Computational particle-fluid dynamics simulation of gas-solid flow in a circulating fluidized bed with air or O₂/CO₂ as fluidizing gas

Upadhyay, Mukesh,Park, Hoon Chae,Hwang, Jae Gyu,Choi, Hang Seok,Jang, Ha-Na,Seo, Yong-Chil Elsevier 2017 Powder technology Vol.318 No.-

<P><B>Abstract</B></P> <P>Computational particle-fluid dynamics (CPFD) simulation was carried out to examine the influence of air versus O<SUB>2</SUB>/CO<SUB>2</SUB> as the fluidizing gas on the hydrodynamics of gas-solid flow in a cold-mode circulating fluidized bed. The CPFD simulation results were compared to the experimental data at constant superficial gas velocity, using air or mixed O<SUB>2</SUB>/CO<SUB>2</SUB> in three different concentrations as the fluidizing gas. The simulation results showed that the model successfully captured the experimentally observed trends. A detailed statistical analysis was carried out on the transient pressure data, and results were found to vary depending on whether air or combustion gases (O<SUB>2</SUB>/CO<SUB>2</SUB>) were used for fluidization. In all cases, the flow exhibits a typical core-annular flow structure, although for O<SUB>2</SUB>/CO<SUB>2</SUB> gas the solid volume fraction increases near the wall region. The CPFD results provided insights into the gas-solid flow behavior in a fluidized bed combustor riser under an oxy-fuel fluidizing atmosphere.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Gas-solid flow hydrodynamics studied at air and oxy fluidizing conditions. </LI> <LI> CPFD model is used to study the fluid dynamic behavior. </LI> <LI> Comprehensive analysis of the transient pressure and solid volume fraction data. </LI> <LI> Key differences in flow features between air and oxy conditions were identified. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A NOVEL COMPUTATIONAL FLUID DYNAMICS SIMULATION OF LIGNOCELLULOSIC BIOMASS FAST PYROLYSIS IN A CIRCULATING FLUIDIZED BED REACTOR

Mukesh UPADHYAY,Hoon Chae PARK,Hang Seok CHOI 한국신재생에너지학회 2017 AFORE Vol.2017 No.11

Experiment and multiphase CFD simulation of gas-solid flow in a CFB reactor at various operating conditions: Assessing the performance of 2D and 3D simulations

Mukesh Upadhyay,서명원,Parlikkad Rajan Naren,박종호,Thanh Dang Binh Nguyen,Kashif Rashid,임한권 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.12

Accurate prediction of gas-solid flow hydrodynamics is key for the design, optimization, and scale-up of a circulating fluidized bed (CFB) reactor. Computational fluid dynamics (CFD) simulation with two-dimensional (2D) domain has been routinely used, considering the computational costs involved in three-dimensional (3D) simulations. This work evaluated the prediction capability of 2D and 3D gas-solid flow simulation in the lab-scale CFB riser section. The difference between 2D and 3D CFD simulation predictions was assessed and discussed in detail, considering several flow variables (superficial gas velocity, solid circulation rate, and secondary air injection). The transient Eulerian- Eulerian multiphase model was used. CFD simulation results were validated through an in-house experiment. The comparison between the experimental data and both computational domains shows that the 3D simulation can accurately predict the axial solid holdup profile. The CFD simulation comparison considering several flow conditions clearly indicated the limitation of the 2D simulation to accurately predict key hydrodynamic features, such as high solid holdup near the riser exit and riser bottom dense region. The accuracy of 2D and 3D simulations was further assessed using root-mean-square error calculation. Results indicated that the 3D simulation predicts flow behavior with higher accuracy than the 2D simulation.

