JP2015052406A - Drain recovery equipment, operation method of the same, and heat utilization system using drain recovery equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide drain recovery equipment, an operation method of the drain recovery equipment, and a heat utilization system using the drain recovery equipment which further improve heat recovery rate from a high-pressure and high-temperature drain in the drain recovery equipment A1 using a flash tank 40 and, when recovering drain water after separation by means of the drain water recovery tank under atmospheric pressure, can avoid the generation of flash steam (white smoke) released to the air.SOLUTION: A drain recovery equipment A1 includes means for generating a negative pressure in a closed system (including pipe lines 42, 43, 53) from a flash tank 40 to a second heat load device 50. Steam of a boiler 10 is introduced via a first branched pipe line 14 and a pressure-reducing valve 16 and an on-off valve 17 arranged on the first branched pipe line before starting the operation and air in the system is discharged from a purge valve 41. Thereafter, the on-off valve 17 is closed and it is waited that steam in the system is condensed. Such a cycle is repeated, the negative pressure is established in the system and, thereafter, high-pressure and high-temperature drain is introduced into the flash tank 40.

Description

  The present invention relates to a drain recovery facility, a method for operating the drain recovery facility, and a heat utilization system using the drain recovery facility, and in particular, sensible heat possessed by a high-pressure and high-temperature drain generated from a heat load device using steam generated by the steam generator. The present invention relates to a drain recovery facility capable of recovering latent heat with high efficiency, an operating method thereof, and a heat utilization system using the drain recovery facility.

  Steam generated from a steam generator such as a boiler is used in a heat load device such as a production facility or an air conditioner, loses latent heat, condenses, and is recovered as a high-pressure and high-temperature drain. It is not preferable to discharge the high-pressure and high-temperature drain as it is from the viewpoint of energy efficiency, and the flash vapor generated from the high-pressure and high-temperature drain when exposed to the atmosphere appears as white smoke. Therefore, in order to improve the heat recovery rate, high-pressure and high-temperature drain is introduced into a flash tank held at a lower pressure and re-evaporated, and gas-liquid separation into flash steam and warm water (drain water) is performed. There has been proposed a drain recovery facility in which the generated flash steam and warm water (drain water) are used again as a heat medium (Patent Documents 1, 2, 3, etc.).

JP 2009-198038 A JP 2012-7762 A JP 2012-72984 A

  In a drain recovery facility equipped with a flash tank that has been proposed in the past, during operation, the pressure in the flash tank is lower than the pressure of the high-pressure and high-temperature drain that is received, but is controlled to a positive pressure (above atmospheric pressure). Yes. The reason is that the steam generated from the flash tank (flash steam) may be used alone as a heat medium, but generally it is mixed with the steam generated from the boiler separately and used as a heat medium at the heat load destination. This is because they often do. The temperature of the hot water (drain water) after gas-liquid separation generated in the flash tank controlled to a positive pressure is 100 ° C. or higher, and the hot water (drain water) is recovered in the drain water recovery tank at atmospheric pressure. In addition, it is inevitable that flash vapor (white smoke) released into the atmosphere is generated, and there is room for improvement in the heat recovery rate.

  The present invention has been made in view of the above circumstances. In a drain recovery facility using a flash tank, the heat recovery rate from the high-pressure and high-temperature drain is further improved, and hot water (drain water) after separation is improved. ) Is recovered in a drain water recovery tank under atmospheric pressure, so that the generation of flash vapor (white smoke) released into the atmosphere can be avoided, a drain recovery facility, its operating method, and its drain It is an object to provide a heat utilization system using a recovery facility.

  In order to solve the above-mentioned problems, the present inventors further conduct research and experiments to forcibly discharge the air in the system out of the system using an air vent valve, thereby including a piping system including a flash tank. It was discovered that a drain recovery facility capable of solving the above problems can be obtained by maintaining the inside at a negative pressure (pressure lower than atmospheric pressure) and sufficiently recovering heat from the generated flash steam.

