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  • 1. Bergström, Dan
    et al.
    Israelsson, Samuel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Dahlqvist, Sten-Axel
    Gref, Rolf
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Wästerlund, Iwan
    Effects of raw material particle size distribution on the characteristics of Scots pine sawdust fuel pellets2008Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 89, nr 12, s. 1324-1329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to study the influence of raw material particle size distribution on the pelletizing process and the physical and thermomechanical characteristics of typical fuel pellets, saw dust of Scots pine was used as raw material for producing pellets in a semi industrial scaled mill (similar to 300 kg h(-1)). The raw materials were screened to a narrow particle size distribution and mixed into four different batches and then pelletized under controlled conditions. Physical pellet characteristics like compression strength, densities, moisture content, moisture absorption and abrasion resistance were determined. In addition, the thermochemical characteristics, i.e. drying and initial pyrolysis, flaming pyrolysis, char combustion and char yield were determined at different experimental conditions by using a laboratory-scaled furnace. The results indicate that the particle size distribution had some effect on current consumption and compression strength but no evident effect on single pellet and bulk density, moisture content, moisture absorption during storage and abrasion resistance. Differences in average total conversion time determined for pellet batches tested under the same combustion conditions was less than 5% and not significant. The results are of practical importance suggesting that grinding of saw dust particle sizes below 8 mm is probably needless when producing softwood pellets. Thus it seem that less energy could be used if only over sized particles are grinded before pelletizing.

  • 2. Bergström, Dan
    et al.
    Israelsson, Samuel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Dahlqvist, Sten-Axel
    Gref, Rolf
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Wästerlund, Iwan
    Effects of raw material particle size distribution on the characteristics of Scots pine sawdust fuel pellets2008Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 89, nr 12, s. 1324-1329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to study the influence of raw material particle size distribution on the pelletizing process and the physical and thermomechanical characteristics of typical fuel pellets, saw dust of Scots pine was used as raw material for producing pellets in a semi industrial scaled mill (similar to 300 kg h(-1)). The raw materials were screened to a narrow particle size distribution and mixed into four different batches and then pelletized under controlled conditions. Physical pellet characteristics like compression strength, densities, moisture content, moisture absorption and abrasion resistance were determined. In addition, the thermochemical characteristics, i.e. drying and initial pyrolysis, flaming pyrolysis, char combustion and char yield were determined at different experimental conditions by using a laboratory-scaled furnace. The results indicate that the particle size distribution had some effect on current consumption and compression strength but no evident effect on single pellet and bulk density, moisture content, moisture absorption during storage and abrasion resistance. Differences in average total conversion time determined for pellet batches tested under the same combustion conditions was less than 5% and not significant. The results are of practical importance suggesting that grinding of saw dust particle sizes below 8 mm is probably needless when producing softwood pellets. Thus it seem that less energy could be used if only over sized particles are grinded before pelletizing.

  • 3.
    Borén, Eleonora
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Larsson, Sylvia H.
    Thyrel, Mikael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Averheim, Andreas
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    VOC off-gassing from pelletized steam exploded softwood bark: emissions at different industrial process stepsIngår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Formation of hazardous gases during transport and storage of biomass for large-scale bioenergy production is an important safety concern. While off-gassing has been addressed in numerous studies for raw woody biomass, very few describe it in the context of biomass for bioenergy production pre-treated by thermal technologies such as steam explosion. Volatile Organic Components (VOCs) are expected to be altered by the treatment, but until now there is no research published on VOC profiles of steam exploded materials in industrial scale. In the present study, VOCs emitted from the products were evaluated by sampling from different production steps from steam explosion of softwood bark, and following the production chain including also pelletization. Off-gasses were actively sampled using Tenax TA absorbent and analyzed by GC-MS. The VOC formation dependency of operation and storage conditions at different process steps was evaluated by multivariate statistical analysis. We showed that the different process steps along the production line was the main influencing factor for VOC off-gassing amounts, with highest VOC levels directly after the steam explosion process. Treatment severity mainly altered the relative composition of VOC profiles with more terpenes emitted from milder treatment, whereas more severe treatment shifted VOCs composition to contain more furans, e.g. furfural. In summary, treatment by steam explosion leads to potentially problematic VOC off-gassing profiles from the material, and levels vary considerable along the production line. The findings are important from a fuel handling and working environment perspective.

