Using the CSTR to investigate the oxidation of hydrocarbons

The continuously-stirred tank reactor (CSTR) is one of the standard types of reactor used in industry. The reactants flow continuously at a known volumetric flow-rate into the reactor and, in order to maintain a constant reaction volume, there is a matching volumetric outflow from the reactor. As a result, chemical species spend only a finite time in the reactor. The CSTR is efficiently stirred so that there are neither any concentration gradients nor a temperature gradient. The bifurcation behaviour of such reactors have been widely investigated in the context of chemical engineering [Razon & Schmitz, 1987]. Particular attention has been paid to models using a first-order non-isothermal irreversible reaction (FONI models).

Traditionally, gas-phase combustion processes were studied in batch reactors. In the early to mid 1970s groups in Leeds and Naples realised that the CSTR offers a much better experimental arrangement [Caprio et al 1973; Gray & Felton 1974; Gray et al 1975; Caprio et al 1976; Felton et al 1976]. In a CSTR true stationary states can be realised and oscillatory behaviour sustained indefinitely. The use of CSTRs was responsible for the advancement in understanding of the mechanism for hydrocarbon oxidation in the 1970s and 1980s and they are now commonly used to study combustion reactions. The absence of spatial gradients permit a stress on the physical chemistry of the problem, without the added complications of fluid flow, and presents an opportunity to validate detailed kinetic mechanisms through the analysis of the rich variety of phenomena accompanying low temperature oxidation (multiplicity, birhythmicity, cool flames, oscillatory ignition, two-stage and multi-stage ignition, complex ignition, steady ignition etc). One of the principal experimental goals is to establish in the inflow pressure-ambient temperature plane, the regions in which the observed phenomena are found. This is effectively the construction of an unfolding diagram. This picture is usually built up from a series of experiments at constant pressure in which the ambient temperature is increased or decreased [Griffiths 1985]. Unfolding diagrams of specific systems are discussed in the review articles [Gray & Scott 1990; Griffiths 1985; Griffiths & Scott 1987].

There are a number of review articles containing good expository sections on the use of the CSTR in gas-phase combustion studies [Faravelli et al 1998; Gray & Scott 1990; Griffiths 1985; Griffiths & Scott 1987]


  1. V. Caprio, A. Insola, and R. Barbella. Preflame processes in the ozone activated oxidation of methlycyclopentane. In F.J. Weinberg, editor, Combustion Institute European Symposium 1973, pages 99--104. Academic Press, 1973.
  2. V. Caprio, A. Insola, and P.G. Lignola. Isobutane cool flames investigation in a continuous stirred tank reactor. In Sixteenth Symposium (International) On Combustion, pages 1155--1163. The Combustion Institute, 1976.
  3. T. Faravelli, P. Gaffuri, E. Ranzi, and J.F. Griffiths. Detailed thermokinetic modelling of alkane autoignition as a tool for the optimization of performance of internal combustion engines. Fuel, 77(3):147--155, 1998.
  4. P.G. Felton, B.F. Gray, and N. Shank. Low temperature oxidation in a stirred flow reactor -{II}. Acetaldehyde. Combustion and Flame, 27:363--376, 1976.
  5. B.F. Gray and P.G. Felton. Low-temperature oxidation in a stirred-flow reactor -I. Propane. Combustion and Flame, 23:295--304, 1974.
  6. B.F. Gray, P.G. Felton, and N. Shank. A theoretical and experimental study of the low temperature oxidation of acetaldehyde. In 2nd European Symposium on Combustion, page 103. The Combustion Institute, 1975.
  7. P. Gray and S.K. Scott. Experimental systems 2: Gas-phase reactions. In Chemical Oscillations and Instabilities: non-linear chemical kinetics, volume 21 of International Series of Monographs on Chemistry, chapter 15. Clarendon Press, first edition, 1990.
  8. J.F. Griffiths. Thermokinetic oscillations in homogeneous gas-phase oxidations. In R.J. Field and M. Burger, editors, Oscillations and Travelling Waves in Chemical Systems, pages 529--564. John Wiley & Sons, 1985.
  9. J.F. Griffiths and S.K. Scott. Thermokinetic interactions: Fundamentals of spontaneous ignition and cool flames. Progress in Energy and Combustion Science, 13:161--197, 1987.
  10. L.F. Razon and R.A. Schmitz. Multiplicities and instabilities in chemically reacting systems - A review. Chemical Engineering Science, 42(5):1005--1047, 1987.

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