This study aims at valorizing the residual aqueous phase from hydrothermal carbonization (HTC) of Sicilian agrowastes in order to enhance the hydrochar recovery, positively affecting the process energy balance. Process waters (PW) obtained from HTC and co-HTC using orange peel waste and fennel plant residues were used as recycled solvent in experiments carried out at the temperatures of 180 and 230 ◦C. The results showed that an additional hydrochar formation was promoted during recirculation of solvent, leading to average increments of solid mass yield of 10.5 wt% for tests conducted at 180 ◦C and 3.9 wt% for 230 ◦C. After five consecutive recirculation phases in co-HTC runs, the hydrochar yield increased up to 18.2 wt%. The low H/C and O/C atomic ratios values, found after recirculation, indicate that organic acids, accumulated in the PW, may catalyze the process and promote the biomass deoxygenation by boosting dehydration and decarboxylation. The recovered PWs from conversion steps with deionized water were also carbonized in absence of the solid feedstock in order to quantify their contribution in hydrochar formation during recirculation and thus the synergistic interactions. After recirculation, energy recovery averagely augmented by more than threefold, showing that the proposed strategy could significantly improve the sustainability of HTC.

Recirculation of hydrothermal carbonization (HTC) process water (PW) has been revealed as an effective strategy to promote the recovery of lost dissolved organics in the spent solvent. However, the role of operating parameters such as temperature, time and solid load during recirculation needs to be clarified and better investigated in order to achieve a successful PW valorization. In this paper, the effects of different reaction conditions during HTC with PW recirculation were studied by using orange peel waste as feedstock. The results showed that strong synergistic interactions occurred between the biomass and the recycled solvent, leading to a hydrochar mass yield increase between 0.5 and 11 wt% on a dry basis (d.b.), according to the reaction conditions. PW recirculation, especially at low conversion severity and solid load, increased hydrochar carbon content while drastically reduced the oxygen fraction. The reason was probably related to promoted dehydration and decarboxylation. As result, carbon and energy yields were respectively increased by 26.1 % and 27.0 %, on average. The energy balance outcomes showed that the energy recovery rose up to 8 times by recycling PW compared to phases with deionized water as HTC solvent.

This work explores the valorization of residual olive mill wastewater as a process aqueous medium for cohydrothermal carbonization (co-HTC) of typical Sicilian agro-wastes (tangerine and orange peel wastes). Co-HTC experiments were carried out at 180 and 220 ◦C to assess the interaction between the feedstocks. Synergistic effects increased the yield of hydrochar and gas phases while antagonism altered the formation of aqueous products. Compared to the expected value, hydrochar yield was increased by 37 wt%, on average, while the interaction effect on gas phase was weaker (+23 wt%, on average) and increased with temperature. Both the retention of unhydrolyzed primary char and the recapture of secondary char phases from process water enhanced the hydrochar recovery in different ways according to feedstock nature and co-HTC conditions. On the basis of hydrochars characterization through elemental analysis and surface functionality, the degree of carbonization was significantly improved after co-HTC due to promoted dehydration and decarboxylation reactions. As result, co-hydrochars exhibited a moderately higher energy content and a greater thermal stability compared to samples obtained from HTC of individual substrates. Co-hydrochars also retained relatively high amounts of nutrients such as phosphorus, potassium and calcium, which could enable their use as soil improvers.

In this study fresh carob tree fruits (CF), a very widespread botanical species in the Mediterranean basin, were hydrothermally carbonized (HTC) at 200, 230, 250, and 280 °C for a residence time of 0.5 h and a biomass-towater mass ratio (B/W) of 0.1. CF hydrochars were characterized in terms of elemental and proximate analysis for their possible valorization as solid biofuels. Increased reaction severity showed a decrease in solid mass yield recovery but an increase in hydrochar fixed carbon content and energy density. Hydrochars showed a high heating value (HHV) up to about 27.7 MJ/kg with a corresponding energy densification ratio (EDR) higher than 150%. CF hydrochars were also investigated as potential carbon-dense material as fillers in bio-plastic. Therefore, the CF hydrochar particles, at different concentrations, have been introduced in biopolymer matrices, such as PolyButylene Adipate Terephthalate (PBAT), by melt mixing and the rheological and mechanical behaviour of the bio-composites have been evaluated considering their potential application in the packaging sector.

Recirculation of process water (PW) from hydrothermal carbonization (HTC) has revealed as an effective strategy for the residual aqueous phase valorization in order to make the process energetically more efficient while reducing its environmental footprint. The effects of temperature, solid load and consecutive conversion phases on PW recirculation were assessed by using Ferula Communis plant residues as feedstock in HTC experiments. Recirculation of solvent promoted strong synergistic interactions between biomass and PW aimed at increasing hydrochar mass recovery. Hydrochar yield increased by 4-12 wt% on a dry basis (d.b.) according to reaction conditions. Biomass degradation was catalyzed by the reactive intermediates dissolved in the PW. The energy balance results showed that the energy recovery almost doubled by recycling PW when compared to the experiments carried out using only deionized water as HTC solvent.

The aim of this paper is to develop an analytical model of a single and two parallel configuration silicon carbide power MOSFETs utilizing the state-space equations to offer a straightforward solution with reduced computational efforts, still maintaining high accuracy. The analytical model of each single power device is directly obtained from technical specifications. Although the main target is to investigate the unbalanced phenomena in paralleled SiC devices, the proposed approach additionally provides a practical model for testing electric drive configurations, control strategies and fault tolerant drives. The analytical model has been validated through simulation implemented in Matlab/Simulink, comparing transient commutation and computational times with SPICE models.