Increasing the share of biomass, preferably by replacing fossil fuels, is one way to mitigate the present climate change. Fossil coal can be directly replaced by co-combustion of coal and biomass and fossil engine fuels (gasoline and diesel) could potentially partly be replaced by synthetic renewable fuels produced via entrained flow gasification of biomass. The use of biomass in these processes is so far limited, partly because of the fibrous and hygroscopic nature of biomass which leads to problem in storing, transportation, handling and feeding. This thesis demonstrates how the challenging characteristics of raw biomass are mitigated by the pretreatment method torrefaction. Torrefaction is a process where biomass is heated in an oxygen deficient atmosphere to typically between 240 and 350°C for a time period of 2 minutes to 1 hour. Most of the torrefaction R&D in the literature have so far been performed with bench-scale batch reactors. For the purpose of carefully studying continuous torrefaction, a 20 kg/h torrefaction pilot plant was therefore designed, constructed and evaluated. The overall conclusion from this thesis is that the many benefits of torrefied biomass are valid also when produced with a continuous pilot plant and for typically Swedish forest biomasses. Some of the documented improved biomass properties are increased heating value, increased energy density, higher friability (lower milling energy) and less hydrophilic biomass (less moisture uptake). Most of the improvements can be attributed to the decomposition of hemicellulose and cellulose during torrefaction. The most common variables for describing the torrefaction degree are mass yield or anhydrous weight loss but both are challenging to determine for continuous processes. We therefore evaluated three different methods (one existing and two new suggestions) to determine degree of torrefaction that not require measurement of mass loss. The degree of torrefaction based on analyzed higher heating value of the raw and torrefied biomass (DTFHHV) predicted mass yield most accurate and had lowest combined uncertainty. Pelletizing biomass enhance transportation and handling but results from pelletization of torrefied biomass is still very limited in the literature and mainly reported from single pellet presses. A pelletization study of torrefied spruce with a ring die in pilot scale was therefore performed. The bulk energy density was found to be 14.6 GJ/m3 for pelletized torrefied spruce (mass yield 75%), a 40% increase compared to regular white pellets and therefore are torrefied pellets more favorable for long distance transports. More optimization of the torrefied biomass and the pelletization process is though needed for acquiring industrial quality pellets with lower amount of fines and higher pellet durability than attained in the present study. Powders from milled raw biomass are generally problematic for feeding and handling and torrefied biomass has been proposed to mitigate these issues. The influence of torrefaction and pelletization on powder and particle properties after milling was therefore studied. The results show that powder from torrefied biomass were enhanced with higher bulk densities, lower angle of repose as well as smaller less elongated particles with less surface roughness. Even higher powder qualities were achieved by pelletizing the torrefied biomass before milling, i.e. another reason for commercial torrefied biomass to be pelletized. Entrained flow gasification (EFG) is a promising option for conversion of biomass to other more convenient renewable energy carriers such as electricity, liquid biofuels and green petrochemicals. Also for EFGs are torrefied fuels very limited studied. Raw and torrefied logging residues were successfully gasified in a pilot scale pressurized entrained flow biomass gasifier at 2 bar(a) with a fuel feed corresponding to 270 kWth. Significantly lower methane content (50% decrease) in the syngas was also demonstrated for the torrefied fuel with mass yield 49%. The low milling energy consumption for the torrefied fuels compared to the raw fuel was beneficial for the gasification plant efficiency.

