JP2018025358A - Heat recovery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat recovery system capable of effectively preventing a state where stop of circulation of high-temperature fluid causes cooling water retaining in a heat exchanger to become a high-temperature state, leading to corrosion of inside of the heat exchanger.SOLUTION: A heat recovery system 1 includes: an oil cooler 23 for heating supply water W1 by exchanging heat between lubrication oil H1 serving as high-temperature fluid flowing in a circulation line L4 and the supply water W1 serving as cooling water including a corrosive substance; and a control section 90 for controlling circulation of the lubrication oil H1 and the flowing of the supply water W1. The control section 90 continues the flowing of the supply water W1 until a temperature of the supply water W1 that has passed through the oil cooler 23 reaches below a predetermined temperature enabling suppression of high-temperature corrosion of the oil cooler 23, even after the circulation of the lubrication oil H1 is stopped.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat recovery system for exchanging heat between a high-temperature heat medium flowing through a circulation line and cooling water.

  Conventionally, a heat recovery system that cools a high-temperature fluid and heats the cooling water by performing heat exchange between the high-temperature fluid to be cooled and the cooling water is known. For example, Patent Literature 1 and Patent Literature 2 disclose this type of technology. Patent Document 1 collects high-temperature drain from steam-utilizing equipment into a water supply tank, and recovers the compression heat of the oil supply type air compressor by heat exchange with boiler feed water (cooling water) sent to the water supply tank. Thus, a technique for raising the temperature of boiler feed water and cooling the lubricating oil of the compressor is disclosed. In Patent Document 2, as a heat recovery system for recovering the compression heat of an oil supply type air compressor, lubricating oil (high temperature fluid) sent to an oil cooler (oil cooler) and boiler feed water (cooling water) sent to a water supply tank ) And a configuration for performing heat exchange between them. In the heat recovery systems of Patent Literatures 1 and 2, cooling and heat recovery of the lubricating oil are performed while circulating the lubricating oil between the compressor and the heat exchanger during operation of the compressor.

JP 2010-38383 A JP 2012-87664 A

  By the way, since the circulation of the lubricating oil in the oil supply type air compressor is due to a mechanical pump action such as a screw type compression mechanism or a scroll type compression mechanism, when the operation of the compressor is stopped, Distribution of lubricating oil (high temperature fluid) stops. At this time, if the supply of cooling water is stopped when the compressor that is the heat source is stopped, the cooling water staying inside the heat exchanger may be overheated by the high-temperature lubricating oil remaining inside the heat exchanger. is there.

  Since cooling water usually uses tap water or industrial water, anions such as chloride ions and sulfate ions, and oxidizing substances such as residual chlorine are often contained as corrosive substances. The same water quality tendency is obtained when boiler feed water is used as cooling water. Therefore, although metal materials that take corrosion resistance into consideration, such as stainless steel, are used in heat exchangers, corrosive substances promote the corrosion of metal materials at higher temperatures, so the service life of heat exchangers is unstable. It is easy to become. Furthermore, if the cooling water staying in the heat exchanger continues to be overheated, local boiling may occur on the surface of the heat transfer surface. If it does so, a corrosive substance will be concentrated and corrosion of a metal material will progress more. Although it is conceivable to use a heat exchanger that uses titanium as a highly corrosion-resistant metal material, titanium materials themselves are expensive, and it is time-consuming to amortize equipment costs at sites where it is difficult to obtain the benefits of heat recovery. So it was difficult to apply.

  An object of the present invention is to provide a heat recovery system that can effectively prevent a situation in which cooling water staying inside a heat exchanger is overheated by a high-temperature fluid and the inside of the heat exchanger is corroded.

  The present invention includes a heat exchanger that heats cooling water by exchanging heat between the high-temperature fluid and cooling water containing a corrosive substance, and a controller that controls the flow of the high-temperature fluid and the cooling water. And the control unit distributes the cooling water until the temperature of the cooling water that has passed through the heat exchanger falls below a predetermined temperature at which high-temperature corrosion of the heat exchanger can be suppressed even after the flow of the high-temperature fluid is stopped. Continuing heat recovery system.

