Estudo da pirólise de misturas de resíduos de plásticos, pneus e biomassa

Dissertação para obtenção do Grau de Doutor em Engenharia Química e BioquímicaAs sociedades modernas encontram-se fortemente dependentes de fontes de energia fósseis, o que poderá ter consequências graves num futuro próximo se não forem adotadas medidas que permitam diminuir esta situação. Outra vertente problemática, atual, é a elevada produção de resíduos e o seu deficiente reaproveitamento. O presente trabalho procurou integrar o tratamento de três tipos de resíduos pelo processo de pirólise com o objetivo da sua valorização. A adição de uma mistura dos principais plásticos presentes nos resíduos sólidos urbanos permitiu melhorar a pirólise de biomassa e de borracha de pneu em condições de pirólise descontínua. Obtiveram-se, deste modo, produtos líquidos com conteúdo energético apreciável, semelhante ao do gasóleo de aquecimento, bem como gases com poder calorífico superior ao do gás de cidade e sólidos com conteúdo energético superior ao de alguns carvões. Foi estudada a influência das condições operatórias no rendimento e composição das frações de produtos obtidos (gases, líquidos e sólidos). Verificou-se que o teor de plástico na mistura inicial foi a condição que mais afetou os resultados, favorecendo a formação de líquidos e de hidrocarbonetos gasosos. O aumento do tempo de reação favoreceu a produção de gases e o seu teor em alcanos. O acréscimo deste parâmetro também promoveu a produção de líquidos mais leves e com maior teor de alcanos. O aumento da temperatura de reação diminuiu o rendimento da fração líquida promovendo o de sólidos e de gases e aumentou a produção de alcanos nos gases. Obtiveram-se líquidos com menor resíduo da destilação e maior teor de alcanos. A pressão inicial favoreceu a produção de alcanos gasosos. O estudo da otimização das condições experimentais, através da implementação de um plano fatorial de ensaios, revelou que a produção de líquidos totais (líquidos diretamente decantados da autoclave mais os líquidos adsorvidos nos sólidos, recuperados por extração) é maximizada por uma temperatura de reação de 350ºC, uma pressão inicial de azoto de 0,2 MPa e um tempo de reação de 30 minutos obtendo-se nestas condições um rendimento de 91,2%, enquanto que a produção máxima dos líquidos decantados ocorre quando se utiliza uma temperatura de 450ºC, 18 minutos de reação e a pressão de 0,8 MPa de azoto inicial, produzindo 55,3% de líquidos decantados. Numa última fase do trabalho foi realizado um estudo cinético das reações ocorridas durante o processo de pirólise. Foi proposto um modelo de mecanismo que melhor se ajustou aos resultados experimentais e calculados os parâmetros cinéticos dos diferentes passos envolvidos.FCT-MCES através da bolsa nº SFRH / BD / 41406 / 200

Recovery of wastes by pyrolysis: effect of experimental conditions

This work aimed to study the recovery of three types of waste by the process of pyrolysis: biomass, plastics and used tyres. The effects of experimental conditions in products yield and composition were studied. The increase of reaction time increased alkane content both in gas phase from 53% to 70% v/v and in liquid fraction from 48% to 60% w/w. The rise of reaction temperature led to a decrease of liquid yield (from 82% to 73% w/w), which was followed by the increase of solids and gases. The increase of reaction temperature also allowed the increase of the alkane content in gas phase from 39% to 70% v/v. The increase of initial pressure did not lead to appreciable variations in product yields or composition. The parameter that most affected products yield and composition was plastics content on the wastes initial mixture. The enhancement of this parameter increased liquids yield from 33% to 92% w/w, at the expenses of solids and gases contents and also decreased aromatics contents from 52% to 28% w/w

Study of the slow batch pyrolysis of mixtures of plastics, tyres and forestry biomass wastes. Effect of experimental conditions in the liguid compounds

