JP2003279215A - Air cooling system and gas turbine power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air cooling system wherein the economical efficiency is enhanced, while restraining increase in pressure loss. <P>SOLUTION: A heat exchanger system for cooling air includes a first heat exchanger system and a second heat exchanger system, the first heat exchanger system is composed of heat exchangers 70a, b, and the second heat exchanger system is composed of a heat exchanger 71. A heat exchanger 70 is switched between defrosting operation and cooling operation by a four-way valve 72, the air passages of the heat exchangers 70a, b are connected in series, and the passages of an LNG are connected in parallel. In the first heat exchanger system, air is cooled to -40 to -70°C, and in the second heat exchanger 71, the air is cooled to about -130°C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an air cooling system for reducing compression power and liquefaction power of air, a heat exchanger therefor, and a gas turbine power generation system.

[0002]

In Japanese Patent Laid-Open No. 2001-116198, a liquid refrigerant such as mixed alcohol cooled by liquefied natural gas (hereinafter referred to as LNG) is circulated and air is indirectly cooled by an air cooler. Is listed. In order to suppress frost formation inside the air cooler, an air precooler and drain separator for precooling the air to condense the water upstream of the air cooler, and cooling to a lower temperature to reduce the water content It is proposed to install a deicer. In this known example, by switching the flow paths of the ice accumulators installed in parallel, a heated liquid refrigerant is used as a heat source,
It presents a method of melting the water that has frozen inside.

Further, Japanese Patent Laid-Open No. 2001-289057 discloses an LN.
An air cooling method for performing intake air cooling of a gas turbine using G has been proposed. In this known example, as a measure against condensation and solidification of moisture in the air, heat exchangers are connected in series, and one of the heat exchangers on the upstream side of the air flow melts frost due to the heat of the air itself. -The other heat exchanger, which is removed and is on the downstream side, cools the air by the cold heat of LNG. If moisture frosts on the heat exchanger on the downstream side, by changing the connection order of these heat exchangers in the reverse order, cooling and defrosting of air are alternately performed in each heat exchanger,
Defrosting is done without the need for an external heat source.

[0004]

In the known example disclosed in Japanese Patent Laid-Open No. 2001-116198, since another refrigerant substance is used as a medium for heat exchange between air and LNG, L
In addition to the heat exchangers for NG and the liquid refrigerant, the heat exchangers for the liquid refrigerant and the air are required, which increases the quantity of equipment.

Further, in the known example described in Japanese Patent Laid-Open No. 2001-289057, although a simple structure does not use another refrigerant substance, the LNG at a low temperature of -162 ° C causes the air to reach a desired temperature (implemented). In the example, it is cooled to about -150 ° C. Since the two heat exchangers are connected in series,
The quantity of heat exchanger is about twice as large as that without switching, and the pressure loss of fluid is also about twice as large, which causes increase in equipment cost and operation cost. Immediately after the defrosting operation is started, air containing moisture flows back through the low temperature part in the heat transfer tube cooled to a temperature close to the temperature of LNG, which causes new frost formation and defrosting. The time required increases. This is also a factor that increases operating costs.

In view of the above problems of the prior art, it is an object of the present invention to provide an air cooling system for reducing the compression power and liquefaction power of air without increasing the equipment cost and the operating cost. . Another object of the present invention is to provide a heat exchanger having an advantageous shape for removing water and defrosting.
Another object is to provide a gas turbine power generation system using this cooling system.

[0007]

In order to achieve the above object, in the air cooling system of the present invention, the heat exchanger system for cooling air comprises a high temperature heat exchanger system and a low temperature heat exchanger system,
The high temperature heat exchanger system is piped to exchange heat between air to be cooled and a low temperature fluid supplied from the low temperature heat exchanger system, and the low temperature heat exchanger system is cooled by the high temperature heat exchanger system. Piping is performed to exchange heat between air and a low temperature fluid that is a cold heat source, and the high temperature heat exchanger system is composed of a plurality of heat exchangers configured to be switchable between defrosting operation and cooling operation. The air passages of the heat exchangers for the defrosting operation and the cooling operation are connected in series, and the passages of the low temperature fluid are connected in parallel.

Alternatively, the high temperature heat exchanger system is composed of a plurality of heat exchangers in which the flow paths of the low temperature fluid are connected in parallel, and the plurality of heat exchangers have a valve mechanism according to the operating conditions. By switching, it is possible to select and partition the first heat exchanger group and the second heat exchanger group in any combination, and to select and partition the air flow path of the first heat exchanger group. The air passages of the second heat exchanger group are characterized by being piped so that they can be connected in series with each other.

Further, it is characterized in that the temperature of the air supplied from the high temperature heat exchanger system to the low temperature heat exchanger system is in the range of −45 to −70 ° C.

The fact that the air outlet temperature of the high temperature heat exchanger system is set within the above range is a finding obtained from the experiments by the inventors. According to this, the air is heated in the high temperature heat exchanger system at −45 to −70 ° C.
Since it is cooled down to about −150 ° C. in the low temperature heat exchanger system, the pressure loss in the heat exchanger is small and the operating cost can be reduced. Also, the time required for defrosting is shortened.

The heat exchanger of the present invention which achieves the above object,
A heat transfer tube group configured by a plurality of heat transfer tubes that circulate a low-temperature fluid, a heat transfer fin that is installed on an outer surface of the heat transfer tube and exchanges heat with air, a body that houses the heat transfer tube group, and the heat transfer tube. A tube plate installed at each end of the group and holding each end, and a baffle plate installed so as to form a flow path of water generated in the heat exchanger in the space inside the body. It is characterized by According to this, it becomes possible to remove the water generated inside the heat exchanger.

[0012]

FIG. 2 shows an embodiment of a gas turbine power generation system including an air cooling system according to the present invention. This system is a compressor 51 that compresses air into high pressure,
A combustor 5 that combusts compressed air and a fuel 50 such as LNG, and a gas turbine 7 that is driven by expansion of high-temperature and high-pressure combustion gas are provided. Further, a generator 8 arranged on the same axis as the gas turbine 7 and a regenerative heat exchanger 9 for recovering heat of exhaust gas of the gas turbine 7 are provided.

