JP2011094901A - Gas-gas heater and control method of the gas-gas heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas-gas heater capable of prohibiting corrosion of a finned heat transfer pipe of a reheater, and a control method of the gas-gas heater. <P>SOLUTION: The gas-gas heater includes: a heat recovery device 10 recovering heat of exhaust gas from a boiler 1 by coming into contact with a heat transfer pipe 11 in which a heating medium is made to flow; the reheater 20 having a preheating part 20A preheating exhaust gas passed through the heat recovery device 10 by making the exhaust gas come into contact with a heat transfer uncovered pipe 21 in which the heating medium from the heat recovery device 10 is made to flow and a heating part 20B heating exhaust gas passed through the preheating part 20A by making the exhaust gas come into contact with the finned heat transfer pipe 22 in which the heating medium is made to flow; a heating medium heating heater 32 heating a heating medium made to flow in a high temperature communication pipe 30; a heating medium outflow temperature sensor 42 detecting a heating medium outflow temperature TE<SB>2</SB>from the finned heat transfer pipe 22; and a steam control part 45 controlling a heating medium inflow temperature TE<SB>1</SB>of the heating medium made to flow in to the heat transfer uncovered pipe 21 so that a gas inlet/outlet temperature difference ΔT between a preheating part outlet temperature and a preheating part inlet temperature of exhaust gas exceeds a predetermined temperature and the heating medium outflow temperature TE<SB>2</SB>exceeds a predetermined temperature. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gas gas heater used in a treatment facility for exhaust gas discharged from a combustion engine such as a boiler, and a method for controlling the gas gas heater.

Conventionally, as the gas gas heater described above, for example, there is one described in Patent Document 1.
The gas gas heater includes a heat recovery unit installed on the upstream side of the exhaust gas passage of the boiler, and a reheater installed on the downstream side of the wet desulfurization apparatus that constitutes the exhaust gas treatment facility provided on the exhaust gas passage. Each of the heat recovery unit and the reheater includes a heat transfer tube through which a heat medium such as water flows.

  The heat transfer tubes of the heat recovery device and the reheater are connected to each other by a communication tube, and the heat medium is circulated between the heat recovery device and the reheater via these communication tubes. That is, in this gas gas heater, the heat medium recovered from the exhaust gas by the heat recovery device is sent to the reheater via the connecting pipe, and the mist discharged from the wet desulfurization device in this reheater. By reheating the exhaust gas in a substantially saturated state containing a heat-recovered heat medium, the exhaust gas is prevented from being released into the atmosphere as white smoke.

  In this gas gas heater, the heat transfer tube on the gas inlet side of the reheater is composed of a bare tube without fins, and the central gas outlet side is composed of a heat transfer tube with fins. When almost saturated exhaust gas containing mist discharged from the gas flows into the reheater, the exhaust gas containing this mist is preheated by a bare pipe without fins on the gas inlet side and dried in the gas outlet from the center. Since it passes through the region of the finned heat transfer tube, it is avoided that dust or the like adheres to and accumulates on the finned heat transfer tube.

Patent No. 3783417

  In the conventional gas gas heater described above, a bare pipe without fins is arranged by controlling the temperature of the heating medium on the gas outlet side of the reheater to be a predetermined temperature (for example, 65 to 75 ° C.) or more. The preheating performance of the exhaust gas at the gas inlet side of the reheater is maintained. For that reason, depending on the difference in the properties of the exhaust gas, even if the temperature of the heat medium on the gas outlet side is kept above the predetermined temperature, the preheating performance may be lower than the design value. The exhaust gas that has not been completely dried on the gas inlet side of the reheater passes through the finned heat transfer tube region, so that dust or the like may be deposited on the finned heat transfer tube. It has been a conventional problem to solve this problem.

  The present invention has been made paying attention to the above-described conventional problems, and prevents dust and the like from adhering and accumulating on the finned heat transfer tube of the reheater, and as a result, prevents the finned heat transfer tube from corroding. It is an object of the present invention to provide a gas gas heater and a gas gas heater control method that can be used.

