Exploring thermochemical routes for argan shells valorization
The present thesis addresses, as indicated in the title, the valorization of an agricultural waste, argan shells, via the thermochemical pathway.<br />This Ph.D. study has been developed at the Aragón Institute of Engineering Research (I3A), affiliated with the Universidad de Zaragoza-Spain, i...
| Autores: | , , |
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| Tipo de recurso: | tesis de maestría |
| Estado: | Versión publicada |
| Fecha de publicación: | 2023 |
| País: | España |
| Institución: | Universidad de Zaragoza |
| Repositorio: | Zaguán. Repositorio Digital de la Universidad de Zaragoza |
| OAI Identifier: | oai:zaguan.unizar.es:129535 |
| Acceso en línea: | http://zaguan.unizar.es/record/129535 |
| Access Level: | acceso abierto |
| Palabra clave: | química de monomeros altas temperaturas espectroscopia de masas química ambiental |
| Sumario: | The present thesis addresses, as indicated in the title, the valorization of an agricultural waste, argan shells, via the thermochemical pathway.<br />This Ph.D. study has been developed at the Aragón Institute of Engineering Research (I3A), affiliated with the Universidad de Zaragoza-Spain, in the Thermochemical Processes Group (GPT). The topics investigated at the GPT can be divided into two main lines: (i) the fuel conversion and minimization of pollutant emissions and (ii) the production of biofuels and bioproducts from biomass and waste, where the current work is framed. In this research area, the main objective consists of finding the appropriate means for sustainable upgrading of industrial and agroforestry residues into add-valued products.<br />During the last three decades, the group has worked on the thermochemical processing of many types of materials, such as sewage sludge, animal manure, wood, plastics, meat and bone meal, as well as some agricultural wastes like wheat straw, sugar cane bagasse and fruit shells, by torrefaction, pyrolysis, gasification or hydrotreatment. For instance, almond shells, an abundant waste in Spain, were gasified, and their behavior was outlined in a previous work of the GPT (Bilbao et al., 1995). In the same way, the pyrolysis of cashew nutshells has more recently been studied at the facilities of the GPT, showing the great fuel potential of the charcoal and the liquid produced (Ábrego et al., 2018). The process prototype was scaled up into a 50 kg fixed-bed reactor mounted in Bobo-Dioulasso, Burkina Faso (Plaza et al., 2019), thus providing new avenues for the sustainable development of the mentioned region. Hence, the idea of valorizing another kind of fruit shell, specifically argan shells, emerged from the same perspective of promoting its use locally in the Moroccan region where the argan tree grows. Unlike other nutshells, such as almond or cashew, there were very few bibliographical antecedents about argan shells characterization and its thermochemical conversion when this Ph.D. project was started (by February 2018), except for some studies about activated carbon production and hard carbon for batteries (Boujibar et al., 2018; Dahbi et al., 2017; Elmouwahidi et al., 2012; Ennaciri et al., 2014). More recently, some of the thermal characteristics and the combustion behavior of this residue were involved in other studies developed by Moroccan researchers (Rahib et al., 2019a; Rahib et al., 2019b).<br />In the present Ph.D. work, the argan shells were characterized in depth, and their thermochemical treatment was experimentally studied through different routes in order to explore different potential alternatives for the valorization of this waste.<br />Torrefaction appears as the softest thermochemical treatment in terms of the temperature range applied to the material. In most cases, this treatment is used to increase the energetic value, improve the carbon content and ease the grinding of the raw material for the sake of storage and transportation (Brachi et al., 2017; Medic et al., 2012). In the present study, the torrefaction of argan shells was performed in an auger reactor under two different temperatures, with an exhaustive characterization of the products. Afterward, air-steam gasification of raw shells and of the torrefied material was experimentally tested in a fluidized-bed at the operational conditions pre-established by chemical thermodynamic equilibrium calculations. The behavior of argan shells in both processes was experimentally compared to another biomass more used and explored in thermochemical processes (pine residues).<br />In order to extend the knowledge on the thermochemical upgrading of argan shells, the pyrolysis process was also experimentally studied at three different temperatures in a fixed-bed reactor. The process was followed by other post-treatments intending to find sustainable applications and end-uses for the generated products. In particular, the produced biochar was used as feedstock to produce high-quality activated carbon (by physical activation in two different reactors using CO2 as an agent). On the other hand, the bio-oil obtained from the pyrolysis process, as well as the lignin fraction extracted from the shells by a soda semi-chemical pulping process, were hydrothermally processed. The liquid products were further upgraded to obtain potential antioxidant additives, whose activity was tested by blending with biodiesel and measuring the improvement of its oxidation stability.<br /> |
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