Due to security issues in energy supply and environmental concerns, renewable energy production from biomass becomes an increasingly important area of study. Thus, thermal conversion of biomass via pyrolysis and subsequent upgrading procedures were explored, in an attempt to convert an abundant agricultural residue, corn stover, into potential bio-fuels. Pyrolysis of corn stover was carried out at 400, 500 and 600oC and at moderate pressure. Maximum bio-char yield of 37.3 wt.% and liquid product yield of 31.4 wt.% were obtained at 400oC while the gas yield was maximum at 600oC (21.2 wt.%). Bio-char characteristics (energy content, proximate and ultimate analyses) indicated its potential as alternative solid fuel. The bio-oil mainly consisted of phenolic compounds, with significant proportions of aromatic and aliphatic compounds. The gas product has energy content ranging from 10.1 to 21.7 MJ m-3, attributed to significant quantities of methane, hydrogen and carbon dioxide. Mass and energy conversion efficiencies indicated that majority of the mass and energy contained in the feedstock was transferred to the bio-char. Fractional distillation of the bio-oil at atmospheric and reduced pressure yielded approximately 40-45 wt.% heavy distillate (180-250oC) with significantly reduced moisture and total acid number (TAN) and greater energy content. Aromatic compounds and oxygenated compounds were distributed in the light and middle fractions while phenolic compounds were concentrated in the heavy fraction. Finally, hydrotreatment of the bio-oil and the heavy distillate using noble metal catalysts such as ruthenium and palladium on carbon support at 100 bar pressure, 4 hours reaction time and 200o or 300oC showed that ruthenium performed better at the higher temperature (300oC) and was more effective than palladium, giving about 25-26% deoxygenation. The hydrotreated product from the heavy distillate with ruthenium as catalyst at 300oC had the lowest oxygen content and exhibited better product properties (lower moisture, TAN, and highest heating value), and can be a potential feedstock for co-processing with crude oils in existing refineries. Major reactions involved were conversion of phenolics to aromatics and hydrogenation of ketones to alcohols. Results showed that pyrolysis of corn stover and product upgrading produced potentially valuable sources of fuel and chemical feedstock.

Bio-oil which is produced by fast pyrolysis of biomass has high energy density compared to as received biomass. Two cases are studied for pipeline transport of bio-oil, a coal-based and hydro power based electricity supplies. These cases of pipeline transport are compared to two cases of truck transport (trailer and super B-train truck). The life cycle GHG emissions from the pipeline transport of bio-oil for the two sources of electricity are 345 and 17 g of CO2 m-3 km-1. The emissions for transport by trailer and super B-train truck are 89 and 60 g of CO2 m-3 km-1. Energy input for bio-oil transport is 3.95 MJ m-3 km-1 by pipeline, 2.59 MJ m-3 km-1 by trailer, and 1.66 MJ m-3 km-1 by super B-train truck. The results show that GHG emissions in pipeline transport are largely dependent on the source of electricity; substituting 250 m3 day-1 of pipeline-transported bio-oil for coal can mitigate about 5.1 million tonnes of CO2 per year in the production of electricity. The fixed and variable components of cost are 0.0423 $/m3 and 0.1201 $/m3/km at a pipeline capacity of 560 m3/day and for a distance of 100. It costs less to transport bio-oil by pipeline than by trailer and super B-train tank trucks at pipeline capacities of 1,000 and 1,700 m3/day, and for a transportation distance of 100 km. Power from pipeline-transported bio-oil is expensive than power that is produced by direct combustion of wood chips and transmitted through electric lines.