  A control method for a gas gas heater according to the present invention is located upstream of an exhaust gas passage of a combustion engine, and recovers the heat of the exhaust gas through contact between the exhaust gas discharged from the combustion engine and a heat transfer pipe through which a heat medium flows. The heat recovery unit is located on the downstream side of the exhaust gas passage of the combustion engine, and is in contact with the exhaust gas that has passed through the heat recovery unit and the heat transfer bare tube through which the heat recovery heat medium from the heat recovery unit flows. A reheater having a preheating part for preheating the exhaust gas, and a heating part for heating the exhaust gas by contact between the exhaust gas that has passed through the preheating part and the finned heat transfer tube through which the heat transfer medium from the heat transfer bare tube flows. A gas gas heater control method comprising: a gas heating / discharging temperature difference between a preheating part outlet temperature and a preheating part inlet temperature of exhaust gas passing through the reheater is set to a predetermined temperature or more, and a fin of the heating part Of the heat medium flowing out of the attached heat transfer tube In order to make the outflow temperature equal to or higher than a predetermined temperature, the temperature of the heat medium flowing into the heat transfer bare tube of the preheating portion in the reheater is controlled, and the control of the gas gas heater of this configuration The method is a means for solving the above-described conventional problems.

  According to a second aspect of the present invention, there is provided a method for controlling a gas gas heater, wherein when the gas inlet / outlet temperature difference is equal to or higher than a predetermined temperature and the heat medium outlet temperature is equal to or higher than a predetermined temperature, preheating in the reheater is performed. When the heat medium inflow temperature flowing into the heat transfer bare pipe of the section is maintained, and any one of the gas inlet / outlet temperature difference and the heat medium outflow temperature is less than a predetermined temperature, in the reheater The inflow temperature of the heat medium flowing into the heat transfer bare pipe of the preheating unit is increased.

  Furthermore, the gas gas heater control method according to claim 3 of the present invention measures the inflow temperature of the heat medium flowing into the heat transfer bare tube of the preheating section in the reheater, and the inflow temperature of the heat medium is calculated in advance. When the heating medium outflow temperature is equal to or higher than a predetermined temperature for maintaining the heating performance of the preheating unit, the heat medium inflow temperature is maintained, and the heat medium inflow temperature is maintained. When either one of the heat medium outflow temperatures does not reach a predetermined temperature, the inflow temperature of the heat medium is increased. Note that the predetermined temperature for maintaining the heating performance of the preheating unit calculated in advance is, for example, a temperature calculated based on experience and the scale of the plant when designing the gas gas heater.

  Furthermore, the control method of the gas gas heater according to claim 4 of the present invention measures the inflow temperature of the heat medium flowing into the heat transfer bare pipe of the preheating unit in the reheater, and also measures the preheating unit in the reheater. The heat transfer temperature of the heating medium flowing between the heat transfer bare pipe of the heating section and the finned heat transfer pipe of the heating unit is measured, and heating calculated based on the difference between the inflow temperature of the heating medium and the circulation temperature of the heating medium When the amount keeps the gas inlet / outlet temperature difference equal to or higher than the predetermined temperature and the heat medium outflow temperature is higher than the predetermined temperature, the inflow temperature of the heat medium is maintained, and the heating amount reduces the gas inlet / outlet temperature difference. When the temperature cannot be kept higher than a predetermined temperature, or when the outflow temperature of the heat medium is less than the predetermined temperature, the inflow temperature of the heat medium is increased.

  On the other hand, the gas gas heater according to the present invention is located on the upstream side of the exhaust gas passage of the combustion engine, and recovers the heat of the exhaust gas through contact between the exhaust gas discharged from the combustion engine and the heat transfer pipe through which the heat medium flows. Heat transfer that is located downstream of the recovery unit and the exhaust gas passage of the combustion engine and through which the exhaust gas that has passed through the heat recovery unit and the heat recovery heat medium that is supplied from the heat recovery unit via a pipe flows A preheating section that preheats the exhaust gas by contact with the bare pipe, and heating that heats the exhaust gas by contact between the exhaust gas that has passed through the preheating section and the finned heat transfer pipe through which the heat transfer medium from the heat transfer bare pipe flows. A reheater having a heating part, a heating medium heater that heats the heating medium that is installed on the pipe and flows through the pipe, and detects the heat medium outlet temperature of the heating medium that flows out from the finned heat transfer tube of the heating part Heat medium outflow temperature detecting means for passing through the reheater The gas inlet / outlet temperature difference between the preheating part outlet temperature and the preheating part inlet temperature of the exhaust gas is set to a predetermined temperature or more, and the heating medium outflow temperature detected by the heating medium outflow temperature detecting means is set to a predetermined temperature or more. Therefore, the heat medium heater is operated and the heat medium temperature control means for controlling the heat medium inflow temperature of the heat medium flowing into the heat transfer bare tube of the preheating part in the reheater is provided. The gas gas heater having this configuration is a means for solving the above-described conventional problems.

