Estimation of lower flammability limits in high-pressure systems. Application to the direct synthesis of hydrogen peroxide using supercritical and near-critical CO2 and air as diluents

C.M. PIQUERAS; J. GARCÍA-SERNA; M.J. COCERO

JOURNAL OF SUPERCRITICAL FLUIDS

ELSEVIER SCIENCE BV

Año: 2011 vol. 56 p. 33 - 40

0896-8446

A method for the prediction of the LFL at high pressures, where data are scarce, based on the calculation of adiabatic flame temperatures for the mixtures H2+O2 in CO2 and N2, between 1.0 and 300 bar and 288 to 348K is presented. A group contribution equation of state (GC EoS) has been selected to predict thermodynamic properties of the mixture, i.e. residual enthalpy, heat capacity and others, as well as phase equilibrium data, giving deviations lower than 10% at high pressures. The use of CO2 as a diluent increases the operational margin from 4.5 mol% H2 at 1 bar up to ca. 7.0 to 9.0 mol% H2 at 200 bar due to the increase in the heat capacity. On the other hand, the use of nitrogen or air as a diluent only increases the margin from 5.2 mol% H2 at 1 bar up to ca. 6.0 mol% H2 at 200 bar.