O desenvolvimento de tecnologias para geração de hidrogênio no Brasil tem se tornado um fator relevante, pois se trata de uma fonte de combustível limpa que pode ser obtida a partir de diversas matérias-primas renováveis. Entre essas tecnologias pode-se destacar a reforma a vapor do bio-óleo, proveniente da pirólise da biomassa. O bio-óleo consiste em uma mistura complexa de diversos compostos orgânicos oxigenados tais como: aldeídos, ácidos carboxílicos, cetonas, carboidratos, alcoóis, entre outros, sendo o ácido acético um dos compostos majoritários (∼12-15%), o qual pode ser utilizado como molécula modelo do bio-óleo em reações de reforma a vapor. Entretanto, a reforma a vapor do ácido acético apresenta algumas dificuldades, como a formação de coque na superfície dos catalisadores, o que pode resultar na desativação do mesmo. Dentro deste contexto, este trabalho teve como objetivo desenvolver catalisadores a base de níquel (Ni) promovidos com magnésio (Mg) e nióbio (Nb) suportados em alumina (γ-Al2O3), para aplicação na reforma a vapor do ácido acético, visando minimizar e/ou modificar a estrutura dos depósitos carbonáceos, bem como aumentar a atividade e seletividade para o hidrogênio. Para isso, sintetizaram-se inicialmente três catalisadores com diferentes teores de Ni, (10, 15 e 20%), suportados em alumina, sendo que o catalisador com 15% de Ni em massa foi o que apresentou melhor seletividade e atividade para a reforma a vapor do ácido acético. A partir da melhor carga de Ni, adicionaram-se quatro diferentes teores de Mg e Nb 1,0%; 2,5%; 5,0% e 10% em massa. Entre os catalisadores promovidos com Mg, o catalisador com 5,0% de Mg (15%Ni5%Mg/Al), apresentou uma conversão de 96% para o ácido acético, com seletividade para o hidrogênio em torno de 65% a 600 oC. Além disso, este catalisador apresentou menor taxa de formação de coque e menor tamanho de partícula de Ni0, comparado ao catalisador não promovido (15%Ni/Al), evidenciando que a adição de Mg pode prevenir a sinterização das partículas de Ni. Entre os catalisadores promovidos com Nb, o catalisador 15%Ni2,5%Nb/Al apresentou maior seletividade para o hidrogênio (∼73%) a 600o C comparado aos demais. Apesar de ter apresentado um maior tamanho de partícula Ni0, a adição de Nb aumentou a capacidade de decomposição do metano, proveniente da reação de decomposição e metanação do ácido acético, favorecendo a produção de hidrogênio, além de promover a formação de nanoestruturas de carbono. Assim, a adição de promotores catalíticos como os estudados neste trabalho pode contribuir para o aumento na produção de hidrogênio, seja pela redução nos depósitos carbonáceos ou pela modificação das estruturas de carbono formados na superfície dos materiais. / The development of technologies for generating hydrogen in Brazil has become an important factor because it is a source of clean fuel which can be obtained from different renewable raw materials. Among these technologies, the steam reforming of bio-oil from the pyrolysis of biomass can be highlighted. The bio-oil is a complex mixture of different oxygenated organic compounds such as aldehydes, carboxylic acids, ketones, carbohydrates and alcohols with acetic acid being one of the major compounds (∼12-15%), which may be used as a model molecule of bio-oil steam reforming reactions. However, the steam reforming of acetic acid presents some difficulties, such as coke formation on the surface of the catalysts, which may result in its deactivation. Thus, this work aimed to develop catalysts based on nickel (Ni) promoted with magnesium (Mg) and niobia (Nb) supported on alumina (γ-Al2O3), for application in steam reforming of acetic acid in order to minimize the formation of carbonaceous residues, as well as increase the activity and selectivity for hydrogen. For this purpose, initially three catalysts were synthesized with different Ni content, (10, 15 and 20%), and the catalyst with 15% Ni mass showed the best activity and selectivity for the steam reforming of acid acetic acid. From the best Ni loading, was added four different concentrations of Mg and Nb, 1%; 2.5%; 5% and 10% by weight. Among the catalysts promoted with Mg, the catalyst with 5% Mg (15% Ni5% Mg/Al) at a temperature of 600 °C, showed a 96% conversion of acetic acid, with selectivity to hydrogen of around 65 %. In addition, this catalyst showed lower rate of coke formation and lower Ni particle size compared to the non-promoted catalyst (15% Ni/Al), showing that the addition of Mg can prevent sintering of Ni particles. Among the catalysts promoted with Nb, the catalyst 15% Ni 2, 5% Nb/Al showed higher selectivity to hydrogen (∼73%) at 600 °C compared to the others. Despite having a larger particle size, the addition of Nb increased the capacity of decomposition of methane from of the decomposition reaction and methanation of acetic acid favoring the production of hydrogen and promoted the formation of nanostructures. Thus, the addition of catalytic promoters can contribute to the increase in hydrogen production, either by a reduction in carbonaceous deposits or the modification of structures formed on the surface of the materials.