  The cooling water is, for example, fresh water containing chloride ions and / or sulfate ions as a corrosive substance. The cooling water is, for example, fresh water containing residual chlorine as a corrosive substance.

  The predetermined temperature capable of suppressing high temperature corrosion of the heat exchanger is preferably a temperature of 50 ° C. or lower.

  When the flow of the high-temperature fluid is stopped, the control unit preferably continues the flow of the cooling water until a set time elapses.

  The heat recovery system further includes a temperature detection unit that detects a temperature of the cooling water flowing out of the heat exchanger, and the control unit monitors the detection temperature of the temperature detection unit when the flow of the high-temperature fluid stops. It is preferable to continue the circulation of the cooling water until the temperature falls below the predetermined temperature.

  ADVANTAGE OF THE INVENTION According to this invention, the heat recovery system which can prevent effectively the situation which the cooling water which retains in a heat exchanger with a high temperature fluid is overheated, and the inside of a heat exchanger is corroded can be provided.

It is a figure showing typically composition of a heat recovery system concerning a 1st embodiment of the present invention. It is a figure which shows typically the structure of the heat recovery system which concerns on 2nd Embodiment of this invention.

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

<First Embodiment>
FIG. 1 is a diagram schematically showing a configuration of a heat recovery system 1 according to the first embodiment of the present invention. The heat recovery system 1 of the first embodiment includes a compressor unit 10, a heat recovery unit 20, a cooling water feed pump 21, and a control unit 90 as main components. The heat recovery system 1 heats the feed water W <b> 1 (cooling water) to the steam boiler 4 by recovering the compression heat generated in the compressor unit 10 by the heat recovery unit 20.

  The heat recovery system 1 includes a control unit 90 that performs various controls such as water supply control to the water supply tank 5 and supply or stop of the compressed air A1. The control unit 90 is a computer that is electrically connected to each component. Next, each configuration will be described.

[Compressor unit 10]
The compressor unit 10 is a unit for sucking outside air and adiabatically compressing it to generate compressed air A1. As shown in FIG. 1, the compressor unit 10 includes a compressor 11, a steam engine 12, a steam capacity control valve 13, a check valve 14, and an oil separator 15 as main components. These components are housed in a single housing and packaged.

The components of the compressor unit 10 will be described.
The compressor 11 has a screw mechanism (not shown) as an air compression mechanism, and cools the air compression mechanism, that is, removes the compression heat, by introducing the lubricating oil H1 into the screw mechanism in the process of generating the compressed air A1. Is an oil supply type (also called oil cooling type or oil lubrication type). In addition, various mechanisms, such as a scroll mechanism and a rotary mechanism, are employable as an air compression mechanism.

  The steam engine 12 is a drive source that drives the compressor 11. The steam engine 12 is connected to a steam supply line L1 for supplying steam and an exhaust steam line L2 for discharging steam. In the present embodiment, a shaft leak steam line L6 for discharging shaft leak steam is further connected.

  The steam capacity control valve 13 is disposed in the steam supply line L1. The driving, stopping, and output of the steam engine 12 are adjusted by opening / closing the steam capacity control valve 13 and changing the opening. Further, the check valve 14 is arranged in the exhaust steam line L2. The drive source of the compressor 11 is not limited to the steam drive type, and various drive sources such as an electric drive type motor can be employed.

  The oil separator 15 is a separator for the lubricating oil H1 contained in the compressed air A1 discharged from the compressor 11.

