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.

Biomass gasification has attracted the interest of researchers because it produces zero carbon to the atmosphere. This technology does not only produce syngas but also the byproducts which can be used for various application depending on quality.The study conducted at Melani village in Alice in the Eastern Cape of South Africa was aimed at investigating the possible applications of the gasification byproducts instead of being thrown away. Pine wood was employed as the parent feedstock material for the gasifier. Biomass gasification by-products were then collected for further analysis. The studied by-products included tar(condensate), char, soot and resin. These materials were also blended to produce strong materials.The essence of the blending was to generate ideal material that is strong but light at the same time.The elemental analysis of the samples performed by CHNS analyser revealed that carbon element is in large quantities in all samples. The FTIR spectra showed almost similar results for all the studied samples, since the samples are end products of lignocellulosegasification. SEM gave the sticky images of resin as well as porous char structures. Char showed a higher heating value of 35.37MJ/Kg when compared to other by-products samples.

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

With increasing energy demand globally and, in particular, in South Africa coupled with depletion of the earth’s fossil energy resources and growing problem of disposal of nonbiodegradable waste such as waste tyres, there is a need and effort globally to find alternative energy from waste material including waste tyres. One possible way of exploiting waste tyre for energy or chemicals recovery is through gasification for the production of syngas, and this is what was investigated in this study. The possibility of gasification of waste tyre blended with coal after pyrolysis was investigated and two Bituminous coals were selected for blending with the waste tyre in co-gasification. A sample of ground waste tyre / waste tire, WT, a high vitrinite coal from the Waterberg coalfield (GG coal) and a high inertinite coal from the Highveld coalfield (SF coal) were used in this investigation. The waste tyre sample had the highest volatile matter content of 63.8%, followed by GG coal with 27% and SF coal with 23.8%. SF coal had the highest ash content of 21.6%, GG coal had 12.6% and waste tyre had the lowest of 6.6%. For the chars, SF char still had the highest ash of 24.8%, but WT char had higher ash, 14.7%, when compared to GG char with 13.9% ash. The vitrinite content in GG coal was 86.3%, whilst in SF coal it was 25% and SF coal had a higher inertinite content of 71% when compared to GG coal with 7.7%. SF char had the highest BET surface area of 126m2/g, followed by GG char with 113m2/g, and WT had the lowest value of 35.09m2/g. The alkali indices of the SF, WT and GG chars were calculated to be 8.2, 4.2 and 1.7 respectively. Coal samples were prepared by crushing and milling to particle sizes less than 75μm before charring in a packed bed balance reactor at temperatures up to 1000oC.Waste tyre samples were charred at the same conditions before milling to < 75μm particle size. Coal and WT chars were blended in ratios of 75:25, 50:50 and 25:75 before gasification experimentation. Carbon dioxide gasification was conducted on the blends and the pure coal and WT chars in a Thermogravimetric analyser (TGA) at 900oC, 925oC, 950oC and 975oC and ambient pressure. 100% CO2 was used at a flow rate of 2L/min. Reactivity of the pure char samples was found to be in the order SF > GG > WT, and the relationship between the coal chars’ reactivities could be explained by the high ash content of the SF char and low reactivity of the WT char corresponds to its low BET surface area. In general, the coal/WT char mixtures were less reactive than the respective coal, but more reactive than the pure WT char, the only exception being the 75% GG char blend which was initially more reactive than the GG char, and reactivity decreased with increasing WT content. For all samples reactivity increased with increasing temperature. The relationship between the reactivities of the GG char and its blends and that of the SF char and its blends was found to be affected by the amount of WT char added, especially at the lower temperatures 900oC and 925oC. SF coal is more reactive than GG coal, but at 900oC and 925oC, the reactivity of GG/WT blends improves in relation to the SF/WT blends with an increase in