Steps to environmental safety. Greening vehicles

In the previous issue of the section “Humanity. Society. Nature” we began to consider the system of environmental safety of enterprises, which should provide a comprehensive, timely and reliable assessment of indicators, the use of which will provide an idea of the degree of environmental friendliness of production, environmental efficiency of environmental activities.

One of the main sources of environmental pollution is emissions of harmful substances from working motor vehicles. Any company has a fleet of cars that provides delivery of employees to the place of work, cargo to storage warehouses, and also carry out all types of work within the company itself.

The exhaust gas composition of automobile engines gives an idea of the completeness of fuel combustion and the coefficient of excess air. By the composition of the exhaust gases, one can judge the technical condition of the engine, power system and ignition. The composition of the exhaust gases is one of the parameters that determine the suitability of car operation; with increased carbon monoxide, car operation is prohibited.

 Car exhaust gas consists of many chemical components: nitrogen, carbon dioxide and carbon monoxide, water vapor and other elements. The most toxic component is carbon monoxide - the result of incomplete combustion of the fuel and an indicator of the technical condition of the engine as a whole, its content in faulty engines reaches 10%. Therefore, when diagnosing engines, the content of carbon monoxide in the exhaust gases is primarily determined. The greatest emission of carbon monoxide occurs when the engine is idling and during acceleration.

Ways to reduce environmental pollution by toxic components of automobile exhaust

A decrease in the quantity and a change in the qualitative composition of harmful substances emitted into the environment with exhaust gases is achieved by a whole range of measures. Among them, a number of constructive developments should be noted - special designs of combustion chambers, including those with various types of exhaust gas recirculation, i.e. supplying their parts to the engine inlet, gas distribution control systems, etc. However, even when used in the design of engines all the most advanced solutions to meet the toxicity standards established, for example, in the USA, Japan and European countries, it is not possible. As a result, modern cars with gasoline engines are equipped with catalytic converters, which are ceramic material coated with a thin catalyst layer of noble metals, for example, platinum, palladium, rhodium. When the catalyst surface temperature exceeds 250-300 ° С, the carbon oxides contained in the exhaust gases are effectively oxidized, and their concentration in exhaust gases decreases many times. Hydrocarbon oxidation occurs at a higher temperature (400 ° C). Such converters have been widely used in automobiles since the beginning of the 80s, including with a carburetor fuel supply system. However, a consistent tightening of toxicity standards required the creation of neutralizers that reduce not only concentration.

The toughening of toxicity standards explains the widespread introduction of sophisticated electronic fuel delivery systems on cars. The complexity of these systems is likely to increase over time with further tightening of toxicity standards.

Unlike gasoline engines, diesel engines have significantly lower emissions of nitrogen, carbon dioxide and carbon monoxide, and water vapor, and in the past did not require the installation of special devices to reduce toxicity. However, in recent years, stricter standards of toxicity have also affected diesel engines — many models of cars with such engines already have systems for reducing exhaust toxicity, including exhaust gas recirculation, a catalytic Converter and a special particulate filter.

Control methods and standards for acceptable exhaust gas toxicity

Exhaust smoke is estimated from the density of the exhaust gas, which is the amount of light absorbed by soot particles and other light-absorbing particles contained in the gases. It is determined on the scale of the device of a compact gas analyzer-smoke meter, or a smoke detector of exhaust gases of diesel engines, which works on the principle of transmission of gas volume, or a portable digital smoke meter with access to a PC and printer. The latter is convenient for difficult-to-reach exhaust systems. The measurement of smoke is carried out in two modes of engine operation - at idle and free acceleration to the maximum shaft speed. The table shows the norms for the content of the main harmful substances in exhaust gases.

Table. Standards for the content of harmful substances in exhaust gases, g/(kWh)

The Republic of Kazakhstan joined the international Agreement on environmental requirements of the UNECE Regulations, which created a legal basis for monitoring their implementation by the state.