  An air supply line L3 for sending the compressed air A1 is connected to the compressor 11. In the air supply line L3, an oil separator 15 and an air cooler 22 (also referred to as aftercooler) are arranged in order from the upstream. The compressed air A1 discharged from the compressor 11 is sent to the air cooler 22 of the heat recovery unit 20 described later after the lubricating oil H1 is separated by the oil separator 15 through the air supply line L3. An air dryer (not shown) is disposed downstream of the air cooler 22 in the air supply line L3. The compressed air A1 is sent to a compressed air utilization device (not shown) after moisture is removed by the air dryer.

  The oil separator 15 is connected to a circulation line L4 for reintroducing the separated and recovered lubricating oil H1 into the compressor 11. In the circulation line L4, the oil cooler 23 and the three-way valve 16 are arranged in order from the upstream. The remaining port of the three-way valve 16 is connected to a bypass line L5 that bypasses the oil cooler 23 and distributes the lubricating oil H1.

[Heat recovery unit 20]
As shown in FIG. 1, an air cooler 22, an oil cooler 23, a drain heat exchanger 24, an electric valve 25, and a temperature sensor 26 are arranged as components of the heat recovery unit 20 in order from the upstream side in the water supply line L <b> 10. The The heat recovery unit 20 of the present embodiment is packaged by housing these components in one housing. As a result, the existing compressor unit 10 can be retrofitted. Specifically, the air supply line L3 extending from the oil separator 15 is drawn to the outside of the compressor unit 10 on the way to the air cooler 22, and after being disposed at an appropriate position inside the heat recovery unit 20, It is returned to the inside of the compressor unit 10 again. On the other hand, the circulation line L4 extending from the oil separator 15 is drawn to the outside of the compressor unit 10 on the way to the oil cooler 23, and after being disposed at an appropriate position inside the heat recovery unit 20, the compressor again. It is returned to the inside of the unit 10.

  The air cooler 22 is a heat exchanger that performs heat exchange between the compressed air A1 (high temperature fluid) and the feed water W1 (cooling water). In the air cooler 22, the feed water W1 is heated and the compressed air A1 is cooled.

  The oil cooler 23 is a heat exchanger that performs heat exchange between the lubricating oil H1 (high temperature fluid) and the feed water W1 (cooling water). In the oil cooler 23, the feed water W1 heated by the air cooler 22 is heated and the lubricating oil H1 is cooled.

  The drain heat exchanger 24 is a heat exchanger that performs heat exchange between the shaft seal leaking steam (high temperature fluid) and the feed water W1 (cooling water). In the drain heat exchanger 24, the feed water W1 heated by the oil cooler 23 is heated, and the shaft seal leaking steam is cooled to become low-temperature condensed water. The shaft seal leaking steam may include high-temperature steam condensed water (drain).

  In this embodiment, the air cooler 22, the oil cooler 23, and the drain heat exchanger 24 are connected in series, and the feed water W1 is heated a plurality of times by these heat exchangers. That is, the heat recovery unit 20 heats the water supply W1 (cooling water) flowing through the water supply line L10 by performing heat recovery from the compressed air A1, the lubricating oil H1, and the shaft seal leakage steam that are high-temperature fluids.

  The electric valve 25 is a proportional control valve whose opening degree can be changed. The electric valve 25 of this embodiment is arrange | positioned further downstream of the drain heat exchanger 24 located in the most downstream among the heat exchangers arrange | positioned in multiple numbers.

  The temperature sensor 26 detects the temperature of the water supply W1 on the downstream side of the motor-operated valve 25. A temperature sensor 26 detects the temperature of the water supply W1 that is sequentially heated by the air cooler 22, the oil cooler 23, and the drain heat exchanger 24.

[Cooling water feed pump 21]
The cooling water feed pump 21 applies pressure to the feed water W1 (cooling water) sent from a supply source (not shown) through the feed water line L10. The cooling water supply pump 21 of the present embodiment is operated at a constant pressure by the control unit 90.

