Techno-economic prospects of small-scale membrane reactors in a future hydrogen-fuelled transportation sector

摘要

The membrane reactor is a novel technology for the production of hydrogen from natural gas. It promises economic small-scale hydrogen production, e.g. at refuelling stations and has the potential of inexpensive CO_2 separation. Four configurations of the membrane reactor have been modelled with Aspen~(plus) to determine its thermodynamic and economic prospects. Overall energy efficiency is 84%_(HHV) without H_2 compression (78% with compression up to 482 bar). The modelling results also indicate that by using a sweep gas, the membrane reactor can produce a reformer exit stream consisting mainly of CO_2 and H_2O ( > 90%_(mol)) suited for CO_2 sequestration after water removal with an efficiency loss of only 1%_(pt). Reforming with a 2 MW membrane reactor (250 unit production volume) costs 14 $/GJ_(H_2) including compression, which is more expensive than conventional steam reforming + compression (12 $/GJ). It does, however, promise a cheap method of CO_2 separation, 14 $/t CO_2 captured, due to the high purity of the exit stream. The well-to-wheel chain of the membrane reactor has been compared to centralised steam reforming to assess the trade-off between production scale and the construction of a hydrogen and a CO_2 distribution infrastructure. If the scale of centralised hydrogen production is below 40 MW, the trade-off could be favourable for the membrane reactor with small-scale CO_2 capture (18 $/GJ including H_2 storage, dispensing and CO_2 sequestration for 40 MW SMR versus 19 $/GJ for MR). The membrane reactor might become competitive with conventional steam reforming provided that thin membranes can be combined with high stability and a cheap manufacturing method for the membrane tubes. Thin membranes, industrial utility prices and larger production volumes (i.e. technological learning) might reduce the levelised hydrogen cost of the membrane reactor at the refuelling station to less than 14 $/GJ including CO_2 sequestration cost, below that of large-scale H_2 production with CO_2 sequestration (～15 $/GJ).