MODELLING AND SIMULATION OF CATALYTIC CONVERTER IN AUTOMOBILE EXHAUST TAIL PIPE

Abstract

The road traffic is on of the major sources of the air pollutants of which carbon monoxide, hydrocarbon, nitrogen oxides and sulphur dioxide are the main emissions. Oxides of nitrogen ("NO„" including NO and NO2) contribute to smog and are the main cause of acid rain. Carbon monoxide (CO) is poisonous to people, as it renders the lungs less effective in taking in oxygen, but it is overall not harmful to the environment. Hydrocarbons (HC) are contributors to smog and are generally unhealthy. Few of them are even carcinogenic. Now a days, many contribute requires very stringent emissions limit for engine to prevent the pollution problems. Various techniques were needed to meet the prescribed standards of emissions, which includes:- 1. Modification of the engine to decrease the emission of raw emissions. 2. After- treatment of the engine exhaust by heterogeneous catalysts to convert the engine raw emission. 3. A combination of engine exhaust after treatment by heterogeneous catalyst. Present study is concerned with the vehicular pollution control using catalytic converter in automobile tail pipe. The catalytic converter is mounted somewhere on the exhaust pipe of the automobile. It filters these gases with the dense honey comb structure coated with precious metals like platinum, palladium and rhodium. Chemical reaction occurs on their surface and converts the pollutants (CO, HC, and NOR) into less harmful gases. A steady state and a transient state one dimensional model are developed to simulate the thermal conversion characteristics of adiabatic monolith converter operating under warm up conditions. A steady state and a transient state one dimensional model accounts for simultaneous process of heat transfer, mass transfer, and chemical reaction. The complex physical phenomena accounted in the model includes the heat and mass transfer between the exhaust gas and the catalytic surface, convective heat and mass transport, chemical reactions and related heat release, heat conduction in the substrate, and heat loss to the environment. The model has been used to analyze the steady state and transient response of an ax symmetric catalytic converter during a warm up as a function of catalyst design parameters and the operating conditions in order to observe their effects on the light off. The results obtained from the simulated model shows increase in the temperature of the solid phase i.e. catalyst wall above its initial temperature as the conversion takes place. High feed stream temperature also yields in increased solid phase temperature. Further decrease in the concentration of the species obtained from the model is qualitatively acceptable as compared with those in the available literature. The results obtained have been represented graphically.