TWI237089B - Method of cleaning NOx for catalysts in a exhaust pipe of the motorcycle - Google Patents

Abstract

A method of cleaning NOx for catalysts in an exhaust pipe of the motorcycle comprises a fore reduction catalyst is installed in the exhaust pipe near an engine, a re-sued air is conducted into the exhaust pipe at a rear end of the fore reduction catalyst, and a hind oxidation catalyst is installed in the exhaust pipe at a rear end of the re-used air guide position. Thereby, the waste gas with less oxygen containing in the exhausting end of the engine passes through the reduction catalyst with an air to fuel ratio smaller than or equal to 14.7 so as to increase the ability that the reduction catalyst to convert the NOx in the waste gas to a harmless N2 or O2. Then, O2 is guided into by the re-used air so that air to fuel ratio of the waste gas passing through the Oxidized catalyst is larger than 14.7. Thereby, the CO and HC in the waste gas can be converted into harmful CO2 and N2O so as to purify the waste gas exhausting from the motor engine.

Description

1237089 Amendment_Case No. 93103170 V. Description of the Invention (1) [Technical Field] The present invention relates to a method for upgrading a catalyst to purify nitrogen oxides in an exhaust pipe of a locomotive, and particularly relates to a reduction catalyst, an oxidation catalyst, and a designation. The configuration technology of the secondary air introduction position also includes the technical application of using this configuration to control the air-fuel ratio of the exhaust gas. [Prior art] The air-fuel ratio (A / F) of the exhaust gas referred to in the present invention refers to the mixing ratio of the air (A i r) contained in the exhaust gas and the fuel (F u e 1). The most ideal air-fuel ratio (A / F) in the general engine operating environment is controlled within a predetermined range around 14.7 (as shown by the slanted area in Figure 1), which indicates that the better the engine's operating efficiency, the less likely it is that combustion will be incomplete. Phenomenon, and the catalyst in the exhaust pipe of the engine is more likely to react with harmful substances in the exhaust gas (Oxidation) and reduction (Reduction) reactions. The locomotive in the field, except for the engine operating environment equipped with an engine control unit (£ 11, 116 (] 〇-ntrol Unit, ECU) and an oxygen sensor (02 Sensor), can more stably control the air-fuel ratio in the exhaust gas. In addition, there is no other more effective method. Also, it is known that locomotive engines with smaller displacements based on cost considerations are not equipped with oxygen sensors. These locomotive engines without oxygen sensors are relatively The exhaust air-fuel ratio approaching 1 4 · 7 cannot be accurately controlled, so that the engine operating efficiency is relatively low, and the phenomenon of incomplete combustion generating harmful exhaust gas is more serious. The reasons affecting the efficiency of locomotive engine purification exhaust gas include Media installation technology and secondary air introduction position, etc. The current practice in the workshop is to coat one or more of the precious metals such as platinum (Pt), palladium (Pd), and rhodium (Rh).

Page 5 1237089 ^. __Case No. 93103170 (^ January 6 amendment_ V. Description of the invention (2) The metal metal carrier is set in the exhaust pipe, and the locomotive engine exhaust before the catalyst carrier The secondary air is introduced into the pipeline. The secondary air can introduce the fresh air from the outside into the exhaust pipe by the intermittent negative pressure generated when the locomotive engine is running, so as to make up for a certain amount of oxygen in the exhaust gas (〇2), and The air-fuel ratio is greater than 14.7, which promotes the conversion efficiency of the above catalysts to oxidize carbon monoxide (C 0) and hydrocarbons (HC). However, since the oxygen (〇2) content has been increased in the exhaust gas, it is forced to pass through the catalyst carrier The air-fuel ratio of the exhaust gas cannot be less than or equal to 14.7. At the same time, high temperatures are generated during the oxidation reaction. As a result, the conversion efficiency of the catalyst to reduce nitrogen oxides (NOx) is even lower, so that the nitrogen oxides emitted into the atmosphere are oxidized. The content of NOx is only increasing, which is the main cause of acid rain and damage to the ozone layer, which has a great impact on the natural environment. [Content] The method for improving the catalyst for purifying nitrogen oxides aims to maintain the original oxygen Oxidation catalyst is used to purify harmful substances such as carbon monoxide (C0) and hydrocarbons (HC) in the exhaust gas, and then a reduction catalyst is used to purify nitrogen oxides. (NOx To achieve the above purpose, the technology of the present invention includes the following steps: 1. Utilize the characteristic of less oxygen content in the harmful exhaust gas exhausted from the exhaust end of the engine, and reduce at least one Type catalyst is installed in the front exhaust pipe of the engine, and the front exhaust gas with insufficient oxygen content [air-fuel ratio (A / F) S14.7] is introduced into the exhaust end of the engine to facilitate the reduction of nitrogen oxides (NOx) to Harmless nitrogen (N2) and oxygen (02);

