JP2015230117A - Air-cooled steam condensing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-cooled steam condensing device that has higher heat exchange performance than conventional ones, enables a compact design, and is hard to generate dew condensation.SOLUTION: In an air-cooled steam condensing device 11, cooling air F is sprayed toward a condensing pipe unit 21 comprising a plurality of condensing pipes 23 where exhaust steam discharged from equipment flows, then the cooling air cools the condensing pipes 23, and thereby the exhaust steam in the condensing pipes 23 are condensed. The plural stages of the condensing pipe units 21 are arranged with intervals in a cooling air flow direction. Between condensing pipe units 21 adjacent in the cooling air flow direction, provided is a water spray nozzle 24 for spraying water to the cooling air F.

Description

  According to the present invention, the condensate pipe is air-cooled by blowing cooling air toward a condensate pipe unit in which a plurality of condensate pipes through which exhaust steam discharged from equipment such as a steam turbine generator flows is bundled. The present invention relates to an air-cooled steam condensing device that condenses exhaust steam in a water pipe.

  In a waste incinerator equipped with a power generation facility, steam is generated in a boiler using the heat of exhaust gas discharged from the waste incinerator, and power is generated by supplying the generated steam to a steam turbine generator. The exhaust steam discharged from the steam turbine generator is condensed by a steam condensing device and stored in a condensate tank. The condensate stored in the condensate tank is sent to a deaerator to remove gases such as dissolved oxygen and then supplied to the boiler again.

  In the air-cooled steam condensing device that condenses the exhaust steam in the condensate pipe by air cooling the condensate pipe by blowing cooling air to the condensate pipe through which the exhaust steam flows, the cooling air is used to improve the heat exchange performance. It is desirable to increase the temperature difference from the condensate temperature by lowering the temperature of the water. For example, Patent Document 1 discloses an air-cooled steam condensing device that includes a steam condenser that forcibly cools a condenser pipe from the outside and an air passage that supplies air to the steam condenser, and is provided with a water spray nozzle in the air passage. Is disclosed. Water is sprayed on the air introduced into the air passage to form cooling air, and the condenser tube is forcedly air-cooled from the outside with the cooling air. In this air-cooled steam condensing device, the heat exchange performance is improved by lowering the temperature of the air introduced into the air passage by using the latent heat of vaporization of water and increasing the temperature difference from the condensate temperature. Yes.

  Further, in Patent Document 2, in an air-cooled steam condensing apparatus that cools air by blowing the outside air introduced from the outside air introduction section into the steam condenser chamber onto the steam condenser by a blower, a plurality of passages are passed through the outside air introduction section. By arranging air rectifying members with uniformly arranged pores, providing water spray nozzles with shutoff valves in each vent hole, and operating the shutoff valves to increase or decrease the number of water spray nozzles used for water spraying. An invention for adjusting the temperature and humidity of the cooling air blown to the condenser is disclosed. In this air-cooled steam condensing device, in order to further improve the function of the air-cooled steam condensing device described in Patent Document 1, the amount of water spray is controlled according to fluctuations in the amount of exhaust steam and outside air conditions.

Japanese Patent Laid-Open No. 11-142067 JP 2010-169285 A

  Generally, the overall dimensions of the air-cooled steam condensing device, the capacity of the blower, and the like are determined by the outside air temperature assumed at the time of design. Therefore, in order to obtain stable cooling performance throughout the year, it is necessary to design an air-cooled steam condensing device assuming summertime when the outside air temperature is high. As a result, it is necessary to increase the heat transfer area of the condensate pipe, which inevitably increases the installation space for the air-cooled steam condensing device.

