KR20230093091A - Polymer Heat Exchanger For Low Temperature Exhaust Gas Heat Recovery and Combustion Air Preheating System Comprising It - Google Patents

Abstract

The present invention provides a low-temperature exhaust gas heat recovery polymer heat exchanger capable of recovering heat from low-temperature exhaust gas. and a plurality of tubes extending from the fluid inlet to the fluid outlet and having a U-shape as a whole, wherein the plurality of tubes is a polymer composite in which at least one of carbon, ceramic, and metal particles is included as a filler in a pure polymer. It provides a low-temperature exhaust gas heat recovery polymer heat exchanger comprising a.

Description

Polymer Heat Exchanger For Low Temperature Exhaust Gas Heat Recovery and Combustion Air Preheating System Comprising It}

The present invention relates to a polymer heat exchanger capable of recovering low-temperature heat.

When the exhaust gas temperature of power generation, steel, oil rectification, brick factory, bakery, beer, incineration process, etc. is below 200℃, heat recovery is not possible due to low-temperature corrosion and economic feasibility, and is released into the atmosphere. On the other hand, in the case of exhaust gas over 300℃, exhaust heat can be recovered by a metal heat exchanger to increase the efficiency of the plant by heating combustion air and preheating feed water, and by installing an exhaust heat recovery boiler, steam can be generated and used as power generation and processor steam.

In general, exhaust gas has different components depending on the type of fuel, but sulfuric acid, hydrochloric acid, and nitric acid exist in gaseous form, and when cooled below the dew point temperature in response to the exhaust gas pressure, they condense on the surface of the metal heat exchanger and cause severe corrosion, which causes system operation to stop. cases do occur.

In recent years, attention has been focused on the heat recovery of low-temperature flue gas that has been discarded so far in order to increase the efficiency of plants due to restrictions on carbon emissions and demands for the use of clean energy. When recovering low-temperature exhaust gas heat, low-temperature corrosion does not satisfy the economic feasibility of metal heat exchangers. Therefore, polymer heat exchangers made of polymers are installed in low-temperature exhaust gases to commercialize gaseous fuel preheating, combustion air preheating, and feedwater preheating technologies.

In the case of polymer heat exchangers, they are superior to metal heat exchangers in manufacturing, processability, light weight, washability, low-temperature corrosion, and rupture. There are limits to what is required.

(Patent Document 1) JP 2016-61542 A

The present invention is to solve the above problems, and an object of the present invention is to provide a low-temperature exhaust gas heat recovery polymer heat exchanger capable of recovering heat from low-temperature exhaust gas.

In order to achieve the above object, the present invention provides a low-temperature flue gas heat recovery polymer heat exchanger and a combustion air preheating system as follows.

The present invention is disposed on the path of the low-temperature exhaust gas in one embodiment, the fluid inlet and fluid outlet disposed on one side; and a plurality of tubes extending from the fluid inlet to the fluid outlet and having a U-shape as a whole, wherein the plurality of tubes is a polymer composite in which at least one of carbon, ceramic, and metal particles is included as a filler in a pure polymer. It provides a low-temperature exhaust gas heat recovery polymer heat exchanger comprising a.

In one embodiment, a water spray spray for spraying water toward the plurality of tubes may be further included, or a tube insert extending along the tube may be inserted into the inside of the tube.

In the low-temperature exhaust gas heat recovery polymer heat exchanger of one embodiment, the fluid inlet and the fluid outlet are disposed on the upper side, and the tube is connected to the fluid inlet and extends in a vertical direction, a first extension connected to the fluid outlet and vertically It may include a second extension portion extending, and a curved portion that bends and connects a lower end portion of the first extension portion and a lower end portion of the second extension portion.

The present invention is a heat source unit in which combustion occurs in one embodiment; an inlet passage for supplying air to the heat source; a discharge path through which the gas generated from the heat source unit is exhausted; a metal heat exchanger for exchanging heat between the inlet passage and the air passing through the outlet passage; and a polymer heat exchanger disposed downstream of the metal heat exchanger on the discharge passage and exchanging heat between air before flowing into the metal heat exchanger and gas on the discharge passage, wherein the polymer heat exchanger recovers heat from the low-temperature exhaust gas described above. An air preheating system for combustion that is a polymer heat exchanger is provided.

