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  • 1.
    Borén, Eleonora
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kajsa, Werner
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Defining the temperature regime of gaseous degradation products of Norway spruce2013In: 21nd European Biomass Conference and Exhibition, Copenhagen, June, 2013, ETA Florens Renewable Energies, 2013, 2013Conference paper (Other academic)
  • 2.
    Borén, Eleonora
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Rudolfsson, Magnus
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Larsson, Sylvia H.
    Off-gassing from 16 pilot-scale produced pellets assortments of torrefied pine: impact of torrefaction severity, storage time, pelletization parameters, and pellet qualityManuscript (preprint) (Other academic)
    Abstract [en]

    Off-gassing from wood pellets poses risks in large scale handling chains - yet little is known on off-gassing from pellets of torrefied wood. This study reports CO, CO2, and O2 concentrations in off-gases during storage of 16 torrefied and two untreated pellets assortments. According to an experimental design, pellets were produced in pilot scale from pine chips torrefied at five different set points. Off-gassing was assessed in relation to storage conditions, torrefaction and pelletization parameters, and pellet quality. Pellets from the most severely torrefied pine formed CO, CO2, and consumed O2 similarly to untreated pellets. Off-gassing was positively correlated to pellet moisture content; however, the most severely torrefied also retained the least moisture. Open air storage (20–270 days) of torrefied chips prior to pelletization did not affect off-gassing levels. Results are important for safe handling; torrefied pellets can cause comparable levels as untreated pellets of CO, CO2, and O2.

  • 3.
    Borén, Eleonora
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Rudolfsson, Magnus
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Larsson, Sylvia H.
    Off-gassing from pilot-scale torrefied pine wood chips: – impact of torrefaction severity, cooling technology, and storage timeManuscript (preprint) (Other academic)
    Abstract [en]

    During handling and storage of conventional wood-based energy carriers, O2 depletion as well as CO and CO2 off-gassing can reach hazardous levels, and certain irritating VOCs trespass exposure levels. When new thermally pre-treated biomass commodities are entering consumer markets, knowledge on these assortments’ off-gassing behaviour is needed. In this study, relative concentrations of VOCs, CO, CO2, and O2 in off-gases of five different pilot-scale torrefied pine wood chip assortments was monitored over 12 days. VOC composition shifted with increased torrefaction treatment; terpene concentrations decreased while furan and lignin derivates increased. Generally, VOC amounts decreased with storage time, but for the least severely torrefied chips (291°C, 6 min), certain VOCs increased; e.g. hexanal, acetone, and 2-pentylfuran. Torrefied chips was subject to two different cooling technologies: i) heat exchanging and ii) additional water spraying. Water spraying resulted in higher VOC concentrations, stronger O2 depletion, and higher CO2 by a factor four. 

  • 4.
    Brostrom, Markus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Branca, C.
    Di Blasi, C.
    Influence of torrefaction on the devolatilization and oxidation kinetics of wood2012In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 96, p. 100-109Article in journal (Refereed)
    Abstract [en]

    Devolatilization and oxidation kinetics of torrefied wood have been studied by evaluating thermogravimetric curves measured in nitrogen and air at various heating rates. Samples consist of Norway spruce wood chips torrefied at several process temperatures and residence times. Data about untreated wood have also been obtained for comparison. Measured curves are well predicted by means of a five-reaction mechanism, consisting of three devolatilization reactions for the pseudo-components hemicellulose. cellulose and lignin and, in air, of two additional reactions for char devolatilization and combustion. The torrefaction pre-treatment only requires model modifications in the amounts of volatiles generated from the decomposition of pseudo-components, indicating that only their relative percentages and not their reactivities are modified. On the other hand, a slightly different thermal stability is found for the char generated from torrefied wood, which results in higher activation energy and lower reaction order for the oxidation step. Hence torrefaction conditions can affect the subsequent conversion characteristics of the char product. (C) 2012 Elsevier B.V. All rights reserved.

  • 5.
    Fick, Jerker
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nilsson, Calle
    Unit for Biomass Technology and Chemistry, Swedish University of Agricultural Sciences, Umeå.
    A study of the gas-phase ozonolysis of terpenes: the impact of radicals formed during the reaction2002In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 36, no 20, p. 3299-3308Article in journal (Refereed)
    Abstract [en]

    The gas-phase ozonolysis of α-pinene, Δ3-carene and limonene was investigated at ppb levels and the impact of the ozone, relative air humidity (RH), and time was studied using experimental design. The amounts of terpene reacted varied in the different settings and were as high as 8.1% for α-pinene, 10.9% forΔ3-carene and 23.4% for limonene. The designs were able to describe almost all the variation in the experimental data and were also successful in predicting omitted values. The results described the effects of time and ozone and also showed that RH did not have a statistically significant effect on the ozonolysis. The results also showed that all three terpenes were affected by an additional oxidation of OH radicals and/or other reactive species. The results from the designs states that this additional oxidation was responsible for 40% of the total amount of α-pinene reacted, 33% of the total amount of Δ3-carene reacted and 41% of the total amount of limonene reacted at the settings 20 ppb terpene, 75 ppb ozone, 20% RH and a reaction time of 213 s. Additional experiments with 2-butanol as OH radical scavenger showed that the reaction with OH radicals was responsible for 37% of the total α-pinene reacted and 39% of the total Δ3-carene reacted at the same settings. The scavenger experiments also showed that there were no significant amounts of OH radicals formed during the ozonolysis of limonene. The results from the designs were also compared to a mathematical model in order to evaluate further the data.

