KR100398099B1 - Urea-SCR SYSTEM CONTROLED WITH TEMPERATURE AND RPM - Google Patents

Abstract

The present invention extends the active region of the catalyst by connecting the Pt / Al ₂ O ₃ catalyst and V ₂ O ₅ / TiO ₂ catalyst in series, and by adjusting the urea (Urea) injection amount by using the temperature and rpm data as an input signal, The present invention relates to a temperature rpm controlled Urea-SCR system that can adjust the ratio of urea and NOx to a catalyst and is installed in the exhaust pipe to purify harmful substances in the exhaust gas discharged from the exhaust manifold of the engine through the exhaust pipe. The injector to inject the urea by the air introduced through the air supply port, the urea supply pump to supply the urea in the urea tank to the injector, the thermocouple to measure the temperature in the catalyst, the input signal from the thermocouple and the engine side The DAS receives the input signal from the DAS, and the CPU outputs the element injection control signal to the injector via the DAS and amplification circuit based on the signal provided from the DAS. In the Urea-SCR system comprising a Pt / Al ₂ O ₃ catalyst and a V ₂ O ₅ / TiO ₂ catalyst in series connected in the catalyst group, the CPU is the temperature data input from the thermocouple and It is an object of the present invention to provide a temperature rpm controlled Urea-SCR system characterized by outputting an element injection control signal to an injector based on rpm data input from an engine speed sensor.

Description

Temperature-controlled thermo-scr system {Urea-SCR SYSTEM CONTROLED WITH TEMPERATURE AND RPM}

The present invention relates to a temperature rpm controlled Urea-SCR system, and more particularly, a Pt / Al ₂ O ₃ catalyst and a V ₂ O ₅ / TiO ₂ catalyst in series to extend the active area of the catalyst, The present invention relates to a temperature rpm controlled Urea-SCR system capable of constantly adjusting the ratio of urea and NOx by adjusting the urea injection amount using the rpm data as an input signal.

Although automobiles are classified into passenger cars, buses, and trucks according to their type, the same type of fuel is used for gasoline vehicles using gasoline as a fuel, diesel vehicles using diesel as a fuel, and LPG (Liquefied Petroleum Gas) as fuel. Also known as LPG vehicles.

Since the diesel vehicle is burned in an oxygen-rich atmosphere, the generation of NOx, which is a harmful substance, is considerably higher than that of a gasoline engine, and it is difficult to remove NOx because it is burned in a lean burn atmosphere. Therefore, the most actively developed as NOx removal technology is Urea (Urea) -SCR (Selective Catalytic Reduction) system. The Urea-SCR system supplies urea to an exhaust gas line in the form of an aqueous solution to react NOx with NH ₂ -CO-NH ₂ (urea) to convert NOx to N ₂ + It is a method of converting into O ₂ .

In the conventional Urea-SCR system having such a configuration, the active area (temperature) of the Urea-SCR catalyst is so narrow that NOx can be removed during urea supply only within a certain temperature range, and the NOx value can be read in real time. Since the NOx sensor is not provided, data such as speed, rpm, load, temperature, and the like must be mapped and stored as data for each engine.

Accordingly, the present invention has been made to solve such a problem, and focuses on the fact that the NOx concentration and the catalyst temperature show similar patterns through the exhaust gas emission detection test of the diesel vehicle, thereby providing the catalyst temperature instead of the NOx concentration. In addition, by adjusting the urea injection amount through a predetermined equation using the temperature data and the rpm data of the engine as an input signal, the temperature rpm controlled type Urea which can suppress the generation of NOx by controlling the ratio of urea and NOx constantly. To provide an SCR system.

1 is a block diagram showing a Urea-SCR system according to the present invention,

Figure 2 is a graph showing the NOx purification rate in the Urea-SCR system according to the present invention, Figure 3 is a graph showing the change in catalyst temperature and NOx concentration over time in the flow path mode.

