Waste heat recovery device

Abstract

Provided is a waste heat recovery device. A waste heat recovery device according to the present invention comprises: an evaporator for heating a working fluid with exhaust gas to provide superheated steam; a condenser for condensing the superheated steam to exchange heat with a fluid to be heated, and discharging a supercooled liquid; and a preheater which is disposed between the condenser and the evaporator and heats the supercooled liquid with a portion of the exhaust gas and provides the same to the evaporator.

Description

Array recovery device

[0001] The present invention relates to an array recovery device.

[0002] In general, the array recovery device performs combustion air, steam generation, and feedwater preheating by passing unused flue gas, such as combustion flue gas, which is discharged after a process and has a temperature of 300℃ or higher, through a heat exchanger installed therein to be fed into a furnace.

[0003] Heat exchangers utilize either bare tubes or finned tubes, depending on the flue gas composition, temperature, and flow rate. Since flue gas is discharged into the atmosphere through a stack at temperatures exceeding 150°C, consideration of heat exchanger materials to prevent low-temperature corrosion is also crucial.

[0004] Conventional exhaust gas recovery systems employ forced convection, with exhaust gas flowing along the outside of the heat exchanger and the working fluid flowing along the inside. This increases the convective heat transfer coefficient within the heat exchanger tubes and enables rapid operation control.

[0005] Meanwhile, preheating combustion air by utilizing discarded flue gas saves fuel as much as the heat recovery.

[0006] When steam is generated using an array, the generated steam can drive a turbine according to its temperature and flow rate to generate electricity and can be used as steam for other processes. It increases the efficiency of the plant when preheating feedwater. From an environmental perspective, it reduces carbon dioxide (CO2) and sulfur oxides (SO2) by reducing energy use. X ), nitrogen oxides (NO X ) can contribute to reduction.

[0007] However, in the case of a forced circulation type array recovery device, a separate additional circulation device such as a pump or flow control device was required for forced circulation of the working fluid.

[0008] The present invention aims to provide an array recovery device that can be operated continuously according to the array capacity without using a separate additional circulation control device such as a pump or a flow control device for forced circulation of the working fluid and can naturally circulate the working fluid.

[0009] An array recovery device according to one embodiment of the present invention may include an evaporator that heats a working fluid with exhaust gas to provide superheated steam, a condenser that condenses the superheated steam to exchange heat with a heated fluid and discharges a subcooled liquid, and a preheater that is disposed between the condenser and the evaporator and heats the subcooled liquid with a portion of the exhaust gas to provide the subcooled liquid to the evaporator.

[0010] It may include a purge device disposed between the evaporator and the condenser and for purge-ing non-condensable gas among the gas flowing from the evaporator to the condenser.

[0011] The working fluid may consist of water to create a natural circulation flow through the evaporator, condenser and preheater.

[0012] The evaporator, condenser, and preheater can all be made of fin-tube type heat exchangers.

[0013] Additionally, the heat exchanger tubes of the evaporator can be arranged in a sweeping direction with respect to the inflow direction of the exhaust gas.

[0014] The heat exchanger tubes of the condenser can be arranged in a sweeping direction with respect to the inflow direction of the fluid to be heated.

[0015] Additionally, a tube insert may be installed inside the heat exchanger tube of the condenser to improve heat transfer performance within the heat exchanger tube.

[0016] The tube inserts may be of wire mesh type or twist type to improve condensation performance within the heat exchanger tubes.

[0017] The tube insert can be installed at a set height from the heat exchanger tube outlet.

[0018] In addition, a first automatic control valve may be installed on the inlet side of the evaporator to automatically control the flow rate of the subcooling liquid flowing into the evaporator from the preheater.

[0019] A second automatic control valve may be installed on the outlet side of the evaporator to automatically control the flow rate of superheated steam flowing from the evaporator to the condenser.

[0020] Additionally, the first automatic control valve and the second automatic control valve can be automatically controlled by the controller according to the flow rate, temperature, and pressure information of the exhaust gas and the heated fluid.

[0021] According to an embodiment of the present invention, continuous operation is possible according to the array capacity without using a separate additional circulation control device such as a pump or flow control device for forced circulation of the working fluid, and the working fluid can be naturally circulated.

[0022] That is, since the water, which is the working fluid flowing through the heat exchanger tubes of the evaporator and condenser, operates with a circulating force due to the vapor-liquid phase change, the pump device used in the forced circulation type heat recovery device is not required.

