KR0173398B1 - Air fuel ratio control of combustion appliance by using the gas sensor and processing method of exhaust gas - Google Patents

Abstract

The present invention can easily detect the amount of oxygen (O ₂ ) of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NO _x ) in the gas discharged after the fuel and air are mixed and combusted in the combustion chamber of the combustion apparatus. The voltage signal obtained by installing a semi-conductor type gas sensor in the year is processed by the microcomputer and applied to control the air-fuel ratio of the combustion device, the exhaust gas recirculation function, and the operation temperature of the three-way catalyst. The sensor 3 detects the concentrations of carbon monoxide and hydrocarbons as voltages, respectively, and sends them to the microcomputer, and the oxygen, nitrogen oxide, and temperature sensors simultaneously measure the concentration of oxygen and the temperature of the combustion flue gas as voltages and send them to the microcom. And compare and settle the value. The amount of carbon monoxide and hydrocarbons due to the lack of air combustion is compared with the reference output voltage at the optimum combustion, and the opening and closing angles of the blower 8 or damper 7 of the boiler and the opening time of the injector until the value matches the reference voltage. Air-fuel ratio control method of combustion flue gas measurement-type combustor using multi-gas sensor to optimize air-fuel ratio by adjusting the gas pressure and the output voltage of carbon monoxide or hydrocarbon sensor is zero at the same time. The output voltage of the oxygen and nitrogen oxide sensor is largely negative and it is adjusted to the optimum combustion by controlling the blower, damper or injector until the same as the reference voltage, respectively. If the combustion temperature is higher than 300 ℃ or the oxygen concentration is 4 ~ 10%, it is open if it is over the setting value of Micom (6). The nitrogen recirculation valve 9 is closed to suppress the release of nitric oxide compounds. Also, if the carbon monoxide, hydrocarbon, and nitrogen oxide emissions from the sensors 3 and 5 are excessively discharged above the regulated values, the catalytic purifier 4 A method of treating flue gas of a combustor using a composite gas sensor to control the temperature of the gas as high as possible to discharge harmful gases low.

Description

Air-fuel ratio control and flue gas treatment method of combustion equipment using gas sensor

1 is a flue gas concentration change of the combustion device according to the air volume.

2 is a configuration of the air-fuel ratio of the combustion equipment (boiler), exhaust gas recirculation, catalytic purifier.

3 is a detailed view of the exhaust gas detection sensor.

4 is a sensor output voltage for each exhaust gas in the case of air shortage combustion.

5 is a change of the motor rotation, the damper opening and closing angle, the opening and closing angle of the recirculation air valve, the catalyst purifier temperature according to the output voltage.

* Explanation of symbols for main parts of the drawings

1: combustion chamber 2: year

3,5 sensor 4: catalytic purifier

6: micom 7: blower

8: damper 9: exhaust gas recirculation valve

10: recycle passage

The present invention relates to an air-fuel ratio control and exhaust gas treatment method of a combustion device using a gas sensor. Specifically, carbon monoxide (CO) and hydrocarbon (HC) in the gas discharged after being mixed with fuel and air in the combustion chamber of the combustion device. And controlling the air-fuel ratio and the exhaust gas recirculation function of the combustion device by installing a semiconductor gas sensor that can easily detect the oxygen (O ₂ ) amount of nitrogen oxide (NO _x ) in the flue by calculating the voltage signal with a microcomputer. This method is applied to the operation temperature control of the original catalyst.

The exhaust gas type air-fuel ratio control technology applied to various combustors such as boilers, automobiles, and incinerators is mainly controlled by using only zirconia-based or titania-based ceramic oxygen sensors to control the air and fuel costs by detecting oxygen concentration in the exhaust gas. did. This technology is not widely used due to its own problems with oxygen sensors and its derivatives. That is, the oxygen sensor has a slow response time of more than 30 seconds due to the diffusion of oxygen ions into the solid electrolyte, and the operating temperature of the measuring sensor is about 600 to 800 ° C., which requires a heating device. When CO, HC) components remain or low fuel consumption due to gas leakage, the oxygen concentration decreases due to combustion, or negative pressure is generated in the combustion chamber, and inflow of air from the outside is inevitable. So there was a big problem in use. In addition, it is difficult to control the air-fuel ratio by supplying excess surplus air to reduce the generation of pollution gas during combustion, or by introducing small amount of oxygen in the rear end of the boiler or the year due to air leakage. The sensor device is large and the price is expensive.