The last couple of decades have seen entrained-flow gasification of black liquor (BL) undergo an incremental process of technical development as an alternative to combustion in a recovery boiler. The ability of the technology to combine chemical recovery with the production of clean syngas renders it a promising candidate for the transformation of chemical pulp mills into integrated forest biorefineries. However, techno-economic assessments have shown that blending BL with the more easily transportable pyrolysis oil (PO) can not only increase the system efficiency for methanol production but remove a significant roadblock to development by partially decoupling production capacity from limitations on black liquor availability. The verification and study of catalytic co-gasification in an industrially-relative scale can yield both scientifically interesting and practically useful results, yet it is a costly and time-consuming enterprise. The expense and time involved can be significantly reduced by performing thermodynamic equilibrium calculations using a model that has been validated with relevant experimental data. The main objective of this thesis was to study, understand, quantify and compare the gasification behaviour and process performance of black liquor and pyrolysis oil blends in pilot-scale. A secondary objective of this work was to demonstrate and assess the usefulness and accuracy of unconstrained thermodynamic equilibrium modelling as a tool for studying and predicting the characteristics of alkali-impregnated biomass entrained-flow gasification. The co-gasification of BL/PO blends was studied at the 3 MWth LTU Green Fuels pilot plant in a series of experimental studies between June 2015 and April 2016. The results of the studies showed that the blending of black liquor with the more energy rich pyrolysis oil increased the energetic efficiency of the BLG process without adversely affecting carbon conversion. The effect of blend ratio and reactor temperature on the gasification performance of PO and BL blends with up to 20 wt% PO was studied in order to assess the impact of alkali-dilution in fuel on the conversion characteristics. In addition to unblended BL, three blends with PO/BL ratios of 10/90, 15/85 and 20/80 wt% were gasified at a constant load of 2.75 MWth. The decrease in fuel inorganic content with increasing PO fraction resulted in more dilute green liquor (GL) and a greater portion of the feedstock carbon ended up in syngas as CO. As a consequence, the cold gas efficiency increased by about 5%-units. Carbon conversion was in the range 98.8-99.5% and did not vary systematically with either fuel composition or temperature. The validation of thermodynamic equilibrium simulation of black liquor and pyrolysis co-gasifications with experimental data revealed the need to be mindful of errors and uncertainities in fuel composition that can influence predictions of equilibrium temperature. However, provided due care is to taken to ensure the use of accurate fuel composition data, unconstrained TEMs can serve as a robust and useful tool for simulating catalytic entrained-flow gasification of biomass-based feedstocks. / LTU Biosyngas (Catalytic Gasification)

Mit Hilfe eines variabel einsetzbaren Reaktornetzwerkmodells (RNM) wird in der vorliegenden Dissertation der Prozess der Vergasung von Brennstoffmischungen in der Fließbildsimulation beschrieben. Neben der Untersuchung von gestuften Prozessketten zur Veredelung von kohlenstoffhaltigen Energieträgern ist damit auch die differenzierte Analyse von Effekten während der Vergasung von binären und ternären Brennstoffmischungen möglich. Die Erstellung sowie Validierung des RNM wird anhand des PEFR-Vergasers, des SFGT-Vergasers und des Hybridwandvergaser vorgenommen. Die anschließende Analyse der Vergasung von Brennstoffmischungen zeigt, dass in ihren Eigenschaften sehr heterogene Brenn¬stoffmischungen Synergieeffekte bei der Vergasung hervorrufen. Diese sind in der Literatur schon oft beschrieben worden, eine systematische Analyse wird jedoch erst in der vorliegenden Dissertation durchgeführt. / Within this document the modeling and simulation of fuel blend gasification is investigated based on a variably applicable Reduced Order Model (ROM) developed for the flowsheet simulation of entrained-flow gasification reactors and processes. On one hand this enables the investigation of cascaded solid fuel conversion technologies and on the other hand effects during gasification of binary and ternary fuel blends are describable. The development as well as the validation of the ROM has been carried out for the SFGT gasifier, the PEFR gasifier and the hybrid-wall gasifier. The subsequent analysis of binary and ternary fuel blend gasification shows that fuel blends with very heterogeneous component properties induce synergy effects which have been reported in various peer review publications.

