• Energy Research

Digestate, a nutrient-rich substance, is a potential resource of income in biogas plants. It can be utilized as a soil amendment and solid biofuel due to containing inorganic and organic compounds. However, concerning the environmental regulations, there is a requirement for further processes, including hydrothermal carbonization (HTC). Regarding the selection of optimum conditions from the experimental data, this study proposes the energetic yield as the performance indicator from the techno-economic viewpoint, taking solid load and relative equipment size comparison into account as well as the heating value of hydrochar. The energetic yield is the energy content in hydrochar as the heating value per unit mass of reactor inlet, MJ/kg reactor inlet. Among the investigated data for various digestates, the optimum feedstock and conditions were HTC agricultural residue (with 5.02 Energetic yield MJ/kg reactor inlet) at 200 °C and the residence time of 1 h with 30 % solid load based on the energetic yields, i.e. selected for process simulation. This study also investigates required experimental data for enabling mass balance and simulation models. In addition to yield and proximate analysis of feedstock and hydrochar, the characterization of process water is important for representing the dissolved organics. The available data influences the accuracy and closure of elemental mass balances for process simulation. In addition, this study also investigates simulation aspects for producing hydrochar with 20 % moisture content as well: the impact of property method on energy balance, the heat of reaction compared to the literature values, and heat integration concepts. SRK, PSRK, NRTL, and IDEAL methods reported the same value, −122 kW, as the heat duty of the reactor. This value corresponds to −1.46 MJ/kg dry solid and −1.74 MJ/kg dry-ash-free solid inlet as the heat of reaction.

Abstract The main purpose of this paper is the study of elemental mercury adsorption phenomena on a commercially available activated carbon in different oxygen/nitrogen streams. A laboratory-scale apparatus with a fixed bed was used to adsorb elemental mercury vapors in an oxygen/nitrogen stream (synthetic gas). Temperature was varied from 90 to 150 °C. The inlet gas stream was a nitrogen/oxygen mixture with oxygen partial pressures varying from 4.9 to 99.3 kPa, in this gas stream elemental mercury vapors was added spanning the mercury concentration from 0.3 to 3 mg/m 3 . A commercial activated carbon (Darco G60 from BDH) was utilized as sorbent. The experiments led to the determination of the breakthrough curves for the fixed bed. Saturation data allow determining the adsorption isotherms for the temperatures tested, at the different oxygen partial pressures investigated. Experiments showed that the presence of oxygen in the gas phase increases the adsorption capacity of the sorbent and the higher the oxygen concentration the higher the adsorption capacity; however an unusual trend of the adsorption capacity as a function of the temperature was observed, suggesting the occurrence of different phenomena. In order to explain this trend a set of ad hoc experiments was realized pre-treating the carbon in oxygen/nitrogen gas phase and performing the adsorption of mercury in a nitrogen gas phase. These experiments allow the definition of a new model that accounts for the phenomena occurring during mercury adsorption in gas phase containing oxygen. Eventually, the model results well fit the experimental findings.

Accelerated solvent extraction (ASE) was used for the extraction of carotenoids from pre-treated biomass of Dunaliella salina microalgae. The total carotenes and lutein were extracted using different solvents i.e., acetone, chloroform: methanol (C:M) in the ratio of 1:1, ethanol, and hexane. The effects of various experimental parameters, such as temperature (20, 40, 60 and 80 °C), pressure (50 and 100 bar) and static time (2 cycles of 5 and 10 minutes) on the ASE extraction efficiency were investigated systematically. The properties of the solvent and the extraction temperature were found to be the most important parameters affecting the ASE extraction efficiency of thermolabile natural compounds. Moreover, 99% recovery of total carotenes was achieved during extraction with hexane solvent at 40 °C, 100 bar and 2 cycle of 10 minutes. While solvent mixture of C:M was suitable for lutein extraction and resulted 92% recovery at 20 °C, 100 bar and 2 cycle of 10 minutes. Proceedings of the 27th European Biomass Conference and Exhibition, 27-30 May 2019, Lisbon, Portugal, pp. 112-118

The production of biofuels from renewable sources is a major challenge in research. Methanol, ethanol, dimethyl ether (DME), synthetic natural gas (SNG), and hydrogen can be produced from syngas which is the result of the gasification of biomasses. Syngas composition varies according to the gasification technology used (such as fixed bed reactors, fluidized bed reactors, entrained flow reactors), the feedstock characteristics, and the operating parameters. This paper presents a review of the predominant biomass gasification technologies and biofuels obtained from syngas by biomass gasification.

Astaxanthin and lutein, antioxidants used in nutraceutics and cosmetics, can be extracted from several microalgal species. In this work, investigations on astaxanthin and lutein extraction from Haematococcus pluvialis (H. pluvialis) in the red phase were carried out by means of the supercritical fluid extraction (SFE) technique, in which CO2 supercritical fluid was used as the extracting solvent with ethanol as the co-solvent. The experimental activity was performed using a bench-scale reactor in semi-batch configuration with varying extraction times (20, 40, 60, and 80 min), temperatures (50, 65, and 80 °C) and pressures (100, 400, and 550 bar). Moreover, the performance of CO2 SFE with ethanol was compared to that without ethanol. The results show that the highest astaxanthin and lutein recoveries were found at 65 °C and 550 bar, with ~18.5 mg/g dry weight (~92%) astaxanthin and ~7.15 mg/g dry weight (~93%) lutein. The highest astaxanthin purity and the highest lutein purity were found at 80 °C and 400 bar, and at 65 °C and 550 bar, respectively.

Haematococcus pluvialis microalgae in the red phase can produce significant amounts of astaxanthin, lutein, and fatty acids (FAs), which are valuable antioxidants in nutraceutics and cosmetics. Extraction of astaxanthin, lutein, and FAs from disrupted biomass of the H. pluvialis red phase using carbon dioxide (CO2) in supercritical fluid extraction (SFE) conditions was investigated using a bench-scale reactor in a semi-batch configuration. In particular, the effect of extraction time (20, 40, 60, 80, and 120 min), CO2 flow rate (3.62 and 14.48 g/min) temperature (50, 65, and 80 °C), and pressure (100, 400, and 550 bar.) was explored. The results show the maximum recovery of astaxanthin and lutein achieved were 98.6% and 52.3%, respectively, at 50 °C and 550 bars, while the maximum recovery of FAs attained was 93.2% at 65 °C and 550 bars.

The analytical model of the effect of Lorentz forces on enhancing, by 2 orders of magnitude, hydrogen production from water molecules in bulk iron oxide pellets is studied in this paper. This model is verified by experimental data. Dropping water molecules on the surface of an iron oxide pellet results in releasing oxygen ions, due to the existing dangling bonds at relatively elevated temperatures. These ions can be directed from the surface inward, toward the bulk of the iron oxide, due to Lorentz forces perpendicular to the surface of the magnetic pellet, thus permitting new oxygen ions to be released from water molecules. These Lorentz forces are generated by the interaction between an in-plane magnetic induction of proper orientation and an in-plane applied electric field. The oxygen ion mobilization is enabled due to the substantial amount of oxygen vacancies in the bulk of the iron oxide and is being analytically modeled as a drift-diffusion mechanism, dominated by a Lorentz force-driven drift. This process remains active as long as the paths of oxygen ion mobilization toward the inner part of the iron oxide pellet are active. The same effect should also occur in other nonstoichiometric metal oxides, provided that proper Lorentz forces are applied on the corresponding oxygen ion carriers.