In addition, the exhaust gas recirculation function has a low effect of lowering the flame temperature because the exhaust gas is recycled at all times except for the initial operation of the combustion device. This method can in particular to lower the emissions of nitrogen oxides take place by a gentle combustion with a low oxygen concentration in the flame temperature drops with the combustion reaction zone of the high temperature section to the recycle is determined by the discharge amount of NO _x in the exhaust gas temperature.

Current three-way catalytic purifiers for exhaust gas purification have been linked to oxygen concentrations regardless of the constituents or concentrations of noxious exhaust gas, which keeps the temperature and life of the catalyst due to deterioration. In this method, the temperature of the catalytic converter is linked to about 300 ℃ to 600 ℃ according to the exhaust gas concentration obtained by the semiconductor gas sensor. In other words, when the harmful gases of carbon monoxide, hydrocarbons and nitrogen oxides are discharged at low concentration, the catalyst temperature is lowered, while in the case of high concentration discharge, the catalyst temperature is kept higher, thereby improving purification efficiency and catalyst life.

As a new method to solve the above problems, the present invention proposes an air-fuel ratio control and a combustion management technique using a combination of a semiconductor CO, HC, NO _x , O ₂ sensor and a temperature detection sensor.

When petroleum, gas and coal are burned, soot, carbon monoxide, and hydrocarbons are generated when air is insufficient depending on air and fuel costs. On the other hand, when the air is supplied excessively, the above unburned substances are reduced, but over-emission of nitrogen oxide and exhaust gas There are problems such as excessive heat loss and unsafe combustion conditions. Therefore, all the combustors have an optimum combustion zone, and around 20 ~ 80ppm of carbon monoxide and hydrocarbons (excess air ratio λ = 1.15 ± 0.09, air-fuel ratio A / F = 1.45 ± 0.09) and oxygen is about 3 ~ 4 In% (see Figure 1).

The present invention is a composite for detecting exhaust gas temperature, carbon monoxide and unburned hydrocarbons, oxygen and nitrogen oxides between the three-way catalytic purifier 4 and the rear end of the three-way catalytic purifier 4 of the combustion apparatus combustion chamber 1 and the flue 2. The semiconductor gas sensors 3 and 5 are provided respectively. Here, the over-generation of carbon monoxide and unburned hydrocarbons indicates the lack of air supply on the basis of optimal combustion, and the over-generation of oxygen and nitrogen oxides is judged as the over-supply of combustion air. In addition, the temperature value is used for output correction and combustion control of the combustion flue gas detection sensor.

The output size of each sensor detected by the composite sensor is input to the microcomputer 6 and compared and calculated according to the characteristics of the signal. In the case of a boiler, the angle of the damper 8 and the rotation speed of the blower 7 are controlled. 2) to control the recirculation of the exhaust gas, and 3) to feed back to adjust the operating temperature characteristics of the three-way catalytic purifier (4) by controlling the opening and closing rate of the exhaust gas recirculation valve (9) of the combustion device. use.

The air-fuel ratio adjustment is determined by the sensor 3 that the air supply is excessive, reduce the number of rotations of the burner motor of the blower 7 and / or widen the angle of the air passage diameter regulator (damper) 8 of the combustor, and also the amount of air. On the contrary, if it is determined that the air is insufficient, increase the motor rotation speed or narrow the angle of the damper to reduce the generation of carbon monoxide or unburned hydrocarbon with sufficient air supply.

The recirculation of the exhaust gas is determined by the microcomputer to exclude the case where the temperature of the exhaust gas detected by the sensor is too high than the set temperature (above 300 ° C) or the oxygen concentration is high (3.8% or more), and then the exhaust gas is returned to the recirculation passage 10. It is sent back to the combustion air to reduce the internal flame temperature and oxygen concentration, thus reducing the emission of excess nitric oxide with efficient combustion.

The control of the catalyst purifier (4) is to control the operating temperature to reduce the carbon monoxide, nitrogen oxide, and hydrocarbon components, which are regulated in the flue gas, to a catalyst heated to a temperature of 320 ° C or higher to be harmless. Maintaining a high temperature of the sieve at all times results in shortening the life of the entire catalytic converter. In this case, the microcomputer 6 adjusts to keep the catalyst temperature low to prevent shortening of life.

The configuration of the sensor is described in FIG. The sensor is composed of a sensor substrate 13 in which five pieces of sensor detection material 12 are applied in a ceramic protective tube 11 through which a large number of holes of about 0.1 mm in diameter are allowed to flow freely. The sensor board is connected to the sensor shocks 14 and the ceramic protective tube is screwed to the support 15.