  • 4.
    Borén, Eleonora
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå University Industrial Doctoral School for Research and Innovation, Sweden.
    Larsson, Sylvia H.
    Thyrel, Mikael
    Averheim, Andreas
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    VOC off-gassing from pelletized steam exploded softwood bark: emissions at different industrial process steps2018Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 171, s. 70-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Formation of hazardous gases during transport and storage of biomass for large-scale bioenergy production is an important safety concern. While off-gassing has been addressed in numerous studies for raw woody biomass, very few describe it in the context of biomass for bioenergy production pre-treated by thermal technologies such as steam explosion. Volatile Organic Components (VOCs) are expected to be altered by the treatment, but until now there is no research published on VOC profiles of steam exploded materials in industrial scale. In the present study, VOCs emitted from the products were evaluated by sampling from different production steps from steam explosion of softwood bark, and following the production chain including also pelletization. Off-gasses were actively sampled using Tenax TA absorbent and analyzed by GC–MS. The VOC formation dependency of operation and storage conditions at different process steps was evaluated by multivariate statistical analysis. We showed that the different process steps along the production line was the main influencing factor for VOC off-gassing amounts, with highest VOC levels directly after the steam explosion process. Treatment severity mainly altered the relative composition of VOC profiles with more terpenes emitted from milder treatment, whereas more severe treatment shifted VOCs composition to contain more furans, e.g. furfural. In summary, treatment by steam explosion leads to potentially problematic VOC off-gassing profiles from the material, and levels vary considerable along the production line. The findings are important from a fuel handling and working environment perspective.

  • 5.
    Broström, Markus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Enestam, Sonja
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Mäkelä, Kari
    Condensation in the KCl–NaCl system2013Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 105, s. 142-148Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Condensation of gaseous KCl and NaCl is known to participate in deposit formation and high temperature corrosion processes in heat and power plants. Little is known about interaction between the two salts, which is of interest for the overall understanding of deposit and corrosion problems. Within this study, condensation at different material surface temperatures and salt mixtures was investigated.

    Salt vapors were prepared by temperature controlled evaporation. A cooled condensation probe with a temperature gradient was inserted in the hot gas. After exposure, the probe surface was visually inspected and analyzed with SEM/EDS and XRD for elemental and phase composition. TGA/DTA was used to provide complementary information on vaporization and sintering.

    The results indicated that a mixture of KCl and NaCl probably condenses as separate phases at concentrations and temperatures below the melting points of the salts. Condensation was possibly followed by a secondary sintering process. It was verified by TGA/DTA that a mixture of solid KCl and NaCl particles sinters and melts rapidly at temperatures above the melting temperature of a corresponding solution. It was also seen that sintering took place at lower temperatures with slow solid-gas interactions, possibly with the formation of solid solutions.

  • 6.
    Broström, Markus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Kassman, Håkan
    Vattenfall Power Consultant AB, Box 1046, SE-611 29 Nyköping, Sweden.
    Helgesson, Anna
    Vattenfall Research and Development AB, SE-814 26 Älvkarleby, Sweden.
    Berg, Magnus
    Vattenfall Research and Development AB, SE-814 26 Älvkarleby, Sweden.
    Andersson, Christer
    Vattenfall Research and Development AB, SE-814 26 Älvkarleby, Sweden.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Sulfation of corrosive alkali chlorides by ammonium sulfate in a biomass fired CFB boiler2007Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 88, nr 11-12, s. 1171-1177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biomass and waste derived fuels contain relatively high amounts of alkali and chlorine, but contain very little sulfur. Combustion of such fuels can result in increased deposit formation and superheater corrosion. These problems can be reduced by using a sulfur containing additive, such as ammonium sulfate, which reacts with the alkali chlorides and forms less corrosive sulfates. Ammonium sulfate injection together with a so-called in situ alkali chloride monitor (IACM) is patented and known as "ChlorOut". IACM measures the concentrations of alkali chlorides (mainly KCl in biomass combustion) at superheater temperatures. Tests with and without spraying ammonium sulfate into the flue gases have been performed in a 96MW(th)/25MW(e) circulating fluidized bed (CFB) boiler. The boiler was fired mainly with bark and a chlorine containing waste. KCl concentration was reduced from more than 15 ppm to approximately 2 ppm. during injection of ammonium sulfate. Corrosion probe measurements indicated that both deposit formation and material loss due to corrosion were decreased using the additive. Analysis of the deposits showed significantly higher concentration of sulfur and almost no chlorine in the case with ammonium sulfate. Results from impactor measurements supported that KCl was sulfated to potassium sulfate by the additive. (C) 2007 Elsevier B.V. All rights reserved.

