Heat recovery apparatus

Abstract

The present application relates to a heat recovery apparatus and a method thereof, according to the heat recovery apparatus and a method thereof according to an embodiment of the present application, steam of 120 C. or more may be generated using only one heat exchanger using waste heat of a low-grade heat source in the state of a sensible heat of 70 C. or more discharged in industrial sites or various chemical processes, for example, such as a manufacturing process of petrochemicals, and the generated steam may also be used in various processes, and thus the use of high temperature steam which is an external heat source to be used in a reactor or a distillation column may be decreased, thereby maximizing energy saving efficiency.

Claims

1. A heat recovery apparatus, comprising: a first heat exchanger, a compressor, a second heat exchanger, and a pressure drop device which are fluidically connected through a pipe through which a refrigerant flows, wherein a refrigerant flow flowing into the first heat exchanger is heat-exchanged with a fluid flow of 70 C. or more flowing into the first heat exchanger, the refrigerant flow flowing out of the first heat exchanger flows into the compressor, the refrigerant flow flowing out of the compressor flows into the second heat exchanger, and is heat-exchanged with a fluid flow flowing into the second heat exchanger, the refrigerant flow flowing out of the second heat exchanger flows into the pressure drop device, the refrigerant flow flowing out of the pressure drop device reflows into the first heat exchanger, and a ratio between a pressure of the refrigerant flow flowing out of the first heat exchanger and a pressure of the refrigerant flow flowing out of the compressor satisfies the following Expression 1:
3.1P.sub.C/P.sub.H4.2[Expression 1] where, in Expression 1, P.sub.C denotes a pressure of the refrigerant flow flowing out of the compressor, and P.sub.H denotes a pressure of the refrigerant flow flowing out of the first heat exchanger, wherein the fluid flowing into the second heat exchanger is water, and the water which is heat-exchanged in the second heat exchanger is discharged as steam, and wherein a temperature of the steam is 120 C. or more.

2. The heat recovery apparatus of claim 1, wherein the fluid flow flowing into the first heat exchanger is a waste heat flow or a flow of condensate passed through a condenser.

3. The heat recovery apparatus of claim 1, wherein a temperature of the refrigerant flow flowing out of the first heat exchanger and a temperature of the fluid flow flowing into the first heat exchanger satisfy the following Expression 2:
1 C.T.sub.FT.sub.R20 C.[Expression 2] where, in Expression 2, T.sub.F denotes a temperature of the fluid flow flowing into the first heat exchanger, and T.sub.R denotes a temperature of the refrigerant flow flowing out of the first heat exchanger.

4. The heat recovery apparatus of claim 1, wherein a flow rate of the refrigerant is in the range of 5,000 to 231,000 kg/hr.

5. The heat recovery apparatus of claim 1, wherein a temperature of the refrigerant flow flowing into the first heat exchanger is in the range of 60 to 105 C.

6. The heat recovery apparatus of claim 1, wherein a flow rate of the fluid flow flowing into the first heat exchanger is in the range of 50,000 to 2,300,000 kg/hr.

7. The heat recovery apparatus of claim 1, wherein a temperature of the fluid flow flowing out of the first heat exchanger is in the range of 68 to 102 C.

8. The heat recovery apparatus of claim 1, wherein a temperature of the refrigerant flow flowing out of the first heat exchanger is in the range of 65 to 105 C.

9. The heat recovery apparatus of claim 1, wherein a pressure of the refrigerant flow flowing out of the first heat exchanger is in the range of 3.0 to 20.0 kgf/cm.sup.2g.

10. The heat recovery apparatus of claim 1, wherein a temperature of the refrigerant flow flowing out of the compressor is in the range of 125 to 185 C.

11. The heat recovery apparatus of claim 1, wherein a pressure of the refrigerant flow flowing out of the compressor is in the range of 9.0 to 62.5 kgf/cm.sup.2g.

12. The heat recovery apparatus of claim 1, wherein a flow rate of the fluid flow flowing into the second heat exchanger is in the range of 500 to 10,000 kg/hr.

13. The heat recovery apparatus of claim 1, wherein a temperature of the water flowing into the second heat exchanger is in the range of 70 to 105 C.

14. The heat recovery apparatus of claim 1, wherein a pressure of the steam is in the range of 0.99 to 10.5 kgf/cm.sup.2g.

