Διεργασίες ενεργειακής αξιοποίησης βιομάζας για εφαρμογές θέρμανσης και ψύξης

Πολλές πρόσφατες μελέτες έχουν επικεντρωθεί στη θερμικά προκατεργασμένη λιγνοκυτταρινούχο βιομάζα με σκοπό την υποκατάσταση των ορυκτών καυσίμων. Οι μελέτες αυτές ασχολήθηκαν με την αποδοτικότερη χρήση των ανανεώσιμων πηγών ενέργειας, για την διασφάλιση βιώσιμων πρότυπων στην παραγωγή και στην κατανάλωση, πετυχαίνοντας έτσι την εκπλήρωση των στόχων με αρ. 7 και αρ. 12 της Βιώσιμης Ανάπτυξης σύμφωνα με την ατζέντα των Ηνωμένων Εθνών για το 2030. Η χρήση ανανεώσιμων πηγών ενέργειας και ιδιαίτερα της βιομάζας είναι σημαντική λόγω των οικονομικών συντελεστών, καθώς η χρήση χαμηλού κόστους πηγών ενέργειας είναι πιο ελκυστική, ενισχύοντας έτσι τη διατήρηση ενός καθαρού περιβάλλοντος. Οι θερμικές εφαρμογές είναι οι πιο συνηθισμένες και καθιερωμένες χρήσεις της βιομάζας παγκοσμίως. Έχουν αναπτυχθεί αρκετά συστήματα θέρμανσης και ψύξης, με βάση τη βιομάζα, τα οποία είναι εμπορικά διαθέσιμα και οικονομικώς ανταγωνιστικά. Η βιομάζα χρησιμοποιείται με διάφορους τρόπους για την θέρμανση. Τα συστήματα θέρμανσης καλύπτουν ένα ευρύ φάσμα οικιακής θέρμανσης, από μια μονοκατοικία με λέβητες λίγων kW, έως εγκαταστάσεις λεβήτων πολλών kW στη βιομηχανία και την τηλεθέρμανση. Οι θερμικές μονάδες μεγάλης ισχύος μπορούν να συνδυάσουν τα ‘κύκλα ισχύος’ για την συμπαραγωγή θερμότητας και ηλεκτρικής ισχύος (CHP). Καινοτόμες τεχνολογίες όπως είναι ο Οργανικός Κύκλος Rankine (ORC) και η αεριοποίηση, μας προσφέρουν επίσης μια αποτελεσματική συμπαραγωγή. Η παρούσα διατριβή συμβάλλει στην έρευνα αυτή διερευνώντας την αύξηση της Ανώτερης Θερμογόνου Δύναμης (HHV) του άχυρου κριθαριού και σιταριού, μέσω της υγρής και της ξηρής φρύξης, για να χρησιμοποιηθούν αυτά ως στερεό καύσιμο σε συστήματα θέρμανσης και ψύξης. Συγκεκριμένα, στη διαδικασία της υγρής φρύξης διερευνάται η επίδραση του χρόνου, της θερμοκρασίας και της συγκέντρωσης του οξέος. Επιπλέον, για την προσαρμογή των πειραματικών δεδομένων εφαρμόστηκαν καινοτόμα κινητικά μοντέλα χρησιμοποιώντας έναν