  The water supply W1 supplied from the supply source of this embodiment is fresh water containing corrosive substances such as tap water and industrial water. Examples of corrosive substances contained in the feed water W1 include chloride ions, sulfate ions, and residual chlorine. These corrosive substances can be contained alone or in parallel. In the case of water supply W1 for boiler water supply, hardness components (calcium ions and magnesium ions) are removed by the water softening device upstream of the heat recovery unit 20, but corrosive substances remain in the water supply W1.

[Steam boiler 4 and incidental equipment]
The feed water W1 sent through the feed water line L10 is stored in the feed water tank 5, and then sent to the steam boiler 4. In addition to the water supply line L10, a makeup water line L11 is connected to the water supply tank 5 of the present embodiment, and makeup water is also supplied from the makeup water line L11. Further, an overflow line L12 for discharging a predetermined amount or more of water to the outside is connected.

  In the present embodiment, a makeup water valve 51 is arranged in the makeup water line L11, and supply / stop of makeup water to the feed water tank 5 is switched by opening and closing the makeup water valve 51. A water level detector 52 is disposed in the water supply tank 5, and the water level of the water supply tank 5 is maintained in an appropriate range by controlling the replenishment water valve 51 based on the detection signal of the water level detector 52.

  The water stored in the feed water tank 5 is sent to the steam boiler 4 through the boiler feed water line L15. A water supply pump 55 and a check valve 56 are arranged in the boiler water supply line L15. The feed water W 1 stored in the feed water tank 5 is sent to the steam boiler 4 by driving the feed water pump 55. In the steam boiler 4, the feed water W1 sent through the boiler feed water line L15 is heated to generate steam. The generated steam is supplied to a steam use facility (not shown).

[Example of operation control by the control unit 90]
The control unit 90 drives the cooling water feed pump 21 when receiving the start signals of the compressor unit 10 and the heat recovery unit 20 during the operation of the steam boiler 4. Next, the electric valve 25 of the heat recovery unit 20 is opened to supply the water supply W1. The valve opening degree of the motor-operated valve 25 is adjusted so that the temperature detected by the temperature sensor 26 becomes the target temperature. The feed water flow rate sent to the air cooler 22, the oil cooler 23, and the drain heat exchanger 24 is adjusted by adjusting the valve opening.

  In this embodiment, the air cooler located on the upstream side of the motor-operated valve 25 by restricting the flow path of the water supply line L10 by the motor-operated valve 25 disposed on the downstream side of the air cooler 22, the oil cooler 23, and the drain heat exchanger 24. 22, pressure is applied to the water supply W <b> 1 that flows inside the oil cooler 23 and the drain heat exchanger 24. The pressure of the feed water W1 flowing inside the air cooler 22, the oil cooler 23 and the drain heat exchanger 24 increases, thereby creating a situation in which dissolved gas such as dissolved oxygen is difficult to be released, and pressure that prevents the accumulation of bubbles that cause corrosion Functions as a grant unit. The retention of bubbles tends to cause the stagnation of the water flow, and the stagnation of the water flow tends to cause the corrosion of the metal by the corrosive substance. Therefore, in this embodiment, the operation is performed so that bubbles do not stay.

  The controller 90 circulates the feed water W1 and controls the steam capacity control valve 13 of the compressor unit 10 to be in an open state to drive the steam engine 12. The controller 90 performs load / unload control of the compressor 11 according to the amount of compressed air used during the operation of the compressor unit 10 and the heat recovery unit 20. The amount of compressed air used can be determined based on, for example, the pressure in a receiver tank (not shown) that stores the compressed air.

  By operating the compressor 11, the lubricating oil H1 circulates through the circulation line L4. More specifically, the compressed air A1 discharged by the compressor 11 is sent to the oil separator 15, and the lubricating oil H1 is separated from the compressed air A1 by the oil separator 15. The lubricating oil H1 separated by the oil separator 15 is sent to the oil cooler 23 through the circulation line L4, exchanges heat with the feed water W1, and then returned to the compressor 11. In this embodiment, the low temperature lubricating oil H1 may return to the compressor 11 without passing through the oil cooler 23 through the bypass line L5. However, the lubricating oil H1 separated by the oil separator 15 is passed through any path. Will return to the compressor 11. Thus, during the operation of the compressor 11, the lubricating oil H1 circulates through the circulation line L4.