With 220 billion dry tons available, biomass is one of the world’s most abundant energy source; it also could be a reliable energy source. The human population annual rate of production is 275 million tons of plastic waste as of the year 2019, which has to be managed to facilitate circular carbon economy. Pyrolysis of biomass has emerged as an attractive option for converting waste into bioenergy. Because of its high oxygen content, acidity and viscosity, pyrolysis bio-oil is generally a low-quality product that requires upgrading before being used directly as a drop-in fuel and a fuel additive; this upgrade is achieved by co-pyrolysis of biomass with waste polymers. Since polymers are a rich source of hydrogen, pyrolysis vapors are upgrade; the advantage of co-pyrolysis is that a separate hydroprocessing unit becomes unnecessary after process optimization. Machine learning is emerging as a growing field to predict and optimize the energy related processes. The process can be finetuned using the models trained on the existing experimental data. In this research, machine learning models were developed to predict product yields from the co-pyrolysis of biomass and polymers. Data from the literature on co-pyrolysis of lignocellulosic biomass and polymer co-pyrolysis provided a tool to predict these outcomes. Machine learning algorithms were examined and trained with datasets acquired for biochar and bio-oil yields, with cross-validation and hyperparameters to fit the ultimate and proximate analysis of the reactants and physical conditions of the reactions. XGBoost predicted a biochar yield with RMSE of 1.77 and R$^2$ of 0.96, and a dense neural network predicted a bio-oil yield with RMSE 2.6 and R$^2$ of 0.96. Proximate analysis features were a necessary addition to the bio-oil model. SHAP (SHapley Additive exPlanations) analysis for the DNN liquid model found biomass fixed carbon, biomass moisture and biomass volatile matter with 0.11, 0.09, and 0.06 mean absolute SHAP values, respectively. The machine learning models provided a convenient and predictive tool for co-pyrolysis reaction within the range of the model’s errors and training features. These models also offered insight into the development of municipal solid waste pyrolysis in a circular carbon economy.

The objectives of this dissertation’s studies were to determine the effects of different additives on biomass wood pellets’ physical properties and the production energy required to produce each treatment. Chapter II was completed using a pneumatic pelletizer as a small scale test to determine effects of different additives. The pneumatic pelletizer was a good indicator of which additives can be successfully pelletized. The results of this chapter show that using bio-oil can significantly increase calorific value, without significantly decreasing durability and significantly increasing production energy required. Corn starch, in a 4% treatment, was shown to not hinder durability or calorific value significantly, but significantly lower production energy. Biochar was shown to be an additive insignificant in production due to such a low durability. Chapter III is a scaled up pelleting study, which takes additives from Chapter II as well as multiple new additives to determine each one’s effects on the physical properties and production energy effects. The larger scale, Sprout Walden pelletizer gave much different results than that of the pneumatic pelletizer. The results tend to prove beneficial to durability, calorific value, and bulk density with multiple of the treatments. Vegetable oil was a treatment shown to be less beneficial with each increase in additive and would not be recommended in a production setting at such levels. Chapter IV focused on the economic effect of the pellets produced in Chapter III. Equations were made to determine the possible marginal revenue using each of the treatments. The marginal revenue equations take into account the changes in durability and calorific value. Biochar 4%, and vegetable oil at 1% and 2% show that an increase in marginal revenue could be possible with these treatments.