15. The heat recovery apparatus of claim 1, further comprising one or more steam compressors configured to compress the steam.

16. The heat recovery apparatus of claim 1, further comprising one or more steam condensers configured to condense the steam.

17. The heat recovery apparatus of claim 1, wherein a temperature of the refrigerant flow flowing out of the second heat exchanger is in the range of 125 to 190 C.

18. The heat recovery apparatus of claim 1, wherein a temperature of the refrigerant flow flowing out of the pressure drop device is in the range of 65 to 105 C.

19. A heat recovery method, comprising: a refrigerant circulation step in which a refrigerant flow flows into a first heat exchanger, the refrigerant flow flowing out of the first heat exchanger flows into a compressor, the refrigerant flow flowing out of the compressor flows into a second heat exchanger, the refrigerant flow flowing out of the second heat exchanger flows into a pressure drop device, and the refrigerant flow flowing out of the pressure drop device flows into the first heat exchanger; a first heat exchange step in which the refrigerant flow flowing into the first heat exchanger is heat-exchanged with a fluid flow of 70 C. or more flowing into the first heat exchanger; a second heat exchange step in which the refrigerant flow flowing out of the compressor exchanger is heat-exchanged with a fluid flow of flowing into the second heat exchanger; and a pressure adjustment step in which a ratio between a pressure of the refrigerant flow flowing out of the first heat exchanger and a pressure of the refrigerant flow flowing out of the compressor is adjusted to satisfy the following Expression 1:
3.1P.sub.C/P.sub.H4.2[Expression 1] where, in Expression 1, P.sub.C denotes a pressure of the refrigerant flow flowing out of the compressor, and P.sub.H denotes a pressure of the refrigerant flow flowing out of the first heat exchanger, wherein the fluid flowing into the second heat exchanger is water, and the water which is heat-exchanged in the second heat exchanger is discharged as steam, and wherein a temperature of the steam is 120 C. or more.

20. The heat recovery method of claim 19, wherein the fluid flow flowing into the first heat exchanger is a waste heat flow or a flow of condensate passed through a condenser.

21. The heat recovery method of claim 19, further comprising adjusting a temperature of the refrigerant flow flowing out of the first heat exchanger and a temperature of the fluid flow flowing into the first heat exchanger to satisfy the following Expression 2:
1 C.T.sub.FT.sub.R20 C.[Expression 2] where, in Expression 2, T.sub.F denotes a temperature of the fluid flow flowing into the first heat exchanger, and T.sub.R denotes a temperature of the refrigerant flow flowing out of the first heat exchanger.

22. The heat recovery method of claim 19, wherein a pressure of the steam is in the range of 0.99 to 10.5 kgf/cm.sup.2g.

23. The heat recovery method of claim 19, further comprising compressing the steam.

24. The heat recovery method of claim 19, further comprising condensing the steam.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a view schematically showing a conventional waste heat disposal device.

(2) FIG. 2 is a view schematically illustrating a heat recovery apparatus according to an embodiment of the present application.

(3) FIG. 3 is a graph exemplarily showing a temperature-entropy of the waste heat recovery apparatus and method according to the embodiment of the present application.

(4) FIG. 4 is a view showing the heat recovery apparatus according to the embodiment of the present application.

MODES OF THE INVENTION

(5) Hereinafter, the present application will be described in greater detail in conjunction with examples according to an embodiment of the present application and comparative examples not according to the embodiment of the present application, but the scope of the present application is not limited to the following examples.

Example 1

(6) Steam was generated using a heat recovery apparatus of FIG. 4.

