In the present study, an oxygen blown pilot scale pressurized entrained-flow biomass gasification plant (PEBG, 1 MWth) was designed, constructed, and operated. This Article provides a detailed description of the pilot plant and results from gasification experiments with stem wood biomass made from pine and spruce. The focus was to evaluate the performance of the gasifier with respect to syngas quality and mass and energy balance. The gasifier was operated at an elevated pressure of 2 bar(a) and at an oxygen equivalence ratio (λ) between 0.43 and 0.50. The resulting process temperatures in the hot part of the gasifier were in the range of 1100–1300 °C during the experiments. As expected, a higher λ results in a higher process temperature. The syngas concentrations (dry and N2 free) during the experiments were 25–28 mol % for H2, 47–49 mol % for CO, 20–24 mol % for CO2, and 1–2 mol % for CH4. The dry syngas N2 content was varied between 18 and 25 mol % depending on the operating conditions of the gasifier. The syngas H2/CO ratio was 0.54–0.57. The gasifier cold gas efficiency (CGE) was approximately 70% for the experimental campaigns performed in this study. The synthesis gas produced by the PEBG has potential for further upgrading to renewable products, for example, chemicals or biofuels, because the performance of the gasifier is close to that of other relevant gasifiers.

PostprintThis is the accepted version of a paper published in Fuel processing technology. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record):Weiland, F., Nordwaeger, M., Olofsson, I., Wiinikka, H., Nordin, A. (2014) Entrained flow gasification of torrefied wood residues. In this work, four different fuels were gasified in a pressurized entrained flow pilot plant 12 gasifier at approximately 270 kW th . The different fuels were; two torrefied wood 13 residues, one raw wood residue and one torrefied stem wood. The system pressure and 14 oxygen equivalence ratio (!) were held constant for all four gasification experiments. It 15 was found that the torrefaction pretreatment significantly reduced the milling energy 16 consumption for fuel size reduction, which in turn contributed to increased gasification 17 plant efficiency. Furthermore, the results indicate that the carbon conversion efficiency • The torrefaction pretreatment reduced the milling energy consumption. 2• Torrefaction pretreatment contributed to increased gasification plant efficiency. 3• The fuel carbon conversion efficiency was affected by torrefaction pretreatment. 4• The CH 4 yield from gasification was reduced for severely torrefied fuel. 5

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Stem wood powders were fired in a mullite-lined pilot-scale oxygen-blown pressurized entrained-flow gasifier. During repeated campaigns involving increases in fuel load and process temperature, slag formations that eventuated in the blockage of the gasifier outlet were observed. These slags were retrieved for visual and chemical characterization. It was found that the slags had very high contents of Al and, in particular, high Al/Si ratios that suggest likely dissolution of the mullite-based refractory of the gasifier lining due to interactions with the fuel ash. Possible causes for the slag formation and behavior are proposed, and practical implications for the design of future stem wood entrained-flow gasifiers are also discussed.

Pressurized entrained-flow gasification of renewable forest residues has the potential to produce high-quality syngas suitable for the synthesis of transport fuels and chemicals. The ash transformation behavior during gasification is critical to the overall production process and necessitates a level of understanding to implement appropriate control measures. Toward this end, ash deposits were collected from inside the reactor of a pilot-scale O2-blown pressurized entrained-flow gasifier firing stem wood, bark, and pulp mill debarking residue (PMDR) in separate campaigns. These deposits were characterized with environmental scanning electron microscopy equipped with energy-dispersive X-ray spectrometry and X-ray diffractometry. The stem wood deposit contained high levels of calcium and was comparatively insubstantial. The bark and PMDR fuels contained contaminant sand and feldspar particles that were subsequently evident in each respective deposit. The bark deposit consisted of lightly sintered ash aggregates comprising presumably a silicate melt that enveloped particles of quartz and, to a lesser degree, feldspars. Discontinuous layers likely to be composed of alkaline-earth metal silicates were found upon the aggregate peripheries. The PMDR deposit consisted of a continuous slag that contained quartz and feldspar particles dispersed within a silicate melt. Significant levels of alkaline-earth and alkali metals constituted the silicate melts of both the bark and PMDR deposits. Overall, the results suggest that fuel contaminants (i.e., quartz and feldspars) play a significant role in the slag formation process during pressurized entrained-flow gasification of these woody biomasses.

Integration of renewable raw materials in existing refineries is most likely the shortest way for the successful, largescale introduction of biofuels in the transport sector in the short term and medium term. One possible renewable raw material for this application is fast pyrolysis bio-oil (FPBO), which in this study has been coprocessed (at 0 and 20 wt %) with vacuum residue (VR, 50 wt %) and vacuum gas oil (VGO, balance) in a continuous, as well as a semibatch, slurry hydrocracking process. Experiments both with and without FPBO were performed at 450 °C and 150 bar with a continuous hydrogen flow through the reactor. Oil-soluble molybdenum hexacarbonyl and molybdenum 2-ethylhexanoate were used as catalyst precursors, to be sulfided in situ. The continuous trials resulted in reactor walls completely free of coking, and they resulted in a low overall coke yield (about 1 wt %). The hydrodeoxygenation reached almost 92%, and the total acid number was reduced by nearly 99% in the FPBO experiment. A mass balance of the renewable carbon from FPBO, based on the performed experiments, showed that the fossil CO 2 emissions can be lowered by 1.35 kg per kilogram of processed FPBO if all renewable carbon in gaseous and liquid hydrocarbons is used to replace its fossil counterparts, and all methane formed from FPBO is used to produce hydrogen. Semibatch experiments gave less successful results when upgrading FPBO-containing feedstock, with a high coke yield (8 wt %) as well as a high gas yield (24 wt %). The results of this study demonstrate that FPBO can be successfully coprocessed with heavy fossil oils in a continuous slurry hydrocracking process without negatively affecting the processing of the fossil components of the feed and that a continuous process is preferred over batch or semibatch processes when studying coprocessing of bio-oils.

Pressurized entrained-flow gasification (PEFG) of bark and a bark/peat mixture (BPM) was carried out in a pilot-scale reactor (600 kWth, 7 bar­(a)) with the objective of studying ash transformations and behaviors. The bark fuel produced a sintered but nonflowing reactor slag, while the BPM fuel produced a flowing reactor slag. Si was enriched within these slags compared to their original fuel ash compositions, especially in the bark campaign, which indicated extensive ash matter fractionation. Thermodynamically, the Si contents largely accounted for the differences in the predicted solidus/liquidus temperatures and melt formations of the reactor slags. Suspension flow viscosity estimations were in qualitative agreement with observations and highlighted potential difficulties in controlling slag flow. Quench solids from the bark campaign were mainly composed of heterogeneous particles resembling reactor fly ash particles, while those from the BPM campaign were flowing slags with likely chemical interactions with the wall refractory. Quench effluents and raw syngas particles were dominated by elevated levels of K that, along with other chemical aspects, indicated KOH­(g) and/or K­(g) were likely formed during PEFG. Overall, the results provide information toward development of woody biomass PEFG and indicate that detailed understanding of the ash matter fractionation behavior is essential.