JPH0882413A - Condensation apparatus - Google Patents

Abstract

PURPOSE: To improve the recovery rate of latent heat by reheating gas to be processed after cooled by recovering condensable gas latent heat with the gas to be processed before the cooling. CONSTITUTION: Exhaust gas 2 discharged from an air preheating chamber 4 presents sensible heat to exhaust gas discharged from a condensation heat exchanger 16 in a gas-gas heat exchanger 15 and is hence lowered in its temperature. The exhaust gas lowered in its temperature is cooled with a heat medium 12 in the condensation heat exchanger 16 to provide water vapor latent heat and exhaust sensible heat to the heat medium 12, and is discharged from the condensation heat exchanger 16. The heat medium 12 raised in its temperature by recovering the water vapor latent heat and exhaust gas sensible heat through the condensation heat exchanger 16 supplies heat to a heat pump 13 and is lowered in its temperature and is again return to the condensation heat exchanger 16. The exhaust gas 12 discharged from the condensation heat exchanger 16 is heated in the gas-gas heat exchanger 15 with exhaust gas flowing in anew, and is again raised in its temperature and is discharged from a condensation apparatus. Accordingly, temperature of the exhaust gas in the condensation apparatus 5 is only slightly lowered. Hereby, a recovery rate of the latent heat is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent heat recovery condenser for recovering the latent heat of steam from exhaust gas containing steam in a thermal power generation boiler or the like, or a closed cycle MH.
The present invention relates to a condensing device for recovering a condensable component contained in a non-condensable gas such as a seed recovery of a D power generation system.

[0002]

2. Description of the Related Art Conventionally, in a steam turbine power plant or the like, a sensible heat recovery device such as a economizer or an air preheater is installed to recover the sensible heat of a boiler exhaust gas in order to improve thermal efficiency. When the fuel is a high water content fuel such as liquefied natural gas (LNG), since a large amount of water vapor is contained in the exhaust gas, it has been proposed to recover the latent heat of the water vapor to further improve the efficiency. Since LNG is a clean energy source whose main component is a hydrocarbon that does not contain a corrosive component such as sulfur, corrosive substances such as sulfuric acid are not generated even if latent heat is recovered, and there is no risk of low temperature corrosion. For this reason,
In LNG fueled thermal power generation boilers and the like, a condenser is actively used.

As shown in FIG. 2, a steam turbine power plant has a steam system and an exhaust gas system. In the steam system, LNG is combusted in the boiler 1, the generated steam is sent to the steam turbine 8 to rotate the generator 11, and then condensed in the condenser 9. The condensed water is pressurized by the pump 10,
After being preheated by the economizer 3, it returns to the boiler 1. The alternate long and short dash line in the figure indicates the vapor cycle. Also, the solid line in the figure,
The broken line and the dotted line represent the exhaust gas 2 and the working heat medium 12, respectively.
The flow of (hereinafter abbreviated as heat medium) and the combustion air 14 is shown.

On the other hand, in the exhaust gas system, the exhaust gas 2 emitted from the boiler 1 passes through the economizer 3, the air preheater 4 and the condensing device 5 for recovering the latent heat, and is blown from the chimney 7 to the atmosphere. Is released. Each temperature entered in the drawing is the temperature of the exhaust gas 2 and the heat medium 12 at the inlet and outlet of the condenser 5.

The condenser 5 is a condensing heat exchanger in which the exhaust gas 2 and the heat medium 12 exchange heat in a countercurrent manner. The temperature of the inflowing exhaust gas 2 is 110 ° C. and the water vapor concentration is about 17 mol.
% (Dew point temperature about 55 ° C.). On the other hand, the inlet temperature of the heat medium 12 is 35 ° C. Since the exhaust gas 2 is cooled to below the dew point temperature by the heat medium 12, the contained water vapor is condensed. At this time, not only the latent heat of steam but also the sensible heat of the exhaust gas are taken away, so that the exhaust gas temperature greatly decreases and the outlet temperature becomes 50 ° C. (that is, the temperature decrease in the condenser is 60 ° C.). On the other hand, the heat medium 12 recovers the latent heat of steam and the sensible heat of the exhaust gas and rises in temperature to 50 ° C., but supplies heat to the attached heat pump 13 to lower the temperature and returns to the condenser 5 again. The water condensed by the condenser 5 is used as boiler feed water.

Usually, the density of the exhaust gas sent to the chimney is lower than the density of the atmosphere, and the buoyancy due to this density difference causes the exhaust gas to rise in the chimney and diffuse into the atmosphere. In order to obtain sufficient buoyancy, it is necessary to keep the exhaust gas flowing into the chimney at a predetermined temperature (about 100 ° C.) or higher.

