DEF is a liquid solution containing 67.5% deionized water and 32.5% urea. It is sprayed into diesel engines’ exhaust streams to break down dangerous nitrogen oxide (NOx) emissions into harmless nitrogen and water vapor.
The development of DEF started in the 1990s as diesel engine manufacturers were working to meet stricter emissions regulations, especially for NOx. Researchers found that injecting a urea-based solution into the exhaust could significantly reduce NOx emissions through a chemical reaction. After extensive testing, the use of DEF systems was implemented in the mid-2000s on most new diesel trucks in North America and Europe.
DEF provides the necessary reactant for selective catalytic reduction (SCR) systems on diesel vehicles. SCR systems convert NOx into N2 and H2O using a catalyst and DEF. By converting NOx emissions, DEF helps diesel vehicles meet strict emissions standards and reduces smog-forming pollutants. Learn all about “What is DEF for diesel” in this blog post by Azure Chemical.
Contents
How DEF Works
Diesel Exhaust Fluid (DEF) is a liquid solution that helps lower diesel engines’ nitrogen oxide emissions. It works through a process called Selective Catalytic Reduction (SCR).
DEF’s main ingredient is urea, which breaks down into ammonia when injected into the exhaust stream. The urea solution is carried in a separate tank from the fuel tank and injected in small amounts into the exhaust upstream of a catalyst.
The ammonia produced from the urea reacts with the nitrogen oxides (NOx) in the exhaust and converts them into nitrogen gas and water vapor through a chemical reaction. This reaction occurs on a catalyst substrate’s surface inside the SCR system.
Most modern diesel engines are equipped with an advanced DEF injection system. This consists of a DEF tank, DEF lines and pumps, a DEF injector, and an SCR catalyst. The DEF pump meters the correct amount of fluid based on engine operating conditions. The DEF injector sprays it into the exhaust stream, where the hot gases help evaporate the droplets before they reach the catalyst.
By reducing NOx emissions, DEF helps diesel vehicles meet stringent emissions regulations and run cleaner. It’s a key component of modern diesel engine technology.
DEF Specifications
Diesel Exhaust Fluid (DEF) has specific quality standards per the ISO 22241 specification. These standards ensure that the DEF used in diesel vehicles meets certain requirements for optimal emissions control.
DEF Concentration
The ISO 22241 standard requires DEF to have a urea content between 31.8% and 33.2% by weight, corresponding to an aqueous urea solution between 32.5% and 33.2%.
Approved Containers
DEF is commonly packaged in various containers including drums, totes, bottles, or bulk tanks. All containers must be made from approved materials like polyethylene, polypropylene, or stainless steel. Containers cannot be made of galvanized, bare, aluminum, or zinc-coated steel, as these materials can contaminate the DEF.
Purity Requirements
To avoid potential damage to SCR systems, The DEF solution must have a minimum urea purity of 96.0%. The concentration levels of individual impurities like Al, Ca, K, Na, etc. are also restricted.
Adhering to these quality standards ensures that the DEF used by diesel vehicles meets the specifications for the proper functioning of SCR systems for reduced NOx emissions. Proper DEF quality is critical for emissions compliance.
Benefits of Using DEF
Diesel Exhaust Fluid (DEF) provides several important benefits for diesel engines.
By reducing the nitrogen oxide emissions from diesel exhaust, DEF helps mitigate air pollution from diesel vehicles.
As emissions regulations have become more stringent over the years, DEF has become essential in bringing diesel vehicles into compliance. Today, all new diesel vehicles utilize DEF systems to meet emissions standards. Without DEF, diesel engines would not be able to achieve the ultra-low emissions levels required by regulations.
In addition to enabling compliance, DEF also helps improve the fuel efficiency of diesel engines. By reducing engine emissions, DEF lowers the need for fuel-wasting exhaust gas recirculation (EGR) rates, allowing the engine to run more efficiently. DEF’s impact on fuel efficiency varies, but most estimates suggest a 2-5% improvement when DEF is used. These fuel savings directly translate into cost savings for the vehicle operator.
In summary, DEF provides cleaner air, regulatory compliance, and improved fuel economy. These substantial benefits make DEF an integral part of modern diesel engine operation. Going forward, DEF will continue to play a key role as manufacturers work to further enhance diesel vehicles’ efficiency and emissions performance.
Potential Drawbacks of DEF
Diesel Exhaust Fluid (DEF) provides many benefits for diesel engines and emissions, but there are also some potential drawbacks.
Additional Cost
DEF adds extra cost to owning and operating a diesel vehicle. The fluid itself is not overly expensive, but it’s an additional fluid that requires routine refilling. The DEF system also adds complexity to the vehicle, increasing maintenance costs.
Refilling/Replacing DEF
DEF has a limited lifespan and tank size, which means refilling or replacing it regularly. The fluid crystallizes when it gets old and can clog the DEF system. This requires staying on top of refilling/replacing DEF per the manufacturer’s schedule.
DEF Freezing
DEF freezes around 12° Fahrenheit. In very cold climates, steps may need to be taken to prevent the DEF tank and lines from freezing up, which could prevent the vehicle from running. This may require DEF heating systems, parking in a garage, or using DEF blends for extreme cold temperatures.
