Titchenko Prospects for the use of dry carbamide in diesel exhaust gas aftertreatment systems

Improvement of diesel exhaust gas aftertreatment systems is one of the most urgent methods of technical competition with the electric transmission, which has been developing rapidly in recent times. The search for the most optimal technical solutions will reduce the environmental load when using diesel engines. This article discusses the prospects for the use of dry carbamide in neutralization systems of diesel engines. A dry carbamide system is free from a significant drawback of the widely used SCR Nitrogen Oxide Reduction System. Such systems are not resistant to low temperatures below -11 °C and require heating, which entails significant energy costs and design complexity. The methods for the direct use of ammonia for the reduction of nitrogen oxides are known. Amminex Company uses ammonia bound in the form of salts. A design that already has practical application is considered. The buses used blocks, generating the required amount of ammonia. One set is enough to work for one two days. Blocks are replaced by infrastructure. The design is simple enough and undoubtedly efficient. There are also patents describing devices based on direct thermolysis of carbomide. In this case, it is possible to create a compact design that requires practical application. The main reactions occurring upon receipt of ammonia from a solution (urea), ammonia salts, and dry carbamide are presented. The features of thermolysis at various heating rates and temperature levels are considered. The paper analyzes the reactions proceeding in three design options. An energy analysis has been carried out and a conclusion has been drawn on the advantage of direct thermolysis of carbamide. A design variant of the exhaust gas aftertreatment system for diesel engines using direct thermolysis is proposed. Based on the results of a wide analysis, it was concluded that the structures constructed on the basis of direct thermolysis of dry solid carbamide are promising.

ecology, diesel engine, neutralization system, nitrogen oxides, carbamide, thermolysis, ammonia