JP2017072313A - Superheating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superheating device capable of preventing corrosion of a superheater tube in a simple control process, without measuring a tube wall temperature of the superheater with a thermometer.SOLUTION: A primary controller 15 of a superheating device 1 compares a secondary superheater inlet temperature difference obtained by subtracting a measurement temperature of a secondary superheater inlet thermometer 11 from a predetermined secondary superheater inlet setting temperature with a secondary superheater outlet temperature difference obtained by subtracting a measurement temperature of a secondary superheater outlet thermometer 18 from a predetermined secondary superheater outlet setting temperature; when the secondary superheater inlet temperature difference is made larger, adjusts a supply amount of cooling water in a primary desuperheater 9 based on the measurement temperature of the secondary superheater inlet thermometer 11 so that the secondary superheater inlet temperature becomes the secondary superheater inlet setting temperature; and when the secondary superheater outlet temperature difference is made larger, adjusts the supply amount of cooling water in the primary desuperheater 9 based on the measurement temperature of the secondary superheater outlet thermometer 18 so that the secondary superheater outlet temperature becomes the secondary superheater outlet setting temperature.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a superheater in which a plurality of superheaters that are provided in a boiler that recovers heat from exhaust gas discharged from a waste treatment furnace and that superheats steam in a superheater tube by heat exchange with the exhaust gas are arranged in series.

  In a superheater provided in a heat recovery boiler provided in a waste treatment furnace, for example, an incinerator for incinerating garbage or industrial waste, a superheater having a superheater tube group is arranged in the boiler. Accordingly, the superheated tube group may corrode (high temperature corrosion) by contacting with a corrosive gas contained in the exhaust gas discharged from the waste treatment furnace at a high temperature. For this reason, the material of the superheated tube group is required to have corrosion resistance. However, when an expensive high corrosion resistance material is used, there is a problem that equipment costs increase.

  Then, in order to prevent the high temperature corrosion of a superheated tube group, controlling the tube wall temperature of a superheater like patent document 1, for example is known. In this patent document 1, in a boiler, three superheaters, a high temperature superheater, an intermediate temperature superheater, and a low temperature superheater, are arranged in order from the upstream side of exhaust gas. In these three superheaters, superheater tubes are connected in series. Steam flows through the superheater tube in the order of a low-temperature superheater, medium-temperature superheater, and high-temperature superheater. Thus, superheated steam is generated.

  A primary desuperheater is provided at the connection position between the low temperature superheater and the intermediate temperature superheater, and a secondary desuperheater is provided at the connection position between the intermediate temperature superheater and the high temperature superheater. By supplying cooling water to the superheated steam, the superheated steam is cooled to control the temperature of the superheated steam. In such a patent document 1, the superheated steam temperature near the inlet of the high-temperature superheater and the superheated tube wall temperature near the outlet of the intermediate-temperature superheater are respectively measured, and from the primary desuperheater based on those measured temperatures. Adjust the cooling water supply. In addition, the superheated steam temperature and the superheated tube wall temperature near the outlet of the high-temperature superheater are measured, and the supply amount of the cooling water from the secondary desuperheater is adjusted based on these measured temperatures.

  In Patent Document 1, in this way, the amount of cooling water supplied from each desuperheater, and thus the temperature of superheated steam, is adjusted, and a high temperature superheater that comes into contact with corrosive gas contained in exhaust gas at a high temperature in the boiler and By suppressing the tube wall temperature of each medium temperature superheater to a predetermined temperature or less, high temperature corrosion of the tube wall of each superheater is prevented.

JP 05-280707

  In Patent Document 1, the amount of cooling water supplied from each temperature reducer is controlled based on two types of measurement temperatures, that is, the temperature of the superheated steam and the temperature of the tube wall of the superheater. Compared with the case where the supply amount of the cooling water is controlled based on the temperature, the control process becomes complicated and the cost increases. In addition, in order to measure the tube wall temperature of the superheater, it is necessary to provide a thermometer on the superheater tube at the measurement position of the tube wall temperature, and this thermometer is disposed at a high temperature in the boiler. Therefore, there is a problem that the thermometer itself is easily damaged.

  In view of such circumstances, it is an object of the present invention to provide a superheater that does not require measurement of the tube wall temperature of the superheater and can prevent corrosion of the superheater tube with a simple control process.