The characteristic component of this embodiment is the air cooling system. That is, there is an air blower 80 that pressurizes the air introduced from the air introduction pipe 42, and a four-way valve 72 that switches and supplies the air sent from the blower 80 to the heat exchangers 70a and 70b on the downstream side. Depending on the position of the four-way valve 72, the heat exchanger 7 heats the heat exchanger with the air supplied from the air blower 80 to defrost or cools the air with low temperature natural gas supplied from the heat exchanger 71 described later.
There are 0a and 70b. Further, depending on the position of the four-way valve 72, a water separator 81 for collecting water removed from the air flow path of the heat exchanger 70a or 70b, LNG supplied from the LNG storage tank 43 via the pipe 40, and four-way There is a heat exchanger 71 for exchanging heat with the dry air supplied from the valve 72. The heat exchangers 70a and 70b are heat exchangers of a system which will be described later with reference to the drawings, and the heat exchanger 71 is preferably a compact one such as a plate fin system heat exchanger.

In the flow path of natural gas (hereinafter referred to as NG) that has exchanged heat with the heat exchanger 71, adjusting valves 78a and 78b are provided.
Is installed, and the heat exchanger 70a is installed depending on the operating conditions.
And 70b, the flow rate of NG supplied to each of them can be independently set. The NG that has exchanged heat with the heat exchanger 70a or 70b is sent to the facility using NG by the natural gas flow path 19 via the check valve 79a or 79b. The check valve 79 is provided to prevent the temperature of the heat exchanger from rising and the internal pressure of the heat transfer tube to rise when the supply of NG is stopped by switching the operation mode.

In addition, a temperature sensor 84 for measuring the temperature of the air supplied to the heat exchanger 71, a control circuit 83 for generating a signal for controlling the flow rate of LNG based on a signal from the temperature sensor 84, and a pipe 40. A control valve 85 for controlling the flow rate of LNG in response to a signal from the control circuit 83 is provided. Further, the bypass valves 90a and 90b installed in the middle of the pipe connecting the inlet and outlet of the air passages of the LNG heat exchangers 70a and 70b, and the inlet and outlet of the air passages of the LNG heat exchangers 70a and 70b. Differential pressure gauges 86a and 86b for respectively measuring the differential pressure are provided.
In addition, an adjustment valve 76a that adjusts the air flow rate of the heat exchanger 70
76b, and a condensed water tank 46 for guiding the water separated by the water separator 81 through the condensed water pipe 47 and temporarily storing the water.

Further, although not shown in FIG. 2, the heat exchangers 70a and 70b have drainage pipes 16 for draining condensed water generated in the heat exchangers and water melted in the defrosting operation.
Is provided, and the drainage is configured to be treated in the same manner as the condensed water in the condensed water tank 46.

In this embodiment, the switching of the four-way valve 72 is such that the headers 73a and 73b communicate with each other and the headers 73c and 73d communicate with each other, and the heat exchanger 70a operates in the defrosting operation mode. It shows a case where 70b operates in the cooling operation mode.

FIG. 1 is an explanatory view showing an outline of an air cooling system according to the present invention and a switching operation between defrosting and cooling. 1 (A) and 1 (B), the details of the adjusting valves 76a and 76b, the bypass valves 90a and 90b, and the temperature sensor 8 are shown.
4, the description of the parts that commonly operate in each operation mode, such as the control circuit 83 and the gas turbine, is omitted.

(A) shows the case where the left heat exchanger 70a is in the defrosting operation and the right heat exchanger 70b is in the cooling operation. The four-way valve 72 is switched to the direction shown in the drawing, and hot air flows through the heat exchanger 70a to perform the defrosting operation. At this time, the regulating valve 78a is closed and NG, which is a low temperature fluid, does not flow to the heat exchanger 70a, so that defrosting is efficiently performed. On the other hand, the heat exchanger 70b is the heat exchanger 7
The air discharged from 0a and the NG discharged from the heat exchanger 71 are adjusted valve 78.
It flows through b and heat exchange is performed. The heat-exchanged low-temperature air flows through the other of the four-way valve 72 as shown in the figure, and is heat-exchanged with the LNG in the heat exchanger 71.

(B) is a case where the left heat exchanger 70a is in the cooling operation and the right heat exchanger 70b is in the defrosting operation. When the four-way valve 72 is switched as shown in the figure, the flow of air to the heat exchangers 70a and 70b is opposite to that in the case of (A), and the regulating valves 78a and 78b are also switched so that the NG heat exchanges from the regulating valve 78a. Flows to the vessel 70a.

FIG. 3 shows a schematic view of a heat exchanger according to an embodiment of the present invention. In the figure, (A) defrosting operation mode and (B) cooling operation mode are shown separately according to the operating condition of the heat exchanger 70, and the direction of the fluid in each state is shown by an arrow.

The heat exchanger 70 includes a steel shell 30 for accommodating a plurality of copper alloy heat transfer tubes 24 for flowing NG, and a steel tube sheet 27 for collecting the tube ends of the plurality of heat transfer tubes 24. It is composed of a steel lid 32 and the like. On the outer surface of the heat transfer tube 24, a plurality of aluminum alloy plate-shaped fins 22 each having a surface in a direction perpendicular to the tube axis are attached. Steel baffle plates 31 are arranged in the plate fins 22 at appropriate intervals. The baffle plate 31 is shown in FIG.
As shown in (B) and (B) respectively, the air supplied from the nozzle 11b or 11a forms a flow path while meandering in the body 30 along the surface of the plate-shaped fins.
It has an opening that allows it to flow toward the nozzle 11a or 11b.

In the present embodiment, the pedestal 13 which supports the side surface of the shell 30 of the heat exchanger 70 by inclining the side surface of the shell 30 so as to be upward by about 5 degrees with respect to the traveling direction of the air in the cooling operation mode (B). Has been installed. Inside the lower side surface of the inclined body 30, the water passage 17 formed through the gap between the baffle plate 31 and the body 30 and communicated with the lower space of the water passage 17 is condensed or melted inside the body 30. There is a drainage pipe 16 for extracting water to the outside. The inclination of the body 30 is shown in FIG.
In the operation mode of (A), the direction of the air flow is reversed, so the direction of air flow is about 5 degrees downward.