  • 6.
    Fick, Jerker
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Chemistry.
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Chemistry.
    Nilsson, Calle
    Ozone Removal in the Sampling of Parts per Billion Levels of Terpenoid Compounds: An Evaluation of Different Scrubber Materials2001In: Environmental Science & Technology, Vol. 35, no 7, p. 1458-62Article in journal (Refereed)
    Abstract [en]

    Some reactive volatile organic compounds (VOCs) are prone to degradation during sampling in an ozone-rich environment. A wide variety of different chemicals have been used to remove the ozone prior to sampling, but the possibility of interference by such chemicals with the sampled VOCs has not been thoroughly examined. In the present investigation, the retention/degradation of four terpenes (-pinene, -pinene, 3-carene, and limonene) and isoprene together with some of their oxidation products (-pinene oxide, nopinone, 4-acetyl-1-methylcyclohexene (AMCH), methylglyoxal, and methacrolein) has been studied, using various ozone-removing chemicals in an attempt to evaluate their potential as ozone scrubbers in the sampling of ambient air. The chemicals included in this first screening and their ozone-removing capacity are as follows: KI, MnO2, and Na2SO3 removed ozone for more than 24 h when exposed to 73-78 ppb (150-160 g/m3) at a sampling flow rate of 500 mL/min. Silanized poly(1,4-phenylene sulfide) (PFS) removed ozone for 5 h, unsilanized PFS removed ozone for 1 h and 50 min, and Na2S2O3 removed ozone for 20 min. The recovery of the selected compounds with the different scrubbers was >95% for all compounds for KI; >95% for the terpenes oxidation products; >90% for the terpenes and isoprene for PFS; >90% for the terpenes and isoprene for MnO2 on copper nets, Na2SO3, and Na2S2O3; and <90% for the terpenes and isoprene for carulite (a commercial mixture between MnO2, CuO, and Al2O3), CuO, and indigo carmine.

  • 7.
    Fick, Jerker
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Chemistry.
    Nilsson, Calle
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Chemistry.
    Effect of OH radicals, relative humidity, and time on the composition of the products formed in the ozonolysis of α-pinene2003In: Atmospheric Environment, Vol. 37, no 29, p. 4087-96Article in journal (Refereed)
    Abstract [en]

    The gas-phase ozonolysis of α-pinene at ppb levels were studied and the effects of OH radicals formed in the reaction, the relative humidity (RH), and time on the products formed were investigated. Identified products were pinic acid, glyoxal, methyl glyoxal, norpinonic acid and a norpinonic acid isomer, pinonic acid, a C4 dicarbonyl, a C5 dicarbonyl, norpinon aldehyde, and pinon aldehyde. The different parameters effect on the formation of these products were evaluated using experimental design and multivariate modeling. Pinonic acid, norpinonic acid and its isomer, were not detected in the absence of OH radicals. The amounts of pinic acid, norpinon aldehyde, and pinon aldehyde all decreased in the absence of OH radicals. Glyoxal and methyl glyoxal were not affected.

    The formation of pinonic acid decreased when the RH was increased. The formation of pinic acid, glyoxal, methyl glyoxal, and pinon aldehyde increased with increasing RH, while norpinon aldehyde was not affected. The implications of these observations and additional interaction effects are discussed, and a novel route of the formation of pinic acid is presented.

  • 8.
    Fick, Jerker
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Pommer, Linda
    Åstrand, Anders
    Östin, Ronny
    Nilsson, Calle
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Chemistry.
    Ozonolysis of monoterpenes in mechanical ventilation systems2005In: ATMOSPHERIC ENVIRONMENT, Vol. 39, no 34, p. 6315-25Article in journal (Refereed)
    Abstract [en]

    In this investigation the ozonolysis of of three monoterpenes (alpha-pinene, Delta(3)-carene and limonene) was studied was studied in authentic mechanical ventilation systems, that included either a cross flow or a rotary heat exchanger. The effects of varying three experimental parameters were investigated: the level of ozone (25 and 75 ppb), the reaction time (25 and 75s), and the surface area in the ventilation duct (14.8 and 29.5 m(2)). The initial concentration of each of the monoterpenes was 20 ppb in every experiment, and 1-16% of the alpha-pinene, < 0.5-13% of the Delta(3)-carene, and < 0.5-16% of the limonene reacted. The effects of humidity (g m(-3)) and temperature of the outdoor and supply air, and water losses in the ventilation duct, were also evaluated. Experiments were based on a chemometric statistical design. Comparison of the results to theoretically calculated values showed that theoretical calculations underestimated the amounts that reacted in the ventilation systems by factors of 2-13, depending on the monoterpene and experimental settings.

  • 9.
    Fick, Jerker
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Åstrand, Anders
    Östin, Ronny
    Nilsson, Calle
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The effect of mechanical ventilation systems on the chemistry in the supply airArticle in journal (Refereed)
  • 10.
    Gao, Qiuju
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Jansson, Stina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Evaluation of solvent for pressurized liquid extraction of PCDD, PCDF, PCN, PCBz, PCPh and PAH in torrefied woody biomass2015In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 154, p. 52-58Article in journal (Refereed)
    Abstract [en]

    Biomass torrefaction for sustainable energy production has gained an increasing interest. However, there is a lack of information on the thermal formation of persistent organic pollutants such as dioxins in the torrefied solid product. In this paper, we investigated the applicability of pressurized liquid extraction (PLE) for simultaneous extraction of a number of polychlorinated planar aromatic compounds from torrefied wood. The targeted compounds included polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), naphthalenes (PCNs), benzenes (PCBz), phenols (PCPhs) and PAHs. PLE tests were conducted on torrefied and non-torrefied (i.e. raw) eucalyptus wood chips using 5 single solvents (n-hexane, toluene, dichloromethane, acetone and methanol) and a mixture of n-hexane/toluene (1:1, v/v). The performance of each solvent was evaluated in terms of recoveries of spiked internal standards and the amount of co-extracted sample matrix. High polarity solvents such as methanol and acetone resulted in poor recoveries from torrefied wood for most of the target compounds, probably due to the high co-extraction of thermally degraded lignocellulosic compounds. Raw wood was less solvent-dependent and comparable results were obtained for polar and non-polar solvents. Toluene showed the best performance of the investigated solvents, with average recoveries of 79 +/- 14% and 66 +/- 9% for raw and torrefied wood, respectively. The method was validated using pentachlorophenol-tainted spruce wood chips. The proposed PLE method was compared to the traditional Soxhlet method. Results show that PLE gave equivalent or better extraction for all target compounds.

