High-purity H2 production with CO2 capture based on coal gasification

Abstract

A novel hybrid concept is proposed, combining Pd-alloy membrane and low temperature separation technology, to produce pure H2 from gasified coal and capture the main part of the generated CO2. 75% of the H2 produced from gasification and water-gas shift is separated from the shifted syngas through H2-selective Pd-alloy membranes. After water removal, the H2-depleted, CO2-rich retentate stream is compressed and cooled, after which CO2 is condensed out at a purity level of ∼99%. The “waste” volatiles from the low-temperature CO2 separation constitute a low heating value syngas that is burnt in a gas turbine. The gas turbine with a steam bottoming cycle generates a surplus of electricity that could be employed for H2 liquefaction. Altogether, the concept has the potential to be developed into a stand-alone high-purity H2 production unit with CO2 capture, suitable e.g. for remote areas from where H2 and possibly also CO2 must be transported by ship. However, the investigations of three different process alternatives, as well as three membrane separator parameters, illustrate that there are many degrees of freedom in the proposed concept that require further analysis, both individually and how they interact, in order to establish an optimized and purposeful stand-alone H2 production concept.