DOSING SYSTEM FOR INJECTION OF A UREA SOLUTION IN THE EXHAUST GAS CURRENT OF A COMBUSTION ENGINE AND PROCESS FOR CONTROLING THE INJECTION OF A Urea SOLUTION

摘要

Dosage system for the injection of a urea solution into the exhaust gas stream of a combustion engine and method for controlling the injection of a urea solution The present invention relates to a dosage system for the injection of a urea solution. urea solution in the exhaust gas stream (9) of a combustion engine for selective catalytic reduction, as well as a process for controlling the injection of a urea solution by means of compressed air, wherein the metering system can be connected with a urea solution tank (1) from which urea solution may be withdrawn, and wherein the dosing system may be connected to a compressed air supply (6), wherein the dosing system It has at least one ejector (5) through which, by means of compressed air, the urea solution can be injected into the exhaust gas stream (9), in which the metering system has an air valve (7). ), by means of which the pressure and / or the amount of air and / or the opening times of the compressed air supply valve (6), and between the air valve (7) and the ejector (5) a sensor is arranged for the measurement pressure and / or the amount of air in the compressed air supply (6) such that the amount of compressed air supplied for urea spraying is controlled at each operating point as a function of operating exhaust gas and exhaust gas mass stream and be reduced to the minimum required air