(7) A refrigerant (1,1,1,3,3-pentafluoropropane, R245fa) was circulated at a flow rate of 30,000 kg/hr such that the refrigerant sequentially passes through a first heat exchanger, a compressor, a second heat exchanger, and a control valve. Specifically, a refrigerant flow in the state of 75.4 C., 6.2 kgf/cm.sup.2 g (7.1 bar) with a gas volume fraction of 0.0 flowed into the first heat exchanger, and at the same time, the waste heat flow in the state of 85.0 C., 1.0 kgf/cm.sup.2 g (2.0 bar) with the gas volume fraction of 0.0 flowed into the first heat exchanger at a flow rate of 300,000 kg/hr for heat exchange. After the heat exchange in the first heat exchanger, the waste heat flow in the state of 83.3 C., 1.0 kgf/cm.sup.2 g with the gas volume fraction of 0.0 flowed out at a flow rate of 30,000 kg/hr, the refrigerant flow in the state of 80 C., 6.2 kgf/cm.sup.2 g (7.1 bar) with the gas volume fraction of 1.0 flowed out, and then the refrigerant flow flowed into the compressor. Further, the refrigerant flow compressed in the compressor flowed out of the compressor while being in the state of 127 C., 21.4 kgf/cm.sup.2 g (22.0 bar) with the gas volume fraction of 0.88. Here, the amount of work used in the compressor was 220,404 W. The refrigerant flow which flowed out of the compressor flowed into the second heat exchanger, and at the same time, water in the state of 100 C., 0.99 kgf/cm.sup.2 g (1.98 bar) with the gas volume fraction of 0.0 flowed into the second heat exchanger at a flow rate of 2,000 kg/hr for the heat exchange with the refrigerant flow. After the heat exchange, the water was discharged as the steam in the state of 120 C., 0.99 kgf/cm.sup.2 g with the gas volume fraction of 1.0, the refrigerant flow was condensed and flowed out while being in the state of 126 C., 21.4 kgf/cm.sup.2 g (22.0 bar) with the gas volume fraction of 0.0, and then flowed into the control valve. Further, the refrigerant flow which passed through the control valve flowed out of the control valve while being in the state of 75.4 C., 6.2 kgf/cm.sup.2 g (7.1 bar) with the gas volume fraction of 0.66, and then reflowed into the first heat exchanger.

(8) Here, in the pressure drop device, an electrical power of 72,874 W was generated using mechanical energy of the fluid flow. Further, coefficient of performance of the heat recovery apparatus was calculated by the following Expression 4, and shown in the following Table 1.

(9) $\begin{array}{cc}\mathrm{COP}=\frac{Q}{W}& \left[\mathrm{Expression}4\right]\end{array}$

(10) In Expression 4, Q denotes the quantity of heat of condensation generated in the second heat exchanger, and W denotes the amount of work done by the compressor.

Example 2

(11) The steam was generated in the same manner as in Example 1 except that the refrigerant flow in the state of 75.4 C., 6.2 kgf/cm.sup.2 g (7.1 bar) with the gas volume fraction of 0.0 flowed into the first heat exchanger, and at the same time, the waste heat flow in the state of 95 C., 1.0 kgf/cm.sup.2 g (2.0 bar), the gas volume fraction of 0.0 flowed into the first heat exchanger at a flow rate of 300,000 kg/hr for the heat exchange, the heat was exchanged in the first heat exchanger, the refrigerant flow in the state of 90 C., 6.2 kgf/cm.sup.2 g (7.1 bar) with the gas volume fraction of 1.0 flowed into the compressor, the refrigerant flow compressed in the compressor flowed out of the compressor while being in the state of 133 C., 24.3 kgf/cm.sup.2 g (24.8 bar) with the gas volume fraction of 1.0, the refrigerant flow flowed into the second heat exchanger and was heat-exchanged with the water of 100 C., the heat-exchanged refrigerant flow in the state of 132 C., 24.3 kgf/cm.sup.2 g (24.8 bar) with the gas volume fraction of 0.0 flowed out, and flowed into the pressure drop device. Here, the coefficient of performance of the heat recovery apparatus and the temperature of the steam were shown in the following Table 1.

Example 3

(12) The steam was generated in the same manner as in Example 1 except that the refrigerant flow in the state of 68.5 C., 5.0 kgf/cm.sup.2 g (5.9 bar) with a gas volume fraction of 0.0 flowed into the first heat exchanger, and at the same time, the waste heat flow in the state of 95 C., 1.0 kgf/cm.sup.2 g with the gas volume fraction of 0.0 flowed into the first heat exchanger at a flow rate of 300,000 kg/hr for the heat exchange, the heat was exchanged in the first heat exchanger, the refrigerant flow in the state of 90 C., 5.0 kgf/cm.sup.2 g (5.9 bar) with the gas volume fraction of 1.0 flowed into the compressor, the refrigerant flow compressed in the compressor flowed out of the compressor while being in the state of 133 C., 24.3 kgf/cm.sup.2 g (24.8 bar) with the gas volume fraction of 1.0, the refrigerant flow flowed into the second heat exchanger and was heat-exchanged with the water of 100 C., the heat-exchanged refrigerant flow in the state of 132 C., 24.3 kgf/cm.sup.2 g (24.8 bar) with the gas volume fraction of 0.0 flowed out, and flowed into the pressure drop device. Here, the coefficient of performance of the heat recovery apparatus and the temperature of the steam were shown in the following Table 1.