  As a countermeasure against the above problem, as seen in the patent literature, it is effective to lower the temperature of the cooling air using the latent heat of vaporization of water. However, in the case of the conventional water spray type air-cooled steam condensing device, the temperature of the cooling air sprayed on the condensate pipe cannot be lowered in principle to the wet bulb temperature or lower. Furthermore, if the temperature of the cooling air is lowered to a temperature close to the saturation state of water (that is, the wet bulb temperature), incomplete evaporation tends to occur and the amount of non-evaporated water increases. As a result, there is a problem that not only the spray water consumption is increased, but also the non-evaporated water wets the peripheral equipment and the peripheral equipment is corroded.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an air-cooled steam condensing device that has a higher heat exchange performance than that of the prior art, can be compactly designed, and can suppress unevaporated water. .

In order to achieve the above-mentioned object, the present invention blows cooling air toward a condensate pipe unit in which a plurality of condensate pipes through which exhaust steam discharged from facility equipment flows flows, thereby cooling the condensate pipes by air. In an air-cooled steam condensing device that condenses exhaust steam in the condensate pipe,
A water spray nozzle that sprays water onto the cooling air between the condensate pipe units that are arranged in a plurality of stages at intervals in the flow direction of the cooling air and that is adjacent to the flow direction of the cooling air. It is characterized by being provided.

The cooling air that has passed through the upstream condensate pipe unit exchanges heat with the condensate pipe constituting the condensate pipe unit, so that the temperature is higher than that of the cooling air before being introduced into the condensate pipe unit. It is high. In the present invention, the cooling air whose temperature has been lowered by spraying water onto the cooling air that has passed through the upstream condensate pipe unit and has increased in temperature is introduced into the downstream condensate pipe unit. Compared to the conventional case, the logarithmic average temperature difference between the cooling air and the condensate temperature is increased, and the heat exchange performance is improved.
In addition, the cooling air that has passed through the upstream condensate pipe unit and has a higher temperature has a lower relative humidity with respect to the outside air at the inlet of the steam condensing device, and the amount of spray water that reaches saturated steam greatly increases. Thereby, the cooling performance by evaporation is improved, and complete evaporation is easily performed. Furthermore, since the cooling air that has passed through the upstream condensing pipe unit is rectified so as to flow uniformly in the air flow path, uniform cooling can be obtained by evenly arranging the water spray nozzles.

  In the air-cooled steam condensing device according to the present invention, water is sprayed on the cooling air that has passed through the upstream condensate pipe unit and has a high temperature. The temperature can be greatly reduced. Since the cooling air whose temperature has decreased is introduced into the condensate pipe unit on the downstream side, a larger temperature difference can be obtained between the cooling air and the condensate temperature than in the past. As a result, the heat exchange performance is improved, the heat transfer area is reduced, the installation area of the steam condensing device can be greatly reduced, and the load on the frame supporting the steam condensing device is reduced. be able to. Furthermore, adverse effects such as condensation due to incomplete evaporation can be prevented.

1 is a schematic diagram of an air-cooled steam condensing device according to a first embodiment of the present invention. It is a perspective view of the air-cooled steam condensing device. It is an axial orthogonal direction sectional view of a condensate pipe unit. It is an axial sectional view of a condensate pipe. It is a schematic diagram of the air-cooled steam condensing apparatus which concerns on the 2nd Embodiment of this invention. It is a humid air line figure which shows the cooling state of the conventional air cooling type steam condensing apparatus. It is a humid air line figure which shows the cooling state of the air-cooling type steam condensing apparatus which concerns on embodiment of this invention.

  Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.

[Air-cooled steam condensing device according to the first embodiment]
The air-cooled steam condensing device 11 according to the first embodiment of the present invention is fed by a steam distribution pipe 14 that supplies exhaust steam discharged from equipment such as a steam turbine generator, and a steam distribution pipe 14. Water is supplied to the condensate pipe unit 21 that condenses the supplied exhaust steam, the condensate collecting pipe 15 that collects the condensate discharged from the condensate pipe unit 21, and the cooling air F that passes through the condensate pipe unit 21. And a water spray nozzle 24 for spraying (see FIGS. 1 and 2). A blower 25 that supplies cooling air F to the condensate pipe unit 21 is installed below the condensate pipe unit 21.

