Journal of Applied Mechanical Engineering

The scaling problem of oxide materials hydrothermal synthesis for various autoclave reactors with considering natural convection

3^rd International Conference on Fluid Dynamics & Aerodynamics

October 25-26, 2018 | Berlin, Germany

I V Sharikov

Saint Petersburg Mining University, Russia

Keynote: J Appl Mech Eng

Abstract:

Hydrothermal synthesis is widely used for the production of various nanodispersed oxide materials. Reactions under hydrothermal conditions are complicated and usually they are accompanied with heat generation or heat absorption. Heat flux calorimetry is a powerful instrument for kinetic study and developing mathematical models of hydrothermal reactions. A mathematical model makes it possible to determine optimal experimental conditions for the production of a definite material on the base of a limited number of kinetic calorimetric runs. But in order to apply the kinetic data to reactors of larger volume one should take into account heat transfer, mass transfer phenomena and non-uniform temperature distribution in a definite apparatus at the chosen initial conditions and in course of hydrothermal synthesis. Reaction vessel of C80 Calvet calorimeter (SETARAM Instrumentation) is a micro-autoclave of 8.5 cm3 volume without mechanical stirring. Heat transfer and mass transfer inside it are run due to natural convection while heating to a chosen temperature of an isothermal run. And temperature gradient in this case is rather moderate (yet not negligible) as the reactor is relatively small. If we pass to the reactor of a larger volume (e.g., 1 liter) ??? we find that the real temperature mode in it is far from that in a kinetic vessel at the same initial conditions. In order to take into account the temperature and conversion distribution due to natural convection in course of a definite hydrothermal synthesis we have developed a mathematical model that takes into account convection inside a hydrothermal reactor together with the chemical reaction. Convective flows were described at the base of Business approach and the differential equations system was solved with applying Convex program package that takes into account size and geometry of the reactor, reaction mixture properties, heat transfer peculiarities inside and outside and heat generation due to chemical reaction. It was found that temperature and conversion distributions in the calorimetric vessel and in the 1 liter reactor were rather different at similar initial conditions from the very beginning. Time of reaching the stationary temperature profile in the bigger vessel at implementing, e.g., isothermal mode is comparable with total duration of the run, and stationary temperature gradient is bigger as well. This indicates of the necessity to estimate rigorously the natural convection and heat transfer phenomena at scaling the hydrothermal synthesis for the reactor of bigger volume without mixing. Kinetic models developed on the base of calorimetric data cannot be directly applied to simulating the hydrothermal synthesis process in such a reactor. Recent Publications 1. Byrappa K and Yoshimura M (2001) Handbook of hydrothermal technology. A technology for crystal growth and materials processing. New York: William Andrew Publishing, ISBN 081551445X. 2. Ivanov V K, Kopitsa G P, Sharikov F Yu, et al. (2010) Ultrasound-induced changes in mesostructure of amorphous iron (III) hydroxide xerogels: A small-angle neutron scattering study. Physical Review B 81:174201. 3. Gershunin G Z and Zhukhjvitskii E M (1989) Stability of convection flows. PMM 31(2):272-281.

Biography :

I V Sharikov graduated from the Technological University, St.-Petersburg, in 1958. Diploma qualification is “chemical engineer-technologist”. In 1961 he entered a postgraduate course in the same Technological University, department of Physical Chemistry. In 1965 he presented a dissertation work and got Ph.D (physical chemistry), chemical kinetics and mass transfer phenomena. From 1965 to 1979 he was Head of Laboratory of mathematical modelling and optimisation of chemical and technological processes (Research Institute of Synthetic Resins, Vladimir, VNIISS). In 1973 he presented and defended a dissertation work for Doct. Sci. – “Mathematical modelling of cellulose esters production process”. In 1976 he got a Professor diploma for the speciality “Processes and Apparatuses in Chemical Technology”. In 1979 he became Head of the Department for engineering judgement of chemical processes (Russian Scientific Centre “Applied Chemistry”, RSC AC, or GIPH). 1985-1999 - Deputy General Director for scientific work in RSC AC. 1999-2007 - Principal Research Scientist, leader of several works on developing new chemical processes and their engineering aspects. Totally 182 articles were published in Russian and foreign scientific journals. I.V. Sharikov is a member of the working group on Loss Prevention in industry in the European Society of Chemical Engineers. From 2004 and up to the moment I.V. Sharikov is professor of Saint Petersburg Mining University, Department of Technological Processes Automation. His area of interest is mainly the problem of optimal control and modeling for high temperature metallurgical and petrochemical processes. He is fluent in English and German.

E-mail: felix101t@mail.ru

yvshar@mail.ru