The present invention can provide a polymer heat exchanger capable of recovering low-temperature exhaust gas heat through the above configuration, and can provide a combustion air preheating system including the same.

1 is a schematic perspective view of a low-temperature exhaust gas heat recovery polymer heat exchanger according to an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view of the low-temperature exhaust gas heat recovery polymer heat exchanger of FIG. 1 .
3 and 4 are plan views of the distribution plate of FIG. 1;
5 is a schematic perspective view of a low-temperature exhaust gas heat recovery polymer heat exchanger according to another embodiment of the present invention.
6 is a schematic diagram of a combustion air preheating system including a low-temperature flue gas heat recovery polymer heat exchanger according to an embodiment of the present invention.

Hereinafter, preferred embodiments will be described in detail so that those skilled in the art can easily practice the present invention with reference to the accompanying drawings. However, in describing a preferred embodiment of the present invention in detail, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. In addition, the same reference numerals are used throughout the drawings for parts having similar functions and actions. In addition, in this specification, terms such as 'upper', 'upper', 'upper surface', 'lower', 'lower', 'lower surface', and 'side surface' are based on the drawings, and are actually elements or components may vary depending on the direction in which is placed.

In addition, throughout the specification, when a part is said to be 'connected' to another part, this is not only the case where it is 'directly connected', but also the case where it is 'indirectly connected' with another element in between. include In addition, 'including' a certain component means that other components may be further included, rather than excluding other components unless otherwise stated.

In general, polymer heat exchangers are superior to metal heat exchangers in terms of manufacturability, processability, light weight, washability, low-temperature corrosion, and rupture, but due to the material characteristics, the thermal conductivity is <0.25W/mK, which is 100 times smaller than that of metal heat exchangers. For this reason, when a polymer heat exchanger is applied to low-temperature exhaust gas, it has excellent operating properties compared to a metal heat exchanger, but a huge heat transfer area is required.

In order to overcome this, it is necessary to consider the material, shape, arrangement, and washability of the polymer heat exchanger. The flow rate of low-temperature flue gas and cooling fluid, tube arrangement and flow direction, and the material of the plastic heat exchanger are the main factors for calculating the heat transfer area. The present invention discloses a highly conductive polymer composite heat exchanger structure that maximizes heat transfer by introducing a fluid flow direction, fluid retention time, cleaning method, and a fluid disturbance device when a gas-gas type heat exchanger is applied.

1 and 2 show a perspective view and a partial cross-sectional view of a low-temperature exhaust gas heat recovery polymer heat exchanger according to an embodiment of the present invention, and FIGS. 3 and 4 show a plan view of the distribution plate of FIG. 1 .

1 and 2, the low-temperature exhaust gas heat recovery polymer heat exchanger according to the present invention is disposed on the path of the low-temperature exhaust gas, and includes a fluid inlet 110 and a fluid outlet 120 disposed on one side; and a plurality of tubes 140 extending from the fluid inlet 110 to the fluid outlet 120 and having a U-shape as a whole, and a water spray 160 spraying water toward the plurality of tubes. A distribution plate 130 connecting the fluid inlet 110 and the fluid outlet 120 and the plurality of tubes 140, and a support plate disposed in the middle of the tubes 140 and fixing the tubes 140. (150).

Since the fluid inlet 110 and the fluid outlet 120 are connected to the U-shaped tube 140, they are disposed in the same direction in the tube 140, and preferably the fluid inlet 110 and the fluid outlet 120 Is disposed on the upper side, the U-shaped tube 140 is connected to the lower portion of the fluid inlet 110 and the fluid outlet 120.

As shown in FIG. 2, the U-shaped tube 140 is a tube having a U shape as a whole by connecting a curved portion 143 between first and second extension portions 142 and 144 extending in the vertical direction ( 140). The curved portion 143 may have a curved structure that is constantly bent with a predetermined radius of curvature, but is not limited thereto.

