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Untersuchungsgegenstand der vorliegenden Dissertation sind biomassebasierte Kohlen (Biokohlen, biochar), welche für eine langfristige Kohlenstoffspeicherung in Böden mit dem gleichzeitigen Ziel der zusätzlichen Bodenverbesserung hergestellt werden. Die Auswahl der Kohlen umfasste Kohlen aus Pyrolyse- und hydrothermale Carbonisierung (HTC). In dieser Arbeit werden einige zentrale Phänomene, die bei deren Ausbringung in einem bestehenden Bodenökosystem auftreten können, nähergehend untersucht. Einerseits beeinflusst das fremde Material den Stoffwechsel und die Abundanz und Vielfalt innerhalb der mirkobiellen Gemeinschaft im Boden; im Gegenzug spielen die Mikroorganismen eine aktive Rolle beim Abbau des neuen Substrats. Diese beiden Aspekte sind größer Bedeutung, um bewerten zu können, wie erfolgsversprechend der Einsatz einer bestimmten Kohle im Boden hinsichtlich der Langlebigkeit, der gewünschten Ertragseffekte sowie möglicher Nebenwirkungen ist. Daraus ergeben sich die beiden folgenden zwei Fragestellungen, auf die diese Arbeit fokusiert ist: • Welche Faktoren beeinflussen die Abbaubarkeit der Kohlen im Boden? • Welche Wirkungen haben die Kohlen auf die Bodenatmung, auf den Boden-C-Gehalt, auf die mikrobielle Abundanz und auf die Dynamik der mikrobiellen Gemeinschaft? Als mögliche Einflussgrößen für die Abbaubarkeit der Kohlen wurden die Art der Kohlenherstellung, eine mögliche Nachbehandlung, der Alterungsprozess sowie die Zugabe einer Nährstoff- und einer labilen Kohlenstoffquelle getestet. Für diese Studie wurden Pyrolyse- und HTC-Kohlen aus Mais-Silage in einen Sandboden ausgebracht. Grundlage aller Versuche war die Untersuchung der Respirationsdynamik in unterschiedlichen Boden-Kohle-Gemischen, die durch Infrarotspektrometrie ermittelt wurde. Sie diente als Indikator für die mikrobielle Aktivität und dem daraus resultierenden Abbau der Substrate. Ergänzend wurde am Anfang und am Ende jedes Versuchs der Boden-Kohlenstoffgehalt gemessen. Die Versuche erfolgten auf verschiedenen Skalen: • Kurzzeit-Laborinkubationen (10 Tage) unter konstanten klimatischen Bedingungen in einem automatisch gesteuerten Durchflusssystem, an das das Messgerät direkt angeschlossen wurde. • Parzellenversuch (2 Jahre) im Freiland im Nordwesten Brandenburgs, bei dem die Bestimmung der Bodenatmung mittels wiederholter Beprobung aus auf der Ackerfläche gestellten geschlossenen Hauben erfolgte. In einer Laborinkubation wurde zusätzlich eine qPCR (quantitative Echtzeit Polymerase Kettenreaktion) zur Bestimmung der Abundanz ausgewählter mikrobieller Gruppen eingesetzt. Im Feldversuch wurde außerdem die Abundanz der stabilen Kohlenstoff-Isotopen (12C und 13C) im Boden und im freigesetzten CO2 ermittelt, um den Abbau der Kohlen vom Abbau des bodenorganischen Kohlenstoffs, der durch die Kohlen beeinflusst sein kann (priming), zu unterscheiden. Die Ergebnisse bestätigen die erhöhte Stabilität beider Kohlen im Vergleich zum Ausgangsmaterial, vor allem für die Pyrolyse-Kohle, deren Abbau sowohl im Labor als auch im Freiland am langsamsten erfolgte. Bei beiden Kohlen sank die Abbaubarkeit mit ihrer Alterung. Anhand der Abbauraten im zweiten Jahr des Feldversuchs wurden für die Pyrolyse- und HTC-Kohle Halbwertszeiten von 81 bzw. 60 Jahren ermittelt. Im Gegensatz zur Pyrolyse-Kohle wies der Abbau der HTC-Kohle eine komplexere Dynamik auf, was im Lauf der 10-tägigen Inkubationsversuche mit einer Verschiebung der mikrobiellen Gemeinschaft einherging. Im ersten Jahr des Freilandversuchs kam es bei der HTC-Kohle zur Ausgasung flüchtiger und leicht abbaubarer Kohlenstoffverbindungen, wodurch die Stabilität im Folgejahr deutlich erhöht wurde. Eine Nachbehandlung der Kohlen durch anaerobe Fermentierung führte zu einer deutlichen Verminderung der kurzzeitigen Ausgasung bei HTC-Kohle, sowohl im Freiland als auch im Labor, jedoch zu einer langfristigen Reduktion der Stabilität beider Kohlen: die ermittelten Halbwertszeiten für die fermentierte Pyrolyse- und HTC-Kohle nach dem zweiten Jahr des Feldversuchs betrugen 14 bzw. 13 Jahren. Die Wirkung der unbehandelten Kohlen auf die Abundanz der untersuchten mikrobiellen Gruppen im C-armen Boden war stark reduziert im Vergleich zum Ausgangsmaterial, und unter C-reichen Bedingungen kam es zu einer Hemmung der Aktivitätssteigerung. Die Zugabe leicht verfügbaren Kohlenstoffs wie Glukose zum reinen Boden in einem Inkubationsversuch steigerte die Bodenatmung erheblich und erhöhte die Variationsbreite der mikrobiellen Gemeinschaft. In Gegenwart der Kohlen war dies allerdings weniger stark ausgeprägt. Bei Zugabe mineralischen Stickstoffs in Gegenwart von Kohlen wurde hingegen keine signifikante Veränderung der Bodenatmung nachgewiesen. Die Inkubationsversuche haben es ermöglicht, die Kurzzeitdynamik der Bodenatmung und die Anpassung der mikrobiellen Gemeinschaft nach Zugabe der Kohlen und zusätzlicher C- und N-Quellen nachzuweisen. Im Freilandversuch konnte die Abbaudynamik von Kohlenstoffverbindungen unter Praxisbedingungen untersucht werden und durch die Messung der stabilen Isotope differenzierte Aussagen über die langfristige Stabilität von zugesetzten Kohlen und der bodenorganischen Substanz getroffen werden. Eine langfristige Festlegung von Kohlenstoff ist im Boden in Form von Biokohlen ist möglich. Allerdings hängt die Dauer der Festlegung von einer Vielzahl von Faktoren wie der Art der Ausgangsstoffe, den Prozessbedingungen, den Interaktionen zwischen Kohlepartikeln und Bodenorganismen und nicht