Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Prediction of Droplet Size Distribution for High Pressure Homogenizers with Heterogeneous Turbulent Dissipation Rate

Droplet size distribution (DSD) of an emulsion is one of the important properties that affect product quality, stability, appearance, and rheology. Reliable prediction of DSDs in high-pressure homogenizers under various emulsion formulation and processing conditions is still challenging. A zero-dimensional population balance equation (PBE) model was developed to take account of the heterogeneous turbulent dissipation rate through its volume fraction distribution rather than the mean value as the coupling parameter between CFD and PBE. Furthermore, the effect of emulsifier on coalescence was also incorporated through the surface coverage of emulsifier. The model can give satisfactory DSDs under different oil fractions, homogenization pressures, and emulsifier concentrations for the oil-in-water emulsions. Moreover, the predictions were more sensitive to the breakage kernel parameters than to the coalescence ones or the number of daughter droplets. This approach is beneficial to the fast computational product design with less computational cost and reasonable prediction

Hydrodynamics in bubble columns with helically-finned tube Internals: Experiments and CFD-PBM simulation

Experiments and CFD-PBM simulation were performed in this study to investigate the effects of helically-finned tube (HFT) internals on the gas-liquid flow in a laboratory-scale bubble column. Hydrodynamic parameters, including gas holdup, bubble size and flow field as well as turbulence properties, were com-pared for an empty column and other two columns with bare-tube (BT) or HFT internals. We found that bare rods promote the stability of two-phase flow, whereas helical fins destabilize the flow. Meanwhile, the spatial distribution of gas holdup or bubble size becomes more uniform in the presence of HFT inter-nals, whereas liquid velocity or turbulent dissipation rate evidently decreases. The fin-induced spiral movement, flow resistance and bubble accumulation are the mechanisms underlying these experimental observations. Integration of rod and helical fin may be promising for process intensification in bubble columns. (c) 2021 Elsevier Ltd. All rights reserved

Metal Recovery from Hydroprocessing Spent Catalyst: A Green Chemical Engineering Approach

The present study aims to develop an ecofriendly, chelant-assisted extraction methodology for significant recovery of heavy metals (cobalt (Co), molybdenum (Mo)) from hydroprocessing spent catalyst. Ethylene diamine tetraacetic acid (EDTA) was employed for metal mobilization in the extraction process. The possibility of internal and external mass transfer resistance was investigated to improve the diffusion rate of reactants, while kinetic aspects were studied to achieve thermodynamic equilibrium for the process. Percentage distribution of various protonation stages of EDTA was explored to understand the conjugate base and ligand precursor and to improve the effect of reaction pH on extraction efficiency. Extraction of 80.4% Co and 84.9% Mo was achieved at optimum reaction conditions. Selective precipitation of metals was attained according to maximum solubility of metal oxides at different pH regions. Efforts were also made to recycle the recovered EDTA, recovered support material, and extracted metals. Significant metal extraction efficiency (72.7% Co and 76.5% Mo) was observed with recovered EDTA even after the fourth cycle of operation which may provide economic consistency to the extraction process. The extracted metals were impregnated on recovered alumina to synthesize fresh catalyst. Structural analysis of spent catalyst, recovered support material, and synthesized catalyst from extracted metals suggested successful recovery and recycling of metals. This work offers an incentive to the industrial practice for waste minimization, recycling of the extracted metals, and the noncorrosive, ecofriendly approach for metal extraction from spent catalyst

Liquid-liquid extraction system with microstructured coiled flow inverter and other capillary setups for single-stage extraction applications

Process intensification via miniaturization has become an attractive research field for industry and R&D especially for the production of fine chemicals and pharmaceuticals due to enhanced mass and heat transport. Fabrication of helically coiled tubular devices (HCTDs) in micro-scale can further enhance the mass and heat transfer due to the formation of secondary flow profile at laminar flow. Liquid-liquid (L-L) mass transfer performance of different microstructured HCTDs were investigated for slug flow patterns. A complete microextraction system was constructed and characterized including a T-junction (T-mixer) for slug flow generation, HCTDs as residence time units (RTUs), and a continuously working in-line phase splitter for an instantaneous phase separation. RTUs were fabricated by using fluorinated ethylene propylene (FEP) tubes (ID = 1mm). EFCE test system, namely, n-butyl acetate/acetone/water system was chosen as an extraction system for the mass transfer characterization. The total volumetric flow rate and the volumetric flow ratio of aqueous to organic phase were varied in the range of 1-8mLmin-1 and 0.5-2.0, respectively. Effects of residence time, flow ratio, and the generation of secondary flow profile, i.e. Dean vortices on L-L mass transfer were investigated and results were compared with straight capillaries. Results revealed that a certain type of HCTD, i.e. coiled flow inverter (CFI) offers higher extraction efficiencies up to 20% in comparison to straight capillaries at constant residence times. Additionally, it was found that for slug flow patterns, Dean vortices provide enhanced L-L mass transfer compared to Taylor vortices that occur in straight capillaries. A complete, continuously operated microextraction system was developed for single-stage applications, where very small liquid hold-ups and longer residence times are required due to slower mass transfer rates