παράγοντα σοβαρότητας (Severity Factor, Rο) ο οποίος συνδυάζει την επίδραση του χρόνου αντίδρασης, της θερμοκρασίας και τηςσυγκέντρωσης του οξέος, στην περίπτωση μιας μη ισοθερμοκρασιακής διεργασίας. Ειδικότερα, η δυνατότητα βελτίωσης της HHV του άχυρου κριθαριού πραγματοποιήθηκε με (i) Ξηρή φρύξη, η οποία καλείται και απλά φρύξη, σε κλίβανο, και (ii) Καταλυόμενη από Οξύ Υγρή Φρύξη (ACWT), ή όξινη υδρόλυση ή υδροθερμική επεξεργασία καταλυόμενη από οξύ, που πραγματοποιήθηκε σε αντιδραστήρα διαλείποντος έργου τύπου αυτοκλείστου 3,75 L Parr 4553. Επίσης, μελετήθηκε το άχυρο σιταριού όσον αφορά την βελτίωση της HHV. Σε όλες τις περιπτώσεις, χρησιμοποιήθηκε θερμιδόμετρο Parr 1341 Plain Jacket Bomb για τη μέτρηση της HHV των δειγμάτων. Επίσης, τα δείγματα μελετήθηκαν με τη χρήση τηςτελικής (Ultimate) και προσεγγιστικής (Proximate) ανάλυσης, καθώς και με μικροσκόπιο ηλεκτρονικής σάρωσης (SEM).Όσον αφορά την προκατεργασία με ACWT, εφαρμόστηκαν δύο διαφορετικές προσεγγίσεις προσομοίωσης: (α) ο συνδυασμένος συντελεστής σοβαρότητας (CSF) και (β) η μεθοδολογία επιφανειακής απόκρισης (RSM) σύμφωνα με τον σχεδιασμό των πειραμάτων (DoE) κατά Box – Behnken. Εξετάστηκαν οι παράμετροι της ACWT, όπως η συγκέντρωσητου θειικού οξέος (SA), η θερμοκρασία και ο χρόνος. Όσον αφορά στην προκατεργασία με ξηρή φρύξη, μελετήθηκαν διάφορες πειραματικές συνθήκες, χρησιμοποιώντας πολλούς συνδυασμούς θερμοκρασίας και χρόνου σε έναν κλίβανο (Nuve Muffle Furnace). Επιπλέον, εφαρμόστηκαν καινοτόμα κινητικά μοντέλα για την προσαρμογή των πειραματικώνδεδομένων χρησιμοποιώντας τον CSF, ο οποίος συνδυάζει την επίδραση της θερμοκρασίας και του χρόνου στη διεργασία της φρύξης. Συμπερασματικά, η προκατεργασία με ACWT και ξηρή φρύξη των άχυρων κριθαριού και σιταριού αύξησε σημαντικά την HHV, στις βέλτιστες συνθήκες προκατεργασίας, με αποτέλεσμα την παραγωγή στερεού καυσίμου προερχόμενου από βιομάζα, το οποίο κρίθηκε κατάλληλο για χρήση σε συστήματα θέρμανσης και ψύξης, στο πλαίσιο της έννοιας της κυκλικής οικονομίας μηδενικών αποβλήτων.