  The superheater according to the present invention is a superheater provided in a boiler that recovers heat from exhaust gas discharged from a waste treatment furnace, and a plurality of superheaters that superheat the steam in the superheater tube by heat exchange with the exhaust gas are arranged in series. The plurality of superheaters includes a primary superheater that superheats steam supplied from outside the superheater to generate superheated steam, and a temperature higher than that of the primary superheater. A secondary superheater that superheats the superheated steam that has passed through, and a tertiary superheater that is arranged at a lower temperature than the secondary superheater and that superheats the superheated steam that has passed through the secondary superheater and then sends it to the outside of the superheater. Yes.

  In such a superheater, in the present invention, the primary superheater that supplies cooling water to the superheated steam sent to the secondary superheater to reduce the temperature of the superheated steam, and the secondary superheater that is reduced in temperature by the primary cooler. The secondary superheater inlet thermometer that measures the temperature of the superheated steam that is sent to the heater, and the secondary superheater outlet temperature that is the temperature of the superheated steam that is superheated by the secondary superheater The amount of cooling water supplied to the primary desuperheater is adjusted based on the measured temperature of the secondary superheater outlet thermometer and the measured temperature of the secondary superheater inlet thermometer or the measured temperature of the secondary superheater outlet thermometer A primary control device, a tertiary superheater outlet thermometer for measuring a tertiary superheater outlet temperature that is a temperature of superheated steam that is superheated by the tertiary superheater and sent to the outside of the superheater, and the tertiary superheater outlet temperature is a predetermined tertiary The above-mentioned tertiary superheater outlet temperature is set so as to be the superheater outlet set temperature. A secondary control device that adjusts the supply amount of cooling water in the secondary desuperheater based on the measured temperature of the meter, and the primary control device is configured to perform secondary superheating from a predetermined secondary superheater inlet set temperature. Secondary superheater obtained by subtracting the measured temperature of the secondary superheater outlet thermometer from the secondary superheater inlet temperature difference obtained by subtracting the measured temperature of the inlet thermometer and the predetermined secondary superheater outlet set temperature Compared with the outlet temperature difference, when the secondary superheater inlet temperature difference is larger, the secondary superheater inlet temperature is set so that the secondary superheater inlet temperature becomes the secondary superheater inlet set temperature. The amount of cooling water supplied in the primary desuperheater is adjusted based on the temperature measured by the thermometer, and when the secondary superheater outlet temperature difference is larger, the secondary superheater outlet temperature is set to the secondary superheater. The temperature measured by the secondary superheater outlet thermometer so that the set outlet temperature is Based on the temperature of the secondary superheater outlet set temperature to avoid high temperature corrosion of the superheater tube group of the secondary superheater and the tertiary superheater outlet It is characterized in that it is set based on the set temperature range.

  In the present invention, as described above, when the secondary superheater inlet temperature difference is larger than the secondary superheater outlet temperature difference, the primary controller reduces the primary reduction based on the measured temperature of the secondary superheater inlet thermometer. The secondary superheater inlet temperature is adjusted by adjusting the amount of cooling water supplied in the warmer. In addition, when the secondary superheater outlet temperature difference is larger than the secondary superheater inlet temperature difference, the primary controller determines that the cooling water in the primary desuperheater is based on the measured temperature of the secondary superheater outlet thermometer. The secondary superheater outlet temperature is adjusted by adjusting the supply amount. Further, the secondary control device adjusts the supply amount of the cooling water in the secondary desuperheater based on the measured temperature of the tertiary superheater outlet thermometer, thereby adjusting the tertiary superheater outlet temperature.

  In this way, in the present invention, the amount of cooling water supplied from the temperature reducer is adjusted based only on the temperature of the superheated steam, so that not only the temperature of the superheated steam but the superheater as in the prior art. As compared with the case where the supply amount of the cooling water is adjusted based on the temperature of the pipe wall, the control process of the supply amount of the cooling water is simplified. Moreover, in this invention, since it is not necessary to measure the tube wall temperature of a superheater with a thermometer, the situation where this thermometer is damaged does not arise.

  In the present invention, the superheater corrects the secondary superheater outlet set temperature based on the tertiary superheater outlet temperature difference obtained by subtracting the measured temperature of the tertiary superheater outlet thermometer from the tertiary superheater outlet set temperature. And a correction device that corrects the secondary superheater outlet set temperature to be higher when the tertiary superheater outlet temperature difference is larger than a predetermined tertiary superheater outlet maximum allowable temperature difference. When the heater outlet temperature difference is smaller than a predetermined tertiary superheater outlet minimum allowable temperature difference, correction for lowering the secondary superheater outlet set temperature may be performed.