[Explanation of symbols on the main parts of the drawings]

2: engine 4; exhaust manifold

10: Catalyst 12,14: Pt / Al ₂ O ₃ catalyst, V ₂ O ₅ / TiO ₂ catalyst

16: Thermocouple 20: Injector

22: CPU 24: DAS

26: amplifier circuit 30: element tank

32: Urea supply pump 34: Air supply port

Temperature rpm controlled type Urea-SCR system of the present invention for achieving the above object is a catalytic device for purifying the harmful substances in the exhaust gas discharged through the exhaust pipe from the exhaust manifold of the engine, the air supply is installed in the exhaust pipe An injector for injecting urea by air flowing through the port, an urea supply pump for supplying urea in the urea tank to the injector, a thermocouple for measuring the temperature in the catalyst and an amplification based on an input signal from the thermocouple In the Urea-SCR system including a CPU for outputting the urea injection control signal to the injector via a circuit, in the catalyst is a state in which the Pt / Al ₂ O ₃ catalyst and V ₂ O ₅ / TiO ₂ catalyst is connected in series The CPU is arranged on the injector based on temperature data input from the thermocouple and rpm data input from the engine speed sensor. It characterized in that it outputs the injection control signal.

Hereinafter, a temperature rpm controlled Urea-SCR system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a Urea-SCR system according to the present invention, Figure 2 is a graph showing the NOx purification rate in the Urea-SCR system according to the present invention.

First, as shown in FIG. 1, the overall configuration of the Urea-SCR system is used to purify harmful substances in the exhaust gas discharged from the exhaust manifold 4 of the engine 2 through the exhaust pipe 6. The injector 20, which is installed in the catalyst 10, the exhaust pipe 6, and injects urea by air introduced through the air supply port 34, and the urea in the urea tank 30 is injected into the injector 20. A DAS receiving the urea supply pump 32 to be supplied to the reactor, the thermocouple 16 for measuring the temperature in the catalyst 10, and the input signal from the thermocouple 16 and the input signal from the engine 2 side ( 24 and a CPU 22 for outputting an element injection control signal to the injector 20 via the DAS 24 and the amplifying circuit 26 based on the signal provided from the DAS 24.

Here, the temperature data provided from the thermocouple 16 side of the catalyst 10 and the rpm data provided from the engine 2 side are input to a DAS (Data Acquisition System), and the DAS 24 inputs the input temperature data. After calculating the NOx amount in the total exhaust gas amount based on Equation 2 (NOx amount per second discharged from the engine) described below with rpm data, the calculated value is transmitted to the CPU 22. The CPU 22 Outputs the element injection control signal to the injector 20 through the DAS 24 and the amplifying circuit 26 based on the input value. That is, the amplified signal is passed through the amplifying circuit 26. 20 to provide a duty control, and the injector 20 injects the urea introduced from the urea tank 30 into the exhaust pipe 6 through the urea supply pump 32. reacting with and thereby convert it to N ₂ and O _2, while passing through the catalytic reactor 10 the purified exhaust Seuneun is discharged into the atmosphere through the then-end supply pipe to the muffler via the intermediate exhaust pipe 18.

In order to determine the injection amount of urea in the temperature rpm controlled Urea-SCR system of the present invention as described above, the amount of NOx (NOx concentration) in the total amount of exhaust gas discharged must be obtained, and in order to control the amount of urea injection in real time, the engine discharges per second. The amount of NOx (L / sec) should be obtained. When the amount of NOx emitted per second from the engine is obtained, the amount of urea injection can be determined by considering the reaction relationship between urea and NOx.

