JP2019090559A - Temperature controller of heat exchanger for boiler exhaust gas - Google Patents

Abstract

To provide a temperature controller of a heat exchanger for boiler exhaust gas, capable of controlling deterioration of heat exchanging performance of a heat recovery device paired with a reheater, and of reducing steam consumption.SOLUTION: The temperature controller of a heat exchanger for a boiler exhaust gas comprises: a heat recovery device 4 that recovers heat of exhaust gas discharged from a boiler 1, using a heat medium; and a reheater 9 that re-heats the exhaust gas using the heat medium having recovered the heat of the exhaust gas in the heat recovery device 4. The reheater 9 comprises: a first heat exchanging part 9A that re-heats the exhaust gas using a first heat medium; and a second heat exchanging part 9B that re-heats the exhaust gas using a second heat medium of a higher temperature relative to the first heat medium. The temperature controller of a heat exchanger for a boiler exhaust gas further comprises: a first heat-medium flow-rate control mechanism 15 for controlling a flow rate of the first heat medium introduced into the first heat exchanging part 9A according to a temperature Tof the first heat medium at an outlet side of the first heat exchanging part 9A; and a second heat-medium flow-rate control mechanism 20 for controlling a flow rate of the second heat medium introduced into the second heat exchanging part 9B according to the temperature Tof the exhaust gas at an outlet side of the reheater 9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a temperature control device for a boiler exhaust gas heat exchanger.

  Generally, in a boiler plant of a thermal power plant using a fossil fuel such as coal, a desulfurization device is provided to remove sulfur oxides contained in exhaust gas.

  As the desulfurization apparatus, a wet desulfurization apparatus using a lime-gypsum method is mainly used, but in the absorption tower of the wet desulfurization apparatus, the exhaust gas at the outlet of the absorption tower is in contact with the absorption liquid. It becomes a water saturated gas, which causes corrosion of the exhaust gas line due to scattered mist and condensed water from the absorption tower and causes white smoke at the chimney exit. In order to prevent these, a reheater is installed downstream of the absorption tower to raise the temperature of the exhaust gas and exhaust it from the chimney.

  As a thing showing the general technical level relevant to the temperature control of the waste gas by the said reheater, there exists patent document 1, for example.

  In the one disclosed in Patent Document 1, the heat recovery device installed on the upstream side of the absorption tower in the middle of the exhaust gas line of the boiler recovers the heat of the exhaust gas by the heat medium, and the heat medium having the heat of the exhaust gas recovered is It is introduced into the reheater installed on the downstream side of the absorption tower to raise the temperature of the exhaust gas, and the heat medium introduction line of the reheater heats the heat medium by the steam generated by the boiler. A heating medium heater is provided. When the temperature of the exhaust gas detected by the exhaust gas temperature sensor provided in the exhaust gas line on the outlet side of the reheater is less than a set temperature (for example, about 90 to 93 ° C.), Steam is supplied, and the temperature of the heat medium introduced into the reheater is raised by heat exchange with the steam in the heat medium heater, and the temperature of the outlet side exhaust gas of the reheater is kept above the set temperature by the heat medium Be done. The steam used to raise the temperature of the heat medium in the heat medium heater becomes a steam drain and is stored in the steam drain tank from the steam drain line. Thereafter, the steam drain is supplied by the steam drain pump to the steam drain heat transfer pipe group disposed in the exhaust gas line on the outlet side of the reheater, and after being subjected to heat exchange again, sent to the boiler plant side. It has become.

Japanese Patent Application Laid-Open No. 11-153318

  However, in the case disclosed in Patent Document 1, when trying to keep the temperature of the outlet side exhaust gas of the reheater above the set temperature, the flow rate of the steam supplied to the heating medium heater increases, and the reheater discharges. The side heat medium temperature may rise more than necessary and may exceed the set temperature (for example, about 70 ° C.). In this case, steam is consumed wastefully.

  Moreover, when the temperature of the heat medium on the outlet side of the reheater rises more than necessary to maintain the temperature of the outlet side exhaust gas of the reheater above the set temperature, a heat recovery unit forming a pair with the reheater The temperature of the incoming heat medium introduced to the When the temperature of the heat transfer medium entering the heat recovery device is increased, the logarithmic mean temperature difference (LMTD) of the heat recovery device is reduced, so that the heat exchange performance may be reduced. When the heat recovery performance is lowered, the heat required for the reheater can not be recovered by the heat recovery unit, the flow rate of steam used in the heat medium heater increases, and the temperature of the heat medium on the outlet side of the reheater becomes Furthermore, it has risen and it has fallen into a vicious circle, and it had the fault that the waste of steam will further increase.

