Combinative treatment of phenol-rich retting-pond wastewater by a hybrid upflow anaerobic sludge blanket reactor and solar photofenton process

Sokkanathan, G.,Sharmila, V. Godvin,Kaliappan, S.,Banu, J. Rajesh,Yeom, Ick Tae,Rani, R. Uma Elsevier 2018 Journal of environmental management Vol.206 No.-

<P><B>Abstract</B></P> <P>In this study, recalcitrant rich retting-pond wastewater was treated primarily by anaerobic treatment and subsequently treated with a solar photofenton process to remove phenol and organics. The anaerobic treatment was carried out in a granulated laboratory scale hybrid upflow anaerobic sludge blanket reactor (HUASBR) with a working volume of 5.9 L. It was operated at different hydraulic retention times (HRT) from 40 to 20 h over a period of 140 days. The optimum HRT of the anaerobic reactor was found to be 30 h, with corresponding chemical oxygen demand (COD) and phenol removal of 60% and 47%, respectively. Primary anaerobically treated wastewater was subjected to secondary solar photofenton treatment which was carried out at pH 3.5. Response surface methodology (RSM) was used to design and optimize the performance of the solar photofenton process. Regression quadratic model describing COD removal efficiency of the solar photofenton process was developed and confirmed by analysis of variance (ANOVA). Optimum parameters of the solar photofenton process were found to be: 4 g/L of fenton as catalysts, 25 mL of hydrogen peroxide, and 30 min of reaction time. After the primary anaerobic treatment, solar photofenton oxidation process removed 94% and 96.58% of COD and phenol, respectively. Integration of anaerobic and solar photofenton treatment resulted in 97.5% and 98.4% removal of COD and phenol, respectively, from retting-pond wastewater.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The HUASB reduces COD and phenol to 180 mg/L and 117 mg/L respectively at 30 h HRT. </LI> <LI> The maximum biogas production of 0.82 L/d at 30 h HRT. </LI> <LI> The post treatment was carried out by solar photofenton process for 30 min. </LI> <LI> Combined HUASB and photofenton process removed 97.5% and 98.4% COD and phenol. </LI> </UL> </P>

A Theoretical Study for the Design of a New Ballistic Range

G. Rajesh,Y. K. Lee(이영기),S. C. Back(백승철),H. D Kim(김희동) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

The Ballistic Range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile Aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of Ballistic Ranges developed to date, two-stage light gas gun is being employed most extensively. In the current study, a theoretical work has been made to develop a new type of Ballistic Range which can easily simulate a flying projectile. The present Ballistic Range consists of piston, pump tube, highpressure tube, shock tube and launch tube. One-dimensional, unsteady compressible equations are solved to obtain the major design parameters of the present Ballistic Range.

A Computational study of the Gas Flow in a Coanda Ejector

G. Rajesh,J. H. Lee,Y. K. Lee,H. D. Kim(김희동) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11

The Coanda effect has been used extensively in various aerodynamic applications to improve the system performance. The primary flow in Coanda ejectors is attached to the ejector wall and is expanded inducing a secondary flow. This will probably lead to the mixing of both primary and secondary flows at a down stream section. Very few works have been reported based on the optimization on such devices. The main objective of the present study is to numerically investigate the flow field on a typical Coanda ejector and validate the results with the available experimental data. Many configurations of the Coanda ejector have been analyzed. The effect of various geometric parameters of the device on the expanding mixing layer has also been obtained. The computed data agree fairly well with the experimental data available.

Computational Study of the Unsteady Projectile Aerodynamics

G. Rajesh,H. G. Kang(강형구),J. M. Lee(이정민),H. D. Kim(김희동) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

A computational fluid dynamics method has been used to simulate the unsteady flow field on a projectile launched from a ballistic range. A moving coordinate scheme for a multi-domain technique was used to study the unsteady flow with moving boundary. The unsteady, axisymmetric Euler equation systems were numerically solved using the third order Chakravarthy-Osher total variation diminishing scheme, with MUSCL approach. Effects of initial pressure and temperature behind the projectile on the flow field were studied. The present results were validated with the available experimental data. The computed results predict the dramatic changes in the flow field when the initial pressure and temperature behind the projectile are varied. For higher pressures and temperatures, the projectile and the blast wave propagation is faster and the supersonic jet in front of the projectile is more under expanded compared to the other cases.