Bio-oil created from biomass sources do not have desirable fuel qualities. Due to their petroleum origins, plastics and micronized rubber powder (MRP) improve oil quality when co-pyrolyzed with biomass. Southern yellow pine, a food grade polymer (FGP) and micronized rubber powder (MRP) were co-pyrolyzed at various ratios in an auger reactor to improve the bio-oil. MRP proved to be the best additive, reducing acids, creating aromatic hydrocarbons, reducing water content, and increasing heating values in created bio-oil, while the FGP led to a formation of a liquid product containing a high concentration of phenolic compounds. To improve these qualities further, nickel oxide and sodium carbonate were added in-vivo to the coeeds. Nickel oxide influenced higher aromatic hydrocarbon production and reduced oxygen formation. Sodium carbonate greatly reduced the concentration of acids and water. Both catalysts improved the creation of unsaturated hydrocarbons, phenol compounds, and enhanced heating values with nickel oxide performing better than sodium carbonate.

There is a growing need to develop the processes to produce renewable fuels and chemicals due to the economical, political, and environmental concerns associated with the fossil fuels. One of the most promising methods for a small scale conversion of biomass into liquid fuels is fast pyrolysis. The liquid product obtained from the fast pyrolysis of biomass is called pyrolysis oil or bio-oil. It is a complex mixture of more than 300 compounds resulting from the depolymerization of biomass building blocks, cellulose; hemi-cellulose; and lignin. Bio-oils have low heating value, high moisture content, are acidic, contain solid char particles, are incompatible with existing petroleum based fuels, are thermally unstable, and degrade with time. They cannot be used directly in a diesel or a gasoline internal combustion engine. One of the challenges with the bio-oil is that it is unstable and can phase separate when stored for long. Its viscosity and molecular weight increases with time. It is important to identify the factors responsible for the bio-oil instability and to stabilize the bio-oil. The stability analysis of the bio-oil showed that the high molecular weight lignin oligomers in the bio-oil are mainly responsible for the instability of bio-oil. The viscosity increase in the bio-oil was due to two reasons: increase in the average molecular weight and increase in the concentration of high molecular weight oligomers. Char can be removed from the bio-oil by microfiltration using ceramic membranes with pore sizes less than 1 µm. Removal of char does not affect the bio-oil stability but is desired as char can cause difficulty in further processing of the bio-oil. Nanofiltration and low temperature hydrogenation were found to be the promising techniques to stabilize the bio-oil. Bio-oil must be catalytically converted into fuels and chemicals if it is to be used as a feedstock to make renewable fuels and chemicals. The water soluble fraction of bio-oil (WSBO) was found to contain C2 to C6 oxygenated hydrocarbons with various functionalities. In this study we showed that both hydrogen and alkanes can be produced with high yields from WSBO using aqueous phase processing. Hydrogen was produced by aqueous phase reforming over Pt/Al2O3 catalyst. Alkanes were produced by hydrodeoxygenation over Pt/SiO2-Al2O3. Both of these processes were preceded by a low temperature hydrogenation step over Ru/C catalyst. This step was critical to achieve high yields of hydrogen and alkanes. WSBO was also converted to gasoline-range alcohols and C2 to C6 diols with up to 46% carbon yield by a two-stage hydrogenation process over Ru/C catalyst (125 °C) followed by over Pt/C (250 °C) catalyst. Temperature and pressure can be used to tune the product selectivity. The hydroprocessing of bio-oil was followed by zeolite upgrading to produce C6 to C8 aromatic hydrocarbons and C2 to C4 olefins. Up to 70% carbon yield to aromatics and olefins was achieved from the hydrogenated aqueous fraction of bio-oil. The hydroprocessing steps prior to the zeolite upgrading increases the thermal stability of bio-oil as well as the intrinsic hydrogen content. Increasing the thermal stability of bio-oil results in reduced coke yields in zeolite upgrading, whereas, increasing the intrinsic hydrogen content results in more oxygen being removed from bio-oil as H2O than CO and CO2. This results in higher carbon yields to aromatic hydrocarbon and olefins. Integrating hydroprocessing with zeolite upgrading produces a narrow product spectrum and reduces the hydrogen requirement of the process as compared to processes solely based on hydrotreating. Increasing the yield of petrochemical products from biomass therefore requires hydrogen, thus cost of hydrogen dictates the maximum economic potential of the process.