Process Intensification and Green Processing Using Cavitational Reactors - Process Intensification for Green Chemistry - page 196

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Process Intensification and Green
Processing Using Cavitational Reactors

Vijayanand Moholkar, 1 Parag Gogate 2 and Aniruddha Pandit 2

1 Chemical Engineering Department, Indian Institute of Technology, Guwahati, Assam, India
2 Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai, India

7.1 Introduction

Cavitational reactors are a novel and promising form of multiphase reactor in which the
energy is released at the location of transformation, possibly resulting in significant process
intensification. The principle behind the expected beneficial effects is the phenomenon of
cavitation, described as the generation, subsequent growth and collapse of cavities, which
releases large magnitudes of energy over a very small volume, resulting in very high energy
densities [1,2]. Cavitation occurs at millions of locations in the reactor simultaneously, and
generates conditions of very high temperatures and pressures locally (a few thousand
atmospheres pressure and a few thousand K temperature), with overall ambient conditions
[3]. Moreover, free radicals are generated in the process due to the dissociation of vapours
trapped in the cavitating bubbles, which results either in intensification of the chemical
reactions or the propagation of certain reactions [4-6]. Cavitation also results in
the generation of local turbulence and liquid microcirculation (acoustic streaming) in
the reactor, enhancing the rates of the transport processes. These physical effects will
be responsible for the intensification of physical processing applications and chemical
processing applications limited by mass transfer.