JP6007468B2 - Denitration equipment - Google Patents

Description

  The present invention relates to a denitration device that reduces nitrogen oxides contained in engine exhaust gas to nitrogen using a reducing agent.

  Combustion exhaust gas (exhaust gas) is generated when fossil fuel is burned in an engine such as a ship or a vehicle. This exhaust gas contains nitrogen oxides (hereinafter simply referred to as NOx). In order to remove such NOx, a denitration device may be provided on the downstream side of the exhaust passage.

As a denitration apparatus, a selective catalytic reduction denitration apparatus that includes a denitration catalyst that promotes NOx reduction and a reducing agent that reduces NOx has become widespread. When NOx is decomposed using a denitration device, exhaust gas and a reducing agent are mixed, and the mixed gas is passed through a denitration catalyst so that the reducing agent reduces (decomposes) NOx in the exhaust gas. To do. Ammonia (NH ₃ ) is considered as the reducing agent, but urea is widely used as a precursor of ammonia because ammonia is highly toxic. Therefore, in order to supply ammonia to the denitration catalyst, the urea water inlet is installed upstream of the denitration catalyst.

  As a technology to generate ammonia by sufficiently vaporizing and decomposing urea water in the denitration device, a part of the exhaust gas flowing through the exhaust flue leading the engine exhaust gas is shunted downstream of the DPF (Diesel Particulate Filter). In order to vaporize and decompose the urea water injected from the injection valve in the flow path of the split flow exhaust gas, a technique has been proposed in which a heater is disposed in the flow path of the split flow exhaust gas (for example, Patent Document 1).

Japanese Patent No. 4430524

  By the way, a large ship such as a container ship or a tanker has a large diameter of a pipe for circulating exhaust gas, for example, 1 to 2 m. When a reducing agent is introduced into a pipe having such a large diameter, even if the technique of Patent Document 1 is used, urea water cannot be evenly distributed in the pipe. Will be biased.

  In this case, where the concentration of ammonia is high, NOx contained in the exhaust gas can be reliably reduced, but ammonia may be surplus and ammonia may be discharged. On the other hand, where the ammonia concentration is low, ammonia is insufficient to reduce NOx contained in the exhaust gas, and NOx may be exhausted without being sufficiently reduced.

  In view of such problems, an object of the present invention is to provide a denitration apparatus capable of uniformly distributing a reducing agent in a pipe with a simple configuration.

In order to solve the above-described problems, a denitration apparatus according to the present invention is provided in an exhaust path of an engine and serves as a denitration catalyst that promotes reduction of exhaust gas sent from the engine by a reducing agent, and an exhaust path upstream of the denitration catalyst. Reducing agent introduction having a plurality of flow paths formed by a plurality of pipes having a circular cross section in the radial direction and a main pipe through which the reducing agent flows , and introducing a reducing agent from the main pipe to each of the flow paths comprising a part, a plurality of the flow path is arranged so as to surround the main pipe, characterized in Rukoto.

  The reducing agent introduction unit may introduce the reducing agent so that the concentration is uniform in each flow path.

  The present invention enables a reducing agent to be uniformly distributed in a pipe with a simple configuration.

It is explanatory drawing for demonstrating a denitration system. It is explanatory drawing for demonstrating an example of a some flow path. It is explanatory drawing for demonstrating the other example of a some flow path.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  In large ships such as container ships and tankers, a uniflow type two-cycle engine (two-stroke engine), which is advantageous in terms of cost because it has high thermal efficiency and low-quality fuel oil (heavy oil) can be used, is widely used. Combustion of fuels such as fossil fuels such as gasoline, light oil, heavy oil, liquefied natural gas (LNG), and liquefied petroleum gas (LPG) in such engines results. The exhaust gas contains NOx. Hereinafter, the denitration system 100 that reduces NOx in the exhaust gas discharged from the engine will be described. In the following embodiments, a uniflow type two-stroke engine will be described as an example of an engine used in the denitration system 100. However, the denitration system 100 may be adopted in other types of two-stroke engines.

(Denitration system 100)
FIG. 1 is an explanatory diagram for explaining a denitration system 100 according to the present embodiment. As shown in FIG. 1, the denitration system 100 includes an engine 110, a supercharger 120, and a denitration device 200. In FIG. 1, the flow of substances (exhaust gas, reducing agent) is indicated by solid lines, and the flow of signals is indicated by broken lines.

  The engine 110 includes a cylinder 110a, a piston 110b, an exhaust valve 110c, and an exhaust collecting pipe 112. The engine 110 reciprocates in the direction shown by the white arrow in FIG. 1 so that the piston 110b connected to the crosshead (not shown) can slide in the cylinder 110a through the processes of scavenging, compression, combustion, and exhaust. To do. In such a crosshead type piston 110b, the stroke in the cylinder 110a can be formed relatively long, and the crosshead receives the side pressure acting on the piston 110b, so that the output of the two-stroke engine can be increased. Can do. Further, since the cylinder 110a and the crank chamber in which the crosshead is accommodated are isolated, it is possible to prevent fouling deterioration even when low quality fuel oil is used. The exhaust collecting pipe 112 collects a plurality of exhaust passages communicating with the cylinder 110 a through the plurality of exhaust valves 110 c provided in the engine 110.

  The supercharger 120 includes a turbine 122 and a compressor 124 that is coaxial with the turbine 122. The turbine 122 is rotated by the exhaust gas X1 discharged from the exhaust collecting pipe 112, and the compressor 124 uses the rotation of the turbine 122 to activate an active gas (oxidant such as oxygen or ozone, or The air-fuel mixture (for example, air)) is compressed to increase the scavenging pressure to the engine 110. By doing so, the output of the engine 110 can be improved.

