JP2007205187A - Heat recovery system attached to boiler-steam turbine system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat recovery system capable of increasing formed steam quantity by an exhaust gas boiler by effectively utilizing heat energy of cooling water derived from a condenser by introducing a heat pump, and performing temperature control at dew-point temperature or higher. <P>SOLUTION: When steam turbine condensation 14 is supplied to an exhaust gas boiler 3 in a heat recovery system, a system supplying condensation directly to an economizer 20 of the exhaust gas boiler 3 and a system supplying condensation after heating by the heat pump 11 are separated as former technology, and necessary water supply pipe is newly provided for that. Heat energy of condenser outlet cooling water is pumped up by the heat pump 11, a part of condensation 14 is heated to about 90°C by heat energy thereof and is mixed with rest of condensation at exhaust gas boiler 3 water supply inlet. Consequently, temperature of water supply to the exhaust gas boiler 3 is raised, and shortage of heat for increasing boiler steam quantity is compensated as a result. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat recovery system that uses hot water heat-exchanged by a heat pump as water supply for an exhaust heat recovery boiler, and more specifically, in a combined system (boiler-steam turbine system) that is one of thermal power generation facilities. The present invention relates to a heat recovery system in which steam turbine condensate is heated by a heat pump and then supplied to an exhaust heat recovery boiler.

  In a condenser for condensing the exhaust steam of a steam turbine that works with steam from a steam generator such as a boiler, the temperature of the cooling water that cools the condenser is generally as low as 30 ° C to 40 ° C. Generally, it is discharged unused. Use of a heat pump is considered as a method of effectively using this low-temperature condenser outlet cooling water.

  For example, there is a conventional technique known from Patent Document 1 in which heat is pumped from a low-temperature heat source such as condenser outlet cooling water and the heat is used.

  Patent Document 2 describes one provided with a vapor compression heat pump as feed water heating means for heating feed water to a boiler.

Patent Document 3 describes an example in which an absorption heat pump device is used.
In the conventional exhaust heat recovery boiler, in order to make the outlet exhaust gas temperature equal to or higher than the acid dew point temperature, a technique known in Patent Document 2 for preheating the feed water to the exhaust heat recovery boiler is used.

  Absorption heat pumps, as is well known in the prior art, efficiently pumps heat from a low-temperature heat source and heats the high-temperature heat source. The usage destination is limited. The cooling water for cooling the condenser is generally water from a cooling tower or seawater, and the temperature is preferably controlled to be constant. There are various control methods, and if it can be controlled to a constant temperature, it can be used as a low-temperature heat source of a heat pump. The use of fluid that has been heat-exchanged by a heat pump can contribute to energy saving because the amount of fuel used can be reduced by using the generated hot water as preheating of process steam, compared to heating with a boiler alone. Is possible.

  On the other hand, the exhaust heat recovery boiler is a conventional facility that uses the exhaust heat of the gas turbine to generate steam and supply it to the steam turbine. If the heat transfer area of the exhaust heat recovery boiler is increased, the exhaust gas recovery is achieved. The amount of heat can be increased, and the amount of generated steam can be increased. However, the exhaust gas temperature at the outlet of the exhaust heat recovery boiler must be equal to or higher than the acid dew point temperature if the exhaust gas contains sulfur, and even if it does not contain sulfur, white smoke due to moisture condensation in the exhaust gas From the viewpoint of prevention, etc., it is generally set at about 90 ° C at least.

  Conventionally, in an exhaust heat recovery boiler, the exhaust gas temperature has only to be equal to or higher than the acid dew point temperature, and heating of the feed water has not been performed for other purposes. That is, the introduction of a heat pump for heating the feed water to the exhaust heat recovery boiler has not been implemented.

  Further, in the conventional exhaust heat recovery boiler, since the lower limit value exists in the outlet exhaust gas temperature as described above, there is an upper limit in the amount of heat recovered by the exhaust heat recovery boiler. For this reason, the heat transfer area of the exhaust heat recovery boiler cannot be increased beyond a certain upper limit, and the amount of boiler steam generated has an upper limit.