zuletzt der Versuchsdauer ab. Während Kurzzeitversuche eine gute Möglichkeit darstellen, um die Effekte veränderter Bedingungen im Boden aufzuzeigen, kann die Kohlestabilität im Boden und damit das C-Sequestrierungspotenzial am zuverlässigsten nur in Langzeitstudien im Freiland abgeschätzt werden. / The object of the present thesis is charred biomass (biochar) produced for double aim of carbon storage in soil and improvement of soil properties. The chosen chars included chars from pyrolysis and hydrothermal carbonisation (HTC). The present work investigates closely some basic phenomena which can occur upon application of chars into an existing soil ecosystem: on the one hand, the allochthonous material affects the metabolism and the relative abundance of different microbial groups; on the other hand the microorganisms play an active role in the degradation of the new substrate. These two aspects are crucial to evaluate the suitability of the application of a specific char in the soil, particularly as concerns its stability, the length of time the char remains in the soil, the expected effects on crop yields, as well as possible side effects on the soil ecosystem. Based on this, two research questions arise which have been investigated in this thesis: • What factors affect the degradability of chars in soil? • How do the chars influence soil respiration, soil carbon content, microbial abundance and the dynamics of the microbial community? The production process, a post-treatment, the ageing process as well as the addition of a source of nutrients and a source of labile carbon were assessed as possible factors in determining the degradability of chars. For the present study, pyrolysis char and HTC char from maize silage were applied to a sandy soil. The basis of all experiments was an investigation of the respiration dynamics in different soil/char mixtures, measured through an infrared spectrometer, which was used to track the microbial activity and the substrate degradation. As a complement, soil carbon was also measured at the beginning and at the end of each experiment. The investigations were performed at different scales: • Short-term laboratory incubations (10 days) under constant climatic conditions in an automatic multi-channel flowthrough system, with direct plug-in for the measurement instrument. • A plot-wise investigation (2 years) in an agricultural field in North-West Brandenburg, where the soil respiration was measured by a repeated sampling from static chambers placed hermetically on the field. For one incubation study, qPCR (qunatitative real time polymerase chain reaction) was additionally applied to determine the abundance of selected microbial groups. Moreover, for the field investigation the abundance of stable carbon isotopes (12C und 13C) in the soil and in the released CO2 was recorded, to differentiate between the degradation of the chars and the degradation of soil organic carbon, which might be affected by the presence of chars (priming). The results confirm the higher stability of both chars in comparison to the feedstock, in particular for pyrolysis char, whose decay was the slowest both in the laboratory and in the field. The degradability of both chars decreased with their ageing. Based on the decay rates in the second year of the field investigation, decay half-lives for pyrolysis char and HTC char amounted respectively to 81 years and 60 years. Other than pyrolysis char, the degradation of HTC char revealed a more complex dynamics, which was accompanied by a shift of the microbial community within the 10 days incubation. During the first year of the field experiment, an intensive release of volatile and labile compounds took place, which led to an increased stability during the following year. A post-treatment of the chars via anaerobic fermentation led to a reduction in the initial degasing of the HTC char, both in the laboratory and in the field, but also to a decrease in stability for both chars: the calculated half-lives for fermented pyrolysis char and fermented HTC char on the basis of the second year of the field investigation were respectively 14 years and 13 years. The effects of the untreated chars on the abundance of the selected microbial groups in the carbon-poor soil used was also strongly reduced in comparison to the feedstock, while in a situation of carbon abundance a inhibition of the activity increase took place. Addition of readily available carbon in the form of glucose increased soil respiration tremendously and magnified the variation amplitude of the microbial community, which was however much reduced in the presence of chars. Instead, after addition of mineral nitrogen in presence of chars, no significant variation in the soil respiration could be observed. The incubation experiments made it possible to report the short-term dynamics of the soil respiration and the adaptation of the microbial community after application of char and additional carbon and nitrogen sources. In the field experiment the decay dynamics of char compounds could be investigated in a situation of common agricultural practice and the measurement of stable isotopes has given differentiated outcomes about the long-term stability of the added chars and of the soil organic matter. Storage of carbon in the soil in the form of char for a long period is possible. How long carbon can actually be stored depends on a number of factors such as the feedstock, the carbonisation process parameters, the interactions between char particles