Rich Flammability Limits in CH3OH/CO/diluent Mixtures

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 O 2 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.