Industrial furnace waste gas waste heat cascade recovery system

Abstract

The invention belongs to the technical field of waste heat recovery, and particularly discloses an industrial furnace waste gas waste heat cascade recovery system which comprises an industrial furnace, a fused salt energy storage module and a steam pocket module, a waste gas discharge port of the industrial furnace is communicated with a waste gas pipe, the waste gas pipe is communicated with a first waste gas branch pipe and a second waste gas branch pipe, and the first waste gas branch pipe is communicated with the fused salt energy storage module; the second waste gas branch pipe is communicated with the steam pocket module, a pressure detection meter is arranged on the waste gas pipe, the first waste gas branch pipe and the second waste gas branch pipe are provided with a first electric control valve and a second electric control valve, outlets of the fused salt energy storage module and the steam pocket module are communicated with discharge pipes, and ORC generator sets are sequentially communicated with the discharge pipes. The problems that in the prior art, medium and low temperature waste heat is not deeply utilized, heat is wasted, and the waste heat recovery rate is low are solved. An energy recovery path is automatically switched through the fused salt energy storage module and the steam pocket module according to waste gas pressure, and heat of low-temperature waste gas of 300 DEG C or below is recovered through the ORC generator set for power generation.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery, and in particular to a cascade recovery system for waste heat from industrial furnace exhaust. Background Art

[0002] Industrial furnaces (such as metallurgical furnaces and blast furnaces) generate large amounts of high-temperature exhaust gases during high-temperature operation, typically ranging from 800°C to 1400°C. These exhaust gases contain not only sensible heat but also carry some incompletely burned fuel or harmful gases (such as NOx). Currently, waste heat recovery from industrial furnace exhaust gases primarily relies on direct heat exchange technology. Common methods include converting the exhaust gas heat into steam through a heat exchanger for power generation or heating; using the exhaust gas to preheat combustion air to improve combustion efficiency; and discharging some low-temperature exhaust gases directly into the chimney due to their poor economical utilization.

[0003] Although the above technology can recover some high-temperature waste heat, the design of the single heat exchange equipment leads to low utilization rate of medium and low-temperature waste heat. The efficiency of traditional heat exchangers drops significantly when the exhaust gas temperature is below 300°C, resulting in a large amount of low-temperature waste heat not being utilized and being directly discharged, causing energy waste and low waste heat recovery rate. Summary of the Invention

[0004] The purpose of the present invention is to provide a cascade recovery system for waste heat from industrial furnace exhaust gas, so as to solve the problem in the prior art that medium and low temperature waste heat is not deeply utilized, resulting in heat waste and low waste heat recovery rate.

[0005] To achieve the above-mentioned objectives, the basic solution provided by the present invention is: a cascade recovery system for waste heat from exhaust gas from an industrial furnace, comprising an industrial furnace, a molten salt energy storage module, a steam drum module and a chimney, wherein the exhaust gas outlet of the industrial furnace is connected to an exhaust pipe, one end of the exhaust pipe is respectively connected to an exhaust gas branch pipe 1 and an exhaust gas branch pipe 2, one end of the exhaust gas branch pipe 1 is connected to the inlet of the molten salt energy storage module, and one end of the exhaust gas branch pipe 2 is connected to the inlet of the steam drum module, a pressure detection gauge is provided on the exhaust pipe, and an electric regulating valve 1 and an electric regulating valve 2 are respectively provided on the exhaust gas branch pipe 1 and the exhaust gas branch pipe 2, the pressure detection gauge is electrically connected to a PLC sensor, and the electric regulating valve 1 and the electric regulating valve 2 are respectively electrically connected to the PLC sensor, the exhaust gas outlets of the molten salt energy storage module and the steam drum module are both connected to an exhaust pipe, one end of the exhaust pipe is connected to the chimney, and the exhaust pipe is sequentially connected to an ORC generator set, a catalytic purification module and an exhaust fan.

[0006] The working principle of the present invention is that when it is necessary to recover the waste heat of the exhaust gas from the industrial furnace, the high-temperature exhaust gas generated by the industrial furnace is first sent to the exhaust pipe by the smoke exhaust fan, and the pressure detection gauge monitors the exhaust gas pressure after heat exchange in real time. When the pressure detection gauge detects that the exhaust gas pressure is greater than 4MPa, the PLC controller controls the electric regulating valve 2 to open, and the exhaust gas enters the steam drum module through the exhaust gas branch pipe 2, and the generated steam is supplied to the steam network; when the pressure detection gauge detects that the exhaust gas pressure is ≤4MPa, the PLC controller controls the electric regulating valve 1 to open, and the exhaust gas enters the molten salt energy storage module through the exhaust gas branch pipe 1, and the exhaust gas heat is stored in the binary molten salt. Then the exhaust gas enters the ORC generator set through the exhaust pipe to generate electricity, and then the exhaust gas enters the catalytic purification module through the exhaust pipe to filter harmful gases, and then the purified exhaust gas is discharged into the chimney and finally discharged.