Page 6 1237089 __Case No. 93103170 V. Description of the invention (3) Amendment 2 · Use the negative pressure of the engine or electric fruit as the power source to introduce the secondary air into the exhaust pipe behind the reduction catalyst and supply a fixed amount of Oxygen to make the air-fuel ratio (A / F) of the exhaust gas at the rear stage> 14.7; 3 · At least one oxidation catalyst is set in the exhaust pipe behind the above-mentioned secondary air introduction position and contacts the air-fuel ratio (A / F) > The rear exhaust gas of 14.7 is beneficial to oxidize carbon monoxide (CO) and hydrocarbons (HC) into harmless carbon dioxide (C02) and water (H20) 'and discharge them to the outside world. However, in order to further elaborate the present invention, the detailed description is given below in conjunction with the drawings: [Implementation method] Firstly, as shown in FIG. 2, it is a schematic diagram of a configuration for implementing the present invention on an exhaust pipe of a locomotive, including The following structural contents are provided: At least one front-stage reduction catalyst (Reduction catalyst) 2 is provided in an exhaust pipe 10 adjacent to the exhaust end 1 of the engine. This reduction type catalyst 2 is implemented by using a metal or ceramic carrier covered with a precious metal containing at least a bond gold (Rh) component, which is used to convert the exhaust catalyst 1 from the engine into the reduction type catalyst 2 The front exhaust 1 2. In addition, the precious metal component of the reduced catalyst 2 can also be implemented as a three-way catalyst consisting of thorium (Rh), starting (Pt), and (Pd). A secondary air introduction port 14 'is provided in the exhaust duct 11 behind the above-mentioned reduction plastic catalyst 2 for introducing secondary air. When more than one reduction type catalyst 2 is provided, the position of the secondary air introduction port 14 is located behind the last reduction type catalyst 2 and exhausted behind the secondary air introduction port 14 Set in pipeline 11

Page 7 1237089 Γ_Case No. 93103Π0 Month / Day Amendment_ V. Description of the invention (4) At least one oxidation catalyst (3) in the latter stage. This oxidizing catalyst 3 is implemented by coating a metal or ceramic carrier with a precious metal containing at least the initial (Pt) and Is (Pd) components, and used to convert the exhaust gas flowing through the rear stage of the reducing catalyst 2 1 3. In addition, the precious metal component of the oxidation catalyst 3 may be a three-way catalyst consisting of rhodium (Rh), platinum (Pt), and palladium (Pd). In the above structure of the present invention, the front exhaust gas 12 discharged from the exhaust end 1 of the engine into the exhaust pipe 10 contains a large amount of harmful substances such as carbon monoxide (C0), hydrocarbons (HC), nitrogen oxides (NOx), And because the residual oxygen (0 2) is not completely combusted in the engine, the air-fuel ratio in the front stage exhaust gas 12 is at (A / F) S14.7, which is also conducive to the The exhaust gas flows, and the following steps and methods for implementing the present invention are planned, including: (1) · Performing a reduction reaction; using a reduction catalyst 2 at the front stage to purify the front stage discharged from the exhaust end 1 of the engine into the exhaust pipe 10 The exhaust gas 12 reduces nitrogen oxides (NOx) in the exhaust gas 12 before the air-fuel ratio (A / F) '14 .7 to harmless nitrogen (N2) and oxygen (02). In the above steps, the front-stage exhaust gas 12 containing harmful substances such as carbon monoxide (co), hydrocarbons (HC) 'nitrogen oxides (NOx), etc., contains at least a rhodium gold (Rh) as a main component in the reduction catalyst 2 After the conversion of 'due to the air-fuel ratio (A / F) S 1 4 · 7, only carbon monoxide (C 0) and hydrocarbons (HC) and other harmful substances have not been completely purified, and due to nitrogen oxides (NOx) Oxygen (〇2) is generated when it is reduced. Although not many, it still contributes to the demand for the oxidation reaction of the exhaust gas 13 in the subsequent stage.

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(2) Introduce the air once; from the exhaust pipe j j behind the external prototype catalyst 2, oxygen (02) is introduced into the exhaust gas 13 in the rear stage to the ratio (A / F) > 14.7. In the above steps, the secondary air can be controlled by using the negative pressure of the engine as the power source and the valve, and the valve body is installed in the engine or the negative pressure suction force is actuated, and then the exhaust gas behind the reduction catalyst 2 is introduced. The amount of air introduced with the speed of the engine can make the amount of secondary air introduced and the air-fuel ratio of the exhaust gas at the rear of the exhaust pipe 1 behind the high-reduction catalyst 2 (A / F) > 1 4 the method of secondary air It is also possible to use an exhaust pipe 11 inside. The secondary air 15 is introduced in the above-mentioned range so that the method of increasing the air-fuel introduction of the exhaust gas in the rear stage 13 with the engine speed is quantitatively implemented. The implementation includes the use of a secondary air to control the negative pressure of 1 § The pressure end 'receives intermittent fresh air outside (ie, secondary air ^ in the pipe 11. This method is easy to increase and decrease the second rate of the south, in other words, put in a proportional relationship' will help raise the content of exhaust gas in the channel 10. The amount of oxygen is even • 7 (as shown in Figure 3). In addition, the electric fruit is introduced to force which gas enters the rear (3). The oxidation reaction is carried out; the oxidation catalyst 3 at the rear stage is used to purify the exhaust gas 13 from the above stage to make the air The fuel ratio is (A / F) > The residual monoxide reverse (C0) and hydrocarbons (jjc) in the waste 13 after the stage 14 · 7 are quickly converted into harmless carbon dioxide (C02) and water (H20). In the above steps, the oxidation catalyst 3 in the latter stage contains at least the noble metals (P t) and (P d), which are the main components, and can be used in the exhaust gas in the latter stage. 3 Air-fuel ratio (A / F) > 1 4 · In the case of 7, the existing ideal conversion rate is exerted. The steps of (1) to (3) above will be It can effectively improve the conversion rate of the reduction catalyst 2 in the previous stage when purifying nitrogen oxides (N 0 X).