Japanese Patent Laid-Open No. 6-129511 JP-A-11-173110 JP-A-5-263610 JP 2000-45713 A

  As described above, in the exhaust heat recovery boiler, the outlet exhaust gas temperature needs to be equal to or higher than the acid dew point temperature, and there is an upper limit on the amount of heat recovered by the exhaust heat recovery boiler, so there is also an upper limit on the amount of boiler steam generated. there were. Further, the condenser outlet cooling water has a low temperature, and the amount of heat it has had not been effectively used.

  The present invention, in a boiler-steam turbine system, increases the amount of steam generated by the exhaust heat recovery boiler by effectively utilizing the thermal energy of the cooling water derived from the condenser by introducing a heat pump, and the acid dew point. An object of the present invention is to provide a heat recovery system capable of controlling the temperature above the temperature.

  In the heat recovery system of the present invention, an exhaust heat recovery boiler, a steam turbine that uses steam from the exhaust heat recovery boiler, a condenser for condensing steam that has worked in the steam turbine, the condenser, and In a boiler water supply system equipped with a cooling water system for supplying heat to a plant auxiliary heat exchanger, piping for exchanging a part of the condensate with a heat pump, and condenser outlet cooling water is used as a low-temperature heat source for the heat pump. Provide piping. Heat is pumped from the condenser outlet cooling water by a heat pump, and the condensed water heated to about 90 ° C. is supplied to the exhaust heat recovery boiler. Condensate at a relatively low temperature (generally around 60 ° C) that is not heated by a heat pump is supplied directly to the exhaust heat recovery boiler economizer via the condensate pump.

  At this time, the temperature of the feed water from two different pipes varies depending on whether or not the heat pump is heated, but mixing this at the exhaust heat recovery boiler feed water inlet results in an increase in the feed water temperature to the exhaust heat recovery boiler Let

  The present invention uses a heat pump to increase the feed water temperature to the exhaust heat recovery boiler in order to increase the amount of steam generated by the boiler. The method includes a method in which the temperature of the total flow rate of the steam turbine condensate supplied to the exhaust heat recovery boiler is slightly increased, and a part of the steam turbine condensate is heated to a high temperature and mixed with the remaining water supply. In general, a method of increasing the temperature of the entire flow rate is conceivable, but the latter is more efficient from the economical and thermal energy utilization viewpoints.

  Among the steam turbine condensate, the distribution of the amount of water to be heated by the heat pump and the flow rate to supply water directly to the exhaust heat recovery boiler is based on the assumption that the exhaust heat recovery boiler recovers the gas turbine exhaust heat to the limit. It is determined from the amount of generated steam to be increased.

The present invention relates to an exhaust heat recovery boiler, a steam turbine that uses steam from the exhaust heat recovery boiler as a power source, a condenser for condensing steam that has worked in the steam turbine, and a condenser to an exhaust heat recovery boiler. In a heat recovery system attached to a boiler-steam turbine system having a condensate circulation system for circulating condensate and a cooling water supply system for supplying cooling water to the condenser,
A heat pump connected to a pipe for guiding the cooling water from the cooling water supply system, and connected to a pipe branched from the condensate circulation system via a branch valve;
A controller for controlling the temperature of the mixed boiler water introduced into the economizer by mixing the condensate heated by the heat pump with the condensate from the condensate circulation system to form boiler water; There is provided a heat recovery system attached to a boiler-steam turbine system characterized by being provided.

  According to the present invention, in the boiler-steam turbine system, by introducing the heat pump described above, the heat energy of the cooling water introduced with the condenser is effectively utilized to increase the amount of steam generated by the exhaust heat recovery boiler. In addition, it is possible to provide a heat recovery system capable of controlling the temperature above the acid dew point temperature.

A heat recovery system according to an embodiment of the present invention includes an exhaust heat recovery boiler, a steam turbine that uses steam from the exhaust heat recovery boiler as a power source, a condenser for condensing steam that has worked in the steam turbine, A heat recovery system attached to a boiler-steam turbine system having a condensate circulation system for circulating condensate from a water heater to a waste heat recovery boiler and a cooling water supply system for supplying cooling water to the condenser,
A heat pump connected to a pipe for guiding the cooling water from the cooling water supply system, and connected to a pipe branched from the condensate circulation system via a branch valve;
The condensate heated by the heat pump is mixed with the condensate from the condensate circulation system and the boiler water circulated by the boiler water circulation system of the exhaust heat recovery boiler to form boiler water. And it is comprised by providing the control apparatus which controls the temperature of the mixed boiler water introduce | transduced into the said economizer.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The heat recovery system 100 according to the present embodiment is attached to a combined cycle, that is, a boiler-steam turbine system.