[0023] Therefore, the number of breakdowns is minimal and the flow of working fluid is generated according to the array capacity, so there is no need for the operation of a forced convection pump.

[0024] Additionally, fuel savings are achieved by increasing the recovery of exhaust gas arrays, and carbon dioxide (CO2), sulfur oxides (SO2) are reduced. X ), nitrogen oxides (NO X ) can also be reduced.

[0025] FIG. 1 is a schematic diagram of an array recovery device according to one embodiment of the present invention.

[0026] FIG. 2 is a partial detailed perspective view of an array recovery device according to one embodiment of the present invention.

[0027] Figure 3 is a graph comparing the improvement in thermal efficiency (performance) according to the fuel gas temperature at the evaporator inlet depending on whether a tube insert is installed in the heat exchanger tube of the condenser.

[0028] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described so that those skilled in the art can easily implement them. As will be readily apparent to those skilled in the art, the embodiments described below may be modified in various ways without departing from the spirit and scope of the present invention. Wherever possible, identical or similar parts are indicated in the drawings using the same reference numerals.

[0029] The terminology used below is for the purpose of describing specific embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other specific features, regions, integers, steps, operations, elements, components, and / or groups.

[0030] All terms, including technical and scientific terms, used below have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention pertains. Terms defined in the dictionary are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0031] FIG. 1 is a schematic diagram of an array recovery device according to one embodiment of the present invention, and FIG. 2 is a partially detailed perspective view of an array recovery device according to one embodiment of the present invention.

[0032] Referring to FIGS. 1 and 2, an array recovery device according to one embodiment of the present invention may include an evaporator (100), a condenser (200), a preheater (300), and a purge device (400).

[0033] At least one evaporator (100) is provided and can heat the working fluid with exhaust gas (10) to provide superheated steam.

[0034] In addition, at least one condenser (200) is provided, and can condense superheated steam to exchange heat with the heated fluid (11) and discharge the supercooled liquid.

[0035] And, the preheater (300) is placed between the condenser (200) and the evaporator (100), and can heat the subcooled liquid as part of the exhaust gas (10) and provide it to the evaporator (100).

[0036] In addition, the extraction device (400) is disposed between the evaporator (100) and the condenser (200), and can extract non-condensable gas (13) from the gas flowing from the evaporator (100) to the condenser (200) in order to maintain the heat exchange efficiency of the condenser (200).

[0037] Here, the working fluid may be made of water or the like so as to create a natural circulation flow through the evaporator (100), condenser (200), and preheater (300).

[0038] Additionally, the heated fluid (11) may be composed of any one selected from combustion air, gas fuel, steam, feedwater, etc.

[0039] In Fig. 1, three evaporators (100) are illustrated, but this is not limited to the number of evaporators, and three or fewer or three or more may be arranged. In addition, three condensers (200) are illustrated, but this is not limited to the number of condensers, and two or fewer or three or more may be arranged.

[0040] The evaporator (100), condenser (200), and preheater (300) may all be fin-tube type heat exchangers to expand the heat transfer area. Here, the fin-tube type may refer to a form in which fins (203 - shown only in the condenser of FIG. 2) protrude at set intervals on the outer surface of a cylindrical tube, as illustrated in FIG. 2.

[0041] The heat exchanger tubes (101, 102, 103) of the evaporator (100) can be arranged in a sweeping direction with respect to the inflow direction of the exhaust gas (10) so as to create a cross flow with the exhaust gas (10) for easy absorption of the exhaust gas (10) array.

[0042] Additionally, the heat exchanger tubes (201, 202, 203) of the condenser (200) can be arranged in a sweeping direction with respect to the inflow direction of the heated fluid (11) so as to create a cross flow with the heated fluid (11) for easy heating of the heated fluid (11).

[0043] A tube insert (210) that improves the heat transfer performance within the heat exchanger tubes (201, 202, 203) of the condenser (200) can be installed to improve the heat recovery performance.

[0044] The tube insert (210) may be formed of a wire mesh tube insert or a twist type, etc., which improves the condensation performance within the heat exchanger tubes (201, 202, 203), as shown in FIG. 2.

[0045] In this way, by installing the tube insert (210) within the condenser (200), the thickness of the thermal boundary layer does not increase in the downstream direction of the heat exchanger tubes (201, 202, 203) installed at a set angle, for example, vertically, with respect to the inflow direction of the heated fluid (11).

[0046] This is because the thermal boundary layer of the condensate is disturbed and thinned by wire mesh, etc. as the condensate flows along the wall of the heat exchanger tube (201, 202, 203).