  The condensate pipe unit 21 is a rectangular panel formed by bundling a plurality of condensate pipes 23 through which exhaust steam flows (see FIG. 3). In the present embodiment, the condensate pipes 23 are arranged in two stages in the direction in which the cooling air F passes. The cooling air F passes through a clearance provided between adjacent condensate pipes 23.

  Each condensate pipe 23 is also called a fin tube, and is composed of a cylindrical tube 23a through which exhaust steam flows and a ring-shaped fin 23b formed on the outer periphery of the tube 23a (see FIG. 4). The tubes 23a are made of carbon steel, and the fins 23b are made of aluminum.

The steam distribution pipe 14 includes a main pipe 14 a disposed in the horizontal direction and a branch pipe 14 b that branches from the main pipe 14 a and supplies exhaust steam to each condensate pipe unit 21.
The condensate pipe unit 21 is arranged so that the exhaust steam flows symmetrically with respect to a virtual vertical plane including the main pipe 14a and obliquely downward from the main pipe 14a. Further, the flow direction of the cooling air F (in this embodiment, the vertical direction) ) Are arranged in two steps with a gap. That is, the condensate pipe unit 21 is arranged in a state where the gable roofs are stacked in two stages. A condensate collecting pipe 15 that collects condensate discharged from the condensate pipe unit 21 is disposed along the downstream end of each condensate pipe unit 21.
Further, the blower 25 that supplies the cooling air F to the condensate pipe unit 21 is installed below the condensate pipe unit 21 arranged on the upstream side (lower stage side in the present embodiment).

  The water spray nozzle 24 is installed between the condensing pipe units 21 adjacent to each other in the flow direction of the cooling air F (vertical direction in the present embodiment) and close to the condensing pipe unit 21 arranged on the lower side. Yes. An injection hole (not shown) of the water spray nozzle 24 is directed upward from the horizontal plane. That is, water is sprayed from the upstream condensate pipe unit 21 toward the downstream (upper stage in the present embodiment) condensate pipe unit 21.

The interval between the condensing pipe units 21 adjacent to each other in the vertical direction may be an interval sufficient for the water sprayed from the water spray nozzle 24 to evaporate, and may be approximately 2 m or more. The inclination angle of the condensate pipe unit 21 is not particularly limited, and may be substantially horizontal.
A shielding wall (not shown) is provided on the side of the air-cooled steam condensing device 11 so that the cooling air F does not escape.

The operation of the air-cooled steam condensing device 11 according to the present embodiment is as follows.
When the blower 25 installed below the condensate pipe unit 21 is driven, the cooling air F is blown to the condensate pipe unit 21. As the cooling air F passes through the condensate pipe unit 21 arranged on the lower side, heat exchange is performed between the condensate pipe 23 and the cooling air F constituting the condensate pipe unit 21 arranged on the lower side. Is called. As a result, the exhaust steam fed from the steam distribution pipe 14 to the condensate pipe 23 condenses in the condensate pipe 23 to become condensate, and is stored in a condensate tank (not shown) via the condensate collecting pipe 15. .

On the other hand, water is sprayed from the water spray nozzle 24 to the cooling air F that has passed through the condensate pipe unit 21 disposed on the lower side. The cooling air F whose temperature has been lowered by the water spray passes through the condensate pipe unit 21 disposed on the upper stage side, and exchanges heat with the condensate pipe 23 constituting the condensate pipe unit 21 disposed on the upper stage side. Thus, the exhaust steam fed from the steam distribution pipe 14 to the condensate pipe 23 condenses in the condensate pipe 23 to become condensate, and is stored in the condensate tank via the condensate collecting pipe 15.
The cooling air F that has passed through the condensate pipe unit 21 disposed on the upper side is released into the atmosphere.

  Next, regarding the heat exchange performance of the air-cooled steam condensing device according to the present embodiment, a conventional air-cooled steam condensing device (condensate pipe unit) in which a water spraying device is installed at the cooling air introduction portion at the inlet of the steam condensing device. Is considered as a comparison target.