FIG. 4 shows a sectional view of the body 30 of the heat exchanger 70 taken along a plane parallel to the baffle plate 31. Water channel 17
Is the moisture attached to the inner wall surface of the body 30 due to gravity.
It is a route that can move to the bottom of 0. For example, as shown in FIG. 4A, the water flow path 17 may be provided as a gap on the entire boundary surface between the baffle plate 31 and the inner surface of the body 30, or as shown in FIG. The water flow path 17 may be provided as a notch in the plate 31.

A method of manufacturing the heat transfer element portion of the heat exchanger 70 will be described below. When the heat transfer tube 24 is made of a copper alloy, the plate-shaped fin 22 that is pre-drilled on the outer surface of the heat transfer tube 24.
The baffle plate 31 is fitted and the heat transfer tube is mechanically expanded or hydraulically expanded to join the fin and the heat transfer tube and the baffle plate and the heat transfer tube, respectively. Further, unlike the present embodiment, when a stainless steel heat transfer tube is used, for example, it is difficult to expand the tube due to the nature of the material. Therefore, it is also possible to manufacture the plate-shaped fins 22 that have been pre-drilled on the outer surface of the heat transfer tube by sequentially press-fitting them from the tube end. In this case, the hole shape of the plate-shaped fins 22 is designed to facilitate press-fitting.
It is desirable to have elasticity such as making a notch.

The baffle plate 31 is similarly drilled. However, since the baffle plate 31 is installed to limit the direction of the flow in the body and heat conduction is not always necessary, the hole of the baffle plate 31 has elasticity. A flexible rubber or packing such as Teflon (registered trademark) may be installed. In that case, airtightness can be improved. The advantage of using stainless steel heat transfer tube is that it has better corrosion resistance than copper alloy,
The service life can be extended. On the other hand, since the heat transfer coefficient of stainless steel is smaller than that of copper alloy, the overall heat resistance increases, the required heat transfer area increases, and the heat exchanger tends to increase in size.

Next, the operation of this embodiment will be described. The outside air from which dust and the like have been removed by a filter (not shown) is introduced from the air introduction pipe 42, and the air blower 80 causes the outside air to reach 0.
Pressurized to 13 MPa. The reason for pressurizing to this extent is to overcome the pressure loss in the heat exchangers 70 and 71 installed downstream and to stably supply the outside air. As a result, the temperature of the air is:
The internal energy increased due to the compression, 50
It rises to about ℃.

In the state of the four-way valve 72 shown in FIG. 2, the heat exchanger 70a operates in the defrosting operation mode.
b shows the case of operating as a cooling operation mode,
Air flows in the direction from the headers 73a to 73b. The bypass valve 90a, the adjusting valve 76a, and the adjusting valve 78a of the heat exchanger 70a are in the following three states (1) to (3) in the defrosting operation mode.

That is, (1) in the defrosting operation mode, when frost or dew condensation occurs in the air passage of the heat exchanger 70a, the bypass valve 90a is closed and the adjusting valve 76 is closed.
a is opened, and the adjusting valve 78a that controls the supply of NG is also closed. As a result, only the air having a temperature of about 50 ° C. is supplied to the heat exchanger 70a, and the operation of melting the frost in the flow path and drying the dew condensation is performed. (2) In the defrosting operation mode, when the defrosting and the drying are completed, the adjustment valve 76a is closed, the bypass valve 90a is opened, and the adjustment valve 78a is closed, so that the pressure loss in the air flow path is reduced. And air of about 50 ° C. is supplied to the heat exchanger 70b in the cooling operation mode.
(3) Immediately before switching from the defrosting operation mode to the cooling operation mode, the adjusting valve 78a remains closed and the bypass valve 90a remains open, and the adjusting valve 78a is opened as much as necessary. As a result, the heat exchanger equipment is pre-cooled by the cold heat of the low temperature NG, and the cooling of the air can be immediately started when the cooling operation mode is switched to.

In the defrosting operation mode, the internal operation of the heat exchanger 70a in the state (1) where defrosting is actually performed will be described in detail with reference to FIG. Nozzle 11b
The air having a temperature of about 50 ° C. flowing in from the baffle plate 3
In the process of passing through the flow path divided by 1, heat is exchanged with the frosted surface of the fin 22 by forced convection heat transfer. Heat transfer tube 24
Since the adjustment valve 78a is closed in the inside, NG does not flow, and the temperature of frost on the fin 22 rises with the passage of time, and melts when the temperature approaches 0 ° C. A part of the melted liquid film flows down toward the lower surface of the inner wall of the body 30 due to gravity and reaches the water channel 17. The remaining liquid film receives a volume force from the air flow to become droplets, and flows together with air.
Since the flow path divided by the baffle plate 31 meanders,
The droplet having a higher density than that of air has a relatively large radius of gyration in the swirling portion of the flow path, collides with the inner wall surface of the body 30, and becomes a liquid film again. The liquid film that has reached the inner wall surface of the body 30 flows down along the inner wall surface of the body 30 due to gravity, and reaches the water flow path 17 also on the lower surface of the inner wall of the body 30. Due to gravity, the water in the water flow path 17 flows toward the drainage pipe 16 installed in the lower portion of the body 30 and is discharged to the outside.

The progress of defrosting the fins 22 is measured by the differential pressure gauge 8
The judgment is made by measuring the pressure loss in the air flow path at 6a. That is, if the pressure loss increased due to frost falls to the level before frost formation, it can be determined that frost formation has been removed. After the frost formation on all the fins 22 is removed, the inside of the body 30 is dried by flowing air at a temperature of about 50 ° C. After the drying is completed, the heat exchanger 70a is bypassed by operating the valve in the state of (2) to reduce the pressure loss, thereby saving the power of the blower. Immediately before switching from the defrosting operation mode to the cooling operation mode, the adjustment valve 76a, the adjustment valve 78a, and the bypass valve 90a are operated to bring them to the state of (3), and the heat of the heat exchanger equipment is pre-cooled by the cold heat of the low temperature NG. I do.

In the defrosting operation mode, the liquid droplets that cannot be completely removed from the drainage pipe 16 of the heat exchanger 70a due to the above-mentioned action are discharged together with the air and discharged from the nozzle 11a. The droplets are separated by the water separator 81 installed in the air outlet pipe and collected from the condensed water pipe 47 to the condensed water tank 46. The air from which the liquid droplets have been removed is supplied to the heat exchanger 70b operating in the cooling operation mode and undergoes countercurrent heat exchange with NG of about -80 ° C supplied from the adjusting valve 78b, and the air is -50. It is cooled to about ℃.