[0047] However, the evaporator (100) and the preheater (300) are not equipped with tube inserts like the condenser (200).

[0048] In addition, the tube insert (210) is installed from the outlet of the heat exchanger tube (201, 202, 203) of the condenser (200) to further improve the heat transfer performance within the heat exchanger tube (201, 202, 203), and the height can be determined depending on the degree of improvement in condensation heat transfer.

[0049] This is because when a tube insert is installed in the evaporator (100), the boiling start time is delayed and the tube insert acts as a thermal resistance, lowering the evaporation efficiency. Similarly, when a tube insert is installed in the preheater (300), the preheating start time is delayed and the tube insert acts as a thermal resistance, lowering the preheating efficiency.

[0050] The exhaust gas (10) can be transported from the furnace (30) to the evaporator (100) by the first line (21), and the heated heated fluid (11) that has passed through the condenser (200) can be transported to the furnace (30) by the second line (22).

[0051] Additionally, the exhaust gas (10) passing through the evaporator (100) can be discharged to the chimney (40) through the third line (23).

[0052] Superheated steam passing through each heat exchange tube (101, 102, 103) of the evaporator (100) can be transferred to the condenser (200) by the fourth line (24-1, 24-2, 24-3).

[0053] That is, each heat exchanger tube (101, 102, 103) of the evaporator (100) can be correspondingly connected to each heat exchanger tube (201, 202, 203) of the condenser (200) by the fourth line (24-1, 24-2, 24-3), as shown in FIG. 1.

[0054] The preheater (300) is connected to the heat exchange tubes (201, 202, 203) of the condenser (200) and the fifth line (25-1, 25-2, 25-3), and the preheater (300) can be connected to the heat exchange tubes (101, 102, 103) of the evaporator (100) and the sixth line (26-1, 26-2, 26-3), respectively.

[0055] The exhaust device (400) can be installed in a branch line (27) branched from the fourth line (24-1, 24-2, 24-3) to effectively exhaust non-condensable gas (13).

[0056] In addition, a first automatic control valve (311, 312, 313) may be installed on the inlet side of the evaporator (100) to automatically control the flow rate of the subcooled liquid flowing into the evaporator (100) from the preheater (300) in order to maximize the efficiency of the natural circulation type array recovery device according to the flow rate, temperature, and pressure of the exhaust gas (10) and the heated fluid (11).

[0057] That is, the first automatic control valve (311, 312, 313) can automatically control the flow rate of the subcooling liquid flowing from the preheater (300) into each heat exchange tube (101, 102, 103) of the evaporator (100).

[0058] In addition, a second automatic control valve (321, 322, 323) may be installed on the outlet side of the evaporator (100) to automatically control the flow rate of superheated steam flowing from the evaporator (100) to the condenser (200) in order to maximize the efficiency of the natural circulation type array recovery device according to the flow rate, temperature, and pressure of the exhaust gas (10) and the heated fluid (11).

[0059] That is, the second automatic control valves (321, 322, 323) can automatically control the flow rate of superheated steam flowing from each heat exchange tube (101, 102, 103) of the evaporator (100) to each heat exchange tube (201, 202, 203) of the condenser (200).

[0060] The first automatic control valve (311, 312, 313) and the second automatic control valve (321, 322, 323) can be automatically controlled by a controller (not shown) that receives information on the flow rate, temperature, and pressure of the exhaust gas (10) and the heated fluid (11) according to the information on the flow rate, temperature, and pressure of the exhaust gas (10) and the heated fluid (11).

[0061] Hereinafter, with reference to FIGS. 1 and 2, the operation of an array recovery device according to one embodiment of the present invention will be described.

[0062] Below, an example using water as a working fluid is described.

[0063] First, the exhaust gas discharged from the furnace (30) is transferred to the evaporator (100) through the first line (21).

[0064] At this time, the exhaust gas transferred to the evaporator (100) is introduced in a sweeping direction for each heat exchanger tube (101, 102, 103) of the evaporator (100) and flows to the fin (not shown) side of each heat exchanger tube (101, 102, 103) to create a cross flow, and water flows inside the heat exchanger tube (101, 102, 103) of the evaporator (100) and absorbs the array of exhaust gas (10) to evaporate and change into superheated steam.

[0065] In this way, as the water changes phase into superheated steam, the superheated steam that has absorbed the exhaust gas (10) array flows from each heat exchange tube (101, 102, 103) of the evaporator (100) into each heat exchange tube (201, 202, 203) of the condenser (200) through the second line (22).

