Redesign and structural optimization of a rotary vacuum dryer (RVD) powered with vapor

La empresa Corteva Agriscience es una multinacional encargada de la producción de herbicidas, fungicidas, entre otros productos relacionados con el agro. Actualmente se ubicada en el municipio de soledad, Atlántico. Planteó una problemática respecto a los tiempos de secado durante la elaboración de Mancozeb (fungicida), que toma alrededor de 3 horas y quieren reducirlo al menos a 2 horas y 30 minutos. El secado se realiza por medio de un RVD (Rotary Vacuum Dryer) el cual está conformado por una carcasa estática cubierta por una chaqueta y un eje rotativo que cuenta con cintas y ramificaciones, el proceso es llevado al vacío para disminuir el punto de ebullición del agua, dado que el material a secar no puede superar los 80°C. El fenómeno que rige el proceso es la transferencia de calor ocasionada por el vapor que fluye a través de la chaqueta y el eje. La empresa como posible solución propone aumentar la presión del vapor través del eje, pero teme por los esfuerzos ocasiona dicho cambio. Durante el planteamiento de alternativas, analizamos la sugerida por la empresa y mediante cálculos de transferencia de calor apreciamos que el coeficiente global de transferencia de calor se mantiene alrededor de unos 1.95 kW/m2k por más significativo que sea el cambio en la presión, por lo cual los tiempos serán similares. Por otro lado, haciendo una revisión exhaustiva del estado de la técnica proponemos hacer pequeños cambios al equipo teniendo en cuenta el factor económico, entre ellos la implementación de sellos mecánicos para mantener la hermeticidad dentro del equipo y evitar las infiltraciones, modificar las condiciones del fluido que pasa a través del eyector para mejorar el vacío, implantación de rodamiento lineal en un extremo y conos truncados para el soporte de las ramificaciones. Por último, el cambio del eje o modificación de la geometría del eje, para ampliar el área de transferencia de calor sin afectar significativamente el volumen de trabajo, muy costosa.Corteva Agriscience Company is a multinational that produced of herbicides, fungicides, among other products related to agriculture. Currently located in the municipality of Soledad, Atlántico. They have a problem regarding the drying times during the production of Mancozeb (fungicide), which takes around 3 hours and they want to reduce it to at least 2 hours and 30 minutes. Drying is carried out by means of an RVD (rotary vacuum dryer) which is made up of a static casing covered by a jacket and a rotary axis that has tapes and branches; the process is carried out under vacuum to decrease the boiling point of water, since the material to be dried cannot exceed 80 ° C. The phenomenon that governs the process is the heat transfer caused by the steam that flows through the jacket and the shaft. The company as a possible solution proposes to increase the pressure of the vapor through the axis, but the time caused by the efforts causes such a change. During the proposal of alternatives, we analyze the one suggested by the company and through heat transfer calculations we appreciate that the global coefficient of heat transfer remains around 1.95 kWm2kno matter how significant the change in the pressure, so the times will be similar. On the other hand, making an exhaustive review of the state of the art, we propose to make small changes to the equipment taking into account the economic factor, including the implementation of mechanical seals to maintain the tightness within the equipment and avoid infiltrations, modify the fluid conditions that passes through the ejector to improve the vacuum, implantation of a linear bearing at one end and truncated cones to support the branches. Finally, the change of the axis or modification of the axis geometry, to expand the heat transfer area without significantly affecting the work volume, very expensive

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London