Clean up of bleed air contamination

Abstract

To compensate for the low temperature and pressure at high altitude, the air provided to the cabin of the aircraft is drawn from the jet engine. This is known as bleed air which provides heat and pressurises the cabin and flight deck. As the air passes the engine, any minor mechanical faults can cause leakage of engine oil into the stream of air being fed into the cabin which can contaminate the air. There is growing evidence to suggest that this cabin air contamination in aircrafts is causing illness in passengers and this is accompanied by a concern that aviation safety regulators are not taking preventative actions.

The focus of this work was to develop a catalyst for bleed air contamination. For this, stainless steel 314 and 316 foams were modified and tested for the oxidation of known contaminants. The oxidised foam possessed had chemical composition of spinel oxides therefore, spinel oxides were also synthesised, reduced and etched during this work and were then tested. Stainless steel foam was an ideal candidate for this process as it can be used as a catalyst itself or act as a support to impregnate other catalytically active species on it. Spinel oxides also possess good catalytic capabilities. The main focus of the work was toluene as it is not only a contaminant in the cabin air but is also found in many industrial waste streams. It is also a model volatile organic compound therefore the catalytic system developed can be used in more than one application. Another contaminant studied was ethyl acetate which has been tested due to being present in the cabin air in the past. Raw SS 314/316 foams were modified via oxidation and dip coating to be investigated for the oxidation of toluene/ethyl acetate in to CO₂ (g) and H₂O (v) in a lab scale rig at temperatures between 200 and 500 °C. MnFeCrO₄ and MnNiCrO₄ spinels were synthesised using solution combustion method and reduced at different temperatures. The reduced spinels were tested for oxidation of toluene. The results show that the impregnated SS 316 foams have higher selectivity towards production of CO₂ (g) at lower temperatures compared to SS 314 foams and spinels.