This work deals with the design of a galvanically isolated converter of continuous analog signals and the design of a galvanically separated converter of digital TTL signals to HTL signals. The device is complemented by a STM32 microprocessor, which ensures the connection of analog input and output. The result of the work is the circuit structure of individual units, the results of simulations of important units, complete data for the production of device and measured values of individual units.

An experimental study on the effect of fuel mixing on the products resulting from hydrothermal liquefaction (HTL) was conducted. The feedstocks used were kraft lignin (KL), GROT (GT) and microalgae cultivated in wastewater (MA). Three sets of mixtures were prepared, each containing two types of feedstocks with a 1:1 ratio: KLGT, MAKL, and MAGT. The experiments were performed using a pilot-scale continuous HTL-system. Elemental analysis CHNO and thermogravimetric analysis were used to determine the ultimate and proximate composition of the samples. Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) was used to further analyse the elemental distribution on the hydrochars’ surface. The co-liquefaction effect (CE) was evaluated by comparing the experimental results found for the mixtures with the theoretical values calculated as the average of the respective pure components. The results showed that the yield of light oil was not significantly affected for any mixture. However, the mixtures containing KL showed a lower yield of heavy oil than the predicted value, while a higher yield was found for MAGT. All heavy oils had higher carbon content than expected from the predicted values. Every mixture had a significantly larger yield of hydrochar than what was expected. The increased yield of hydrochar for KLGT was insufficient to compensate for the loss of heavy oil and thus the overall product yield was decrease showing antagonistic interactions in the mixture. The hydrochar from MAGT had the highest ash content, and upon closer inspection with SEM/EDS it showed a much larger phosphorus content than any other hydrochar, even compared to the predicted value. This suggests that an interaction between MA and GROT causes the hydrochar to bind more contaminants and enables it to collect more ash than what would have been achieved from liquefying the components individually. Thus, MAGT showed synergetic effects overall, MAKL had increased carbon recovery but at the cost of heavy oil yield making in a poor choice for HTL, and KLGT showed antagonistic effects in the form of lower yield of biocrude and overall recovery of products. The study highlights that co-liquefaction can potentially have a larger impact on the hydrochar than it does on the biocrude, and that evaluation of hydrochar should be included when examining co-liquefaction

El presente trabajo de investigación surge para dar una respuesta alternativa a las tecnologías actuales de eliminación y/o aprovechamiento de los subproductos de origen animal (SANDACH) y revalorizar estos subproductos. Los residuos cárnicos generados en los mataderos, en los procesados de alimentos y los animales que fallecen en las granjas son considerados SANDACH y están sujetos a una legislación estricta que regula su manipulación y gestión. Entre otros aspectos, la legislación clasifica a los subproductos según su potencial peligrosidad y define los posibles usos y gestión como residuos. Los de mayor peligrosidad (Categoría 1) deben ser incinerados, enterrados previa esterilización y marcado o utilizados en la producción de biodiesel, biogás o en procesos de combustión. Los subproductos de peligrosidad media (Categoría 2), además de los usos anteriores, pueden aprovecharse para fabricar abono y sólo los SANDACH de baja peligrosidad (Categoría 3) pueden transformarse mediante renderizado en piensos para animales de compañía y animales de peletería. Esta tesis estudia la viabilidad del proceso de obtención de bio-combustible mediante licuefacción hidrotérmica de los subproductos de origen animal y de sus productos de renderizado. La tesis está estructurada en tres partes. La primera parte brinda una visión general de los subproductos de origen animal en la actualidad (Capítulo 1) así como una introducción a los fundamentos de la conversión de biomasa y la licuefacción hidrotérmica (Capítulos 2 y 3). La segunda parte describe el proceso experimental llevado a cabo a escala laboratorio (Capítulo 4), los estudios comparativos realizados entre licuefacción hidrotérmica y pirólisis de SANDACH y productos de renderizado (Capítulo 5), y el análisis de la influencia de los parámetros de reacción para la licuefacción de esta materia prima (Capítulos 6 y 7). La tercera y última parte de este trabajo presenta los estudios relacionados con el escalado a planta piloto (Capítulo 8) y la evaluación del análisis de ciclo de vida y costes del proceso (Capítulo 9). Este trabajo de tesis es altamente interdisciplinario por ser una combinación de ingeniería química, química orgánica, inorgánica, física y analítica.

Microalgae are a diverse group of oxygenic photosynthetic microorganisms which show great promise as a source of biofuel. However, significant challenges still remain before microalgae can be considered a viable source of biofuel. The main current challenges are nutrient sourcing and recycling as well as downstream processing. The algal cell wall and especially the presence of an algaenan cell wall in some Chlorophyte algae could be an important variable in determining downstream processing costs but not much comparative research has been done to elucidate this. The first part of the present study focuses on the recently isolated alga Pseudochoricystis ellipsoidea (Trebouxiophyceae) and its improvement and assessment for biofuel production. Random mutagenesis and FACS screening protocols were developed for the isolation of pigment and cell wall mutants but despite considerable efforts no suitable mutants could be identified in the first half of this project. Two 500 L raceway ponds as well as an algal growth room and bubble column bioreactors were set up to facilitate algal research at the University of Bath and assess the performance of P. ellipsoidea in realistic culture conditions. P. ellipsoidea showed a maximum growth of 1.53 divisions day-1 in semi-open raceway ponds, resistance to contamination and a 30% lipid content, making it particularly suitable for raceway pond cultures. In the second part of this project six species of Chlorophyte (“green”) algae, three of which produced algaenan, were compared for suitability to growth in anaerobic digestate and municipal wastewater as well as cell wall strength, permeability and suitability to hydrothermal liquefaction. We found that anaerobic digestate was a good medium for the growth of all species independently of autoclaving and that non-autoclaved wastewater was a very challenging medium. Algaenan production did not affect cell disruption by ultrasonication but growth stage and cell wall thickness did. Lipid extraction kinetics by chloroform/methanol were greatly affected by algaenan, meaning that this material is relatively impermeable to organic solvents. Cell wall thickness, cell volume and lipid content also had an effect on lipid extraction kinetics but this was only measurable after 180 minutes of extraction. 8 Hydrothermal liquefaction showed high solid and low oil yields, very low sulphur (≤0.1 %) as well as a 1.1 % -1.8 % nitrogen content which is significantly lower than most algal HTL studies to date. This suggests that stationary stage algae are more difficult to process but give a cleaner biocrude and reduce the loss of nitrogen through incorporation in the oil. Significant opportunities for optimisation still exist in the HTL process.