[0007] The beneficial effects of the present invention are: ① Through the setting of the molten salt energy storage module and the steam drum module, the energy recovery path can be automatically switched according to the exhaust gas pressure, thereby realizing flexible utilization of high-temperature exhaust gas and solving the energy waste problem caused by the traditional single recovery method; ② The ORC generator set recovers the heat of low-temperature exhaust gas below 300°C to generate electricity, which solves the gap in direct discharge of low-temperature waste heat in traditional technology and improves the comprehensive waste heat recovery rate of the system; ③ The exhaust gas after energy recovery is processed by the catalytic purification module to realize the purification of NOx in the exhaust gas; ④ The pressure detection gauge and the PLC controller are linked for control to avoid manual adjustment, ensure automatic matching after detecting the exhaust gas pressure, and improve operating efficiency.

[0008] Option 2, which is the preferred option of the basic option, is that the exhaust pipe is connected to a silicon carbide ceramic heat exchanger, the air inlet of the silicon carbide ceramic heat exchanger is connected to an air pipe, one end of the air pipe is connected to an induced draft fan, and an air supply pipe is connected between the air outlet of the silicon carbide ceramic heat exchanger and the air inlet end of the industrial furnace; by arranging the silicon carbide ceramic heat exchanger, the air pipe, the air supply pipe and the induced draft fan, efficient heat exchange between high-temperature exhaust gas and normal temperature air is achieved, the air is preheated and reused to support combustion, thereby reducing the gas consumption of the industrial furnace.

[0009] Option three is a preferred option of the basic option. The end of the exhaust pipe close to the inlet of the ORC generator set is connected to a bypass exhaust pipe, and one end of the bypass exhaust pipe is connected to the end of the exhaust pipe close to the inlet of the catalytic purification module. The end of the exhaust pipe close to the inlet of the ORC generator set and the bypass exhaust pipe are respectively provided with an electric regulating valve three and an electric regulating valve four. The end of the exhaust pipe close to the inlet of the catalytic purification module is provided with a temperature sensor, and the temperature sensor is electrically connected to a PLC controller. The electric regulating valve three and the electric regulating valve four are electrically connected to the PLC controller. By arranging the bypass exhaust pipe, the temperature sensor, the electric regulating valve three, the electric regulating valve four and the PLC sensor, the exhaust gas temperature before the catalytic purification module can be stabilized in the optimal range, thereby ensuring the activity of the catalyst.

[0010] Option 4 is a preferred option of Option 3. The outer wall of the catalytic purification module is covered with a shell. One side of the shell is connected to an air intake pipe, and the other side is connected to an exhaust pipe. One end of the exhaust pipe is connected to an end of the exhaust pipe close to the inlet of the ORC generator set. The air intake pipe and the exhaust pipe are respectively provided with an electric regulating valve five and a one-way valve. The electric regulating valve five is electrically connected to the PLC controller. By setting up the shell and the introduced air intake pipe, the catalytic bed can be heated in an emergency, which can further improve the activity of the catalyst.

[0011] Option 5 is a preferred option of Option 2. The exhaust pipe is connected to a spiral coil at one end close to the outlet of the catalytic purification module. A cavity is provided on the spiral coil. One side of the cavity is connected to an air inlet and the other side is connected to an air branch pipe. The air branch pipe is connected to the air pipe. The waste heat of the exhaust gas is recovered to preheat the combustion air and improve the thermal efficiency of the silicon carbide heat exchanger.

[0012] Option six is ​​the preferred option of the basic option. The catalytic purification module adopts a two-stage honeycomb ceramic carrier with pore densities of 50ppi and 30ppi respectively. It absorbs harmful gas components such as NOx in the flue gas in a segmented manner to improve the removal effect.

