EURO 5 EMISSION STANDARDS 

The Euro 5 emission standard is one of the strictest automotive standards being widely applied worldwide, including in Vietnam. The purpose of the Euro 5 emission standard is to create environmentally friendly automotive products and enhance the quality of life. 

The Euro 5 standard sets limits for emissions including carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and fine particulate matter, helping to reduce negative impacts on the environment and human health. 

To meet these stringent emission standards, Hino has implemented SCR technology on the Hino Series 500 to reduce nitrogen oxide (NOx) emissions. 

SCR EXHAUST TREATMENT SYSTEM 

SCR, which stands for “Selective Catalytic Reduction,” is an after-treatment technology that uses catalysts to remove or decompose specific chemical components and facilitate chemical reactions.  

The SCR exhaust treatment system is applied to medium and heavy-duty Hino trucks, such as the Series 500 and Series 700, to reduce nitrogen oxide emissions. 

After NOx is generated from the engine due to high combustion chamber temperatures, the excess NOx is mixed with other exhaust components and passes through the SCR system, converting it into nitrogen and water to reduce NOx levels below the emission standards.

BASIC COMPONENTS OF THE SCR SYSTEM 

1. Muffler: NOx treatment device present in engine exhaust. 
2. DCU (Dosing Control Unit): Controls the exhaust treatment system, regulating the pumping and injection of urea solution into the exhaust stream. 
3. Urea Tank: Tank containing aqueous urea solution. 
4. Cut-off Valve: Controls the flow of engine coolant to the urea tank and urea injector to prevent freezing and thawing of the aqueous urea solution. 
5. Urea Pump: Draws aqueous urea solution from the tank. 
6. Urea Injector: Sprays aqueous urea solution to chemically treat nitrogen oxides in the exhaust. 
7. NOx Sensor: Measures NOx concentration. 
8. Pre-SCR Temperature Sensor: Measures exhaust temperature before the SCR catalyst. 
9. Ambient Air Temperature Sensor: Measures the temperature of the surrounding air. 

OPERATION PRINCIPLE 

• The urea SCR system reduces NOx emissions from the engine by using ammonia absorbed by the urea SCR catalyst, which is then converted into nitrogen (N2) and water (H2O). 
• The urea solution used for the Series 500 is AdBlue, consisting of 67.5% pure water and 32.5% urea. When sulfur content (in fuel) is high, the effectiveness of the oxidation catalyst is significantly reduced by sulfur. 
• The amount of AdBlue injected is measured by the DCU, and the optimal injection amount is determined based on information received from the sensors. 
• Ammonia (NH3), necessary for the chemical reaction, is generated by injecting AdBlue into the exhaust, where high-temperature exhaust gases cause hydrolysis, which is then absorbed by the urea SCR catalyst. 
• AdBlue serves as the medium providing the ammonia component needed for NOx reduction. 
• When AdBlue is injected, hydrolysis occurs rapidly, producing the necessary ammonia to catalyze the reduction of NOx emissions into the environment. 
• Vanadium plays an important role in SCR technology as a catalyst for chemical reactions with sulfur, even at high sulfur content (up to 350 ppm). 

BENEFITS 
The SCR exhaust treatment system equipped in the Hino Series 500 aims to meet Euro 5 emission standards, complying with current regulations set by the Vietnamese Government. The SCR system limits harmful emissions, contributing to improved air quality and environmental protection. It also demonstrates Hino’s responsibility to the community by providing high-quality products and fulfilling commitments to sustainable development.