  In this way, the correction device corrects the secondary superheater outlet set temperature based on the above-mentioned tertiary superheater outlet temperature difference, thereby obtaining the tertiary superheater outlet temperature difference and the tertiary superheater outlet maximum allowable temperature difference and the tertiary superheater outlet temperature. It can be maintained within a range between the minimum allowable temperature difference, and the superheated steam from the tertiary superheater can be set to an appropriate temperature so that the superheated steam has sufficient heat energy.

  In the present invention, when the primary superheater inlet temperature difference is smaller than a predetermined secondary superheater inlet maximum allowable temperature difference, the primary superheater inlet temperature becomes the secondary superheater inlet set temperature. As described above, the control in the first control mode for adjusting the supply amount of the cooling water in the primary desuperheater is performed based on the measured temperature of the secondary superheater inlet thermometer, and the control in the first control mode is performed. When the tertiary superheater outlet temperature difference obtained by subtracting the measured temperature of the tertiary superheater outlet thermometer from the predetermined tertiary superheater outlet set temperature is larger than the predetermined tertiary superheater outlet maximum allowable temperature difference, Second control that adjusts the supply amount of cooling water in the primary desuperheater so that the secondary superheater outlet temperature becomes the secondary superheater outlet set temperature based on the secondary superheater outlet temperature difference Control in mode, second control mode When performing the control of, the tertiary superheater outlet temperature difference becomes smaller than the predetermined tertiary superheater inlet minimum allowable temperature difference, it may be adapted to perform control in the first control mode.

  In this way, at the normal time when the secondary superheater inlet temperature difference is smaller than the predetermined secondary superheater inlet maximum allowable temperature difference, based on the measured temperature of the secondary superheater inlet thermometer, Control in the first control mode that adjusts the cooling water supply amount, the measured temperature of the tertiary superheater outlet thermometer is too low, and the tertiary superheater outlet temperature difference is larger than the predetermined tertiary superheater outlet maximum allowable temperature difference When it becomes larger, the supply amount of cooling water in the primary desuperheater is decreased so that the secondary superheater outlet temperature becomes the secondary superheater outlet set temperature based on the difference in temperature of the secondary superheater outlet. When the control in the second control mode is adjusted and the control in the second control mode is performed, if the tertiary superheater outlet temperature difference becomes smaller than the predetermined tertiary superheater inlet minimum allowable temperature difference, By controlling in one control mode, It is possible to reliably control the amount of cooling water supplied to prevent hot corrosion of the heat pipe, and to maintain the tertiary superheater outlet temperature at an appropriate temperature close to the set temperature of the tertiary superheater outlet. The superheated steam from the vessel can have sufficient thermal energy.

  As described above, according to the present invention, the amount of cooling water supplied from each desuperheater is adjusted based only on the temperature of the superheated steam. Compared with the case where the supply amount of the cooling water is adjusted based on the wall temperature, the control process of the supply amount of the cooling water for preventing the high temperature corrosion of the superheated pipe is simplified, and the cost can be suppressed. Moreover, since it is not necessary to measure the tube wall temperature of a superheater with a thermometer, the thermometer is not damaged.

It is a block diagram showing the outline composition of the superheater concerning the embodiment of the present invention. It is a flowchart which shows the process of selection of control mode. It is a flowchart which shows the control process in 1st control mode. It is a flowchart which shows the process of correction | amendment of secondary superheater exit preset temperature.

  Hereinafter, an apparatus according to an embodiment of the present invention will be described with reference to FIG. 1 of the accompanying drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a superheater 1 according to an embodiment of the present invention. The superheater 1 is provided, for example, in a boiler (not shown) that is attached to a waste treatment furnace (not shown) such as a waste incinerator and recovers heat from exhaust gas discharged from the waste treatment furnace. . The superheater 1 includes a primary superheater 2, a secondary superheater 3, and a tertiary superheater 4 (hereinafter referred to as “superheater 2 as necessary”, which are disposed in a boiler and superheat steam in a superheater pipe by heat exchange with exhaust gas. , 3, 4 ").