When the heat exchange amount Qs of the conventional air-cooled steam condensing device is expressed by a heat balance equation, the following equation is obtained.
Qs = (h2-h1) · G0
here,
h1: Specific enthalpy of cooling air immediately before passing through the condensate pipe unit h2: Specific enthalpy of cooling air immediately after passing through the condensate pipe unit G0: Amount of cooling air

Further, the heat exchange amount Qs of the conventional air-cooled steam condensing device is represented by the following equation when expressed by a heat transfer calculation formula.
Qs = K · Δtm · A0
here,
K: Heat transfer coefficient Δtm: Logarithmic average temperature difference A0: Total heat transfer area of the condenser unit

The logarithmic average temperature difference Δtm is expressed by the following equation.
Δtm = {(tw−ta1) − (tw−ta2)}
/ Ln {(tw-ta1) / (tw-ta2)}
here,
tw: temperature of exhaust steam ta1: temperature of cooling air immediately before passing through the condensate pipe unit ta2: temperature of cooling air immediately after passing through the condensate pipe unit

  As a general actual operating condition, the temperature of the exhaust steam is 65 ° C., the atmospheric condition is an air temperature of 30 ° C. and the relative humidity is 50%. The exchange amount is a basic condition. In addition, the water spray is considered to have a relative humidity of about 80 to 90% after spraying in consideration of complete evaporation. Therefore, in this embodiment, the upper limit is set to 80%.

FIG. 6 shows a state of the cooling air passing through the steam condensing device on the wet air diagram under the above conditions. When water spraying is performed in the range from the initial state (relative humidity 50%) of the atmosphere in the state (1) to the relative humidity 80% in the state (2) on the inlet side, the temperature ta1 of the cooling air immediately before passing through the condenser unit Is 24.5 ° C. and the specific enthalpy h1 is 64.2 kJ / kg (DA). Heat exchange for 20 ° C. is performed from here through the condensate pipe unit, the temperature ta2 of the cooling air immediately after passing through the condensate pipe unit in the outlet side state (3) is 44.5 ° C., and the specific enthalpy h2 is 85. 0.0 kJ / kg (DA).
The above-described heat balance equation and heat transfer calculation formula under this condition are as follows.
Qs = 20.8 × G0
Qs = 29.4 × K · A0

  On the other hand, in the air-cooled steam condensing apparatus according to the embodiment of the present invention, the same performance as that of the above-described conventional type, that is, the same heat exchange amount is considered. In the present embodiment, assuming that the upper and lower condensate pipe units 21 are responsible for half the heat exchange amount, the heat exchange amounts of the upper and lower condensate pipe units are Qu = Qd = Qs / 2 = 10.4. XG0.

  FIG. 7 shows a state of the cooling air of the air-cooled steam condensing device according to the present embodiment on the wet air diagram based on the above conditions. The outside air taken into the steam condensing unit as the state (1) is directly introduced into the lower condenser unit and heat-exchanged to increase the temperature to 40 ° C. and the relative humidity to 28.7%. Become. Here, water spraying can be performed up to 80% which is the upper limit of the relative humidity. The cooling air in the state (3) whose temperature has been lowered to 27.4 ° C. by water spraying is heated up to 37.2 ° C. in the state (4) through heat exchange while passing through the upper condenser tube unit. .

The heat exchange amount Qs of the air-cooled steam condensing device according to the present embodiment is expressed by the following equation.
Qs = Qd + Qu = K · Δtmd · Ad + K · Δtmu · Au
here,
Qd = heat exchange amount of the lower condenser tube unit Qu = heat exchange amount of the upper condenser tube unit Δtmd: logarithmic mean temperature difference of the lower condenser unit Δtmu: logarithmic mean temperature difference of the upper condenser unit Ad: lower part Heat transfer area of the condenser tube unit Au: Heat transfer area of the upper condenser tube unit

