Introduce you to the car three-way catalytic converter

What is a three-way catalytic converter?

Three-way catalytic converter is the most important external purification device installed in the automobile exhaust system. It can change the harmful gases such as CO, CARBON monoxide, HC hydrocarbons and NOx from automobile exhaust into harmless carbon dioxide, water and nitrogen through oxidation and reduction. Because this catalytic converter can simultaneously convert the three main harmful substances in the waste gas into harmless substances, it is called three yuan.

Ternary catalytic converters working principle is: when high temperature by automobile exhaust purification device, cleaning agent of three yuan catalysts will enhance CO, HC and NOx activity of three kinds of gases, prompting the oxidation - reduction reaction, in which CO oxidation at high temperatures become colorless, non-toxic, carbon dioxide gas; HC compounds are oxidized to water and carbon dioxide at high temperatures; NOx is reduced to nitrogen and oxygen. Three kinds of harmful gases become harmless gases, so that automobile exhaust can be purified.

Reason of failure of three-way catalytic converter

1. The temperature is too high

Ternary catalytic converter does not have catalytic capacity at normal temperature, and its catalyst must be heated to a certain temperature to have oxidation or reduction capacity. Usually, the starting and burning temperature of catalytic converter is 250-350 ℃ and the normal working temperature is generally 350-700 ℃. Catalytic converter work will produce a lot of heat, the higher the heat, the higher the temperature of oxidation, when the temperature exceeds 850-1000℃, the catalyst coating is likely to fall off, carrier fragmentation. So must pay attention to control exhaust temperature rise caused by various factors, such as ignition time is too late or firing order confusion, fire, etc., this can be a mixture of unburned into catalytic reactor, cause the exhaust temperature is too high, influence the efficiency of catalytic converter.

2. Chronic poisoning

Catalyst for sulfur, elements such as lead, zinc phosphate, very sensitive, sulfur and lead from gasoline, phosphorus and zinc from the lubricating oil, the four kinds of substances and their formed after combustion in engine oxide particles are easily adsorbed on the surface of the catalyst, the catalyst can't contact with the waste gas, thus lost the catalysis, the so-called "poisoning" phenomenon.

Surface area carbon

When the car works at low temperature for a long time, the three-way catalytic converter cannot start, and the carbon smoke discharged from the engine will adhere to the surface of the catalyst, resulting in the inability to contact with CO and HC. In the long run, the pores of the carrier will be blocked, affecting its conversion efficiency.

4. The exhaust

Catalytic converter for pollutant conversion ability has certain limits, so you must minimize the original exhaust through internal purification technology. If the concentration and total amount of exhaust gas pollutants are too large, such as too thick mixture, the catalytic conversion capacity of catalytic converter will be affected and its conversion efficiency will be reduced. In addition, due to the large amount of HC and CO in the exhaust gas entering the catalytic reactor, excessive oxidation reaction will occur in it, and the oxidation reaction will generate a large amount of heat, which will cause the high temperature of the catalytic reactor and damage.

5. It does not match the engine

Even for the same engine, the same three-way catalytic converter, different models, the commonly used working interval of the engine will be different, the exhaust status will change, the installation of three-way catalytic converter will be different, which will affect the catalytic conversion effect of the three-way catalytic converter. Therefore, different vehicles should use different ternary catalytic converters.

6. The oxygen sensor fails

For the exhaust gas catalytic rate of best, inevitable in engine exhaust pipe installation of oxygen sensor and realizing the closed-loop control, its working principle is oxygen sensor to measure concentration of oxygen in flue gas, converted to electrical signals of backwardness to ECU, make the engine air-fuel ratio control in a narrow, close to the ideal area, if the air-fuel ratio big, although the CO and HC conversion rate increased slightly, But the NOx conversion rate drops sharply to 20%, so it is necessary to ensure the best air-fuel ratio, to achieve the best air-fuel ratio, the key is to ensure that the oxygen sensor works normally. If the fuel contains lead, silicon can cause oxygen sensor poisoning. In addition, improper use will also cause carbon deposition of oxygen sensors, ceramic fragmentation, heater resistance wire burning, internal circuit off and other faults. Oxygen sensor failure will lead to air fuel ratio misalignment, exhaust deterioration, catalytic converter efficiency reduced, long time will reduce the service life of catalytic converter.

Curing method of three-way catalytic converter

Three catalytic converter maintenance cycle should not be too long, generally go to 4S shop or regular repair shop for cleaning and maintenance, usually when using the car more attention to maintain the performance of the car can also reduce the composition of harmful substances in the tail gas. Usually pay more attention to the following:

1. Cars equipped with three-way catalytic converters cannot use leaded gasoline, because lead particles will cover the catalyst surface when the lead oil is burned and the exhaust gas is discharged through the three-way catalytic converter, reducing the catalyst action area, thus greatly reducing the conversion efficiency of the catalytic converter, resulting in lead poisoning of the three-way catalytic converter.

2. The unburned mixture should be avoided from entering the catalytic converter. The starting temperature of three-way catalytic converter is about 200 degrees Celsius, and the best working temperature is between 400 degrees Celsius and 800 degrees Celsius. After 1000 degrees Celsius, the precious metal composition of catalyst itself will also produce chemical changes, so as to reduce the effective catalyst composition in catalytic converter and weaken the catalytic effect. Therefore, in the process of vehicle use, we should pay attention to the exclusion of the following situations: one is too long idling; Second, ignition time is too late; Three is individual cylinder fire does not work; Fourth, it is difficult to start; Fifth, the mixture is too thick; Six is the engine burning oil, seven is the oxygen sensor failure; Eight is poor heat dissipation caused by the water temperature is too high.

3. When driving on uneven roads, special attention should be paid not to "support the bottom", because most of the three-way catalytic converters are internal catalyst carriers formed by honeycomb pottery, which are easy to be broken after collision, resulting in the failure of catalytic converters and blockage of exhaust pipes.

4, abnormal working conditions, such as tempering or repetitive stall, should be stopped in time for inspection, because these conditions can lead to permanent damage to the catalytic converter.

5. Do not cut off the ignition switch when the vehicle is running.

6. Check the three-way catalytic converters in vehicle maintenance. Check the contents are: the exhaust pipe has the same sound, this abnormal sound is usually caused by the loose exhaust pipe joint, three catalytic converter damage, catalyst replacement plug loosening and other reasons; Whether the exhaust pipe cracking or shell flattening appearance damage; Whether catalyst particles are discharged from the exhaust liner. If the three-way catalytic converter shell is damaged or particles are discharged from the exhaust tail pipe, it needs to be replaced.