  The superheaters 2, 3, 4 are connected to each other through connecting pipes 6, 7, and the steam is heated while flowing through the superheater tubes in the order of the primary superheater 2, the secondary superheater 3, and the tertiary superheater 4. It has become so. Specifically, the primary superheater 2 and the secondary superheater 3 are connected by a connecting pipe 6, and the secondary superheater 3 and the tertiary superheater 4 are connected by a connecting pipe 7. The primary superheater 2 is connected to an introduction pipe 5 for receiving steam from a boiler drum (not shown), and the tertiary superheater 4 sends superheated steam to a steam sump (not shown). For this purpose, a delivery pipe 8 is connected.

  In the present embodiment, the secondary superheater 3, the tertiary superheater 4, and the primary superheater 2 are arranged in this order in the flow direction of the exhaust gas in the boiler. That is, the secondary superheater 3 is arranged at a higher temperature than the tertiary superheater 4 and the primary superheater 2, and the tertiary superheater 4 is arranged at a higher temperature than the primary superheater 2. In such a configuration, each of the superheaters 2, 3, 4 is firstly heated by the primary superheater 2 to superheat steam supplied from outside the superheater 1 through the introduction pipe 5, and then generates superheated steam. The secondary superheater 3 receives the superheated steam passed through the primary superheater 2 from the connection pipe 6 and superheats the superheated steam, and the tertiary superheater 4 connects the superheated steam passed through the secondary superheater 3 to the connection pipe. 7, the superheated steam is further superheated and then sent to the steam sump by the delivery pipe 8. The superheated steam sent to the steam sump has a sufficiently high temperature, and the thermal energy possessed by the superheated steam is used, for example, for power generation by a turbine (not shown).

  As shown in FIG. 1, the connecting pipe 6 is provided with a primary temperature reducer 9 that supplies cooling water to the superheated steam sent from the primary superheater 2 to the secondary superheater 3 to reduce the temperature of the superheated steam. It has been. Even if the secondary superheater 3 is arranged at a high temperature in the boiler, the temperature of the superheated steam is sufficiently reduced by the cooling water from the primary temperature reducer 9. The tube wall of the superheater tube does not become excessively hot, and high-temperature corrosion of the superheater tube of the secondary superheater 3 is well prevented.

  The amount of cooling water supplied from the primary temperature reducer 9 is controlled by adjusting the opening degree of the primary flow rate adjusting valve 10 connected to the primary temperature reducer 9 by a primary controller 15 described later. Specifically, the primary control device 15 further reduces the temperature of the superheated steam by increasing the amount of cooling water supplied by increasing the degree of opening of the primary flow rate regulating valve 10, and the degree of opening of the primary flow rate regulating valve 10. Decreasing the amount of cooling water supplied to reduce the temperature of superheated steam.

  Further, the connecting pipe 6 has a temperature of the superheated steam that is cooled by the primary temperature reducer 9 and sent to the secondary superheater 3 downstream of the primary temperature reducer 9 in the flow direction of the superheated steam. A secondary superheater inlet thermometer 11 for measuring the secondary superheater inlet temperature is provided.

  The connection pipe 7 is provided with a secondary temperature reducer 12 that supplies cooling water to the superheated steam sent from the secondary superheater 3 to the tertiary superheater 4 to reduce the temperature of the superheated steam. Even when the tertiary superheater 4 is disposed at a high temperature in the boiler, the superheated steam is sufficiently reduced by the cooling water from the secondary temperature reducer 12, so that the superheater of the tertiary superheater 4 is superheated. The tube wall of the tube is not excessively heated, and high-temperature corrosion of the superheated tube of the tertiary superheater 4 is well prevented.

  The supply amount of the cooling water from the secondary temperature reducer 12 is controlled by adjusting the opening degree of the secondary flow rate adjusting valve 13 connected to the secondary temperature reducer 12 by a secondary control device 16 described later. Is done. Specifically, the secondary control device 16 further reduces the temperature of the superheated steam by increasing the opening amount of the secondary flow rate adjustment valve 13 and increasing the supply amount of the cooling water. Decreasing the temperature of the superheated steam by reducing the amount of cooling water supplied by reducing the opening.

  The connecting pipe 7 measures the secondary superheater outlet temperature, which is the temperature of the superheated steam superheated by the secondary superheater 3, upstream of the secondary desuperheater 12 in the superheated steam flow direction. A next superheater outlet thermometer 18 is provided. The delivery pipe 8 is provided with a tertiary superheater outlet thermometer 14 for measuring the tertiary superheater outlet temperature, which is the temperature of the superheated steam that is superheated by the tertiary superheater 4 and sent to the sump.

