Publication
Bio synthetic natural gas (Bio-SNG) is being proposed as an alternative to the natural gas of fossil origin (NG) [1]. Bio-SNG consists mainly of CH4 (at least 95%mol), has a high heating value (e.g. 10 kWh/m3N), and respects the quality standards of the NG industry [1]. Bio-SNG can be injected in the existing NG distribution grids and used in the current applications of NG, such as gas turbines, heating, transportation, etc. It can be manufactured from dry biomass such as wood and grass via low pressure gasification (0 to 10 barg), which converts the raw material into the raw producer gas. The raw producer gas is cleaned (i.e. removal of impurities), converted into CH4 and finally upgraded into the Bio-SNG (e.g. removal of CO2 and H2O from the product stream). In the gas cleaning step, a hot catalytic reactor operated between 400◦C and 600◦C could be used, named hydrogenolysis reactor. It should promote (i) hydrodesulfurization of organic sulfur compounds (HDS), (ii) hydrogenation (HYD) and/or steam reforming (SteamRef) of hydrocarbons , (iii) sulfur resistant methanation (S-RM) and (iv) sour water-gas-shift (WGS). In this PhD thesis, catalysts were investigated, which could promote the reactions mentioned above under the conditions projected for the hydrogenolysis reactor. Additionally, a detailed characterization of sulfur-containing organic compounds in the raw producer gas was conducted, since it is necessary for the correct design of the gas cleaning step. The gas streams of biomass gasification plants, such as the raw producer gas, can be characterized using a sampling system and analytical equipments. The use of an in-house constructed sampling system based on a liquid quench of the sampled gas was evaluated in detail. It is shown that 70 to 99% of the molar fraction of condensable compounds (e.g. tars) can be captured into the quenching liquid, depending on how the sampling system is operated. For non-condensable compounds (e.g. H2, CO, CO2, etc.), when 1-methoxy-2-propanol is used to quench the sampled gas, 80% to nearly 100% of the molar fractions of the compounds in the sampled gas can be recovered, depending on the compound considered and how the equipment is operated. Moreover, an analysis of the uncertainties related to this sampling technique was conducted. For this purpose, the systematic measurement uncertainties of this sampling technique were determined and compared with the random uncertainties of the concentrations measured. The results showed that for certain compounds (e.g. H2, CO, CH4, and tars) the concentration measurements are reliable. For the detailed speciation of condensable organic sulfur compounds found in the raw producer gas of biomass gasification, the liquid quench sampling system and a gas chromatograph coupled with a sulfur chemiluminescence detector (GC/SCD) were used. Up to 41 different sulfur-containing compounds could be detected. It is considerably more than what is commonly reported in the literature,