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Preparation and purification of catalytic additive in exhaust gas system of diesel engines based on urea for production of diesel exhaust fluid (DEF)

Catalytic additives in the combustion system of diesel engines are designed to reduce the presence of harmful substances in exhaust gases. These types of liquids are derived from carbonyl diamide aqueous solution (urea).

As it's known, carbamide is widely used in agriculture as a mineral fertilizers' basis. Although, its solution also implies the basis of the aforementioned catalytic reagent. To make it, carbamide undergoes dissolution and purification stages.

Due to heat absorption under the carbamide dissolving process, the solution temperature is essential to be controlled during its formation. Under non-compliance with dissolution temperature conditions, the quality of the inlet solution can be worsened by low and high temperatures. Besides, dissolution conditions strongly affect the further purification of reagents. A substantial problem during dissolution implies the formation of a colloidal solution, whose already difficult enough filtration requires high operating expenditures.

preparation and purification of catalytic additive in exhaust gas system of diesel engines based on urea for production of diesel exhaust fluid (DEF)

Carbamide solution preparation essentially depends on inlet product quality. As it's known, there are several carbamide grades that differed by quality implying the number of additional impurities. The anti-cacking agent also essentially affects the solution quality, existing in granular carbamide. Single carbamide grade varies essentially depending on the manufacturer and the batch. Thus, when adding water, single carbamide grade can form solutions of different densities of colloidal and mineral impurities, including diverse coloration. Thus, the inlet product composition has to be carefully analyzed.

The solution quality is essentially affected by the water involved in the dissolution process. Its impurities can affect the final solution quality and lead to the excess of permissible reagent parameters limit. Thus, when manufacturing a catalytic additive, it’s necessary to prepare high-quality demineralized water with a minimum salt ions concentration.

Although, even strict following of the above processes can’t guarantee the occurrence of top-grade reagents without using additional solution purification. Thus, after the proper selection of parameters for carbamide dissolution, it requires filtering. One of the best carbamide filtration methods lies in its processing in microfiltration systems. Microfiltration separates suspended and colloidal impurities, including anti-cacking agents from the solution, thereby, making a stable solution without the precipitate formation and impurity damage to the dosing equipment for this reagent.

Video of carbamide microfiltration system:

One more task during carbamide solution purification lies in removing biuret and cations of inorganic salts (calcium, magnesium, sodium, potassium…). Some impurities are added to the water solution, while some are already included in carbamide. The task of their removal can be solved by using ultrapure water during dissolution, or by ion exchange of the ready-mixed solution. Selection of purification from the above impurities depends on many conditions, like the quality of inlet carbamide, its grade, and other data obtained during analyze of implemented technology.

Litech Aqua is a manufacturer of fluid filtration equipment. One of our specialties lies in carbamide solution purification.

If you have such a request, please feel free to contact us. Our experts will do their best to assist you.


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