Zirconia pumped

REGULATION OF OXYGEN PARTIAL PRESSURE IN MELTS BY ZIRCONIA PUMPS... 

Ogando, J. (2005) Zirconia pump liners last longer, lower total coast. Design News, 7 March 2005. 

Zirconia cells similar to the ones employed in the present study, have been used i) by Mason et al (18) to electrochemically remove oxygen from Pt and Au catalysts used for NO decomposition. It was shown that electrochemical oxygen pumping causes a dramatic increase in the rate of NO decomposition (18,19), ii) by Farr and Vayenas to electrochemically oxidize ammonia and cogenerate NO and electrical energy (20,21), iii) by Vayenas et al (11,12,22,23) to study the mechanism of several metal catalyzed oxidations under open circuit (potentiometric) conditions. 

Several oxygen sensors based on oxygen pumping with stabilised zirconia have been reported (Hetrick, Fate and Vassell, 1981). This type of oxygen sensor is able to measure the oxygen partial pressure in the exhaust gas from the engine in lean burn. The operating principle of the... 

Yttrium stabilized zirconia (Zr02-Y203) as an electrolyte for reduction of molecular oxygen at elevated temperatures (400-800°C) has been already discussed in Section 6.23.4. In fact, both the reduction of oxygen and the oxidation of the oxide ion at the Pt/zirconia interface is reversible and the transport of both species in zirconia is so rapid it is possible to construct an electrochemical oxygen pump, which is the heart of the limiting current oxygen sensor described in this chapter (Saji, 1987). The overall electrochemical reaction that takes place at the porous Pt electrode is... 

Test Results. The pH response of the zirconia tubes was tested at elevated temperatures and pressures using the apparatus previously described. Standard HC1 and NaOH solutions were pumped through the test chamber while the EMF of the sensor was monitored. The pH values at temperature and pressure were calculated from the room temperature pH measurement based on hydrogen ion mass balance using the data of (11). 

Electrochemical pumps have also been successfully used to promote reactions catalytically. If oxygen is pumped through a zirconia cell into a reaction chamber which is, e.g., filled with hydrocarbons, not only the oxygen that is transferred, reacts. The anode itself can act catalytically. It seems that this so-called NEMCA effect ( Nonfaradaic Electrochemical Modification of Catalytic Activity 51) relies on a hindered surface reaction as a consequence of which the applied potential is translated into a concentration polarization, as reflected by the enrichment of a not fully oxidized oxygen species (e.g., O or O2") at the interface.51"53 For this species, redistribution equilibrium may be assumed that... 

Oxide ion conductors have been extensively investigated for their applications in fuel cells, oxygen sensors, oxygen pumps, and oxygen permeable membranes [81-108], The ion conduction effect was discovered more than a century ago by Nernst in zirconia products [83,84], To use zirconia, it... 

The zirconia-based pump-sensor device can be used for controlling the oxygen partial pressure in closed systems typical applications include the oxygen permeation flux measurements, oxygen monitoring in molten metals, and coulometric titration. 

The cylindrical oxygen pumps based on zirconia electrolytes, in contrast from the lamellar oxygen pumps, can be utilized in such compact designs as test tubes, crucibles, and the like. Therefore, their practical implementation is more accepted by industry. The principal scheme of the cylindrical oxygen pump is shown in Figure... 

Therefore, considering the equations given above, it is possible to calculate the reversible zirconia oxygen pumps and to determine their main characteristics during oxygen pumping from the liquid metal into the gaseous environment... 

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