The heat exchanger 70 in this cooling operation mode
The internal operation of b will be described in detail with reference to FIG.
The moist air having a maximum temperature of 50 ° C. and a maximum relative humidity of 100% flowing from the nozzle 11a is forcibly convection cooled by the fins 22 that are cooled by the low temperature NG flowing in the heat transfer tube 24. In the process of passing through the flow path partitioned by the baffle plate 31, as the temperature of the air becomes lower than the dew point, dew condensation occurs and adheres on the heat transfer surface. When the dew condensation grows, it becomes a liquid film, and part of the liquid film flows down toward the lower surface of the inner wall of the body 30 due to gravity and reaches the water flow path 17. The remaining part of the liquid film receives a volume force from the air to become a droplet, which flows together with the air. Since the flow path divided by the baffle plate 31 meanders, the droplet having a higher density than air has a relatively large radius of gyration in the swirling portion of the flow path. Most of the droplets collide with the inner wall surface of the body 30, again form a liquid film, flow down along the inner wall surface of the body 30, and reach the water channel 17 also on the lower surface of the inner wall of the body 30.

The water in the water flow path 17 is discharged to the outside from the drainage pipe 16 as in the case described with reference to FIG.
The difference from the case of FIG. 3 (A) is that the direction of the air flow and the direction of the water flow are opposite, so when the air flow velocity inside the body 30 is very high, the surface of the water in the water flow passage 17 is different. Is subjected to shearing force and may flow upward against the inclination. Under such conditions, most of the condensed water can be removed by increasing the inclination of the body 30 or by installing a plurality of drainage pipes 16 in the flow direction of the body 30.

Further cooling of the air proceeds along the flow,
As the temperature becomes lower than the freezing point of water, moisture frosts on the surface of the heat transfer surface, and air is gradually cooled and dehumidified. Comparing this condensation process with the frost formation process, most of the water contained in the air is removed in the condensation process due to the nature of the saturation pressure curve of water. By effectively collecting the condensed water by the action of the baffle plate 31, the amount of water to be frosted can be suppressed to the minimum, and the air cooling operation for a long time becomes possible.

The reason why the air is cooled to −45 ° C. or lower by the heat exchanger 70b is that most of the water is frosted and removed by cooling to this temperature range.
The inventors conducted an experiment in which two heat exchangers were connected in series and the air containing moisture was cooled by low temperature liquid nitrogen. The two heat exchangers correspond to the heat exchanger 70b and the heat exchanger 71 of this embodiment, respectively. When the air outlet temperature Ta of the upstream (high temperature) side heat exchanger is changed by fixing conditions such as air inlet temperature, humidity, flow rate, and pressure and adjusting the flow rate of liquid nitrogen in this connection form. The pressure loss of the air flow path of the heat exchanger on the downstream (low temperature) side of was measured.

FIG. 6 shows the rate of increase in pressure loss in the downstream (low temperature) side heat exchanger. The horizontal axis of the figure is the elapsed time after the start of cooling operation, and the vertical axis is the ratio of the pressure loss after the elapse of time to the pressure loss at the start of cooling. According to FIG. 6, when the air is cooled to −10 ° C. in the upstream heat exchanger, the increase rate of the pressure loss in the air passage of the downstream heat exchanger is high, and 1 hour has elapsed since the cooling was started. Later, the pressure loss will be 1.4 times or more of the original pressure loss. On the other hand, when the heat exchanger on the upstream side cools to −55 ° C., the pressure loss of the heat exchanger on the downstream side is almost constant even after 2 hours or more.

Using the results of this experiment, the thickness of frost formed on the inside of the heat transfer surface per unit time was arranged and calculated by the temperature of the air supplied to the heat exchanger on the downstream side. Using the result,
The rate of increase in pressure loss of the downstream heat exchanger when the cooling operation was continued for 8 hours was derived.

FIG. 7 shows the rate of increase in pressure loss in the downstream heat exchanger. According to this, if air is cooled to −45 ° C. in the upstream heat exchanger and frost is formed, even if cooling is continued for 8 hours, the increase in pressure loss in the downstream heat exchanger is doubled. It is weak. Furthermore, when the air is cooled to −55 ° C., the increase in pressure loss is about 1.1 times, and heat exchange can be maintained without causing blockage or the like. Therefore,
In the configuration of the present embodiment, the temperature at which the air is cooled by the heat exchanger 70 is -50 ° C, which is a value of -45 ° C or less.

If the temperature of the air cooled by the heat exchanger 70 is further lowered, the removal of water becomes more reliable.
However, in order to cool to a lower temperature, more heat transfer area of the heat exchanger 70 is required, and since the heat exchanger 70 is connected in series to the air flow, an increase in pressure loss and heat There is concern that this may lead to an increase in the equipment cost of the exchange.

In order to investigate the relationship between the temperature at which air is cooled by the heat exchanger on the upstream side (for high temperature) and the pressure loss of the entire heat exchanger, the pressure loss was calculated based on the experimental results. The boundary conditions used for the calculation are shown in FIG. Air at 50 ° C. is cooled to −130 ° C. by an upstream (high temperature) heat exchanger and a downstream (low temperature) heat exchanger. At that time, in the high temperature heat exchanger, it was assumed that a pressure loss of 0.1 kPa would occur for cooling the air by 1 ° C. Further, in the heat exchanger for low temperature, the density of air becomes high and the flow velocity becomes low.
It was assumed that a pressure loss of 0.05 kPa would occur for cooling at 0 ° C. Further, in the high temperature heat exchanger, the operation control for switching between the dehumidifying and cooling heat exchangers was considered when the pressure loss due to frost became 2.5 times the initial value. As the pressure loss of the low temperature heat exchanger, the result examined in FIG. 7 based on the experimental result was used.

Due to these boundary conditions, the pressure loss of the upstream (high temperature) heat exchanger and the downstream (low temperature) heat exchanger as a function of the temperature of cooling the air in the upstream (high temperature) heat exchanger. FIG. 9 shows the result of calculation of the total value of the pressure loss of.