[0007]

However, when the exhaust gas 2 recovers latent heat in the condenser 5, the sensible heat is also taken away at the same time, so that the exhaust gas temperature is lower than the predetermined temperature required to obtain sufficient buoyancy. Considerably lower. As a result, not only the rising speed of the exhaust gas decreases, but also the diffusion speed into the atmosphere decreases, which may lead to pollution problems. In order to prevent this, measures such as providing the ventilator 6 and raising the chimney 7 are required, but there is a problem that the facility cost increases and the power generation efficiency decreases due to the power consumption of the ventilator 6. .

Further, since the temperature of exhaust gas at the outlet of the condenser 5 cannot be lowered so much (about 50 ° C. at most),
The latent heat cannot be recovered sufficiently, and a considerable amount of latent heat of steam is discarded.

On the other hand, in a condensing device for condensing and recovering a small amount of condensable gas components contained in the gas to be treated, such as a seed recovery condensing device of a closed cycle MHD power generation system, the recovery rate of the condensable gas components is improved. In order to achieve this, it is necessary to cool the gas to be processed to a temperature as low as possible. However, this causes a large decrease in the temperature of the gas to be treated, resulting in a large energy loss. On the contrary, if the cooling temperature of the gas to be treated is increased in order to suppress energy loss, the recovery rate of the condensable gas component decreases.

The present invention has been made in order to solve such a conventional problem, and can recover the condensable gas component and the latent heat of the condensable gas without substantially lowering the temperature of the gas to be treated. An object of the present invention is to provide a condensing device that can be used.

[0011]

In order to achieve the above object, a condensing apparatus according to the present invention cools a gas to be treated containing a condensable gas and a non-condensable gas and removes the condensable gas in the gas to be treated. In a condenser capable of condensing and recovering the latent heat of the condensable gas component or the condensable gas, the gas to be treated after recovering the latent heat of the condensable gas component or the condensable gas,
It is characterized in that the condensable gas component or the latent heat of the condensable gas is reheated by the gas to be treated before being recovered.

Further, the condensing device according to the present invention includes a first heat exchanger for exchanging heat between the gas to be treated and the gas to be treated before and after recovering the condensable gas component or the latent heat of the condensable gas, and the gas to be treated. A second heat exchanger for recovering the latent heat of the condensable gas component or the condensable gas therein. In this case, the gas to be treated is a combustion exhaust gas of liquefied natural gas containing water vapor as a condensable gas.

[0013]

In the condensing device according to the present invention, the condensable gas and the gas to be treated whose temperature is lowered by recovering the latent heat thereof are
Since the latent heat of the condensable gas is reheated with the gas to be treated before it is recovered (that is, before being cooled), the temperature of the gas to be treated is hardly lowered, that is, the sensible heat amount of the gas to be lost is small, The condensable gas component and its latent heat are recovered.

Therefore, in the condenser for recovering latent heat of steam in exhaust gas, sufficient buoyancy is obtained to release the exhaust gas into the atmosphere, and equipment such as a ventilator and its power consumption can be omitted. Furthermore, since the exhaust gas can be cooled at a sufficiently low temperature without worrying about the decrease in the exhaust gas temperature, it is possible to recover the latent heat almost completely.

Further, in the condensing device for recovering the condensable component in the gas to be treated, the temperature decrease of the non-condensable gas can be suppressed to the minimum, so that the energy loss can be reduced. Further, since the non-condensable gas can be cooled at a sufficiently low temperature and the condensable component can be recovered without being concerned about the temperature decrease of the non-condensable gas, the recovery rate can be greatly improved.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In this embodiment, a case where the condenser of the present invention is used as a latent heat recovery device for recovering steam latent heat from boiler exhaust gas in a steam turbine power plant will be described. The condenser 5 is shown by being surrounded by a chain double-dashed line in FIG.

The condensing device 5 comprises a counterflow type gas-gas heat exchanger 15 as a first heat exchanger and a counterflow type condensing heat exchanger 16 as a second heat exchanger. ing.
A solid line, a broken line, and a dotted line in the figure show the flows of the exhaust gas 2, the heat medium 12, and the combustion air 14, respectively. The steam cycle is omitted from FIG. 1 as it is not particularly relevant to the present invention. The temperatures entered in the figure are examples of the exhaust gas temperature and the heat medium temperature in the condenser and at the inlet and outlet of the condenser. Here, the minimum temperature difference between the heating fluid and the heated fluid in the gas / gas heat exchanger 15 and the condensation heat exchanger 16 is set to 20 ° C. and 15 ° C., respectively. Exhaust gas 2 (temperature is 110 ° C., water vapor concentration is about 17 mol%, dew point temperature is about 55 ° C.) that exits air preheater 4, is
The gas heat exchanger 15 gives sensible heat to the exhaust gas leaving the condensing heat exchanger 16 to lower the temperature to 70 ° C. The exhaust gas whose temperature has been lowered is cooled by the heat medium 12 in the condensing heat exchanger 16, and gives latent heat of steam and sensible heat of the exhaust gas to the heat medium 12, and exits the condensing heat exchanger 16 at 50 ° C. The heat medium 12 whose temperature has risen by collecting latent heat of steam and sensible heat of exhaust gas in the heat exchanger 16 for condensation supplies heat to the heat pump 13,
The temperature is lowered, and the flow returns to the condensation heat exchanger 16 again.