For example, the engine displacement per minute (L / min) discharged from the engine is generally the engine displacement x rpm / 2. To know the amount of NOx in the total displacement, the total volume (exhaust) is multiplied by the amount of NOx. The amount of NOx emitted per minute from the engine can be obtained by using Equation 1 below. NOx content per minute (L / min) = NOx concentration (ppm) × engine exhaust volume (L / min) × rpm / (2 × 1,000,000) Here, the 1,000,000 value is calculated in terms of parts per million since the unit of ppm is used. In order to control the amount of urea injection in real time, NOx amount per second is required rather than NOx amount per minute. Obtained from 2. NOx per second (L / sec) = NOx concentration (ppm) × engine exhaust (L / min) × rpm / (2 × 60 × 1,000,000) On the other hand, it can be seen that the above NOx concentrations showed almost similar patterns of catalyst temperatures in the exhaust gas amount detection test for the Euro mode, that is, the diesel driving mode and the high speed driving mode. Therefore, the NOx concentration value can be replaced by the catalyst temperature value. For example, FIG. 3 is a graph showing the change in catalyst temperature and NOx concentration over time, with a solid line indicating NOx concentration and a dotted line indicating temperature. As can be seen in Figure 3, since the pattern of the graphs showing the catalyst temperature and the NOx concentration are almost similar, instead of the practically difficult NOx concentration value (currently measuring the NOx concentration continuously in a vehicle is technically problematic). By applying the catalyst temperature value based on the above graph, it is possible to estimate the approximate amount of NOx per second. Roughly it is determined that the amount of NOx discharged per second, taking into account the relationship between the reaction element and the NOx can ultimately determine the dosage element. That is, the reaction of NOx with urea are shown below .H ₂ N-CO-NH ₂ + H ₂ O → 2NH ₃ + CO ₂ (t> 160 ° C.) 4NO + 4NH ₃ + 3O ₂ → 4N ₂ + 6H ₂ O6NO + 4NH ₃ → 5N ₂ + 6H ₂ O As can be seen from the above scheme, Urea is converted into two ammonia, and each ammonia reacts 1: 1 with NOx, so eventually urea and NOx reacts with 1: 2, thus determining the amount of urea injected. Thus, the amount of NOx per second (L / sec) ) Can be calculated using Equation 2, and considering the urea and the amount of NOx per second (L / sec) in the chemical reaction, it is possible to calculate the amount of urea participating in the reaction appropriately, Aqueous solution of urea can be injected on the basis.

Therefore, if the temperature value is obtained from the thermocouple 16 installed in the catalyst 10 instead of the NOx concentration, and the rpm value of the engine is obtained from the engine speed sensor, the amount of NOx at that time can be predicted. Can be injected.

The injected urea aqueous solution reacts with the NOx while passing through the Pt / Al ₂ O ₃ catalyst 14 and the V ₂ O ₅ / TiO ₂ catalyst 12 in the catalyst 10 so that NOx is converted into N ₂ and O ₂ . Decompose

The NOx conversion rate thus evaluated is shown in the graph of FIG. 2. This graph was obtained by fixing the engine rpm to 1500 and increasing the catalyst temperature. In this graph, activity was shown in a wide range from 150 to 400 ° C., and a high activity was shown by a good balance between urea and NOx.

That is, it was possible to configure the Urea-SCR system for reducing NOx only by rpm and catalyst temperature, and showed excellent performance.

According to the present invention described above, by extending the catalytic active region by connecting the Pt / Al ₂ O ₃ catalyst and V ₂ O ₅ / TiO ₂ catalyst in series, by adjusting the urea injection amount by using the temperature and rpm data as an input signal For example, by controlling the ratio of urea and NOx, the generation of NOx can be suppressed as much as possible, and the reduction of harmful gases has the effect of reducing environmental pollution.

Claims (1)

The catalyst 10 for purifying the harmful substances in the exhaust gas discharged from the exhaust manifold 4 of the engine through the exhaust pipe 6, and the exhaust pipe 6 is provided to the air supply port 34 Measuring the temperature in the injector 20, the urea supply pump 32 for supplying the urea in the urea tank 30 to the injector 20 by the air introduced through the air, and the catalyst 10 Urea-SCR system including a thermocouple 16 and a CPU 22 for outputting an element injection control signal to the injector 20 via an amplification circuit 26 based on an input signal from the thermocouple 16. To In the catalyst 10, a Pt / Al ₂ O ₃ catalyst 14 and a V ₂ O ₅ / TiO ₂ catalyst 12 are arranged in series, and the CPU 22 is a thermocouple 16. The temperature data inputted from the engine and rpm data inputted from the engine speed sensor are expressed by Equation 2 [NOx amount per second (L / sec) = NOx concentration (ppm) × engine exhaust capacity (L / min) × rpm / (2 × 60 × 1,000,000)] to obtain the amount of NOx discharged from the engine per second and at the same time to obtain the urea injection amount in consideration of the chemical reaction between urea and NOx, and based on this outputs the urea injection control signal to the injector 20 Temperature rpm controlled Urea-SCR system.