  The present invention has been made based on the above knowledge, and the drain recovery facility according to the present invention basically includes a steam generator, a first heat load device using the steam generated by the steam generator, A flash tank that re-evaporates the drain generated from the first heat load device and separates it into flash steam and first drain water, and a second heat load that uses the flash steam generated in the flash tank Drain having a drain water recovery tank for recovering the first drain water generated in the flash tank and the second drain water condensed by the flash vapor by passing through the second heat load device The drain recovery facility is configured to maintain a piping system in a closed system, and is closed from the flash tank to the second heat load device. Characterized by further comprising means for generating a negative pressure in the silicic.

  In the drain recovery facility according to the present invention, means for generating a negative pressure in the closed system from the flash tank to the second heat load device is not limited, but a steam generator is provided in the closed system. Provided with steam introduction means for introducing the generated steam and an air vent valve for discharging the air in the closed system out of the system, by introducing the steam into the closed system, the air in the system is expelled from the air vent valve A configuration in which a negative pressure is formed in a closed system by filling the system with steam and condensing the steam in the system by heat dissipation is an extremely effective mode. However, the present invention is not limited to this, and a vacuum pump or the like can be used.

  In the drain recovery facility according to the present invention, the second heat load device heats or heats the environmental air by exchanging heat with the environmental air or appropriate heating air for production from the viewpoint of obtaining a high heat recovery amount. An air heater that reheats air is preferable. However, the present invention is not limited to this, and a heat load device such as a feed water preheater or a washing water heater may be used.

  In the drain recovery facility according to the present invention, the drain water recovery tank is preferably a water supply tank to the steam generator from the viewpoint of improving the efficiency of the facility. However, the present invention is not limited to this, and it may be a water supply tank to other hot water use facilities such as washing water, washing water, CIP device water.

  The present invention further includes a step of operating a means for generating a negative pressure in the closed system to bring the closed system into a negative pressure state as an operation method of the drain recovery facility, Also disclosed is a method for operating a drain recovery facility, in which a process of introducing drain generated in the first heat load device into the closed system that has become negative pressure by performing a process is started. .

  The present invention further provides an air that is the second heat load device as a heat utilization system using the drain recovery facility when the drain recovery facility according to the present invention uses an air heater as the second heat load device. A heat utilization system in which a heater is used for preheating combustion air of an appropriate combustion device, and a heat utilization system using the drain recovery facility in the case where the steam generator is a combustion-type boiler. A heat utilization system using a drain recovery facility in which an air heater as the second heat load device is used for preheating the supply air of the boiler is also disclosed.

  In the present invention, the drain generated from the first heat load device is a high-pressure high-temperature drain that is condensed water of steam from which flash steam can be taken out, and the first drain water generated in the flash tank is The drain is a low-pressure low-temperature drain after the flash steam is generated, and the second drain water is a negative-pressure low-temperature drain obtained by draining the flash steam. Here, “high temperature” is a temperature of 100 ° C. or higher, and “low temperature” is a temperature of less than 100 ° C.

  According to the drain recovery facility and the method of operating the same according to the present invention, the steam is introduced into the closed system from the flash tank to the second heat load device, for example, by introducing steam into the closed system. The air inside the system is filled with steam, and the vapor in the system is condensed by heat dissipation, so that a negative pressure is formed, and the system is in a negative pressure (below atmospheric pressure) Since the steam separation of the high-pressure and high-temperature drain proceeds in the flash tank, the flash rate (the weight of the flash steam generated from the high-pressure and high-temperature drain of the unit weight) is larger than when performing in a positive pressure state. By appropriately setting the negative pressure level, the temperature of the first drain water after separation can be set to a temperature lower than 100 ° C. Thereby, even if the first drain water is drained under atmospheric pressure, flash vapor (white smoke) released to the atmosphere does not occur. Also, by consuming a lot of heat in the second heat load device, the system from the flash tank to the second heat load device becomes negative pressure, and it is possible to maintain negative pressure during operation. Thus, the above-described operational effects are maintained even during operation.

