Technical Definition and Description Catalytic Converter - Essay Example

?Catalytic Converter Catalytic converters are essential in eliminating pollution caused by incomplete combustion of diesel in cars. There are many cars on the roads and the need to protect the environment saw the need to produce a device that would ensure that air pollution caused from vehicle exhausts is minimized. In the early 20th century, manufactures of vehicles started the manufacture of the catalytic converters, which would treat the exhaust gases. Therefore, it has developed over the years and different manufacturers have different designs, but they all have the same function and operate in a similar way. The catalytic converter converts the emissions from vehicle exhaust to less harmful gases using a catalyst, which speeds up the rate at which the poisonous gases are altered. The catalyst will remain unchanged through out the process since it only acts as a support mechanism to see that the conversion of the gases is at a high speed. The catalysts used are mainly Platinum (Pt), Palladium (Pd), Rhodium (Rh) and Vanadium (V) and since they are rare, they are among the most expensive parts of vehicles. However, oxides of base metals like Zinc (Zn), Aluminum (Al) and Magnesium (Mg) are also used as catalysts, but their effectiveness is minimal making the precious metals be used by most manufacturers (Mohiuddin, 2007). The catalytic converter is one of the most effective devices for fighting air pollution as it reduces more than 80% of exhaust gases, which cause air pollution. The exhaust from car engines combustion has various gases and elements, which can contribute to air pollution, Carbon Monoxide, other hydrocarbons, and Nitrogen Oxides, but Nitrogen gas, carbon dioxide, and water vapor are the main ones. Carbon Monoxide, other hydrocarbons, and Nitrogen Oxides are responsible for the pollution caused by cars, since Carbon monoxide is poisonous and can kill if it is inhaled in large amounts. Hydrocarbons result from incomplete combustion of fuel and when released into the air they form smog, which is a form of air pollution. Nitrogen oxides cause acidic rain when released to the atmosphere and the catalytic converter will reduce the amounts of these gases that are released into the atmosphere. The catalytic converter is made out of steel it is located along the exhaust pipe, and has a porous ceramic constitution where the exhaust gases are passed through. The ceramic structure has many passages to create a large surface area for gases to pass and the passages are of different shapes. Catalysts and inorganic oxides like gamma Alumina, Ceria and Zirconia are applied on the surfaces of the porous structure where the exhaust gases will be passed for the reactions to occur at the catalytic sites (Mohiuddin, 2007). Nowadays, most cars are equipped with three-way catalytic converters to reduce the levels of harmful gases from car exhausts. There are two parts of these converters, which perform in a similar way, but they will eradicate different pollutants. The honeycomb is placed inside the converter to increase the surfaces area for reactions to occur and to reduce the amounts of catalysts used since they are expensive. When the exhaust from the vehicles is exposed to the catalysts, chemical reactions will occur which will convert the harmful gases into harmless compounds. Modern vehicles will undergo the conversion process through main two processes. The reduction catalyst The oxidation catalyst The reduction catalyst is the first stage of conversion where the exhaust gases go through the honeycomb, which is coated with the catalysts platinum and rhodium. At this stage, the exhaust gases that are converted to less harmful gases are the nitrogen compounds, which are broken down into nitrogen and oxygen. Nitrogen and oxygen are not harmful and thereby the catalytic converter functions to reduce the levels of nitrogen compounds, which are harmful when released to the atmosphere (Mohiuddin, 2007). The oxidation catalyst is the second stage where hydrocarbons and carbon monoxide are oxidized and the catalysts used in the reactions are palladium and platinum. Theses catalysts reduce carbon monoxide and hydrocarbons to carbon dioxide and water, which are not harmful to the environment. The oxygen produced during the first stage is used for further oxidizing of the carbon compounds. Control of the engine emissions is crucial since it will determine the amounts of gases that are emitted into the atmosphere. The engine management system is used for this purpose and car manufacturers will use an oxygen sensor, which is placed on the upper side of the converter. The oxygen sensor transmits a voltage reading to the computer mechanism of the car so that a balanced amount is kept at all times. The voltage reading will vary depending on the amount of oxygen in the exhaust but the ideal air fuel to gasoline ratio is 14.7: 1. If it occurs that the ratio is less than that, there will be fuel in the exhaust and this creates a rich condition. If the ratio is higher than that, it is not appropriate and the engine mechanism will have to control the amounts of air. The reading of the air to fuel ratio made by the oxygen sensor is utilized by the engine mechanism to ensure that there is a balance in oxygen in the exhaust gases, and this aids in controlling the catalytic reactions. Efficiency of the catalytic converter is determined by various factors which include flow distribution of the exhaust gases, substrates properties, channel diameter, channel length, precious metal loading, and cross-sectional area just to name a few. When a converter is working under perfect conditions, it eliminates 98-99% of Carbon dioxide, 95% of Nitrogen oxides, and more than 95% of hydrocarbons. Conversion efficiency increases as the speed of the car increases since the conversion process will require high temperatures to be undertaken efficiently. When the catalytic converter fails, it will restrict the movement of gases in cars since it blocks the flow of gases in the exhaust. This reduces the performance of the car and the car exhaust will produce some bad smell. In the worst case scenario, the car can be prevented from starting and this means that the oxygen sensor need to be in a good condition since it is responsible for ensuring that the catalytic reactions take place. The catalytic converter is a crucial device to install in car since it protects the environment from pollution by converting harmful gases produced by combustion of fuels. Oxidation of the compounds produces less harmful compounds, which when released into the atmosphere will not cause air pollution. Reference Mohiuddin, A and Nurhafez, M. (2007). Experimental Analysis and Comparison of Performance Characteristics of Catalytic Converters Including Simulation. International Journal of Mechanical and Materials Engineering (IJMME), Vol. 2 No. 1, 1-7. Read More