Mit Hilfe eines variabel einsetzbaren Reaktornetzwerkmodells (RNM) wird in der vorliegenden Dissertation der Prozess der Vergasung von Brennstoffmischungen in der Fließbildsimulation beschrieben. Neben der Untersuchung von gestuften Prozessketten zur Veredelung von kohlenstoffhaltigen Energieträgern ist damit auch die differenzierte Analyse von Effekten während der Vergasung von binären und ternären Brennstoffmischungen möglich. Die Erstellung sowie Validierung des RNM wird anhand des PEFR-Vergasers, des SFGT-Vergasers und des Hybridwandvergaser vorgenommen. Die anschließende Analyse der Vergasung von Brennstoffmischungen zeigt, dass in ihren Eigenschaften sehr heterogene Brenn¬stoffmischungen Synergieeffekte bei der Vergasung hervorrufen. Diese sind in der Literatur schon oft beschrieben worden, eine systematische Analyse wird jedoch erst in der vorliegenden Dissertation durchgeführt.:Nomenklatur XIV 1 Einleitung 1 2 Grundlagen 3 2.1 VERGASUNG 3 2.1.1 Vergasungsreaktionen 3 2.1.2 Vergasungskennzahlen 4 2.1.3 Modellierung der Vergasung 6 2.2 CO-VERGASUNG 8 2.2.1 Brennstoffe 8 2.2.2 Großtechnische Anwendung 8 2.2.3 Experimentelle Arbeiten 10 2.2.4 Modellierung und Simulation 13 2.2.5 Synergieeffekte 13 2.3 STOFFGEFÜHRTE PROZESSKETTE 15 2.4 BRENNSTOFFAUSWAHL UND BRENNSTOFFEIGENSCHAFTEN 16 2.5 ABLEITUNG DER AUFGABENSTELLUNG UND METHODIK 19 3 Entwicklung des Reaktornetzwerkmodells 22 3.1 MODELLIERUNGSUMGEBUNG 23 3.2 THERMODYNAMISCHE ZUSTANDSGLEICHUNG 23 3.3 STOFFDATENBANK 24 3.4 STRÖMUNGSBEDINGUNGEN IM FLUGSTROMREAKTOR 25 3.4.1 Zonenmodell 25 3.4.2 Verweilzeitverhalten 29 3.5 PARTIKELMODELL 31 3.6 MODELLIERUNG DER REAKTORZONEN 35 3.6.1 Nahbrennerzone (Zone I) 35 3.6.2 Jetzone (Zone II) 36 3.6.3 Rezirkulationszone (Zone III) 41 3.6.4 Auslaufzone (Zone IV) 41 3.6.5 Wasserquench (Zone V) 41 3.7 REGELMECHANISMEN 42 3.7.1 Regelung der Aschefließtemperatur 42 3.7.2 Regelung des Kohlenstoffumsatzgrades 46 3.7.3 Regelung der maximalen Reaktoraustrittstemperatur 47 3.7.4 Kombinierte Regelung 47 3.8 LÖSUNGSALGORITHMEN UND KONVERGENZVERHALTEN 48 4 Validierung des Reaktornetzwerkmodells 51 4.1 REAKTORNETZWERKMODELL PEFR-VERGASER 51 4.1.1 Aufbau des PEFR-RNM 51 4.1.2 Validierung des PEFR-RNM 54 4.2 REAKTORNETZWERKMODELL SFGT-VERGASER 61 4.2.1 Aufbau des SFGT-RNM 61 4.2.2 Validierung des SFGT-RNM 62 4.3 REAKTORNETZWERKMODELL HYBRIDWANDVERGASER 74 4.3.1 Beschreibung der Technologie Hybridwandvergaser 74 4.3.2 Aufbau des Hybridwandvergaser-RNM 75 4.3.3 Validierung des Hybridwandvergaser-RNM 78 5 RNM-Analyse der Vergasung von Brennstoffmischungen 85 5.1 VORÜBERLEGUNGEN 85 5.1.1 Festlegung der Randbedingungen 85 5.1.2 Thermische Vergaserleistung 86 5.1.3 Simulationsdauer und Automatisierung 87 5.2 AUSWERTUNG DER RNM-ANALYSE VON BRENNSTOFFMISCHUNGEN 89 5.2.1 RNM-Analyse BSM-BRP (binär) im SFGT-Vergaser 89 5.2.2 RNM-Analyse BSM-BRP (ternär) im SFGT-Vergaser 95 5.2.3 RNM-Analyse BSM-ibi (binär) im SFGT-Vergaser 100 5.2.4 RNM-Analyse BSM-ibi (ternär) im SFGT-Vergaser 102 5.3 DISKUSSION DER ERGEBNISSE AUS RNM-ANALYSE 106 5.4 BSM-DIAGRAMME FÜR VERGASERBETRIEB 109 5.4.1 BSM-Diagramme für SFGT-Vergaser 109 5.4.2 BSM-Diagramme für Hybridwandvergaser 112 6 Zusammenfassung und Ausblick 117 Literatur 121 Abbildungsverzeichnis 