Real-time method for the identification and quantification of hydrocarbon pyrolysis products: Part II. Application to transient pyrolysis and validation by numerical simulation

A real-time quantification infra red method has been developed with a gas cell to determine the composition of hydrocarbon pyrolysis products. The aim is to chemically characterise the fuel decomposition in case of regenerative cooling. The method can be extended to a large variety of applications. A transient analysis of the method behaviour is conducted to estimate its capacity to be applied to unsteady conditions (one measure per second), which can be encountered in cooling activity and unsteady processes. A numerical tool called RESPIRE (French acronym for Supersonic Combustion Ramjet Cooling with Endothermic Fuel, Transient Reactor Programming) is used to help in understanding the complex phenomena involved in such a chemical reactor. The validation of transient behaviour with respect to the computations shows negligible time delay (lower than few seconds with gasification rate higher than 60 wt.%) due to residence time in the experimental setup. The quantification accuracy is confirmed to be around 2 mol%. The agreement obtained on gas cell measurements is found to be correct over 10-20 wt.% of gasification rate and very satisfactory over 60 wt.% but this depends on the species. An extension of the method has been developed with a dedicated online cell to be specifically applied to supercritical and multiphase flows. The quantification of the gas phase in the pyrolysis mixture in case of biphasic flow is proposed and validated with an uncertainty around 3 wt.%. The coke formation is monitored as a function of time and its quantification is even tested with 50% of uncertainty after a numerical calibration with respect to simulation.