Prilled AdBlue Urea Vs. Liquid Form: Which Is Best for Your Diesel Engine?

The demand for cleaner, more efficient diesel engines has led to numerous innovations in the world of automotive technology. One such innovation is the use of AdBlue (also known as Diesel Exhaust Fluid, or DEF), a solution that helps reduce nitrogen oxide (NOx) emissions from diesel engines. AdBlue is crucial in meeting stringent environmental standards like Euro 6 and EPA regulations. However, AdBlue is available in two forms—prilled urea and liquid urea—each with its own set of advantages and considerations.

This article will explore both types of AdBlue urea, compare their benefits and drawbacks, and help you determine which one is best suited for your diesel engine.

What is AdBlue Urea?

Before diving into the comparison of prilled urea and liquid urea, let’s understand what AdBlue is and how it works. AdBlue is a non-toxic solution composed of 32.5% high-purity urea and 67.5% deionized water. It is injected into the exhaust stream of diesel vehicles equipped with Selective Catalytic Reduction (SCR) systems, which are designed to reduce NOx emissions. Once injected into the exhaust gases, AdBlue reacts with the nitrogen oxides in the emissions and transforms them into harmless nitrogen and water vapor, thus significantly reducing air pollution.

Now, AdBlue can come in two forms: prilled urea and liquid urea. Let’s explore both.

What is Prilled AdBlue Urea?

Prilled AdBlue urea refers to urea in solid form, which has been processed into small, uniform pellets (also known as prills). These prills are typically around the size of a small grain of sand and have a low moisture content. The prills are easy to store, transport, and handle, making them a convenient option for some industries and specific vehicle needs.

The prilled form of urea is commonly used in industrial applications, where it can be dissolved in water to create a solution like AdBlue. The prilled urea is not typically used directly in diesel vehicles without being dissolved into a liquid form of AdBlue, so it needs an additional step before it can be injected into the SCR system.

What is Liquid AdBlue Urea?

Liquid AdBlue urea is a ready-to-use solution, consisting of 32.5% urea and 67.5% deionized water. This form of AdBlue is pre-mixed and is directly injected into the diesel engine’s exhaust system without requiring any further processing or dilution. Liquid urea is commonly used in most modern diesel vehicles, as it’s specifically designed for ease of use and quick deployment.

Unlike prilled urea, liquid AdBlue is stored in specially designed tanks within the vehicle and can be easily refilled. It is generally the most common form of AdBlue in passenger vehicles, commercial trucks, and heavy machinery.

Key Differences Between Prilled Urea and Liquid Urea

Now that we understand the basic differences between prilled urea and liquid urea, let’s take a closer look at how these two types compare in various important areas, such as handling, storage, efficiency, and performance.

1. Handling and Storage

• Prilled Urea: Prilled urea is solid, making it easier to store and transport. Due to its granular form, it does not require special storage conditions and is less susceptible to environmental factors like temperature or contamination. However, it must be dissolved in water before being used in the SCR system, which can add an extra step to the process.

• Liquid Urea: Liquid urea, on the other hand, requires more careful storage. It must be stored in temperature-controlled environments to prevent freezing in colder climates. The liquid form also requires specific containers that meet safety standards. In addition, the vehicle’s AdBlue tank needs to be regularly filled to ensure there is always enough liquid urea for the SCR system to function effectively.

2. Ease of Use

• Prilled Urea: The main challenge with prilled urea is that it must be dissolved in water before it can be used in the SCR system. This adds an additional step in the process, requiring equipment and time to properly dissolve the urea. Moreover, the dissolution process can introduce the possibility of inconsistencies, and the solution might need to be filtered to ensure purity.

• Liquid Urea: Liquid AdBlue is much easier to use, as it is ready-to-use and does not require mixing. With liquid urea, the user simply needs to top up the AdBlue tank in the vehicle, much like refilling fuel. This makes liquid urea the most user-friendly option for most consumers.

3. Cost and Availability

• Prilled Urea: Prilled urea tends to be less expensive to produce compared to liquid urea due to lower transportation and storage costs. However, the additional step of mixing it with water before it can be used makes it less convenient for everyday use. Prilled urea is more commonly used in industrial applications, such as agriculture and manufacturing.

• Liquid Urea: While liquid urea may come at a slightly higher cost due to its ready-to-use nature, it is more widely available for personal and commercial use. Refills are typically offered at service stations, and vehicles using SCR systems are designed to easily accommodate liquid AdBlue.

4. Efficiency and Performance

• Prilled Urea: The efficiency of prilled urea depends largely on how well it is dissolved and the purity of the resulting solution. If the prills are not dissolved correctly, they may not be effective in reducing NOx emissions. Additionally, the possibility of impurities in the dissolved solution may hinder the SCR process.

• Liquid Urea: Liquid urea is pre-mixed to the correct ratio and purity, making it a more reliable option for ensuring optimal SCR performance. It is designed to work efficiently with diesel engines and is more commonly used in vehicles equipped with SCR technology, where it plays a key role in reducing NOx emissions.

5. Environmental Impact

• Prilled Urea: Prilled urea, while environmentally safe when used properly, can be difficult to manage if improperly dissolved or disposed of. Inadequate handling can lead to environmental contamination, especially in agriculture where prilled urea is used as fertilizer. This form of urea may have a slightly higher environmental risk due to potential leaching into the soil and water.

• Liquid Urea: Liquid urea is generally easier to handle and transport, and it is less likely to lead to contamination. Since it is designed to be injected directly into the vehicle’s exhaust system, it poses a lower environmental risk than prilled urea in terms of handling and disposal.

6. Freezing and Temperature Sensitivity

• Prilled Urea: Prilled urea is much less susceptible to freezing compared to its liquid counterpart, making it a better option for regions with extremely cold temperatures. Since it is solid, it can be stored and transported in cooler environments without the risk of freezing.

• Liquid Urea: Liquid AdBlue can freeze at temperatures below -11°C (12°F), which can damage the SCR system if not properly managed. Special additives or heated storage systems are often required in colder climates to ensure that the liquid does not freeze in transit or in the vehicle's tank.

Which is Best for Your Diesel Engine?

The choice between prilled urea and liquid urea ultimately depends on your specific needs and application.

• Prilled Urea: If you're working in industries like agriculture or heavy machinery, where urea is used for various applications beyond just SCR systems, prilled urea may be a more economical choice. However, it requires extra steps for mixing, so it’s not ideal for regular vehicle maintenance.

• Liquid Urea: For most modern diesel-powered vehicles, liquid urea is the clear winner. It is easy to use, requires no additional mixing, and ensures the SCR system works efficiently to reduce NOx emissions. If you are a commercial fleet owner, or if you own a diesel-powered passenger vehicle, liquid AdBlue is the more convenient and reliable choice.

Conclusion

Both prilled urea and liquid urea play important roles in SCR systems designed to reduce NOx emissions in diesel engines. Prilled urea offers cost-effective benefits for large-scale or industrial applications, while liquid urea is more practical, user-friendly, and efficient for daily use in vehicles equipped with SCR technology. Understanding the differences between these two forms of AdBlue will help you make the best choice based on your specific needs and the type of diesel engine you’re working with.

Ultimately, choosing the right form of AdBlue is essential for ensuring optimal vehicle performance and compliance with environmental regulations. As emissions standards continue to evolve, technologies like SCR and AdBlue will remain critical in reducing pollution and fostering a cleaner, more sustainable future.