  The denitration apparatus 200 reduces the NOx contained in the exhaust gas X1 to nitrogen by causing ammonia to act on the exhaust gas X1.

  As described above, the exhaust gas X1 exhausted from the engine 110 passes through the exhaust collecting pipe 112, the exhaust path 202a, the turbine 122, and the exhaust path 202b, and is then introduced into the denitration apparatus 200, where NOx is reduced and the exhaust gas is exhausted. X2 is discharged to the outside. Hereinafter, a specific configuration of the denitration apparatus 200 according to the present embodiment will be described.

(Denitration device 200)
In the denitration apparatus 200 according to the present embodiment, a selection is made such that a reducing agent is introduced into the exhaust gas X1, and NOx contained in the exhaust gas X1 is reduced by a denitration catalyst downstream of the introduction position of the reducing agent to generate nitrogen. The catalytic reduction method is adopted.

  Specifically, as shown in FIG. 1, the denitration apparatus 200 includes a plurality of flow paths 210, a reducing agent introduction unit 212, a denitration catalyst 214, a NOx detection unit 216, and a reducing agent adjustment unit 218. Composed. Here, a case where there are four flow paths 210 will be described as an example.

  The plurality of flow paths 210 are provided as at least a part of the exhaust path 202 b upstream of the denitration catalyst 214.

  FIG. 2 is an explanatory diagram for explaining an example of the plurality of flow paths 210, and is a view for explaining a cross section in the radial direction of the tube 204 that forms the flow paths 210. As shown in FIGS. 2A and 2B, the plurality of flow paths 210 (indicated by 210 a to 210 d in FIG. 2) include, for example, a pipe 204 that constitutes the exhaust path 202 b of the engine 110. It is formed by dividing by a partition plate 220 extending in the longitudinal direction.

  FIG. 3 is an explanatory view for explaining another example of the plurality of flow paths 210 and is a view for explaining a cross section in the radial direction of the tube 204 forming the flow paths 210. As shown in FIGS. 3A and 3B, the plurality of flow paths 210 (210 e to 210 h in FIG. 3) are formed by independent pipes 206.

  The reducing agent introduction unit 212 introduces (injects) urea water so that the concentration is uniform in each of the plurality of flow paths 210.

  As shown in FIGS. 2 and 3, the pipe 204 and the pipe 206 forming the flow path 210 are configured so that the outer periphery is covered with a heat insulating material. Thereby, the situation where the exhaust gas X1 passing through the flow path 210 radiates heat to the outside can be avoided, and the urea water can be suitably vaporized and decomposed.

  The denitration catalyst 214 is made of a metal such as vanadium, tungsten, molybdenum, or an oxide thereof and titanium oxide, and reduces NOx in the exhaust gas X1 that has passed through the turbine 122 of the supercharger 120.

  The NOx detector 216 detects the NOx concentration of the exhaust gas X1 upstream of the turbine 122 or the exhaust gas X1 downstream. Here, since the NOx concentration has a correlation with the engine load, the NOx detecting unit 216 may estimate the NOx concentration from the engine load without measuring the actual NOx concentration.

  The reducing agent adjustment unit 218 adjusts the amount of urea water introduced by the reducing agent introduction unit 212 based on the NOx concentration detected by the NOx detection unit 216.

  Due to the configuration provided with the NOx detection unit 216 and the reducing agent adjustment unit 218, urea water is introduced wastefully when the NOx in the exhaust gas X1 is small, and ammonia is not oxidized in the denitration catalyst 214 and discharged outside. It is possible to avoid a situation where the amount of urea water is necessary to reduce the NOx when the amount of NOx is large.

  As described above, the denitration apparatus 200 according to the present embodiment has a plurality of flow paths 210 and a configuration in which urea water is introduced into each of the flow paths 210, so that the inside of the pipes 204 and 206 constituting the exhaust path 202 b The urea water can be distributed evenly. Therefore, it is possible to make the ammonia concentration uniform in the radial cross section of the tubes 204 and 206.

  As a result, it is possible to avoid a situation in which ammonia is exhausted due to an excess of ammonia caused by uneven concentration of ammonia, and a situation in which NOx cannot be sufficiently reduced and exhausted due to insufficient ammonia. Is possible.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  INDUSTRIAL APPLICABILITY The present invention can be used for a denitration device that reduces nitrogen oxides contained in engine exhaust gas to nitrogen using a reducing agent.

200 ... Denitration device 202b ... Exhaust passages 204 and 206 ... Pipe 210 ... Channel 212 ... Reductant introduction part 214 ... Denitration catalyst 220 ... Partition plate

Claims (2)

A denitration catalyst that is provided in the exhaust path of the engine and promotes reduction of exhaust gas sent from the engine by a reducing agent ;
A plurality of flow paths formed as a plurality of pipes provided as exhaust passages upstream of the denitration catalyst and having a circular cross section in the radial direction;
It has a main pipe in which the reducing agent flows, and the reducing agent introducing part for introducing the reducing agent in each of the flow path from the main pipe,
With
Wherein the plurality of flow path denitration apparatus according to claim Rukoto disposed so as to surround the main pipe.   The denitration apparatus according to claim 1, wherein the reducing agent introduction unit introduces the reducing agent so that the concentration is equalized in each of the flow paths.

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