  In the gas gas heater and the gas gas heater control method according to the present invention, when the difference between the gas outlet temperature and the gas inlet temperature in the preheating part of the reheater is small, that is, the rising temperature of the exhaust gas in the preheating part is preset. Heat medium inflow into the heat transfer bare tube when the temperature does not reach the specified temperature (design value) or when the heat medium outflow temperature of the heat transfer medium flowing out from the finned heat transfer tube is less than the predetermined temperature As the temperature is raised, when exhaust gas in a nearly saturated state containing mist flows into the reheater, the exhaust gas containing mist is sufficiently preheated by the heat transfer bare tube of the preheating part and dried. In this state, it passes through the heating part of the reheater.

  As a result, it is possible to prevent dust and the like from adhering and accumulating on the finned heat transfer tube disposed in the heating section of the reheater, and to prevent the finned heat transfer tube from corroding.

  In the gas gas heater and the method for controlling the gas gas heater according to the present invention, since the above-described configuration is adopted, dust and the like can be prevented from adhering to and deposited on the finned heat transfer tube of the reheater. A very good effect is obtained that it is possible to prevent corrosion of the heat transfer tubes.

It is schematic structure explanatory drawing of the gas gas heater which concerns on one Example of this invention. It is a flowchart which shows one control routine by the vapor | steam control part of the gas gas heater in FIG. It is a flowchart which shows the other control routine by the vapor | steam control part of the gas gas heater in FIG. 7 is a flowchart showing still another control routine by the steam control unit of the gas gas heater in FIG. 1.

Hereinafter, the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of a gas gas heater according to the present invention. In this embodiment, a case where the gas gas heater according to the present invention is employed in an exhaust gas treatment facility will be described as an example.

  As shown in FIG. 1, the gas gas heater is located on an exhaust gas passage 2 of a boiler 1 that is a combustion engine, and a heat recovery device 10 disposed on the upstream side of the exhaust gas passage 2 and an exhaust gas passage 2. A reheater 20 is provided on the downstream side.

  Between the boiler 1 and the heat recovery unit 10 in the exhaust gas passage 2, a denitration device and an air preheater (both not shown) constituting the exhaust gas treatment facility are arranged along the flow of the exhaust gas. Between the heat recovery unit 10 and the reheater 20, an electric dust collector 3, an incentive fan 4 and a wet desulfurization device 5 that also constitute an exhaust gas treatment facility are arranged along the flow of the exhaust gas. A desulfurization fan and a chimney 6 (not shown) are disposed on the downstream side.

  The heat recovery device 10 includes a heat transfer tube 11 through which a heat medium flows. On the other hand, the reheater 20 has an exhaust gas inflow side (left side in the figure) as a preheating part 20A, and an exhaust gas outflow side (right side in the figure) as a heating part 20B. A tube 21 is disposed, and a finned heat transfer tube 22 that is continuous with the heat transfer bare tube 21 is disposed in the heating unit 20B.

  One end of the heat transfer tube 11 in the heat recovery device 10 and the end portion of the heat transfer bare tube 21 in the reheater 20 are connected to the exhaust gas inflow side end by a high-temperature communication tube (pipe) 30 through which a heat-recovered heat medium flows. The other end of the heat transfer tube 11 in the recovery unit 10 and the finned heat transfer tube 22 in the reheater 20 are connected by a low-temperature communication tube 31 to form a circulation path of the heat medium. In this case, by connecting the exhaust gas outflow side end of the heat transfer bare tube 21 in the reheater 20 to the exhaust gas outflow side end of the finned heat transfer tube 22, the heating medium from the heat transfer bare tube 21 in the heating unit 20B. Is flowed from the exhaust gas outflow side of the finned heat transfer tube 22 to the exhaust gas inflow side, and the low temperature communication tube 31 is connected to the exhaust gas inflow side end of the finned heat transfer tube 22 through which the heat medium flows out.