  • 11.
    Khwaja, Salik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Weiland, Fredrik
    Pettersson, Esbjorn
    Wiinikka, Henrik
    Wingren, Anders
    Strandberg, Martin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Padban, Nader
    Hinderson, Anna
    Khodayari, Raziyeh
    Carbo, Michiel
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Entrained Flow Gasification of Torrefied Lignocellulosic Biomass2016In: Papers of the 24TH European Biomass Conference: Setting the Course for a Biobased Economy / [ed] Faaij, APC Baxter, D Grassi, A Helm, P, Amsterdam: ETA Florence Renewable Energies , 2016, p. 1138-1142Conference paper (Refereed)
    Abstract [en]

    An extensive evaluation program was carried out within the European SECTOR project to evaluate the feasibility of torrefied and densified biomass in available entrained flow gasifiers. Different entrained flow reactors (both atmospheric and pressurized) in different scales, from lab scale to a 240 MW industrial gasifier were used for evaluation of torrefied materials as feedstock. Total behaviours of the new fuel throughout the whole supply chains and the EFG systems were evaluated and documented, including process behaviours in terms of operation, gas quality, products of incomplete gasification, etc. Results showed a significant improvement in fuel properties in terms of storage, logistics, milling and feeding behaviour by torrefaction and densification. Entrained flow gasification of the torrefied biomass was also shown to be feasible without any major showstoppers, even improving the gasification processes. Production of tars and other products of incomplete gasification were often found significantly reduced during gasification of torrefied material.

  • 12.
    Lestander, Torbjörn A.
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Rudolfsson, Magnus
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    NIR provides excellent predictions of properties of biocoal from torrefaction and pyrolysis of biomass2014In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 16, no 12, p. 4906-4913Article in journal (Refereed)
    Abstract [en]

    When biomass is exposed to high temperatures in torrefaction, pyrolysis or gasification treatments, the enrichment of carbon in the remaining 'green coal' is correlated with the temperature. Various other properties, currently measured using wet chemical methods, which affect the materials' quality as a fuel, also change. The presented study investigated the possibility of using NIR spectrometry to estimate diverse variables of biomass originating from two sources (above-ground parts of reed canary grass and Norway spruce wood) carbonised at temperatures ranging from 240 to 850 C-circle. The results show that the spectra can provide excellent predictions of its energy, carbon, oxygen, hydrogen, ash, volatile matter and fixed carbon contents. Hence NIR spectrometry combined with multivariate calibration modeling has potential utility as a standardized method for rapidly characterising thermo-treated biomass, thus reducing requirements for more costly, laborious wet chemical analyses and consumables.

  • 13.
    Nordin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordwaeger, Martin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Biomass conversion through torrefaction2012In: Technologies for converting biomass to useful energy: combustion, gasification, pyrolysis, torrefaction and fermentation / [ed] Erik Dahlquist, CRC Press, 2012, p. 217-244Chapter in book (Refereed)
  • 14.
    Normark, Monica
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gräsvik, John
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gorzsas, Andras
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Winestrand, Sandra
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jönsson, Leif J.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Biochemical Conversion of Torrefied Norway Spruce After Pretreatment with Acid or Ionic Liquid2016In: Bioenergy Research, ISSN 1939-1234, E-ISSN 1939-1242, Vol. 9, no 1, p. 355-368Article in journal (Refereed)
    Abstract [en]

    The chemical effects of torrefaction and the possibility to combine torrefaction with biochemical conversion were explored in experiments with five preparations of wood of Norway spruce that had been torrefied using different degrees of severity. Compositional analysis and analyses using solid-state CP/MAS C-13 NMR, Fourier-transform infrared (FTIR) spectroscopy, and Py-GC/MS showed small gradual changes, such as decreased hemicellulosic content and increased Klason lignin value, for torrefaction conditions in the range from 260 A degrees C and 8 min up to 310 A degrees C and 8 min. The most severe torrefaction conditions (310 A degrees C, 25 min) resulted in substantial loss of glucan and further increase of the Klason lignin value, which was attributed to conversion of carbohydrate to pseudo-lignin. Even mild torrefaction conditions led to decreased susceptibility to enzymatic hydrolysis of cellulose, a state which was not changed by pretreatment with sulfuric acid. Pretreatment with the ionic liquid (IL) 1-butyl-3-methylimidazolium acetate overcame the additional recalcitrance caused by torrefaction, and the glucose yields after 72 h of enzymatic hydrolysis of wood torrefied at 260 A degrees C for 8 min and at 285 A degrees C for 16.5 min were as high as that of IL-pretreated non-torrefied spruce wood. Compared to IL-pretreated non-torrefied reference wood, the glucose production rates after 2 h of enzymatic hydrolysis of IL-pretreated wood torrefied at 260 A degrees C for 8 min and at 285 A degrees C for 16.5 min were 63 and 40 % higher, respectively. The findings offer increased understanding of the effects of torrefaction and indicate that mild torrefaction is compatible with biochemical conversion after pretreatment with alternative solvents that disrupt pseudo-lignin-containing lignocellulose.

  • 15. Olofsson, Ingemar
    et al.
    Strandberg, Martin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Oxygen enhanced torrefaction - An initial feasibility studyManuscript (preprint) (Other academic)
    Abstract [en]

    Upcoming world market prices on thermally treated and densified biomass to be feasible for coal replacement put a high demand on the process suppliers to deliver cost efficient and high energy yield conversion systems with a capacity to produce a high quality product. One of the more complex and vital parts in a torrefaction facility is the indirect or direct heat transfer system applied. This is a critical task that also may limit the scale-up potential and thus influence the economy of scale of a complete torrefaction system.