the ratio of WT in the blends, i.e. the 25% GG char blend is more reactive than the 25% SF char blend. The reactivity of the coal/WT blends was also checked against predicted conversion rates based on the conversion rates of the pure WT and coal samples. At 900oC and 925oC, the reactivities of the blends of both coal chars with WT char were found to be greater than the predicted conversion rates, and for the GG/WT blends the deviation increased with increasing WT ratios, while for the SF/WT blends the deviation increased with increasing SF ratios. These findings suggest the presence of synergism or enhancement between the coal chars and WT char in gasification reactions. The random pore model (RPM) was used to model the gasification results and it was found to adequately describe the experimental data. Activation energies determined with the RPM were found to be 205.4kJ/mol, 189.9kJ/mol and 173.9kJ/mol for SF char, WT char and GG char respectively. The activation energies of the coal/WT blends were found to be lower than those of both the pure coal and the pure WT chars. For the GG/WT blends the activation energy decreased with increasing WT char ratio, while for the SF/WT blends the activation energy decreased with increasing SF char ratio. The trends of the activation energies and conversion rates of the blends point to synergism or enhancement between the coal and WT chars in CO2 gasification reactions, and in the GG/WT blends this enhancement is driven more by the WT char, while in SF/WT blends it is driven by SF chars. It is possible that enhancement of the reactions is caused by mineral matter catalysis of the gasification reactions. The ash contents and alkali indices of the pure samples follow the order SF > WT > GG. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

With increasing energy demand globally and, in particular, in South Africa coupled with depletion of the earth’s fossil energy resources and growing problem of disposal of nonbiodegradable waste such as waste tyres, there is a need and effort globally to find alternative energy from waste material including waste tyres. One possible way of exploiting waste tyre for energy or chemicals recovery is through gasification for the production of syngas, and this is what was investigated in this study. The possibility of gasification of waste tyre blended with coal after pyrolysis was investigated and two Bituminous coals were selected for blending with the waste tyre in co-gasification. A sample of ground waste tyre / waste tire, WT, a high vitrinite coal from the Waterberg coalfield (GG coal) and a high inertinite coal from the Highveld coalfield (SF coal) were used in this investigation. The waste tyre sample had the highest volatile matter content of 63.8%, followed by GG coal with 27% and SF coal with 23.8%. SF coal had the highest ash content of 21.6%, GG coal had 12.6% and waste tyre had the lowest of 6.6%. For the chars, SF char still had the highest ash of 24.8%, but WT char had higher ash, 14.7%, when compared to GG char with 13.9% ash. The vitrinite content in GG coal was 86.3%, whilst in SF coal it was 25% and SF coal had a higher inertinite content of 71% when compared to GG coal with 7.7%. SF char had the highest BET surface area of 126m2/g, followed by GG char with 113m2/g, and WT had the lowest value of 35.09m2/g. The alkali indices of the SF, WT and GG chars were calculated to be 8.2, 4.2 and 1.7 respectively. Coal samples were prepared by crushing and milling to particle sizes less than 75μm before charring in a packed bed balance reactor at temperatures up to 1000oC.Waste tyre samples were charred at the same conditions before milling to < 75μm particle size. Coal and WT chars were blended in ratios of 75:25, 50:50 and 25:75 before gasification experimentation. Carbon dioxide gasification was conducted on the blends and the pure coal and WT chars in a Thermogravimetric analyser (TGA) at 900oC, 925oC, 950oC and 975oC and ambient pressure. 