This report details the progress on work to develop an alternative technology that can produce ammonia at much lower pressures (~30 bar) by sourcing hydrogen directly from a PEM electrolyser and scale-up the technology to build a prototype capable of producing ammonia with the only inputs being water, air and solar PV.
Report extract
Currently most of the ammonia is globally produced by sourcing hydrogen from Natural Gas (NG) and making this hydrogen react with nitrogen in the presence of a catalyst in a Haber-Bosch reactor at around 450oC and pressures in excess of 150 bar. The major aim of the proposed work is to develop an alternative technology that can produce ammonia at much lower pressures (~30 bar) by sourcing hydrogen directly from a PEM electrolyser and scale-up the technology to build a prototype capable of producing ammonia with the only inputs being water, air and solar PV. In the conventional ammonia synthesis Haber-Bosch reactor hydrogen to ammonia conversion rates of around 15% are achieved in a single pass and with multiple passes, over 90% hydrogen utilisation is achieved. In the previous project in collaboration with Orica, a metal membrane based process was developed to convert hydrogen to ammonia. Hydrogen is driven across a hydrogen permeating membrane (i.e. Pd) by a partial pressure difference, and the permeated hydrogen species react in the presence of a catalyst with nitrogen supplied to the other side of the membrane. The technology was developed to TRL 3, with ammonia synthesis rates of up to 10-6 mol cm-2 s-1 and hydrogen conversion rates of up to 4% at pressures much lower than used in the conventional H-B reactor. The technology was demonstrated in the lab at a small scale by sourcing hydrogen directly from a PEM electrolysis cell.