    In the present study, it was demonstrated that the torrefaction reactions in a rotary drum pilot reactor (20 kgDS/h) potentially may be operated autothermally by a low level injection of air directly into the reactor for controlled in-situ partial combustion of the released torrefaction gases. Both concurrent and countercurrent gas flow patterns were evaluated for different process temperatures. At higher temperatures (338°C) in countercurrent gas flow mode, steady-state torrefaction was reached without external heat supply. The resulting torrefied biomass had higher heating value, higher carbon content and lower milling energy consumption, compared to non-oxidative torrefied biomass with same mass yield. Condensation of torrefaction gas compounds is a suggested reason.No significant decrease in the combustibility of the torrefaction gas was experienced.  The demonstrated Oxygen Enhanced Torrefaction (OET) mode thus has the potential to improve the torrefaction systems in terms of scale-up performance with reduced investment and operational costs but further validation work is needed to confirm the present findings and also to identify working conditions.

  • 16.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Oxidation of terpenes in indoor environments: A study of influencing factors2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis the oxidation of monoterpenes by O3 and NO2 and factors that influenced the oxidation were studied. In the environment both ozone (O3) and nitrogen dioxide (NO2) are present as oxidising gases, which causes sampling artefacts when using Tenax TA as an adsorbent to sample organic compounds in the air. A scrubber was developed to remove O3 and NO2 prior to the sampling tube, and artefacts during sampling were minimised when using the scrubber. The main organic compounds sampled in this thesis were two monoterpenes, alfa-pinene and delta-3-carene, due to their presence in both indoor and outdoor air. The recovery of the monoterpenes through the scrubber varied between 75-97% at relative humidities of 15-75%.

    The reactions of alfa-pinene and delta-3-carene with O 3, NO2 and nitric oxide (NO) at different relative humidities (RHs) and reaction times were studied in a dark reaction chamber. The experiments were planned and performed according to an experimental design were the factors influencing the reaction (O3, NO2, NO, RH and reaction times) were varied between high and low levels. In the experiments up to 13% of the monoterpenes reacted when O3, NO2, and reaction time were at high levels, and NO, and RH were at low levels. In the evaluation eight and seven factors (including both single and interaction factors) were found to influence the amount of alfa-pinene and delta-3-carene reacted, respectively. The three most influencing factors for both of the monoterpenes were the O 3 level, the reaction time, and the RH. Increased O3 level and reaction time increased the amount of monoterpene reacted, and increased RH decreased the amount reacted.

    A theoretical model of the reactions occurring in the reaction chamber was created. The amount of monoterpene reacted at different initial settings of O3, NO2, and NO were calculated, as well as the influence of different reaction pathways, and the concentrations of O3 and NO2, and NO at specific reaction times. The results of the theoretical model were that the reactivity of the gas mixture towards alfa-pinene and delta-3-carene was underestimated. But, the calculated concentrations of O3, NO2, and NO in the theoretical model were found to correspond to a high degree with experimental results performed under similar conditions. The possible associations between organic compounds in indoor air, building variables and the presence of sick building syndrome were studied using principal component analysis. The most complex model was able to separate 71% of the “sick” buildings from the “healthy” buildings. The most important variables that separated the “sick” buildings from the “healthy” buildings were a more frequent occurrence or a higher concentration of compounds with shorter retention times in the “sick” buildings.

    The outcome of this thesis could be summarised as follows;

    -

    -

    -

    -

  • 17.
    Pommer, Linda
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nilsson, Calle
    Development of a NO2 scrubber for accurate sampling of ambient levels of terpenes2002In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 36, no 9, p. 1443-1452Article in journal (Refereed)
    Abstract [en]

    The result of pumping air containing 56 ppb NO2 through a terpene-spiked adsorbent (90–130 ng, 90–100 ml min−1), Tenax TA, for 20 min (1.8–2.0 l) was that 8% of α-pinene, 7% of β-pinene, 21% of Δ3-carene and 5% of limonene were oxidised. In similar experiments with air containing 56 ppb O3, 3% of α-pinene, 4% of β-pinene, 10% of Δ3-carene and 38% of limonene were oxidised. Sampling a mixture of a terpene and NO2 using Tenax TA can give unwanted overestimation of the amount of reaction products from the terpene–NO2 reaction or underestimation of the original terpene levels. A scrubber was needed to reduce the problems caused by interfering reactions on the adsorbent of NO2 and to reduce discrimination of reactive compounds due to their relatively fast decay on the adsorbent. Several chemicals have been tested for their ability of removing NO2 and our objective was to develop a well functioning, reusable, easy to handle, easy manufactured NO2 scrubber. The result of the experiments was a scrubber consisting of two glass fibre filters coated with Na2SO3 assembled in a dust collector. The recovery of the terpenes through the scrubber varied between 75% and 97% at 15–75% relative humidity, and the scrubber is a one-use scrubber due to memory effects. The Na2SO3 scrubber could be stored in room air for at least one month without loosing the capacity of removing NO2.

  • 18.
    Pommer, Linda
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Nilsson, Calle
    The influence of O3, relative humidity, NO and NO2 on the oxidation of α-pinene and Δ3-carene2004In: Journal of Atmospheric Chemistry, ISSN 0167-7764, E-ISSN 1573-0662, Vol. 48, no 2, p. 173-189Article in journal (Refereed)
    Abstract [en]

    Upto 13% of α-pinene and δ3-carene had reacted after 213 s in this dark experimental set-up, where O3, NO and NO2 were mixed with terpenes at different relative humidities (RHs). The different experiments were planned according to an experimental design, where O3, NO2, NO, RH and reaction time were varied between high and low settings (25 and 75 ppb, 15 and 42%, 44 and 213 s). An increased amount of α-pinene and δ3-carene reacted in the chamber was observed, when the level of O3, NO and reaction time was increased and RH was decreased. In the study, it was found that different interactions affected the amount of terpene reacted as well. These interactions were between O3 and NO, O3 and reaction time, NO and RH, and between NO and reaction time.