100% CO2 was used at a flow rate of 2L/min. Reactivity of the pure char samples was found to be in the order SF > GG > WT, and the relationship between the coal chars’ reactivities could be explained by the high ash content of the SF char and low reactivity of the WT char corresponds to its low BET surface area. In general, the coal/WT char mixtures were less reactive than the respective coal, but more reactive than the pure WT char, the only exception being the 75% GG char blend which was initially more reactive than the GG char, and reactivity decreased with increasing WT content. For all samples reactivity increased with increasing temperature. The relationship between the reactivities of the GG char and its blends and that of the SF char and its blends was found to be affected by the amount of WT char added, especially at the lower temperatures 900oC and 925oC. SF coal is more reactive than GG coal, but at 900oC and 925oC, the reactivity of GG/WT blends improves in relation to the SF/WT blends with an increase in the ratio of WT in the blends, i.e. the 25% GG char blend is more reactive than the 25% SF char blend. The reactivity of the coal/WT blends was also checked against predicted conversion rates based on the conversion rates of the pure WT and coal samples. At 900oC and 925oC, the reactivities of the blends of both coal chars with WT char were found to be greater than the predicted conversion rates, and for the GG/WT blends the deviation increased with increasing WT ratios, while for the SF/WT blends the deviation increased with increasing SF ratios. These findings suggest the presence of synergism or enhancement between the coal chars and WT char in gasification reactions. The random pore model (RPM) was used to model the gasification results and it was found to adequately describe the experimental data. Activation energies determined with the RPM were found to be 205.4kJ/mol, 189.9kJ/mol and 173.9kJ/mol for SF char, WT char and GG char respectively. The activation energies of the coal/WT blends were found to be lower than those of both the pure coal and the pure WT chars. For the GG/WT blends the activation energy decreased with increasing WT char ratio, while for the SF/WT blends the activation energy decreased with increasing SF char ratio. The trends of the activation energies and conversion rates of the blends point to synergism or enhancement between the coal and WT chars in CO2 gasification reactions, and in the GG/WT blends this enhancement is driven more by the WT char, while in SF/WT blends it is driven by SF chars. It is possible that enhancement of the reactions is caused by mineral matter catalysis of the gasification reactions. The ash contents and alkali indices of the pure samples follow the order SF > WT > GG. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In light of the rapid depletion of the world’s oil reserves, concerns about energy security prompted the exploration of alternative sources of liquid fuels for transportation. One such alternative is the production of synthetic fuels with the indirect coal liquefaction process or Coal-To-Liquids (CTL) process. In this process, coal is burned in a gasifier in the presence of steam and oxygen to produce a synthesis gas or syngas, consisting mainly of hydrogen and carbon monoxide. The syngas is then converted to liquid fuels and a variety of useful chemicals in a Fischer Tropsch synthesis reactor. However, the traditional process for syngas production also produces substantial amounts of carbon dioxide. In fact, only about one third of the carbon in the coal feedstock ends up in the liquid fuel product using traditional CTL technology. If additional hydrogen was available, the carbon utilisation of the process could be improved significantly. The high temperature reactor (HTR) is a gas cooled Generation IV nuclear reactor ideally suited to provide electrical power and high temperature heat for the production of carbon neutral hydrogen via high temperature electrolysis. The integration of an HTR into a CTL process therefore provides an opportunity to improve the thermal and carbon efficiency of the CTL process significantly. This thesis presents a possible process flow scheme for a nuclear assisted CTL process. The system is evaluated in terms of its thermal or syngas production efficiency (defined as the ratio of the heating value of the produced syngas to the sum of the heating value of the coal plus the HTR heat input) as well as its carbon utilisation. If the hydrogen production plant is sized to produce only enough associated oxygen to supply in the needs of the gasification plant, syngas is produced at about 63% thermal efficiency, while 71.5% of the carbon is utilised in this process. It was found that the optimum HTR outlet temperature to produce hydrogen with a high temperature steam electrolysis process is 850°C. If enough process heat and electrical power are available and process equipment capacities are sufficient, the carbon utilisation of the process could be improved even further to values in excess of 90%. / AFRIKAANSE OPSOMMING: Die uitputting van die wêreld se olie-reserwes, asook kommer oor energiesekuriteit