KR20020055630A - Urea-SCR SYSTEM CONTROLED WITH TEMPERATURE AND RPM - Google Patents

Abstract

PURPOSE: A temperature-rpm control type urea-Selective Catalytic Reduction(SCR) system is provided to reduce NOx by controlling urea injection amount by an input signal with temperature, rpm and uniform NOx-NH3 ratio. CONSTITUTION: A catalytic converter(10) purifies a noxious substance in exhaust gas exhausted from an exhaust manifold(4) through an exhaust pipe(6). An injector(20) is installed on the exhaust pipe(6), and injects urea by air introduced through an air supply port(34). A urea supply pump(32) supplies the urea in a urea tank(30) to the injector(20). A thermocouple(16) measures the temperature of the catalytic converter(10). A CPU(22) outputs a control signal for urea injection to the injector(20) according to a signal from the thermocouple(16). In the catalytic converter(10), a Pt/Al2O3 catalyst(14) is connected to a V2O5/TiO2 catalyst(12) in series.

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 / Al2O3 catalyst and a V2O5 / TiO2 catalyst are connected in series to extend the catalytic active region, and the temperature and rpm data are input signals. The present invention relates to a temperature rpm controlled Urea-SCR system capable of constantly adjusting the ratio of NOx / NH3 by adjusting the injection amount.

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.

Among them, diesel vehicles are burned in an oxygen-exhaust atmosphere, so the generation of NOx, which is a harmful substance, is considerably higher than that of gasoline engines, and it is difficult to remove NOx since it is burned in a lean burn atmosphere. Therefore, the most active development of NOx removal technology is the 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 NH2-CO-NH2 (urea) to convert NOx to N2 + O2.

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.

The present invention for solving this problem is to expand the catalytic active region, and by adjusting the urea injection amount by using the temperature, rpm data as an input signal to constantly adjust the ratio of NOx / NH3 to suppress the generation of NOx The purpose is to provide a temperature rpm controlled Urea-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.

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

2: engine 4; exhaust manifold

10: Catalyst 12, 14: Pt / Al2O3 catalyst, V2O5 / TiO2 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 exhausted from the exhaust manifold of the engine through the exhaust pipe, the air supply is installed in the exhaust pipe On the basis of the injector for injecting the urea by the air flowing through the port, the urea supply pump for supplying the urea in the urea tank to the injector, the thermocouple for measuring the temperature in the catalyst, and the input signal from the thermocouple In the Urea-SCR system including a CPU for outputting the urea injection control signal to the injector via an amplification circuit, a PtAl 2 O 3 catalyst and a V 2 O 5 TiO 2 catalyst are arranged in series in the catalyst, and the CPU is separated from the thermocouple. Based on the temperature data inputted and the rpm data of the engine inputted from the engine speed sensor, Characterized in that the element injection control signal to the injector.

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 flowing through the air supply port 34, and the urea in the urea tank 30, is injected into the injector 20. To the injector 20 via the urea supply pump 32 to be supplied to the reactor, the thermocouple 16 for measuring the temperature in the catalyst 10, and the amplification circuit 26 based on an input signal from the thermocouple 16. A CPU 22 for outputting an element injection control signal is provided.

Here, the temperature value detected by the thermocouple 16 of the catalyst 10 is input to a data acquisition system (DAS), and the DAS 24 transmits the input temperature value to the CPU (control unit) 22. . The CPU 22 outputs the element injection control signal to the amplification circuit 26 via the DAS 24 based on the input temperature value. Through the amplification circuit 26, the amplified signal is supplied to the injector 20 to control the duty. The injector 20 exhausts the urea introduced from the urea tank 30 through the urea supply pump 32. To (6). The injected urea reacts with NOx and converts it into N2 and O2, and the purified exhaust gas passing through the catalyst 10 is supplied to the silencer through the intermediate exhaust pipe 18 and then to the atmosphere through the end pipe. Discharged to the air.

In the Urea-SCR system having such a configuration, as a method for expanding the catalytic active region, a preferred embodiment of the present invention exemplifies a method of predicting the NOx value by reading the temperature instead of the NOx concentration.

H2N-CO-NH2 + H2O → 2NH3 + CO2 (t> 160 ℃)

4NO + 4NH3 + O2 → 4N2 + 6H2O

Considering 6NO + 8NH3 → 7N2 + 9H2O,

Approximately 1: 1 is suitable for NOx / NH3, and considering the engine rpm, the total amount of NOx can be known.

That is, the amount of NOx per second (l / sec) can be obtained by the following equation (1).

rm NOx concentration (ppm) x rpm (times / min) x exhaust rate (L) over 6000poo x 2 x 60

Here, rpm and displacement are known values depending on the operating conditions and the specifications of the engine, and the NOx concentration can be replaced by temperature.

Therefore, the amount of NOx per second (ℓ / sec) is calculated by Equation 1 and considering the amount of urea and NOx per second (ℓ / sec) in the formula 1, it is possible to calculate the amount of urea participating in the reaction appropriately Based on this, an aqueous solution of urea can be supplied.

Therefore, instead of the NOx concentration, if the temperature value is obtained from the thermocouple 16 installed in the catalyst 10 and the rpm value of the engine from the engine speed sensor, the amount of NOx at that time can be estimated, and based on this, Inject urea based on the measured quantity.

The injected urea aqueous solution reacts with the NOx while passing through the Pt / Al2O3 catalyst 14 and the V2O5 / TiO2 catalyst 12 in the catalyst 10 to decompose NOx into N2 and O2.

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, the Pt / Al2O3 catalyst and the V2O5 / TiO2 catalyst are connected in series to expand the catalyst active region, and the ratio of NOx / NH3 is fixed by adjusting the urea injection amount by using the temperature and rpm data as input signals. It is possible to suppress the generation of NOx as much as possible, and to reduce the environmental pollution according to the reduction of harmful gases.

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 The injector 20 for injecting the urea by air introduced through the urea, the urea supply pump 32 for supplying the urea in the urea tank 30 to the injector 20, and the temperature in the catalyst 10 are measured. 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, the Pt / Al2O3 catalyst 14 and the V2O5 / TiO2 catalyst 12 are arranged in series, The CPU 22 outputs an element injection control signal to the injector 20 based on temperature data input from the thermocouple 16 and rpm data of the engine input from an engine speed sensor. rpm controlled Urea-SCR system.