Ballistic Range의 작동과정에 대한 수치 해석적 연구

G. Rajesh,강현구(H. G. Kang),김희동(H. D. Kim) 한국추진공학회 2007 한국추진공학회 학술대회논문집 Vol.2007 No.11

Solution-based synthesis of high yield CZTS (Cu₂ZnSnS₄) spherical quantum dots

Rajesh, G.,Muthukumarasamy, N.,Subramanian, E.P.,Venkatraman, M.R.,Agilan, S.,Ragavendran, V.,Thambidurai, M.,Velumani, S.,Yi, J.,Velauthapillai, D. Academic Press 2015 Superlattices and microstructures Vol.77 No.-

High yield CZTS quantum dots have been synthesized using simple precursors by chemical precipitation technique. Formation mechanism of CZTS spherical quantum dots also has been investigated. According to the mechanism, copper sulfide nuclei firstly forms, and serves as the starting point for the nucleation and growth of CZTS. X-ray diffraction pattern, X-ray photoelectron spectra (XPS) and Raman spectra reveals the formation of pure kesterite structure Cu<SUB>2</SUB>ZnSnS<SUB>4</SUB> nanoparticles. HRTEM analysis reveals the formation of CZTS quantum dots with an average particle size of ~8.3nm. The elemental distribution of CZTS quantum dots studied using STEM elemental mapping reveals that Cu, Zn, Sn and S are present in the sample. The photoluminescence spectra of CZTS exhibit a broad red emission band at 657nm. The optical band gap is shifted to the higher energy side and it shows the presence of quantum confinement effect.

A Theoretical Study for the Design of a New Ballistic Range

G. Rajesh,J. M. Lee,S. C. Back,Heuy Dong Kim 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.7

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 ㎞/sec could be achieved with the present ballistic range.

코안다 이젝터 유동에 관한 수치해석적 연구

G. Rajesh,이준희(J. H. Lee),김희동(H. D. Kim) 한국추진공학회 2005 한국추진공학회 학술대회논문집 Vol.2005 No.11

A Theoretical Study for the Design of a New Ballistic Range

Rajesh G.,Lee J.M.,Back S.C.,Kim Heuy-Dong The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.7

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.

Computational and Experimental Simulations of the Flow Characteristics of an Aerospike Nozzle

Rajesh, G.,Kumar, Gyanesh,Kim, H.D.,George, Mathew The Korean Society of Visualization 2012 한국가시화정보학회지 Vol.10 No.1

Single Stage To Orbit (SSTO) missions which require its engines to be operated at varying back pressure conditions, use engines operate at high combustion chamber pressures (more than 100bar) with moderate area ratios (AR 70~80). This ensures that the exhaust jet flows full during most part of the operational regimes by optimal expansion at each altitude. Aero-spike nozzle is a kind of altitude adaptation nozzle where requirement of high combustion chamber pressures can be avoided as the flow is adapted to the outside conditions by the virtue of the nozzle configuration. However, the thrust prediction using the conventional thrust equations remains to be a challenge as the nozzle plume shapes vary with the back pressure conditions. In the present work, the performance evaluation of a new aero-spike nozzle is being carried out. Computational studies are carried out to predict the thrust generated by the aero-spike nozzle in varying back pressure conditions which requires the unsteady pressure boundary conditions in the computational domain. Schlieren pictures are taken to validate the computational results. It is found that the flow in the aero-spike nozzle is mainly affected by the base wall pressure variation. The aerospike nozzle exhibits maximum performance in the properly expanded flow regime due to the open wake formation.