  • 7.
    Fagerström, Jonathan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Rebbling, Anders
    Olwa, Joseph
    Steinvall, Erik
    Boström, Dan
    Öhman, Marcus
    Boman, Christoffer
    Control strategies for reduction of alkali release during grate combustion of woody biomass: influence of process parameters and fuel additives2015Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188Artikel i tidskrift (Refereegranskat)
  • 8.
    Fagerström, Jonathan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Steinvall, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Alkali transformation during single pellet combustion of soft wood and wheat straw2016Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 143, s. 204-212Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Controlling slag and deposit formation during thermochemical fuel conversion requires a fundamental understanding about ash transformation. In this work, a macro-TGA reactor was used to determine the release of ash forming elements during devolatilization and char combustion of single pellets. Soft wood and wheat straw were combusted at two temperatures (700 °C and 1000 °C) and the residual ashes were collected and analyzed for morphology, elemental and phase composition. The results showed that the single pellet combustion exhibit similar release character as in grate boilers. The temporal release was found to be both temperature and fuel dependent. For wood, the release of potassium occurred mostly during char combustion regardless of furnace temperature. Similar results were found for straw at 700 °C, but the temperature increase to 1000 °C implied that the release occurred already during devolatilization. The differences are presumably explained by different fuel phase compositions. The residual ash were composed of three different categories of phases; crystalline compounds, molten ash (glass) and char, and the work concludes that K was captured by crystalline K/Ca-carbonates as well as in amorphous glassy silicates for wood, and by almost fully molten ash of glassy silicates for straw. The fuel conversion processes occurring on a grate influence the fuel combustibility in terms of e.g. burnout, slag formation and release of fine particle and deposit forming matter, and the present work has given novel insights into the specific alkali behavior during biomass fuel conversion.

  • 9. Grimm, Alejandro
    et al.
    Etula, Jarkko
    Salh, Roushdey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kalén, Gunnar
    Segerström, Markus
    Brücher, Jörg
    Söderberg, Christer
    Soukup, David
    Pfeifer, Christoph
    Larsson, Sylvia H.
    Slagging and fouling characteristics during co-combustion of Scots pine bark with low-temperature dried pulp and paper mill chemical sludge2019Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 193, s. 282-294Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper shows how chemical sludge (CS) generated during wastewater treatment at a paperboard mill can be quickly dried at low-temperature and employed in bark-fired boilers to reduce slagging and corrosion problems. By using a cyclone-dryer operated at an inlet-air velocity of 110 m/s and a temperature of 90 degrees C, the dry-matter content of CS was increased from approximately 19 to 82%. The residence time of CS inside the cyclone was approximately 2 s when using the inlet-air velocity mentioned above. Disaggregation of the feedstock caused by collisions with the cyclone wall and between particles played a crucial role in enhancing the efficiency of heat and mass transfer. Three co-pelletized mixtures of Scots pine bark (SPB) and dried-CS were combusted in a 40 kW fixed-bed burner. Flue gas analysis was performed with a gas analyser. Coarse and fine ash were analysed by SEM-EDS and XRD. NO,, and SO2 emissions increased with increasing amount of CS in the mixtures. Mono combustion of SPB resulted in a large quantity of slag (i.e., molten ash) with a high degree of sintering (i.e., hardness of the slag), and ash deposits formed on heat transfer surfaces were rich in K2SO4 and KCI. Mixtures of SPB and CS were less prone to slagging, and the amount of alkali chloride in the deposits was reduced in favour of alkali sulphate formation.

  • 10. Hedman, Bjorn
    et al.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Zhu, Wanbin
    Orberg, Hakan
    Xiong, Shaojun
    Enhancing fuel qualities of cassava crop residues by washing2015Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 139, s. 127-134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cassava (Manihot esculenta Crantz) stems, being waste residues after harvesting starchy roots, are a potential bio-fuel resource. However high concentrations of ash and elements Cl, K, etc. in the stems may cause severe deposition, corrosion and particle emissions, in addition to slagging during combustion. This study tests washing by water as a pretreatment to reduce the problems. A 3-level full factorial designed experiment was conducted with washing time (<1800 s) and temperature (20-40 degrees C) as factors and fuel characteristics as responses. The effect of milling particle size was also examined in a supplementary experiment. After washing, the net calorific value of the biomass tended to be higher, though not significant. Both washing time and temperature increased C but decreased H, while N and S content decreased with time only. A short washing of 50s decreased the ash content by approximately 50% and Cl around 75%, followed by K and P that decreased to 50% after 5 min. Smaller milling size resulted in a larger amount of starch washed away, but no significant change in content of total ash and individual elements, except for Cl which was significantly higher in the smaller particles. The effect of washing on the ash composition is visualized in a ternary diagram, showing that the risk for slagging and fine particle emissions is reduced. A reduction in the risk of corrosion is also predicted as indicated by a relatively higher ratio of S/Cl and lower Cl/(K + Na). Thus, in addition to extraction of starch, the washing can also improve fuel quality of the residual biomass. 