  The separated flash vapor passes through the piping system that is also maintained at a negative pressure, and passes through the second heat load device as a heat medium. By exchanging heat with the second heat load device, the latent heat is lost, and the flash vapor is condensed to become second drain water. In addition to the negative pressure in the system, the temperature of the second drain water can also be set to a temperature lower than 100 ° C. by increasing the amount of heat recovered by the second heat load device. Even if the drain water is drained to the drain water recovery tank under atmospheric pressure together with the drain water of 1, the flash vapor (white smoke) released to the atmosphere is not generated.

  As described above, in the drain recovery facility and the operation method thereof according to the present invention, it is possible to recover latent heat with high efficiency from the sensible heat possessed by the high-pressure and high-temperature drain, thereby improving energy efficiency and, as a result, the flash tank. The hot water (first drain water) separated in step 1 and the warm water (second drain water) condensed by the flash steam by passing through the second heat load device are drained to a drain water recovery tank under atmospheric pressure. In addition, no flash vapor (white smoke) released into the atmosphere is generated, making the drain recovery facility friendly to the environment.

  Since the environmental air or the appropriate production heating air after being heat-exchanged by the air heater as the second heat load device according to the present invention is heated to a high temperature, it is the second heat load device. A heat utilization system using a drain recovery facility according to the present invention that uses an air heater for preheating combustion air for an appropriate combustion device, and further, when the steam generator is a combustion type boiler, The heat utilization system using the drain recovery facility according to the present invention in which the air heater as the heat load device 2 is used for preheating the combustion air of the boiler is a very effective heat utilization system.

The figure which shows the piping system of one Embodiment of the drain recovery equipment by this invention. The figure which shows the piping system of other embodiment of the drain collection | recovery installation by this invention. The figure for demonstrating the drain collection | recovery equipment used by the Example and the comparative example.

[First Embodiment]
Hereinafter, with reference to FIG. 1, the drain collection | recovery installation which concerns on the 1st Embodiment of this invention, its operating method, and the heat utilization system using the said drain collection | recovery installation are demonstrated.

  FIG. 1 shows an outline of a piping system of a drain recovery facility according to the first embodiment of the present invention. As shown in FIG. 1, the drain recovery facility A1 includes a boiler 10, a water supply tank 20, a first heat load device 30, a flash tank 40, and a second heat load device 50 as main components. In FIG. 1, a thick solid line is a piping system through which high-pressure and high-temperature drain, first drain water, flash steam, and second drain water flow, and a thin solid line is a piping system through which high-pressure steam from a boiler flows.

  The boiler 10 heats the water supplied from the water supply tank 20 to generate high-pressure and high-temperature steam, and is an example of a steam generator in the present invention. The high-pressure steam generated in the boiler 10 is sent to the steam header 12 through the pipe 11, and is supplied from there to the first heat load device 30 through the steam pipe 13. The water supply tank 20 is for supplying steam generation water to the boiler 10, and is connected to the boiler 10 via a water supply pipe 21. As will be described later, in the water supply tank 20, in addition to the water from the main water supply pipe 22, drain water (first drain water and second drain water) that has become 100 ° C. or less passes through the return pipe 23. Returned. A first branch pipe 14 and a second branch pipe 15 branch from the steam pipe 13, and the first branch pipe 14 is connected to the flash tank 40 via a pressure reducing valve 16 and an on-off valve 17. . An air vent valve 41 is attached to the flash tank 40. The second branch pipe 15 is connected via a pressure reducing valve 18 to steam drive traps 60A and 60B described later.

  The first heat load device 30 uses steam supplied from the boiler 10 via the steam header 12 as a heat medium. For example, the first heat load device 30 uses steam as a heat source used in a printing machine, a food machine, a papermaking machine, or the like. Examples of the apparatus and apparatus for heating a product (an apparatus having a steam heat exchanger) can be given. In the first heat load device 30, a part of the steam loses latent heat and condenses to become high-pressure and high-temperature drain (condensed water of steam from which flash steam can be taken out). The first heat load device 30 is connected to the flash tank 40 via a drain pipe 31, and is a mixed fluid of high-pressure and high-temperature drain discharged from the first heat load device 30 and flash steam of the same pressure generated from the drain. Flows into the flash tank 40 via the drain pipe 31. The drain pipe 31 is provided with a trap 32 and an on-off valve 33.