When the temperature for cooling the air in the upstream (high temperature) heat exchanger is about -30 ° C., the pressure loss during frost formation in the downstream (low temperature) heat exchanger is large, and the total pressure is reduced. The loss is about 80 kPa. When the air is cooled to −50 ° C., the increase in pressure loss due to frost formation on the downstream side (for low temperature) heat exchanger is very small, and the overall pressure loss is 40%.
It becomes about kPa. However, if the upstream side (for high temperature) heat exchanger cools the air to a lower temperature, the upstream side heat exchanger is connected in series with the air and the pressure loss of the air is large, so the overall pressure loss increases. Tend to do. Therefore, there is an optimum value for the temperature at which the air is cooled in the heat exchanger on the upstream side. The range is -45 as shown in FIG.
It is in the range of ° C to -70 ° C. In this temperature range, the total pressure loss can be suppressed to 44 kPa or less.

FIG. 10 compares the pressure loss on the air side by the heat exchanger 70 and the heat exchanger 71 and the effect of reducing the air compression power by utilizing the cold heat of LNG. The horizontal axis of the graph is the pressure loss on the air side, and the vertical axis is based on the power of the compressor 51 that can be reduced by utilizing LNG cold heat, and subtracts the power increase of the air blower 80 due to the increase of the pressure loss. .

According to FIG. 10, when the total pressure loss of the heat exchangers 70 and 71 is 44 kPa, the compression power reduction effect is 0.78 times. When the pressure loss of the heat exchanger increases, the compression power reduction effect shown in the figure becomes smaller than this value. From the above, the optimum range of the temperature for cooling the air by the heat exchanger 70 is −45 to −70 ° C.

Air is changed from -45 to-by the heat exchanger 70b.
In order to surely cool to a temperature in the range of 70 ° C., control is performed by the control circuit 83 shown in FIG. 2 in this embodiment. The temperature sensor 84 detects the temperature of the air that has been heat-exchanged by the heat exchanger 70, and if the detected temperature is higher than the target temperature, the opening degree of the adjustment valve 85 is increased to increase the flow rate of the low temperature NG. The temperature difference of the heat exchange fluid inside the heat exchanger 70 is increased to increase the exchange heat amount. If the detected temperature is lower than the target temperature, perform the reverse operation. By such control, it is possible to reliably cool the air to a temperature in the range of −45 to −70 ° C. and prevent an increase in pressure loss due to frost formation on the heat exchanger 71.

As another method, by designing the heat exchange capacity of the heat exchanger 70 and the heat exchanger 71, the temperature of the air discharged from the heat exchanger 70 is set to a predetermined value without controlling the flow rate and the like. It is also possible. That is, the flow rate of air to be cooled and the flow rate of LNG that is a low temperature heat source are fixed conditions. When the target temperature of the air discharged from the heat exchanger 70 is determined, the outlet temperature from the heat exchanger 71 is -130.
Since the temperature is determined to be ° C, the heat exchange amounts required for the heat exchanger 70 and the heat exchanger 71 can be obtained. From the heat balance between air and LNG, the LNG temperature at each inlet / outlet of the heat exchangers 70 and 71 is automatically determined, and the logarithmic average temperature difference between the fluids is obtained. The amount of heat exchanged by the heat exchanger is determined by the product of the logarithmic mean temperature difference between the fluids, the heat transfer coefficient, and the heat transfer area. Therefore, the product of the remaining heat transfer coefficient and the heat transfer area is inevitably determined. After all, the heat exchangers 70 and 71 are designed and manufactured so that the product of the heat transmission coefficient and the heat transfer area has a predetermined value, so that the temperature of the air exchanged in the heat exchanger 70 has a predetermined value. Become.

The dehumidified air cooled to −50 ° C. by the heat exchanger 70b is led to the heat exchanger 71 to which LNG of lower temperature is supplied via the headers 73d to 73c of the four-way valve 72. . In the heat exchanger 71, the LNG stored in the LNG storage tank 43 and having a temperature of about −160 ° C.
Is pressurized by a pump and supplied through the pipe 40 and the adjusting valve 85. The air is cooled to about −130 ° C. by exchanging heat with the LNG in a counterflow.

The low temperature air of about -130 ° C. is supplied to the compressor 51 via the pipe 41 and is compressed to about 15 atm by the action of the compressor 51. At this time, the air that has been cooled and has an increased density is compressed, so that it can be compressed with about half or less power as compared with the case of compressing air at room temperature to about 15 atm. The temperature of the compressed air rises up to about 70 ° C.
It is heated to about 0 ° C, and fuel 50 such as LNG is burned in the combustor 5.
Burn with.

In the gas turbine 7, the expansion force of the high-temperature and high-pressure combustion gas drives the generator 8 to generate electric power. Exhaust gas from the gas turbine 7 is subjected to heat recovery by the regenerative heat exchanger 9 and discharged from the stack 55 to the atmosphere.
Thus, by utilizing the cold heat possessed by the LNG, the power of the air compressor, which normally consumes 50 to 60% of the gas turbine output, can be greatly reduced, and as a result, the power generation output can be greatly increased.

The operation so far described is such that the state of the four-way valve 72 is the state of FIG. 1A, that is, the heat exchanger 70a operates in the defrosting operation mode and the heat exchanger 70b operates in the cooling operation mode. That was the case. If this operation mode is continued for a long time, frost will grow on the surface of the heat transfer surface of the heat exchanger 70b operated in the cooling operation mode, and adverse effects such as an increase in pressure loss and an increase in heat transfer resistance will increase. . In order to recover this, the four-way valve 72 is switched to the state shown in FIG. As a result, the air flow is changed to the heat exchanger 70a.
And the heat exchanger 70b can be set to be completely opposite, and the heat exchanger 70a is operated in the cooling operation mode,
The heat exchanger 70b can be operated in the defrosting operation mode.

The operation of the equipment at this time is as follows:
Read 70b, adjusting valves 76a and 76b, adjusting valve 7
8a and 78b, check valves 79a and 79b, differential pressure gauges 86a and 86b, and bypass valves 90a and 90b will be explained in the same manner. At this time, the intake operation by the air blower 80, the power generation operation by the air compressor 51, the gas turbine 7, etc. are the same regardless of the position of the four-way valve 72.

Further, although it is assumed in this embodiment that the four-way valve 72 is used, the same effect can be obtained by installing a plurality of simple stop valves in combination instead of the four-way valve 72. There is no end.