In this gas gas heater, in the heat recovery device 10, the temperature of the exhaust gas is lowered to 80 to 100 ° C. by bringing the heat transfer tube 11 through which the heat medium flows into contact with the 110 to 140 ° C. exhaust gas discharged from the boiler 1. It has become.
On the other hand, in the preheating part 20A of the reheater 20, it passes through the heat transfer bare pipe 21 through which the heat-recovered heat medium fed through the high temperature communication pipe 30 circulates and the wet desulfurization apparatus 5 to 45 to 55. This exhaust gas is preheated by bringing it into contact with the exhaust gas having a low temperature of 0 ° C., and in the heating unit 20B, the finned heat transfer tube 22 through which the heat medium from the heat transfer bare tube 21 circulates and the exhaust gas that has passed through the preheating unit 20A The exhaust gas is heated to 80 to 100 ° C.

  In this case, a heat medium heater 32 is provided on the high temperature communication tube 30. This heat medium heater 32 is installed in the middle of the steam pipe 33 through which the steam from the boiler 1 flows, and by heat exchange between the steam flowing through the steam pipe 33 and the heat medium flowing through the high temperature communication pipe 30, The heating medium is heated. The steam pipe 33 is provided with a steam valve 34 that controls the temperature of the heat medium by changing the flow rate of the steam to the heat medium heater 32. A circulation pump 35 for circulating the heat medium is provided on the low temperature communication pipe 31.

  In addition, a heat medium inflow temperature sensor 41 for detecting the heat medium inflow temperature of the heat medium flowing into the heat transfer bare pipe 21 of the preheating unit 20A is provided near the entrance of the preheating unit 20A in the reheater 20 of the high temperature communication tube 30. A heat medium outflow temperature sensor 42 for detecting the heat medium outflow temperature of the heat medium flowing out from the finned heat transfer tube 22 of the heating unit 20B is provided in the vicinity of the reheater 20 of the low temperature communication tube 31. ing.

Further, the reheater 20 is provided with a heat medium flow temperature sensor 43 for detecting the flow temperature of the heat medium flowing between the heat transfer bare tube 21 of the preheating unit 20A and the finned heat transfer tube 22 of the heating unit 20B. It has been.
Furthermore, the reheater 20 includes a preheating part outlet temperature sensor 44r and a preheating part inlet temperature in order to measure the gas inlet / outlet temperature difference between the preheating part outlet temperature and the preheating part inlet temperature of the exhaust gas passing through the preheating part 20A. Each sensor 44f is provided.

The heating medium inflow temperature sensor 41, the heating medium outflow temperature sensor 42, the heating medium circulation temperature sensor 43, the preheating unit outlet temperature sensor 44r, and the preheating unit inlet temperature sensor 44f are all electrically connected to the steam control unit 45. Has been. The steam control unit 45 is also electrically connected to the steam valve 34, and the heat medium inflow temperature TE ₁ detected by the heat medium inflow temperature sensor 41 and the heat detected by the heat medium outflow temperature sensor 42. Steam valve based on the medium outflow temperature TE ₂ , the heat medium circulation temperature TE ₃ detected by the heat medium circulation temperature sensor 43, the gas inlet / outlet temperature difference ΔT measured by the preheating part outlet temperature sensor 44 r and the preheating part inlet temperature sensor 44 f The valve opening of 34 is controlled.
In addition, the code | symbol 46 in FIG. 1 is a heat-medium cooler.

Next, one control method of the gas gas heater having such a configuration, that is, one control routine of the above-described steam control unit 45 will be described based on the flowchart of FIG.
In this embodiment, the steam control unit 45 controls to normally close the steam valve 34.

  First, in step S1, the preheating part outlet temperature and the preheating part inlet temperature of the exhaust gas passing through the preheating part 20A of the reheater 20 are measured by the preheating part outlet temperature sensor 44r and the preheating part inlet temperature sensor 44f, respectively, and the gas in and out is measured. A temperature difference ΔT is acquired.

  In step S2, it is determined whether or not the gas inlet / outlet temperature difference ΔT is equal to or higher than a predetermined temperature (for example, 3 to 5 ° C.), and the gas inlet / outlet temperature difference ΔT is equal to or higher than a predetermined temperature ( If yes, the process proceeds to the next step S3.

In step S < _b > 3, the heat medium outflow temperature TE < _b > ₂ of the heat medium flowing out from the finned heat transfer tube 22 of the heating unit 20 </ _b > B of the reheater 20 is acquired by the heat medium outflow temperature sensor 42.

