AdBlue - Eliminating product quality risks with the Synthesis production
Posted / Last update: 20-12-2011
The author compares the Synthesis production of AdBlue with the Decomposition of solid urea and works out the impact on quality, logistics and cost.
To fulfil the Euro IV and Euro V standards and the future Euro VI standards, the manufacturers of diesel engines for heavy means of transport adopted the SCR (Selective catalytic reduction) technology, an emission treatment system that, by using AdBlue, converts nitrogen oxides (NOx) of exhaust gasses in non-dangerous substances such as nitrogen and water vapour.
For the SCR system to work in a stable manner and without any technical problem for long periods, the AdBlue used must be of quality and comply with specific and limiting quality principles both for what concerns production and for packaging and transport.
Quality standards were defined by the CEFIC (European Chemical Industry Council) and by the International Organization for Standardisation (ISO 22241) to guarantee users that AdBlue has the performance requested by manufacturers of diesel engines.
There are two production processes of AdBlue:
1) Synthesis production - by deriving the product directly from a urea system and diluting it with demineralised water on the line of the plant
2) Decomposition of solid urea in demineralised water by using small mixing units.
The process and related risks are detailed below.
AdBlue synthesis production
The synthesis production of AdBlue assumes upstream the existence of a plant operated continuously for the production of technical urea .
A urea plant requires big investments (ca. 300 M€) and now difficult to authorise in Europe since the starting base for the reactions requires in turn NH3 (ammonia).
Moreover, synthesis production plants of AdBlue would not be justified only for producing AdBlue since the minimum critical mass of a urea plant is 200,000 tons/y of 100 % product.
The process is detailed below:
The urea is industrially synthesised by using the Bosch-Meiser process that is based on the synthesis of ammonium carbamate, from carbon dioxide and ammonia, and on the following reaction of decomposition of the carbamate that provides urea and water:
- 2 NH3 + CO2 → H2N-COONH4
- H2N-COONH4 → (NH2)2CO + H2O
 Technical urea is used for the production of glues and bonding agents and represents only 6-8 % of the overall production of urea in the world. Urea is mainly applied as fertiliser for agriculture. Technical urea has higher characteristics and therefore needs more advanced plants.
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