  In FIG. 1, fuel is supplied to a gas turbine 1, and power is generated by a generator 2 driven by the gas turbine 1. The exhaust heat gas from the gas turbine 1 is sent to the exhaust heat recovery boiler 3 to recover thermal energy. The exhaust gas after heat exchange with the feed water in the exhaust heat recovery boiler 3 is discharged from the chimney 12 to the atmosphere. Heat is exchanged in the exhaust heat recovery boiler 3, and the generated steam is sent to the steam turbine 4 as a power source. The steam worked by the generator 5 driven by the steam turbine 4 is cooled by the condenser 6 and supplied to the exhaust heat recovery boiler 3 through the condensate pump 9. In the present embodiment, the system in the condenser 6 and the exhaust heat recovery boiler 3 is referred to as a condensate circulation system 14.

  In order to effectively recover the amount of heat recovered by the condenser 6, the heat pump 11 that efficiently pumps the heat of the low-temperature heat source, compresses it to high temperature and high pressure, and warms the high-temperature heat source is connected to the condenser outlet side and exhaust heat recovery. Installed on the boiler inlet side. That is, a three-way valve (branch valve) 10 is provided in the condensate circulation system 14, a pipe 18 branched through the three-way valve 10 is connected to the heat pump 11, and a pipe E 19 led out from the heat pump 11 is connected to the inlet side of the exhaust heat recovery boiler 3. Connect to.

  As a low-temperature heat source for the heat pump 11, condenser outlet cooling water (generally about 30 ° C. to 40 ° C.) of the condenser outlet cooling water pipe 13 that generally uses water of the cooling tower 7 or seawater (not shown) is used. As a result, the condenser outlet cooling water of the condenser outlet cooling water pipe 13 gives heat through the heat pump 11, and the pipe A15 and the pipe B16 are returned to the cooling tower 7 as drains. Provide.

  Further, when the condensate flowing through the condensate circulation system 14 is supplied to the exhaust heat recovery boiler 3, a part of the condensate is branched and heated by the amount of heat recovered by the heat pump 11. For this purpose, in addition to the water supply pipe C17 for supplying the condensate directly to the exhaust heat recovery boiler 3, the pipe D18 for newly sending the condensate as a high-temperature heat source of the heat pump, and the above-mentioned recovery A pipe E19 for supplying water to the exhaust heat recovery boiler 3 is installed.

  FIG. 2 shows an embodiment of the present invention in detail. The exhaust heat recovery boiler 3 includes a economizer 20 in a flue 40, and is provided with a boiler pipe 41 whose inlet side is connected to the condensate circulation system 14 and whose outlet side is connected to the boiler drum 22 via a water level regulator 21. . A thermometer 25 is provided on the circulating water inlet side of the economizer 20, that is, the outlet side of the exhaust gas 24, and the temperature signal can be generated by measuring the outlet side temperature of the exhaust gas.

  The temperature signal generated by the thermometer 25 is input to the control device 26.

  The control device 26 uses the temperature signal from the thermometer 25 to control the circulation amount of the boiler water using the pipe F23, that is, the control valve 31 provided in the boiler water circulation system. Further, the control device 26 controls the circulation amount of the boiler water and the branch distribution amount of the condensate by the three-way valve 10. If the boiler-steam turbine system is stabilized, the control valve 31 and the three-way valve 10 are controlled by a certain amount. A condensate thermometer 42 is provided in the condensate circulation system 14, and a temperature signal generated by the thermometer 42 is combined with a temperature signal from the thermometer 25 in the control device 26 to control the control valve 31 and the three-way valve 10. May be performed. In any case, it is important to control the temperature of the condensate at the inlet of the economizer 20 to a predetermined temperature in consideration of condensation. Here, the circulating water until it is introduced into the economizer 20 is referred to as condensate, and the exhaust heat recovery boiler 3, that is, the circulating water that flows through the economizer 20 is referred to as boiler water. Accordingly, the circulating water that is introduced into the economizer 20 and becomes boiler water is introduced outside the system of the economizer 20 through the condensate flowing through the condensate circulation system 14, the heated condensate heated by the heat pump 11, and circulating. It is formed by mixing with boiler water (part of boiler water).