[Example of stop control by the control unit 90]
When receiving a stop signal for the compressor unit 10 and the heat recovery unit 20, the control unit 90 closes the steam capacity control valve 13 of the compressor unit 10 and stops driving the steam engine 12. Along with this, the circulation of the lubricating oil H1 is also stopped.

  When the compressor unit 10 is stopped, the control unit 90 starts the corrosion prevention control for monitoring the temperature detected by the temperature sensor 26 in a state where the motor-operated valve 25 is kept open. In the corrosion prevention control, the valve opening degree of the electric valve 25 before receiving the stop signal of the compressor unit 10 is maintained, and the temperature detected by the temperature sensor 26 is monitored.

  In the corrosion prevention control, the control unit 90 continues the circulation of the feed water W1 until the temperature of the feed water W1 being monitored falls below a predetermined temperature. The predetermined temperature is a temperature set from the viewpoint of preventing high-temperature corrosion of each heat exchanger 22, 23, 24 for heat recovery. When the temperature of the feed water W1 after passing through the heat exchangers 22, 23, and 24 is equal to or lower than a predetermined temperature, the control unit 90 of the present embodiment can compress the compressed air A1, the lubricating oil H1, and the shaft seal leakage. It is determined that the temperature of the steam is sufficiently lowered and the water supply W1 is not overheated inside each heat exchanger 22, 23, 24.

  The predetermined temperature is set as a temperature at which high temperature corrosion of the heat exchanger caused by overheating of the feed water (corrosion promoting action of corrosive substances in a high temperature state) can be suppressed. This specified temperature depends on the type and concentration of corrosive substances in the feed water (average value and actual measurement value), heat exchanger structure (plate type, shell & tube type, etc.), heat exchanger material, etc. It is preferable to make a determination based on preliminary corrosion experiment data reflecting the use conditions. For example, when the heat exchanger is formed of a material excellent in stress corrosion cracking resistance, it is preferable to set the predetermined temperature to 90 ° C. or less, and the exchanger is formed of a material having poor stress corrosion cracking resistance. In some cases, the temperature is preferably set to 50 ° C. or lower. In the present embodiment, a temperature of 50 ° C. or less is set as the predetermined temperature.

The predetermined temperature can be a fixed value, or a variable value that changes each time the compressor 11 is stopped. When the predetermined temperature is a fluctuation value, it is preferable to set as follows.
[Example 1] The temperature of the lubricating oil H1 when the compressor 11 is stopped (for example, the oil temperature after separation by the oil separator 15) is set as a base temperature, and a temperature obtained by subtracting a constant value from the base temperature is set as a predetermined temperature. For example, if the oil temperature when the compressor 11 is stopped is in the range of 80 to 90 ° C, the predetermined temperature is set in the range of 40 to 50 ° C, which is 40 ° C lower than this temperature.
[Example 2] The temperature of the unheated water supply W1 at the time of stopping the compressor 11 (for example, the water temperature before flowing into the air cooler 22) is set as a base temperature, and a temperature obtained by adding a constant value from the base temperature is set as a predetermined temperature. . For example, if the water temperature when the compressor 11 is stopped is in the range of 15 to 35 ° C., the predetermined temperature is set in the range of 30 to 50 ° C., which is 15 ° C. higher than this temperature.

