hydrogen produced from gasification of RDF. The gas mixture considered is composed of 30% of H2, 40% of CO2, 25% of CO and 5% of CH4 for a total flowrate of 1273 Nm³/h. Several configurations are investigated for the use of adsorption process: direct treatment of the feed gas or treatment of the H2 preconcentrated gas after membrane unit. Several (V)PSA configurations are investigated: classical Skarström cycle, 3-bed-6step cycles as well as more complex ones with a commercial zeolite 13X and with a promising MOF, MIL-120(Al) which can be produced at kiloton scale for a production cost estimated at 13 $/kg [1]. Experimental measurements (adsorption isotherms and breakthrough curves) have been performed in ordrer to determine thermodynamic and kinetic parameters required for the simulation of VPSA process in Aspen Adsorption.
The objective is to compare several configurations in terms of H2 recovery, energy consumption and cost to produce hydrogen with two grades of purity: 90% and 99.9%. The first results are promising, allowing to produce 99.9% purity hydrogen with a recovery around 95% by using VPSA after a membrane unit.