  The superheater 1 according to the present embodiment further supplies the cooling water supply amount in the primary desuperheater 9 based on the measured temperature of the secondary superheater inlet thermometer 11 or the measured temperature of the secondary superheater outlet thermometer 18. A primary control device 15 that adjusts the amount of cooling water, a secondary control device 16 that adjusts the amount of cooling water supplied from the secondary desuperheater 12 based on the temperature measured by the tertiary superheater outlet thermometer 14, and a secondary superheater described later. And a correction device 17 for correcting the set outlet outlet temperature.

  In the present embodiment, for each of the secondary superheater inlet temperature, secondary superheater outlet temperature, and tertiary superheater outlet temperature, the secondary superheater inlet set temperature, the secondary superheater outlet set temperature, the tertiary superheater outlet set temperature. Is preset as a target value. Further, the secondary superheater outlet thermometer 18 is obtained from the secondary superheater inlet temperature difference obtained by subtracting the measured temperature of the secondary superheater inlet thermometer 11 from the secondary superheater inlet set temperature and the secondary superheater outlet set temperature. For each secondary superheater outlet temperature difference obtained by subtracting the measured temperature, the maximum allowable temperature difference at the secondary superheater inlet and the maximum allowable temperature difference at the secondary superheater outlet are preset as allowable maximum values. Yes. Further, regarding the tertiary superheater outlet temperature difference obtained by subtracting the measured temperature of the tertiary superheater outlet thermometer 14 from the set temperature of the tertiary superheater outlet, the maximum allowable temperature difference of the tertiary superheater outlet as the maximum allowable value and the allowable The minimum allowable temperature difference of the tertiary superheater outlet as a minimum value is set in advance.

  The primary controller 15 determines the magnitude relationship between the secondary superheater inlet temperature difference and the secondary superheater inlet maximum allowable temperature difference and the magnitude relationship between the secondary superheater outlet temperature difference and the secondary superheater outlet maximum allowable temperature difference. Based on the first control mode as the control mode in normal time and the second control mode as the control mode in emergency, the cooling water from the primary temperature reducer 9 is selected in the selected control mode. Control the supply amount.

  FIG. 2 is a flowchart showing a control mode selection process. First, the primary controller 15 subtracts the measured temperature of the secondary superheater inlet thermometer 11 from the set temperature of the secondary superheater inlet to calculate the secondary superheater inlet temperature difference (S1). When the secondary superheater inlet temperature difference is smaller than the secondary superheater inlet maximum allowable temperature difference, the primary controller 15 selects the first control mode as a normal time and, as will be described later, the first control mode Then, the supply amount of the cooling water in the primary temperature reducer 9 is controlled (S2).

  When performing control in the first control mode, the temperature difference of the tertiary superheater outlet obtained by subtracting the measured temperature of the tertiary superheater outlet thermometer from the predetermined tertiary superheater outlet set temperature is the predetermined tertiary superheater outlet When the difference is larger than the maximum allowable temperature difference (Y in S3), the primary control device 15 selects the second control mode and supplies the cooling water in the primary temperature reducer 9 in the second control mode, as will be described later. The amount is controlled (S4). On the other hand, when the tertiary superheater outlet temperature difference is smaller than the tertiary superheater outlet maximum allowable temperature difference (N in S3), the primary controller 15 selects the first control mode and continues the control in the first control mode. To do. When performing the control in the second control mode, when the tertiary superheater outlet temperature difference is smaller than the predetermined tertiary superheater outlet minimum allowable temperature difference (Y in S5), the primary control device 15 is in the first control mode. As described later, the supply amount of the cooling water in the primary temperature reducer 9 is controlled in the first control mode (S6). On the other hand, when the tertiary superheater outlet temperature difference is larger than the tertiary superheater outlet minimum allowable temperature difference (N in S5), the primary controller 15 selects the second control mode and continues control in the second control mode. To do.

  Next, the control process by the primary controller 15 will be described in the order of the first control mode and the second control mode.

<First control mode>
In the first control mode, the primary controller 15 calculates the secondary superheater inlet temperature difference and the secondary superheater outlet temperature difference, as described later with reference to FIG. When the superheater inlet temperature difference is larger, the supply amount of the cooling water in the primary desuperheater 9 is adjusted based on the measured temperature of the secondary superheater inlet thermometer 11, and the secondary superheater outlet temperature is adjusted. When the difference is larger, the supply amount of the cooling water in the primary temperature reducer 9 is adjusted based on the temperature measured by the secondary superheater outlet thermometer 18.