  • 19.
    Pommer, Linda
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nilsson, Calle
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    An experimental comparison of a kinetic model for the reaction of α-pinene and Δ3-carene with ozone and nitrogen oxides2004In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 14, no S8, p. 75-83Article in journal (Refereed)
    Abstract [en]

    A kinetic model was compiled to simulate reactions of the monoterpenes, α-pinene and Δ3-carene, with O3, NO2 and NO. The influence of different initial settings of O3, NO2 and NO on the monoterpene reaction was evaluated. At initial levels of 75 p.p.b. of O3, NO2 and NO each, 1.5% of α-pinene and 1.1% of Δ3-carene were calculated to react after 215 s. The corresponding experimental results showed that 9.3–12.2% of α-pinene and 9.9–11.7% of Δ3-carene reacted. The calculated levels of O3, NO2 and NO were compared to experimental measurements and were shown to correspond well. However, comparison of the amount of monoterpene reacted between calculated and experimental results, demonstrated that the calculations underestimated the amount of monoterpene reacted in the experimental chamber. The difference between experimental and calculated results could, e.g., be the effect of surfaces and the presence of water, which are parameters not included in the kinetic model known to have influence on these reactions.

  • 20.
    Pommer, Linda
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sundell, J
    Nilsson, C
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stenberg, Berndt
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Dermatology and Venerology.
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Class separation of buildings with high and low prevalence of SBS by principal component analysis2004In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 14, no 1, p. 16-23Article in journal (Refereed)
    Abstract [en]

    In this study, we were able to separate buildings with high and low prevalence of sick building syndrome (SBS) using principal component analysis. The prevalence of SBS was defined by the presence of at least one typical skin, mucosal and general (headache and fatigue) symptom. Data from the Swedish Office Illness Study describing the presence and level of chemical compounds in outdoor, supply, and room air, respectively, were evaluated together with information about the buildings in six models. When all data were included the most complex model was able to separate 71% of the high prevalence buildings from the low prevalence buildings. The most important variable that separates the high prevalence buildings from the low prevalence buildings was a more frequent occurrence or a higher concentration of compounds with shorter retention time in the high prevalence buildings. Elevated relative humidity in supply and room air and higher levels of total volatile organic compounds in outdoor and supply air were more common in high prevalence buildings. Ten building variables also contributed to the separation of the two classes of low and high prevalence buildings.

  • 21.
    Pommer, Linda
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Burvall, Jan
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Olofsson, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Mechanisms behind the positive effects on bed agglomeration and deposit formation combusting forest residue with peat additives in fluidized beds2009In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 23, no 9, p. 4245-4253Article in journal (Refereed)
    Abstract [en]

    A compilation was made of the composition of peat from different areas in Sweden, or which a selected But was characterized anal co-combusted with forest residue ill controlled fludized-bed agglomeration tests with extensive particle sampling, The variation in ash-forming elements in the different peat samples was large; thus, eight peat samples were selected from the compilation to represent the variation in peat composition in Sweden. These samples were characterized in terms of botanical composition, analyzed for ash-forming elements, and oxidized using a low-temperature ashing procedure, followed by characterization using scanning electron microscopy/electron-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD). The selected peat samples had in common the presence of Et small fraction of crystalline phases, such as quartz, microcline, albite, and calcium sulfate. The controlled fluidized-bed agglomeration tests that co-combusted forest residue with peat resulted ill a significant increase it) agglomeration temperatures compared to combusting forest residue alone. Plausible explanations for this were in increase of calcium, iron, Or aluminum in the bed particle layers and/or the reaction of potassium with clay minerals, which prevented the formation of low molting bed particle layers, The effects oil particle and deposit formation during co-combustion were reduced amounts of rule particles and all increased number of coarse particles, The mechanisms for the positive effects were a transfer and/or removal of potassium ill the gas phase to it loss reactive particular form via sorption and/or it reaction with the reactive peat ash (SiO2 and CaO), which in most cases formed larger particles (> 1 mu m) containing calcium silicon and Potassium.

  • 22.
    Pommer, Linda
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Bed agglomeration characteristics and mechanisms during gasification and combustion of biomass fuels2005In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 19, no 4, p. 1742-1748Article in journal (Refereed)
  • 23. Rudolfsson, Magnus
    et al.
    Borén, Eleonora
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lestander, Torbjörn A.
    Combined effects of torrefaction and pelletization parameters on the quality of pellets produced from torrefied biomass2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 191, p. 414-424Article in journal (Refereed)
    Abstract [en]

    A combined torrefaction and pelletization study was performed at industrially relevant settings using a factorial design. First, wood chips of Scots pine were torrefied at high temperatures (291-315 degrees C) and short residence times (6-12 min), facilitating high throughput in a continuous pilot-scale torrefaction process. Then the torrefied materials were pelletized, also in pilot-scale, using varying moisture contents (MCs) (10-14%), sieve sizes (4-6 mm), and press channel lengths (PCLs) (25 and 30 mm), in all 19 batches, each of 400 kg. The resulting so called black pellets exhibited bulk densities of 558-725 kg m(-3), durabilities of 46.3-86.5%, and fines contents of 3.8-85.8%. Through multiple linear regression modelling of all 11 responses, it was found that the parameter with the greatest influence on the responses was the torrefaction temperature, followed by torrefaction time, MC, and PCL. Longer PCL and higher MC resulted in higher pellet quality, with less fines and greater bulk density and durability. Furthermore, a low torrefaction degree decreased the amount of power required for pelletization. The energy required to grind pellets into a powder (<0.5 mm) decreased with increasing torrefaction degree as expected, but also with decreasing MC before pelletizing. Pyrolysis-GC/MS analysis of thermal degradation products from the pellets revealed correlations with the torrefaction temperature and time, but no correlations with the pelletization process. These results are useful for mapping chemical changes in torrefied materials and identifying complementary torrefaction and pelletization settings. Specifically of interest is adjustment of PCLs at low intervals to better match friction properties of torrefied materials.

