Emerging Technologies on Syngas Purification: Process Intensification

Syngas normally contains a series of contaminating gases, depending on the raw materials used, the most abundant one usually being H₂S, accompanied by COS and, also, HCl, HF, etc. Normally, purification should be performed before its combustion in the gas turbine (in the case of combined cycle plants) and the classic procedure, as performed at present in some installations, uses the wet process, which demands a reduction in the temperature of the gas to be purified and, therefore, gives rise to a series of thermodynamic losses. The trend is to research high-temperature purification processes that avoid or reduce this loss in performance. In particular, there are two research lines for sulphur compounds: (i) The use of low-value metal adsorbents that may be discarded once they have been stabilised and without contaminating properties, such as calcium compounds that may produce CaO that captures the hydrogen sulphide and (ii) the ‘important value’ adsorbents that therefore require the ability to be regenerated and reused, and whose base are metals with high affinity with sulphur, such as Zn, Fe and Cu but whose cost is much higher than the previously mentioned calcium compounds.