  When the temperature of the feed water W1 being monitored falls to a predetermined temperature, the control unit 90 closes the motor-operated valve 25 and stops the flow of the feed water W1. The circulation of the cooling water is continued until the temperature of the feed water W1 drops to a predetermined temperature (temperature of 50 ° C. or lower), whereby the high-temperature fluid (compressed air A1, Lubricating oil H1 and shaft seal leakage steam) are also cooled. In the present embodiment, since the valve opening of the motor-operated valve 25 during operation of the compressor unit 10 is maintained, the feed water W1 is continuously fed in the same manner as during operation, so that the high-temperature fluid is effectively cooled. be able to. Therefore, it is possible to reliably prevent a situation in which the cooling water staying inside each of the heat exchangers 22, 23, 24 is overheated by the high-temperature fluid and is likely to cause high-temperature corrosion.

  The feed water W <b> 1 that continues to flow even during the corrosion prevention control is stored in the feed water tank 5 and then sent to the steam boiler 4. During operation of the steam boiler 4, the water supply W1 is used, the load on the steam boiler 4 increases, the amount of water used increases, and when the lower limit set value (water supply start water level) is detected, the supply water valve 51 is opened to supply water. Supply water to the tank 5.

The heat recovery system 1 according to the first embodiment described above has the following effects.
That is, the heat recovery system 1 of the first embodiment performs cooling by exchanging heat between a high-temperature fluid (compressed air A1, lubricating oil H1 and shaft seal leakage steam) and cooling water containing corrosive substances (feed water W1). Heat exchangers 22, 23, and 24 for heating water, and a control unit 90 for controlling the flow of the high-temperature fluid and the flow of the cooling water. The circulation of the feed water W1 is continued until the temperature of the cooling water that has passed through the exchangers 22, 23, and 24 falls below a predetermined temperature at which high-temperature corrosion of the heat exchangers 22, 23, and 24 can be suppressed.
As a result, the high-temperature fluid is sufficiently cooled by the cooling water continuously flowing even after the compressor 11 is stopped, so that high-temperature corrosion due to overheating inside the heat exchangers 22, 23, 24 can be reliably prevented.

The cooling water (feed water W1) of this embodiment is fresh water containing chloride ions and / or sulfate ions as corrosive substances, or fresh water containing residual chlorine as corrosive substances.
Thereby, even if it is a case where the cooling water containing a corrosive substance is used, the high temperature corrosion of the heat exchangers 22, 23, and 24 can be prevented by continuing circulation of cooling water until it falls to predetermined temperature.

In this embodiment, the predetermined temperature which can suppress the high temperature corrosion of the heat exchangers 22, 23, 24 is set to 50 ° C. or less.
Thereby, the cooling water can be stopped in a state in which the high-temperature fluid is sufficiently cooled to a temperature at which the high-temperature corrosion of the heat exchangers 22, 23, and 24 is reliably suppressed.

The heat recovery system 1 of the present embodiment further includes a temperature sensor 26 that detects the temperature of the cooling water (feed water W1) flowing out from the heat exchangers 22, 23, and 24, and the control unit 90 stops the flow of the high-temperature fluid. Then, the temperature detected by the temperature sensor 26 is monitored and the circulation of the cooling water is continued until the temperature falls below a predetermined temperature.
Thereby, since it can be determined whether the cooling water has been sufficiently cooled based on the temperature detected by the temperature sensor 26, the heat exchangers 22, 23, 24 are always stopped in a thermally protected state. Will be. As a result, the heat exchangers 22, 23, 24 are prevented from being damaged and can be used for a long period of time.

  As described above, the corrosion prevention control by the heat recovery system 1 of the first embodiment has been described. However, as a method for lowering the feed water W1 as the cooling water to a predetermined temperature, a method other than the determination based on the temperature detected by the temperature sensor 26 is used. Can be adopted. Next, a modification of the first embodiment will be described in which it is determined whether or not the feed water W1 has dropped to a predetermined temperature after the flow of the high-temperature fluid is stopped by a method other than the determination based on the temperature detected by the temperature sensor 26.