and soil microorganisms and the duration of the investigation itself. Short-term experiments represent a good possibility to highlight the effects of modified soil conditions, while the stability of char in soil and thus the potential carbon sequestration can be estimate in the most reliable way only through long-term studies in field. / Oggetto della presente tesi sono i carboni prodotti da biomasse (biochar) e utilizzati per lo stoccaggio del carbonio nel suolo e allo stesso tempo come ammendanti per terreni agricoli. I carboni considerati sono derivati da pirolisi o carbonizzazione idrotermale (HTC). Nel presente lavoro vengono esaminati in dettaglio alcuni importanti fenomeni che si possono manifestare in seguito all’applicazione su un ecosistema preesistente nel terreno: da un lato il materiale estraneo influenza il metabolismo della materia organica, l’abbondanza e la varietà all’interno della comunità microbica nel suolo, dall’altro i microorganismi giocano un ruolo fondamentale nella degradazione del nuovo substrato. Questi due aspetti sono essenziali per valutare quanto sia opportuno l’utilizzo di un determinato carbone dal punto di vista della sua longevità, degli effetti attesi sulla resa agricola e di eventuali effetti collaterali sull’ecosistema. Da queste premesse sono emerse le seguenti domande, su cui è focalizzato il presente lavoro: • Quali fattori determinano la degradabilità dei carboni nel suolo? • Che effetti possono avere i carboni sulla respirazione del terreno, sul suo contenuto di carbonio, sull’abbondanza dei microorganismi e sulla dinamica della comunità microbica? Come possibili variabili indipendenti per la degradabilità dei carboni sono state considerate: il processo di produzione, un possibile posttrattamento, l’invecchiamento dei substrati, l’aggiunta di nutrienti e di carbonio biodisponibile. Per questo studio sono stati applicati carboni derivati da pirolisi e da HTC di insilato di mais in un terreno sabbioso. Il fondamento di tutti gli esperimenti riportati è lo studio della dinamica della respirazione microbica in diverse miscele terreno/carbone, misurata tramite spettroscopia a infrarossi, che vale come tracciante per l’attività microbica e per la degradazione del substrato. In aggiunta è stato periodicamente misurato il contenuto di carbonio nel terreno. Gli esperimenti sono stati condotti su due diverse scale: • Incubazioni in laboratorio (10 giorni) in condizioni climatiche controllate, all’interno di un apparato per la ventilazione a flusso continuo, con presa diretta per lo strumento di misura. • Esperimento in campo parcellizzato (2 anni) nel Brandeburgo nordoccidentale, dove la misura della respirazione è avvenuta per campionamento ripetuto da camere opache poggianti ermeticamente sul suolo. Per una delle incubazioni è stata anche eseguita una qPCR (reazione a catena della polimerasi quantitativa in tempo reale) per quantificare l’abbondanza di determinati gruppi tassonomici di microorganismi. Nel campo è stata inoltre misurata l’abbondanza degli isotopi stabili del carbonio (12C e 13C), sia nel terreno sia nella CO2 liberata, per differenziare la degradazione dei carboni da quella del carbonio organico nel suolo, che in principio può essere influenzata dalla presenza dei carboni (priming). I risultati confermano l’aumentata stabilità di entrambi i carboni in confronto al materiale di partenza, in particolare del carbone pirolitico che si è degradato piú lentamente, sia in laboratorio sia in campo. La degradabilità di entrambi i carboni si è in ogni caso ridotta con l’invecchiamento. Basandosi sulle emissioni del secondo anno della sperimentazione in campo, sono stati calcolati dei tempi di dimezzamento di 81 anni e 60 anni, rispettivamente per il carbone pirolitico e per il carbone da HTC. La degradazione del carbone da HTC ha rivelato una dinamica piú complessa, che testimonia un adattamento della comunità microbica nell’arco dei 10 giorni di incubazione. Nel primo anno in campo è stata rilevata un’elevata emissione di composti volatili e labili, che ha portato a un incremento della stabilità nell’anno seguente. Il posttrattamento dei carboni tramite fermentazione anaerobica ha comportato una notevole riduzione dell’iniziale mineralizzazione del carbone da HTC, ma una diminuzione della stabilità di entrambi i carboni sul lungo periodo: i tempi di dimezzamento calcolati per il carbone pirolitico fermentato e per il carbone da HTC fermentato nel secondo anno dell’esperimento sul campo valgono rispettivamente 14 anni e 13 anni. Nel terreno usato, povero di carbonio, gli effetti dei carboni sull’abbondanza dei gruppi microbici selezionati è stata nettamente ridotta rispetto al materiale non carbonizzato, mentre la reazione all’aggiunta di carbonio labile è stata tendenzialmente inibitoria. Infatti, se l’aggiunta di glucosio ha incrementato considerevolmente la respirazione e l’ampiezza delle variazioni nella comunità microbica, in presenza dei carboni le variazioni sono state fortemente ridotte. L’aggiunta di azoto inorganico non ha invece portato a variazioni apprezzabili nella respirazione. Gli esperimenti basati su incubazioni hanno consentito di determinare la dinamica a breve termine della respirazione e l’adattamento della comunità microbica in seguito ad aggiunta dei carboni e di altre sorgenti di carbonio e azoto. Nell’esperimento su campo si è potuta osservare la dinamica di degradazione dei composti carboniosi in condizioni di prassi agricola e grazie alla misura degli isotopi stabili si sono potuti ottenere risultati differenziati sulla stabilità a lungo termine dei carboni e della sostanza organica del suolo. È quindi possibile immagazzinare il carbonio in modo duraturo nel suolo sotto forma di carbone. La durata stimabile di questo immagazzinamento dipende però da molteplici fattori tra cui la materia prima, il processo di carbonizzazione, le interazioni tra particelle carboniose e microorganismi del suolo e non da ultimo la durata della sperimentazione. Gli esperimenti a breve termine sono un mezzo efficace per rilevare le conseguenze immediate di modifiche del terreno; la stabilità dei carboni e quindi il loro potenziale per il sequestro del carbonio può essere determinata nel modo piú affidabile solo in studi a lungo termine sul campo.

