Experiments in methane at 10 bar pressure

In order to simulate the process parameters of thermal cracking in the refinery better experiments were carried out in a hydrocarbon atmosphere (methane) at 10 bar pressure. This corresponds to the maximum pressure of the gas supply. 

The experimental conditions were again heating rates P of 5, 10, 20, and 50 K/min, sample sizes from 1.0 to 4.0 mg, and gas flow rates of 5 cmVmin. 

Increase in the pressure leads to an increase of the peak maximum temperatures in the distillation (evaporation) range by up to 60 °C, whereas the peak maximum temperatures of the pyrolysis reaction can decrease by 10 °C. 

The peak maximum temperatures of the pyrolysis (cracking) reaction (450-485 °C) differ so little that for each heating rate a coefficient of variation V = 1.08 % of the corresponding mean has been calculated. Calculation of the kinetic coefficients using ASTM E 698-79 gives the following average values  

From the individual values of the kinetic coefficients in Table 4-38, an arithmetic mean with considerably larger coefficients of variation is derived by statistical evaluation  

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The start temperature of evaporation and of pyrolysis reaction may be defined by means of the onset temperature, which is itself defined as the temperature of the intersection of the tangents to the two branches of the curve, which have different slopes. The small drift of the curve of energy versus temperature introduces errors in the determination of the onset temperatures of evaporation events. For the experiment in methane at 10 bar pressure the onset temperatures and the peak maximum (minimum) temperatures of the evaporation are sometimes, quite close, due to the mode of determination (table 4-40) ... 

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