het daartoe gelei dat alternatiewe bronne van vloeibare brandstowwe vir vervoer ondersoek moes word. Een so 'n alternatief is die produksie van sintetiese brandstof d.m.v. die indirekte steenkool vervloeiing proses of sogenaamde Coal-To-Liquids (CTL) proses. In hierdie proses word steenkool in die teenwoordigheid van stoom en suurstof in 'n vergasser gebrand om 'n sintesegas of singas te produseer, wat hoofsaaklik uit waterstof en koolstofmonoksied bestaan. Die sintesegas word daarna omgeskakel na vloeibare brandstowwe en 'n verskeidenheid van nuttige chemikalieë in 'n Fischer-Tropsch-sintese reaktor. Ongelukkig produseer die tradisionele proses vir sintesegas produksie ook 'n beduidende hoeveelheid koolstofdioksied. Trouens, slegs sowat een derde van die koolstof in die steenkool roumateriaal eindig in die vloeibare brandstof produk indien van tradisionele CTL-tegnologie gebruik gemaak word. Indien addisionele waterstof beskikbaar was, kon die koolstofbenutting van die proses aansienlik verbeter word. Die hoë temperatuur reaktor (HTR) is 'n gas-verkoelde Generasie IV kernreaktor wat by uitstek geskik is om elektrisiteit en hoë temperatuur hitte te verskaf vir die produksie van koolstofneutrale waterstof d.m.v. hoë temperatuur elektrolise. Die integrasie van 'n HTR in 'n CTL-proses bied dus 'n geleentheid om die termiese- en koolstofdoeltreffendheid van die CTL-proses aansienlik te verbeter. In hierdie ondersoek word 'n moontlike proses vloeidiagram vir 'n kern-gesteunde CTL-proses voorgestel. Die stelsel is geëvalueer in terme van sy termiese- of sintesegas produksie doeltreffendheid (gedefinieer as die verhouding van die hittewaarde van die geproduseerde sintesegas gedeel deur die som van die hittewaarde van die steenkool en die HTR hitte-insette) sowel as sy koolstof-effektiwiteit. Indien die waterstof produksie-aanleg ontwerp word om net genoeg geassosieerde suurstof te voorsien om in die behoeftes van die vergassing-aanleg te voorsien, word sintesegas teen ongeveer 63% termiese doeltreffendheid vervaardig, terwyl 71.5% van die koolstof in hierdie proses benut word. Daar is bevind dat 850°C die optimum HTR uitlaat temperatuur is om waterstof d.m.v. hoë temperatuur stoom-elektrolise te vervaardig. Indien daar genoeg proses hitte en elektrisiteit beskikbaar is en die proses toerusting kapasiteite voldoende is, sou die koolstof-benutting van die proses tot meer as 90% verbeter kon word.

This paper introduces an energy-saving biomass stove. The principle of energy-saving biomass stove is gasification. It is a chemical process, transforms solid fuel into a gas mixture, called (CO + H2 + CH4) gas. Emission lines in the stove chimneys typically remain high temperatures around 900 to 1200C. The composition of the flue gas consists of combustion products of rice husk which are mainly CO2, CO, N2. A little volatile in the rice husk, which could not burn completely, residual oxygen and dust will fly in airflow. The amount of dust in the outlet gas is a combination of unburnt amount of impurity and firewood, usually occupied impurity rate of 1 % by weight of dry husk. Outlet dust of rice husk furnace has a normal size from 500μm to 0.1 micron and a particle concentration ranges from 200-500 mg/m3. Gas emissions is created when using energy-saving stove and they will be used as the main raw material in combustion process Therefore the CO2 emission into the environment when using the stove will be reduced up to 95% of a commonly used stove. / Bài báo giới thiệu một bếp tiết kiệm dùng năng lượng sinh khối. Bếp tiết kiệm năng lượng thực hiện nguyên lý khí hóa sinh khối. Đó là một quá trình hóa học, chuyển hóa các loại nhiên liệu dạng rắn thành một dạng hỗn hợp khí đốt, gọi là khí Gas (CO + H2 + CH4). Dòng khí thải ra ở ống khói của bếp thông thường có nhiệt độ vẫn còn cao khoảng 900 ~ 1200C. Thành phần của khói thải bao gồm các sản phẩm cháy của trấu, chủ yếu là các khí CO2, CO, N2, một ít các chất bốc trong trấu không kịp cháy hết, oxy dư và tro bụi bay theo dòng khí. Lượng bụi tro có trong khói thải chính là một phần của lượng không cháy hết và lượng tạp chất không cháy có trong củi, lượng tạp chất này thường chiếm tỷ lệ 1% trọng lượng trấu khô.Bụi trong khói thải lò đốt trấu thông thường có kích thước hạt từ 500μm tới 0,1μm, nồng độ dao động trong khoảng từ 200-500 mg/m3. Lượng khí thải được sinh ra khi sử dụng bếp tiết kiệm năng lượng, sẽ được dùng làm nguyên liệu đốt cháy chính của quá trình đó. Do đó lượng khí CO2 thải ra môi trường khi sử dụng bếp tiết kiệm sẽ được giảm xuống 95 % so với sử dụng bếp thường.