  • 11. Kuba, Matthias
    et al.
    He, Hanbing
    Kirnbauer, Friedrich
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Ohman, Marcus
    Hofbauer, Hermann
    Deposit build-up and ash behavior in dual fluid bed steam gasification of logging residues in an industrial power plant2015Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 139, s. 33-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A promising way to substitute fossil fuels for production of electricity, heat, fuels for transportation and synthetic chemicals is biomass steam gasification in a dual fluidized bed (DFB). Using lower-cost feedstock, such as logging residues, instead of stemwood, improves the economic operation. In Senden, near Ulm in Germany, the first plant using logging residues is successfully operated by Stadtwerke Ulm. The major difficulties are slagging and deposit build-up. This paper characterizes inorganic components of ash forming matter and draws conclusions regarding mechanisms of deposit build-up. Olivine is used as bed material. Impurities, e.g., quartz, brought into the fluidized bed with the feedstock play a critical role. Interaction with biomass ash leads to formation of potassium silicates, decreasing the melting temperature. Recirculation of coarse ash back into combustion leads to enrichment of critical fragments. Improving the management of inorganic streams and controlling temperature levels is essential for operation with logging residues. (C) 2015 Elsevier B.V. All rights reserved.

  • 12.
    Lundholm, Karin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Trace element speciation in combustion processes: review and compilatons of thermodynamic data2007Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 88, nr 11-12, s. 1061-1070Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chemical equilibrium calculations are often used to determine the fate of trace metals in combustion processes and to study the effects of different process variables and varying fuel compositions. In the present report, thermodynamic data on compounds containing the trace elements As, Cd, Cr, Cu and Pb from different database sources are compared. The results showed significant differences between existing databases in both number of compounds included in the databases and thermodynamic data. The differences also significantly affected the outcome of the equilibrium calculations.

  • 13. Moradian, Farzad
    et al.
    Tchoffor, Placid A.
    Davidsson, Kent O.
    Pettersson, Anita
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Thermodynamic equilibrium prediction of bed agglomeration tendency in dual fluidized-bed gasification of forest residues2016Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 154, s. 82-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dual fluidized-bed (DFB) gasification is one of the recently developed technologies for production of heat, power, transportation fuels and synthetic chemicals through steam gasification of biomass. Bed agglomeration is a serious ash-related problem that should be taken into account when biomass-based fuels are selected for fluidized bed gasification and combustion. This study developed a thermodynamic equilibrium model to assess the risk of bed agglomeration in gasification and combustion reactors of a DFB gasifier using biomass (forest residues) as feedstock. The modelling approach combined thermodynamic equilibrium calculations with chemical fractionation technique to predict the composition and melting behaviour of the fuel-derived ash as well as bed particles coating layer in the gasification and combustion reactors. FactSage was employed for the thermodynamic equilibrium calculations. The modelling results were then compared with experimental data obtained from a full-scale DFB gasifier to estimate the reliability and validity of the predictive model. In general, a good agreement was found between the modelling results and experimental observations. For the forest residues as feedstock and olivine as bed material, the modelling results indicate a low risk of bed agglomeration in the DFB gasifier, as long as the dominant temperature in the combustion zone is below 1020 degrees C. In contrast, quartz as bed material in the DFB gasifier was shown to significantly increase the risk of bed agglomeration through coating-induced agglomeration mechanism. 

  • 14. Nordgren, Daniel
    et al.
    Hedman, Henry
    Padban, Nader
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Ash transformations in pulverised fuel co-combustion of straw and woody biomass2013Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 105, s. 52-58Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ash transformation processes have been studied during co-firing of wheat straw and pine stem wood and softwood bark. Pilot-scale trials in a 150 kW pulverised-fuel-fired burner were performed. Thermodynamic equilibrium calculations were made to support the interpretation of the results. The results show that reactions involving condensed phases are kinetically limited compared to reactions between gaseous ash compounds. Accordingly, the conditions promote gas phase reactions resulting in the formation of chlorides, sulphates and carbonates whereas reactions involving condensed reactants are suppressed. Both the slagging and fouling propensities of all co-firing mixes were reduced compared to that for pure straw. For the wood/straw mixes this was mainly due to a dilution of the ash forming elements of straw whereas for straw/bark, an additional effect from interaction between the fuel ash components was observed to reduce slagging. In general it can be concluded that under powder combustion conditions equilibrium is approached selectively and that the ash matter is strongly fractionated. The general results in this paper are useful for straw-fired power stations looking for alternative co-firing fuels.