  • 24.
    Strandberg, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Ingemar
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Evaluation of existing and new approaches to determine degree of torrefactionManuscript (preprint) (Other academic)
    Abstract [en]

    Torrefaction is a promising thermal pretreatment method for biomass in which many material properties are enhanced. The biomass components (hemicellulose, cellulose and lignin) degrade in this thermal process to different extents depending on type of process, treatment temperature, residence time and biomass type. Torrefaction severity is usually defined by biomass weight loss or mass yield, but other approaches to determine degree of torrefaction have also been suggested. For continuous and large scale facilities, mass yield can be challenging to determine and another approach to determine torrefaction severity is therefore desired. In this study, one existing and two new approaches for determining degree of torrefaction are presented, compared and evaluated including uncertainty analysis. The three approaches were based on analysis of; volatile matter, thermochemical properties (enthalpy of formation), and higher heating value. 

    All three methods were highly correlated to mass yield and independent of torrefaction process. The degree of torrefaction based on higher heating value predicted mass yield most accurate, had lowest measurement uncertainty and the results were independent of biomass type. In the evaluation of the method based on formation enthalpy it was revealed that the increase in heating values for torrefied biomasses could be explained by the combination of increase in enthalpy of formation and decrease in oxygen content.

  • 25.
    Strandberg, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wiklund-Lindström, Susanne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Åberg, Katarina
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effects of temperature and residence time on continuous torrefaction of spruce wood2015In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 134, p. 387-398Article in journal (Refereed)
    Abstract [en]

    As a solid energy carrier, biomass generally has a few disadvantages, which limits its use for coal replacement and as a feedstock for entrained flow gasification. The hydrophilic and fibrous nature, the low calorific value and low bulk energy content imply high accumulated costs in the whole supply chain and severe challenges in more advanced conversion systems. By thermally pretreating the biomass by torrefaction, these properties may be significantly improved. A continuous torrefaction rotary drum reactor was designed, constructed and evaluated to enable an accurate process control and allow a homogeneous well-defined high quality product to be produced. The combined effects of torrefaction temperature (260–310 °C) and residence time (8–25 min) on a large number of product properties (&gt; 25) were determined for Norway spruce. The resulting mass and energy yields were 46–97% and 62–99%, respectively. Exothermic reactions were evident both at low (260 °C) and high temperatures (310 °C) but with no thermal runaway observed. Increased torrefaction severity resulted in decreased milling energy consumption, angle of repose, mass and energy yield, content of volatile matter, hydrogen, cellulose and hemicellulose. Hydrophobicity, heating value, carbon and fixed carbon contents increased. For all responses, the effect of torrefaction temperature was larger than the effect of residence time. Substantial interaction effects were present for mass and energy yields, volatile matter and hydrogen content. Another correlation found was the relationship of hemicellulose degradation and the brittleness of the torrefied product. Data also suggest secondary char forming reactions during the torrefaction process, resulting in higher fixed carbon content in the torrefied material than expected. The results also suggest torrefaction temperature and residence time not to be totally interchangeable.

  • 26.
    Strandberg, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wiklund-Lindström, Susanne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Swedish Defence Research Agency, FOI.
    Åberg, Katarina
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effects of temperature and residence time on torrefaction of spruce woodManuscript (preprint) (Other academic)
  • 27.
    Taube, Fabian
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Larsson, Tom
    Umeå University, Faculty of Science and Technology, Chemistry.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Chemistry.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Soil Remediation – Mercury Speciation in Soil and Vapor Phase During Thermal Treatment2008In: Water, Air, & Soil Pollution, Vol. 193, no 1-4, p. 155-63Article in journal (Refereed)
    Abstract [en]

    Spectroscopic (XRD, XPS, ICP-MS and AAS) and microscopic (ESEM) techniques have been used in order to study the chemical effects with emphasis on mercury speciation, during thermal treatment of a mercury contaminated soil. In the untreated soil, mercury was found concentrated in spherical particles, which were successively broken down upon thermal treatment. Hg0 and inorganic mercury compounds (presumably HgO(s) and HgSO4(s)) could be detected. No (CH3)2Hg and only traces of CH3Hg+ could be found. The dependence on temperature and heating time indicated that the evaporation of mercury from the soil was partly controlled by diffusion mechanisms. Mercury volatilized in two separate stages during heating; initial elemental vaporization, and subsequent volatilization of the oxide or sulfate phase at higher temperatures (>230°C). By thermal treatment at 470°C and 20 min, a removal of >99% of the mercury could be achieved.

  • 28.
    Werner, Kajsa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Borén, Eleonora
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Comprehensive study of the thermal decomposition of different hemicelluloses2013In: European Biomass Conference and Exhibition Proceedings: 21nd European Biomass Conference and Exhibition, ETA-Florens Renewable Energies , 2013, p. 944-946Conference paper (Other academic)
    Abstract [en]

    Carbohydrates (cellulose and hemicellulose) constitute the main fraction of plant cell walls and detailed knowledge about their thermal decomposition are therefore of great importance for understanding pyrolytic degradation properties of biomass. Hemicellulose is a diverse group of non-cellulosic polysaccharides and is composed of chains of different monomeric sugar units (pentoses, hexoses and hexuronic acids). The heterogeneous structures of hemicelluloses should be considered when evaluating the decomposition behavior. Nevertheless, thermal analysis of hemicellulose often uses the commercially available xylan as a model compound of hemicelluloses. In contrast to previous work several polysaccharides (xylan arabinogalactan, galactomannan, xyloglucan, and cellulose) were thoroughly investigated in the current study by thermogravimetric analysis, differential scanning calorimetry and pyrolysis-gas chromatography/mass spectrometry during heating in inert atmosphere. The results gave new insights into hemicellulose decomposition and demonstrated that different hemicelluloses have different decompoition behavior.