  FIG. 3 is a flowchart showing a control process in the first control mode. First, the primary controller 15 calculates the secondary superheater inlet temperature difference by subtracting the measured temperature of the secondary superheater inlet thermometer 11 from the set temperature of the secondary superheater inlet (S1). Moreover, the primary control apparatus 15 calculates a secondary superheater exit temperature difference by subtracting the measured temperature of the secondary superheater exit thermometer 18 from the secondary superheater exit set temperature (S2). Either S1 or S2 may be executed first or may be executed simultaneously.

  The primary controller 15 compares the secondary superheater inlet temperature difference calculated in S1 with the secondary superheater outlet temperature difference calculated in S2, and when the secondary superheater inlet temperature difference is larger ( Y of S3), the supply amount of cooling water in the primary desuperheater 9 based on the measured temperature of the secondary superheater inlet thermometer 11 so that the secondary superheater inlet temperature becomes the secondary superheater inlet set temperature Is adjusted (S4). On the other hand, when the secondary superheater outlet temperature difference is larger (N in S3), the primary controller 15 sets the secondary superheater outlet temperature so that the secondary superheater outlet temperature becomes the secondary superheater outlet set temperature. Based on the temperature measured by the thermometer 18, the supply amount of the cooling water in the primary temperature reducer 9 is adjusted (S5).

  In the present embodiment, the secondary superheater inlet set temperature is set to a low temperature that can prevent the occurrence of high-temperature corrosion in the superheater tube of the secondary superheater 3. The secondary superheater inlet set temperature may be set as a temperature range having a predetermined temperature range.

  Further, in the present embodiment, the secondary superheater outlet set temperature is set to a high temperature that allows the superheated steam sent from the tertiary superheater 4 to the steam sump to have sufficient thermal energy. . As will be described later, the secondary superheater outlet set temperature is corrected by the correction device 17 based on the tertiary superheater outlet temperature difference. The secondary superheater inlet set temperature may be set as a temperature range having a predetermined temperature range.

  In this embodiment, the secondary superheater inlet temperature difference and the secondary superheater outlet temperature difference are compared, and the larger temperature difference is reduced, i.e., the superheated steam that has become too low from the set temperature. The supply amount of the cooling water in the primary temperature reducer 9 is adjusted so as to increase the temperature. Therefore, both of the two effects of preventing the high temperature corrosion of the superheated tube of the secondary superheater 3 and ensuring sufficient thermal energy of the superheated steam from the tertiary superheater 4 can be surely obtained.

  The secondary control device 16 calculates the tertiary superheater outlet temperature difference by subtracting the measured temperature of the tertiary superheater outlet thermometer 14 from the tertiary superheater outlet set temperature, so as to eliminate the tertiary superheater outlet temperature difference, that is, The amount of cooling water supplied from the secondary desuperheater 12 is controlled by adjusting the opening of the secondary flow rate adjustment valve 13 so that the tertiary superheater outlet temperature becomes a predetermined tertiary superheater outlet set temperature. .

  In this embodiment, the tertiary superheater outlet set temperature is set to a high temperature that allows the superheated steam delivered from the tertiary superheater 4 to the outside of the superheater 1 to have sufficient thermal energy. The tertiary superheater outlet set temperature may be set as a temperature range having a predetermined temperature range.

<Second control mode>
When performing control in the first control mode, the temperature difference of the tertiary superheater outlet obtained by subtracting the measured temperature of the tertiary superheater outlet thermometer from the predetermined tertiary superheater outlet set temperature is the predetermined tertiary superheater outlet When larger than the maximum allowable temperature difference, the primary control device 15 selects and executes the second control mode. In the second control mode, the primary control device 15 is the primary desuperheater so that the secondary superheater outlet temperature becomes the secondary superheater outlet set temperature based on the secondary superheater outlet temperature difference. Adjust the amount of cooling water supplied. In other words, in the second control mode, in the situation where the tertiary superheater outlet temperature has become too low from the set temperature, the amount of cooling water supplied by the primary desuperheater is reduced so that the secondary superheater outlet temperature difference becomes small. Adjust. As a result, since the secondary superheater outlet temperature approaches the secondary superheater outlet set temperature, the tertiary superheater outlet temperature can also be maintained at an appropriate temperature close to the tertiary superheater outlet set temperature, and from the tertiary superheater. It is possible to ensure that the superheated steam has sufficient thermal energy.