  • 15.
    Persson, Kristoffer
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Carlsson, Jörgen
    Umeå Energi AB, Box 224, 901 05 Umeå, Sweden.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    High temperature corrosion in a 65 MW waste to energy plant2007Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 88, nr 11-12, s. 1178-1182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Incineration of municipal solid waste is often associated with high temperature corrosion problems. This paper presents results of full-scale corrosion tests in a 65 MW waste fired combined heat and power plant. A failure case indicated alarmingly high corrosion rate of the superheater tubes. Corrosion tests with five different alloys were carried out within this work in order to determine plant specific corrosion rates on different superheater materials. Additional tests were done to determine the effect on the corrosion rate from adding chlorine containing polyvinyl chloride to the ordinary fuel mix. A corrosion probe with metal temperatures ranging from 320 degrees C to 460 degrees C was used to estimate corrosion loss and to collect deposits. The sampling was performed at a flue gas temperature of 470 degrees C for 10 days. The probe rings were analysed using scanning electron microscope and micrometer measurements to determine the deposit chemistry and corrosion rates. The results showed significant differences in corrosion rates depending on tube material. Chlorine was shown to have a key role in the corrosion process, even at these relatively low temperatures. The results indicated a chlorine induced corrosion mechanism involving volatile iron chloride with a high corrosion rate on the superheater materials typically used. Addition of extra polyvinyl chloride to the fuel mix had an increasing effect on the corrosion. (C) 2007 Elsevier B.V. All rights reserved.

  • 16. Samuelsson, Robert
    et al.
    Thyrel, Mikael
    Sjöström, Michael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lestander, Torbjörn A
    Effect of biomaterial characteristics on pelletizing properties and biofuel pellet quality2009Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 90, nr 9, s. 1129-1134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sawdust of conifers as a by-product from saw mills is the most commonly used biomaterial for pellet production in Sweden today. Experiences from the biofuel pellet industry indicate that different biomaterial properties influence the final pellet quality. A systematic study was conducted where five factors were varied according to a two level fractional factorial design. The factors were: tree species (Scots pine, Norway spruce); origin of growth-place (latitudes 57 and 64°N); storage time of sawdust (0 and 140 days), moisture content (9 and 12%) and steam treatment (2 and 6 kg/h). The measured responses bulk density and mechanical durability represented the pellet quality while the press current and the fines produced in the pelletizing process were measures of the pelletizing property.

    The results showed that low moisture content and long storage time resulted in increased bulk densities and press currents. For mechanical durability and fines, a long storage time and intermediate moisture contents were found favourable. In addition, indications were found that the reduction of fatty and resin acids during the storage also influenced the pelletizing properties and the pellet quality.

  • 17.
    Skoglund, Nils
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Energy Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology.
    Bäfver, Linda
    Fahlström, Johan
    Holmén, Erik
    Renström, Caroline
    Fuel design in co-combustion of demolition wood chips and municipal sewage sludge2016Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 141, nr 2, s. 196-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Municipal sewage sludge (MSS) is a waste stream resource which contains both energy and elements such as phosphorus which could be recycled. If these two aspects of this waste stream resource are to be used to their full potential the sludge should not be used in landfills or road construction. There is some use of sludge in agriculture today but not all MSS produced is suitable for direct use on arable land due to its content of potentially harmful elements, pathogens or anthropogenic chemicals. By combusting sludge that is not used directly in agriculture the problematic organic content could be destroyed. The combustion process also produces an ash that possibly could be used either directly in agriculture or as a raw material for recovering phosphorus and energy could be recovered. Building mono-combustion plants for sewage sludge is not economically feasible in all parts of the world so it is of interest to investigate how MSS can be introduced together with other fuels in existing infrastructure which already have extensive cleaning systems for potentially harmful elements. To investigate this possible path, demolition wood chips (DWC) were co-combusted with municipal sewage sludge (MSS) in a grate-fired combined heat and power plant running at 50% capacity producing 25 MWth and 9 MWel. The amount of MSS that was suitable to introduce in blends was determined using a "fuel fingerprint" based on the composition of the raw materials. Thermodynamic equilibrium calculations were made to evaluate potential problems with slagging based on the ash content prior to the combustion experiments. The fuels were introduced as a reference case with only demolition wood and pre-blended fuel mixtures in two ratios; 65 w/w-% DWC/35 w/w-% MSS and 55 w/w-% DWC/45 w/w-% MSS and were fired for 12 h. The high water content of the MSS affected how much MSS that could be introduced without compromising the heat and power production. The fuel blends worked nicely for 12 h of continuous combustion with small adjustments where the primarily the air inlet configuration was changed. The main problems encountered related to cleaning of the flue gases and to some extent ash removal. The bed ash and fly ash produced was analysed both using ICP-AES (elemental) and XRD (speciation) and the bottom ash was subjected to ash melting tests. The major nutrient phosphorus was mainly found in bottom ash (80 w/w-%) as whitlockites with some hydroxyapatite whereas fly ash (20 w/w-%) contained larger amounts of hydroxyapatite, especially for the reference fuel. The amount of alkali chloride in the fly ash was reduced in favour of alkali sulphate formation.

