KR20230157750A - Apparatus and method for controlling temperature of boiler exhaust gas - Google Patents

Abstract

In order to appropriately lower the temperature of the exhaust gas discharged from the boiler and flowing into the SCR, it is provided at the inlet of the SCR, which removes nitrogen oxides from the exhaust gas discharged from the boiler, and supplies outdoor air to the exhaust gas flowing into the SCR to reduce the exhaust gas temperature. Provides a boiler exhaust gas temperature control device structured to reduce .

Description

Boiler exhaust gas temperature control device and temperature control method {APPARATUS AND METHOD FOR CONTROLLING TEMPERATURE OF BOILER EXHAUST GAS}

The present disclosure relates to an apparatus and method for controlling boiler exhaust gas temperature upstream of an SCR.

Generally, power generation facilities generate energy such as electricity and steam using heat energy generated by burning fossil fuel through a boiler. The exhaust gas discharged from the boiler of power generation facilities contains pollutants such as nitrogen oxides, so it goes through treatment facilities to prevent air pollution to remove harmful gases.

Exhaust gas treatment methods include wet methods and dry methods, and the Selective Catalytic Reduction (SCR) method, which reduces nitrogen oxides to nitrogen and moisture using a catalyst, is mainly used because it is advantageous from an economic and technical standpoint. Accordingly, an SCR is placed at the rear of the boiler to treat harmful gases in the exhaust gas. The exhaust gas discharged from the boiler passes through the SCR, passes through an air preheater and dust collector, and is discharged through the chimney.

However, when the temperature of the exhaust gas discharged from the boiler rises and remains high due to operation changes or fuel switching, a phenomenon occurs that exceeds 415°C, the maximum continuous use temperature of the SCR catalyst. Accordingly, when the SCR catalyst is exposed to high temperatures, the catalyst activity is reduced due to thermal fatigue of the catalyst, its lifespan is reduced, and operating costs increase due to frequent catalyst replacement.

Accordingly, in order to prevent the catalytic performance of the SCR from deteriorating, the boiler is operated with reduced output within the maximum allowable temperature of the exhaust gas, resulting in a decrease in power generation efficiency.

This project is to provide a boiler exhaust gas temperature control device and temperature control method that can appropriately lower the temperature of the exhaust gas discharged from the boiler and flowing into the SCR.

This project is to provide a boiler exhaust gas temperature control device and temperature control method that can extend the life of SCR.

The temperature control device of this embodiment may be provided at the inlet side of the SCR, which removes nitrogen oxides from the exhaust gas discharged from the boiler, and may be structured to reduce the exhaust gas temperature by supplying outside air to the exhaust gas flowing into the SCR.

The control device may be installed in an inlet duct connected to the inlet of the SCR and include at least one supply pipe for introducing outside air into the interior, and a damper for selectively opening and closing the supply pipe.

The control device operates a first temperature sensor installed in the inlet duct to detect the temperature of the exhaust gas, calculates the output signal of the first temperature sensor, and generates the damper opening/closing signal when the temperature of the exhaust gas flowing into the SCR is above the reference value. It may further include a control unit that outputs the output and opens the supply pipe.

The control device further includes a second temperature sensor installed on the output side of the SCR to detect the temperature of the exhaust gas that has passed through the SCR, and the control unit calculates the output signal of the second temperature sensor to determine the temperature of the exhaust gas that has passed through the SCR. If the temperature is below the reference value, the damper opening/closing signal may be output to close the supply pipe.

The first temperature sensor may be installed between the oxygen sensor installed in the inlet duct and the supply pipe.

The temperature reduction method of this embodiment may include reducing the temperature of the exhaust gas by supplying outside air to the inlet of the SCR, which is disposed at the rear of the boiler and removes nitrogen oxides in the exhaust gas discharged from the boiler.

The temperature reduction method includes detecting the temperature of the exhaust gas flowing into the SCR from a first temperature sensor provided at the entrance of the SCR, calculating whether the temperature of the exhaust gas detected by the first temperature sensor is greater than a reference value, and exhaust gas If the temperature is above the reference value, a step of introducing external air toward the SCR inlet may be included.