Energy Requirements and Tillage Performance Under Different Active Tillage Treatments in Sandy Loam Soil

Choudhary Swapnil,Upadhyay Ganesh,Patel Bharat,Naresh,Jain Mukesh 한국농업기계학회 2021 바이오시스템공학 Vol.46 No.4

Purpose To assess the operational energy requirement (OER) and tillage performance index (TPI) of four different active tillage treatments and identification of the best efficient tillage practice among them to achieve an alternative to the conventional practice T1 (1×Cultivator+2×Offset disc harrow), which involves only purely passive type of tillage tools. Methods The active tillage treatments considered were as follows: T2 (1×Combined offset disc harrow), T3 (1×Cultivator+ 1×Single rotor type rotavator), T4 (1×Double rotor type rotavator), and T5 (1×Power harrow). Each implement in the respective treatment was operated at their best suitable forward speed and rotor rpm. Results Compared to the conventional practice T1, the amount of fuel saved per hectare in tillage practices, T2, T4, and T5, was 49.8%, 17.9%, and 20.3%, respectively. However, tillage treatment T3 was found to consume 6.9% more fuel. Compared to T1, the amount of time saved by T2, T3, T4, and T5 tillage practices was found to be 61.1%, 9.54%, 40.6%, and 44.6%, respectively. The maximum OER of 1445.32 MJ ha−1 was observed in T3 followed by 1360.40, 1105.86, 1085.86, and 681.36 MJ ha−1 in T1, T4, T5, and T2, respectively. Further, compared to T1, the TPI for tillage treatments, T2 and T4, was found to be higher by 74.07% and 133.33%, respectively. However, the TPI for tillage treatment T3 was found to be lower by 88.88%. Conclusions Active tillage implements helped in time and fuel-saving in seedbed preparation. The maximum percentage of operational energy was consumed in the form of fuel energy. The front active and rear passive configuration of combined offset disc harrow was found to be the most effective among all the tested active tillage implements in terms of both operational energy and tillage performance criteria.

GI Surgery

( Narayan Prasad Belbase ),( Aditya Kumar Jalan ),( Hari Upadhyay ),( Rohit Mishra ),( Mukesh Karki ),( Sujit Kumar ) 대한간학회 2020 춘·추계 학술대회 (KASL) Vol.2020 No.1

Aims: The aim of this study was to determine the outcome of liver injuries managed operatively or non-operatively and predict factors affecting morbidity and mortality. Methods: This was a retrospective study of 40 liver injuries managed in the department of Surgical Gastroenterology at College of Medical Sciences over a period of 2 years. The liver injury was classified in accordance with the American Association for the Surgery of Trauma liver injury scoring scale. Patients were divided into two groups those managed operatively or non-operatively and were compared in terms of demographic profile and outcome. Results: Forty patients were analyzed. The mean age of the patients was 29.95years. Male predominance was seen with 72.5% of the cases. Road traffic accidents were the commonest mode of injury seen in 72.5% cases. The mean Revised Trauma Score (RTS) and Injury severity score (ISS) were 7.11and 22.58. The mean systolic BP, hospital stay and ICU stay were 93.80 mm of mercury, 11.55 days and 3.55 days respectively. Twenty six patients (65%) were initially managed non-operatively and 14 patients were managed operatively. Five patients had to be converted to operative management for hemodynamic instability. Mortality was 7.6% in patient undergoing non-operative management and 21.43% in patients managed operatively. Low systolic BP at presentation, low RTS score, high ISS score, high AST, ALT and prothrombin time were significantly associated with operative management and mortality. Conclusions: Patients with hemodynamic instability, low RTS score, high ISS score, high liver enzymes have high likelihood of operative management.

Influence of process conditions on product yield of waste tyre pyrolysis- A review

최항석,Prakash Parthasarathy,Hoon Chae Park,황재규,Ho Seong Yoo,Byeong-Kyu Lee,Mukesh Upadhyay 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.8

Waste tyres have become a grave concern as their accumulation is aggregating every year. Not only the size of waste tyre has to be reduced, but also some useful energy has to be recovered out of it as the world badly requires energy from alternate sources. Pyrolysis is one such method to extract energy potential products from waste tyres. It is extensively used to generate carbon black (solid product), tyre-oil (liquid product) and syngas (gas product) from waste tyres. In that connection, this article discusses the effect of various parameters on the product composition of pyrolysis of waste tyres. The current usage of pyrolysis products and their typical characteristics are also discussed in this critique. Of late, extraction of high value added products, such as activated carbon from carbon black, and limonene from tyre-oil is gaining attention. The article also throws some light on the application and generation routes of activated carbon and limonene from waste tyres.