Properly maintaining DEF helps sustain the emissions performance of your diesel vehicle. Monitor fluid levels, refill responsibly, and take steps to prevent freezing. With routine care, your DEF system will operate reliably for the life of your vehicle.
DEF Quality Standards
Diesel exhaust fluid (DEF) must meet precise quality standards for optimal performance and engine protection.
The International Organization for Standardization (ISO) standardizes DEF worldwide. The current ISO specification is ISO 22241, which defines the required properties and test methods for DEF.
All DEF sold in the United States and Canada must be ISO-compliant and certified by the American Petroleum Institute (API). Certified DEF will have the API logo on the packaging.
Using poor quality or contaminated DEF can cause serious problems. It may not properly react in the selective catalytic reduction system, leading to increased emissions. Contaminants and impurities can also cause crystallization and clogging of system components.
The most common DEF quality issues are:
- Contamination from dirt, debris, other fluids, or water ingress
- Dilution from improper mixing
- Degradation from heat and age
Poor-quality DEF can damage expensive components like catalytic converters and cause drivability issues. Only purchase DEF from reputable manufacturers and avoid any fluid that does not meet ISO 22241 or API guidelines. Proper storage and handling are also essential to maintaining DEF integrity.
DEF Availability
DEF is widely available at most truck stops, fuel stations, and auto parts stores across the United States.
This broad availability makes it easy for diesel pickup owners and truck drivers to find DEF when needed.
The most convenient places to find DEF are truck stops with diesel pumps.
In addition to truck stops, many gas stations and fuel retailers also carry DEF if they offer diesel fuel. Some states even require DEF to be available wherever diesel is sold for highway use.
The widespread availability of DEF makes compliance with emissions regulations easier for both professional truck drivers and personal pickup owners. Having DEF pumps next to diesel fuel dispensers at major truck stops also promotes convenience and proper use.
The Future of DEF
Diesel exhaust fluid (DEF) has become integral to diesel engine emissions control systems in the past decade. As emissions regulations become stricter, particularly for heavy-duty vehicles, DEF’s role will likely increase further.
Several trends are expected in the future of DEF:
Stricter Emissions Regulations
Regulations like Euro 7 in Europe and EPA Tier 5 in the US will require even lower NOx emissions from diesel vehicles. This will necessitate improved SCR systems and likely higher DEF dosing rates. Automakers are investing heavily in advanced SCR technologies to meet these standards.
New DEF Technology
Research is ongoing to optimize DEF performance. This includes studying new DEF formulations with enhanced thermal stability and low-temperature performance. Improved DEF pumps, injectors, and sensors are being developed to precisely control DEF dosing.
Frequently Asked Questions
You asked, we answered:
What Is DEF And Why Is It Used In Diesel Engines?
DEF, or Diesel Exhaust Fluid, is a liquid solution used in diesel engines equipped with Selective Catalytic Reduction (SCR) technology to reduce harmful nitrogen oxide (NOx) emissions. DEF is made of high-purity urea (32.5%) and deionized water (67.5%) and is injected into the exhaust stream, where it helps to convert NOx into nitrogen and water, which are harmless to the environment.
How Often Do I Need To Refill DEF In My Diesel Vehicle?
The frequency at which you’ll need to refill DEF in your diesel vehicle depends on your engine’s consumption rate and how you use your vehicle. Most modern diesel vehicles are equipped with a gauge that indicates the DEF level, similar to a fuel gauge. Under normal driving conditions, DEF is typically refilled during regular service intervals. It’s generally a good practice to check your DEF levels regularly and top off as needed.
Can I Use Any Type Of DEF In My Diesel Engine?
It’s important to use DEF that meets the standards set by the International Organization for Standardization (ISO), particularly ISO 22241. This ensures the purity and quality of the DEF, which is crucial for the proper functioning of the SCR system and to avoid potential damage. Always check your vehicle’s owner manual or consult with the manufacturer for their specific DEF recommendations.
What Happens If My Diesel Vehicle Runs Out Of DEF?
If your diesel vehicle runs out of DEF, the vehicle’s performance will be de-rated, and you may see a reduction in power or speed. Modern diesel engines are designed to comply with strict emission regulations, and running out of DEF could lead to the vehicle’s control system limiting its functionality to prevent excessive emissions. In some cases, the engine may not start until DEF is replenished. It is therefore important to ensure that you maintain an adequate level of DEF in your vehicle.
In Conclusion
While DEF is today’s standard SCR reagent, alternatives are being explored. These include solid or pelletized reductants that could simplify handling and refilling compared to liquid DEF. Ammonia gas systems are also being researched, which would avoid the need for an additional fluid altogether. However, DEF is expected to remain the primary choice in the foreseeable future.
DEF will continue to play a critical role in diesel emissions control. While the technology may evolve, DEF will likely remain essential for meeting increasingly strict NOx regulations worldwide. Automakers and suppliers will continue innovating DEF systems to optimize performance and efficiency. Get in touch with Azure chemical to learn more about DEF’s importance for your diesel.