Subsequently, in step S4, the heating medium outlet temperature TE _2, it is determined whether or not at least a predetermined temperature which is set in advance (for example, 65 to 75 ° C.), the heat medium outlet temperature TE ₂ is given If the temperature is equal to or higher than the temperature (Yes), the process proceeds to the next step S5.

  In step S5, the control of the steam valve 34 at the normal time is maintained, that is, the steam valve 34 is kept closed, and the routine returns.

On the other hand, if the determination result in step S2 or step S4 is negative (No), i.e., when one of the gas inflow and outflow temperature difference ΔT and the heat medium outlet temperature TE ₂ is less than a predetermined temperature proceeds to step S6, and in step S6, by opening the steam valve 34, to raise the inlet temperature TE ₁ of the heating medium flowing into the heat transfer bare tube 21 of the preheating section 20A in the reheater 20 (e.g. The routine is returned.

Thus, when the gas inlet / outlet temperature difference ΔT in the preheating unit 20A is small, that is, when the rising temperature of the preheating unit 20A is less than a predetermined temperature (design value) set in advance, or from the finned heat transfer tube 22 when the heat medium outflow and the temperature TE ₂ of the heat medium flowing out is less than the predetermined temperature, the steam control unit 45 controls to open the steam valve 34.

Thus, heating of the heat medium is performed by a heat medium heater 32, the heat medium inlet temperature TE ₁ of the heating medium flowing into the heat transfer bare pipe 21 is increased, the mist discharged from the wet desulfurization system 5 When the contained exhaust gas flows into the reheater 20 in a substantially saturated state, the exhaust gas containing mist is sufficiently preheated by the heat transfer bare tube 21 of the preheating portion 20A and dried in the heated portion of the reheater 20 It will pass 20B.
As a result, it is possible to prevent soot and dust such as gypsum from adhering and accumulating on the finned heat transfer tube 22 disposed in the heating section 20B of the reheater 20, and to prevent the occurrence of corrosion in the finned heat transfer tube 22. It becomes.

Next, another control routine of the steam control unit 45 described above will be described with reference to the flowchart of FIG.
Also in this case, the steam control unit 45 performs control so that the normal steam valve 34 is closed.

This control routine, first, in step S11, the heat medium inlet temperature TE ₁ of the heating medium flowing into the heat transfer bare tube 21 of the preheat portion 20A of the reheater 20 is obtained by heating medium inlet temperature sensor 41.

Then, in step S12, it is determined whether or not the heating medium inlet temperature TE ₁ is the predetermined temperature Tm or more for maintaining the heating performance of the pre-calculated preheating section 20A, the heat medium inlet temperature TE ₁ Is equal to or higher than a predetermined temperature Tm (Yes), the process proceeds to step S5 through steps S3 and S4 in the same manner as in the previous control routine, and in this step S5, control of the steam valve 34 at normal time is maintained. That is, the steam valve 34 is kept closed and the routine returns.

On the other hand, if the judgment result at Step S12 or Step S4 is negative (No), i.e., if any of the heating medium inlet temperature TE ₁ and the heat medium outlet temperature TE ₂ is less than a predetermined temperature In the same manner as in the previous control routine, the process proceeds to step S6. In this step S6, the steam valve 34 is opened, so that the inflow temperature of the heat medium flowing into the heat transfer bare pipe 21 of the preheating unit 20A in the reheater 20 is reached. Is raised and the routine returns.

Thus, Ya if less than the predetermined temperature Tm to keep the heating performance of the preheating section 20A of the heat medium inlet temperature TE ₁ of the heating medium flowing into the heat transfer bare tube 21 is calculated in advance of the pre-heating section 20A in the case where the heat medium outflow and the temperature TE ₂ of the heat medium flowing out of the finned heat transfer tubes 22 of the heating unit 20B is lower than the predetermined temperature, the steam control unit 45 controls to open the steam valve 34.

Accordingly, the heat medium inlet temperature TE ₁ of the heating medium flowing into the heat transfer naked pipe 21 by the heat medium heater 32 is operated increases, a substantially saturated conditions including mist flowed into the reheater 20 the exhaust gas Is sufficiently preheated by the heat transfer bare tube 21 of the preheating unit 20A and passes through the heating unit 20B of the reheater 20 in a dry state, so that dust such as gypsum is put on the finned heat transfer tube 22 of the heating unit 20B. It is possible to prevent adhesion and deposition and prevent the finned heat transfer tube 22 from corroding.