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.

Sustainable energy sources are of great importance, and will become even more important in the future. Gasification of biomass is an important process for utilization of biomass, as a renewable energy carrier, to produce fuels and chemicals. Density functional theory (DFT) calculations were used to investigate i) the effect of co-adsorption of water and CO on the Ni(111) catalysed water splitting reaction, ii) water adsorption and dissociation on Ni(111), Ni(100) and Ni(110) surfaces, as well as iii) formyl oxidation and dissociation, iv) hydrocarbon combustion and synthesis, and v) the water gas shift (WGS) reaction on these surfaces. The results show that the structures of an adsorbed water molecule and its splitting transition state are significantly changed by co-adsorption of a CO molecule on the Ni(111) surface. This leads to less exothermic reaction energy and larger activation barrier in the presence of CO which means that far fewer water molecules will dissociate in the presence of CO. For the adsorption and dissociation of water on different Ni surfaces, the binding energies for H2O and OH decrease in the order Ni(110) &gt; Ni(100) &gt; Ni(111), and the binding energies for O and H atoms decrease in the order Ni(100) &gt; Ni(111) &gt; Ni(110). In total, the complete water dissociation reaction rate decreases in the order Ni(110) &gt; Ni(100) &gt; Ni(111). The reaction rates for both formyl dissociation to CH + O and to CO + H decrease in the order Ni(110) &gt; Ni(111) &gt; Ni(100). However, the dissociation to CO + H is kinetically favoured. The oxidation of formyl has the lowest activation energy on the Ni(111) surface. For combustion and synthesis of hydrocarbons, the Ni(110) surface shows a better catalytic activity for hydrocarbon combustion compared to the other surfaces. Calculations show that Ni is a better catalyst for the combustion reaction compared to the hydrocarbon synthesis, where the reaction rate constants are small. It was found that the WGS reaction occurs mainly via the direct pathway with the CO + O → CO2 reaction as the rate limiting step on all three surfaces. The activation barrier obtained for this rate limiting step decreases in the order Ni(110) &gt; Ni(111) &gt; Ni(100). Thus, the WGS reaction is fastest on the Ni(100) surface if O species are present on the surfaces. However, the barrier for desorption of water (as the source of the O species) is lower than its dissociation reaction on the Ni(111) and Ni(100) surfaces, but not on the Ni(110) surface. Therefore the direct pathway on the Ni(110) surface will dominate and will be the rate limiting step at low H2O(g) pressures. The calculations also reveal that the WGS reaction does not primarily occur via the formate pathway, since this species is a stable intermediate on all surfaces. All reactions studied in this work support the Brønsted-Evans-Polanyi (BEP) principles.