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-10-17T20:21:34Z No. of bitstreams: 1 DAUCI PINHEIRO RODRIGUES - TESE PPGEP 2014..pdf: 15558379 bytes, checksum: 466dcc6a1f195a3b008e5ed0c6d8321a (MD5) / Made available in DSpace on 2018-10-17T20:21:34Z (GMT). No. of bitstreams: 1 DAUCI PINHEIRO RODRIGUES - TESE PPGEP 2014..pdf: 15558379 bytes, checksum: 466dcc6a1f195a3b008e5ed0c6d8321a (MD5) Previous issue date: 2014-02-12 / A utilização de combustíveis alternativos vem ganhando destaque no mundo inteiro, pois além do petróleo ser uma fonte esgotável de energia, emite grandes quantidades de gases poluentes. Propostas têm surgido para substituição dos combustíveis fósseis, entre elas se destacam os biocombustíveis, a partir de óleos vegetais e gorduras animais. Partindo deste contexto, este trabalho tem como objetivo avaliar a estabilidade térmica do bio-óleo de girassol, obtido por craqueamento térmico e termocatalítico. Inicialmente as amostras do catalisador foram sintetizadas e caracterizadas por DRX, área superficial por adsorção de nitrogénio, FRX, FTIR, TG/DTG/DTA, TPD-NH3, infravermelho por adsorção de piridina e RMN de31P,27Al, e 29Si. Os resultados obtidos pela difratometria de raios-X indicaram que as amostras de SAPO-5 possuem boa cristalinidade, evidenciando que o método de síntese empregado foi eficiente. A acidez das amostras do catalisador nos diversos teores de silício foi avaliada por (TPD-NH3) e infravermelho por adsorção de piridina. Pela TPD-NH3 verificou-se a presença de dois tipos de sítios ácidos, um mais fraco que dessorve amónia em temperaturas mais baixas e outro mais forte que dessorve amónia em temperaturas mais altas. Por meio da adsorção de piridina detectou-se a maior presença de sítios ácidos fracos de Bronsted para todas as amostras analisadas, sendo a amostra S040 a que apresentou maior quantidade de sítios de Bronsted e Lewis. A análise RMN de 29Si indicou para todas as amostras, a presença de mais de um tipo de mecanismo de incorporação do silício à rede de um aluminofosfato, tendo o SM2 ocorrido em maior proporção. Os craqueamentos térmico e termocatalítico do óleo de girassol, realizados da temperatura ambiente a 550°C, em um reator batelada com sistema de destilação simples, forneceram duas frações líquidas orgânicas. A primeira fração coletada em ambos os processos apresentou índice de acidez elevado (170 mg KOH/mg de bio-óleo), indicando que o catalisador não foi efetivo sobre esta fração. Por outro lado, a segunda fração líquida obtida em presença de catalisador apresentou baixo índice de acidez, principalmente aquela obtida nos processos realizados sobre as amostras S025 e S040. Indicando que essas amostras foram mais efetívas no craqueamento secundário do óleo, no qual os ácidos carboxílicos se decompõem gerando hidrocarbonetos. O bio-óleo obtido na segunda fração por ambos os métodos, foi submetido às análises físico-químicas: destilação atmosférica, massa específica, viscosidade cinemática e índice de cetano. Os resultados obtidos indicaram que essas propriedades permaneceram dentro das especificações da ANP para o diesel mineral, tendo o bio-óleo obtido pelo processo de craqueamento termocatalítico propriedades mais adequadas para uso como combustível. A estabilidade térmica do óleo de girassol e dos bio-óleos com e sem a presença de catalisadores foi avaliada utilizando as técnicas TG/DTG/DTA nas razões de aquecimento de 5, 10, 15 e 20(°C.min") em atmosfera de N2. Os resultados obtidos indicaram que os bio-óleos apresentam baixas estabilidades térmicas, necessitando, portanto do uso de aditivo melhorador da estabilidade térmica do bioóleo, para, assim, poder aumentar o tempo de prateleira do