In this work was studied the effect of experimental conditions in the production of liquid compounds from slow batch pyrolysis of mixtures of plastics, tires and pines wastes. The major compounds formed were toluene, ethylbenzene, and linear alkanes from C5 to C10 (each reaching yields around 5% w/w of the initial waste mixture). The pyrolysis reaction time and temperature improved the production of those species, while decreasing heavier alkanes formation. An increase of plastics content in waste mixture seemed to favour the production of lighter alkanes, although this effect was not as notorious as the ones just mentioned. The styrene production decreased regularly with the decrease of tyres content in the mixture. Autoclave initial pressure variation did not seem to affect significantly the formation of the major compounds

Co-pyrolysis of pre-treated biomass and wastes to produce added value liquid compounds

ABSTRACT: It is imperative to find novel environmental friendly liquid fuels to be used in the long distance transportation sector. Pyrolysis of wastes may have an important role in the near future to attain this goal. Biomass pyrolysis has also been widely studied by several researchers, but besides the potentialities of such technology, the bio-oil obtained still has to overcome some challenges related to its unsuitable properties to be used in conventional combustion devices. On the contrary, plastics pyrolysis produces oils, whose main compounds are hydrocarbons, thus they can be used in conventional engines without complex and high cost upgrading processes. Thus, co-pyrolysis of plastics blended with biomass may be a suitable option to produce alternative liquid fuels from wastes. The biomass selected for this study was Eucalyptus globulus wastes, because it has been mostly used in the pulp and paper industry in Iberian Peninsula, which has produced high amounts of wastes. On the other hand, PE (polyethylene) was the plastic chosen, because of the huge wastes amounts generated per year. With the aim of facilitating biomass pyrolysis and to increase the production of liquid compounds with suitable properties to be used as fuels, an alternative to the conventional biomass pyrolysis was studied. First eucalyptus wastes were pre-treated by diluted acid hydrolysis, which removed the hemicellulose fraction, produced added value sugar-based compounds and upgraded the remaining solids to better conditions for pyrolysis. Several pathways were studied, including untreated and pre-treated eucalyptus, blended with different contents of PE wastes. The best technical option is the co-pyrolysis of pre-treated eucalyptus mixed with PE, as the highest liquids yields were produced. However, this process needs to be further studied and the economic viability of the overall process still needs to be proven.info:eu-repo/semantics/publishedVersio

Co-liquefaction of wastes and coal mixtures to produce added value liquid compounds

ABSTRACT: Nowadays there is an increasing need to find alternative fuels to reduce the dependency on imported ones and to decrease the negative environmental impact of wastes accumulation. Plastics are an important components of urban biowaste, thus their conversion into liquid fuels, in mixtures with other solid fuels still remains an important research goal. After the large experience obtained from coal gasification, it was found that co-liquefaction of coal and wastes may be a good solution to produce liquid fuels and raw materials for several industries. Co-liquefaction of coal blended with biomass gave unfavourable results, but co-liquefaction of coal mixed with PE (polyethylene) wastes led to encouraging results. The results obtained showed that the rise of PE content in coal blends led to an increase in liquid yield. As the main objective was the formation of liquid products, the mixture of coal with 50 wt% of PE was selected, as substantial total liquid yields were obtained, while using significant coal content. This blend was used to study the effect of initial hydrogen pressure, reaction temperature and time on products yields, using Response Surface Methodology (RSM) approach. Liquid yields were most affected by reaction temperature and pressure. The rise of temperature decreased liquid yields, while pressure had a positive effect, but the interaction between these two parameters showed a negative influence. Theoretical equations were used to calculate total and direct liquids yield (%daf). Total liquids are the sum of the liquids directly recovered from the autoclave (direct liquids) and the liquids extracted from the solid product. Both the theoretical model and the experimental results showed that the highest total liquids yields were obtained at 380 ºC, 1.4 MPa and 90 minutes.info:eu-repo/semantics/publishedVersio

Effect of experimental conditions on co-pyrolysis of pre-treated eucalyptus blended with plastic wastes