La pyrolyse et la gazéification sont les deux procédés les plus prometteurs pour une valorisation thermique des déchets organiques solides en réponse aux objectifs énergétiques environnementaux actuels et futurs. Si pour la pyrolyse, les déchets traités sont aussi synthétiques (plastiques, composites) que naturels (biomasse), pour la gazéification c'est la biomasse qui est la matière première la plus rencontrée. Les travaux expérimentaux de cette thèse ont été réalisés dans deux types d'installations : une installation à échelle laboratoire (analyseur thermique : TG, ATD, EGA) et une installation à échelle pilote (nommée four « Aubry »). Les traitements thermiques ont été effectués dans les conditions spécifiques pour la pyrolyse (atmosphère d'azote) et la gazéification (vapeurs d'eau). Les matériaux testés ont été le polychloroprène, les composés de la biomasse (hémicellulose, lignine, cellulose), seuls où en mélange, ainsi qu'un bois naturel (le bouleau) et son « modèle » (mélange en proportions équivalents de ses constituants). Deux modèles cinétiques pour la pyrolyse du polychloroprène ont été choisis de littérature et testés. La différence primordiale entre les deux modèles est leur degré de complexité. Le premier est un modèle empirique simplifié, tandis que le deuxième, très détaillé, est un modèle radicalaire Le modèle cinétique utilisé pour modéliser le processus de pyrolyse de la cellulose, pris aussi de la littérature, a montré une concordance très bonne avec nos résultats expérimentaux. L'étude hôte de la gazéification à la vapeur d'eau a nécessité des modifications de nos installations expérimentales, tout particulièrement à l'échelle pilote, pour assurer une atmosphère confinée en vapeur d'eau. Les expériences réalisées en conditions expérimentales spécifiques ont données des résultats excellents pour la composition finale du gaz de synthèse. La simulation, à l'échelle pilote, de la gazéification a été obtenue par adaptation d'un modèle existant, à la réalisation de nos conditions opératoires, prenant en compte les transferts matières et basé sur l'évolution de la porosité d'une particule sphérique équivalente. Le modèle a montré une concordance raisonnable avec nos données expérimentales. La dernière partie de cette thèse présente une étude dans lequel on compare les analyses thermiques pour les constituants purs, un modèle de bois et un bois naturel afin d'établir les interactions possibles entre ces composants lors de la dégradation thermique du bois naturel. Les résultats ont montré que pour les mélanges cellulose-lignine et lignine-hémicellulose, le premier composé inhibe la dégradation du dernier tandis que, pour les mélanges cellulose-hémicellulose, cet effet se manifeste à l'inverse. Tous les modèles testés et les résultats enregistrés dans cette thèse représentent des instruments très utiles pour l'aide au dimensionnement des installations de pyrolyse à échelle laboratoire ainsi que pour des installations de gazéification à la vapeur d'eau à échelle pilote. / The pyrolysis and gasification are the most actual techniques used for valorization of organic wastes. If for pyrolysis the raw materials are both synthetic (plastics) and natural (biomass), in the case of gasification mainly the biomass is used. The experiments presented in this thesis were carried out in two type of plants: a laboratory scale plant (thermal analyses: TGA, DTA, EGA) and a pilot scale plant (so-called “Aubry” furnace). The thermal treatments implemented both the conditions of pyrolysis (nitrogen atmosphere) and gasification (water vapors). The materials tested in the experimental part were: polychloroprene, biomass constituents (hemicelluloses, lignin and cellulose), alones and in mixture, and a natural wood (the birch) with it's “model” (a mixture of it's components in different proportions). For the polychloroprene pyrolysis, two kinetic models chosen from the published literature were tested. The difference in the two models is given by their degree of complexity. The first one was a simplified empirical model. The second one was a free-radical model. For the cellulose pyrolysis was also tested a model proposed in the literature and the model showed a good accuracy in representing our experimental data. The study of gasification at pilot scale needed an appropriate modification of the experimental set-up to create a saturated atmosphere in water vapor inside the Aubry furnace. The experimental work concerning the gasification followed a specific protocol and gave excellent results for the syngas composition. A gasification mathematical model for pilot scale was proposed and tested. This model, based on the evolution of equivalent spherical particles porosity, take supplementary into account the mass transfer. The results given by the last model were in reasonable agreement with our experimental results. The last part of this thesis presents a comparative study of the thermal analyses of pure biomass components, of a wood model and also of a natural wood. The goal is to identify the interactions that could take place between these compounds during the thermal degradation of the natural wood. Our results showed that for the mixtures cellulose-lignin and lignin-hemicelluloses the first compound inhibits the second one. For the mixtures cellulose-hemicelluloses this effect is inverse. All the kinetic models tested in this thesis are useful tools for dimensioning laboratory scale pyrolysis plants and pilot scale set-up for water vapors gasification.