The fluid introduced into the fluid inlet 110 is dispersed into the plurality of tubes 140 by the inner space 111 of the inlet 110 and the distribution plate 130 . The number of tubes 140 is not particularly limited, but tens to hundreds of tubes 140 may be connected to the distribution plate 130 . In addition, a support plate 150 for supporting the tube 140 is installed in the middle along with the distribution plate 130 to fix the tube 140 composed of a plurality of highly conductive polymer composites. 1 and 2 show that one support plate 150 is disposed on the inlet side and the outlet side, but a larger number of support plates ( 150) can be arranged, of course.

Meanwhile, as shown in FIG. 2 , a tube insert 145 is disposed inside the tube 140 to make the fluid flow inside the tube 140 turbulent. The tube insert 145 may be continuously arranged from the starting position to the ending position of the tube 140 . The tube insert 145 enhances mixing and turbulence strength of the fluid flowing inside the tube to help heat the internal fluid.

In addition, the tube 140 has a U-shape and is arranged so that the flow of the low-temperature exhaust gas and the heated fluid flows in a counter flow.

The water spray spray 160 includes a spray nozzle 162 for spraying water into the tube 140 and a pipe 161 connected to the nozzle 162 and a water supply source (not shown), through which exhaust gas flows. It may be disposed inclined upward toward the tube 140 at the lower side of the side. Although not shown, a plurality of water spray sprays 160 may be disposed to spray water toward the tube 140 .

In the present invention, the tube 140 is formed of a high thermal conductivity polymer composite material using carbon, ceramic, metal particles, etc. having good thermal conductivity as a filler in a pure polymer in order to overcome thermal conductivity. As a result, the wall 141 of the tube 140 ) can increase the thermal conductivity at Regarding the high thermal conductivity polymer composite, a high conductivity polymer composite using PP and PPS polymer as a matrix and graphite as a filler of TechnoForm GmbH of Germany may be applied. In the case of the low-temperature exhaust gas heat recovery polymer heat exchanger 100, which is an embodiment of the present invention, when installed in a plant low-temperature exhaust gas path, considering that the convective heat transfer coefficient is 60 to 80 W/m ² K on average, if the thermal conductivity is >2 W/mK It can be evaluated to have a heat transfer area equal to that of a stainless-based material used as a low-temperature corrosion resistance heat exchanger material.

In one embodiment of the present invention, the tube 140 through which heat exchange is performed includes a high-conductivity polymer composite, and has excellent thermal conductivity, corrosion resistance, chemical resistance, light weight, fabrication, pressure resistance, processability, etc. compared to conventional polymers, and a surface Because of its smoothness, it has excellent fouling and adhesion resistance.

Meanwhile, the inside of the tube 140 of the gas-gas low-temperature heat exchanger 100 has a low heat transfer coefficient. To overcome this, as shown in FIG. 2 , a tube insert 145 capable of disturbing fluid flow is installed inside the tube 140 . The tube insert 145 may have various shapes, and in this embodiment, the tube insert 145 in the form of entangled lines is disclosed, but is not limited thereto, such as a spiral tube insert or a porous mesh tube insert. Tube inserts having other shapes may also be applied.

By inserting the tube insert 145 into the tube 140, the intensity of turbulence within the tube 140 is strengthened to increase fluid mixing, thereby slowing down the formation of a thermal boundary layer and increasing the heat transfer coefficient, thereby enhancing heat transfer performance.

Combustion air or water flows inside the tube 140, and low-temperature exhaust gas flows outside the tube to preheat the air or water passing through the tube 140. However, in the present invention, the fluid flowing through the fluid inlet 110, the tube 140, and the fluid outlet 120 is not limited to air or water, and may be other liquid or gaseous materials.

In addition, the insertion of the tube insert 145 at the curved portion 143 of the tube 140 may be more difficult than the insertion of the tube insert 145 at the first and second extension portions 142 and 144, in this case It is also possible to install the tube insert 145 on the curved part 143 and then connect it to the tube insert 145 installed on the first and second extension parts 142 and 144 .