  The present invention has been made in view of the above-mentioned conventional problems, and it is a heat exchanger for a boiler exhaust gas that can suppress the decrease in heat exchange performance of a heat recovery unit forming a pair with a reheater and reduce the consumption of steam. It is an object of the present invention to provide a temperature control device for

In order to achieve the above object, the temperature control device for a boiler exhaust gas heat exchanger according to the present invention comprises a heat recovery device for recovering heat of exhaust gas discharged from the boiler by a heat medium;
A temperature controller for a boiler exhaust gas heat exchanger, comprising: a reheater reheating the exhaust gas with a heat medium in which the heat of the exhaust gas is recovered by the heat recovery unit;
The reheater includes a first heat exchange unit that reheats the exhaust gas with a first heat medium, and a second heat exchange unit that reheats the exhaust gas with a second heat medium that is hotter than the first heat medium.
A first heat medium flow control mechanism for adjusting the flow rate of the first heat medium introduced into the first heat exchange section based on the temperature of the first heat medium output side of the first heat exchange section;
And a second heat medium flow control mechanism for adjusting the flow rate of the second heat medium introduced to the second heat exchange unit based on the temperature of the outlet side exhaust gas of the reheater.

In the temperature control device for a boiler exhaust gas heat exchanger, the first heat medium flow control mechanism is
A bypass line connecting a first heat medium introduction line to the first heat exchange section and a first heat medium lead line from the first heat exchange section;
And a first heat medium flow control valve for adjusting the flow rate of the first heat medium diverted to the bypass line.

In the temperature control device of the boiler exhaust gas heat exchanger, the first heat medium flow control mechanism is
A first heat medium temperature sensor may be provided that detects the temperature of the output first heat medium and outputs an opening adjustment signal to the first heat medium flow control valve.

In the temperature control device of the boiler exhaust gas heat exchanger, the second heat medium flow control mechanism includes:
A second heat medium flow control valve for adjusting the flow rate of the second heat medium introduced into the second heat exchange unit;
And an exhaust gas temperature sensor that detects an outlet side exhaust gas temperature and outputs an opening degree adjustment signal to the second heat medium flow rate adjustment valve.

  In the temperature control device of the boiler exhaust gas heat exchanger, the first heat medium may be water, and the second heat medium may be steam generated by the boiler.

  According to the temperature control device for a boiler exhaust gas heat exchanger of the present invention, it is possible to suppress the decrease in heat exchange performance of the heat recovery unit forming a pair with the reheater, and to achieve an excellent effect of reducing the consumption of steam. obtain.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole outline | summary block diagram which shows the Example of the temperature control apparatus of the heat exchanger for boiler waste gases of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

  FIG. 1 shows an embodiment of a temperature control system for a boiler exhaust gas heat exchanger according to the present invention.

  In the embodiment shown in FIG. 1, in the exhaust gas line 2 of the boiler 1, from the upstream side, the air preheater 3, the heat recovery device 4, the electric precipitator 5, the induction ventilator 6, the absorption tower 8 of the desulfurization device 7, A heater 9 and a chimney 10 are arranged.

  The boiler 1 burns fuel such as coal and generates steam.

  The air preheater 3 preheats the combustion air introduced into the boiler 1 with exhaust gas.

  The heat recovery unit 4 is configured to recover the heat of the exhaust gas discharged from the boiler 1 and passed through the air preheater 3 by a heat transfer medium (first heat transfer medium).

  The electrostatic precipitator 5 is adapted to collect dust contained in the exhaust gas that has passed through the heat recovery unit 4.

  The induction ventilator 6 pressurizes the exhaust gas from which dust is collected by the electrostatic precipitator 5 and feeds it to the absorption tower 8 of the desulfurization apparatus 7.

  The absorption tower 8 of the desulfurization apparatus 7 is configured to bring the exhaust gas fed from the induced draft fan 6 into contact with the absorbing liquid to remove sulfur oxides contained in the exhaust gas.