[0066] At this time, the exhaust device (400) installed in the branch line (27) of the fourth line (24) between the heat exchange tubes (101, 102, 103) of the evaporator (100) and the heat exchange tubes (201, 202, 203) of the condenser (200) can maintain the heat exchange efficiency of the condenser (200) by exhausting the non-condensable gas (13) among the gas flowing from the evaporator (100) to the condenser (200) through the fourth line (24).

[0067] The superheated steam introduced into the heat exchanger tubes (201, 202, 203) of the condenser (200) flows into the heat exchanger tubes (201, 202, 203) and releases the heat absorbed in the evaporator (100) to the heated fluid (11) introduced into the fin (203) side of each heat exchanger tube (201, 202, 203) of the condenser (200), thereby preheating the heated fluid (11) and condensing it to change into a subcooled liquid.

[0068] At this time, as shown in FIG. 2, a wire mesh tube insert (210) is installed in the heat exchanger tube (201, 202, 203) of the condenser (200), so that the heat transfer performance within the heat exchanger tube (201, 202, 203), i.e., the condensation performance, can be improved, thereby improving the array recovery performance.

[0069] In this way, a tube insert (210) is installed in each heat exchange tube (201, 202, 203) of the condenser (200) so that the thickness of the thermal boundary layer does not increase in the downstream direction of the heat exchanger tube (201, 202, 203) installed vertically, for example, with respect to the inflow direction of the heated fluid (11).

[0070] This is because the thermal boundary layer of the condensate is disturbed and thinned by the wire mesh as the condensate flows along the walls of the heat exchanger tubes (201, 202, 203).

[0071] Additionally, this supercoolant is transferred from each heat exchange tube (201, 202, 203) of the condenser (200) to the preheater (300) through the fifth line (25-1, 25-2, 25-3).

[0072] And, after being preheated by exhaust gas discharged through the third line (23) from the outlet side of each heat exchange tube (101, 102, 103) of the evaporator (100) in the preheater (300), it is transferred into each heat exchanger tube (101, 102, 103) of the evaporator (100) through the sixth line (26-1, 26-2, 26-3).

[0073] In this way, the preheater (300) installed between the condenser (200) and the evaporator (100) can increase the amount of water evaporated in the evaporator (100) by exchanging heat with the exhaust gas exiting the evaporator (100) and thereby causing a decrease in the degree of subcooling, since the degree of subcooling increases due to the tube insert (210) of the condenser (200).

[0074] And, the heated fluid that has passed through the fin (203) side of each heat exchanger tube (201, 202, 203) of the condenser (200) is heated by the heat released from the superheated steam in each heat exchanger tube (201, 202, 203) of the condenser (200) and is transferred to the furnace (30) through the second line (22).

[0075] As a result, the temperature of the heated fluid (11) increases, resulting in fuel savings equivalent to the increased amount of heat.

[0076] In addition, the exhaust gas passing through the fin side of the heat exchanger tube (not shown) of the preheater (300) is discharged to the stack (40) through the third line (23), and the subcoolant flowing inside the heat exchanger tube (not shown) of the preheater (300) is transferred into each of the heat exchanger tubes (101, 102, 103) of the evaporator (100) through the sixth line (26-1, 26-2, 26-3).

[0077] Meanwhile, the evaporator (100) and condenser (200) are operated in one or more bundles, and the exhaust gas flowing into the fins (not shown) of each heat exchanger tube (101, 102, 103) of the evaporator (100) creates a cross flow with each heat exchanger tube (101, 102, 103).

[0078] Additionally, the heated fluid flowing into the fins (203) of each heat exchanger tube (201, 202, 203) of the condenser (200) creates a cross flow with each heat exchanger tube (201, 202, 203).

[0079] At this time, the subcooling liquid flowing into the evaporator (100) bundle is automatically controlled by the first automatic control valve (311, 312, 313) according to the flow rate, temperature, and pressure of the exhaust gas and the heated fluid, and the superheated steam flowing out of the evaporator (100) bundle is automatically controlled by the second automatic control valve (321, 322, 323) according to the flow rate, temperature, and pressure of the exhaust gas and the heated fluid.

[0080] That is, each of the first automatic control valve (311, 312, 313) and the second automatic control valve (321, 322, 323) can be automatically controlled according to the flow rate, temperature, and pressure of the exhaust gas and the heated fluid by a control unit (not shown) that receives information on the flow rate, temperature, and pressure of the exhaust gas and the heated fluid.