  In this embodiment, based on the secondary superheater inlet temperature, the secondary superheater outlet temperature, and the tertiary superheater outlet temperature, that is, based on only the temperature of the superheated steam, the cooling water is supplied from each of the temperature reducers 9 and 12. Since the amount is adjusted, the control process is compared to the case where the supply amount of cooling water is adjusted based not only on the temperature of the superheated steam but also on the temperature of the tube wall of the superheater as in the past. Can be simplified and the cost can be reduced. Moreover, in this embodiment, since it is not necessary to arrange the thermometer for measuring the temperature of the said tube wall under high temperature in a boiler, the situation where this thermometer does not arise does not arise.

  The correction device 17 compares the tertiary superheater outlet temperature difference calculated by the secondary control device 16 with the tertiary superheater outlet temperature maximum allowable temperature difference and the tertiary superheater outlet temperature minimum allowable temperature difference, and determines the comparison result. Based on this, the secondary superheater outlet set temperature is corrected. The correction of the secondary superheater outlet set temperature may be periodically performed at a predetermined timing or may be continuously performed.

  FIG. 4 is a flowchart showing a process of correcting the secondary superheater inlet set temperature. Hereinafter, the correction of the secondary superheater outlet set temperature will be described with reference to FIG. First, the secondary control device 16 calculates the tertiary superheater outlet temperature difference by subtracting the measured temperature of the tertiary superheater outlet thermometer 14 from the tertiary superheater outlet set temperature (S1).

  When the tertiary superheater outlet temperature difference calculated in S1 is larger than the tertiary superheater outlet maximum allowable temperature difference (Y of S2), that is, when the tertiary superheater outlet temperature is too low, the correction device 17 Correction for increasing the next superheater outlet set temperature is performed (S3). By performing such correction, the temperature of the superheated steam from the secondary superheater 3 is increased. As a result, the temperature of the superheated steam from the tertiary superheater 4 is also increased, and the temperature range in which the tertiary superheater outlet temperature can be allowed. Can be maintained within.

  Further, when the tertiary superheater outlet temperature difference calculated in S1 is smaller than the tertiary superheater outlet maximum allowable temperature difference (N of S2), that is, when the tertiary superheater outlet temperature is too high, the tertiary superheater If the outlet temperature difference is smaller than the tertiary superheater outlet minimum allowable temperature difference (Y in S4), the correction device 17 performs correction to lower the secondary superheater outlet set temperature (S5). By performing such correction, the temperature of the superheated steam from the secondary superheater 3 is reduced. As a result, the temperature of the superheated steam from the tertiary superheater 4 is also reduced, and the temperature range in which the tertiary superheater outlet temperature is allowable. Can be maintained within. On the other hand, if the tertiary superheater outlet temperature difference is larger than the tertiary superheater outlet minimum allowable temperature difference (N in S4), the correction device 17 does not correct the secondary superheater outlet set temperature.

  In this embodiment, since the correction device 17 corrects the secondary superheater inlet set temperature based on the tertiary superheater outlet temperature difference as described above, the tertiary superheater outlet temperature difference is set to the tertiary superheater outlet maximum allowable temperature difference. It can be maintained within a range between the minimum allowable temperature difference at the outlet of the tertiary superheater, and the superheated steam from the tertiary superheater 4 can be set to an appropriate temperature so that the superheated steam has sufficient thermal energy.

  In the present embodiment, a total of three superheaters, a primary superheater 2, a secondary superheater 3, and a tertiary superheater 4, are arranged in series. Instead, the primary superheater and the secondary superheater are arranged. Another superheater may be disposed between the secondary superheater 3 and the secondary superheater 3 and the tertiary superheater 4.

