Pressure drop, mechanic deformation, stabilization and scale-up of wheat straw fixed-beds during hydrothermal pretreatment : experiments and modeling

PeerReviewe

GPE2018 - Green Process Engineering

Hydrothermal fractionation is a well-known process for lignocellulosic biomass upgrading. It is based on the continuous treatment of biomass with hot pressurized water, converting the biomass major components (hemicellulose, cellulose and lignin) into soluble compounds. Thus, it is one of the most promising options to produce chemicals and energy from biomass since it only requires water and temperature. However, it is a highly complex process that involves a great deal of physical phenomena: biopolymer and oligomer cleavage, sugar production and degradation, acid releasing, homogeneous acid catalysis, solid-liquid mass transfers and porosity changes. For this reason, the development of a comprehensive kinetic model for biomass hydrothermal fractionation is a difficult matter. Despite these burdens, several modelling options that go from the simplest option, a first order kinetic model, to deeper and complete studies, can be found in the literature. These models are able to reproduce the experimental data of different biomasses in both, packed bed and batch reactors. Nonetheless, they are generally used for just one reactor or for one specific biomass, like spruce or wheat bran. Thereby, this work was aimed at developing an overall model for hemicellulose extraction, validating it with data from different packed bed reactors and for completely different biomasses. Additionally, this model included the whole set of physical phenomena. So, a novel reaction path way with all the physico-chemical process involved in the both phases, the liquid and the solid, was proposed. The model was obtained applying a mass balance for each compound in this mechanism and it was solved applying advanced numerical methods (orthogonal collocation over finite elements and Runge-Kutta with 8th order of convergence). Regarding kinetics, auto-catalytic expressions were selected since they have been demonstrated to be a suitable option to simulate quick changes in concentration profiles. On the other hand, the data of the hydrothermal fractionation were taken from 4 different reactors and using 3 biomasses (holm oak, wheat straw and catalpa) were used (0.1, 3, 6 and 40L). The temperature range was between 140 ºC and 215 ºC to focus the study on the hemicellulose extraction and the residence time was fixed around 5 min to promote extraction without degrading the hydrolysate. The model reproduced the experimental behaviour with average deviations between 6 and 50%. It is worth mentioning that the higher deviations were obtained when also the uncertainty of the experimental measure of the compounds was high. The simulated profiles included: oligomers, hexoses, pentoses, acetic acid, degradation products and pH. Furthermore, it is worth mentioning that the fractionation was mainly controlled by the soluble oligomers production and their hydrolysis kinetics. Therefore, it could be concluded that, for the cases studied, if temperature and pH profiles inside two different reactors are similar, their global behaviour will be also the same, independently of the biomass studied and reactor properties. Finally, it should be remarked that all the calculated parameters had physical meaning

Biorefinery cascade processing for creating added value on tomato industrial by-products from Tunisia

Background: In today’s consumer perception of industrial processes and food production, aspects like food quality, human health, environmental safety, and energy security have become the keywords. Therefore, much effort has been extended toward adding value to biowastes of agri-food industries through biorefinery processing approaches. This study focused, for the first time, on the valorization of tomato by-products of a Tunisian industry for the recovery of value-added compounds using biorefinery cascade processing. Results: The process integrated supercritical CO2 extraction of carotenoids within the oil fractions from tomato seeds (TS) and tomato peels (TP), followed by a batch isolation of protein from the residues. The remaining lignocellulosic matter from both fractions was then submitted to a liquid hot water (LHW) hydrolysis. Supercritical CO2 experiments extracted 5.79% oleoresin, 410.53 mg lycopene/kg, and 31.38 mg β-carotene/kg from TP and 26.29% oil, 27.84 mg lycopene/kg, and 5.25 mg β-carotene/kg from TS, on dry weights. Protein extraction yields, nearing 30% of the initial protein contents equal to 13.28% in TP and 39.26% in TS, revealed that TP and TS are a rich source of essential amino acids. LHW treatment run at 120–200 °C, 50 bar for 30 min showed that a temperature of 160 °C was the most convenient for cellulose and hemicellulose hydrolysis from TP and TS, while keeping the degradation products low. Conclusions: Results indicated that tomato by-products are not only a green source of lycopene-rich oleoresin and tomato seed oil (TSO) and of protein with good nutritional quality but also a source of lignocellulosic matter with potential for bioethanol production. This study would provide an important reference for the concept and the feasibility of the cascade fractionation of valuable compounds from tomato industrial by-products

Thyroid Malignancy Markers on Sonography Are Common in Patients With Benign Thyroid Disease and Previous Iodine Deficiency

OBJECTIVES: The purpose of this study was to evaluate the characteristics of benign thyroid nodules on sonography and ultrasound elastography in a population exposed to iodine deficiency.METHODS: We conducted a prospective systematic evaluation of preoperative thyroid sonography and elastography in patients assigned for surgical excision of benign thyroid nodules. Two experienced sonographers performed all sonographic and elastographic examinations. Thyroid nodules were evaluated by 7 generally accepted sonographic malignancy risk markers and assigned an elasticity score on elastography. The final diagnosis of a benign thyroid nodule was based on histopathologic analysis of resected thyroid gland tissue.RESULTS: We evaluated 232 thyroid nodules in 105 patients (86 women and 19 men). In total, 57% of the examined nodules had 1 or 2 malignancy risk markers present, and 24% did not have any markers present. A solid nodule larger than 15 mm was the most common malignancy risk marker observed (63%), followed by low elasticity (33%), microcalcifications (26%), and hypoechogenicity (15%). In an analysis stratified according to the number of nodules (solitary versus multiple), low elasticity was described more frequently in solitary nodules (61.9% versus 30.4%; P= .004). A large nodular volume was a predictor (P &lt; .05) of microcalcifications and intranodular vascularization, whereas an absent halo sign and a solid nodule were found less frequently in nodules with larger volumes.CONCLUSIONS: Our results show that routine preoperative malignancy risk evaluation of presumably benign thyroid nodules is of little value when performed on patients exposed to iodine deficiency.</p

‘It’s not particularly P.C., you know…’ Women coaches’ performing gender in strength and conditioning

Strength & conditioning (S&C) has become a chief part of athletes’ physiological preparation. Despite S&C’s growing presence across sports, women coaches have been generally marginalised and under-represented. This study explores female S&C coaches’ experiences and coping mechanisms in a male-dominated industry. In doing so, semi-structured interviews with 15 female S&C coaches were conducted. Main themes identified from interview data are: organisational politics, impression management, and humour. The findings suggest that women S&C coaches are often in subservient positions and have to adopt some of the traditional, male-generated sub-cultural practices to fit in. They carefully manage their coaching front stage to generate an impression that is expected and accepted in the given milieu. In their efforts to fit in, women often find themselves in a multiplicity of power matrices which involve a continuous negotiation of gender identity, internal politics and managing sexist banter