  • 29.
    Werner, Kajsa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Thermal decomposition of hemicelluloses2014In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 110, p. 130-137Article in journal (Refereed)
    Abstract [en]

    Decomposition modeling of biomass often uses commercially available xylan as model compound representing hemicelluloses, not taking in account the heterogeneous nature of that group of carbohydrates. In this study, the thermal decomposition behavior of seven different hemicelluloses (beta-glucan, arabinogalactan, arabinoxylan, galactomannan, glucomannan, xyloglucan, and xylan) were investigated in inert atmosphere using (i) thermogravimetric analysis coupled to Fourier transform infrared spectroscopy, (ii) differential scanning calorimetry, and (iii) pyrolysis-gas chromatography/mass spectroscopy. Results on decomposition characteristics (mass loss rate, reaction heat and evolving gas composition) were compared and summarized for the different hemicelluloses and for comparison also crystalline cellulose was included in the study. The mass loss rate characteristics differed between the polysaccharides, with cellulose and glucan-based hemicelluloses as the thermally most stable and xylan as the least stable sample. The heat flow during slow heating in nitrogen flow showed a much more exothermal decomposition of xylan compared with the other hemicelluloses. The composition of off-gases during heating showed large differences between the samples. During decomposition of xylan high levels of CO2 and lower levels of other components were formed, whereas also CO, methanol, methane, furfural, 5-hydroxymethylfurfural and anhydrosugars were formed in substantial amounts from the other polysaccharides. The formation of anhydrosugar was correlated to the monosaccharide composition of the polysaccharide chain. The results from the current study contribute to new knowledge concerning thermochemical behavior of different hemicelluloses.

  • 30.
    Wiklund Lindström, Susanne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nilsson, David
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordwaeger, Martin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Geladi, Paul
    Quality assurance of torrefied biomass using RGB, visual and near infrared (hyper) spectral image data2014In: Journal of Near Infrared Spectroscopy, ISSN 0967-0335, E-ISSN 1751-6552, Vol. 22, no 2, p. 129-139Article in journal (Refereed)
    Abstract [en]

    Visible and near infrared imaging techniques for analysing characteristics of torrefied biomass were evaluated for possible use in future online process control. The goal of such a control system is to identify products with the desired properties and reject products outside the specification. Two pushbroom hyperspectral cameras with different wavelength regions and a commercial digital colour camera were evaluated. The hyperspectrat cameras, short wave infrared (SWIR) and visible-near infrared (VNIR), covered the ranges of 1000-2500 nm and 400-1000 nm, respectively. The biomass was produced according to an experimental design in a torrefaction pilot plant at different temperatures, residence times, and nitrogen and steam flow rates to obtain a wide range of different characteristics and qualities of torrefied material. Chemical characteristics, heating values and milling energy of the different torrefied materials were analysed or calculated using standardized procedures and were used for calibration. For the hyperspectral images, a principal-component analysis was performed on the absorbance spectra. The score plots and score images were used interactively to separate background, outlier pixels and shading effects from sample signal. Averaged spectra of individual torrefied woodchips were used. Partial least-squares regression was used to relate average spectra to heating values and chemical characteristics of the torrefied biomass. Owing to the small size of the data sets, cross-validation using leave-one-out validation was used for testing the models. The ratio of standard error of prediction to sample standard deviation (RPD) values were used for comparing the imaging techniques. For ROB images, all RPD values were 4 or lower. The RPD values for the VNIR technique were all below 5, while the SWIR images produced RPD values above 5 for eight of the 13 properties. The promising results of the SWIR technique strongly suggested that the torrefied biomass undergoes changes to chemical structures, which are not necessarily manifested as changes to the colour of the material.

  • 31.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Borén, Eleonora
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hydrogen and carbon separation by low-temperature slow pyrolysis of biomass: experimental validationManuscript (preprint) (Other academic)
    Abstract [en]

    Previous work have indicated that slow pyrolysis may be used to separate hydrogen and carbon in a biomass feedstock into different product fractions. The hydrogen predominantly ends up in the pyrolysis gas fraction, whereas the carbon is mainly retained in the char. A system concept was suggested using low-temperature slow pyrolysis to achieve; a) transportation fuel/chemical production from the volatilized fraction, and b) potential carbon negativity by sequestering the carbon from the biochar fraction after use for electricity and/or heat production. The present work aimed to identify important process parameters, validate the hydrogen and carbon separation potential, and identify a potential process optimum for spruce wood slow pyrolysis. The process temperature was shown as the most important factor influencing the hydrogen and carbon pyrolysis gas yields, whereas the residence time factor only showed significant influence on the product yields for the shorter residence times. All experiments demonstrated significant hydrogen and carbon separation to gas and char respectively, particularly for lower process temperatures. An optimum process operation temperature was not found but from an industrial perspective, the suggested preferable temperature interval lies within the lowtemperature pyrolysis range (350-400°C), just above high temperature torrefaction (~300°C).

