Air Pollution

14.1 Introduction Air pollution can be defined as: addition to our atmosphere of any materials which will have an adulterous effect on our life. The main pollutants are carbon monoxide (CO), Hydrocarbon (HC), oxides of Nitrogen (NOx), and smoke There are two general types of aerosols: Neutral particles such as dust, soot, fly ash Condensation nucleus such as chlorides salts, sulfuric acid, etc… 14.2 Air pollutant sources of IC engines 1. Exhaust pipe (silencer) combustion (65-85) % (HC, CO, NOx) 2. Crank case breather (20%), (HC and UHC) 3. Fuel tank breather (5)%, evaporation of volatile HC) 4. Carburetor (5-10)%, as head evaporation and leakage of fuel 14.3 Control of engine emissions 1. Modification of engine component and fuel to reduce pollution sources: a. Reduce compression ratio, hence reduce combustion temperature which leads to less NOx and decrease exhaust temperature. b. Increase idle run from (400-450) to (700-900) RPM to get linear mixture and less pollution c. Shorter chock period d. Exhaust gas recirculation (EGR) e. Air injection in to the hot escaping gas can be reduced from emissions of HC, CO, and aldehydes by oxidations Aldehydes [HCOOH]

f. Use thermal reactors: which are large insulated exhaust manifolds, to increase the effect of temperature, time and homogeneity of the exhaust gases. g. Catalytic convertor : such systems are used to decrease HC and CO by oxidation catalytices and NO by reducing catalytic. h. Crankcase ventilation system 2. Design of new engine a. Use supercharging b. gas turbine can be used in automobile (continuous combustion) c. Two stage combustion d. Striling engine e. Battery engine or gas engine may be used 12.4 Analysis of exhaust gases: to measure exhaust products, one of the following methods are used: 1. Orsat method (absorption method): it has good accuracy, but it takes very long time. 2. Infrared Analyzer: This method are based on the principle that, the automatic gases absorb in the fried energy and sparted (more or less) wave length, the absorbed energy raising the temperature and pressure of gases, this gives continuous testing   3. Flame analyzation method: It is based on the fact a flame of pure hydrogen contains a negligible amounts of ions while the addition of even traces of organic components produces large amount of ionization. 4. Gas chromat graphy method: It’s a physical method for a separating mixture into its components. The procedure is to inject the measurement sample into the column (long tube contains the stationary phase as cellulose). Each component has a certain solubility in the stationary phase and leaves the column at a certain time.