The control unit 90 of the modified example uses a set time set in advance as a reference for determining that the feed water W1 has become a predetermined temperature or less after the flow of the high-temperature fluid (compressed air A1, lubricating oil H1, and shaft seal leakage steam) is stopped. Use. That is, when the flow of the high-temperature fluid stops, the control unit 90 continues the flow of the water supply W1 until the set time elapses.
Also with this configuration, it is possible to determine whether or not the high-temperature fluid has been sufficiently cooled, so that the heat exchangers 22, 23, and 24 are always stopped in a thermally protected state. Further, since the determination criterion is time, control for realizing corrosion prevention can be configured simply.

  The set time is a sufficient time for cooling the temperature of the high-temperature fluid to a predetermined temperature or less. The set time may be a time set based on experimental data, or operation history data of the compressor unit 10 (for example, a time required from the stop of the compressor 11 to the stop of water supply in the first embodiment). It may be set based on the maximum value). From the viewpoint of reliably reducing the risk of high temperature corrosion, it is preferable to lower the temperature of the feed water W1, and therefore it is preferable to set the set time longer. When the set time is set to be long, the valve opening of the motor-operated valve 25 may be gradually reduced in conjunction with a decrease in the temperature detected by the temperature sensor 26.

  In 1st Embodiment mentioned above, although demonstrated as an example the heat recovery system applied to an oil supply type compressor, this invention is applicable also to the heat recovery system applied to an oil free type compressor. For example, in the heat recovery system described in Japanese Patent Application No. 2014-212163 by the present applicant, after passing the flow of compressed air (high temperature fluid) to the heat recovery heat exchanger, the heat recovery system passed through the heat recovery heat exchanger. The circulation of the cooling water can be continued until the temperature of the cooling water falls below a predetermined temperature at which the high temperature corrosion of the heat recovery heat exchanger can be suppressed. In general, compressed air produced by an oil-free compressor is hotter than compressed air produced by an oil-filled compressor and thus is more likely to induce high-temperature corrosion of a heat exchanger. By adopting the corrosion suppression control, it is possible to effectively suppress the high temperature corrosion of the heat exchanger.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not restrict | limited to the above-mentioned embodiment, It can change suitably. In the said embodiment, although the heat recovery system applied to a compressor was demonstrated as an example, it is not limited to the structure of the said embodiment, This invention can be applied also to another use.

Second Embodiment
Next, the heat recovery system 301 of 2nd Embodiment which applied this invention to the system which heats the feed water W1 of the steam boiler 4 is demonstrated. FIG. 2 is a diagram schematically showing a configuration of a heat recovery system 301 according to the second embodiment of the present invention.

  As shown in FIG. 2, the heat recovery system 301 of the second embodiment is a feed water heating system that heats feed water W <b> 1 fed to the boiler by a vapor compression heat pump 302. The heat recovery system 1 includes a heat pump 302, a water softener 313, a waste heat recovery device 330, and a control unit 390.

  The heat pump 302 of the second embodiment includes a refrigerant compressor 310, a condenser 303, a supercooler 304, an expansion valve 305, and an evaporator 306. The compressor 310, the condenser 303, the expansion valve 305, and the evaporator 306 are sequentially connected in an annular shape by a refrigerant circulation line L310.

  The refrigerant compressor 310 has a motor 311 as a drive source, and compresses gaseous refrigerant such as Freon gas into a high-temperature and high-pressure refrigerant (high-temperature fluid) H2. The condenser 303 condenses and liquefies the refrigerant H2 from the refrigerant compressor 310. The subcooler 304 exchanges heat between the refrigerant H2 sent from the condenser 303 to the expansion valve 305 and the feed water W1 as cooling water sent to the condenser 303 to heat the feed water W1 and Cooling. The expansion valve 305 reduces the pressure and temperature of the refrigerant H2 sent from the condenser 303 through the supercooler 304. The evaporator 306 evaporates the refrigerant H2 sent from the expansion valve 305 using the heat source water W3 sent through the heat source water line L301 as a heat source.

