Chemicals | Multiparameter Analysis of AdBlue®

Dynamic viscosity, density, refractive index of AdBlue® – determine all these important parameters simultaneously with one measurement by using SVM 3001 Chemical Upgrade combined with an Abbemat refractometer.

To comply with stringent environmental regulations, reducing nitrogen oxide emissions (NOx) from diesel engines is imperative. One widely implemented solution is the Selective Catalytic Reduction (SCR) system, which utilizes a diesel exhaust fluid (DEF), commercially known as AdBlue®. AdBlue® is a solution of 32.5 % urea dissolved in deionised water. In the SCR process, urea decomposes at elevated temperatures (typically above 180 °C) to produce ammonia (NH₃). The NH₃ then reacts with NOx in the exhaust stream, converting it into nitrogen (N₂) and water (H₂O). AdBlue® is stored in a dedicated tank within the vehicle and is injected into the exhaust system in a controlled manner just upstream of the SCR catalyst.

Which parameters are determined

According to the specifications in ISO 22241:

Dynamic viscosity at 20 °C

Viscosity influences the droplet size for injection. For a well working system, consistent homogenous distribution of the spray droplets is required. ISO 22241 specifies 1.4 mPa.s.

Density at 20 °C

Density serves as a readily measurable parameter to verify the correct concentration of urea (32.5%) in AdBlue® and, consequently, ensures the correct quantity of urea is delivered to the SCR system.

Refractive Index (RI) at 20 °C

Only highly pure urea and deionised water shall be used to produce the 32.5 % AdBlue® solution. ISO 22241 specifies a range of 31.8 % to 33.2 %. Contaminants and changes in the concentration both affect RI and have an impact on function and efficiency of AdBlue®. Therefore, it is required to observe this parameter both in production and after sales.

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