DESCRIPTION OF SYMBOLS 1 Superheater 2 Primary superheater 3 Secondary superheater 4 Tertiary superheater 9 Primary desuperheater 11 Secondary superheater inlet thermometer 12 Secondary desuperheater 14 Tertiary superheater outlet thermometer 15 Primary controller 16 Secondary control Device 17 Correction device 18 Tertiary superheater inlet thermometer

Claims (3)

A superheater in which a plurality of superheaters that are provided in a boiler that recovers heat from exhaust gas discharged from a waste treatment furnace and superheats steam in a superheater tube by heat exchange with exhaust gas are arranged in series,
The plurality of superheaters includes a primary superheater that superheats steam supplied from outside the superheater to generate superheated steam, and superheats superheated steam that is disposed at a higher temperature than the primary superheater and that passes through the primary superheater. A superheater having a secondary superheater and a tertiary superheater that is arranged at a lower temperature than the secondary superheater and that superheats the superheated steam that has passed through the secondary superheater and sends the superheated steam outside the superheater,
A primary desuperheater that supplies cooling water to the superheated steam sent to the secondary superheater to reduce the temperature of the superheated steam;
A secondary superheater inlet thermometer that measures the secondary superheater inlet temperature, which is the temperature of the superheated steam that is reduced in temperature by the primary desuperheater and sent to the secondary superheater;
A secondary superheater outlet thermometer for measuring a secondary superheater outlet temperature which is a temperature of superheated steam superheated by the secondary superheater;
A primary control device that adjusts the supply amount of cooling water in the primary desuperheater based on the measured temperature of the secondary superheater inlet thermometer or the measured temperature of the secondary superheater outlet thermometer;
A tertiary superheater outlet thermometer for measuring a tertiary superheater outlet temperature, which is a temperature of superheated steam that is heated by the tertiary superheater and sent to the outside of the superheater;
Adjusting the supply amount of cooling water in the secondary desuperheater based on the measured temperature of the tertiary superheater outlet thermometer so that the tertiary superheater outlet temperature becomes a predetermined tertiary superheater outlet set temperature; With the next control device,
The primary control device is based on the difference between the secondary superheater inlet temperature difference obtained by subtracting the measured temperature of the secondary superheater inlet thermometer from the predetermined secondary superheater inlet set temperature and the predetermined secondary superheater outlet set temperature. Compared with the secondary superheater outlet temperature difference obtained by subtracting the measured temperature of the secondary superheater outlet thermometer, when the secondary superheater inlet temperature difference is larger, the secondary superheater inlet temperature is Adjust the supply amount of cooling water in the primary desuperheater based on the measured temperature of the secondary superheater inlet thermometer so that the secondary superheater inlet set temperature, and the secondary superheater outlet temperature When the difference is larger, the cooling at the primary desuperheater is based on the measured temperature of the secondary superheater outlet thermometer so that the secondary superheater outlet temperature becomes the set temperature of the secondary superheater outlet. Adjust the water supply amount so that the secondary superheater outlet set temperature is Superheater, characterized in that is set based on the temperature range and the tertiary superheater outlet set temperature range to avoid high-temperature corrosion of the superheating tube group of vessels. A correction device for correcting the secondary superheater outlet set temperature based on the tertiary superheater outlet temperature difference obtained by subtracting the measured temperature of the tertiary superheater outlet thermometer from the tertiary superheater outlet set temperature;
The correction device performs correction to increase the secondary superheater outlet set temperature when the tertiary superheater outlet temperature difference is larger than a predetermined tertiary superheater outlet maximum allowable temperature difference, and the tertiary superheater outlet temperature difference is predetermined. 2. The superheater according to claim 1, wherein when the temperature difference is smaller than the minimum allowable temperature difference at the third superheater outlet, correction for lowering the secondary superheater outlet set temperature is performed.   When the primary controller inlet temperature difference is smaller than a predetermined secondary superheater inlet maximum allowable temperature difference, the primary controller is configured so that the secondary superheater inlet temperature becomes the secondary superheater inlet set temperature. When the control in the first control mode is performed to adjust the cooling water supply amount in the primary desuperheater based on the temperature measured by the secondary superheater inlet thermometer, and the control in the first control mode is performed When the tertiary superheater outlet temperature difference obtained by subtracting the measured temperature of the tertiary superheater outlet thermometer from the predetermined tertiary superheater outlet set temperature is larger than the predetermined tertiary superheater outlet maximum allowable temperature difference, the secondary superheater Control in the second control mode for adjusting the cooling water supply amount in the primary desuperheater so that the secondary superheater outlet temperature becomes the secondary superheater outlet set temperature based on the outlet temperature difference And perform control in the second control mode. 3. The superheater according to claim 1, wherein the control in the first control mode is performed if the temperature difference at the outlet of the tertiary superheater becomes smaller than a predetermined minimum allowable temperature difference at the inlet of the tertiary superheater. .

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