With the increasing global energy demand and the decreasing availability of good quality coals, a better understanding of the important properties that control the behaviour of low–grade coals and the subsequent chars in various utilisation processes, becomes pertinent. An investigation was therefore undertaken, to study the effects of chemical and physical properties imparted on chars during pyrolysis on the subsequent gasification reaction kinetics of typical South African inertinite–rich, high ash Highveld coals. An attempt was made at following these changes in the transition from coals to chars by a detailed characterisation of both the parent coals and the respective chars. These changes were determined using various conventional and advanced techniques, which included among others, carbon crystallite analysis using XRD and char carbon forms analysis using petrography. Three of the four original coals were characterised as Bituminous Medium rank C (coals B, C and C2), while coal D2 was found to be slightly lower in rank (Bituminous Medium rank D). The coals were rich in inertinites (> 54 vol. %, mmb with coal C2 having as high as 79 vol. %, mmb) and high in ash content (> 26.7 wt. %, db) and cabominerite and minerite contents (26 – 39 vol. %, mmb). The inertinitevitrinite ratios of the coals were found to range from 1.93 to 26.3. Characterization results show that both volatile matter and inherent moisture content decreased, while ash, fixed carbon and elemental carbon contents increased from coals to chars, indicating that the pyrolysis process was efficient. Elemental hydrogen, oxygen and nitrogen contents decreased, whereas total sulphur contents increased from coals to chars. This reveals that the total sulphur contained in the char samples was associated with the char carbon matrix and the minerals. Hydrogen–carbon and oxygen–carbon ratios decreased considerably from coals to chars showing that the chars are more aromatic and denser products than the original coals. Despite the fact that mineral matter increased from coals to chars, the relative abundance of the different mineral phases and ash components did not exhibit significant variation amongst the samples. The alkali index was, however, found to vary considerably among the subsequent chars. Petrographic analysis of the coals and char carbon forms analysis of the chars reveal that total reactive components (TRC) decrease while the total inert components (TIC) increase from coals to chars. The 0% gain in TIC observed in char C2 was attributed to its relatively high partially reacted maceral char carbon forms content. Total maceral reflectance shifted to higher values in the chars (4.43 – 5.28 Rsc%) relative to the coals (1.15 – 1.63 Rsc%) suggesting a higher structural ordering in the chars. Carbon crystallite analyses revealed that the chars were condensed (smaller in size) relative to the parent coals. Lattice parameters: interlayer spacing, d002, increased, while the average crystallite height, Lc, crystallite diameter, La, and number of aromatic layers per crystallite, Nave, decreased from coals to chars. Carbon aromaticity generally increased whereas the fraction of amorphous carbon and the degree of disorder index decreased from parent coals to the respective chars. Both micropore surface area and microporosity were observed to increase while the average micropore diameter decreased from coals to chars. This shows that blind and closed micropores were “opened up” during the charring process. Despite the original coal samples not showing much variation in their properties (except for their maceral content), it was generally observed that the subsequent chars exhibited substantial differences, both amongst themselves and from the parent coals. The increasing orders of magnitude of micropore surface area, microporosity, fraction of amorphous carbon and structural disorderliness were found to change in the transition, a good indication that the chars’ properties varied from that of the respective parent coals. Isothermal CO2 gasification experiments were conducted on the chars in a Thermax 500 thermogravimetric analyser in the temperature range of 900 – 950 °C with varying concentrations of CO2 (25 – 100 mol. %) in the CO2–N2 reaction gas mixture at ambient pressure (0.875 bar in Potchefstroom). The effects of temperature and CO2 concentration were observed to be in conformity with established trends. The initial reactivity of the chars was found to increase in the order: chars C2 < C < B < D2, with char D2 reactivity greater than the reactivity of the other chars by a factor > 4. Gasification reactivity results were correlated with properties of the parent coals and chars. Except for the rank parameter (the vitrinite reflectance), no