  The mixed fluid supplied via the drain pipe 31 is re-evaporated in the flash tank 40 to be separated into steam and water to generate flash steam and first drain water (negative pressure low temperature drain). The flash steam is sent to the air heater 50 which is an example of the second heat load device via the pipe 42. On the other hand, the first drain water is sent to the return pipe 23 through the pipe 43 and the steam driven trap 60A.

  The air heater 50 heats the environmental air using flash steam as a heat medium. The air heater 50 may be reheated by exchanging heat with the production air already used in the apparatus. The air heated by the heat exchange with the flash steam is sent to an appropriate high-temperature air utilization unit (for example, a dryer or an air supply unit of an industrial furnace) 52 through a duct 51. Alternatively, it is used as combustion air for appropriate combustion equipment. Further, the flash steam that has lost its latent heat by heating the air is condensed to become second drain water (negative pressure low temperature drain), and is sent to the return pipe 23 through the pipe 53. The first drain water and the second drain water collected in the return pipe 23 are returned to the water supply tank 20.

  The pipe 43 and the pipe 53 are provided with steam-driven traps 60A and 60B, respectively. The steam-driven traps 60A and 60B pass through the second branch pipe 15 and the steam is decompressed to about 0.2 MPaG by the pressure reducing valve 18. Is supplied as driving steam. Further, a position upstream of the on-off valve 33 in the drain pipe 31 and a position downstream of the connecting portion between the pipe 43 and the pipe 53 in the return pipe 23 are communicated by a bypass pipe 24. An open / close valve 25 is attached to the pipe 24.

[Drain recovery facility A1 operation method-selection 1]
Next, one option of the operation method of the drain recovery facility A1 will be described. First, in a state where the boiler 10 is generating high-pressure steam, a decompression process is performed on the inside of the flash tank 40 and a piping system related to the flash tank 40 (specifically, a region surrounded by a dotted line in FIG. 1), The system is in a negative pressure state. Procedureally, the steam traps 60A and 60B are kept closed, the on-off valve 33 attached to the drain pipe 31 is closed, the on-off valve 25 attached to the bypass pipe 24 is opened, and the first branch pipe 14 is opened. Open the on-off valve 17 attached to. Thereby, the high-pressure steam generated in the boiler 10 flows into the flash tank 40 through the first branch pipe 14.

  Due to the inflow of steam, the air in the flash tank 40 and the piping system connected thereto (specifically, in the piping 42, the piping 43, and the piping 53) is pushed out of the system through the air vent valve 41. In the illustrated example, the air vent valve 41 is attached only to the flash tank 40, but it may be attached to the pipe 42, the pipe 43, the pipe 53, etc. in order to enhance the exhaust effect. The vapor pressure introduced into the flash tank 40 is sufficient if the system can be set to a positive pressure, and a high pressure such as 0.8 MPaG is unnecessary, and the pressure reducing valve 16 is operated to adjust the pressure to 0.1 to 0.2 MPaG. It is sufficient to introduce as a degree.

  After confirming that a positive pressure has been established in the system by supplying a predetermined amount of steam with a pressure gauge or the like appropriately disposed, the on-off valve 17 is closed, and in that state, the system waits for the steam in the system to condense. . As the vapor condenses in the closed system, the pressure in the system drops to a negative pressure (below atmospheric pressure). If necessary, repeat this air venting operation about 2 to 3 times to confirm that the air has sufficiently escaped (for example, confirm that the pressure in the system is about −50 to −90 kPaG). ). Thereafter, the on-off valve 17 attached to the first branch pipe 14 is kept closed. In addition, mixing of drain water discharged from the first heat load device 30 generated during this air venting operation (preparation step for bringing the closed system into a negative pressure state) and flush steam of the same pressure generated from the drain water. The fluid flows out of the return pipe 23 through the bypass pipe 24 and does not flow into the flash tank 40. Further, during the air venting operation (preparation step for setting the closed system in a negative pressure state), the air heater 50 which is an example of the second heat load device may be operated. The condensation of the vapor in the system proceeds more rapidly.

