What are the distinctions of SCR,DOC,DPF?

In order to fully implement the new national standard emission regulations and meet the continuously improving vehicle exhaust emission standards, SCR, DOC, DPF, and other advanced technologies are increasingly being employed in the field of trucks. Within the diesel vehicle exhaust gas treatment system, SCR, DOC, and DPF are commonly utilized technical devices with distinct functions and operational principles. Let's delve into their specifics.

1. SCR（Selective catalytic reduction）

In the process of modern industrial production and energy utilization, the emission of nitrogen oxides is a serious environmental problem, because they have potential harm to the atmospheric environment and human health. SCR technology is an important technology developed to solve this problem. This is a selective catalytic reduction technology, which is often used to reduce nitrogen oxide emissions during combustion, and is widely used in the exhaust gas treatment of diesel engines to effectively reduce nitrogen oxide emissions generated during combustion.

In SCR technology, the flue gas is first pretreated, including steps such as dust removal and desulfurization, to ensure the normal operation of the catalyst. By spraying a reducing agent (urea solution) into the flue gas, the nitrogen oxide is converted into harmless nitrogen and water vapor by the action of a catalyst. At the same time, the catalyst plays a catalytic role to accelerate the reaction. Finally, the flue gas after denitrification treatment enters the atmosphere to achieve the purpose of reducing nitrogen oxide emissions.

Advantages: 

SCR technology has high efficiency in reducing nitrogen oxide emissions, can significantly reduce harmful nitrogen oxide emissions, and is conducive to vehicles to meet more stringent emission standards; Compact process equipment and reliable operation.

Disadvantages: 

the composition of flue gas is complex, and some pollutants can lead to catalyst poisoning; Highly dispersed dust particles can cover the surface of catalyst and reduce its activity. High investment and operating costs require regular replenishment of urea solution, which increases the operation and maintenance costs of the vehicle.

2. DOC（Diesel oxidation catalyst）

DOC system uses catalyst to oxidize carbon monoxide and hydrocarbons in tail gas to carbon dioxide and water vapor, reduce harmful gas emissions, and indirectly reduce PM particle emissions, thereby improving air quality, protecting the environment and human health.

Advantages: 

The DOC system is relatively simple and reliable, the cost is low, and the purification effect of carbon monoxide and hydrocarbons is good.

Disadvantages: 

DOC system itself does not have any effect on nitrogen oxides, and it needs to be used in combination with other technologies to achieve a comprehensive exhaust gas purification effect; Excessive sulfur and phosphorus are produced in the tail gas, which can easily lead to the failure of the device.

3. DPF（Diesel particulate filter）

DPF is a device that reduces particulate matter in the exhaust gas by filtering. After capturing a certain amount of particulate matter, the system burns the accumulated carbon particles to convert solid particulate matter into gaseous matter, thereby reducing particulate matter in the exhaust. Typically, DPF employs a wall-flow filter, which relies on alternately blocking the inlet and outlet of the carrier hole and forcing the air flow through the porous wall to trap particles. When the device captures particles, it also oxidizes the captured particles to regenerate the DPF.

Advantages: 

DPF technology can capture and reduce particulate matter emissions from diesel vehicle exhaust, which is of great significance to improve air quality and reduce the impact on human health.

Disadvantages: 

Regular regeneration operations are required, which may increase vehicle maintenance costs; When excessive ash is produced in the tail gas, it is easy to cause the device clogging. When the active and passive regeneration process cannot be resolved, the DPF filter device needs to be replaced.

In general, SCR is primarily utilized for the abatement of nitrogen oxides, DOC is predominantly employed for the reduction of carbon monoxide and hydrocarbons, and DPF is chiefly employed for the mitigation of particulate matter. Typically, these three technologies are integrated to ensure that diesel vehicle exhaust emissions comply with environmental regulations and mitigate adverse impacts on the environment and human health.

The continuous upgrade of diesel standards has provided stronger assurance for the advancement of domestic emission regulations. In the future, the diesel vehicle industry will further move towards standardization, normalization, and smart technology. GRWA will adapt to these industry trends, continuously evolve, and progress accordingly.