significant trend was observed with any other coal petrographic property. Correlations with char properties gave more significant and systematic trends. Major factors affecting the gasification reactivity of the chars as it pertains to this investigation are: parent coal vitrinite reflectance, and: aromaticity, fraction of amorphous carbon, degree of disorder and alkali indices, micropore surface area, microporosity and average micropore diameter of the chars. The random pore model (chemical reaction controlling) was found to adequately describe the gasification reaction experimental data (both conversions and conversion rates). The determined activation energy ranged from 163.3 kJ·mol–1 for char D2 to 235.7 kJ·mol–1 for char B; while the order of reaction with respect to CO2 concentration ranged between 0.52 to 0.67 for the four chars. The lower activation energy of char D2 was possibly due to its lower rank, lower coal vitrinite reflectance and higher alkali index. The estimated kinetic parameters of the chars in this study correspond very well with published results in open literature. It was possible to express the intrinsic reactivity, rs, of the chars (rate of carbon conversion per unit total surface area) using kinetic results, in empirical Arrhenius forms. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

With the increasing global energy demand and the decreasing availability of good quality coals, a better understanding of the important properties that control the behaviour of low–grade coals and the subsequent chars in various utilisation processes, becomes pertinent. An investigation was therefore undertaken, to study the effects of chemical and physical properties imparted on chars during pyrolysis on the subsequent gasification reaction kinetics of typical South African inertinite–rich, high ash Highveld coals. An attempt was made at following these changes in the transition from coals to chars by a detailed characterisation of both the parent coals and the respective chars. These changes were determined using various conventional and advanced techniques, which included among others, carbon crystallite analysis using XRD and char carbon forms analysis using petrography. Three of the four original coals were characterised as Bituminous Medium rank C (coals B, C and C2), while coal D2 was found to be slightly lower in rank (Bituminous Medium rank D). The coals were rich in inertinites (> 54 vol. %, mmb with coal C2 having as high as 79 vol. %, mmb) and high in ash content (> 26.7 wt. %, db) and cabominerite and minerite contents (26 – 39 vol. %, mmb). The inertinitevitrinite ratios of the coals were found to range from 1.93 to 26.3. Characterization results show that both volatile matter and inherent moisture content decreased, while ash, fixed carbon and elemental carbon contents increased from coals to chars, indicating that the pyrolysis process was efficient. Elemental hydrogen, oxygen and nitrogen contents decreased, whereas total sulphur contents increased from coals to chars. This reveals that the total sulphur contained in the char samples was associated with the char carbon matrix and the minerals. Hydrogen–carbon and oxygen–carbon ratios decreased considerably from coals to chars showing that the chars are more aromatic and denser products than the original coals. Despite the fact that mineral matter increased from coals to chars, the relative abundance of the different mineral phases and ash components did not exhibit significant variation amongst the samples. The alkali index was, however, found to vary considerably among the subsequent chars. Petrographic analysis of the coals and char carbon forms analysis of the chars reveal that total reactive components (TRC) decrease while the total inert components (TIC) increase from coals to chars. The 0% gain in TIC observed in char C2 was attributed to its relatively high partially reacted maceral char carbon forms content. Total maceral reflectance shifted to higher values in the chars (4.43 – 5.28 Rsc%) relative to the coals (1.15 – 1.63 Rsc%) suggesting a higher structural ordering in the chars. Carbon crystallite analyses revealed that the chars were condensed (smaller in size) relative to the parent coals. Lattice parameters: interlayer spacing, d002, increased, while the average crystallite height, Lc, crystallite diameter, La, and number of aromatic layers per crystallite, Nave, decreased from coals to chars. Carbon aromaticity generally increased whereas the fraction of amorphous carbon and the degree of disorder index decreased from parent coals to the respective chars. Both micropore surface area and microporosity were observed to increase while the average micropore diameter decreased from coals to chars. This shows that blind and closed micropores were “opened up” during the charring process. Despite the original coal samples not showing much variation in their properties (except for their maceral content), it was generally observed that the subsequent chars exhibited substantial differences, both amongst themselves and from the parent coals. The increasing orders of magnitude of micropore surface area, microporosity, fraction of amorphous carbon and structural disorderliness were found to change in the transition, a good indication that the chars’ properties varied from that of the respective parent coals. Isothermal CO2 gasification experiments were conducted on the chars in a Thermax 500 thermogravimetric analyser in the temperature range of 900 – 950 °C with