  • 18.
    Skoglund, Nils
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Energy Engineering, Department of Engineering Sciences & Mathematics, Luleå University of Technology, Luleå, Sweden.
    Werner, Kajsa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nylund, Göran M.
    University of Gothenburg, Department of Marine Sciences - Tjärnö.
    Pavia, Henrik
    University of Gothenburg, Department of Marine Sciences - Tjärnö.
    Albers, Eva
    Chalmers University of Technology, Department of Biology and Biological Engineering, Division Industrial Biotechnology.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Combustion of seaweed: a fuel design strategy2017Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 165, s. 155-161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The high ash content and varying ash composition in algal biomass is often mentioned as problematic if to beused for thermal energy conversion. This paper suggests an approach where detailed information on ash compositionand predicted ash formation reactions are basis for successful remedies enabling the use of fuels consideredto be difficult. The procedure is demonstrated on seaweed (Saccharina latissima) cultivated for biorefinery purposes. The ash composition of the seaweed was found suitable for co-combustion with Miscanthus x giganteus, an energy crop high in alkali and silicon. Fuel mixtures were combusted in a bubbling fluidized bed reactorand ash samples were analyzed by SEM-EDS and XRD. The results showed that Ca from the seaweed was veryreactive and thus efficient in solving the silicatemelting problems. The fuel design approach was proven successfuland the potential for using otherwise difficult seaweed fuels in synergetic co-combustion was demonstrated.

  • 19.
    Strandberg, Anna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Holmgren, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Predicting fuel properties of biomass using thermogravimetry and multivariate data analysis2017Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 156, s. 107-112Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simple and reliable characterization methods for determining fuel properties of biomass are needed for several different applications. This paper describes and demonstrates such a method combining thermogravimetric analysis with multivariate data analysis, based on the thermal decomposition behavior of the fuel. Materials used for the tests were milled samples of wood chips thermally pretreated under different conditions in a torrefaction pilot plant. The predictions using the multivariate model were compared to those from a conventional curve deconvolution approach. The multivariate approach showed better and more flexible performance, with error of prediction of 2.7% for Mass Yield prediction, compared to the reference method that resulted in 29.4% error. This multivariate method could handle samples pretreated under more severe conditions compared to the curve deconvolution methods. Elemental composition, heating value and volatile content were also predicted with even higher accuracies. The results highlight the usefulness of the method and also the importance of using calibration data of good quality. (C) 2016 Elsevier B.V. All rights reserved.

  • 20.
    Strandberg, Anna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Thyrel, Mikael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Umeå, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Lestander, Torbjörn A.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Umeå, Sweden.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Biomass pellet combustion: cavities and ash formation characterized by synchrotron X-ray micro-tomography2018Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 176, s. 211-220Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ash formation during thermochemical conversion of biomass-based pellets influences both char conversion rates and ash-related operational problems. The objective of the present study was to provide detailed insights into changes in fuel and ash properties during fuel conversion. Pellets of poplar wood and wheat straw were used as model biofuels, representing vastly different compositions of ash-forming elements. Pellet samples at different char conversion phases were analyzed by synchrotron-based 3D X-ray micro-tomography, to map and visualize the development of cracks, internal cavities, and ash layers during conversion. The analysis of ash layers was complemented by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. The results provide new insights into how large cracks and internal cavities are developed already during devolatilization, for example, the poplar wood pellets had a 64% void fraction after the devolatilization stage. As expected, there were large variations between the ash layer properties for the two fuels. A porous, low density, and calcium-rich ash was formed from the poplar fuel, whereas the wheat straw ash was a high-density silicate melt that developed into bubbles on the surface. As the conversion proceeded, the wheat straw ash covered parts of the active char surface area, but without blocking the gas transport.

