Gasification processes deliver a producer gas that is not clean enough for modern applications due to the presence of residual tars. Various filtering, catalytic, and other methods have been tested giving “too complicated and expensive” and/or “not sufficient” results. Although plasma reactors can be used directly for gasification for the production of clean syngas—and ECP has developed its own such plasma gasification system, SynGen—for this application ECP is suggesting a different approach assisted by its GlidArc low-tech plasma:

1. Gasification of any feed into as-dirty-as-possible producer gas. The main target of this step is a separation of ashes, minerals, and metals from all volatile elements and compounds.

2. Total and selective conversion of highly-abundant tars, hydrocarbons, and other carbonaceous molecules into a supplementary amount of very clean synthesis gas using GlidArc-assisted partial oxidation. This step deals with all complex molecules and converts them into hydrogen and carbon monoxide. Any initial H₂ and CO in initial dirty producer gas are not attacked in the process so that more syngas exits the selective GlidArc-assisted Oxidizer.

3. The clean and compressed syngas then flows to the Compact Plate Reactors. In the paper presented at ACS, ECP discussed a reactor tailored for local resources and a low H₂/CO syngas issued from biomass gasification. Continuous runs were performed using a 5.5-L test reactor, the high-temperature iron catalyst and real syngas at H₂/CO = 1.6 to 2.0 ratios.

   High-quality waxes at a high yield were obtained by this process. The sulfur-free wax analysis shows 50% mass occurrence of linear alkanes, 48% of saturated monocyclo-alkanes, and absence of polycyclic substances. Such composition is intriguing, as this type of FT product has never been described, ECP says. The resulting wax should be easily hydrocracked and resulting fuels will be an order of magnitude less toxic than conventional Diesel oil.

The compact reactor features thin catalyst grains filling the relatively narrow (up to 50 mm) and relatively short channels (up to 3 m) of the Reactive plates (R) made of a heat conducting metal. A coolant fluid crosses other neighboring metallic Heat-conducting (H) plates of a similar shape and size. The H plates are strongly tightened to the two sides of every R plate to assure a very good thermal contact between them. Dozens or hundreds of such R and H plates can be assembled in a sandwich structure supporting high-pressure syntheses.

ECP believes that iron-based FT catalysts are advantageously adapted to this plate reactor. Moreover, the Fe-based catalysts accept various syngas mixtures at much wider H₂/CO molar ratios than delicate Cobalt-based catalysts.

The compact size of the reactors (about the size of a refrigerator) would enable lower cost production of synthetic fuels produced by a low-tech gasification of locally available wastes, biomass, or other resources, according to Czernichowski. Corn farming regions, for instance, could use corn stover (leaves and stalks left in the field after harvest) as the raw material. In urban areas, waste cooking oil from restaurants could be the raw material. In regions that produce biodiesel fuel, glycerol could be converted into clean fuels.

Resources

• Albin Czernichowski, Prof. “Plasma-assisted selective partial oxidation of tars and other pollutants in producer gases” (ACS 239 Paper 194)

• Albin Czernichowski, Prof. “Fischer-Tropsch products from compact reactor and high-temperature Iron catalyst” (ACS 239 Paper 91)