62 research outputs found
Modelling of Sorption Enhanced Chemical Looping Steam Reforming (SE-CLSR) of Methane in a Packed Bed Reactor
In the sorption enhanced steam methane reforming (SE-SMR) process, hydrogen (H2) can be produced in concentration up to 98 vol. % (dry basis) in a single reactor packed with a mixture of reforming catalyst and carbon dioxide (CO2) sorbent. This is defined as pre-combustion capturing of CO2 and the high purity H2 produced can be used as a fuel for electricity generation, synthesis of ammonia-derived fertilisers, or hydrotreating of naphtha and other heavy gas oil in petroleum refinery. A cyclic operation between the production of H2 and regeneration of CO2 sorbent is required, but the energy demand for the sorbent regeneration is high. A proposed method to decrease this energy demand is to couple SE-SMR with chemical looping (CL), which naturally separates the nitrogen (N2) from the syngas via the highly exothermic cyclic oxidation with air of a metallic material, which acts as the reforming catalyst when reduced (oxygen transfer material or ‘OTM’). The combination of SE-SMR and CL makes the process energy efficient and eliminates the need for (i) high temperature as compared to the conventional steam methane reforming (SMR) process (typical temperature range is 750- 950°C), (ii) the water gas shift (WGS) reactors downstream of the reformer, and (iii) external heating using the natural gas fuel in the reformer. However the H2 generation of a high purity from one reactor operation is intermittent, as part of a cyclic operation, with the reactor alternately operating in Fuel Reactor mode (FR), with fuel and steam feed or Air Reactor mode (AR), with air feed. Adsorption of CO2 shifts the equilibrium of reaction towards more H2 production and ultimately increases the efficiency of the process towards H2 production. Production of H2, CH4 conversion and overall efficiency of the process depend upon many operating parameters. The effects of inlet temperature, reactor pressure, molar steam to carbon ratio (S/C) in the feed, and gas mass velocity on the SE-SMR and the sorption enhanced chemical looping steam reforming (SE-CLSR) of methane processes is reported in this thesis.
The formulation of the SE-CLSR process model requires the modelling of packed bed reactors. This mathematical modelling covers various individual models (sub-models) for; SMR, SE-SMR, OTM reduction and oxidation of reduced OTM. The gPROMS model builder 4.1.0® is used to solve the model equations. In this work, an experimental
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kinetics study and model of SMR process over 18 wt. % NiO/α-Al2O3 catalyst are presented for an adiabatic fixed bed reactor in the temperature range of 300-700°C at 1 bar pressure. The model is validated by comparing the results with the experimental data obtained as part of this work. The simulation results are in excellent agreement with the experimental results. The equilibrium results are generated using Chemical Equilibrium with Applications (CEA) software. The effect of various operating parameters (temperature, pressure and S/C) on the CH4 and water conversion (%) is modelled and compared with the equilibrium values. The mathematical model of SE-SMR was developed based on the industrial operating conditions of temperature and pressure. The 873-973 K was found to be the optimum range of temperature, under the high pressure (30 bar) conditions, for the production of H2 of purity exceeding 85%. The developed model of SE-SMR was validated against the literature data.
The mathematical model of SE-CLSR process was developed under adiabatic conditions. This model is the combination of reduction of catalyst followed by oxidation of the reduced catalyst. The individual models of reduction and oxidation are developed by using kinetic data available in the literature and later on validated with experimental results proposed in the literature. The already developed model of SE-SMR process is combined with the OTM reduction model to mimic the dynamic process occurring in the fuel reactor (FR) system. This FR is combined with air reactor (AR) and the combined model is run for 10 cycles. The sensitivity of the process is studied under the various operating conditions of temperature (873-1023 K), pressure (1-30 bar), molar S/C (2-6) and mass flux of the gas phase (Gs = 2-7 kg m-2 s-1). In this work, the operating conditions used for the production of H2 represent realistic industrial production conditions. The sensitivity analysis demonstrates that the developed model of SE-CLSR process has the flexibility to simulate a wide range of operating conditions of temperature, pressure, S/C and Gs
In the Eyes of the Beholder: Leaders’ Personality and Courageous Followership
Received 10 January 2022 . Accepted 30 August 2022. Published online 10 October 2022.The literature on leadership through the lens of followership does not provide empirical evidence of leaders’ personalities and their perception of subordinates’ courageous followership behaviors. This paper explores the connection between personality and courageous followership. The study sample is 190 school leaders working in the top private schools in Pakistan as regular employees. The responses collected through simple random sampling techniques and Stata 16 software are used for data analysis. Data analysis indicates that leaders having extraversion, agreeableness, consciousness, and openness to intellectual/imagination personality traits perceive their subordinates’ behaviors as courageous followers, whereas the neuroticism personality trait resulted in a negative perception of courageous followership behaviors among Pakistani school leaders. This paper is prominent research in a new direction of leadership through followership. This study recommends emphasizing the development of positive personality traits in leaders so that they can transform their subordinates into courageous followers which is an antidote to toxic leadership
The Al2O3-monolayer sensitivity towards NH3 and PH3 molecule: A DFT Study
The recent theoretical investigation has advocated the Al2O3 monolayer as a stable atomic configuration. This work deals with the interaction of NH3 and PH3 towards this monolayer configuration. Structural and electronic investigation suggests a strong affinity of the monolayer towards the NH3 and PH3 molecules. PDOS analysis reveals hybridization between the molecular orbital of NH3/PH3 and Al2O3-monolayer. The electronic energy bandgap of the Al2O3 monolayer gets reduced by 0.26eV and 0.21eV respectively, on NH3 and PH3 adsorption. In the bandstructure analysis of the Al2O3-monolayer, the energy band dispersion got flattened after the toxic molecular gas (NH3/PH3) adsorption, suggesting strong sensitivity towards the toxicants. Mulliken population analysis witnessed a robust amount of charge transferred from the toxic molecules to the Al2O3-nanosheet. A competency in electrical conductivity and energy-band gap flattening of the NH3/PH3-Al2O3 configurations is an interesting outcome of the present work. All these findings suggest strong sensitivity of the 2D-monolayer for NH3/PH3
Diagnostic Accuracy of Tympanometry for Diagnosis of Fluid the Middle Ears of Children with Otitis Media with Effusion staking Myringotomy as Gold Standard
Objective: To determine the diagnostic accuracy of tympanometry for diagnosing fluid in the middle ears of children with Otitis Media with Effusion taking myringotomy as a gold standard.
