During the operation of diesel engines, various exhaust pollutants are produced. To reduce the impact on the environment, multiple exhaust emission treatment technologies have emerged, purifying the exhaust from different perspectives.

　　Waste gas recirculation (EGR) technology is one of the common means of exhaust gas treatment. This technology introduces part of the exhaust gas emitted by the engine into the intake pipe, mixes it with fresh air and then re-enters the cylinder to participate in combustion. As the exhaust gas contains a large amount of inert gases such as carbon dioxide, these gases do not participate in the combustion reaction, but can absorb the heat during the combustion process, lower the combustion temperature, and thereby suppress the formation of nitrogen oxides. In practical applications, the EGR system accurately controls the recirculation volume of exhaust gases based on the engine's operating conditions, such as speed and load, ensuring the engine's power performance while effectively reducing nitrogen oxide emissions.

　　Particulate capture technology is aimed at particulate matter in the exhaust gas of diesel engines. The particulate matter in diesel engine exhaust mainly consists of soot particles and ash. The particulate filter acts like a "filter", installed in the exhaust pipeline, capable of intercepting the particulate matter in the exhaust. The common material of particulate capture equipment is a ceramic honeycomb structure. When the exhaust gas passes through, the particulate matter is blocked on the wall of the channel. As particulate matter accumulates continuously, the particulate filter will become clogged, affecting the exhaust back pressure. At this point, it needs to be regenerated. The regeneration methods are divided into active regeneration and passive regeneration. Active regeneration is to increase the temperature inside the particulate filter through electric heating, fuel combustion assistance and other means, so that the particulate matter burns and is discharged. Passive regeneration utilizes oxygen and a catalyst in the exhaust gas to slowly oxidize and decompose particulate matter under certain conditions.

　　Catalytic conversion technology is also a key technology for treating diesel engine exhaust. Three-way catalytic converters are often used in gasoline engines, while the catalytic converters mainly used in diesel engines are oxidation catalytic converters (DOC) and selective catalytic reducers (SCR). The oxidation catalytic converter can oxidize carbon monoxide and hydrocarbons in the exhaust gas into carbon dioxide and water, effectively reducing the content of these pollutants. Selective catalytic reducers target nitrogen oxides. By injecting urea solution into the tail gas, under the action of a catalyst, the ammonia gas produced by the decomposition of urea undergoes a chemical reaction with nitrogen oxides, generating harmless nitrogen and water, thereby achieving a reduction in nitrogen oxide emissions. SCR technology is widely applied in heavy-duty diesel vehicles. To ensure its normal operation, urea solution needs to be replenished regularly, and the activity and stability of the catalyst must be guaranteed.

　　In addition, there are also some auxiliary technologies used to optimize the treatment effect of exhaust gas emissions. For instance, in the case of fuel additive technology, adding specific additives to diesel can improve the combustion performance of the fuel and reduce the generation of particulate matter and nitrogen oxides. And the optimization of the engine management system, by accurately controlling parameters such as fuel injection volume, injection time, and intake air volume, enables the engine to burn more completely, reducing the generation of exhaust pollutants from the source.

　　A variety of exhaust emission treatment technologies work in coordination to purify diesel engine exhaust from different aspects, playing a significant role in reducing pollutant emissions and protecting the environment.