As shown in FIGS. 3 and 4, in one embodiment, the arrangement of the plurality of tubes fixed to the distribution plate 130 may be arranged in an in-line arrangement as shown in FIG. 3, or staggered as shown in FIG. Tubes 140 may be arranged, and this arrangement may be determined by the required heat exchange amount and pressure drop design.

In one embodiment of the present invention, the low-temperature exhaust gas includes exhaust gas having a temperature of about 250 ° C. or less, and when such low-temperature exhaust gas is supplied, heat exchange performance is secured in the case of the heat exchanger 100 according to an embodiment of the present invention, so that the tube 140 ) surface can form a temperature low enough for water vapor to condense, and accordingly, some SOx and NOx in the flue gas condense and form a solution on the surface of the melting furnace.

In addition, since the surface temperature of the tube 140 falls below the dew point temperature of the water vapor contained in the exhaust gas at the exhaust gas pressure, the water vapor is condensed, and the dew point temperature of sulfuric acid, hydrochloric acid, nitric acid, etc. present as gases in the exhaust gas is higher than the steam dew point temperature. Therefore, the mentioned SOx and NOx are condensed on the surface of the heat exchanger and washed down with the condensate water, so cleaning and low-temperature corrosion can be prevented. Since SO ₂ and NO ₂ gases have good solubility in water, they are dissolved in pre-condensed water and washed away. Therefore, it is possible to avoid low-temperature corrosion and wash by applying a heat exchanger made of polymer material at the same time as recovering the heat of the existing low-temperature exhaust gas discharged to the atmosphere, and it is possible to remove some fouling contained in the exhaust gas. Condensation of water vapor on the surface of the low-temperature heat exchanger prevents generation of white smoke in the air, and it is possible to remove SOx and NOx, precursors of ultra-fine dust.

In addition, in the case of sulfuric acid, condensed water is diluted but sticky, so that the surface of the tube can be cleaned by periodically spraying the water spray 160 disposed toward the tube 140, and the heat transfer performance can be restored by removing fouling.

5 shows another embodiment of the present invention. In the case of FIG. 5, a plurality of bundles 100a and 100b including the fluid inlet 110, the tube 140, and the fluid outlet 120 of the heat exchanger 100 shown in FIG. 1 are provided, and these bundles are parallel. A connection is shown.

As shown in FIG. 5, in the case of the embodiment of FIG. 5, the fluid inlet 110, the fluid outlet 120, and the tube 140 form a set (bundle), and two bundles 100a and 100b are arranged side by side, It can be seen that the fluid is supplied/discharged in parallel to the two bundles 100a and 100b. However, the present invention is not limited to the parallel connection, and depending on the heat exchange amount of one bundle, only a single bundle (100a, 100b) is used, or a plurality of bundles (100a, 100b) are connected in series or in parallel to exhaust gas Can be placed in piping. The number and shape of these bundles 100a and 100b are determined by the amount of heat transfer, the final temperature of the required fluid, the pressure drop, and the available space.

6 shows a schematic diagram of a combustion air preheating system 1 including a low-temperature flue gas heat recovery polymer heat exchanger 100 according to an embodiment of the present invention.

As shown in FIG. 6 , the low-temperature flue gas heat recovery polymer heat exchanger 100 according to an embodiment of the present invention can be applied to a combustion air preheating system 1 including a boiler 10 .

The combustion air preheating system 1 includes a boiler 10 or furnace; An air inlet path for providing air to the boiler 10 (dotted line in FIG. 6 ), an exhaust gas path combusted in the boiler 10 (solid line in FIG. 6 ), and metal heat exchange disposed on the air inlet path and the exhaust gas path It may include a group 20 and a low-temperature exhaust gas heat recovery polymer heat exchanger 100.