  The reheater 9 includes a first heat exchange unit 9A and a second heat exchange unit 9B. In the first heat exchange unit 9A, a first heat medium introduction line 11 extending from the heat recovery unit 4 and a first heat medium lead line 12 leading to the heat recovery unit 4 are connected, and an exhaust gas is generated by the first heat medium. Is supposed to reheat. The first heat medium is, for example, water (chemically treated pure water) circulated between the heat recovery unit 4 and the first heat exchange unit 9A by the operation of a pump (not shown). The second heat exchange unit 9B is connected to the second heat medium introduction line 13 extending from the boiler 1 and the drain discharge line 14, and reheats the exhaust gas by the second heat medium having a temperature higher than that of the first heat medium. It is supposed to be. The second heat medium is steam generated by the boiler 1.

The first heat exchange unit 9A of the reheater 9 is provided with a first heat medium flow rate adjusting mechanism 15. The first heat medium flow control mechanism 15 includes a first heat medium introduction line 11 to the first heat exchange unit 9A and a first heat medium discharge line 12 from the first heat exchange unit 9A as a bypass line 16. The first heat medium flow control valves 17a and 17b are provided in the bypass line 16 and the first heat medium introduction line 11, and the flow rate of the first heat medium diverted to the bypass line 16 is the first heat medium flow control valve 17a. , 17b are configured to adjust. The first heat medium flow control valve 17 b is provided in the first heat medium introduction line 11 downstream of the branch point of the bypass line 16. The first heat medium flow control valves 17a and 17b may use orifices whose opening degree can be adjusted. Furthermore, a first heat medium temperature sensor 18 is provided on the first heat medium lead-out line 12 downstream of the junction point of the bypass line 16, and the first heat medium temperature sensor 18 outputs the first heat medium temperature wherein detecting a T ₁ first heat medium flow control valve 17a, and outputs opening adjustment signal 19a, and 19b to 17b. The first heat medium temperature sensor 18 stores in advance a set temperature T _S1 (for example, about 70 ° C.) at which corrosion by acid does not occur inside the reheater 9. Thus, the first heat medium flow rate control mechanism 15, the flow rate of the first heat medium introduced into the delivery side first heat based on the medium temperature T ₁ of said first heat exchange portion 9A of the first heat exchanger 9A Is supposed to adjust.

A second heat medium flow control mechanism 20 is provided in the second heat exchange unit 9B of the reheater 9. The second heat medium flow control mechanism 20 is provided with a second heat medium flow control valve 21 in the second heat medium introduction line 13, and the flow rate of the second heat medium introduced to the second heat exchange unit 9B is It is configured to be adjusted by the dual heat medium flow control valve 21. The second heat medium flow control valve 21 may use an adjustable orifice. Further, wherein the exhaust gas line 2 exit side of the reheater 9, the exhaust gas temperature sensor 22 is provided, said detecting the exit-side exhaust gas temperature T ₂ by the exhaust gas temperature sensor 22 second heat medium flow rate control valve An opening adjustment signal 23 is output to 21. In the exhaust gas temperature sensor 22, a set temperature T _S2 (for example, about 90 to 93 ° C.) which can suppress the generation of white smoke from the chimney 10 is stored in advance. Thus, the second heat medium flow rate control mechanism 20, so as to adjust the flow rate of the second heat medium introduced into the reheater 9 of exit side based on the exhaust gas temperature T ₂ the second heat exchanger 9B It has become.

  Next, the operation of the above embodiment will be described.

  The exhaust gas generated by burning a fuel such as coal in the boiler 1 preheats the combustion air introduced to the boiler 1 in the air preheater 3 and then the heat is recovered by the heat medium in the heat recovery unit 4 Be done.

  The dust contained in the exhaust gas that has passed through the heat recovery unit 4 is collected by the electrostatic precipitator 5, and the exhaust gas from which the dust is collected by the electrostatic precipitator 5 is pressurized by the induction ventilator 6. It is sent to absorber 8.

  In the absorption tower 8 of the desulfurization apparatus 7, the exhaust gas fed from the induction ventilator 6 comes in contact with the absorbing liquid, and the sulfur oxides contained in the exhaust gas are removed.

  The exhaust gas from which sulfur oxides have been removed by the absorption tower 8 of the desulfurization device 7 is led to a reheater 9.

