NOVELTY - The system has a reactor (6) in which chemical reaction that converts nitrogen oxides included in exhaust gas into nitrogen by denitrifying the nitrogen oxides using catalyst takes place. The reactor comprises a catalytic filter unit (62) coated with catalyst and provided with a set of through-holes through which exhaust gas passes and a noise-reducing unit (63) for removing noise from the exhaust gas denitrified by the filter unit. The reactor denitrifies the nitrogen oxides and reduces the noise. The filter unit includes wave-shaped side walls forming the through-holes.    USE - Exhaust gas denitrifying system for use in engines of thermoelectric power plants and ships.    ADVANTAGE - The system can denitrify the exhaust gas and reduce noise using the reactor without providing a silencer. The filter unit in the reactor can reduce the noise such that size of a noise-reducing unit can be decreased, so that size of the reactor can be decreased compared to size of the silencer of the system, thus decreasing size of the system. The side walls forming the through-holes of the filter unit are formed in wave shape, so that space of the through-holes can be enlarged, while maintaining a contact area between the exhaust gas and the catalyst, thus increasing noise-reducing effect, while minimizing pressure drop of the exhaust gas. The system includes partitions that are placed at a rear side of the filter unit in the reactor at regular intervals along direction parallel to flow of the exhaust gas, so that the flow of the exhaust gas denitrified by the filter unit can be dispersed and the noise of the exhaust gas can be reduced, thus increasing noise-reducing effect. The system allows denitrification reaction of the exhaust gas to be conducted prior to reduction of noise, so that high-temperature and high-pressure exhaust gas is denitrified, thus improving denitrification efficiency of the exhaust gas. The system minimizes pressure drop of the exhaust gas, thus increasing efficiency of an engine and decreasing consumption of fuel. The system allows length of a mixing chamber to be kept long to secure time and length sufficient for mixing reductant with the exhaust gas after spraying the reductant in short period of time, so that the length of the mixing chamber can be shortened, thus efficiently maintaining area of the system.    DESCRIPTION OF DRAWING(S) - The drawing shows a partially-cut away perspective view of a reactor used by an exhaust gas denitrifying system with a noise-reduction structure.    Reactor (6)    Noise-absorbing material layer (61)    Catalytic filter unit (62)    Noise-reducing unit (63)    Partitions (631)