The switching of these operation modes is basically a preset switching time, and while monitoring the differential pressure gauge 86 installed in the air flow path of the heat exchanger 70, a control circuit (not shown) has been described above. This is done by automatically operating the valves. The optimum switching time interval can be selected from the viewpoints of facility cost reduction and operating cost reduction.

That is, in order to reduce the equipment cost, it is effective to increase the heat transfer area per unit volume of the heat exchanger 70 and make the heat exchanger compact. However, in that case, since the flow passage area of the air becomes small, the degree of narrowing of the flow passage area is large when frost is formed, and the pressure loss increases quickly. When the pressure loss increases rapidly, the switching time interval of the heat exchanger becomes short, so that the energy for defrosting, the energy for precooling, etc. will be large, the thermal efficiency of the system will decrease, and the operating cost will decrease. Is a factor that increases. On the contrary, if the heat transfer area per unit volume of the heat exchanger 70 is increased, the heat exchanger becomes expensive, but the increase in pressure loss becomes slower and the switching time interval becomes longer, so the system operating cost is increased. Will improve.

In this embodiment, a heat exchanger 70 for cooling air to -45 ° C. or lower and a heat exchanger 71 for cooling air to about −130 ° C. are connected in series, and the heat exchanger 70 is further connected.
Is a heat exchanger 70a and 7 in which the NG flow paths are connected in parallel.
It consists of 0b. The air flow paths of the heat exchangers 70a and 70b are connected in series by switching the connection order depending on the operating conditions, so that those connected on the upstream side are defrosted,
Those connected to the downstream side can be cooled.

According to this structure, cooling and defrosting can be performed simultaneously without separately preparing a heat source and a fluid required for the defrosting operation. Further, the heat exchanger 70 is the heat exchanger 7
Since the air passages of 0a and 70b are connected in series, compared with the case where only one heat exchanger is connected for cooling,
The pressure loss and the amount of necessary equipment are doubled. However, the lower limit of the cooling temperature of air by the heat exchanger 70 is set to −
Since the temperature is limited to 70 ° C., it is possible to suppress an increase in the pressure loss of the entire system and an increase in the required amount of equipment.

In this embodiment, the body 30 of the heat exchanger 70 is arranged slightly inclined (about 5 degrees) from the horizontal, but the body 30 of the heat exchanger 70 may be installed vertically.
FIG. 5 shows a schematic structure of a vertically arranged heat exchanger.
(A) shows the time of defrosting, (B) shows the time of cooling, and the arrow described has shown the flow direction of the fluid.

The operation inside the heat exchanger 70 having the configuration of FIG. 5 will be described. In the case of (A) defrosting, the air having a temperature of about 50 ° C., which has flowed in from the nozzle 11 a on the upper portion of the body 30, passes through the flow passages defined by the baffle plate 31, and the frosted surface of the fin 22. Heat is exchanged by forced convection heat transfer with. The frost formed on the fins 22 melts with the passage of time, reaches the inner wall surface of the body 30 as droplets, and forms a liquid film again. This liquid film flows downward in the water flow path 17 formed in the gap between the inner wall surface of the body 30 and the baffle plate 31 by the action of gravity. At this time, it is expected that a part of the air flowing through the body 30 will flow downward via the water flow path 17 without depending on the guide of the baffle plate. Due to the downward shearing force received from the air flow, the liquid film in the water flow path 17 flows downward while being accelerated. This moisture reaches the lower portion of the body 30 and is discharged to the outside from the drainage pipe 16 as in the case of the embodiment of FIG.

The operation at the time of cooling in FIG. 5B will be described. The moist air flowing in from the nozzle 11b in the lower part of the body 30 passes through the flow passages defined by the baffle plate 31, and condenses on the heat transfer surface to form a liquid film. This liquid film is the same as in the case of the embodiment described with reference to FIG.
Reach 7. Moisture in the water flow path 17 is absorbed by the body 30 due to gravity.
Receives a volume force that flows down the inner wall surface of the. On the other hand, the water flow path 17 is a bypass path in which a part of the air flowing through the body 30 flows upward against the guide of the baffle plate. However, the downward force by which the water drops due to gravity and the upward shearing force received from the air flow ensure a sufficiently large flow passage cross-sectional area of the water flow passage 17 so that the downward force by which the water falls due to gravity becomes large. Because
Moisture flows down. This moisture reaches the lower part of the body 30 and is discharged to the outside from the drainage pipe 16 installed in the lower part of the body 30, as in the case of the embodiment of FIG.

As described above, when the heat exchanger 70 is installed vertically, there is an advantage that the installation area of the heat exchanger can be made smaller than when it is installed horizontally.

In the embodiment shown in FIG. 5, the air is lowered during defrosting, and the air is raised during cooling. However, the fluid may be supplied in the opposite direction. In that case, during the cooling operation, the water condensed in the upper high temperature area is
When it flows down the water flow path 17 and reaches the lower temperature region, it may freeze below the freezing point of water, and water may not be discharged. On the other hand, in the case of flowing the fluid in the opposite direction of the embodiment of FIG. 5, since the direction of the NG flow is upward, the density of NG becomes lighter along with heat exchange, and the buoyancy causes the volume force to accelerate the flow. . Since a volume force acts on air even in the direction in which the flow is accelerated by gravity, there is a characteristic that an unstable event such as a backflow of a fluid is unlikely to occur.

Further, the heat exchanger 70 shown in FIG.
Although the embodiment of the type shown in (1) is shown, other types of heat exchangers can be used. At that time, when the moisture cannot be removed inside the heat exchanger, in the defrosting operation mode, the moisture generated as a result of defrosting becomes droplets and is separated by the moisture separator 81. In the cooling operation mode, since the dew condensation on the heat transfer surface is not discharged, the speed of frost formation is increased and the operation time is shortened. Therefore, when a heat exchanger that cannot remove water inside the heat exchanger is selected, it is desirable to add a dehumidifying mechanism that collects condensed water in the upper stage.

Further, in the present embodiment, a normal heat exchanger is assumed as the heat exchanger 71 used in the low temperature region, but the heat exchanger 71 should be a cold storage heat exchanger for storing latent heat or sensible heat. You can In that case, the influence of the flow rate fluctuation due to the fluctuation of the demand of the LNG used as the cold heat source can be mitigated, and the cold heat of the LNG can be used more effectively.