  Thus, the condensate heated by the heat pump 11 is mixed with the condensate from the condensate circulation system 14 and the boiler water circulated by the boiler water circulation system of the exhaust heat recovery boiler 3 and led out of the economizer. A controller is provided that forms boiler water and controls the temperature of the mixed boiler water introduced into the economizer 20.

  The control device 26 inputs at least a temperature signal from the thermometer 25 and circulates the condensate branched from the condensate circulation system 14 or the amount of boiler water circulated by the boiler water circulation system and led out of the economizer. To control.

  Further, the control device 26 inputs a temperature signal from a condensate circulation thermometer 27 provided in the condensate circulation system 14, and is circulated by a condensate circulation amount branched from the condensate circulation system 14 or a boiler water circulation system to save coal. The amount of boiler water led out of the vessel is controlled.

  Moreover, the control apparatus 26 can perform the control of the amount of boiler water led out of the economizer prior to the control of the circulation rate of the branched condensate.

  In FIG. 2, in the heat pump 11, heat is pumped from the condenser outlet cooling water from the condenser outlet cooling water pipe 13, and a part of the condensate 14 is heated to about 90 ° C. by the heat pump 11 to generate high-temperature water. And used as water supply to the exhaust heat recovery boiler 3. In the exhaust heat recovery boiler 3, the exhaust gas 24 of the gas turbine and the condensate of the condensate circulation system 14 are heat-exchanged to generate steam. This generated steam is provided with a circulating water pipe F23 that branches off from the system to be sent to the steam turbine via the boiler drum 22 and is sent again to the exhaust heat recovery boiler inlet, so that the boiler water circulation system (that is, the exhaust heat recovery boiler) is provided. A circulating water system) is formed.

  Condensate from the condensate circulation system supplied directly from the condenser 6 and condensate from the pipe E19 heated by the heat pump 11 are mixed at the inlet of the economizer 20, and the boiler water of the exhaust heat recovery boiler 3 is mixed. Is supplied to the economizer 20. The boiler water to be supplied is partially heated by the heat pump 11, so that the temperature is higher than the outlet temperature of the condenser 6. The boiler water supplied to the economizer 20 exchanges heat with the exhaust gas 24 in the exhaust heat recovery boiler 3 and is sent to the steam turbine 4 as boiler steam.

  On the other hand, the exhaust heat recovery boiler 3 can be recovered from the exhaust gas 24 because the inlet exhaust gas temperature and the exhaust gas flow rate depend on the gas turbine 1 and the outlet exhaust gas temperature must be equal to or higher than the acid dew point temperature for the purpose of preventing corrosion. The amount of heat is determined by the specifications.

  In the exhaust heat recovery boiler 3, the amount of heat recovered from the exhaust gas 24 is given to the supplied boiler water to generate steam. As shown in FIG. 3, the amount of heat Q1 recovered from the exhaust gas 24 is obtained by calculation. Therefore, if the temperature T2 of the generated steam is determined, the amount of generated steam can be obtained.

  When the amount of steam is increased, the difference between the amount of heat Q1 recovered from the exhaust gas and the amount of heat Q2 required for generating steam obtained from the amount of steam to be increased is compensated by the amount of heat applied by the heat pump 11. That is, by raising the feed water temperature at the inlet of the economizer 20 from T1 to T3, the shortage of the difference in heat quantity between Q1 and Q2 can be compensated. Conventionally, the amount of heat of Q2 is supplied from the gas turbine 1 by exhaust gas, but the amount of heat supplied from the gas turbine 1 can be Q1. The flow rate of the condensate heated by the heat pump 11 is calculated in advance from the heat balance.

  As shown in FIG. 4, the feed water temperature can be controlled to be T3, and the temperature in the exhaust heat recovery boiler 3 can be controlled to be a one-dot chain line.

  Moreover, since the temperature of the condenser outlet cooling water that is a low-temperature heat source of the heat pump 11 varies depending on the atmospheric temperature, a function that determines the feed water flow rate to the heat pump 11 is determined for each atmospheric temperature as shown in FIG. This will increase the accuracy.

