CFD Simulation of Chemical Looping Combustion System

Emerging technologies for greenhouse-gas mitigation have assumed growing importance due to the imminent threat of climate change. The American Clean Energy Security Act and the American Power Act project that about 30% of fossil-fuel-based electricity generation to come from power plants with carbon capture and sequestration (CCS) by 2040, rising to approximately 59% by 2050. Chemical looping combustion (CLC) is one of the most promising cost-effective technologies that can be retrofitted onto existing power plants for CCS. The main drawback attributed to CLC is a very low confidence level as a consequence of the lack of maturity of the technology. Use of computational fluid dynamics (CFD) has the potential to boost the development and implementation of commercial-scale CLC units. This dissertation focuses on designing a novel semi-batch CLC unit using fluidized-bed reactors and modeling the hydrodynamics of fluidized bed reactors with use of CFD. The National Energy Technology Laboratory’s (NETL, USA) open-source code MFIX is used in this study as flow solver for CFD models.In this dissertation, a conceptual design is developed that leads to fabrication of a 100-kWth semi-batch CLC prototype unit by ZERE Energy and Biofuels, Inc. San Jose, California. The hydrodynamics of the prototype unit are extensively studied using mathematical modeling and CFD. A multi-stage numerical model has been developed to investigate the behavior of a fuel reactor used in CLC unit. To predict the behavior of mass transfer in the CLC reactor, a combination of perturbation theory and semi-empirical correlation is suggested. Much of the work presented in this dissertation is focused on improving the ability to use CFD for process development. The grid size used in numerical simulations should be sufficiently small so that the meso-scale structures prevailing in the gas-fluidized beds can be captured explicitly. This restricts CFD in studying industrial-scale fluidized bed reactors. Thus, a generalized grid size that is sufficient to obtain a grid-independent solution of two-fluid CFD model is suggested in this study. In order to fully understand the complex interaction between fluid phases of CFD models, a 3-D face-masking algorithm is developed and applied to assist post-processing CFD results for identification and tracking of gas bubbles in a fluidized bed. Finally, the hydrodynamics of multiphase flow reactor at high-temperature is investigated through the particle-particle restitution coefficient in numerical simulations. In conclusion, findings of this dissertation will be useful for scale-up, design, or process optimization for reliable commercial CLC plants reducing economic risk, and potentially allowing for rapid scale-up

Effects of sodium sulfate and sodium chloride for sonochemical degradation on1,4-benzoquinone and hydroquinone in aqueous solution

1,4-benzoquinone, with the molecular formula C6H4O2, is generally known as a para-quinone. It is a six-member ring compound with an oxidized derivative known as 1,4-hydroquinone, which is a bright yellow crystal that has an irritating odour. On the other hand, hydroquinone, also known as benzene-1,4-diol, has the chemical formula C6H4(OH)2. It looks like a white granular solid. Quinone is generally used as a precursor to hydroquinone. The skeletal muscle relaxant, ganglion blocking agent, benzoquinonium, is made from benzoquinone. It is utilized to suppress double-bond migrations during olefin metathesis reactions. 1,4-benzoquinone is also used in the synthesis of Bromodol, while hydroquinone is the main ingredient in black-and-white photographic developers such as film and paper developers, where it diminishes the silver halide to elemental silver. There are various other uses related to this diminishing power. As a polymerization inhibitor, hydroquinone prevents the polymerization of methyl methacrylate, acrylic acid, etc. Studies have demonstrated the various effects of Na2SO4 and NaCl on the sonochemical degradation of 1,4-benzoquinone and hydroquinone using a 200-kHz sonicator. The highest degradation rate was obtained in the presence of 0.433 M Na2SO4 for 1,4-benzoquinone. After 30 minutes of ultrasonic irradiation, the total concentration of 1,4-benzoquinone decreased to 99% in the presence 0.433 M Na2SO4. Without Na2SO4, the sonochemical degradation rate of 1,4-benzoquinone was 4.5 times higher than that of hydroquinone, whereas in the presence of 0.433 M Na2SO4 under the same conditions the initial reaction rate of 1,4-benzoquinone was increased to become 10.6 times higher than that of hydroquinone. On the other hand, in the presence of NaCl, no effects were observed for the decomposition of hydroquinone but negative effects were clearly observed for the decomposition of 1,4-benzoquinone

An Overview on the Basics of Islamic Audit

Today is the age of globalization and business is considering as the leading global factor for social and   economic development. It is said that, Accounting is the language of business but it is another gigantic thought that Auditing is the side language of business. Audit is the vital factor to ensure the accountability of an organization, this paper events to explore audit on the perspective of Islam which further enables a practitioners and intended users to be self-confident and inspirational in using his or her acquired knowledge both in traditional system of auditing as well as Islamic perspective. The plot of the paper is as follows: In the first part we shall examine the development and approach of established auditing and point out some of its inadequacies from the Islamic point of view. In the last part, we shall state the role of auditing in the Islamic framework. Keywords: Islamic Auditing, Conventional Auditing, Islamic Shari’ah