Another embodiment of the air cooling system according to the present invention will be described. FIG. 11 shows a block diagram of an air cooling system according to another embodiment. The present embodiment is applicable to a LNG cold heat utilization type gas turbine power generation system,
The air cooling system of the embodiment of FIG. 2 is similar to most of the embodiment, so only different parts will be described.

In the embodiment of FIG. 2, the heat exchanger 70 is 70a.
The heat exchanger 70 of the present embodiment is composed of three systems 70a, 70b and 70c. Further, in the embodiment of FIG. 2, the four-way valve 72
The direction of the air flowing in and out of each heat exchanger 70 was controlled by. On the other hand, in the present embodiment, the adjusting valves 76a, 76
b and 76c and stop valves 77a, 77b and 77c are installed, and 70a, 70
The direction of the air flow of the heat exchangers of three systems b and 70c is switched. At this time, the low temperature NG introduced from the heat exchanger 71
The flow rate of is adjusted by adjusting valves 78a, 78b, and 78c according to the operating state.

Further, in the embodiment of FIG. 2, the bypass valve 90 of the air flow path is separately attached to each heat exchanger system in the form of 90a and 90b. In this embodiment, the bypass valve 90z is installed together with the pipe connecting the downstream of the air blower 80 and the water separator 81,
Even when the number of systems in the defrosting operation mode is smaller than the number of systems in the cooling operation mode, it is possible to introduce a sufficient flow rate of air to the system in the cooling operation mode.

The operation of this embodiment will be described. Here, of the three heat exchangers 70, two are constantly operated in the cooling operation mode, and the remaining one is operated in the dehumidification operation mode.
In FIG. 11, the direction in which the fluid flows is indicated by an arrow. The flow of air is such that the adjustment valve 76a is in the open state and the adjustment valves 76b, 7
6c is closed, stop valve 77a is closed, stop valve 77
b and 77c are open. The air sent from the air blower 80 is introduced into the heat exchanger 70a, and the heat exchanger 7a
The air cooled by 0b and 70c is set to be supplied to the heat exchanger 71. Correspondingly, in the flow of NG, the adjusting valve 78a is closed and the adjusting valves 78b and 78
It is set to supply the low temperature NG discharged from the heat exchanger 71 only to the heat exchangers 70b and 70c by opening c as much as necessary. In this state, the heat exchanger 70a operates in the defrosting operation mode described in FIG. 2, and the heat exchangers 70b and 70c operate in the cooling operation mode.

The difference from the embodiment of FIG. 2 is that the bypass valve 9
The point is that the opening degree of 0z is adjusted and a part of the air sent from the air blower is directly supplied to the water separator 81 without passing through any heat exchanger. Therefore, the heat exchanger 70a
It is possible to supply a sufficient amount of air to the heat exchangers 70b and 70c and cool them while suppressing the pressure loss at the minimum. In addition, after the defrosting is completed in the heat exchanger 70a, the pressure loss can be reduced by closing the adjusting valve 76a and supplying all the air via the bypass valve 90z. Immediately before switching from the defrosting operation mode to the cooling operation mode, the operation of opening the adjusting valve 78a to introduce NG and precooling the heat exchanger 70a is the same as that in the embodiment of FIG.

Heat exchangers 70b and 70c in the cooling operation mode
The pressure loss increases as the frost builds up inside. Therefore, the adjusting valves 76a, 76b, 76c, the stop valves 77a, 77b, 77c, the adjusting valves 78a, 78b,
By operating 78c, the heat exchanger 70b is operated in the defrosting operation mode, and the heat exchangers 70a and 70c are operated in the cooling operation mode. The operating method of each valve and the operation of the heat exchanger 70 at that time are basically the same as described above.

However, the heat exchanger 70 just after defrosting operation
A and the heat exchanger 70c that continuously continues the cooling operation have different frosting conditions inside, so if the flow rate is not adjusted, more air flows into the heat exchanger 70a with a smaller pressure loss. To avoid this, adjust valves 76a and 7
It is effective to adjust the opening of 6c to equalize the flow rates. Frost formation of the heat exchanger 70a progresses over time, and the difference in pressure loss between the heat exchangers 70a and 70c becomes smaller. When the frost formation on the heat exchanger 70c further increased, the adjusting valves 76a, 76b, 76c, and the stop valve 77 were again provided.
a, 77b, 77c and adjusting valves 78a, 78b, 78c to operate the heat exchanger 70c in the defrosting operation mode, the heat exchanger 7
0a and 70b are operated in the cooling operation mode.

Thereafter, exactly the same cycle is repeated. The air cooled to a predetermined temperature by the heat exchangers in these cooling operation modes is further cooled to a lower temperature by the heat exchanger 71 on the downstream side. The method of controlling the air to be cooled to a predetermined temperature by the heat exchanger 70 is the same as that of the embodiment described with reference to FIG. Furthermore, the heat exchanger 71
After the operation of supplying the air cooled to a low temperature of about -130 ° C. to the compressor 51 and compressing it, the operation is exactly the same as that of the embodiment of FIG.

The effect obtained when the number of heat exchangers 70 is three is that the number of heat exchangers in the cooling operation mode can be set to be larger than that in the dehumidification operation mode. . In that case, the maximum cooling capacity is increased with respect to the amount of heat exchangers of the entire facility, and the facility cost can be reduced.

In this embodiment, the heat exchanger 70 has three systems, but similarly, by adding a system, it is possible to operate even if four or more heat exchangers 70 are installed. If the ratio of the systems that perform the cooling operation at the same time out of the total number of systems of the heat exchanger 70 increases, the amount of equipment per cooling capacity can be reduced.
It may be possible to reduce equipment costs. At that time, since the piping configuration and control are complicated, it is necessary to design the optimal configuration in consideration of the total cost.

The embodiments of the LNG cold heat utilization type gas turbine power generation system including the air cooling system, the heat exchanger, and the air cooling system according to the present invention have been illustrated by the two examples. However, in addition to these, the present invention can be applied to a system that uses the cold heat of LNG, such as a liquid air manufacturing system that uses the LNG cold heat.

