Method for dosing solid urea (CO(NH2)2) and device for applying such a method

• Main Authors: REICHERT, MARTINA, BARTSCH, LEONHARD
• Format: Patent
• Language: English; French; German
• Published: 14.11.2007
• Subjects: BLASTING; CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TOTRANSPORTATION; ENGINE PLANTS IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNALCOMBUSTION ENGINES; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES ORENGINES IN GENERAL; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; HEATING; LIGHTING; MACHINES OR ENGINES IN GENERAL; MECHANICAL ENGINEERING; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; STEAM ENGINES; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINSTCLIMATE CHANGE; TRANSPORTING; WEAPONS

The metering solid urea (CO(NH 2) 2) for use as reducing agents for selective catalytic reaction (SCR) catalyst, comprises supplying the urea (3', 3") to a reactor by a metering unit, splitting up of the supplied urea in interaction with a heatable reactor element (1) of the reactor by thermolytic reacting under energy input into ammonia (NH 3) and isocyanic acid (HNCO), indirectly determining the energy input spent for the thermolytic reaction, and determining the supplied, split quantity of urea by the use of already determined energy input. The metering solid urea (CO(NH 2) 2) for use as reducing agents for selective catalytic reaction (SCR) catalyst, comprises supplying the urea (3', 3") to a reactor by a metering unit, splitting up of the supplied urea in interaction with a heatable reactor element (1) of the reactor by thermolytic reacting under energy input into ammonia (NH 3) and isocyanic acid (HNCO), indirectly determining the energy input spent for the thermolytic reaction, and determining the supplied, split quantity of urea by the use of already determined energy input. The temperature of reactor element is detected and the temperature drop of the reactor element is determined due to the thermolytic reaction of the urea. The spent energy input using this temperature drop is indirectly determined. The electrical resistance of reactor element is monitored, and the change of the resistance of the reactor element due to the temperature drop is determined. The spent energy input using this change of resistance is indirectly determined. The change of resistance is determined in such a way that the reactor element is attached to a constant voltage supply and the change of a current that flows through the reactor element is determined due to the change of resistance. For heating up of the reactor element, a heating device is intended, and a target temperature is given to this heating device for the split up of the supplied urea. The power requirement of the heating device necessary for the maintenance of the target temperature is determined, and the spent energy input using the power requirement is indirectly determined. The determined urea quantity is made available as an input signal. An independent claim is included for a device for metering solid urea for use as reducing agents for selective catalytic reaction catalyst. Die Erfindung betrifft ein Verfahren zur Dosierung von festem Harnstoff (CO(NH 2 ) 2 ), insbesondere zur Verwendung als Reduktionsmittel für einen SCR-Katalysator, bei dem –  der Harnstoff (3',3") in fester Form mittels einer Dosiereinheit einem Reaktor zugeführt wird, und –  der zugeführte Harnstoff (3',3'') in Wechselwirkung mit einem beheizbaren Reaktorelement (1) des Reaktors im Rahmen einer thermlolytischen Reaktion unter Energieeintrag in Ammoniak (NH 3 ) und Isocyansäure (HNCO) aufgespalten wird. Des weiteren betrifft die Erfindung eine Vorrichtung zur Durchführung eines derartigen Verfahrens. Es soll ein Verfahren der oben genannten Art aufgezeigt werden, das eine Dosierung des Harnstoffs mit einer größeren Genauigkeit ermöglicht.