varying concentrations of CO2 (25 – 100 mol. %) in the CO2–N2 reaction gas mixture at ambient pressure (0.875 bar in Potchefstroom). The effects of temperature and CO2 concentration were observed to be in conformity with established trends. The initial reactivity of the chars was found to increase in the order: chars C2 < C < B < D2, with char D2 reactivity greater than the reactivity of the other chars by a factor > 4. Gasification reactivity results were correlated with properties of the parent coals and chars. Except for the rank parameter (the vitrinite reflectance), no significant trend was observed with any other coal petrographic property. Correlations with char properties gave more significant and systematic trends. Major factors affecting the gasification reactivity of the chars as it pertains to this investigation are: parent coal vitrinite reflectance, and: aromaticity, fraction of amorphous carbon, degree of disorder and alkali indices, micropore surface area, microporosity and average micropore diameter of the chars. The random pore model (chemical reaction controlling) was found to adequately describe the gasification reaction experimental data (both conversions and conversion rates). The determined activation energy ranged from 163.3 kJ·mol–1 for char D2 to 235.7 kJ·mol–1 for char B; while the order of reaction with respect to CO2 concentration ranged between 0.52 to 0.67 for the four chars. The lower activation energy of char D2 was possibly due to its lower rank, lower coal vitrinite reflectance and higher alkali index. The estimated kinetic parameters of the chars in this study correspond very well with published results in open literature. It was possible to express the intrinsic reactivity, rs, of the chars (rate of carbon conversion per unit total surface area) using kinetic results, in empirical Arrhenius forms. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

An investigation was undertaken to compare the kinetics of combustion and gasification reactions of chars prepared from two South African coals in different reaction atmospheres: air, steam, and carbon dioxide. The two original coals were characterised as vitrinite-rich (Greenside) and inertinite-rich (Inyanda) coals with relatively low ash content (12.5-16.7 wt. %, adb). Chars were prepared from the parent coals under nitrogen atmosphere at 900 °C. Characterisation results show that the volatiles and moisture were almost completely driven off from the parent coals, indicating that the pyrolysis process was efficient. Physicalstructural properties such as porosity and surface area generally increased from the parent coals to the subsequent chars. The heterogeneous char-gas reactions were conducted isothermally in a TGA on ~1 mm size particles. To ensure that the reactions are under chemical reaction kinetic control regime, different temperatures zones were selected for the three different reaction atmospheres. Combustion reactivity experiments were carried out with air in the temperature range of 387 °C to 425 °C; gasification reactivity with pure steam were conducted at higher temperatures (775 °C - 850 °C) and within 825 °C to 900 °C with carbon dioxide. Experimental results show differences in the specific reaction rate with carbon conversion in different reaction atmospheres and char types. Reaction rates in all three reaction atmospheres were strongly dependent on temperature, and follow the Arrhenius type kinetics. All the investigated reactions (combustion with air and gasification with CO2 and steam) were found to be under chemical reaction control regime (Regime I) for both chars. The inertinite-rich coals exhibit longer burn-out time than chars produced from vitrinite-rich coals, as higher specific reaction rate were observed for the vitrinite-rich coals in the three different reaction atmospheres. The determined random pore model (RPM) structural parameters did not show any significant difference during steam gasification of Greenside and Inyanda chars, whereas higher structural parameter values were observed for Greenside chars during air combustion and CO2 gasification (ψ > 2). However a negative ψ value was determined during CO2 gasification and air combustion of Inyanda chars. The RPM predictions was validated with the experimental data and exhibited adequate fitting to the specific rate of reaction versus carbon conversion plots of the char samples at the different reaction conditions chosen for this study. The activation energy determined was minimal for air and maximum for CO2 for both coals; and ranged from 127-175 kJ·mol-1 for combustion, 214-228 kJ·mol-1 and 210-240 kJ·mol-1 for steam and CO2 gasification respectively. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