Next, still another control routine of the steam control unit 45 described above will be described with reference to the flowchart of FIG.
Also in this case, the steam control unit 45 performs control so that the normal steam valve 34 is closed.

In this control routine, first, in step S21, with the heat medium inlet temperature TE ₁ of the heating medium flowing into the heat transfer bare tube 21 of the preheat portion 20A of the reheater 20 is obtained by heating medium inlet temperature sensor 41, the preheating the heat medium flow temperature TE ₃ of the heat medium flowing between the heat transfer bare tubes 21 parts 20A and finned heat transfer tubes 22 of the heating unit 20B obtains at heat transfer medium flow temperature sensor 43.

Then, in step S22, to calculate the heat quantity Q based on the difference between the heating medium inlet temperature TE ₁ and the heat medium flow temperature TE ₃ mentioned above acquired Subsequently, in step S23, the heating amount Q is the gas inflow and outflow temperature It is determined whether or not the difference ΔT is kept above a predetermined temperature.

  In this step S23, when the heating amount Q keeps the gas inlet / outlet temperature difference ΔT equal to or higher than the predetermined temperature (Yes), the process proceeds to step S5 through steps S3 and S4 in the same manner as in the previous control routine, and this step S5. The control of the steam valve 34 during normal operation is maintained, that is, the steam valve 34 is kept closed, and the routine returns.

On the other hand, if the determination result in step S23 or step S4 is NO (No), that is, the heating amount Q cannot maintain the gas inlet / outlet temperature difference ΔT above a predetermined temperature, or the heat medium outlet temperature TE. _{If 2} does not reach the predetermined temperature, the process proceeds to step S6 as in the previous control routine, and in this step S6, the steam valve 34 is opened, so that the heat transfer bare tube of the preheating unit 20A in the reheater 20 is opened. The inflow temperature of the heat medium flowing into 21 is increased, and the routine is returned.

Thus, and if the heating amount Q calculated based on the difference between the heating medium inlet temperature TE ₁ and the heat medium flow temperature TE ₃ can not be maintained the gas inflow and outflow temperature difference ΔT than the predetermined temperature, Den finned in the case where the heat medium outflow and the temperature TE ₂ of the heat medium flowing out of the heat pipe 22 is lower than the predetermined temperature, the steam control unit 45 controls to open the steam valve 34.

Thus, the heat medium inlet temperature TE ₁ of the heating medium flowing into the heat transfer bare pipe 21 is increased, exhaust gas containing mist flowed into the reheater 20 is allowed to dry by heat transfer bare tube 21 of the preheating section 20A Therefore, it is possible to prevent corrosion of the finned heat transfer tube 22 with almost no dust such as gypsum adhering and depositing on the finned heat transfer tube 22 of the heating unit 20B. It becomes.

The configuration of the gas gas heater and the control method thereof according to the present invention is not limited to the configuration of the above-described embodiment.
In addition, the specific numerical values of the exhaust gas temperature, the heat medium inflow temperature TE ₁ , the heat medium outflow temperature TE ₂ , the heat medium circulation temperature TE _3, and the gas inlet / outlet temperature difference ΔT in each part of the above embodiment are the values described above. It is not limited to.

1 Boiler (combustion engine)
2 Exhaust gas passage 10 Heat recovery device 11 Heat transfer tube 20 Reheater 20A Preheating portion 20B Heating portion 21 Heat transfer bare tube 22 Heat transfer tube 30 with fins High temperature communication tube (pipe)
32 Heat medium heater 42 Heat medium outflow temperature sensor (heat medium outflow temperature detection means)
45 Steam control unit (heat medium temperature control means)
TE ₁ Heat-medium inflow temperature TE ₂ Heat-medium outflow temperature TE ₃ Heat-medium distribution temperature Tm Predetermined temperature ΔT for maintaining the heating performance of the preheating part ΔT between the preheating part outlet temperature and the preheating part inlet temperature of the exhaust gas Gas inlet / outlet temperature difference

Claims (5)