  • 32.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Khwaja, Salik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pilot scale experimental validation of the Bio2fuels low-temperature slow pyrolysis system conceptManuscript (preprint) (Other academic)
    Abstract [en]

    The “Bio2Fuels” concept previously suggested may potentially achieve a transport driven carbon negativity by use of a combination of; low-temperature slow pyrolysis/high-temperature torrefaction; gas reforming; fuel synthesis; coal replacement by the solid bio-coal stream; and CCS of the resulting flue gases. The initial pre-treatment process suggested may potentially exhibit several advantages and may well facilitate an appealing and cost-efficient conversion system. The present work was comprised of pilot-scale pyrolysis experiments on softwood pellets using a continuous auger screw torrefaction/pyrolysis reactor for validation of the process in the temperature range of 300-425°C. All products were analyzed for composition and the pyrolysis gas (permanent gases + bio-oil) was sampled for particulate matter, permanent gas and bio-oil composition. The volatilization propensity of ash-forming elements was analyzed based on alkali deposits on impactor plates with SEM analysis and ICP-AES analysis of the bio-oil. The volatilization of sulfur and chlorine was also evaluated via char retainment. In addition, an initial test run of thermal pyrolysis gas reforming was performed by operating the thermal oxidation burner in gasification/reforming mode. The results showed that the hydrogen and oxygen in the biomass feedstock were volatilized at lower temperatures than the feedstock carbon, with the desired resulting hydrogen/carbon separation into pyrolysis gas and biochar, but also enrichment of oxygen in the pyrolysis gas. The hydrogen pyrolysis gas yield was >75% for pyrolysis temperatures ≥375°C and the corresponding carbon gas yield ranged from 50% to 63%. Most of the hydrogen in the pyrolysis gas was bound in the bio-oil as water and various hydrocarbons. No significant volatilization of alkali elements was observed through either analysis method. The most abundant permanent gas formed was CO2 and with a CH4 concentration of about 9%vol. The thermal reforming experiments also demonstrated a high CH4 syngas concentration, strongly indicating the need for a catalytic reforming process.

  • 33.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lindh, Ingemar
    Bioendev AB.
    Kollberg, Kristoffer
    Sigma Industry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Torrefaction and gasification of lignocellulosic hydrolysis residue from bio-ethanol productionManuscript (preprint) (Other academic)
    Abstract [en]

    Production of lignocellulosic ethanol through hydrolysis (acid or enzymatic) combined with fermentation generate a large amount of residue consisting of mainly lignin and un-ydrolyzed cellulose. The significant amount of energy retained in this residue require further conversion as a measure to ensure economic viability for the total process. Thermal conversion of the hydrolysis residue through gasification for syngas production would improve the fuel yield in addition to the overall plant efficiency. Also, torrefaction of various biomass feedstocks has been shown to significantly improve biomass fuel characteristics in addition to having substantial positive effect on the energy consumption of the particle size reduction. The present work was an evaluation of hydrolysis residue and torrefied hydrolysis residue as gasification feedstocks in a bench-scale fluidized bed gasifier, based on syngas composition, particle formation, tar production and volatilization behavior. In addition, the effects of torrefaction on hydrolysis residue material characteristics were separately evaluated, including the influence of the process parameters on milling energy consumption and morphology. All torrefaction data was fitted to multiple linear regression models with good reproducibility and fit. The results confirm the previously reported improved feedstock characteristics resulting from torrefaction of biomass, however residence time was proved the most influential process parameter on the torrefaction severity, most likely derived from the lack of hemicellulose in the residue. The resulting syngas composition and quality indicated that both non-torrefied and torrefied hydrolysis residue were suitable gasification feedstocks. The hydrolysis residue product gas had elevated tar concentration but the torrefied residue demonstrated a significant reduction in the tar content (particularly the heavy tar components), compared to both raw hydrolyis residue and the wood reference feedstock. Hence, torrefaction may significantly reduce tar related problems in downstream equipment/processes.

  • 34.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Low-temperature slow pyrolysis of biomass for H2-enriched syngas production and carbon negativityManuscript (preprint) (Other academic)
    Abstract [en]

    To optimally utilize biomass resources as feedstock for fuels and chemicals production as well as for a potential substantial carbon sink, a dedicated process and system concept is suggested. The desired outcome of the process is a hydrogen-enriched pyrolysis gas and a carbon-enriched char, also retaining the ash-forming elements. To obtain a transport-driven large-scale CO2 negative system, the char is suggested as co-firing fuel in a facility with carbon capture and storage technology. In the present work, the basis for this Bio2Fuels separation concept was evaluated by 1) analysis of previously published empirical data for pyrolysis, and 2) chemical equilibrium calculations. The former analysis indicated on the potential for a significant separation of H and C to the pyrolysis gas and char respectively, with ~80% of the hydrogen and 40-60% of the carbon from the raw feedstock present in the pyrolysis gas product. Based on analyzed thermochemical driving forces, most of the ash-forming elements can be expected to be retained in the char, and an ash and alkali-free gas may be achieved at temperatures below 500°C. In addition, chemical equilibrium modelling of the pyrolysis gas reforming demonstrated a significantly increased H2/CO ratio in the syngas compared to gasification of the raw biomass.

  • 35.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Syngas production by combined biomass gasification and in situ biogas reforming2015In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, no 6, p. 3725-3731Article in journal (Refereed)
    Abstract [en]

    For small- to medium-sized streams of biogas (methane) produced at a biorefinery site where cost-efficient reforming by traditional methods are unavailable, combined biomass gasification and methane reforming could facilitate co-conversion and increase the H-2/CO ratio in the syngas from the gasification plant. In the present work, co-gasification of biomass with CH4 was evaluated by means of a parametric chemical equilibrium study for both wood/CH4 and black liquor/CH4 feedstocks and bench-scale fluidized-bed gasification experiments for a wood/peat/CH4 fuel mixture. The parametric study indicated that high-temperature, and steam and oxygen addition all facilitate a high conversion rate, i.e., methane reforming. Evaluating the influence of the gasification temperature on CH4 reforming and increasing the H-2/CO ratio experimentally demonstrated that high temperatures are required for efficient co-conversion.

  • 36.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Syngas production by combined biomass gasification and in-situ methane reformingManuscript (preprint) (Other academic)
1 - 36 of 36
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