mesmo. / The use of alternative fuels is gaining prominence worldwide, because beyond petroleum be an exhaustible source of energy, emits large amounts of polluting gases. Proposals have emerged to replace fóssil fuels, among which stand out biofuels from vegetable oils and animal fats. From this context, this work aims to evaluate the thermal stability of sunflower bio-oil, obtained by thermal and thermo-catalytic cracking. Initially the samples of the catalyst were synthesized and characterized by XRD, textural analysis by nitrogen adsorption, XRF, FTIR, TG/DTG/DTA, TPD-NH3, infrared by pyridine adsorption and 31P, 27A1, and 29Si NMR. The results obtained by X-ray diffraction showed that the samples of SAPO-5 have good crystallinity, indicating that the synthesis method used was efficient. The acidity of the catalyst samples at various silicon contents was evaluated by (TPD-NH3) and infrared by pyridine adsorption. For the TPD-NH3 it was verified the presence of two types of acid sites, a weaker which desorbs ammonia at lower temperatures and another stronger which desorbs ammonia at higher temperatures. By means of the pyridine adsorption was detected greater presence of weak Bronsted acid sites for ali samples analyzed, being the S040 sample which presented the highest amount of Bronsted and Lewis sites. The 29Si NMR analysis indicated for ali the samples the presence of more than one type of mechanism incorporation of the silicon to the network of an aluminophosphate, having the SM2 occurred in greater proportion. The thermal and thermo-catalytic cracking of sunflower oil, performed from room temperature to 550°C in a batch reactor with simple distillation system, provided two organic liquid fractions. The first fraction collected in both processes showed higher index of acidity (170 mg KOH/mg of bio-oil), indicating that the catalyst was not effective on this fraction. In contrast, the second liquid fraction showed low index of acidity, particularly those obtained in the processes performed on the samples S025 and S040. Indicating that these samples were more effective in secondary cracking of the oil, in which the carboxylic acids decompose themselves generating hydrocarbons. The bio-oil obtained from the second fraction by both methods, was subjected to physicochemical analyzes: atmospheric distillation, specific mass, kinematic viscosity and cetane. The results indicated that these properties remain within the specifications of ANP for mineral diesel, having the bio-oil obtained by the thermo-catalytic cracking process, properties more suitable for use as fuel. The thermal stability of sunflower oil and bio-oils with and without the presence of catalyst was evaluated using the techniques TG / DTG / DTA in the heating ratios of 5, 10, 15 and 20 ("C.min1) in atmosphere of N2. The obtained results indicated that sunflower oil and bio-oils are of low thermal stabilities, requiring therefore the use of improver additives of thermal stability of bio-oil, and thus be able to increase the shelf life of the same.

An important criteria for optimising hydraulic systems is their size. Especially for tanks and heat exchangers oil parameters as heat capacity and thermal conductivity have a big influence on the size. Additionally, various oils differ in their parameters. Accordingly, the heat capacity and thermal conductivity need to be known. However, little research has been done. Data-sheets usually do not provide any thermal data. In this paper, the thermal conductivity is measured for varying types of hydraulic oils. The thermal conductivity is determined by a newly designed test-rig measuring the radial temperature difference in a tube at a quasi-static state using a constant heat flux. Thus, an overview over the thermal conductivity of different oils is achieved. Based on the results, a comparison between different types of fluid is made.