To this end, some city governments have formulated corresponding laws and regulations in conjunction with relevant departments. The Guangzhou Municipal Government promulgated the Notice on the Basic Sale and Use of Leaded Gasoline and the Provisions on the Prevention and Control of Motor Vehicle Exhaust Pollution in Guangzhou. The Beijing Municipal Government has successively issued the Notice on Taking Urgent Measures to Control Air Pollution in Beijing, the Resolution on Further Implementing Air Pollution Prevention Measures to Improve Environmental Quality, and the Beijing Light Vehicle Exhaust Pollutant Standard organized and implemented by the Municipal Environmental Protection Bureau. These local laws and regulations mainly control the pollution of motor vehicle exhaust to the atmospheric environment and give the general public a clean atmospheric living space.
1, harmful components and hazards of automobile exhaust
The tail gas emitted by automobiles, except nitrogen and oxygen in the air, combustion products CO2 and water vapor, are harmful. Some toxic substances in the exhaust gas emitted by automobile engines are caused by incomplete fuel combustion or low gas temperature. Especially in sequential starting, poor injection of injector and overload operation. Fuel oxidation can't burn well, and it will produce a lot of CO, HC and soot. The other part of toxic substances is the general name of nitrogen oxides (nitrogen oxides (nitrogen oxides, NO and NO2) formed due to the high temperature and high pressure in the combustion chamber.
The above-mentioned CO is a colorless and odorless toxic gas, which is not easy to react with other substances and becomes a relatively stable part of the atmospheric composition, and can stay for 2 ~ 3 years. When people inhale too much CO, CO can combine with heme in blood, making blood unable to absorb oxygen and deliver oxygen, leading to poisoning death. The pollution it causes is called the first exhaust pollution of automobile exhaust.
CH compounds, especially olefins, will have photochemical reactions with nitrogen oxides in the air under the action of sunlight and ultraviolet rays, and generate smog-like substances such as ozone and aldehydes, which will irritate people's throat, eyes, nose and other mucous membranes. It not only harms people and animals, but also destroys the ecological environment, seriously affects the growth of crops, reduces agricultural output, and has carcinogenic effects. It has become the second largest public hazard of automobile exhaust emission.
MOx is a general term for NO and NO2, in which NO has stronger binding ability with heme in blood than CO .. It is easy to poison people and die. NO2 is a brown toxic gas with a special pungent smell, which damages people's eyes and lungs. It is the main cause of acid rain, climate change and smog. It has become a public hazard of automobile exhaust.
Particulate matter emitted by automobile exhaust is generally composed of porous carbon particles with a diameter of 0. 1 ~ 40μ m, which can attach toxic substances such as SO2 and benzopyrene, and has an unpleasant smell, which is extremely harmful to human respiratory tract (carbon particles with large particle size can precipitate quickly and are not easy to be discharged from the lungs). In addition, lead compounds and sulfur compounds are also harmful components.
To sum up, the pollutants emitted by automobile exhaust have brought serious pollution to the atmospheric environment on which human beings depend. In densely populated areas such as traffic trunk lines, the exhaust height is close to the human breathing zone, which has caused serious harm to human health. Therefore, effective measures must be taken to reduce or eliminate automobile exhaust emissions.
2. Automobile exhaust purification technology.
Due to the serious dispersion and fluidity of automobile operation, it also brings certain limitations to the purification technology. In addition to developing internal purification technology, we should also vigorously develop external purification treatment technology. This should start from two aspects: first, control technology, mainly to improve the burning rate of fuel, install anti-pollution treatment equipment and develop new engines; Second, administrative means, such as scrapping and updating, eliminating old vehicles and developing new vehicles (i.e. vehicles without pollutant emission), start with controlling fuel use standards.
2. 1 Switch to automobile fuel
(1) Replacing leaded gasoline with unleaded gasoline can reduce the emission of toxic substances in gasoline tail gas.
First of all, pay attention to the switch of automobile oil. Replace tetraethyl lead gasoline with unleaded gasoline. This gasoline is based on methyl butyl ether, which not only contains no lead, but also can reduce carbon monoxide, nitrogen oxides and hydrocarbons emitted by automobile exhaust. At present, in order to reduce automobile exhaust emissions and improve the quality of urban atmospheric environment, the state has stipulated that leaded gasoline will be basically used nationwide from 1 July 19991day. Since July 2000 1, leaded gasoline has basically been sold in the market. Because there is lead in gasoline, the antiknock agent tetraethyl lead is added, which is volatile. Even at 0 degrees Celsius, volatile lead powder exists in the air in the form of steam and smoke. However, the degree of lead pollution is closely related to the traffic density (the number of vehicles passing per hour) and the lead content in gasoline.