ABSTRACT: Eucalyptus has been largely used in the pulp and paper industry in Iberian Peninsula, due to its fast growth and high productivity. This eucalyptus utilisation has generated high amounts of wastes, including leaves, branches and stumps. Hence, these wastes were selected for the co-pyrolysis studies to produce liquid fuels or raw materials. As an alternative to the conventional biomass pyrolysis, biomass was pre-treated under mild acidic conditions to obtain valuable sugar-rich stream to be used in fermentation and the solids rich in lignin were mixed with PE (polyethylene) wastes to be used in co-pyrolysis. The pre-treatment process seems to have weakened initial macromolecular structure of eucalyptus wastes and thus might have helped chemical bonds breakdown during co-pyrolysis. The results obtained so far have shown that PE presence seems to have favoured the biomass conversion. The effect of experimental conditions using Response Surface Methodology (RSM) was studied. There was a good agreement between theoretical and experimental data. The highest liquid yield (78 % wt) was obtained at 380 ºC and for the reaction time of 20 min. These conditions led to the lowest gases yield (7 % wt) and also to the lowest solids yield (14 % wt).info:eu-repo/semantics/publishedVersio

Streamlining the biodesulfurization process: development of an integrated continuous system prototype using Gordonia alkanivorans strain 1B†

ABSTRACT: Biodesulfurization is a biotechnological process that uses microorganisms as biocatalysts to actively remove sulfur from fuels. It has the potential to be cleaner and more efficient than the current industrial process, however several bottlenecks have prevented its implementation. Additionally, most works propose models based on direct cultivation on fuel, or batch production of biocatalysts followed by a processing step before application to batch biodesulfurization, which are difficult to replicate at a larger scale. Thus, there is a need for a model that can be adapted to a refining process, where fuel is being continuously produced to meet consumer needs. The main goal of this work was to develop the first bench-scale continuous biodesulfurization system that integrates biocatalyst production, biodesulfurization and fuel separation, into a single continuous process, taking advantage of the method for the continuous production of the biodesulfurization biocatalysts previously established. This system eliminates the need to process the biocatalysts and facilitates fuel separation, while mitigating some of the process bottlenecks. First, using the bacterium Gordonia alkanivorans strain 1B, continuous culture conditions were optimized to double biocatalyst production, and the produced biocatalysts were applied in batch biphasic biodesulfurization assays for a better understanding of the influence of different factors. Then, the novel integrated system was developed and evaluated using a model fuel (n-heptane + dibenzothiophene) in continuous biodesulfurization assays. With this system strain 1B surpassed its highest biodesulfurization rate, reaching 21 μmol h−1 g−1. Furthermore, by testing a recalcitrant model fuel, composed of n-heptane with dibenzothiophene and three alkylated derivatives (with 109 ppm of sulfur), 72% biodesulfurization was achieved by repeatedly passing the same fuel through the system, maintaining a constant response throughout sequential biodesulfurization cycles. Lastly, the system was also tested with real fuels (used tire/plastic pyrolysis oil; sweet and sour crude oils), revealing increased desulfurization activity. These results highlight the potential of the continuous biodesulfurization system to accelerate the transition from bench to commercial scale, contributing to the development of biodesulfurization biorefineries, centered on the valorization of sulfur-rich residues/biomasses for energy production.info:eu-repo/semantics/publishedVersio

Slow pyrolysis of cork granules under nitrogen atmosphere: by-products characterization and their potential valorization

ABSTRACT: Cork granules (Quercus suber L.) were slowly pyrolyzed at temperatures between 400-700 degrees C and under N-2 flow. While preserving its structure, some cells of the cork biochar became interconnected, allowing such carbon residue to be used as templates for manufacturing ceria redox materials. The pyrolytic char morphology was similar to that of the natural precursor. The produced cork biochar belonged to Class 1 (C > 60%) and possessed a high heating value of 32 MJ kg(-1). Other pyrolysis-derived compounds were identified and quantified through GC-FID and GC-MS analyses. The yield of gases released during cork pyrolysis was strongly dependent on the temperature used due to the thermal decomposition reactions involved in the degradation of cork. In particular, rising pyrolysis temperature from 500 to 700 T resulted in reducing the total hydrocarbon gases from 74 to 24 vol%. On the other hand, the yield of H-2 increased from 0 to 58% by increasing the pyrolysis temperature from 400 to 700 T. Due to the presence of suberin in cork, the composition and yield of bio-oil could be regulated by the pyrolysis temperature. Cork bio-oil was found to consist of long-chain hydrocarbons (from C11 to C24). The bio-oil resulting from the slow pyrolysis of cork residues is suitable as an appropriate feedstock for producing aliphatic-rich pyrolytic biofuels or as a source of olefms. Overall, the findings of this study suggest that Quercus suber L. could be a promising feedstock for biochar and biofuel production through the pyrolytic route and could contribute to the environmental and economic sustainability of the cork production industry.info:eu-repo/semantics/publishedVersio

