AN EXPERIMENT TO PURIFY DIESEL EXHAUST-GAS USING AN ELECTRIC TRAP AND3 TYPES OF CATALYSERS

Diesel engine exhaust gas is known to be one cause of photochemical sm og, which is so damaging to city environments. However, because of its high thermal efficiency and economic advantages, the diesel engine is not easily dispensable. The authors have previously conducted a serie s of experiments to assess the purifying effects of a diesel gas purif ication device employing an electric trap. It has been confirmed that an extraction rate of 60 similar to 75 % for black. smoke can be achie ved using this apparatus, but the extraction effect for nitrogen oxide s (NOx) is insufficient if the electro-trap device is used on its own. To improve its performance, experiments have now been undertaken usin g the same device in combination with various types of attached cataly sers to oxidise and remove the nitrogen in the exhaust gas. Utilising a commercial 3-way catalyser, it proved difficult to maintain the gas at a suitable temperature, so that no outstanding result could be obta ined. Nor was any significant result observed from the use of an ozoni ser. However, with a zeolyte catalyser, it was possible to achieve a N Ox reduction of 20 similar to 30 %. This latter experiment is reported in the present paper.