Optimum torrefaction range for Macaw husks aiming its use as a solid biofuel

Biomass feedstock is broadly available in many countries and a significant amount of residual biomass comes from agriculture and forest crops. This study aims to identify a consistent criteria for optimize Macaw husks torrefaction process maximizing the energy content and minimizing the mass loss. The optimization criteria is based on the Severity Factor (SF), HHVTorrified and ηSolid-Yield. The energy density (ρEnergy) does not provide consistent and indisputable evidence as an optimization criteria; the same applies to Energy-Mass Co-benefit Index (EMCI) and ηEnergy-Yield. This investigation combined few temperatures (180°C, 220°C, and 260°C) with different residence times (20, 40, and 60 min) and found that the optimum torrefaction range for Macaw husk is 220

Different configurations of the two-step floating catchment area method for measuring the spatial accessibility to hospitals for people living with disability: a cross-sectional study

Background Poor spatial accessibility to hospital services is associated with higher morbidity and mortality rates among people living with disability. Improved methods to evaluate spatial accessibility are needed. This study measured the potential spatial accessibility of people living with disability by applying four configurations of the two-step floating catchment area (2SFCA) method to recommend the best model for use in health services research. Methods 2SFCA and an enhanced version (E2SFCA) were used to measure hospital accessibility for people living with disability. We also developed and embedded a non-spatial severity index into the two 2SFCA models. We used 16,186 records of people living with disability experience to evaluate the methodological performance across 68 neighbourhoods of the city of Ahvaz, located in south-western Iran. The models’ performance were measured through correlation of the four accessibility scores with the distance to closest hospital for each neighbourhood centroid. Results Among the four models used to measure spatial accessibility, the E2SFCA integrated with the severity index displayed the best performance. Most people with disabilities lived in neighbourhoods located in the South-western and central areas of the city. Interestingly, south-western neighbourhoods had poor hospital accessibility score and were identified as unmet need areas for access to health services. Conclusions Inclusion of the severity factor in the E2SFCA improved access measurements. Identifying areas with poor levels of hospital accessibility can help policymakers design tailored interventions and improve accessibility to hospital-based care in urban settings for people living with disability.

Phenomenological Modeling of Formic Acid Fractionation of Sugarcane Bagasse by Integration of Operation Parameters as an Extended Combined Severity Factor

In order to more conveniently simulate and optimize the solubilization of sugarcane bagasse components during formic acid (FA) fractionation, an extended combined severity factor (CSFext) was defined to integrate various operation parameters as a single factor. Two phenomenological models based on Arrhenius and Logistic equations were further used to describe the phenomenological kinetics. Different data-processing methods were compared to fit the severity parameters and model constants. Both Arrhenius-based and Logistic-based models show satisfying fitting results, though the values of Arrhenius-based CSFext (A-CSFext) and Logistic-based CSFext (L-CSFext) were somewhat different under the same fractionation condition. The solubilization of biomass components increased with CSFext, but two distinct stages could be observed with inflection points at A-CSFext of 42 or L-CSFext of 43, corresponding to bulk and residual solubilization stages, respectively. For the enzymatic hydrolysis of cellulosic solids, the highest initial enzymatic glucan conversion (EGC@6h) was obtained at A-CSFext of 39–40 or A-CSFext of 40–41; however, for a long hydrolysis period (72 h), relatively high glucan conversion (EGC@72h) was observed at A-CSFext of 42–43 or A-CSFext of 43–44. Post-treatment for deformylation with a small amount of lime could help to recover the cellulose digestibility.

Oral anticoagulant therapy at hospital admission associates with lower mortality in older COVID-19 patients with atrial fibrillation. An insight from the Covid Registry

Funding Acknowledgements Type of funding sources: None. OnBehalf the GeroCovid Investigators Introduction. Atrial fibrillation (AF), the arrhythmia most frequently diagnosed in older patients, associates with serious, thrombo-embolic, complications and high mortality. COVID-19 severely affects aged subjects, determining an important prothrombotic status. Purpose. Aim of this study was to evaluate mortality-related factors in older AF patients with COVID-19. Methods. We included 806 in-hospital COVID-19 patients aged 60 years or more hospitalized between March 1st and June 6th 2020 and enrolled in a multicenter observational study. Results. The prevalence of AF was 21.8%. In-hospital mortality was higher in the AF group (36.9 vs. 27.5%; p = 0.015). Among AF patients, those who survived were younger (81 ± 8 vs. 84 ± 7 years; p = 0.002), had a lower CHA2DS2-VASc score (3.9 ± 1.6 vs. 4.4 ± 1.3; p = 0.02) and were more frequently treated with oral anticoagulants at admission (63.1 vs. 32.3%; p < 0.001) than those who died in hospital. At multivariable logistic regression analysis, lower age (p = 0.042), a better functional profile (p = 0.007), less severe COVID-19 manifestations at admission (p = 0.001), and the use of Vitamin K antagonists (OR = 0.16, 95%CI: 0.03-0.84; p = 0.031) or DOACs (OR = 0.22, 95%CI: 0.08-0.56; p = 0.002), compared to antiplatelet therapy or no treatment at all, were associated with a lower chance of in-hospital death. Conclusions. AF is a prevalent condition and a severity factor in older COVID-19 patients. Advanced age, dependency and severe clinical manifestations of disease characterized older AF subjects with a worse prognosis. Interestingly, pre-admission anticoagulant therapy correlated positively with in-hospital survival.

