1. |
- Kopyscinski, J., et al.
(författare)
-
Synthetic natural gas from wood: Reactions of ethylene in fluidised bed methanation
- 2013
-
Ingår i: Applied Catalysis A: General. - : Elsevier BV. - 1873-3875 .- 0926-860X. ; 462-463, s. 150-156
-
Tidskriftsartikel (refereegranskat)abstract
- The synthesis step in the production of synthetic natural gas from wood, i.e. the methanation, was investigated by systematic experiments with commercial nickel catalyst in a micro-fluidised bed reactor. Ethylene in the feed is always converted completely; dominantly serial reactions of ethylene to ethane and further to methane under isothermal fluidised bed methanation conditions could be shown. Lower temperatures favour the production of the intermediate ethane while high temperatures cause the formation of carbon depositions and carbon whiskers. Applying optimal operation conditions, the hydrogenation of the unsaturated olefin not only avoids the deposition of carbon or coke, but also leads to an increase of the higher heating value (HHV) of the produced (raw) SNG. © 2013 Elsevier B.V. All rights reserved.
|
|
2. |
- König, C.F.J., et al.
(författare)
-
Mechanistic studies of chemical looping desulfurization of Mn-based oxides using in situ X-ray absorption spectroscopy
- 2014
-
Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 113, s. 1895-1901
-
Tidskriftsartikel (refereegranskat)abstract
- Cleaning of producer gas from biomass gasification is required for further processing, e.g. to avoid catalyst poisoning in subsequent conversion steps. High-temperature gas cleaning, of which sulfur removal is an important part, is a promising way to improve the overall efficiency of biomass conversion. In a high temperature "chemical looping desulfurization" process, a sorbent material, here manganese oxide, is cycled between producer gas from the gasifier to remove sulfur species, and an oxidizing atmosphere, in which the sulfur species are released as SO2. Alternatively, the use of such material as reactive bed material could be integrated into an allothermal dual fluidized bed gasifier. In a laboratory reactor, we subjected manganese-based materials to a periodically changing gas atmosphere, simulating a "chemical looping desulfurization" reactor. The "fuel reactor" gas contained H2, CO, CH4 and H2S, similar as in the producer gas, and the "oxidizing reactor" contained diluted O2. Mass spectrometry showed that most of the H2S is taken up by the sample in the "fuel reactor" part, while also some unwanted SO2 is generated in the "fuel reactor" part. Most of the sulfur is released in the oxidizing reactor. Simultaneous in situ X-ray absorption spectroscopy (XAS) of the Mn materials during different stages of the chemical looping desulfurization process showed that the initial Mn3O4 is transformed in the presence of H2S to MnS via a MnO intermediate in the fuel reactor. Oxygen from the reduction of Mn3O4 oxidizes some H2S to the undesired SO2 in the fuel reactor. Upon exposure to O2, MnS is again oxidized to Mn3O4 via MnO, releasing SO2. The presence of CO and/or CH4 in the fuel reactor has no effect on this mechanism. Measuring the structure-performance relationship of gas cleaning materials with in situ methods will enable knowledge-based materials development for improved performance. © 2013 Elsevier Ltd. All rights reserved.
|
|