Valorización de residuos orgánicos como nuevos combustibles sólidos de biomasa
Authors:   , Espuelas Zuazu Sandra 
Published: April 2023

This thesis focuses on the valorization of two industrial wastes, which currently have no effective valorization ways, as solid biomass fuels for the generation of clean energy. In order to valorize these wastes, a methodology structured in six phases has been developed to study the waste and its different valorization routes, as well as to detect the possible wastes generated after the valorization process. Firstly, the spent coffee grounds (SCG) has been valorized by manufacturing briquettes under low-pressure and low-temperature conditions, formed with SCG and xanthan gum and guar gum as binders. The briquettes were manufactured at room temperature, at 10%, 15%, 20%, 25% and 30% humidity, with 8, 10 and 12 MPa of compaction pressure and with 5 and 10% doses of each binder. Several tests were carried out to characterize the briquettes, firstly, to determine the capacity to manufacture functional briquettes, dry density, durability and water absorption tests were carried out. Finally, chemical tests were carried out to determine their potential as solid fuels: ultimate and proximate analysis and combustion test. Combination of 10% of xanthan, 15% of moisture, at 12 MPa, reached the highest dry density, 0.819 g/cm3 . The combination of 5% of xanthan, 30% of moisture, compacted at 12 MPa was the most durable with a loss of mass of 3.9%. No relationships were established among water absorption and binder type, binder dosage, manu- facturing moisture or compaction pressure. The lowest water absorption value, 0.25%, corresponded to the combination with 5% of xanthan, 30% of moisture, compacted at 10 MPa. The lowest heating value achieved by SCG was 25,399 J/g. Guar 5% and 10% combinations achieved 24,398 J/g and 24,321 J/g respectively. Xanthan gum 5% and 10% dosages attained 24,450 and 23,503 J/g. Binder decreased volatiles, increased fixed carbon content and decreased nitrogen content. Guar gum decreased SCG nitrogen content by 15.92% for the 5% and by 16.92% for the 10% dosage combinations, respectively. Xanthan nitrogen reduction attained 13.43% for the 5% and 14.43% for the 10% of dosage. The raw SCG ash production was 0.66%. This value increased to 0.81% and 0.97% with 5% and 10% of xanthan gum, meanwhile guar decreased it to 0.57% and 0.52%, at 5% and 10% of dosage. The second waste studied is cellulose insulation powder (CFP). This waste lacks any method f valorization because of its boron salt content. In this case, it was recovered by manufacturing pellets with lignosulfonate and sugar production waste. Several tests were carried out to characterize the pellets. Firstly, to determine the ability to manufacture functional pellets, dry density, durability and water absorption tests were carried out. In addition, chemical tests were carried out to determine their potential as solid fuels: proximate and ultimate analysis and combustion test. Finally, the ashes obtained after the combustion of the different pellets manufactured were characterized. Raw CFP showed good ability in its pelletization and durability in the range of 15–30% of moisture content. The pellet’s density decreased as water content increased. Binders increased the pellet’s length before and after the durability test. Binders also increased the CFP pellet’s water absorption, demonstrating a potential decrease in durability against environmental factors. Binders also decreased the lower heating value. Ultimate analysis showed a slight Nitrogen increase in both binder combinations that could potentially raise the pollutant NOx combustion emissions. All the combinations showed adequate combustion characteristics, but binders increased ash production. Additives decreased the CFP volatile matter content and increased the fixed carbon, which could facilitate a more stable combustion. DTA curves showed a mass loss rate decrease in the volatile stage for the binder combinations, which also could be considered as an indicator of a more stable combustion. The ashes’ chemical compositions when analyzed by XPS showed boron contents oscillating between 10.03% and 16.42%, demonstrating the possibility of recovering them from the combustion ashes.