EFFECT OF THE RIVET-HOLE TOLERANCE ON THE STRESS-SEVERITY FACTOR

This work is focused on a quantitative procedure for estimating the generally unfavourable effects that incorrectly drilled holes, characterized by the initial clearance between a rivet and a hole, have on the fatigue life of riveted joints. The solution is based on an analytical approach using the stress-severity-factor concept. An experimental programme with riveted-joint specimens characterized by low-load transfer factors was realized in the Czech Aerospace Research Centre (VZLU) test lab under constant amplitude loading. The holes for rivet joints with 4-mm diameters were prepared with the clearance in a range of 0.0–0.16 mm. Force-controlled riveting was applied using a constant pressure force to form the driven head. To prevent fretting events between the joined parts, their anodized contact surfaces were lubricated with MOLYKA, plastic grease with molybdenum disulphide and graphite. The experimental data showed that the load-transfer factor and the fatigue life depend on the initial clearance between a rivet and a hole. The presented procedure introduced the hole-filling factor, integrated in the stress-severity-factor concept as a function of the initial clearance between a rivet and a hole.

INFLUENCE OF AGE AND MORPHOLOGICAL FEATURES ON THE CLINICAL MANIFESTATIONS AND TREATMENT EFFICACY OF HEMANGIOMAS IN CHILDREN

Background. Infantile hemangioma (IH) is a neoplasm that is most common in childhood. Morphologically, hemangiomas are divided into superficial, deep and mixed, focal, segmental, indeterminate and multifocal. The course of IH includes phases of rapid growth followed by slow involution. The degree of involution of hemangioma is variable. Hemangiomas can lead to the appearance of permanent deformities of soft tissues or functional disorders, especially when localized on the face and vital structures. Clinical heterogeneity of hemangiomas creates significant difficulties for physicians in resolving issues of treatment tactics. Specific characteristics of the clinical behavior of hemangiomas of various morphological types can be crucial in the choice of management tactics for such patients. Objectives. The aim of the work is to study the effect of different morphological types of hemangioma in children on the effectiveness of treatment of age-related clinical features. Subjects and Methods. The study group consisted of 100 children in age from birth to 6 years who have hemangiomas of different morphological types and localizations and did not receive previous treatment. All research participants for hemangioma severity scale (HSS), hemangioma activity scale (HAS), visual analogue scale (VAS) before, during and after treatment were scored. Serum levels sFas/sFasLs before and during treatment evaluated. Results. With increasing the child’s age, the indicator as for HAS reliably decreases for all types of hemangiomas. In all types of hemangiomas predominantly an active growth took place. An abortive growth in 10% of patients was noted. For focal hemangiomas, the indicator of sFas decreases with age, and for multifocal hemangiomas it increases. In both cases, there is an increase in the sFasL indicator with increasing age of the child. In our study, in age group before 1 year in the factor structures, “age” factor was considered to be the main one and manifested by a decrease in the activity of hemangioma with an increase in the age of the child. Among children over 1 year age, during the course of treatment, the greatest contribution the “hemangioma severity factor”, the influence of which leads to a decrease in the cosmetic effect of hemangioma treatment against the background of its high severity and an increase in the indicator of apoptosis inhibition of sFas. The influence of the “treatment efficacy” factor leads to a decrease in its cosmetic effect and an increase in the severity of the manifestations of hemangioma against the background of blocking the manifestations of apoptosis. Conclusions. When starting treatment of hemangioma in the early stages, the cosmetic effect increases significantly. A decrease in sFasL in the younger age group may indicate a decrease or absence of apoptosis processes, which is clinically expressed by active proliferation. An increase in sFas in the older age group (over a year old) may indicate a blockage of apoptosis processes and, as a consequence, a slow regression of hemangioma.