The temperature reduction method includes detecting the temperature of the exhaust gas discharged from the SCR from a second temperature sensor provided on the SCR output side, calculating whether the temperature of the exhaust gas detected by the second temperature sensor is below a reference value, and exhaust gas If the temperature is below the reference value, the step of blocking the supply of external air may be further included.

According to this embodiment, by lowering the temperature of the high-temperature exhaust gas of the boiler by introducing outside air, it is possible to always introduce exhaust gas of an appropriate temperature into the SCR. Accordingly, it is possible to increase economic efficiency by protecting the catalyst from high-temperature exhaust gas and increasing output.

Additionally, the lifespan of the SCR catalyst can be maximized by protecting it from high-temperature exhaust gases. Accordingly, maintenance costs can be reduced by reducing the number of catalyst replacements, and the time and cost and safety accidents due to frequent replacement work can be reduced.

1 is a schematic diagram showing a boiler exhaust gas temperature control device installed in an SCR according to this embodiment.
Figure 2 is a graph showing the temperature change of exhaust gas when the supply pipe of the temperature control device is opened according to this embodiment.
Figure 3 is a graph showing changes in oxygen and nitrogen oxides in the exhaust gas discharged from the chimney when the supply pipe of the temperature control device is opened according to this embodiment.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later. The embodiments described below may be modified into various forms without departing from the concept and scope of the present invention. As much as possible, identical or similar parts are indicated using the same reference numerals in the drawings.

The terminology used below is only for referring to specific embodiments and is not intended to limit the invention. As used herein, singular forms include plural forms unless phrases clearly indicate the contrary. As used in the specification, the meaning of "comprising" is to specify a specific characteristic, area, integer, step, operation, element and/or component, and to specify another specific property, area, integer, step, operation, element, component and/or group. It does not exclude the existence or addition of .

Figure 1 shows a boiler exhaust gas temperature control device installed in the SCR according to this embodiment, and Figure 2 shows the outside air inflow structure of the temperature control device in more detail.

Hereinafter, for convenience of explanation, the front side along the direction in which the exhaust gas travels will be referred to as the front end, and the back side will be referred to as the rear end.

As shown in FIG. 1, an SCR 110 is disposed at the rear of the boiler 100 to treat harmful gases in the exhaust gas. The exhaust gas discharged from the boiler 100 flows into the SCR 110 along the inlet duct 112 of the SCR 110, and nitrogen oxides (NOx) are removed as it passes through a catalyst layer provided inside the SCR 110. The exhaust gas that passes through the catalyst layer and exits the SCR (110) passes through the air preheater (120) and dust collector (130) and is discharged through the chimney (140).

The temperature control device of this embodiment is provided in the inlet duct 112 of the SCR (110) and reduces the exhaust gas temperature by introducing outside air into the inlet duct 112 when the temperature of the exhaust gas flowing into the SCR (110) is high. It could be a structure.

Accordingly, the temperature of the exhaust gas is lowered by the outside air, so the catalyst layer installed in the SCR 110 can be protected from the high temperature exhaust gas, and the lifespan of the catalyst layer can be prevented from being shortened.

For this purpose, the control device of this embodiment is installed in the inlet duct 112 connected to the inlet of the SCR 110, and includes at least one supply pipe 10 for introducing outside air into the interior, and selectively opening and closing the supply pipe 10. It may include a damper (12).

The supply pipe 10 is a pipe structure through which outside air can circulate, and at least one supply pipe may be installed along the inlet duct 112. The size or installed number of supply pipes 10 may vary depending on the specifications of the boiler 100 equipment or the amount of external air inflow.

A damper 12 is installed on the supply pipe 10 to open and close the supply pipe 10. When the damper 12 is operated to open, the supply pipe 10 opens and external air flows into the inlet duct 112. When the damper 12 is closed and operated, the supply pipe 10 is closed and the inflow of outside air is blocked. The damper 12 can be applied to any structure that can open and close the supply pipe 10.

The damper 12 may have a structure that is opened and closed manually by an operator. In addition to this structure, the damper 12 may be connected to a driving unit such as a motor or cylinder and be mechanically opened and closed using the power of the driving unit.

