AdBlue, the critical diesel exhaust fluid (DEF) for SCR systems, relies on high-purity urea (≥99.8%) as its core ingredient—far stricter than agricultural-grade urea. This article breaks down the production process, quality requirements, and key differences from standard urea for fleet managers, AdBlue manufacturers, and auto industry professionals.
Before diving into production, it’s critical to understand why AdBlue urea is not the same as agricultural urea:
Urea production for AdBlue comprises two core phases: the synthesis of raw industrial urea and its purification to AdBlue-grade standards.
The foundation of AdBlue urea is industrial urea, synthesized from two abundant raw materials: anhydrous ammonia (NH₃) and carbon dioxide (CO₂). This process typically takes place in large-scale chemical plants.
Raw Material Preparation
Ammonia is produced by the Haber-Bosch process (nitrogen and hydrogen under high pressure/temperature).
Carbon dioxide is captured from industrial flue gases (e.g., natural gas combustion) or ammonia production byproducts.
Reaction Step 1: Formation of Ammonium Carbamate
Ammonia and carbon dioxide are fed into a high-pressure reactor (150–250 atm, 180–200℃).
They react exothermically to form ammonium carbamate, a stable intermediate:
2NH3+CO2→NH2COONH4
Reaction Step 2: Dehydration to Urea
Ammonium carbamate undergoes dehydration (a reversible endothermic reaction) to form urea and water:
NH2COONH4→CO(NH2)2+H2O
To drive the reaction forward, excess ammonia is added, and water is continuously removed from the reactor.
Crude Urea Recovery
The reactor mixture (urea, water, unreacted ammonia/CO₂) is sent to a decomposer to separate unreacted materials (recycled back to the reactor).
The remaining urea solution is concentrated via evaporation, then crystallized, centrifuged, and dried to produce crude industrial urea (purity ~99.5%).
Crude industrial urea does not meet AdBlue’s strict purity requirements—it requires additional purification steps to remove biuret, chloride, and heavy-metal impurities.
Recrystallization
Crude urea is dissolved in high-purity deionized water to form a concentrated solution.
The solution is heated, filtered to remove insoluble particles, then cooled slowly to form large, pure urea crystals.
Impurities (e.g., biuret) remain dissolved in the mother liquor and are discarded.
Ion Exchange Treatment
The recrystallized urea solution is passed through ion-exchange resins to remove trace amounts of heavy metals (e.g., iron, copper) and chloride ions.
This step is critical—even ppm-level impurities can damage SCR system components.
Vacuum Drying
Purified urea crystals are dried in a vacuum oven at low temperatures to prevent biuret formation (biuret forms at high temperatures).
The final product is AdBlue-grade urea with purity ≥99.8%, biuret ≤0.2%, and minimal trace impurities.
Once AdBlue-grade urea is produced, it is mixed with deionized water to create the final DEF:
The production of urea for AdBlue is a precise, multi-step process that goes far beyond basic industrial urea synthesis. Rigorous purification to remove biuret and impurities is critical to ensuring AdBlue works effectively in SCR systems, reducing diesel NOₓ emissions and avoiding costly vehicle repairs.
As global emission standards tighten, the demand for high-quality AdBlue-grade urea will continue to grow—making strict adherence to ISO 22241 production standards more important than ever.
Tech Blog Arc Resistance of Melamine Molding Compounds Melamine molding compounds are essential insulating materials for the electrical and instrumentation industries, widely used in mine
Tech Blog Influential Factors on Melamine Moulding Compounds Melamine moulding compounds are widely used in electronics, household utensils, and automotive parts due to their excellent
Tech Blog How to Slow Down Melamine Reactor Temperature Difference Rise Rate Melamine production via high-pressure processes (3rd-5th generation) relies heavily on reactor long-cycle operation.
JINGJIANG MELAMINE POWDER
© JINJIANG MELAMINE