  FIG. 5 is an example of a function representing the relationship between the flow rate of condensate from the condensate circulation system 14 that supplies water to the exhaust heat recovery boiler and the flow rate of water supply (heated condensate) after being heated by the heat pump 11. This function is determined so that the heat recovery in the exhaust heat recovery boiler 3 is maximized, and the condensate flow rate as a high-temperature heat source to the heat pump 11 is determined based on this function. It should be noted that the exhaust heat recovery boiler water supply amount (boiler water) on the horizontal axis in FIG. 5 can also determine a function of gas turbine load, steam turbine load, plant load, and the like.

  The temperature signal generated by the thermometer 25 is used to monitor the outlet temperature so that it does not fall below the acid dew point. The distribution of the flow rate to the water supply side of the heat pump 11 can be controlled.

  According to the present embodiment, the heat transfer area cannot be increased beyond a predetermined upper limit value by preheating the exhaust heat recovery boiler feed water with the recovered heat amount by the heat pump, and the generated boiler steam amount also has an upper limit. Even in the exhaust heat recovery boiler, the amount of generated steam can be increased.

  3 and 4 show the effects obtained by this embodiment.

  In FIG. 3, the exhaust gas temperature and the exhaust gas flow rate of the exhaust heat recovery boiler depend on the gas turbine, and the outlet exhaust gas temperature must be equal to or higher than the acid dew point temperature as described above. Is required as Q1. On the other hand, the condensate supplied to the exhaust heat recovery boiler at T1 ° C is sent to the exhaust heat recovery boiler in the order of the economizer, evaporator, and superheater, receives the amount of heat Q1 recovered from the exhaust gas, and becomes T2 ° C steam. . The broken line in FIG. 3 has shown the temperature change of these waste gas and feed water.

  On the other hand, in FIG. 3, the solid line shows the temperature change when the amount of steam generated by the boiler is increased. The amount of heat required to increase the amount of steam generated by the boiler is Q2, but the amount of heat Q1 recovered from the exhaust gas does not change, so the amount of heat for Q2-Q1 is insufficient. In this embodiment, the insufficient heat quantity is compensated by the heat quantity obtained by the heat pump.

In other words, by raising the temperature of the condensate supplied at T1 ° C. in FIG. 4 to T 3 ° C., the water supply temperature follows a temperature change as indicated by the alternate long and short dash line, and the insufficient heat quantity when the amount of steam generated by the boiler increases, It is compensated by the amount of heat recovered by the heat pump.
In addition, as another effect, by configuring the heat recovery system as in the present invention, the condenser outlet cooling water that has been conventionally discharged at low temperature can be efficiently discharged by a heat pump. It can pump up heat and effectively use the pumped-up heat energy.

  A second embodiment of the present invention will be described with reference to the system diagram of FIG. 1 and FIG.

  As in the first embodiment, the gas turbine 1, the generator 2, the exhaust heat recovery boiler 3, the steam turbine 4, the generator 5 driven by the steam turbine, the condenser 6, and the steam turbine condensate are recovered as exhaust heat. In a combined cycle (boiler steam turbine system) having a cooling water circulation system such as a condensate pump 9 for supplying water to the boiler 3, a heat pump 11 pumps up the heat energy of the condenser outlet cooling water of the condenser outlet cooling water pipe 13. And the condenser outlet cooling water gives heat through the heat pump 11, and a pipe A15 and a pipe B16 are provided for returning to the cooling tower 7 as a drain.

  Here, as in the first embodiment, when supplying the condensate of the condensate circulation system 14 to the exhaust heat recovery boiler 3 as boiler water, a part of the condensate is heated by the amount of heat recovered by the heat pump 11. . For this purpose, in addition to the water supply pipe C17 for directly supplying the condensate 14 to the exhaust heat recovery boiler 3, a pipe D18 for newly sending the condensate of the condensate circulation system 14 as a high-temperature heat source of the heat pump, and a high temperature A water supply pipe E19 for supplying the condensate of the condensate circulation system 14 to the exhaust heat recovery boiler 3 is installed.