EXAMPLE

When the boiler and the car are burned out of air, the sensor 3 detects the concentrations of carbon monoxide and hydrocarbons as voltages, and sends them to the microcomputer 6, which simultaneously measures the oxygen concentration and the temperature of the combustion exhaust gas as voltages. Is sent to the microcomputer 6 to compare and settle the value. Due to the lack of air combustion, there are many carbon dioxide and hydrocarbons, which are higher than the standard output voltage at the optimum combustion, and the blower (7) or damper (8) of the boiler until the value becomes zero or equal to the oxygen output voltage. In the case of automobiles, the air-fuel ratio is optimized by adjusting the opening time of the needle valve of the fuel injection.

On the contrary, when the excess air is burned, the output voltage of the carbon monoxide or hydrocarbon sensor is zero and the output voltage of the oxygen sensor is large.Then, it is optimized by adjusting the blower, damper or injector. Allow combustion. Likewise, if the combustion temperature is over 300 ° C or over, or the oxygen concentration is over 3.8% and over the microcomputer 6 set point, the open recirculation valve 9 is closed to close the nitrogen oxide compound. Suppress emissions. In addition, if the amount of carbon monoxide, hydrocarbons and nitrogen oxides in the sensor 3 and the sensor 5 is excessively discharged beyond the regulation value, the temperature of the catalytic purifier 3 is kept as high as possible to reduce the harmful exhaust gas.

4 is a sensor output voltage for each exhaust gas during air shortage combustion, and FIG. 5 shows changes in motor rotation, damper opening and closing angle, recirculating air valve opening and closing temperature, and catalyst purifier temperature according to the output voltage. The magnitude of the output voltage (solid line) obtained from the five composite sensors during combustion, and the dotted line is the reference voltage set in the microcomputer for optimal combustion. The formula is expressed as follows.

Where ΔV is the amount of change in the output voltage that corresponds to the deviation from the optimum combustion, and ΔV _t is the value that compensates for the temperature outside the 200 ° C reference set amount of the combustion exhaust gas, and k is a constant. The ΔV value eventually appears as in FIG. 5 as the amount of mechanical action ΔA to adjust the air-fuel ratio.

The value of ΔA is represented by the motor rotation speed, the damper angle and the opening time of the injector.

On the other hand, the opening and closing rotation angle of the recirculation valve is controlled based on the increase in exhaust gas temperature (+ ΔT) and the output by the oxygen concentration (Vo ₂ ), and the catalytic conversion temperature is kept high when there are a lot of harmful exhaust gases, and low when there is little. To be.

The present invention as described above can measure the air and fuel costs supplied to the combustion chamber by the type and concentration (amount) of the combustion exhaust gas to optimize the air-fuel ratio, thereby improving combustion efficiency and saving energy, and excessive soot and harmful exhaust gas. It is possible to create a pleasant environment by reducing emissions, and has an excellent effect of maintaining the long-term performance of the catalytic purifier and extending the life of the combustion apparatus.

Claims (2)

When the combustion device is under-air burned, the sensor 3 detects the concentrations of carbon monoxide and hydrocarbons as voltages and sends them to the microcomputer, and the oxygen, nitrogen oxide, and temperature sensors simultaneously measure the concentration of oxygen and the temperature of the combustion exhaust gas as voltages. Is sent to the microcomputer 6 to compare and settle the value. The amount of carbon monoxide and hydrocarbons due to the lack of air combustion is compared with the reference output voltage at the optimum combustion, and the opening and closing angles of the blower 8 or damper 7 of the boiler and the opening time of the injector until the value matches the reference voltage. Air-fuel ratio control method of the combustion flue gas measurement type combustion apparatus using a composite gas sensor, characterized in that to adjust the air-fuel ratio by adjusting the. The excess voltage of the carbon monoxide or hydrocarbon sensor is zero at the time of excess air combustion of the combustor, and the output voltage of the oxygen and nitrogen oxide sensor is largely negative, until the same as the reference voltage. On the contrary, by adjusting the blower, damper or injector, the optimum combustion is achieved.In the same way, as measured by the sensor (3) in excess air, the combustion temperature is higher than 300 ℃ or the concentration of oxygen is 4 ~ 10%. If abnormal, close the open recirculation valve (9) to suppress the release of nitric oxide compounds, and if the emissions of carbon monoxide, hydrocarbons and nitrogen oxides from the sensor (3) and sensor (5) excessively exceeded the regulation value, catalytic purifier The exhaust gas of the combustion device using the composite gas sensor, characterized in that to control the temperature of (4) as high as possible to discharge the harmful gas low Treatment method.