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Increasing oil prices along with the climate change threat have forced governments, society and the energy sector to consider alternative fuels. Biofuel presents itself as a suitable replacement and has received much attention over recent years. Thermochemical conversion processes such as pyrolysis is a topic of interest for conversion of cheap agricultural wastes into clean energy and valuable products. Fast pyrolysis of biomass is one of the promising technologies for converting biomass into liquid fuels and regarded as a promising feedstock to replace petroleum fuels. Corn residues, corn cob and corn stover, are some of the largest agricultural waste types in South Africa amounting to 8 900 thousand metric tonnes annually (1.7% of world corn production) (Nation Master, 2005). This study looked at the pyrolysis kinetics, the characterisation and quality of by-products from fast pyrolysis of the corn residues and the upgrading of bio-oil. The first objective was to characterise the physical and chemical properties of corn residues in order to determine the suitability of these feedstocks for pyrolytic purposes. Secondly, a study was carried out to obtain the reaction kinetic information and to characterise the behaviour of corn residues during thermal decomposition. The knowledge of biomass pyrolysis kinetics is of importance in the design and optimisation of pyrolytic reactors. Fast pyrolysis experiments were carried out in 2 different reactors: a Lurgi twin screw reactor and a bubbling fluidised bed reactor. The product yields and quality were compared for different types of reactors and biomasses. Finally, a preliminary study on the upgrading of bio-oil to remove the excess water and organics inorder to improve the quality of this liquid fuel was performed. Corn residues biomass are potential thermochemical feedstocks, with the following properties (carbon 50.2 wt. %, hydrogen 5.9 wt. % and Higher heating value 19.14 MJ/kg) for corn cob and (carbon 48.9 wt. %, hydrogen 6.01 wt. % and Higher heating value 18.06 MJ/kg) for corn stover. Corn cobs and corn stover contained very low amounts of nitrogen (0.41-0.57 wt. %) and sulphur (0.03-0.05 wt. %) compared with coal (nitrogen 0.8-1.9 wt. % and sulphur 0.7-1.2 wt. %), making them emit less sulphur oxides than when burning fossil fuels. The corn residues showed three distinct stages in the thermal decomposition process, with peak temperature of pyrolysis shifting to a higher value as the heating rate increased. The activation energies (E) for corn residues, obtained by the application of an iso-conversional method from thermogravimetric tests were in the range of 220 to 270 kJ/mol. The products obtained from fast pyrolysis of corn residues were bio-oil, biochar, water and gas. Higher bio-oil yields were produced from fast pyrolysis of corn residues in a bubbling fluidised bed reactor (47.8 to 51.2 wt. %, dry ash-free) than in a Lurgi twin screw reactor (35.5 to 37 wt. %, dry ash-free). Corn cobs produced higher bio-oil yields than corn stover in both types of reactors. At the optimised operating temperature of 500-530 °C, higher biochar yields were obtained from corn stover than corn cobs in both types of reactors. There were no major differences in the chemical and physical properties of bio-oil produced from the two types of reactors. The biochar properties showed some variation in heating values, carbon content and ash content for the different biomasses. The fast pyrolysis of corn residues produced energy products, bio-oil (Higher heating value = 18.7-25.3 MJ/kg) and biochar (Higher heating value = 19.8-29.3 MJ/kg) comparable with coal (Higher heating value = 16.2-25.9 MJ/kg). The bio-oils produced had some undesirable properties for its application such as acidic (pH 3.8 to 4.3) and high water content (21.3 to 30.5 wt. %). The bio-oil upgrading method (evaporation) increased the heating value and viscosity by removal of light hydrocarbons and water. The corn residues biochar produced had a BET Brynauer-Emmet-Teller (BET) surface area of 96.7 to 158.8 m2/g making it suitable for upgrading for the manufacture of adsorbents. The gas products from fast pyrolysis were analysed by gas chromatography (GC) as CO2, CO, H2, CH4, C2H4, C2H6, C3H8 and C5+ hydrocarbons. The gases had CO2 and CO of more than 80% (v/V) and low heating values (8.82-8.86 MJ/kg). / AFRIKAANSE OPSOMMING: Die styging in olie pryse asook dreigende klimaatsveranderinge het daartoe gelei dat regerings, die samelewing asook die energie sektor alternatiewe energiebronne oorweeg. Biobrandstof as alternatiewe energiebron het in die afgope paar jaar redelik