  • 21.
    Strandberg, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Ingemar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Pommer, Linda
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Wiklund-Lindström, Susanne
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Åberg, Katarina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Effects of temperature and residence time on continuous torrefaction of spruce wood2015Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 134, s. 387-398Artikel i tidskrift (Refereegranskat)
    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.

  • 22.
    Trubetskaya, Anna
    et al.
    Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Bygning 229, Kgs. Lyngby 2800, Denmark.
    Jensen, Peter Arendt
    Jensen, Anker Degn
    Llamas, Angel David Garcia
    Umeki, Kentaro
    Glarborg, Peter
    Effect of fast pyrolysis conditions on biomass solid residues at high temperatures2016Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 143, s. 118-129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fast pyrolysis of wood and straw was conducted in a drop tube furnace (DTF) and compared with corresponding data from a wire mesh reactor (WMR) to study the influence of temperature (1000-1400)°C, biomass origin (pinewood, beechwood, wheat straw, alfalfa straw), and heating rate (103 °C/s, 104 °C/s) on the char yield and morphology. Scanning electron microscopy (SEM), elemental analysis, and ash compositional analysis were applied to characterize the effect of operational conditions on the solid residues (char, soot) and gaseous products. The char yield from fast pyrolysis in the DTF setup was 3 to 7% (daf) points lower than in the WMR. During fast pyrolysis pinewood underwent drastic morphological transformations, whereas beechwood and straw samples retained the original porous structure of the parental fuel with slight melting on the surface. The particle size of Danish wheat straw char decreased in its half-width with respect to the parental fuel, whereas the alfalfa straw char particle size remained unaltered at higher temperatures. Soot particles in a range from 60 to 300 nm were obtained during fast pyrolysis. The soot yield from herbaceous fuels was lower than from wood samples, possibly due to differences in the content of lignin and resin acids.

  • 23. Trubetskaya, Anna
    et al.
    Jensen, Peter Arendt
    Jensen, Anker Degn
    Steibel, Markus
    Spliethoff, Hartmut
    Glarborg, Peter
    Influence of fast pyrolysis conditions on yield and structural transformation of biomass chars2015Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 140, s. 205-214Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fast pyrolysis of biomass (wood, straw, rice husk) and its major components (cellulose, hemicellulose, lignin) was conducted in a wire mesh reactor. The aim of this study was to understand the influence of temperature (350-1400 ∗ C), heating rate (10-3000 ∗ C/s), particle size (0.05-2 mm) and holding time (1-4 s) on the char morphology and char yield. Scanning electron microscopy (SEM) and elemental analysis were conducted to determine the effect of operating conditions on char softening and melting during pyrolysis. The char yield decreased with heating rate for rates ≤ 600 ∗ C/s; above this value a similar biomass char yield was obtained. The potassium content affected the char yield stronger than other minerals, while the distribution of the three major biomass constituents (cellulose, hemicellulose, lignin) affected the char yield only to a minor degree. Moreover, it was found that the heat treatment temperature had a larger influence on the char yield than the heating rate. Scanning electron microscopy indicated different types of biomass char plasticization influenced by the applied temperatures, heating rates, particle sizes and holding times, except for the rice husk char that formed chars with a structure similar to the parental fuel at all conditions. The less severe morphological changes of rice husk char were attributed to a high silica content.

  • 24.
    Trubetskaya, Anna
    et al.
    Department of Energy Engineering, Luleå University of Technology, Luleå 97187, Sweden.
    Poyraz, Yunus
    Weber, Roman
    Wadembäck, Johan
    Secondary comminution of wood pellets in power plant and laboratory-scale mills2017Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 160, s. 216-227Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study aims to determine the influence of mill type and pellet wood composition on particle size and shape of milled wood. The size and shape characteristics of pellets comminuted using power plant roller mills were compared with those obtained by using laboratory-scale roller- and hammer mills. A 2D dynamic imaging device was used for particle characterization. It was shown that mill type has a significant impact on particle size but an almost negligible effect on the shape of milled wood. Comminution in the pilot plant using a Loesche roller mill requires less energy than using a hammer mill, but generates a larger fraction of coarse particles. The laboratory-scale roller mill provides comparable results with the power plant roller mill with respect to particle size and shape.