Page 1237089 y: _Case No. 93103170 (Fi month β amendment_) V. Description of the invention (6) Maintained the oxidation catalyst in the latter stage 3 Conversion rate when purifying carbon monoxide (C 0) and hydrocarbons (HC) (As shown in Figure 3), therefore, it is indeed sufficient to improve the exhaust gas exhaust quality of the locomotive engine. Furthermore, the above-exemplified embodiment of FIG. 2 of the present invention, in which the exhaust gas connected to the exhaust end 1 of the engine is used for exhaust gas exhaustion. The gas ducts 10 and 11 are also included in the muffler chamber 4 that guides exhaust emission; in other words, as long as the above-mentioned reduction catalyst 2 at the previous stage, the position where the secondary air 15 is introduced, and the oxidation catalyst 3 at the rear stage, according to Sequentially arranged on the exhaust pipe 10, 11 or the baffle 41 of the anechoic chamber 4 (as shown in Figure 2), which is within the exhaust flow channel, and those who perform the above reduction and oxidation reactions are all It belongs to the application considered by the present invention, and it will be presented. Based on the description of the above embodiments, it is believed that the technical content of the present invention and the high usability that can be implemented are disclosed in detail, but the technology of the present invention is not limited to Therefore, based on the above and after Patents make brief contents scope of equivalents should be modified under the application scope of the present invention, and to Chen.

Page 10 1237089 Amendment_Case No. 93103170 Simple illustration of the diagram [Simplified illustration of the diagram] Figure 1: Reveal a line chart between the ideal conversion rate and air-fuel ratio, showing that NOx can be obtained when the air-fuel ratio is close to 14.7. And the optimal conversion rates of CO and HC. Figure 1 · Reveals the layout diagram of an exhaust pipe of the present invention. 1 Explains that there is a front stage exhaust gas reduction catalyst introduced into the secondary air. Operation Process 0 Figure III. Reveals a line graph between the conversion rate and air-to-air ratio of the present invention illustrating the air-fuel ratio of the front exhaust gas when converting NOx ^ 14 • 7 and the air-fuel ratio of the rear exhaust gas when converting C0 and HC > 1 4. Reduced contact media 2- 3- 4- Oxidized contact media separator muffling chamber 41

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Claims (1)

1237089 Case No. 93103170 Amendment VI. Application for Patent Scope 1. A method for upgrading catalysts to purify nitrogen oxides in the exhaust pipe of a locomotive. At least one front section of the exhaust pipe connected to the exhaust end of the engine is arranged. The reduction catalyst and at least one oxidation catalyst at the rear stage, and the secondary air is introduced into the exhaust pipe, so as to perform the following steps: (1) · reduction reaction: using at least rhodium gold (Rh) coating The reduction catalyst at the previous stage purifies the front stage exhaust gas discharged from the exhaust end of the engine into the exhaust duct, and reduces the nitrogen oxides (NO x) in the front stage exhaust gas of the air-fuel ratio (A / F) S 14. 7 to harmless Nitrogen (N2) and Oxygen (02); (2). Introduce secondary air: Introduce secondary air from the outside into the exhaust duct behind the reduction catalyst, and supply a sufficient amount of oxygen (02) into the rear exhaust gas. In order to increase the air-fuel ratio of the exhaust gas in the rear stage to (A / F) > 1 4. 7; Purify the exhaust gas from the above-mentioned rear stage and set the air-fuel ratio to (A / F) > 14.7 Residual carbon monoxide (C0) and hydrocarbons (HC) in the exhaust gas in the later stage are oxidized to harmless carbon dioxide (C02) and water (H20), and the above exhaust gas is discharged to the outside. 2. For example, the method for purifying nitrogen oxides in the first scope of the patent application, gas. 3. For the method of purifying nitrogen oxides in the scope of patent application No. 1 catalyst, air. 4. According to the method for purifying nitrogen oxides in the first catalyst range of the patent application, lifting in the exhaust pipe of the locomotive as described in the item is to introduce the secondary air with the negative pressure of the engine. The electric pump is forcibly introduced into the locomotive exhaust pipe as described in the second item, wherein the exhaust pipe contains the guided exhaust gas. Page 12 '1237089 Amendment; _ Case No. 93103170 Sixth, the scope of the patent application emissions anechoic chamber. inm