No abstract

The objective of this research was to study the fast pyrolysis of sisal residue, performed in a pilot unit with a fluidized bed reactor. The tests were carried out by varying the flows of nitrogen (8−14 N m 3 /h), biomass (10.33−25.95 g/ min), and temperature (450−550°C). The experimental planning technique was used to identify the number of tests and the influence of operational variables on the bio-oil yield. One of the highest H 2 /CO (2.16) ratios was found from the eighth test on, which was an appropriate value for the production of methanol and liquid biofuels. All bio-oil samples produced were characterized, and the results showed that the sisal residue bio-oil is different from other bio-oils reported in the literature. It has high viscosity at room temperature, with a pour point of 55°C and average molecular weight of 414.2 g/mol. In addition, phenolic species completely prevail in relation to the other monomeric components. The biochar obtained is an amorphous, fine powder. Despite the porosity, its specific surface area is lower than of commercial activated carbon.

The exponential growth of electric and hybrid vehicles in the last five years forecasts a waste problem when their batteries achieve end-of-life. Li-ion batteries for vehicles have been assembled using materials from natural resources (as Li, Fe, Al, Cu Co, Mn and P). Among them, LiFePO4 cathode materials have demonstrated advantages such as charge–discharge cycles, thermal stability, surface area and raw materials availability (against Ni and Co systems). Due to the performance, LFP batteries stand out in heavy duty fleet, achieving 90% of new energy buses in China. To achieve the circular economy, the recycling of LFP batteries may be carried out by pyrometallurgy (thermal processing), hydrometallurgy (aqueous processing) or both in combination. Comparatively, hydrometallurgical processing is more advantageous due to its low energy consumption and CO2 emissions. In addition, Li may be recovered in a high-pure grade. This work is a literature review of the current alternatives for the recycling of LFP batteries by hydrometallurgy, comparing designed processes in the literature and indicating solutions towards a circular economy. The major recycling steps of hydrometallurgy routes such as pre-treatments, leaching and purification steps will be gathered and discussed in terms of efficiency and environmental impact.

Biomass pyrolysis usually occurs in a fluidized bed reactor formed by sand, biomass, and biochar. Dynamics this fluidization differs from that of literature because the biomass is converted continually in biochar. In this study, a series of experiments have been carried out for ternary mixtures of sand, sisal residue, and biochar, varying the compositions and particle size. The tests were based on two simplification hypotheses (steady state and room temperature) due to fast biomass transformation in bed and low Van der Waals force to large particles. The dynamic characteristics determined included the bed pressure drop and bed fluctuation. The single and combined effects of particle size and composition on the final fluidization velocity (Uff) and particle segregation (S) have been analyzed using response surface (RSM). The Uff and S minimum values were found when the variables were in the smallest particle size and composition levels. New correlations were developed for predicting the values of Uff. The error from measured values when using the new correlation was 7.6%, while the literature equation was 9.7%. The present correlations predicted reasonably well predicted the Uff of ternary mixtures in the fast pyrolysis bed.

In a previous study, a statistical model was developed using the experimental planning technique for evaluating the influence of its variables on fluidization velocity. In this study, we investigated the Vasconcelos-statistical model (VSM) in data representation, considering fluidization with and without segregation. The methodology used was based on the simulation of the fluidization velocity of nine binary systems, comprising sand, and eight biomasses published by six authors. In addition, the results obtained using VSM were compared with those obtained using five other models, reported by different authors, but adjusted to the experimental data of these biomasses. The result obtained by the proposed models mainly indicated a discrepancy between the experimental and calculated fluidization velocities. VSM, using only three variables (particle size, particle diameter, and biomass mass fraction), yielded results of smaller discrepancy values in all simulations (2.23–12.51%), as opposed to the other comparative models, which presented more significant numbers of variables. Thus, VSM is defined as one of the most interesting models for predicting the fluidization velocity of several biomasses.