  After closing the on-off valve 17, the on-off valve 33 attached to the drain pipe 31 is opened, and the on-off valve 25 attached to the bypass pipe 24 is closed. As a result, the high-pressure high-temperature drain discharged from the first heat load device 30 and the mixed fluid of the same-pressure flash vapor generated from the drain flow into the flash tank 40. The inside of the flash tank 40 has a negative pressure due to the preparation process for making the closed system in a negative pressure state as described above, and the flash rate increases as compared with the case of the positive pressure. The temperature of the first drain water after the separation is also lower than 100 ° C.

  The flash steam generated in the flash tank 40 passes through the pipe 42 that is also maintained under a negative pressure, and heat is recovered by exchanging heat with air in the air heater 50 that is an example of the second heat load device. Is done. The inside of the pipe 42 is maintained at a negative pressure, and there is no obstacle to the flow of the flash steam, and high heat recovery from the flash steam is also achieved in the air heater 50. The flash steam that has lost its latent heat by heat exchange condenses and becomes second drain water at 100 ° C. or lower.

  The first drain water generated in the flash tank 40 passes through the pipe 43 and the steam-driven trap 60A, and the second drain water condensed by passing through the air heater 50 is the pipe 53 and the steam-driven trap. After passing through 60B, it flows into the return pipe 23 as described above, and is collected in the water supply tank 20 opened to the atmosphere. Both the first drain water and the second drain water have a temperature of 100 ° C. or less, and no flash vapor (white smoke) released to the atmosphere when flowing into the water supply tank 20 is generated. .

[Drain recovery facility A1 operation method-selection 2]
The following method can also be selected as the operation method of the drain recovery facility A1. That is, in the selection of the operation method described above, high-pressure steam generated in the boiler 10 flows into the first heat load device 30, and the first heat load device 30 generates from drain water and drain water. However, the on-off valve (not shown) is provided immediately upstream of the first heat load device 30 and the on-off valve is closed (that is, the The above-described air venting operation (preparation process for making the closed system in a negative pressure state) may be performed in a state where high-pressure steam generated in the boiler 10 does not flow into the heat load device 30 of one. After the required negative pressure state is established in the system, the on-off valve 17 provided in the first branch pipe 14 is kept closed, and the on-off valve (not shown) is opened, so that the first heat load device 30 is opened. High-pressure steam generated in the boiler 10 is introduced into the inside.

  When this operation method is selected, the on-off valve 33 attached to the drain pipe 31 is kept normally open, and the on-off valve 25 attached to the bypass pipe 24 is kept normally closed. When this operation method is selected, the on-off valve 33 attached to the drain pipe 31, the bypass pipe 24, and the on-off valve 25 attached thereto can be omitted from the drain recovery facility A1.

[Second Embodiment]
Next, with reference to FIG. 2, a drain recovery facility A2 according to a second embodiment of the present invention will be described. The drain recovery facility A2 according to the second embodiment has a high-temperature air utilization unit 52 in FIG. 1 into which air heated by heat exchange with flash steam flows in the air heater 50 that is the second heat load device. 2 differs from the drain recovery facility A1 according to the first embodiment in that it is a combustion air heating device of the boiler 10. In this aspect, since the air heater 50 functions as an air preheater, it will be referred to as an air preheater 50 below. Other configurations and operations during operation are the same as in the case of the drain recovery facility A1, and the corresponding members are denoted by the same reference numerals, and description thereof is omitted.
In the drain recovery facility A2, the heat recovered from the flash steam is used as a part of the steam generation heat of the boiler 10 which is a steam generator, and the thermal efficiency as the boiler can be improved.