aftrek gekry. Termochemiese omskakelingsprosesse soos pirolise word oorweeg vir die omskakeling van goedkoop landbou afval na groen energie en waardevolle produkte. Snel piroliese van biomassa is een van die mees belowende tegnologië vir die omskakeling van biomassa na vloeibare brandstof en word tans gereken as ’n belowende kandidaat om petroleum brandstof te vervang. Mielieafval, stronke en strooi vorm ’n reuse deel van die Suid Afrikaanse landbou afval. Ongeveer 8900 duisend metrieke ton afval word jaarliks geproduseer wat optel na ongeveer 1.7% van die wêreld se mielie produksie uitmaak (Nation Master, 2005). Hierdie studie het gekk na die kinetika van piroliese, die karakterisering en kwaliteit van by-produkte van snel piroliese afkomstig van mielie-afval asook die opgradering van biobrandstof. Die eerste mikpunt was om die fisiese en chemiese karakteristieke van mielie-afval te bepaal om sodoende die geskiktheid van hierdie afval vir die gebruik tydens piroliese te bepaal. Tweendens is ’n kinetiese studie onderneem om reaksie parameters te bepaal asook die gedrag tydens termiese ontbinding waar te neem. Kennis van die piroliese kinetika van biomassa is van belang juis tydens die ontwerp en optimering van piroliese reaktore. Snel piroliese ekspermente is uitgevoer met behulp van twee verskillende reaktore: ’n Lurgi twee skroef reaktor en ’n borrelende gefluidiseerde-bed reaktor. Die produk opbrengs en kwaliteit is vergelyk. Eindelik is ’n voorlopige studie oor die opgradering van bio-olie uitgevoer deur te kyk na die verwydering van oortollige water en organiese materiaal om die kwaliteit van hierdie vloeibare brandstof te verbeter. Biomassa afkomstig van mielie-afval is ’n potensiële termochemiese voerbron met die volgende kenmerke: mielie stronke- (C - 50.21 massa %, H – 5.9 massa %, HHV – 19.14 MJ/kg); mielie strooi – (C – 48.9 massa %, H – 6.01 massa %, HHV – 18.06 MJ/kg). Beide van hierdie materiale bevat lae hoeveelhede N (0.41-0.57 massa %) and S (0.03-0.05 massa %) in vergelyking met steenkool N (0.8-1.9 massa %) and S (0.7-1.2 massa %). Dit beteken dat hieride bronne van biomassa laer konsentrasies van swael oksiedes vrystel in vergelyking met fossielbrandstowwe. Drie kenmerkende stadia is waargeneem tydens die termiese afbraak van mielie-afval, met die temperatuur piek van piroliese wat skuif na ’n hoër temperatuur soos die verhittingswaarde toeneem. Die waargenome aktiveringsenergie (E) van mielie-afval bereken met behulp van die iso-omskakelings metode van TGA toetse was in die bestek: 220 tot 270 kJ/mol. Die produkte verkry deur Snel Piroliese van mielie-afval was bio-olie, bio-kool en gas. ’n Hoër opbrengs van bio-olie is behaal tydens Snel Piroliese van mielie-afval in die borrelende gefluidiseerde-bed reakctor (47.8 na 51.2 massa %, droog as-vry) in vergelyking met die Lurgi twee skroef reakctor (35.5 na 37 massa %, droog as-vry). Mielie stronke sorg vir ’n hoër opbrengs van bio-olie as mielie strooi in beide reaktore. By die optimum bedryfskondisies is daar in beide reaktor ’n hoër bio-kool opbrengs verkry van mielie stingels teenoor mielie stronke. Geen aansienlike verskille is gevind in die chemise en fisiese kenmerke van van die bio-olie wat geproduseer is in die twee reaktore nie. Daar is wel variasie getoon in die bio-kool kenmerkte van die verskillende Snel Piroliese prosesse. Snel piroliese van mielie-afval lewer energie produkte, bio-olie (HVW = 18.7-25.3MJ/kg) en bio-kool (HVW = 19.8-29.3 MJ/kg) vergelykbaar met steenkool (HVW = 16.2-25.9 MJ/kg). Die bio-olies geproduseer het sommige ongewenste kenmerke getoon byvoorbeeld suurheid (pH 3.8-4.3) asook hoë water inhoud (21.3 – 30.5 massa %). Die metode (indamping) wat gebruik is vir die opgradering van bio-olie het gelei tot die verbetering van die verhittingswaarde asook die toename in viskositeit deur die verwydering van ligte koolwaterstowwe en water. Die mielie-afval bio-kool toon ’n BET (Brunauer-Emmet-Teller) oppervlakte area van 96.7-158.8 m2/g wat dit toepaslik maak as grondstof vir absorbante. The gas geproduseer tydens Snel Piroliese is geanaliseer met behulp van gas chromotografie (GC) as CO2, CO, H2, CH4, C2H4, C2H6, C3H8 and C5+ koolwaterstowwe. Die vlak van CO2 en CO het 80% (v/V) oorskry en met lae verhittingswaardes (8.82-8.86 MJ/kg).