In the first heat exchanger 9A and the second heat exchanging portion 9B of the reheater 9, wherein at the exhaust gas is heated, this time, the exit-side exhaust gas temperature T ₂ of the reheater 9 by the exhaust gas temperature sensor 22 together is detected, the delivery side first heat medium temperature T ₁ of the first heat medium temperature sensor 18 is detected.

The first heat medium flow control mechanism 15 controls the first heat medium temperature T ₁ on the outgoing side to a set temperature T _S1 (eg, about 70 ° C.) at which corrosion by acid does not occur inside the reheater 9. Be done. More specifically, the first heat medium flow rate control valve 17a from the basis of the detected output side first heat medium temperature T ₁ of the first heat medium temperature sensor 18, the opening degree adjustment signal 19a to 17b, 19b are output, the The opening degree of the first heat medium flow control valves 17a and 17b is adjusted. Accordingly, since the output-side first heat medium temperature T ₁ is not lower than the set temperature T _S1, not corroded by acid within the reheater 9 is generated, also, the exit-side first heat medium temperatures T _{1 Does} not exceed the set temperature _TS1 more than necessary. Incidentally, the set temperature T _S1 of the outgoing side first heat medium for corrosion by internal acid of the reheater 9 is prevented from occurring, a high the material of the internal components of the reheater 9 anticorrosive By doing this, it is also possible to keep it lower.

Meanwhile, the exit-side exhaust gas temperature T ₂ is the set temperature T _S2 can be suppressed white smoke generation from the stack 10 _(e.g., about 90 to 93 ° C.) and so as, is controlled by the second heat medium flow control mechanism 20 . More specifically, the opening degree adjustment signal 23 from the exhaust gas temperature sensor 22 based on the detected output side exhaust gas temperature T ₂ to the second heat medium flow rate regulating valve 21 is output, the opening degree of the second heat medium flow rate control valve 21 Is adjusted. As a result, only the amount of heat deficient in the first heat exchange section 9A is compensated by the second heat exchange section 9B, and waste of the second heat medium, that is, steam is minimized, and the temperature of the exhaust gas on the output side since T ₂ is not lower than the set temperature T _S2, white smoke is prevented from being generated from the stack 10.

As a result, in the present embodiment, since the temperature control is individually performed in the first heat exchange unit 9A and the second heat exchange unit 9B, unlike the one disclosed in Patent Document 1, the heat medium is heated by steam. heat medium heater without the need to, if you try to hold the output-side exhaust gas temperature T ₂ of the reheater 9 above the set temperature T _S2, the influence to the first heat medium temperature of the first heat exchanger 9A is spanned Absent. That is, the reheater outlet side first heat medium temperature T ₁ of the 9 does not rise more than necessary, the set temperature T _{S1 (e.g.,} about 70 ° C.) is avoided that exceeds.

Moreover, it never rises to the reheater 9 exit side exhaust gas temperature T ₂ a more than necessary exit side first heat medium temperature T ₁ of the reheater 9 to hold more than the set temperature T _S2 of That means that there is no concern that the temperature of the heat transfer medium introduced into the heat recovery unit 4 paired with the reheater 9 will be high. That the temperature of the heat medium entering the heat recovery unit 4 can be kept low and not high means that the logarithmic mean temperature difference (LMTD) of the heat recovery unit 4 becomes large, so heat exchange performance is improved. It does not decline. If the heat recovery performance does not decrease, the heat required for the reheater 9 can be recovered by the heat recovery unit 4, and the flow rate of the second heat medium (steam) used in the second heat exchange unit 9B is suppressed to the reheater outlet side first heat medium temperature T ₁ of the 9 it is avoided as falling into a vicious circle with increased further.

  Thus, the heat exchange performance deterioration of the heat recovery unit 4 paired with the reheater 9 can be suppressed, and the consumption of the second heat medium (steam) can be reduced.

Further, in the case of the present embodiment, the first heat medium flow rate adjusting mechanism 15 is configured to lead the first heat medium introduction line 11 to the first heat exchange unit 9A and the first heat medium delivery from the first heat exchange unit 9A. A bypass line 16 connecting to the line 12 and first heat medium flow control valves 17 a and 17 b for adjusting the flow rate of the first heat medium diverted to the bypass line 16 are provided. According to this structure, the first heat medium flow control valve 17a, the opening adjustment of 17b to adjust the flow rate of the first heat medium bypasses to the bypass line 16, sets the output-side first heat medium temperature T ₁ of the temperature It is preferable to hold it at T _S1 to prevent the occurrence of acid corrosion inside the reheater 9.