  • 25.
    Vicente, Estela D.
    et al.
    Centre of Environmental and Marine Studies.
    Vicente, Ana
    Centre of Environmental and Marine Studies.
    Evtyugina, Margarita
    Centre of Environmental and Marine Studies.
    Carvalho, Ricardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Centre of Environmental and Marine Studies.
    Tarelho, Luís A. C.
    Centre of Environmental and Marine Studies.
    Oduber, Fernanda I.
    Department of Physics, Universidad de León.
    Alves, Célia
    Centre of Environmental and Marine Studies.
    Particulate and gaseous emissions from charcoal combustion in barbecue grills2018Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 176, s. 296-306Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of charcoal for cooking and heating can be a major source of air pollution and lead to a wide range of health outcomes. The aim of this study was to experimentally quantify and characterise the gaseous and particulate matter (PM2.5) emissions from charcoal combustion in a typical brick barbecue grill. The gaseous emission factors were 219 ± 44.8 g kg−1 for carbon monoxide (CO), 3.01 ± 0.698 g kg−1 for nitrogen oxides (NOxexpressed as NO2), and 4.33 ± 1.53 gC kg−1 for total organic carbon (TOC). Particle emissions (7.38 ± 0.353 g kg−1 of dry charcoal burned) were of the same order of magnitude as those from traditional residential wood burning appliances. About 50% of the PM2.5 emitted had a carbonaceous nature while water soluble ions accounted, on average, for 17% of the particulate mass. Alkanes (C11–C16 and C23), hopanes, steranes and alkyl-PAHs accounted for small mass fractions of PM2.5. Phenolic compounds and saccharides represented the major particle-bond organic constituents. The high proportion of either resin acids or syringyl and vanillyl compounds is consistent with emissions from charred coniferous wood. The ratios between anhydrosugars for charcoal are much lower than the values reported for lignite combustion, but overlap those from other biomass burning sources.

  • 26. Weiland, Fredrik
    et al.
    Nordwaeger, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Ingemar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Wiinikka, Henrik
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Entrained flow gasification of torrefied wood residues2014Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 125, s. 51-58Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, four different fuels were gasified in a pressurized entrained flow pilot plant gasifier at approximately 270 kW(th). The different fuels were; two torrefied wood residues, one raw wood residue and one torrefied stem wood. The system pressure and oxygen equivalence ratio (lambda) were held constant for all four gasification experiments. It was found that the torrefaction pretreatment significantly reduced the milling energy consumption for fuel size reduction, which in turn contributed to increased gasification plant efficiency. Furthermore, the results indicate that the carbon conversion efficiency may be enhanced by an intermediate torrefaction pretreatment, whereas both less severe torrefaction and more severe torrefaction resulted in reduced carbon conversions. The results also indicate that the CH4 yield was significantly reduced for the most severely torrefied fuel.

  • 27. Zhu, Youjian
    et al.
    van Eyk, Philip J.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Kirtania, Kawnish
    Piotrowska, Patrycja
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    de Nys, Rocky
    Bhattacharya, Sankar
    Gentili, Francesco G.
    Ashman, Peter J.
    Preliminary understanding on the ash behavior of algae during co-gasification in an entrained flow reactor2018Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 175, s. 26-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Algae are considered as a promising alternative fuel to produce energy due to its advantages such as high production yield, short growth cycle and flexible growing environment. Unfortunately, ash-related issues restrict its thermochemical utilization due to the high ash content and especially the high alkali metal concentration. In this paper, the gasification performance and ash behavior were experimentally analysed for three macro- and micro-algal species. Clear differences in the proximate and ultimate compositions were found between the cultivated algae used in this study and macroalgae (seaweed) harvested from the marine environments. Algal biomass generally contained higher Na and P contents than lignocellulosic biomass. Microalgae also had a relatively high mineral content due to the impurities in the harvesting process which included centrifugal pumping followed by sedimentation. Co-gasification of 20 wt% algae with softwood was investigated using an entrained flow reactor. The addition of both macroalgal species Derbersia tenuissima and Oedogonium to softwood had a limited influence on the gas yields and carbon conversion. On the other hand, the addition of the microalgal species Scenedesmus significantly decreased the main gas yields and carbon conversion. Moreover, the addition of algae clearly changed the residual ash composition of the base fuel. Finally, a preliminary understanding of the ash behavior of the tested algae blends was obtained through the analysis of the fuel ashes and the collected residual ashes. Fouling and corrosion were presumably occurred during the co-gasification of wood/macroalgae blends in view of the high alkali metal content. Microalga Scenedesmus had a high mineral content which could potentially capture the alkali metal in the ash and mitigate fouling when gasified with softwood. The growing environment and harvesting method were found to be significantly affecting the ash behavior implying the need for careful consideration regarding co-gasification process.

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