[Other embodiments]
Although not shown, as a means for generating a negative pressure in the closed system from the flash tank 40 to the second heat load device 50, in the first and second embodiments, the first branch pipe 14 and Although the means comprising the pressure reducing valve 16 and the on-off valve 17 arranged in the above, and the air vent valve 41 attached to the flash tank 40 or the like is shown, the means for generating the negative pressure in the closed system is not limited to this. Alternatively, for example, a means for degassing the system to a negative pressure using a vacuum pump may be used. In the case of using a vacuum pump, after the required negative pressure is established in the closed system by operating the vacuum pump, the first heat load device is installed in the closed system that has become negative pressure. The operation of the drain recovery facility is started by introducing the generated drain and stopping the operation of the vacuum pump.

  Moreover, although the one air preheater 50 was shown as a 2nd heat load apparatus, the 2nd heat load apparatus may be comprised by the 2 or more air preheater 50 arrange | positioned in series or in parallel. Naturally, as described above, not only the air preheater 50 but also heat exchange means such as hot water heating and feed water preheating may be used.

[Examples and Comparative Examples]
Next, the superiority of the present invention will be described with reference to examples and comparative examples. The inventors conducted an experiment using the drain recovery facility A1 shown in FIG. FIG. 3 shows the drain recovery facility A1 in which the experiment was performed, and the pressure and temperature were measured by placing an appropriate number of pressure gauges P and thermometers T at appropriate positions.

In FIG. 3,
P1: Pressure gauge for measuring internal pressure (measured value is gauge pressure),
T2: a thermometer for measuring the temperature in the flash tank 40,
T3: a thermometer for measuring the temperature of the flash steam immediately before flowing into the air preheater 50,
T4: a thermometer for measuring the temperature of hot water flowing in the return pipe 23,
T5: a thermometer for measuring the temperature of the ambient air flowing into the air preheater 50, and
T6: A thermometer that measures the temperature of air after being preheated (heated) by the air preheater 50.

  In the experiment, the high-pressure high-temperature drain from the first heat load device 30 was set to introduce a 120 ° C. drain into the flash tank 40 in an amount of 500 kg / h. In addition, the experiment was performed in Test 1 (Comparative Example): a test in which high-pressure and high-temperature drain was introduced into the flash tank 40 without venting air from the above-described system. Later, three tests were conducted: a test in which air was vented and the experiment was continued, and a test 3 (Example): a test in which high-pressure and high-temperature drain was introduced into the flash tank 40 after venting. And the scale of the said pressure gauge and thermometer in each elapsed time was read about each. The results are shown in Tables 1-3.

[Experiment details]
Test 1 (comparative example) (experiment in which no air was evacuated from the system) was started by immediately introducing the high-pressure and high-temperature drain into the system after the conditions for the high-pressure and high-temperature drain were satisfied. In Test 2 (Comparative Example), the gas in the system (which was in a pressurized state) was discharged (purge out air) 70 minutes after the start of Test 1, and the subsequent situation was confirmed. Since the air was in a pressurized state, the on / off valve in front of the air vent valve was opened to activate the air vent.

  In Test 3 (Example), the above-described air venting process was performed in 10 minutes per cycle, and this was repeated for 3 cycles to evacuate the system (in a state where air was deaerated below atmospheric pressure), then high pressure and high temperature. Drain was introduced. One cycle of air venting introduces steam (steam depressurized to a low pressure) into the system, stops the introduction of steam when the temperature in the system reaches 105 ° C., condenses the steam, and the pressure in the system becomes − It was allowed to stand until it reached 0.05 MPaG.

[Evaluation]
As can be seen from Table 1, as in Test 1 (Comparative Example), the system pressure including the inside of the flash tank exceeds 100 kPaG unless the system is vented (depressurization to negative pressure). The temperature in the tank is also 100 ° C. or higher. Therefore, even after 70 minutes, the air temperature after air preheating does not rise, and the temperature of the first drain water coming out of the flash tank is 100 ° C. or higher. This means that the flash rate in the flash tank (the weight of the flash steam generated from the unit weight of drain) is small, and it is understood that sufficient heat utilization is not performed. Moreover, it turns out that the 1st drain water will be discharged | emitted to the water supply tank open | released to air | atmosphere, and it has also become an environmental load.