Combustion air is primarily heated from the outside through the low-temperature flue gas heat recovery polymer heat exchanger 100, and then passed through the metal heat exchanger 20 to be heated secondarily and raised to a sufficient temperature to be returned to the boiler 10. can be provided. In particular, by applying the low-temperature exhaust gas heat recovery polymer heat exchanger 100 of the present invention in a low-temperature part where it is difficult to apply the metal heat exchanger 20 due to corrosive materials, the low-temperature exhaust gas is not directly discarded to the outside through the flue 30 and energy is saved. It can be recycled, and gases such as SO ₂ and NO ₂ in the exhaust gas and water vapor are also removed through the low-temperature exhaust gas heat recovery polymer heat exchanger 100, reducing white smoke and having a good impact on the environment.

In the above, the embodiment of the present invention has been mainly described, but the present invention is not limited to the embodiment and can be variously modified and implemented.

1: Combustion air preheating system 10: Boiler
20: metal heat exchanger 30: flue
100: low-temperature exhaust gas heat recovery polymer heat exchanger
110: fluid inlet 120: fluid outlet
130: distribution plate 140: tube
145: tube insert 150: support plate

Claims (9)

It is placed on the path of low-temperature exhaust gas,
a fluid inlet and a fluid outlet disposed on one side; and
A plurality of tubes extending from the fluid inlet to the fluid outlet and having a U-shape as a whole; includes,
The plurality of tubes are a low-temperature exhaust gas heat recovery polymer heat exchanger comprising a polymer composite in which at least one of carbon, ceramic, and metal particles is included as a filler in a pure polymer.
According to claim 1,
A water spray spray for spraying water toward the plurality of tubes. The low-temperature exhaust gas heat recovery polymer heat exchanger, characterized in that it further comprises a distribution plate connecting the fluid inlet and fluid outlet and the plurality of tubes, and a support plate disposed in the middle of the tube and fixing the tube.
According to claim 1,
Low-temperature exhaust gas heat recovery polymer heat exchanger, characterized in that the fluid flow through the fluid inlet, the plurality of tubes and the fluid inlet is arranged to form a counter flow with the exhaust gas.
According to claim 3,
The fluid inlet and fluid outlet are disposed on the upper side,
The tube includes a first extension connected to the fluid inlet and extending vertically, a second extension connected to the fluid outlet and extending vertically, and a lower end of the first extension and a lower end of the second extension being bent. Low-temperature flue gas heat recovery polymer heat exchanger including a curved portion connecting.
According to claim 3,
The inside of the tube is a low-temperature exhaust gas heat recovery polymer heat exchanger, characterized in that a tube insert extending along the tube is inserted.
According to claim 3,
the fluid inlet includes a first fluid inlet and a second fluid inlet;
the fluid outlet includes a first fluid outlet and a second fluid outlet;
The plurality of tubes include a plurality of first tubes connecting the first fluid inlet and the first fluid outlet and a plurality of second tubes connecting the second fluid inlet and the second fluid outlet,
the first fluid inlet and the second fluid inlet are connected in parallel to a fluid source;
The first fluid outlet and the second fluid outlet are low-temperature exhaust gas heat recovery polymer heat exchanger, characterized in that connected in parallel to the fluid outlet.
According to claim 5,
The fluid inlet and fluid outlet are disposed on the upper side,
Low-temperature exhaust gas heat recovery polymer heat exchanger, characterized in that it further comprises a water injection nozzle disposed toward the tube at a lower portion than the fluid inlet and the fluid outlet.
According to claim 7,
The water spray nozzle is a low-temperature exhaust gas heat recovery polymer heat exchanger, characterized in that disposed toward the tube from the upstream side of the exhaust gas.
a heat source unit in which combustion occurs;
an inlet passage for supplying air to the heat source;
a discharge path through which the gas generated from the heat source unit is exhausted;
a metal heat exchanger for exchanging heat between the inlet passage and the air passing through the outlet passage; and
A polymer heat exchanger disposed downstream of the metal heat exchanger on the discharge passage and exchanging heat between the air before flowing into the metal heat exchanger and the gas on the discharge passage;
The polymer heat exchanger is the low-temperature exhaust gas heat recovery polymer heat exchanger according to any one of claims 1 to 8. Combustion air preheating system.

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