Logarithmic average temperature differences Δtmd and Δtmu are expressed by the following equations.
Δtmd = {(tw−ta1d) − (tw−ta2d)}
/ Ln {(tw−ta1d) / (tw−ta2d)}
Δtmu = {(tw−ta1u) − (tw−ta2u)}
/ Ln {(tw-ta1u) / (tw-ta2u)}
here,
ta1d: Temperature of the cooling air immediately before passing through the lower side condenser tube unit = 30 ° C.
ta2d: temperature of the cooling air immediately after passing through the lower condenser tube unit (before water spraying) = 40 ° C.
ta1u: Temperature of cooling air immediately after passing through the upper condenser tube unit (after water spraying) = 27.4 ° C.
ta2u: Temperature of the cooling air immediately after passing through the upper condenser tube unit = 37.2 ° C
Therefore,
Qs = K × 29.7 × Ad + K × 32.5 × Au = 62.2 × K · (Ad + Au)

When comparing the conventional air-cooled steam condensing device and the air-cooled steam condensing device according to the present embodiment with respect to the heat transfer area,
(Ad + Au) /A0=29.4/62.2=0.47
It becomes. Therefore, the air-cooled steam condensing device according to the present embodiment can exhibit the same heat exchange performance with a heat transfer area of 47% of the conventional air-cooled steam condensing device.

  In addition, compared with an air-cooled steam condensing device (the total heat transfer area of the condensing pipe unit is A00) that does not have the most widely used water spraying device at present, the cooling air is recovered. Since the temperature is raised from 30 ° C. to 50 ° C. through the water pipe unit, the heat exchange amount is Qs = 23.6 × K · A00 in the heat transfer calculation formula. In comparison of the heat transfer area with this embodiment, (Ad + Au) /A00=23.6/62.2=0.38, and the same performance can be achieved with a heat transfer area of 38%.

  As shown in the above results, by performing water spraying on the cooling air that has been heated by heat exchange in the condensate pipe and the relative humidity has been reduced, the range of reduction in the temperature of the cooling air by water spraying can be reduced. It can be secured larger than As a result, the logarithmic average temperature difference increases, and the heat transfer area of the steam condensing device can be reduced.

[Air-cooled steam condensing device according to the second embodiment]
In the air-cooled steam condensing device 13 according to the second embodiment of the present invention, the condensate pipe unit 21 is not arranged symmetrically with respect to the virtual vertical plane including the main pipe 14a, but one side of the virtual vertical plane. Only the point where the condensate pipe unit 21 is arranged is different from the air-cooled steam condensing device 11 according to the first embodiment (see FIG. 5).

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the above-described embodiments, and is considered within the scope of the matters described in the claims. Other embodiments and modifications are also included. For example, in the above-described embodiment, the flow direction of the cooling air is set from the lower side to the upper side, but may be a left-right direction or an oblique direction.
Further, although the condensate pipe unit is arranged in two stages in the cooling air flow direction, three or more stages may be arranged, and the number of condensate pipes constituting the condensate pipe unit is not limited to two stages, and may be any number of stages. good. Furthermore, it is possible to further reduce the heat transfer area by installing a water spray device at the inlet of the steam condensing device.

11, 13: Air-cooled steam condensing device, 14: Steam distribution pipe, 14a: Main pipe, 14b: Branch pipe, 15: Condensate collecting pipe, 21: Condensate pipe unit, 23: Condensate pipe, 23a: Tube, 23b: Fin, 24: Water spray nozzle, 25: Blower, F: Air for cooling

Claims (1)

The exhaust steam in the condensate pipe is condensed by blowing cooling air toward the condensate pipe unit in which a plurality of condensate pipes through which exhaust steam discharged from the facility equipment is bundled is bundled. In air-cooled steam condensing equipment,
A water spray nozzle that sprays water onto the cooling air between the condensate pipe units that are arranged in a plurality of stages at intervals in the flow direction of the cooling air and that is adjacent to the flow direction of the cooling air. An air-cooled steam condensing device, which is provided.

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