The plight of the Bangladeshi silk industry: An empirical investigation

In spite of having a glorious history in the sericulture industry Bangladesh still is not a bright name in silk production and export. Although the agro-climatic situation in Bangladesh greatly favors the development of silk industry, Bangladesh produces very little amount of silk products every year, whereas India, situated beside Bangladesh, is the second largest producer of sericulture. To investigate the reason behind this, a questionnaire survey has been undertaken in which only the owners or managers have been considered as representatives of the industry. A total of 21 silk enterprises was randomly sampled. Data analyses show that almost 57% of the silk enterprises have less than 40 decimal of land while only 19% have more than 100 decimal of land. These enterprises provided very limited facilities for their workers and mostly depended on imported raw materials. Owners pointed out several constraints to the development of silk industry in Bangladesh including insufficient government patronization and recommended several remedial measures including that the Bangladesh Silk Board (BSB) gives out production credit without too much conditions, adoption of modern technology, and information dissemination . It is evident that government, through BSB and BSRTI (Bangladesh Silk Research and Training Institute) has to play a crucial role to pull this industry up from the brink of destruction

Behavioral and psychosocial predictors of depression in Bangladeshi medical students: a cross-sectional study [version 1; peer review: 2 approved]

Background: Depression, stress, and anxiety were found in a large number of medical undergraduate students, indicating a neglected aspect of their psychology that required immediate attention. The goal of this study was to find out the prevalence of depression among medical students, as well as potential psychosocial and behavioral predictors for depression.  Methods:   This cross-sectional study was conducted from July to November 2021 among 840 randomly selected medical students from four medical colleges using stratified random sampling. Data were collected using a semi-structured, self-administered questionnaire and were analyzed through the SPSS v.23 software. Multiple regression was performed to assess the effect of several behavioral and psychosocial factors on depression.   Results: Among the 840 study participants, 55.7% (n= 468) were female and 44.3% (n= 372) were male. According to the data, the prevalence of depression, anxiety, perceived stress among medical students was found to be 28.8%, 65% and 85% respectively. A strong link was found between depression and anxiety, stress, poor sleep quality, poor academic performance, and a negative social and romantic relationship status.   Conclusions: A significant number of medical students are depressed. In order to prevent and treat depression, medical students should be screened for depression and its associated factors

Examining Bangladesh’s responses to COVID-19 in light of Vietnam: Lessons learned

This review aimed to examine the extent of Bangladesh’s COVID-19 preparedness and control measures up to 20 January 2021, and to draw some lessons for informing the current and future pandemic responses in Bangladesh in light of Vietnam’s responses, which had successfully controlled the pandemic. We performed a content analysis of data to identify similarities and critical discrepancies in epidemiological features and COVID-19 responses between the two countries. Findings indicated that Vietnam reported lower COVID-19 incidence (15 cases per million) and death rate (0.4 cases per million) than Bangladesh, with 3,129 cases per million and a death rate of 46 cases per million. Vietnam reported only 35 deaths, with 22 older individuals (>60 years) compared with 7,950 deaths in Bangladesh, with the highest death rate in older people (45%). An integrated approach combined with widespread contact tracing, better health investment, vaccine development, and strong political commitment enabled Vietnam to control the disease and mitigate its impacts. In contrast, Bangladesh seemed to adopt inadequate and untimely measures in the same domains, potentially contributing to relatively high COVID-19 infections and death rates. To control COVID-19 or inform responses to future pandemics, Bangladesh and similar countries can learn eight lessons from Vietnam. Such transferable responses could prepare health systems and populations for an appropriate global response to the next potential pandemic

Interactive IIoT-Based 5DOF Robotic Arm for Upper Limb Telerehabilitation

Significant advancements in contemporary telemedicine applications enforce the demand for effective and intuitive telerehabilitation tools. Telerehabilitation can minimize the distance, travel burden, and costs between rehabilitative patients and therapists. This research introduces an interactive novel telerehabilitation system that integrates the Industrial Internet of Things (IIoT) platform with a robotic manipulator named xARm-5, aiming to deliver rehabilitation therapies to individuals with upper limb dysfunctions. With the proposed system, a therapist can provide upper limb rehab exercises remotely using an augmented reality (AR) user interface (UI) developed using Vuforia Studio, which transmits bidirectional data through the IIoT platform. The proposed system has a stable communication architecture and low teleoperation latency. Experimental results revealed that with the developed telerehabilitation framework, the xArm-5 could be teleoperated from the developed AR platform and/or use a joystick to provide standard upper limb rehab exercises. Besides, with the designed AR-based UI, a therapist can monitor rehab/robot trajectories along with the AR digital twin of the robot, ensuring that the robot is providing passive therapy for shoulder and elbow movements

Examining Bangladesh’s responses to COVID-19 in light of Vietnam : lessons learned

This review aimed to examine the extent of Bangladesh’s COVID-19 preparedness and control measures up to 20 January 2021, and to draw some lessons for informing the current and future pandemic responses in Bangladesh in light of Vietnam’s responses, which had successfully controlled the pandemic. We performed a content analysis of data to identify similarities and critical discrepancies in epidemiological features and COVID-19 responses between the two countries. Findings indicated that Vietnam reported lower COVID-19 incidence (15 cases per million) and death rate (0.4 cases per million) than Bangladesh, with 3,129 cases per million and a death rate of 46 cases per million. Vietnam reported only 35 deaths, with 22 older individuals (>60 years) compared with 7,950 deaths in Bangladesh, with the highest death rate in older people (45%). An integrated approach combined with widespread contact tracing, better health investment, vaccine development, and strong political commitment enabled Vietnam to control the disease and mitigate its impacts. In contrast, Bangladesh seemed to adopt inadequate and untimely measures in the same domains, potentially contributing to relatively high COVID-19 infections and death rates. To control COVID-19 or inform responses to future pandemics, Bangladesh and similar countries can learn eight lessons from Vietnam. Such transferable responses could prepare health systems and populations for an appropriate global response to the next potential pandemic