  If the pressurized part is exhausted after 70 minutes (extracting air) as in Test 2 (Comparative Example), the temperature of the air after passing through the air preheater gradually increases, but the system cannot be fully depressurized. For this reason, the temperature of the first drain water from the flash tank is around 100 ° C., and it cannot be said that sufficient heat utilization is still performed.

  As in Test 3 (Example), when high-pressure drain water was introduced after air venting, the temperature of the air after the air preheater increased greatly, and the system was kept in a vacuum, and the return drain water ( The temperature of the first drain water and the second drain water) can be maintained at 100 ° C. or lower. This means that the heat reuse of the high-pressure and high-temperature drain has proceeded effectively, and as a result, when the first drain water and the second drain water are discharged into the water supply tank open to the atmosphere. Since it is possible to avoid the generation of flash vapor (white smoke) released into the atmosphere, an environmentally friendly drain recovery facility can be obtained. From these, the superiority of the present invention is proved.

A1 ... Drain recovery equipment according to the present invention,
10 ... Boiler,
12 ... Steam header,
13 ... Steam piping,
14 ... 1st branch piping,
15 ... Second branch pipe,
16 ... pressure reducing valve,
17 ... open / close valve,
18 ... pressure reducing valve,
20 ... Water tank,
23 ... Return piping,
24. Bypass piping,
25. Open / close valve,
30 ... first heat load device,
31 ... Piping (high-pressure high-temperature drain piping),
32 ... Trap,
33 ... Open / close valve,
40 ... Flash tank,
41 ... Air vent valve,
42 ... Piping (pipe for flash steam)
50: an air heater or an air preheater as an example of the second heat load device,
51. Duct,
52 ... High temperature air utilization part.

Claims (7)

A steam generator, a first heat load device that uses steam generated by the steam generator, and drains generated from the first heat load device are re-evaporated into flash steam and first drain water. It passes through a flash tank for separating air and water, a second heat load device using the flash steam generated in the flash tank, a first drain water generated in the flash tank, and the second heat load device. A drain recovery facility comprising a drain water recovery tank for recovering the second drain water in which the flash vapor is condensed,
The drain recovery facility is configured to maintain the piping system in a closed system, and further includes means for generating a negative pressure in the closed system from the flash tank to the second heat load device. Drain collection equipment characterized.   2. The drain recovery facility according to claim 1, wherein the means for generating a negative pressure in the closed system includes a steam introduction means for introducing the steam generated by the steam generator into the closed system and the closed system. The system is equipped with an air vent valve that discharges the air inside the system outside the system, and by introducing steam into the closed system, the air inside the system is expelled from the air vent valve to fill the system with steam, and heat is dissipated. A drain recovery facility characterized in that a negative pressure is formed in a closed system by condensing steam in the system.   3. The drain recovery facility according to claim 1, wherein the second heat load device heat-exchanges the environmental air or appropriate heating air for production to heat the environmental air or reheats the heating air for production. A drain recovery facility characterized by being an air heater.   The drain recovery facility according to any one of claims 1 to 3, wherein the drain water recovery tank is a water supply tank to the steam generator.   5. The operation method of the drain recovery facility according to claim 1, wherein a negative pressure is generated in the closed system by operating a means for generating a negative pressure in the closed system. The drain recovery facility is operated by introducing the drain generated in the first heat load device into the closed system that has become a negative pressure by performing the preparation step. A method for operating a drain recovery facility, characterized by starting the operation.   A heat utilization system using the drain recovery facility according to claim 3 or 4, wherein an air heater which is the second heat load device is used for preheating combustion air of an appropriate combustion device. Heat utilization system using drain recovery equipment.   5. The heat utilization system using the drain recovery facility according to claim 3, wherein the steam generator is a combustion-type boiler, wherein an air heater that is the second heat load device is the boiler. Heat utilization system using drain recovery equipment, which is used for preheating of combustion air for

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