Although the urban traffic density in China is lower than that in developed countries, the lead pollution caused by the burning of leaded gasoline cannot be ignored. Because lead is a cumulative poison, it enters the human body through people's breathing, drinking water and food. The toxic effect on human body is to corrode hematopoietic system, nervous system and kidney. Toxic effects such as vascular system, reproductive system and cancer teratogenesis may also occur.
⑵ Add additives to change the fuel composition.
Mixing methanol fuel with 15% or water gasoline fuel with 10% moisture in gasoline can reduce or eliminate the pollution effects of carbon monoxide, nitrogen oxides, hydrocarbons and lead dust to some extent. If "methanol fuel" is used, it is a fuel made by mixing methanol and other alcohols with gasoline. When methanol accounts for 30% ~ 40%, the pollutants emitted by automobile exhaust can be basically eliminated.
⑶ Choose a suitable lubricating additive-mechanical friction improver.
Adding a certain amount (3%-5%) of solid additives such as graphite, molybdenum disulfide and polytetrafluoroethylene powder to engine oil can save about 5% of engine fuel. In addition, the use of solid lubricant can greatly improve the sealing performance of automobile engine cylinder, increase cylinder pressure and make combustion more complete. Reducing the content of CO and hydrocarbons in tail gas emissions can reduce the pollution to the atmospheric environment.
⑷ Using green fuel can also reduce the emission of toxic gases in automobile exhaust.
A research institute in Ohio, USA, said that "soybean diesel" can be obtained by mixing soybean oil with methanol and caustic soda, and then removing glycerol. "Soybean diesel oil" is mixed with ordinary diesel oil at a ratio of 3∶7, which can be used for diesel vehicles. It can greatly reduce the sulfide, hydrocarbon, carbon monoxide and smoke emitted by the engine when it works. Therefore, it is called green fuel.
5] Use a variety of fuels as fuel sources for automobiles.
With the development of science and technology and the wide application of computers, the implementation of environmental protection regulations and energy-saving measures has been ensured: new formula gasoline, electricity, compressed natural gas, solar energy and ecological fuel cells can be widely used in automobiles. However, this kind of car is equipped with a computer, and the combination is constantly assigned in advance during driving, so that the car can play its best performance. Using computer-controlled ignition system to make rapid response to different working conditions of the engine can achieve the best fuel economy and engine power performance, and reduce the pollution of exhaust gas to the atmosphere.
[6] Save energy, benefit the environment, and vigorously promote ethanol gasoline for vehicles.
According to experts, the development of ethanol instead of gasoline can not only save energy, but also digest old grain and reduce harmful steam emitted by automobiles, which is a new topic that is conducive to protecting the environment and resources.
If the ratio of ethanol to gasoline is 1∶9, with 200,000 tons of ethanol, about 2 million tons of ethanol gasoline can be made, and only 700,000 tons of grain can be consumed by 2 million tons of ethanol. Therefore, the development and use of special ethanol gasoline can solve the conversion problem of stored grain, and can replace gasoline to some extent, alleviating the shortage of crude oil supply in China. Because ethanol is a denatured fuel produced by wheat, corn and other raw materials, ethanol and gasoline are mixed in a certain proportion, which has been included in the tenth five-year development plan. Compared with pure gasoline, carbon monoxide in automobile exhaust can be reduced by about 1/3, and hydrocarbons can be reduced by 13.4%. The popularization and use of this scheme will play an important role in improving urban air pollution and ensuring people's health.
2.2 Automobile engine internal debugging can reduce the emission of exhaust pollutants.
(1) Reduce the injection advance angle. Reducing the injection advance angle can reduce the maximum working temperature of the engine (1500℃) and reduce the production of nitrogen oxides.
⑵ Improving the quality of the injector and controlling the combustion conditions (fuel ratio, combustion temperature and combustion time) can make the fuel burn fully, thus reducing CO, HC and soot.
⑶ Adjusting the fuel supply of the fuel injection pump can reduce the power of the engine and make the atomized fuel have enough oxygen for complete combustion, thus reducing the generation of CO, CH and soot.
2.3 engine external exhaust purification measures
That is, automobile exhaust gas changes from toxic gas to non-toxic gas, and then it is discharged into the atmosphere. Thereby reducing the pollution to the atmospheric environment.