[0081] In this way, the first automatic control valve (311, 312, 313) and the second automatic control valve (321, 322, 323) are automatically opened and closed according to the flow rate, temperature, and pressure of the exhaust gas and the heated fluid, so that the heat recovery efficiency of the array recovery device can be maximized through natural circulation of the working fluid.

[0082] In addition, a certain height is maintained within the heat exchanger tubes (101, 102, 103) of the evaporator, and the outlet of the evaporator (100) is configured so that the superheated temperature is controlled to, for example, within 3 to 5°C so that the superheated vapor does not condense while moving to the condenser (200).

[0083] In addition, the tube insert (210) in the heat exchanger tube (201, 202, 203) of the condenser (200) is installed from the outlet of the heat exchanger tube (201, 202, 203) and the height is determined according to the degree of improvement in condensation heat transfer.

[0084] In addition, since the water, which is the working fluid flowing through each heat exchange tube (101, 102, 103) of the evaporator (100) and each heat exchanger tube (201, 202, 203) of the condenser (200), operates with a circulating force due to a vapor-liquid phase change, a pump device used in a forced circulation type heat recovery device is not required.

[0085] Therefore, the number of breakdowns is minimal and the flow of working fluid is generated according to the array capacity, so there is no need for the operation of a forced convection pump.

[0086] (Performance test results)

[0087] Figure 3 shows the thermal efficiency and performance according to the fuel gas temperature at the inlet of the evaporator (EVA: EVAPORATOR) depending on the presence or absence of a tube insert (210) installed in the heat exchanger tube (201) of the condenser (200).

[0088] Baseline is when the tube insert (210) is not installed in the heat exchanger tube (201), and hiTran (product of CalGavin) is when the tube insert (210) is installed in the heat exchanger tube (201).

[0089] As shown in FIG. 3, the thermal efficiency increases as the exhaust gas temperature of the evaporator (EVA) (100) increases, and when the tube insert (210) of the condenser (200) is installed, the thermal efficiency increases by 3% at an exhaust gas temperature of 297°C.

[0090] Although the present disclosure has been described through preferred embodiments as described above, it will be readily understood by those skilled in the art that the present invention is not limited thereto and that various modifications and variations are possible without departing from the scope of the claims set forth below.

Claims

1. An evaporator that heats the working fluid with exhaust gas to provide superheated steam; A condenser that condenses the superheated steam, exchanges heat with the heated fluid, and discharges the supercooled liquid, and A preheater disposed between the condenser and the evaporator, and heating the subcooled liquid as part of the exhaust gas and providing it to the evaporator An array recovery device comprising:

2. In paragraph 1, An array recovery device, comprising a extraction device disposed between the evaporator and the condenser and configured to extract non-condensable gas from among gas flowing from the evaporator to the condenser.

3. In paragraph 1 or 2, An array recovery device wherein the working fluid comprises water to create a natural circulation flow through the evaporator, the condenser and the preheater.

4. In paragraph 3, An array recovery device, wherein the above evaporator, the above condenser, and the above preheater are all composed of fin-tube type heat exchangers.

5. In paragraph 4, An array recovery device in which the heat exchanger tubes of the above evaporator are arranged in a sweeping direction with respect to the inflow direction of the exhaust gas.

6. In paragraph 5, An array recovery device in which the heat exchanger tubes of the above condenser are arranged in a sweeping direction with respect to the inflow direction of the heated fluid.

7. In paragraph 6, An array recovery device, wherein a tube insert is installed inside the heat exchanger tube of the above condenser to improve heat transfer performance within the heat exchanger tube.

8. In paragraph 7, An array recovery device wherein the above tube insert is made of a wire mesh type or a twist type to improve the condensation performance within the heat exchanger tube.

9. In paragraph 8, An array recovery device wherein the above tube insert is installed at a set height from the heat exchanger tube outlet of the condenser.

10. In paragraph 3, An array recovery device, wherein a first automatic control valve is installed on the inlet side of the evaporator to automatically control the flow rate of the supercooled liquid flowing into the evaporator from the preheater.

11. In paragraph 10, An array recovery device, wherein a second automatic control valve is installed on the outlet side of the evaporator to automatically control the flow rate of superheated steam flowing from the evaporator to the condenser.

12. In paragraph 11, An array recovery device in which the first automatic control valve and the second automatic control valve are automatically controlled by a controller according to information on the flow rate, temperature, and pressure of the exhaust gas and the heated fluid.

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