In the case of a structure in which a plurality of supply pipes 10 are arranged, each supply pipe 10 can be selectively opened and closed by individually driving the damper 12 installed on each supply pipe 10. The flow rate of external air flowing into the inlet duct 112 at a time can be adjusted depending on the number of openings and closings of the supply pipes 10. Accordingly, by adjusting the inflow amount of outdoor air, an appropriate amount of outdoor air can be supplied in accordance with the exhaust gas temperature.

In addition, the control device includes a first temperature sensor 20 installed in the inlet duct 112 to detect the temperature of the exhaust gas, and a first temperature sensor 20 installed on the output side of the SCR 110 to detect the temperature of the exhaust gas passing through the SCR 110. It may further include a control unit 30 that calculates the output signals of the second temperature sensor 22, the first temperature sensor 20, and the second temperature sensor 22 and outputs an opening/closing signal of the damper 12.

The first temperature sensor 20 detects the temperature of the exhaust gas flowing into the SCR 110, that is, the temperature of the exhaust gas in a state that is not mixed with the outside air.

In this embodiment, the first temperature sensor 20 may be installed between the oxygen sensor S installed in the inlet duct 112 and the supply pipe 10. Accordingly, the temperature of the exhaust gas passing through the inlet duct 112 can be accurately detected through the first temperature sensor 20.

When the first temperature sensor 20 is installed later than the supply pipe 10, it is difficult to accurately detect the exhaust gas temperature due to external air flowing in from the supply pipe 10. If the first temperature sensor 20 is installed in front of the oxygen sensor S, the oxygen sensor S may be interfered with by external air flowing in from the supply pipe 10, causing incomplete combustion.

In this way, in this embodiment, the first temperature sensor 20 is disposed between the oxygen sensor S and the supply pipe 10, making it possible to accurately measure the exhaust gas temperature while preventing interference with the oxygen sensor S. .

The supply pipe 10 is also installed along the inlet duct 112 at the rear of the oxygen sensor (S) as well as the first temperature sensor (20), so when outside air is introduced, the first temperature sensor (20) and the oxygen sensor (S) are Interference can be prevented.

The second temperature sensor 22 is installed at the outlet where the exhaust gas that has passed through the SCR (110) is discharged. It is sufficient for the second temperature sensor 22 to detect the temperature of the exhaust gas that has passed through the catalyst layer at the exit side of the SCR 110, and the installation location can be modified in various ways.

The temperature of the exhaust gas that has passed through the catalyst layer is detected by the second temperature sensor 22.

The control unit 30 calculates the temperature value of the exhaust gas detected by the first temperature sensor 20 and the temperature value of the exhaust gas detected by the second temperature sensor 22 and outputs a signal to open and close the damper 12. .

In the case of the manual damper 12, the operator can open and close the damper 12 according to the output signal of the control unit 30. In the case of the damper 12 that is mechanically opened and closed by an external driving force, the driving unit is controlled according to the output signal of the control unit 30 to open and close the damper 12.

In this embodiment, the control unit 30 may internally store in advance an equation for comparing the reference value and the actual temperature value using data on the maximum and minimum temperature values of the exhaust gas flowing into the SCR 110 as the reference value. there is.

For example, the reference value for the maximum value of the exhaust gas temperature flowing into the SCR (110) (hereinafter referred to as the maximum reference value) is set to 430°C, preferably 400°C, which is the maximum allowable temperature to prevent deterioration in the performance of the denitrification catalyst. It can be. And the reference value for the lowest temperature of the exhaust gas discharged through the SCR (110) (hereinafter referred to as the lowest reference value) may be set to 320°C, preferably 350°C.

In this way, the exhaust gas temperature detected by the first temperature sensor 20 is applied to the control unit 30, and the control unit 30 can open the supply pipe 10 by sending an output signal according to this temperature value. As the supply pipe 10 is opened, outside air flows in and the temperature of the exhaust gas is lowered below the maximum standard value. Additionally, the control unit 30 may send an output signal according to the temperature of the exhaust gas detected by the second temperature sensor 22 to close the supply pipe 10. As the supply pipe 10 is closed, the inflow of external air is blocked and the exhaust gas temperature rises.