⑴ Using catalyst: carbon monoxide is oxidized to carbon dioxide, hydrocarbons are oxidized to carbon dioxide and H2O, and nitrogen oxides are reduced to N2. The catalyst used is manganese oxide-copper oxide; Metal oxides such as chromium oxide-nickel oxide-copper oxide and precious metals such as white metal (platinum). They can purify carbon monoxide and hydrocarbons. The catalytic reactor is arranged between the exhaust manifold and the muffler in the exhaust system.
⑵ Water washing: Washing, filtering and steam spraying the soot particles in the automobile exhaust through the water tank can separate the toxic substances attached to the carbon particles, so that the carbon particles can be expanded and removed.
2.4 engine internal purification treatment measures
(1) The design of the crankcase forced ventilation system: The gas (mainly unburned gas) escaping from the cylinder into the crankcase is recovered into the intake manifold to be re-combusted, which changes the pollution caused by direct discharge into the atmosphere in the past.
⑵ Exhaust gas recirculation design: The exhaust port of the engine is connected with the intake manifold through the control valve, so that the exhausted gas can be recycled and the emission of nitrogen oxides can be reduced.
⑶ Design of evaporative emission control system: Introducing gasoline vapor from carburetor float chamber into air intake system and vapor from fuel tank into storage system can greatly reduce pollutant emission.
2.5 Strengthen administrative management to reduce and eliminate the pollution of automobile exhaust to the atmospheric environment.
(1) Eliminate old cars and adopt scrapping to welcome new ones. Developing and adopting new vehicles with multiple fuels is the development direction of future automobiles. Battery car, solar car, electric car, tandem car, liquefied gas car, methanol car, etc. Use hydrogen as fuel. They are low-pollution and the most promising new cars. At the same time, at present, cars with modified automobile engines can also be diesel engines. Although the fuel cost of diesel engine is high, the amount of CO produced is small. If the emission of nitrogen oxides and dust is relatively limited, then the diesel engine car is also the best car in the future.
(2) Strictly implement national quality and technical standards and control fuel standards.
According to national regulations, substandard fuels cannot be used and inferior fuels are not allowed to be sold in the market. However, a ban on the use of leaded gasoline in cars has been issued, but it is difficult to work. The main reason is that the public does not know enough about this policy. The price difference between leaded No.70 gasoline and unleaded No.90 gasoline and No.90 gasoline is relatively large, and there is no effective measure and effective publicity. In addition, leaded gasoline is not prohibited in the surrounding areas of individual cities. The market survey results show that the stock of leaded gasoline is still large, and the mobility of vehicle transportation makes it difficult to implement the ban. Therefore, we should vigorously strengthen the propaganda and implementation of the "ban" to ensure the cleanliness of the atmospheric environment.
In order to protect the natural environment and national resources, prevent automobile exhaust from polluting the atmospheric environment and causing public hazards, and ensure people's life safety and health. The state has specially formulated environmental quality standards, pollutant discharge standards and pollutant control standards. The author believes that in order to ensure the implementation of the above laws and regulations, we can also start from the following aspects:
⑴ Vehicles driving separately: In densely populated urban areas, the traffic density is high, and the emission of automobile exhaust is relatively concentrated in a certain period of time, so the degree of air pollution in this area will increase sharply in a certain period of time, which is harmful to human health. At this time, cars can split up. On the one hand, it can solve the problems of traffic jam and difficulty in riding; In addition, it can also reduce the degree of atmospheric environmental pollution in this area and better implement the implementation of atmospheric environmental quality standards.
(2) Driving the subway, driven by electric traction. Especially in densely populated areas of big cities, opening underground passages can solve the problem of difficulty in riding and reduce atmospheric environmental pollution.
⑶ In the future construction of modern cities, we should also consider our own circular and multifunctional structural forms. Reasonably design the daily life of urban residents, completely replace cars with steps, and cars are only used outside the city. The efficient utilization of wind energy, solar energy and circulating water in cities can also make people get rid of the pollution and waste of non-renewable resources to a great extent.
(4) Strengthen and improve people's awareness of environmental protection-starting from themselves and starting from the family.
The above automobile exhaust emission is an important part of atmospheric environmental pollution. However, personal and household pollution accounts for a certain proportion of air pollution sources. The garbage, waste gas and waste water produced in people's lives not only make people enjoy convenience, but also aggravate the atmospheric environmental pollution, which is a part that we can't ignore.