[0076]

The air cooling system of the present invention can simultaneously cool air and defrost while suppressing an increase in pressure loss of the entire system and an increase in the amount of necessary equipment. Therefore, it is possible to provide an economical air cooling system without significantly increasing the amount of equipment and the required energy.

In addition, the heat exchanger of the present invention can discharge dew condensation water and defrost water inside the heat exchanger, so that the influence of frost formation can be suppressed, and air cooling and defrosting can be economically performed. Can be carried out. As a result, it is possible to provide an air cooling system with improved economy.

By applying the air cooling system of the present invention to a gas turbine power generation system utilizing LNG cold heat,
It is possible to provide a gas turbine power generation system that is highly efficient and economical.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a defrosting mode and a cooling mode of an air cooling system according to the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a gas turbine power generation system according to the present invention.

FIG. 3 is a longitudinal sectional view showing an embodiment of the heat exchanger according to the present invention.

4 is a cross-sectional view of the heat exchanger of FIG.

FIG. 5 is a vertical sectional view of a heat exchanger according to another embodiment of the present invention.

FIG. 6 is a graph showing the measurement results of pressure loss during frost formation on the heat exchanger.

FIG. 7 is a graph showing the relationship between the cooling temperature of air and the increase rate of pressure loss.

FIG. 8 is an explanatory diagram showing boundary conditions of temperature and pressure loss for cooling air with a heat exchanger.

FIG. 9 is a graph showing a total value of pressure loss of the high temperature heat exchanger and the low temperature heat exchanger.

FIG. 10 is a graph showing the relationship between the pressure loss of the heat exchanger and the air compression power reduction effect.

FIG. 11 is a configuration diagram showing an air cooling system according to another embodiment of the present invention.

[Explanation of symbols]

5 ... Combustor, 7 ... Gas turbine, 8 ... Generator, 9 ... Regenerative heat exchanger, 11, 12 ... Nozzle, 13 ... Stand, 16 ... Drainage pipe, 17 ... Water flow passage, 22 ... Fin, 24 ... Heat transfer pipe ,
27 ... Tube plate, 30 ... Trunk, 31 ... Baffle plate, 32 ... Lid, 40, 41 ... Piping, 42 ... Air introduction piping, 43 ... L
NG storage tank, 46 ... Condensed water tank, 47 ... Condensed water piping, 50 ... Fuel, 51 ... Air compressor, 55 ... Stack,
70, 71 ... Heat exchanger, 72 ... Four-way valve, 73 ... Header,
74 ... Regenerator, 76 ... Regulator valve, 77 ... Stop valve, 78 ... Regulator valve, 79 ... Check valve, 80 ... Air blower, 81 ... Moisture separator, 83 ... Control circuit, 84 ... Temperature sensor, 85 ... Adjust Valve, 86 ... Differential pressure gauge, 90 ... Bypass valve.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koichi Chino             2-12-1 Omika-cho, Hitachi-shi, Ibaraki Prefecture             Ceremony Company Hitachi, Ltd. F-term (reference) 3L044 AA04 BA09 CA02 DB03 KA01                       KA04 KA05                 3L103 AA32 BB05 CC18 CC24 DD08                       DD19 DD33 DD42 DD44 DD63

Claims (9)

[Claims] 1. An air cooling system for cooling air with a low temperature fluid, wherein a heat exchanger system for cooling air comprises a high temperature heat exchanger system and a low temperature heat exchanger system, and the high temperature heat exchanger system is a cooling system. Pipes are arranged to exchange heat between the target air and the low temperature fluid supplied from the low temperature heat exchanger system, the low temperature heat exchanger system being air cooled by the high temperature heat exchanger system and the low temperature fluid being a cold heat source. And the high temperature heat exchanger system is composed of a plurality of heat exchangers configured to be switchable for defrosting operation and cooling operation, and for defrosting operation and cooling. An air cooling system characterized in that the air passages of the heat exchanger for operation are connected in series, and the passages of the cryogenic fluid are connected in parallel. 2. An air cooling system for cooling air with a low temperature fluid, wherein a heat exchanger system for cooling air comprises a high temperature heat exchanger system and a low temperature heat exchanger system, and the high temperature heat exchanger system is a cooling system. Pipes are arranged to exchange heat between the target air and the low temperature fluid supplied from the low temperature heat exchanger system, the low temperature heat exchanger system being air cooled by the high temperature heat exchanger system and the low temperature fluid being a cold heat source. And the high temperature heat exchanger system is composed of a plurality of heat exchangers in which the flow paths of the low temperature fluid are connected in parallel, and the plurality of heat exchangers have a valve mechanism. Can be selectively divided into a first heat exchanger group and a second heat exchanger group, and the air passages of the first heat exchanger group and the second heat exchanger group are in series. An air cooling system characterized by being connected to. 3. The structure according to claim 1, wherein the temperature of the air supplied from the high temperature heat exchanger system to the low temperature heat exchanger system is in the range of −45 to −70 ° C. Characteristic air cooling system. 4. The air cooling system according to claim 1, further comprising a control circuit for controlling the temperature of the air to a predetermined value. 5. The water separation mechanism according to claim 1, wherein a water separation mechanism is installed at an air flow path connecting portion of the heat exchanger group connected in series in the high temperature heat exchanger system. Air cooling system. 6. A heat exchanger of an air cooling system for cooling air with a low temperature fluid, comprising a heat transfer tube group constituted by a plurality of heat transfer tubes circulating the low temperature fluid, and air installed on an outer surface of the heat transfer tube. Heat transfer fins for exchanging heat with each other, a body for accommodating the heat transfer tube group, tube plates respectively installed at both ends of the heat transfer tube group for holding the ends, and heat exchange with the space inside the body A heat exchanger comprising: a baffle plate installed so as to form a flow path of water generated in the container. 7. The heat exchanger according to claim 6, wherein the heat exchanger is arranged laterally so that the direction of air flow during defrosting is slightly downward. 8. The heat exchanger according to claim 6, wherein the heat exchanger is arranged vertically so that the air flow during defrosting is downward. 9. A gas turbine power generation system comprising an air compressor for compressing air, a combustor for combusting compressed air and fuel, and a gas turbine with combustion gas generated in the combustor. A gas turbine power generation system, wherein the air cooling system according to any one of claims 1 to 6 is used as a heat exchanger for cooling the generated air.