An investigation was undertaken to compare the kinetics of combustion and gasification reactions of chars prepared from two South African coals in different reaction atmospheres: air, steam, and carbon dioxide. The two original coals were characterised as vitrinite-rich (Greenside) and inertinite-rich (Inyanda) coals with relatively low ash content (12.5-16.7 wt. %, adb). Chars were prepared from the parent coals under nitrogen atmosphere at 900 °C. Characterisation results show that the volatiles and moisture were almost completely driven off from the parent coals, indicating that the pyrolysis process was efficient. Physicalstructural properties such as porosity and surface area generally increased from the parent coals to the subsequent chars. The heterogeneous char-gas reactions were conducted isothermally in a TGA on ~1 mm size particles. To ensure that the reactions are under chemical reaction kinetic control regime, different temperatures zones were selected for the three different reaction atmospheres. Combustion reactivity experiments were carried out with air in the temperature range of 387 °C to 425 °C; gasification reactivity with pure steam were conducted at higher temperatures (775 °C - 850 °C) and within 825 °C to 900 °C with carbon dioxide. Experimental results show differences in the specific reaction rate with carbon conversion in different reaction atmospheres and char types. Reaction rates in all three reaction atmospheres were strongly dependent on temperature, and follow the Arrhenius type kinetics. All the investigated reactions (combustion with air and gasification with CO2 and steam) were found to be under chemical reaction control regime (Regime I) for both chars. The inertinite-rich coals exhibit longer burn-out time than chars produced from vitrinite-rich coals, as higher specific reaction rate were observed for the vitrinite-rich coals in the three different reaction atmospheres. The determined random pore model (RPM) structural parameters did not show any significant difference during steam gasification of Greenside and Inyanda chars, whereas higher structural parameter values were observed for Greenside chars during air combustion and CO2 gasification (ψ > 2). However a negative ψ value was determined during CO2 gasification and air combustion of Inyanda chars. The RPM predictions was validated with the experimental data and exhibited adequate fitting to the specific rate of reaction versus carbon conversion plots of the char samples at the different reaction conditions chosen for this study. The activation energy determined was minimal for air and maximum for CO2 for both coals; and ranged from 127-175 kJ·mol-1 for combustion, 214-228 kJ·mol-1 and 210-240 kJ·mol-1 for steam and CO2 gasification respectively. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

To release energy from chemically stored energy in the biomass was the new investigation in recent years. Utilizing of biomass for this purpose occur in two different ways, directly by burning (combustion) the biomass and indirectly by pyrolysis process which will convert the biomass to three main products, bio- tar, bio- char and synthetic gas. Biomass contains different amount of inorganic compound, especially alkali metals which causes some diverse impacts on combustion, pyrolysis and gasification process such as corrosion, agglomeration and fouling problems. This project aims to investigate the effect of K2CO3 on the pyrolysis and gasification processes of three different types of fuel; wood pellets, forest residue pellets and synthetic waste pellets at three different temperatures, 750 °C, 850 °C and 900 °C respectively. The purpose of this work to study and clarify the influence of K2CO3 on char yield, tar yield and tar compositions and the gasification rate and the reactivity of different fuels char. The pyrolysis process was carried out in a fluidized bed reactor during 2 minutes and the products were tar, char and synthetic gas. In this project interested in char and tar only. Char yield calculated and the results shows the char yield increase with increasing of [K2CO3]. While the tar analysis carried on GC- MS instrument at HB to study the tar yield and compositions. The results showed that potassium carbonate has not so much effect on tar yield and its composition. The last part was gasified the char in TGA with steam and CO2 as oxidizing media to study the influence of [K2CO3] on gasification rate and the reactivity of char samples at different temperatures. The result showed the [K2CO3] has inhibitory effect on gasification rate and the reactivity.

Sewage sludge is the product from wastewater treatment that mostly is considered as a waste material. However, it contains several nutrients, especially phosphorus, potassium and nitrogen which are excellent fertilizers. The downside is the harmful content it also carries with pathogens, heavy metals and a variety of organic pollutants that in many cases have unknown effects on the ecosystem. A possible solution to this problem could be to pyrolyse the sewage sludge and by that decrease the levels of heavy metals and also render both pathogens and organic pollutants harmless. In this thesis project pyrolysis of dried sewage sludge has been evaluated at temperatures 650 750, 850 and 950 °C with addition of chlorine in the form of PVC and straw. An energy balance for pyrolysis and drying of dewatered sewage sludge has also been suggested. The results of the pyrolysis evaluation indicate that cadmium concentration can be reduced significantly with increasing temperature in the product char. But also other heavy metals like lead and zinc are affected at the higher temperatures evaluated. Mercury is completely removed from the char residue. The more latent volatile metals copper, chromium and nickel cannot be reduced to lower concentrations at these temperatures. They are instead enriched under these conditions. Chlorine addition to the sludge enhances the evaporation of all heavy metals but copper, nickel and chromium. The energy balance over the system indicates that the drying process requires more energy than is released from the sludge into the pyrolysis gases. The energy carried by the pyrolysis gases is however larger than what is required to drive the pyrolysis process.