  The water softener 313 produces the feed water W1 that is sent to the feed water tank 5 of the steam boiler 4 through the makeup water line L300. A raw water line (not shown) is connected to the water softener 313, and a water supply valve 315, a waste heat recovery unit 330, a supercooler 304, a condenser (heat exchanger) 303, and a water supply temperature sensor 324 are connected to the makeup water line L300. Are arranged sequentially. The water supply valve 315 is electrically connected to the control unit 390, and water supply is controlled by the control unit 390.

  As described above, in the heat recovery system 1 of the second embodiment, the refrigerant H2 recovers heat from the external heat source water W3 in the evaporator 306, and the feed water W1 is heated by the heat of the refrigerant H2 in the condenser 303. And in 2nd Embodiment, the control part 390 will stop compression of the refrigerant | coolant H2 by the refrigerant | coolant compressor 310, if the stop signal of the heat pump 302 is received, while stopping the circulation of the refrigerant | coolant H2, and the refrigerant | coolant H2 which is a high temperature fluid Even after the circulation (circulation) is stopped, the corrosion prevention control is performed so that the water supply W1 continues and flows to the condenser 303. Even in this configuration, it is possible to prevent a situation in which the feed water W1 is overheated by the refrigerant H2 remaining in the condenser 303 as a heat exchanger and the risk of high-temperature corrosion is increased. In the second embodiment, the feed water W1 is continuously passed through the condenser 303 until the temperature detected by the feed water temperature sensor 324 falls below a predetermined temperature.

  In the second embodiment, the corrosion prevention control is performed based on the temperature detected by the feed water temperature sensor 324. However, as in the modification of the first embodiment, the corrosion prevention control is performed based on the set time. Also good.

  In the above embodiment, the water supply amount is adjusted using the motor-operated valve 25. However, a configuration may be adopted in which the feed water W1 delivery amount is adjusted by changing the rotation speed of the water supply pump by frequency control using an inverter.

  Thus, the present invention can be applied to various heat recovery systems such as an air compressor and a heat pump that distribute a high-temperature fluid to a heat exchanger.

1 Heat recovery system 22 Air cooler (heat exchanger)
23 Oil cooler (heat exchanger)
24 Drain heat exchanger (heat exchanger)
26 Temperature sensor (temperature detector)
90 Control part 301 Heat recovery system 303 Condenser (heat exchanger)
390 Control unit H1 Lubricating oil (high temperature heat medium)
H2 heat medium (high temperature heat medium)
L4 Circulation line (circulation line)
L310 Heat pump circulation line (circulation line)
W1 Water supply (cooling water)

Claims (6)

A heat exchanger that heats the cooling water by exchanging heat between the high-temperature fluid and the cooling water containing corrosive substances;
A controller that controls the flow of the high-temperature fluid and the flow of the cooling water
The controller is
A heat recovery system that continues the circulation of cooling water until the temperature of the cooling water that has passed through the heat exchanger falls below a predetermined temperature at which high-temperature corrosion of the heat exchanger can be suppressed even after the circulation of the high-temperature fluid is stopped.   The heat recovery system according to claim 1, wherein the cooling water is fresh water containing chloride ions and / or sulfate ions as corrosive substances.   The heat recovery system according to claim 1, wherein the cooling water is fresh water containing residual chlorine as a corrosive substance.   The heat recovery system according to any one of claims 1 to 3, wherein the predetermined temperature capable of suppressing high temperature corrosion of the heat exchanger is a temperature of 50 ° C or lower. The controller is
The heat recovery system according to any one of claims 1 to 4, wherein when the flow of the high-temperature fluid is stopped, the flow of the cooling water is continued until a set time elapses. A temperature detector for detecting the temperature of the cooling water flowing out of the heat exchanger;
The controller is
The heat recovery system according to any one of claims 1 to 4, wherein when the circulation of the high-temperature fluid is stopped, the temperature detected by the temperature detection unit is monitored and the circulation of the cooling water is continued until the temperature falls below a predetermined temperature.

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