Further, the first heat medium flow rate control mechanism 15, the outputs the detecting the exit-side first heat medium temperature T ₁ of the first heat medium flow control valve 17a, the opening degree adjustment signal 19a to 17b, and 19b One heat medium temperature sensor 18 is provided. According to this structure, on the basis of the exit-side first heat medium temperatures T ₁ detected by the first heat medium temperature sensor 18 first heat medium flow control valve 17a, the opening degree adjustment signal 19a to 17b, and outputs the 19b It is effective in improving the accuracy of temperature control.

The second heat medium flow control mechanism 20 also includes a second heat medium flow control valve 21 for adjusting the flow rate of the second heat medium introduced to the second heat exchange unit 9B, and the outlet exhaust gas temperature T _2. And an exhaust gas temperature sensor 22 for outputting an opening degree adjustment signal 23 to the second heat medium flow rate adjustment valve 21. With this configuration, it is possible to output a degree of opening adjustment signal 23 to the second heat medium flow rate control valve 21 based on the delivery side exhaust gas temperature T ₂ detected by the exhaust gas temperature sensor 22, an outgoing-side exhaust gas temperature T ₂ It is preferable in order to keep the temperature not lower than the set temperature _TS2 and to prevent white smoke from being generated from the chimney 10.

  Furthermore, the first heat medium is water, and the second heat medium is steam generated by the boiler 1. This configuration is effective in performing temperature control individually in the first heat exchange unit 9A and the second heat exchange unit 9B.

  The temperature control device for a boiler exhaust gas heat exchanger according to the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the scope of the present invention. .

Reference Signs List 1 boiler 4 heat recovery unit 9 reheater 9A first heat exchange unit 9B second heat exchange unit 11 first heat medium introduction line 12 first heat medium lead line 15 first heat medium flow control mechanism 16 bypass line 17a first Heat medium flow control valve 17b First heat medium flow control valve 18 First heat medium temperature sensor 19a Opening degree control signal 19b Opening degree control signal 20 Second heat medium flow control mechanism 21 Second heat medium flow control valve 22 Exhaust gas temperature sensor 23 Opening adjustment signal T ₁ Outgoing first heat medium temperature T ₂ Outgoing exhaust gas temperature

Claims (5)

A heat recovery unit for recovering heat of exhaust gas discharged from the boiler by a heat medium;
A temperature controller for a boiler exhaust gas heat exchanger, comprising: a reheater reheating the exhaust gas with a heat medium in which the heat of the exhaust gas is recovered by the heat recovery unit;
The reheater includes a first heat exchange unit that reheats the exhaust gas with a first heat medium, and a second heat exchange unit that reheats the exhaust gas with a second heat medium that is hotter than the first heat medium.
A first heat medium flow control mechanism for adjusting the flow rate of the first heat medium introduced into the first heat exchange section based on the temperature of the first heat medium output side of the first heat exchange section;
A second heat medium flow control mechanism for adjusting the flow rate of the second heat medium introduced into the second heat exchange unit based on the outlet side exhaust gas temperature of the reheater; temperature control of the boiler exhaust gas heat exchanger apparatus. The first heat medium flow control mechanism
A bypass line connecting a first heat medium introduction line to the first heat exchange section and a first heat medium lead line from the first heat exchange section;
The temperature control device for a boiler exhaust gas heat exchanger according to claim 1, further comprising: a first heat medium flow control valve for adjusting a flow rate of the first heat medium diverted to the bypass line. The first heat medium flow control mechanism
The temperature of the heat exchanger for a boiler exhaust gas according to claim 2, further comprising: a first heat medium temperature sensor that detects the temperature of the first heat medium on the output side and outputs an opening adjustment signal to the first heat medium flow control valve. Control device. The second heat medium flow control mechanism is
A second heat medium flow control valve for adjusting the flow rate of the second heat medium introduced into the second heat exchange unit;
The heat exchange system for boiler exhaust gas according to any one of claims 1 to 3, further comprising: an exhaust gas temperature sensor that detects the outlet side exhaust gas temperature and outputs an opening adjustment signal to the second heat medium flow control valve. Controller temperature controller.   The temperature control device for a boiler exhaust gas heat exchanger according to any one of claims 1 to 4, wherein the first heat medium is water, and the second heat medium is steam generated by the boiler.

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