REDUCTION OF NOX EMISSIONS FROM A MOTOR BY UREA INJECTION TO CONTROLLED TEMPERATURE.

摘要

The invention relates to a reliable and safe SCR system for reducing NOx emissions from a poor internal gas combustion engine by using urea in aqueous solution. Overheating and hydrolysis of the solution is avoided by keeping the temperature of the urea solution sufficiently low so as not to allow it to be maintained for a sufficient time at high temperature and the urea hydrolyzed to such a degree that solids precipitate. In a preferred embodiment, an injection system similar to that used in fuel injection provides constant feeding to the injectors (32) and a return line (33). Feeding and injection can be controlled to provide sufficient urea for NOx reduction and sufficient cooling capacity so that the feeding and injection systems prevent hydrolysis and deposition of hydrolysis products.