Study Design: Cross-sectional study
Place and Duration of Study: Department of ENT & Head and Neck Surgery, Combined Military Hospital, Peshawar Pakistan, from Oct 2018 to Sep 2020.
Methodology: A total of 201 patients who underwent tympanometry followed by myringotomy of aged between 3 to 12 years of either gender were included. All patients underwent tympanometry. After that, myringotomy was carried out through a radial incision in the anteroinferior quadrant using a general inhalational anaesthetic agent. The operative findings at myringotomy were recorded. The presence of fluid on intraoperative findings using myringotomy was considered positive for the presence of fluid in the middle ears of children.
Results: The age range of the patients was from 3-12 years, with a mean age of 7.35±2.41 years. Of these 207 patients,133(64.18%) were males, and 74(35.82%) were females. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of tympanometry for diagnosis of fluid in the middle ears of children with Otitis Media with Effusion taking myringotomy as the gold standard was 85.7%, 86.3%, 89.4%, 81.7% and 85.9% respectively.
Conclusion: This study concluded that the diagnostic accuracy of tympanometry for the diagnosis of fluid in the middle ears of children with Otitis Media with Effusion is quite high
Measuring routine childhood vaccination coverage in 204 countries and territories, 1980-2019 : a systematic analysis for the Global Burden of Disease Study 2020, Release 1
Background Measuring routine childhood vaccination is crucial to inform global vaccine policies and programme implementation, and to track progress towards targets set by the Global Vaccine Action Plan (GVAP) and Immunization Agenda 2030. Robust estimates of routine vaccine coverage are needed to identify past successes and persistent vulnerabilities. Drawing from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2020, Release 1, we did a systematic analysis of global, regional, and national vaccine coverage trends using a statistical framework, by vaccine and over time. Methods For this analysis we collated 55 326 country-specific, cohort-specific, year-specific, vaccine-specific, and dosespecific observations of routine childhood vaccination coverage between 1980 and 2019. Using spatiotemporal Gaussian process regression, we produced location-specific and year-specific estimates of 11 routine childhood vaccine coverage indicators for 204 countries and territories from 1980 to 2019, adjusting for biases in countryreported data and reflecting reported stockouts and supply disruptions. We analysed global and regional trends in coverage and numbers of zero-dose children (defined as those who never received a diphtheria-tetanus-pertussis [DTP] vaccine dose), progress towards GVAP targets, and the relationship between vaccine coverage and sociodemographic development. Findings By 2019, global coverage of third-dose DTP (DTP3; 81.6% [95% uncertainty interval 80.4-82 .7]) more than doubled from levels estimated in 1980 (39.9% [37.5-42.1]), as did global coverage of the first-dose measles-containing vaccine (MCV1; from 38.5% [35.4-41.3] in 1980 to 83.6% [82.3-84.8] in 2019). Third- dose polio vaccine (Pol3) coverage also increased, from 42.6% (41.4-44.1) in 1980 to 79.8% (78.4-81.1) in 2019, and global coverage of newer vaccines increased rapidly between 2000 and 2019. The global number of zero-dose children fell by nearly 75% between 1980 and 2019, from 56.8 million (52.6-60. 9) to 14.5 million (13.4-15.9). However, over the past decade, global vaccine coverage broadly plateaued; 94 countries and territories recorded decreasing DTP3 coverage since 2010. Only 11 countries and territories were estimated to have reached the national GVAP target of at least 90% coverage for all assessed vaccines in 2019. Interpretation After achieving large gains in childhood vaccine coverage worldwide, in much of the world this progress was stalled or reversed from 2010 to 2019. These findings underscore the importance of revisiting routine immunisation strategies and programmatic approaches, recentring service delivery around equity and underserved populations. Strengthening vaccine data and monitoring systems is crucial to these pursuits, now and through to 2030, to ensure that all children have access to, and can benefit from, lifesaving vaccines. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd.Peer reviewe
Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries
Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely
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