Comparative Example 1

(13) The steam was generated in the same manner as in Example 1 except that the refrigerant flow in the state of 79.6 C., 7.0 kgf/cm.sup.2 g (7.9 bar) with the gas volume fraction of 0.0 flowed into the first heat exchanger, and at the same time, the waste heat flow in the state of 90 C., 1.0 kgf/cm.sup.2 g with the gas volume fraction of 0.0 flowed into the first heat exchanger at a flow rate of 300,000 kg/hr for the heat exchange, the heat was exchanged in the first heat exchanger, the refrigerant flow in the state of 85 C., 7.0 kgf/cm.sup.2 g (7.9 bar) with the gas volume fraction of 1.0 flowed into the compressor, the refrigerant flow compressed in the compressor flowed out of the compressor while being in the state of 108 C., 14.2 kgf/cm.sup.2 g (15.0 bar) with the gas volume fraction of 1.0, the refrigerant flow flowed into the second heat exchanger and was heat-exchanged with water of 80 C., the heat-exchanged refrigerant flow in the state of 107 C., 14.2 kgf/cm.sup.2 g (15.0 bar) with the gas volume fraction of 0.0 flowed out, and flowed into the pressure drop device. Here, the coefficient of performance of the heat recovery apparatus and the temperature of the steam were shown in the following Table 2.

Comparative Example 2

(14) The steam was generated in the same manner as in Example 1 except that the refrigerant flow in the state of 61.9 C., 4.0 kgf/cm.sup.2 g (4.9 bar) with the gas volume fraction of 0.0 flowed into the first heat exchanger, and at the same time, the waste heat flow in the state of 70 C., 1.0 kgf/cm.sup.2 g with the gas volume fraction of 0.0 flowed into the first heat exchanger at a flow rate of 300,000 kg/hr for the heat exchange, the heat was exchanged in the first heat exchanger, the refrigerant flow in the state of 65 C., 4.0 kgf/cm.sup.2 g (4.9 bar) with the gas volume fraction of 1.0 flowed into the compressor, the refrigerant flow compressed in the compressor flowed out of the compressor while being in the state of 134 C., 24.6 kgf/cm.sup.2 g (25.2 bar) with the gas volume fraction of 1.0, the refrigerant flow flowed into the second heat exchanger and was heat-exchanged with the water of 100 C., the heat-exchanged refrigerant flow in the state of 133 C., 24.6 kgf/cm.sup.2 g (25.2 bar) with the gas volume fraction of 0.0 flowed out, and flowed into the pressure drop device. Here, the coefficient of performance of the heat recovery apparatus and the temperature of the steam were shown in the following Table 2.

(15) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 T.sub.F ( C.) T.sub.R ( C.) 85 75.4 95 75.4 95 68.5 T.sub.F T.sub.R ( C.) 9.6 19.6 16.5 P.sub.C (bar) P.sub.H (bar) 22 7.1 24.8 7.1 24.8 5.9 P.sub.C/P.sub.H 3.1 3.5 4.2 Q (W) 702,874 678,737 625,323 Total W (W) 220,404 255,159 256,294 COP 3.19 2.67 2.44 Steam temperature ( C.) 120 120 120

(16) TABLE-US-00002 TABLE 2 Comparative Comparative Example 1 Example 2 T.sub.F ( C.) T.sub.R ( C.) 90 79.6 70 61.9 T.sub.F T.sub.R ( C.) 10.4 8.1 P.sub.C (bar) P.sub.H (bar) 15.0 7.9 25.2 4.9 P.sub.C/P.sub.H 1.9 5.14 Q (W) 38,589 510,992 Total W (W) 126,919 236,665 COP 0.30 2.16 Steam temperature ( C.) 103 120