133 Tabellenverzeichnis 141 Anhang 145 / Within this document the modeling and simulation of fuel blend gasification is investigated based on a variably applicable Reduced Order Model (ROM) developed for the flowsheet simulation of entrained-flow gasification reactors and processes. On one hand this enables the investigation of cascaded solid fuel conversion technologies and on the other hand effects during gasification of binary and ternary fuel blends are describable. The development as well as the validation of the ROM has been carried out for the SFGT gasifier, the PEFR gasifier and the hybrid-wall gasifier. The subsequent analysis of binary and ternary fuel blend gasification shows that fuel blends with very heterogeneous component properties induce synergy effects which have been reported in various peer review publications.:Nomenklatur XIV 1 Einleitung 1 2 Grundlagen 3 2.1 VERGASUNG 3 2.1.1 Vergasungsreaktionen 3 2.1.2 Vergasungskennzahlen 4 2.1.3 Modellierung der Vergasung 6 2.2 CO-VERGASUNG 8 2.2.1 Brennstoffe 8 2.2.2 Großtechnische Anwendung 8 2.2.3 Experimentelle Arbeiten 10 2.2.4 Modellierung und Simulation 13 2.2.5 Synergieeffekte 13 2.3 STOFFGEFÜHRTE PROZESSKETTE 15 2.4 BRENNSTOFFAUSWAHL UND BRENNSTOFFEIGENSCHAFTEN 16 2.5 ABLEITUNG DER AUFGABENSTELLUNG UND METHODIK 19 3 Entwicklung des Reaktornetzwerkmodells 22 3.1 MODELLIERUNGSUMGEBUNG 23 3.2 THERMODYNAMISCHE ZUSTANDSGLEICHUNG 23 3.3 STOFFDATENBANK 24 3.4 STRÖMUNGSBEDINGUNGEN IM FLUGSTROMREAKTOR 25 3.4.1 Zonenmodell 25 3.4.2 Verweilzeitverhalten 29 3.5 PARTIKELMODELL 31 3.6 MODELLIERUNG DER REAKTORZONEN 35 3.6.1 Nahbrennerzone (Zone I) 35 3.6.2 Jetzone (Zone II) 36 3.6.3 Rezirkulationszone (Zone III) 41 3.6.4 Auslaufzone (Zone IV) 41 3.6.5 Wasserquench (Zone V) 41 3.7 REGELMECHANISMEN 42 3.7.1 Regelung der Aschefließtemperatur 42 3.7.2 Regelung des Kohlenstoffumsatzgrades 46 3.7.3 Regelung der maximalen Reaktoraustrittstemperatur 47 3.7.4 Kombinierte Regelung 47 3.8 LÖSUNGSALGORITHMEN UND KONVERGENZVERHALTEN 48 4 Validierung des Reaktornetzwerkmodells 51 4.1 REAKTORNETZWERKMODELL PEFR-VERGASER 51 4.1.1 Aufbau des PEFR-RNM 51 4.1.2 Validierung des PEFR-RNM 54 4.2 REAKTORNETZWERKMODELL SFGT-VERGASER 61 4.2.1 Aufbau des SFGT-RNM 61 4.2.2 Validierung des SFGT-RNM 62 4.3 REAKTORNETZWERKMODELL HYBRIDWANDVERGASER 74 4.3.1 Beschreibung der Technologie Hybridwandvergaser 74 4.3.2 Aufbau des Hybridwandvergaser-RNM 75 4.3.3 Validierung des Hybridwandvergaser-RNM 78 5 RNM-Analyse der Vergasung von Brennstoffmischungen 85 5.1 VORÜBERLEGUNGEN 85 5.1.1 Festlegung der Randbedingungen 85 5.1.2 Thermische Vergaserleistung 86 5.1.3 Simulationsdauer und Automatisierung 87 5.2 AUSWERTUNG DER RNM-ANALYSE VON BRENNSTOFFMISCHUNGEN 89 5.2.1 RNM-Analyse BSM-BRP (binär) im SFGT-Vergaser 89 5.2.2 RNM-Analyse BSM-BRP (ternär) im SFGT-Vergaser 95 5.2.3 RNM-Analyse BSM-ibi (binär) im SFGT-Vergaser 100 5.2.4 RNM-Analyse BSM-ibi (ternär) im SFGT-Vergaser 102 5.3 DISKUSSION DER ERGEBNISSE AUS RNM-ANALYSE 106 5.4 BSM-DIAGRAMME FÜR VERGASERBETRIEB 109 5.4.1 BSM-Diagramme für SFGT-Vergaser 109 5.4.2 BSM-Diagramme für Hybridwandvergaser 112 6 Zusammenfassung und Ausblick 117 Literatur 121 Abbildungsverzeichnis 133 Tabellenverzeichnis 141 Anhang 145