Rich Flammability Limits in CH₃OH/CO/diluent Mixtures

ABSTRACT

This investigation is an attempt to predict theoretically, using existing flame modeling capabilities, rich flammability limits for gas mixtures—parameters that are of immense interest to the chemical industry. The system chosen for study is methanol/carbon monoxide/diluent mixtures, where the diluent is either nitrogen or carbon dioxide at pressures of 1,11, and 21 atm, respectively. The critical oxygen concentration needed to sustain a flame, for several mixtures and pressures, was determined experimentally in a spherical vessel with a central ignition source. Burning velocities of 1-D, planar, freely propagating, premixed flames were calculated to determine the minimum oxygen concentration required for these flames to propagate. This minimum O₂ concentration was found to be consistently larger than that observed in experiments; however, the effects of pressure and diluent composition agreed well with experimental measurements. In order to understand better all the phenomena involved, a transient ignition model was applied to the spherical vessel experiment, which resulted in better agreement with the data. The various comparisons are discussed in detail.