Measured oxygen concentration response curve

As shown below, the influence of three quite distinct dynamic processes play a role in the overall measured oxygen concentration response curve. These are the processes of the dilution of nitrogen gas with air, the gas-liquid transfer, and the electrode response characteristic, respectively. Whether all of these processes need to be taken into account when calculating KLa can be seen by examining the mathematical model and making simulations. 

Measured oxygen concentration response curve 534 Measurement... 

The predictions of the theoretical model have been compared with the experimental results. Oxygen concentration breakthrough curves were measured experimentally by sending to an oxygen analyzer a small fraction of the product gas produced at the exit of the bed. The oxygen analyzer response was about 1 sec, and readings were taken every second. There is a period when the unit is not producing, namely between the end of the production step in one bed, and the end of the pressurization step in the other bed. The experimental results are... 

The measurement system developed, as shown in Figure 5, is introduced into the furnace on level SCCo i so that the ceramic tip is in the gas flow. The key elements of the measurement equipment are a suction pyrometer for the temperature measurement, a wide-range oxygen sensor (BOSCH LSU4) for the fast oxygen measurement, and a thermal conductivity detector (TCD) to measure the transient response of the Helium tracer concentration. For the determination of the transient response of the TCD measurement system itself Helium tracer was injected Just at the inlet of the suction pyrometer. In Figure 7 a typical transient response of the TCD measurement system is shown (curve with index SCCi . 

We now use the mass balance discrepancy to subtract the contribution of any "accumulation-reaction" processes present from the measured responses. For example, the corrected response curve for CO, shown in Fig. 12, was obtained at each instant in time by adding to the measured outlet CO concentration the amount of CO that was converted to CO2 by reaction with oxygen atoms stored in the catalyst, as determined from the oxygen balance. The fact that the corrected CO response and the corrected CO2 response, shown in Fig. 13, do not match the instantaneous response demonstrates the action of an "activity change" type of transient chemical process. The process resulted in lower-than-expected CO conversion, since the activity change process included in the simulation was partial deactivation of the catalyst in lean exhaust (e.g., by oxidation of the precious metal). 

---