Biomass waste has been recognised as a promising, renewable source for future transport fuels. With 1.7 million hectares of pine plantation forests and 12 million cubic meters of annual residue produced by sawmills and the pulp and paper industries, New Zealand presents a prime location where utilisation of these resources can take the next step towards creating a more environmentally friendly future. In this research, the process of fast pyrolysis was investigated using a laboratoryscale, nitrogen-blown fluidised bed pyrolyser at CRL Energy. This equipment can process 1–1.5 kg/h of woody biomass in a temperature range of 450–550°C. The purpose of this rig was to determine the impact of various processing parameters on bio-oil yields. Next, the pyrolysis liquids (bio-oil and tar) were processed downstream into bio-bitumen. Pyrolysis experiments were carried out on Pinus Radiata and Eucalyptus Nitens residue sawdust from sawmills and bark feedstock. The properties of the collected products, including pyrolysis liquids (bio-oil and tar), gas and solid bio-chars, were measured under different operational conditions. Further analysis was also performed to determine pH, volatile content, chemical composition and calorific values of the products. The ultimate goal for this project was to develop a feasible, advanced fast-pyrolysis system for a bio-bitumen production plant using various biomass feedstocks. Additionally, a design for a bio-bitumen production plant was developed, and techno-economic analysis was conducted on a number of plant production yield cases and bio-bitumen manufacture ratios.

En 1954, l’Arme Blindée et Cavalerie (ABC) est une arme qui monte en puissance pour faire face à la menace soviétique en Europe. Le général inspecteur de cette arme voit s’achever la guerre d’Indochine avec un soulagement car il pense pouvoir se consacrer pleinement à cette tâche. Aussi, est-ce avec une certaine réticence, qu’à partir de 1955, il fournit à la Xe région militaire (Algérie) les renforts qu’elle réclame. L’organisation opérationnelle des corps, l’instruction du personnel et le programme d’équipement s’en trouvent très perturbés. Voulant à la fois maintenir sa capacité opérationnelle en Europe et faire face aux besoins de l’Algérie, le commandement désorganise l’ABC. Les unités blindées ne sont adaptées ni à un conflit de type insurrectionnel, ni au terrain particulier de l’Algérie. Pourtant, à partir de 1958, elles donnent satisfaction. Leur composante portée s’est développée, leur puissance de feu et leur mobilité sont mises pleinement à profit sur les barrages, et les unités à cheval, qui ont refait leur apparition, sont employées plus judicieusement sur des terrains favorables. Mais cette adaptation s’est faite au prix de grands sacrifices. Le vieux matériel américain n’est remplacé que très progressivement soit par des engins français modernes (EBR ou AMX 13), que le commandement a le sentiment de gaspiller, soit par des nouveaux matériels (Ferret, AML 60, ou AMX 13 à tourelle de M24) qui ne peuvent être employés qu’en Algérie et dont l’acquisition se fait au détriment du char de 25 t dont doit pourtant être équipée l’ABC d’urgence. En somme, l’ABC aurait rencontré les pires difficultés si le conflit avait dû se prolonger au-delà de 1962. / In 1954, the French Armored Cavalry was a corps that was aiming to get stronger to face the Soviet threat in Europe. The Inspector General of this corps was relieved when the war in Indochina ended because he thought he could rededicate himself to this task. So it was with some reluctance, that from 1955 on wards, he provided the tenth military region (Algeria) with the reinforcements it required. The operational organization of the units, personnel training and equipment program found it very disturbing. Seeking both to maintain its operational capacity in Europe and meet the needs of Algeria, the command reorganized the Armored Cavalry. Armored units were not adapted neither to counter-insurgency, neither to the particular terrain in Algeria. Yet in 1958, they gave satisfying result. The vehicle-mounted infantry had been expanded, their firepower and mobility were expertly used over fences; and horseback units were re-created and deployed more wisely on a favorable terrain. But this re-organization cost very much. The old American equipment was only gradually replaced by French modern equipment (EBR or AMX 13), the command considering this equipment was being wasted. The new materials (Ferret, AML 60, or AMX 13 with M24 turret) could only in Algeria and their acquisition was at the expense the 25 ton tank. However, the French Armored Corps urgently needed this battle tank. To sum up, the Armored Cavalry would have encountered severe difficulties if the conflict had been extended beyond 1962.