The key technical challenge for different types of DPF is the regeneration of DPF during normal driving of diesel vehicles.

Types of regeneration methods:

1. Active regeneration: External heat sources are provided or supplemented for regeneration, such as engine rear injection, fuel burners, electric heating, etc.

2. Passive regeneration: relying solely on normal exhaust for regeneration.

Catalysts play a crucial role in DPF regeneration by reducing the combustion temperature of ash. Catalysts can be added to exhaust gas (FBC) using fuel additives such as cerium and iron, Or a catalytic DPF (CSF) coated with precious metal catalyst, Both methods have their own advantages and disadvantages.

The oxygen components in the exhaust gas that can be utilized during the regeneration combustion of collected ash:

——O2 component in exhaust gas: The content of O2 in exhaust gas is about 10%, and O2 regeneration requires a high regeneration temperature. When using a catalyst (such as FBC fuel carrying catalyst)>400 ℃, and without a catalyst>500 ℃ (550-600 ℃). When using O2, regeneration is rapid, but it may generate high local temperatures, leading to damage to the carrier;

——Utilizing the NO2 component in exhaust gas: NOx content in exhaust gas is about 0.01-0.1%, of which NO accounts for about 80-95% and NO2 accounts for about 5-20%. NO2 has high reactivity with ash, and the reaction temperature starts at around 200 ℃. In order to utilize NO2 for regeneration, the exhaust gas first passes through an oxidation catalytic converter to convert NO in NOx into NO2, and the regeneration reaction proceeds from NO2+C to NO+CO2. The regeneration temperature is 300-350 ℃. When using NO2, the regeneration is slow (due to the low concentration of NO2 in the exhaust), but it is relatively safe (to avoid high temperatures). The continuous regeneration system (CRT) uses this method.

The typical regeneration method of DPF system:

1. Passive regeneration system (only capable of utilizing NO2):

-CRT system: oxidation catalytic converter (DOC)+uncoated particulate filter (DPF);

-CSF system: catalyst coated DPF (regeneration temperature higher than CRT system);

-CCRT: DOC+CSF。

2. Active regeneration system:

● Regeneration using NO2:

One engine management method: Exhaust Gas Recirculation (EGR) Air intake throttling, etc;

● Regeneration using O2:

FBC (Fuel Carrier Catalyst): reduces the combustion temperature of ash;

A catalytic converter burner (delayed injection of unburned HC for combustion in DOC, increasing the temperature of DPF);

One engine management method: rear injection, etc.

Application of different types of catalysts in diesel vehicle exhaust systems:

——Fuel Carrier Catalyst (FBC): Cerium based, iron-based;

——Oxidation catalytic converter (DOC):—— Catalyst coated DPF (CSF):

——NOx adsorption catalyst (NAC):

——Selective Catalytic Reduction (SCR) of NOx:—— The combination application of the above types;

——DPF system (DPNR) that simultaneously reduces NOx and particulate matter: The DPF carrier is coated with NAC.

Combination application of different devices that simultaneously reduce NOx and particulate matter:

——DPF+EGR: Reduce PM, CO, and HC>90%, NOx by about 60%;

——DPF+NAC: To reduce PM, CO, HC, and NOx>90%, engine rear injection or additional fuel injection is required;

——DPF+SCR: Reduce PM, CO, HC, and NOx by more than 90%, requiring injection of urea solution and low fuel consumption.