A heat recovery unit that is located upstream of the exhaust gas passage of the combustion engine and recovers the heat of the exhaust gas by contact with the exhaust gas discharged from the combustion engine and a heat transfer tube through which a heat medium flows;
The exhaust gas is preheated by contact between the exhaust gas that has passed through the heat recovery unit and the heat transfer bare pipe through which the heat medium that has recovered heat from the heat recovery unit is located on the downstream side of the exhaust gas passage of the combustion engine. Gas gas heater comprising a preheater, and a reheater having a heating unit that heats the exhaust gas by contact between the exhaust gas that has passed through the preheater and the finned heat transfer tube through which the heat transfer medium from the heat transfer bare tube flows Control method,
The heat medium outflow of the heat medium flowing out from the finned heat transfer tube of the heating unit while the gas inlet / outlet temperature difference between the preheating unit outlet temperature and the preheating unit inlet temperature of the exhaust gas passing through the reheater is equal to or higher than a predetermined temperature A method for controlling a gas gas heater, characterized by controlling an inflow temperature of a heat medium flowing into a heat transfer bare tube of a preheating section in the reheater so that the temperature is equal to or higher than a predetermined temperature.   When the gas inlet / outlet temperature difference is equal to or higher than a predetermined temperature and the heat medium outlet temperature is equal to or higher than a predetermined temperature, the inflow temperature of the heat medium flowing into the heat transfer bare pipe of the preheating portion in the reheater is maintained. When any of the gas inlet / outlet temperature difference and the heat medium outflow temperature is less than a predetermined temperature, the inflow temperature of the heat medium flowing into the heat transfer bare pipe of the preheating unit in the reheater is increased. The method for controlling a gas gas heater according to claim 1.   The inflow temperature of the heating medium flowing into the heat transfer bare tube of the preheating unit in the reheater is measured, and the inflow temperature of the heating medium is equal to or higher than a predetermined temperature for maintaining the heating performance of the preheating unit calculated in advance. When the heat medium outflow temperature is equal to or higher than a predetermined temperature, the heat medium inflow temperature is maintained, and either the heat medium inflow temperature or the heat medium outflow temperature satisfies the predetermined temperature. The method for controlling a gas gas heater according to claim 1, wherein if not, the inflow temperature of the heat medium is increased.   While measuring the inflow temperature of the heat medium flowing into the heat transfer bare tube of the preheating part in the reheater, between the heat transfer bare tube of the preheating part and the finned heat transfer tube of the heating part in the reheater The flow temperature of the flowing heat medium is measured, and the heating amount calculated based on the difference between the inflow temperature of the heat medium and the flow temperature of the heat medium keeps the gas inlet / outlet temperature difference equal to or higher than a predetermined temperature and the heat medium. When the outflow temperature is equal to or higher than a predetermined temperature, the heat medium inflow temperature is maintained, and the heating amount cannot maintain the gas inlet / outlet temperature difference equal to or higher than the predetermined temperature, or the heat medium outflow temperature is predetermined. The method for controlling a gas gas heater according to claim 1, wherein when the temperature of the heat medium is not reached, the inflow temperature of the heat medium is increased. A heat recovery unit that is located upstream of the exhaust gas passage of the combustion engine and recovers the heat of the exhaust gas by contact with the exhaust gas discharged from the combustion engine and a heat transfer tube through which a heat medium flows;
Located on the downstream side of the exhaust gas passage of the combustion engine, an exhaust gas that has passed through the heat recovery device and a heat transfer bare tube through which a heat-recovered heat medium fed from the heat recovery device through a pipe flows. A reheating unit that preheats the exhaust gas by contact, and a heating unit that heats the exhaust gas by contact between the exhaust gas that has passed through the preheating unit and the finned heat transfer tube through which the heat transfer medium from the heat transfer bare tube flows. A heater,
A heat medium heater installed on the pipe to heat the heat medium flowing through the pipe;
Heat medium outflow temperature detecting means for detecting the heat medium outflow temperature of the heat medium flowing out from the finned heat transfer tube of the heating unit;
The difference between the gas inlet / outlet temperature between the preheating part outlet temperature and the preheating part inlet temperature of the exhaust gas passing through the reheater is set to a predetermined temperature or more, and the heating medium outlet temperature detected by the heating medium outlet temperature detecting means A heating medium temperature control means for controlling the heating medium inflow temperature of the heating medium flowing into the heat transfer bare tube of the preheating unit in the reheater by operating the heating medium heater so as to be equal to or higher than a predetermined temperature; A gas gas heater characterized by that.

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