COMBUSTION OF ETHANE WITH SMALL CONCENTRATIONS OF METHYL-CHLORIDE IN A REFRACTORY TUBE BURNER

Premixed, thermally stabilized combustion inside a refractory-tube wit hout a flameholder has a number of unique characteristics that are fav orable for incineration. Owing to the fully developed turbulent flow, the velocity, temperature and composition are relatively uniform acros s the channel. Because of the absence of backmixing other than the neg ligible degree associated with confined turbulent flow, the flame fron t is a virtual step in temperature and composition. Owing to the therm al feedback by wall-to-wall radiation and in-wall conduction, the temp erature of the stream of gas immediately behind the flame front exceed s the adiabatic value, and owing to the great thermal inertia of the r efractory tube and the plug-like flow, the combustion is very stable a nd free of oscillations. Most important of all, the temperature of the wall is close to that of the gas throughout the burner. The net effec t of these characteristics is that every molecule of the gaseous mixtu re experiences essentially the same period of extreme and nearly unifo rm temperature. In the current investigation small concentrations of m ethyl chloride (0.02 to 0.11 mole per mole of ethane) in a slightly le an mixture of ethane and air were passed through a round, 19.5-mm chan nel in a ceramic block. The concentration of chlorohydrocarbons in the exit gas was below our level of detection (similar to 1 ppm), and sup porting theoretical calculations with a detailed kinetic model predict ed concentrations of only a few parts per trillion (a reduction by a f actor of about 10(8)). The addition of the methyl chloride did not aff ect the combustion significantly.