Production of liquid compounds by co-pyrolysis of different pre-treated biomasses mixed with plastic wastes

ABSTRACT: As an innovation to conventional biomass pyrolysis to produce liquid biofuels, different types of biomass wastes were pre-treated by autohydrolysis, prior to pyrolysis. Eucalyptus forestry waste, corn cobs agricultural residue, and miscanthus (an energy crop) were autohydrolysed. Autohydrolysis led to valuable sugar-rich stream that may be used in fermentation and to solids rich in lignin that were pyrolysed. Pyrolysis of autohydrolysed eucalyptus led to an increase in liquids yields of 24 % in relation to untreated eucalyptus, as autohydrolysis weakened initial macromolecular structure and thus helped chemical bonds breakdown during pyrolysis. However, similar pyrolysis liquid yields were obtained by autohydrolysed or untreated corn cobs and miscanthus, thus feedstock composition is an important issue. Nevertheless, the production of added value products by autohydrolysis may still justify this pre-treatment. Otherwise, more severe pre-treatments of these biomasses might improve co-pyrolysis as it happened with eucalyptus. As polyethylene (PE) is easier to pyrolyse than biomass and greatly favours the production of liquid hydrocarbons, autohydrolysed and untreated biomass was mixed with PE wastes to be used in co-pyrolysis. The rise of PE content in the blend clearly favoured the production of liquid products of pre-treated and untreated biomass. 75 %wt. of PE in the blend led to liquid yields of 72 %wt. for untreated eucalyptus and of 82 %wt. for autohydrolysed eucalyptus.info:eu-repo/semantics/publishedVersio

Effect of Type of Biomass used in the Hydrothermal Liquefaction of Microalgae on the Bio Crude Yields and Quality

Hydrothermal liquefaction (HTL) is an energy-efficient technology that converts biomass with high moisture content, such as lignocellulosic material and aquatic biomass, into bio-oil which can be used as a precursor in the production of renewable biofuels. The current state of technology is mostly at a laboratory scale with relatively low Technology Readiness Levels (TRL). Most HTL research takes place in batch reaction systems, but there is growing interest in scaling up the technology through the use of continuous units. The process is influenced by several factors and operational parameters, which affect the performance of the process in terms of production and bio-oil quality. HTL is highly dependent on the type of biomass used. The main advantages in relation to other thermochemical processes is the possibility of using wet biomass, avoiding the high cost of the drying process. In this work several types of biomasses were studied, different types of micro algae (i. e. Spirulina, Chlorella Vulgaris, algae grown in industrial effluents), and grass. Growing microalgae has a significant cost in the production process of liquid biofuels. So, it was also tested algae cultivated in industrial effluents which has advantages from an economic and environmental point of view. Also, the grass wastes, have high moisture content and so its adequate to be process in HTL. In all the tests, four different products were obtained: gases, aqueous and organic (biocrude) products and solids. All these fractions were characterized to suggest their most favourable application. The gases were mainly composed of Hydrogen, Oxygen, Carbon Monoxide, Carbon Dioxide and Hydrocarbons until C4. Bio oil composition was the parameter most affected by biomass type. So, when microalgae were used, it was observed higher content of nitrogenous compounds, like pyrroles, indoles, pyrazines and other nitrogen-containing compounds, probably formed from the protein fraction of the algae. In all the bio-oils it was also detected the presence of oxygenated compounds, such as ketones, esters, phenols, fatty acids, alcohols, that maybe were produced from the lipids and carbohydrates. Hydrocarbons, including alkanes, alkenes, alkynes and aromatics compounds were also present. The composition of the biomass used has a higher effect on the bio-oil composition, so it is important an extensive characterization of the feedstock in order to select the best raw material to be used in HTL process depending on the intended application. This paper analyses the effect of biomass composition in the HTL to assess its viability to be used to produce biofuels or valuable chemicals