The exhaust gas 2 (temperature 50 ° C.) exiting the heat exchanger 16 for condensation is the exhaust gas (temperature 110 ° C.) at the inlet of the condenser 5.
Although the temperature is much lower than that of, the newly introduced exhaust gas (temperature 110 ° C) in the gas / gas heat exchanger 15
The temperature rises again and flows out from the condenser 5 (outlet temperature 90 ° C.). As a result, the temperature drop of the exhaust gas in the condenser 5 was only 20 ° C., and the latent heat of steam contained was recovered with almost no decrease in the temperature of the non-condensable gas. If the performance of the gas-gas heat exchanger is improved and the temperature difference between the heated fluid and the heated fluid is further reduced, the temperature drop of the exhaust gas in the condenser 5 can be further reduced. Further, if the temperature of the heat medium 12 returning from the heat pump 13 is further lowered, the exhaust gas can be cooled at a lower temperature, so that the latent heat recovery rate can be further improved.

In the above embodiment, the case where the condenser of the present invention is used to recover latent heat of steam in boiler exhaust gas has been described. However, such a condenser is used in a closed cycle MH.
Seed (alkali metal such as potassium) contained in a small amount in the working fluid (helium gas, etc.) in the D power generation system
It can also be used as a device for recovering.

In the closed cycle MHD power generation system, when a small amount of seed contained in the working fluid is condensed and collected, it is necessary to cool the working fluid to a temperature as low as possible in order to improve the seed recovery rate. However, when the working fluid is cooled and the seeds are collected, the sensible heat of the working fluid is also removed at the same time, so that the temperature of the working fluid is significantly lowered, resulting in a great energy loss. On the other hand, if the cooling temperature is increased in order to suppress energy loss, the seed recovery rate will decrease.

Therefore, in the seed recovery condenser of the closed cycle MHD power generation system, the working fluid after seed recovery is reheated by the working fluid before seed recovery by the first heat exchanger (gas / gas heat exchanger). Then, the second heat exchanger (condensation heat exchanger) condenses and recovers a small amount of seed contained in the working fluid such as helium gas. This increases the seed recovery rate and reduces the temperature drop of the working fluid.

[0022]

As described above, according to the condenser of the present invention, the gas to be treated after being cooled in order to recover the condensable gas component and its latent heat is reheated by the gas to be treated before being cooled. Therefore, the condensable gas component and its latent heat can be efficiently recovered with almost no decrease in the temperature of the gas to be treated.

As a result, in the condenser for recovering the latent heat of steam of the exhaust gas, sufficient buoyancy is obtained to discharge the exhaust gas into the atmosphere, so that auxiliary equipment such as a ventilator becomes unnecessary, and further, Power consumption can be reduced.

Furthermore, since the temperature of the exhaust gas to be finally discarded does not drop significantly and the exhaust gas can be cooled to a sufficiently low temperature in the condenser, the recovery rate can be greatly improved, and the exhaust gas can be almost completely removed. The latent heat can be recovered.

Further, in the condensing device for recovering the condensable component in the gas to be treated, the temperature drop of the gas to be treated can be suppressed to a minimum, so that the energy loss can be reduced.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example in which a condenser according to the present invention is applied to recover latent heat of steam contained in boiler exhaust gas.

FIG. 2 is a flow sheet showing a conventional condenser for recovering latent heat of steam.

[Explanation of symbols]

 2 ... Exhaust gas 5 ... Condensing device 12 ... Heat medium 15 ... Gas / gas heat exchanger (first heat exchanger) 16 ... Condensing heat exchanger (second heat exchanger)

Claims (3)

[Claims] 1. A process gas containing a condensable gas and a non-condensable gas can be cooled and the condensable gas in the process gas can be condensed to recover the condensable gas component or the latent heat of the condensable gas. In this condensing device, the gas to be treated after recovering the latent heat of the condensable gas component or the condensable gas is reheated by the gas to be treated before recovering the latent heat of the condensable gas component or the condensable gas. And a condenser. 2. A process gas containing a condensable gas and a non-condensable gas can be cooled and the condensable gas in the process gas can be condensed to recover the condensable gas component or the latent heat of the condensable gas. First heat exchanger for performing heat exchange between the process gas before and after recovering the condensable gas component or the latent heat of the condensable gas, and the condensable gas component or condensation in the process gas A second heat exchanger that recovers latent heat of the volatile gas, and a condensing device. 3. The condenser according to claim 1, wherein the gas to be treated is a combustion exhaust gas of liquefied natural gas containing water vapor as a condensable gas.