Therefore, the temperature of the exhaust gas flowing into the SCR (110) is maintained in an appropriate range by this control device, making it possible to protect the catalyst of the SCR (110) from high-temperature exhaust gas and increase output.

Hereinafter, the process of controlling the exhaust gas temperature by the control device of this embodiment will be described.

The temperature control of this embodiment detects the temperature of the exhaust gas flowing into the SCR (110) from the first temperature sensor 20, and calculates whether the temperature of the exhaust gas detected from the first temperature sensor 20 is above the reference value. Therefore, when the exhaust gas temperature is above the set value, it can be achieved through a process of introducing outside air toward the inlet of the SCR (110).

In addition, when the temperature of the exhaust gas drops, the temperature of the exhaust gas discharged from the SCR (110) is detected from the second temperature sensor 22, and the temperature of the exhaust gas detected by the second temperature sensor 22 is below the set value. By calculating whether the exhaust gas temperature is below the set value, the exhaust gas temperature is increased through a process of blocking the supply of external air.

If the temperature of the exhaust gas detected by the first temperature sensor 20 is below the maximum standard value, the control unit 30 maintains the supply pipe 10 in a closed state. Accordingly, outside air is not introduced, and the exhaust gas flows directly into the SCR (110).

When the exhaust gas temperature detected by the first temperature sensor 20 exceeds the maximum standard value, the control unit 30 may apply an output signal for opening the supply pipe 10. As the damper 12 is opened according to the output signal of the control unit 30, the supply pipe 10 is opened and external air flows into the inlet duct 112 through the supply pipe 10. Therefore, as cold outside air is mixed with the exhaust gas, the temperature of the exhaust gas flowing into the SCR (110) falls below the maximum standard value and is lowered to an appropriate temperature.

When there are multiple supply pipes 10, the number of supply pipes 10 to be opened may vary depending on the temperature difference between the highest standard value and the exhaust gas. The larger the difference, the more supply pipes 10 can be opened, and if the difference is small, the number of supply pipes 10 to be opened can be reduced.

In this way, by mixing the exhaust gas with outside air, the temperature of the exhaust gas flowing into the SCR (110) can be preferably managed to below 400°C, which is suitable for operating the SCR (110).

The temperature of the exhaust gas that has passed through the SCR (110) is detected by the second temperature sensor (22) as it passes through the outlet of the SCR (110).

When the temperature of the exhaust gas detected by the second temperature sensor 22 is higher than the minimum standard value, the control unit 30 can keep the supply pipe 10 in an open state. Accordingly, outside air continues to flow into the inlet duct 112, thereby lowering the temperature of the exhaust gas and supplying it to the SCR (110).

As the supply pipe 10 opens and outdoor air continues to flow into the inlet duct 112, the temperature of the exhaust gas through the SCR 110 gradually decreases.

Accordingly, when the exhaust gas temperature detected by the second temperature sensor 22 is lower than the minimum standard value, the control unit 30 may apply an output signal for closing the supply pipe 10. According to the output signal of the control unit 30, the damper 12 is closed and the supply pipe 10 is closed to block the inflow of external air. Accordingly, the exhaust gas is not mixed with cold outside air, and the temperature of the exhaust gas flowing into the SCR (110) becomes higher than the minimum standard value.

When there are multiple supply pipes 10, the number of supply pipes 10 to be closed may vary depending on the temperature difference between the minimum standard value and the exhaust gas. The larger the difference, the more supply pipes 10 can be closed, and if the difference is small, the number of supply pipes 10 to be closed can be reduced.

In this way, by closing the supply pipe 10 to prevent outside air from mixing with the exhaust gas, the temperature of the exhaust gas flowing into the SCR (110) can be increased and preferably managed to above 350°C, which is suitable for operating the SCR (110). .

Figure 2 is a graph showing the change in temperature of exhaust gas according to opening of the supply pipe.

In the graph of Figure 2, the horizontal axis represents time, and the vertical axis represents temperature. Additionally, the upper and lower lines in the graph represent measurements for the two SCRs connected to the boiler.