  FIG. 6 is an example showing where to use the amount of heat given by the heat pump 11. In the exhaust heat recovery boiler 3, if the heat transfer area of the heat transfer tube is increased and the temperature difference between the exhaust gas temperature and the feed water outlet temperature is narrowed, that is, the temperature difference is changed from t1 ° C to t2 ° C, The temperature change of the water supply is as shown by the solid line. Also in this case, the amount of heat is insufficient because the amount of heat Q1 recovered from the exhaust gas is smaller than the amount of heat Q3 necessary to generate steam. By introducing the heat pump 11, it is possible to efficiently pump up the amount of heat that has not been used, and to compensate for this shortage of heat.

It is a schematic systematic diagram showing an embodiment of the present invention. It is a block diagram which shows embodiment of this invention. It is a characteristic view of an exhaust heat recovery boiler showing an embodiment of the present invention. It is a characteristic view of an exhaust heat recovery boiler showing an embodiment of the present invention. It is a characteristic view for the feed water flow rate determination which shows the embodiment of the present invention. It is a characteristic view of an exhaust heat recovery boiler showing an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gas turbine, 2 ... Generator, 3 ... Waste heat recovery boiler, 4 ... Steam turbine, 5 ... Generator, 6 ... Condenser, 7 ... Cooling tower, 8 ... Feed water pump, 9 ... Condensate pump, 10 ... three-way valve, 11 ... heat pump, 12 ... chimney, 13 ... condenser outlet cooling water pipe, 14 ... condensate circulation system, 15 ... pipe A, 16 ... pipe B, 17 ... pipe C, 18 ... pipe D, 19 ... Pipe E, 20 ... economizer, 21 ... water level control valve, 22 ... low pressure drum, 23 ... pipe F, 24 ... exhaust gas, 25 ... thermometer, 26 ... control device, 27 ... evaporator, 28 ... superheater, 31 ... control valve, 40 ... flue, 41 ... boiler piping, 42 ... thermometer, 100 ... heat recovery system.

Claims (5)

Waste heat recovery boiler, steam turbine using steam from exhaust heat recovery boiler as a power source, condenser for condensing steam working in steam turbine, condensate circulation from condenser to exhaust heat recovery boiler A heat recovery system attached to a boiler-steam turbine system having a condensate circulation system and a cooling water supply system for supplying cooling water to the condenser,
A heat pump connected to a pipe for guiding cooling water from the cooling water supply system, and connected to a pipe branched from the condensate circulation system via a branch valve;
A controller for controlling the temperature of the mixed boiler water introduced into the economizer by mixing the condensate heated by the heat pump with the condensate from the condensate circulation system to form boiler water; A heat recovery system attached to a boiler-steam turbine system characterized by being provided. Waste heat recovery boiler, steam turbine using steam from exhaust heat recovery boiler as a power source, condenser for condensing steam working in steam turbine, condensate circulation from condenser to exhaust heat recovery boiler A heat recovery system attached to a boiler-steam turbine system having a condensate circulation system and a cooling water supply system for supplying cooling water to the condenser,
A heat pump connected to a pipe for guiding cooling water from the cooling water supply system, and connected to a pipe branched from the condensate circulation system via a branch valve;
The condensate heated by the heat pump is mixed with the condensate from the condensate circulation system and the boiler water circulated by the boiler water circulation system of the exhaust heat recovery boiler and led out of the economizer to form boiler water. And a controller for controlling the temperature of the mixed boiler water introduced into the economizer. A heat recovery system attached to a boiler-steam turbine system.   The thermometer which measures the gas temperature of the exhaust heat gas introduce | transduced into the said economizer in Claim 2, The said control apparatus inputs the temperature signal from the said thermometer at least, and branches from the said condensate circulation system The heat recovery system attached to the boiler-steam turbine system is characterized in that it controls the amount of recirculated condensate or the amount of boiler water circulated by the boiler water circulation system and led out of the economizer.   4. The control device according to claim 3, wherein the control device inputs a temperature signal from a condensate circulation thermometer provided in the condensate circulation system, and circulates by a circulation amount of condensate branched from the condensate circulation system or by the boiler water circulation system. A heat recovery system attached to a boiler-steam turbine system that controls the amount of boiler water that is led out of the economizer. 5. The boiler-steam according to claim 3, wherein the control device preferentially controls the amount of boiler water led out of the economizer in preference to the control of the circulation amount of branched condensate. A heat recovery system attached to the turbine system.

Images