Syngas Treatment

Treatment of the raw syngas formed during CLG is required to obtain syngas properties compliant with the requirements of the subsequent Fischer-Tropsch synthesis unit. These requirements are an H₂/CO ratio of around 2, the reduction of inert species like CO₂ to minimize unnecessary gas flows, as well as the removal of condensable gases (such as tars) and impurities (i.e. H₂S, COS, HCN, NH₃ < 0.1 ppmv) in order to prevent catalyst deactivation. Moreover, the gas treatment must be reliable since the catalyst requires high stability and activity at the designated operating conditions to achieve high product yields in the preferred range. Taking into account this prerequisite, one major challenge is to minimize the costs for the gas cleaning equipment, which contributes a considerable share to the overall plant costs. While a number of well-established techniques are being considered for the gas treatment train (e.g. water scrubbing for removal of chlorine compounds, biodiesel washing column for tar removal, etc.), acid gas removal and separation is to be achieved via a new technological concept.

This novel process, shown on the right, consists of an amine scrubber/desorber combination, for acid gas removal, coupled with a caustic (NaOH) scrubber and a hydrogen peroxide (H₂O₂) scrubber, for syngas fine cleaning and acid gas separation, respectively. As this concept allows for an operation at moderate temperature levels, as opposed to the state-of-the-art Rectisol® process, which relies on solvent refrigeration, major reductions in CAPEX and OPEX can be achieved through its deployment. These cost-savings facilitate an economic production of biofuels from biogenic residues and therefore are essential for a market break-through of the novel biomass-to-biofuel process chain.

For the experimental investigation of this novel syngas cleaning process, a mobile gas cleaning rig, developed and operated by RWE Power, will be utilized. The functional and constructive aspects of this test rig are discussed in Gas Cleaning Test Rig.