The experiment was conducted by continuously detecting and comparing the exhaust gas temperature in a state in which the supply pipe installed in the inlet duct of the SCR was not opened as in the past and in a state in which the supply pipe was opened as in this embodiment.

As can be seen in the graph of FIG. 2, the experimental results show that when the supply pipe is opened and outdoor air is mixed as in this embodiment, the temperature change value of the exhaust gas decreases by about 30°C on average compared to the case where there is no conventional supply pipe. there is.

Therefore, it can be seen that this control device can lower the temperature of high-temperature exhaust gas and supply it to the SCR.

Figure 3 is a graph showing changes in oxygen and nitrogen oxides in the exhaust gas discharged from the chimney when the supply pipe is opened.

In the experiment, the oxygen content and nitrogen oxide content of the exhaust gas discharged from the chimney were detected without opening the supply pipe installed in the inlet duct of the SCR, and the exhaust gas discharged from the chimney with the outside air introduced by opening the supply pipe was measured. This was done by detecting the oxygen content and nitric acid content and comparing them.

As shown in the experimental results of Figure 3, when outside air was introduced, the oxygen content increased by 0.4% but remained within normal values, and nitrogen oxides decreased by 13ppm.

In addition, due to the inflow of outside air, the temperature drop of the air preheater, the increase in the dust collector inlet temperature, and the increase in chimney outlet temperature were very slight or almost non-existent.

Accordingly, it can be confirmed that the performance of the boiler equipment and SCR does not deteriorate even if the exhaust gas temperature is lowered by introducing outside air into the exhaust gas according to this embodiment.

Although exemplary embodiments of the present invention have been shown and described as described above, various modifications and other embodiments will occur to those skilled in the art. These modifications and other embodiments are to be considered and included in the appended claims without departing from the true spirit and scope of the present invention.

10: supply pipe 12: damper
20: first temperature sensor 22: second temperature sensor
30: control unit

Claims (7)

A boiler exhaust gas temperature control device provided at the inlet of the SCR that removes nitrogen oxides from the exhaust gas discharged from the boiler, and reduces the exhaust gas temperature by supplying outside air to the exhaust gas flowing into the SCR. According to claim 1,
A boiler exhaust gas temperature control device including at least one supply pipe installed in an inlet duct connected to the inlet of the SCR to introduce outside air into the interior, and a damper that selectively opens and closes the supply pipe. According to claim 2,
A first temperature sensor installed in the inlet duct to detect the temperature of the exhaust gas, and an output signal of the first temperature sensor are calculated to output the damper opening/closing signal when the temperature of the exhaust gas flowing into the SCR is higher than the reference value. A boiler exhaust gas temperature control device further comprising a control unit that opens the supply pipe. According to claim 3,
It further includes a second temperature sensor installed on the output side of the SCR to detect the temperature of the exhaust gas that has passed through the SCR, and the control unit calculates the output signal of the second temperature sensor to determine if the temperature of the exhaust gas that has passed through the SCR is below the reference value. A boiler exhaust gas temperature control device configured to close the supply pipe by outputting the damper opening/closing signal. A boiler exhaust gas temperature control method comprising reducing the temperature of the exhaust gas by supplying outside air to the inlet of the SCR, which is disposed at the rear of the boiler and removes nitrogen oxides in the exhaust gas discharged from the boiler. According to claim 5,
The temperature reduction step includes detecting the temperature of the exhaust gas flowing into the SCR from a first temperature sensor provided at the entrance of the SCR, calculating whether the temperature of the exhaust gas detected by the first temperature sensor is above a reference value, and A boiler exhaust gas temperature control method including the step of introducing outside air toward the SCR inlet when the exhaust gas temperature is above the reference value. According to claim 6,
The temperature reduction step includes detecting the temperature of the exhaust gas discharged from the SCR from a second temperature sensor provided on the SCR output side, calculating whether the temperature of the exhaust gas detected by the second temperature sensor is below a reference value, and A boiler exhaust gas temperature control method further comprising blocking the supply of external air when the temperature of the exhaust gas is below the reference value.

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