[0013] Option seven, which is the preferred option of the basic option, the catalyst loaded on the catalytic purification module is a CeO2-MnO2-ZrO2 ternary catalyst; the synergistic effect of the ternary catalyst improves the NOx removal effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a structural diagram of a cascade recovery system for waste heat from industrial furnace exhaust gas. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below through specific embodiments: The figure marks in the drawings of the specification include: 1. industrial furnace; 2. molten salt energy storage module; 3. steam drum module; 4. ORC generator set; 5. chimney; 6. exhaust pipe; 7. exhaust branch pipe 1; 8. exhaust branch pipe 2; 9. pressure detection gauge; 10. electric control valve 1; 11. electric control valve 2; 12. exhaust pipe; 13. catalytic purification module; 14. exhaust fan; 15. silicon carbide ceramic heat exchanger; 16. air pipe; 17. induced draft fan; 18. air supply pipe; 19. bypass exhaust pipe; 20. electric control valve 3; 21. electric control valve 4; 22. temperature sensor; 23. shell; 24. air inlet pipe; 25. exhaust pipe; 26. electric control valve 5; 27. one-way valve; 28. spiral coil; 29. ​​cavity; 30. air inlet; 31. air branch.

[0016] like Figure 1As shown: A cascade recovery system for waste heat from exhaust gas of an industrial furnace, comprising an industrial furnace 1, a molten salt energy storage module 2, a drum module 3 and a chimney 5. The exhaust outlet of the industrial furnace 1 is connected to an exhaust pipe 6, and the exhaust pipe 6 is connected to a silicon carbide ceramic heat exchanger 15. The air inlet of the silicon carbide ceramic heat exchanger 15 is connected to an air pipe 16, and one end of the air pipe 16 is connected to an induced draft fan 17. An air supply pipe 18 is connected between the air outlet of the silicon carbide ceramic heat exchanger 15 and the air inlet end of the industrial furnace 1. One end of the exhaust pipe 6 is respectively connected to an exhaust branch pipe 1 7 and an exhaust branch pipe 2 8. One end of the exhaust branch pipe 1 7 is connected to the inlet of the molten salt energy storage module 2, and one end of the exhaust branch pipe 2 8 is connected to the inlet of the drum module 3. A pressure detection gauge 9 is provided on the exhaust pipe 6, and an electric regulating valve 10 and an electric regulating valve 2 11 are respectively provided on the exhaust branch pipe 1 7 and the exhaust branch pipe 2 8. The pressure detection gauge 9 is electrically connected to the exhaust branch pipe 1 A PLC sensor is connected, and the electric regulating valve 10 and the electric regulating valve 2 11 are electrically connected to the PLC sensor respectively. The exhaust gas outlets of the molten salt energy storage module 2 and the steam drum module 3 are both connected to an exhaust pipe 12, one end of the exhaust pipe 12 is connected to the chimney 5, and the exhaust pipe 12 is connected to the ORC generator set 4, the catalytic purification module 13 and the exhaust fan 14 in sequence. The catalytic purification module 13 adopts a two-stage honeycomb ceramic carrier with a pore density of 50ppi and 30ppi respectively. The catalyst loaded on the catalytic purification module 13 is a CeO2-MnO2-ZrO2 three-way catalyst. The end of the exhaust pipe 12 close to the outlet of the catalytic purification module 13 is connected to a spiral coil 28, and a cavity 29 is sleeved on the spiral coil 28. One side of the cavity 29 is connected to an air inlet 30, and the other side is connected to an air branch pipe 31, and the air branch pipe 31 is connected to the air pipe 16; One end of the exhaust pipe 12 near the inlet of the ORC generator set 4 is connected to a bypass exhaust pipe 19, and one end of the bypass exhaust pipe 19 is connected to one end of the exhaust pipe 12 near the inlet of the catalytic purification module 13. An electric regulating valve three 20 and an electric regulating valve four 21 are respectively provided on the end of the exhaust pipe 12 near the inlet of the ORC generator set 4 and the bypass exhaust pipe 19. A temperature sensor 22 is provided at the end of the exhaust pipe 12 near the inlet of the catalytic purification module 13. The temperature sensor 22 is electrically connected to a PLC controller. The electric regulating valve three 20 and the electric regulating valve four 21 are electrically connected to the PLC controller. The outer wall of the catalytic purification module 13 is sheathed with a shell 23. One side of the shell 23 is connected to an intake pipe 24, and the other side is connected to an exhaust pipe 25. One end of the exhaust pipe 25 is connected to one end of the exhaust pipe 12 near the inlet of the ORC generator set 4. An electric regulating valve five 26 and a one-way valve 27 are respectively provided on the intake pipe 24 and the exhaust pipe 25. The electric regulating valve five 26 is electrically connected to the PLC controller.

[0017] Table 1 - Comparison of the effects of the present invention and traditional waste heat recovery devices index Traditional waste heat recovery device The present invention Gas consumption <![CDATA[85m 3 / t]]> <![CDATA[69m 3 / t]]> NOx emissions <![CDATA[80mg / m 3 ]]> <![CDATA[35mg / m 3 ]]> Annual power generation - 1.2GWh The implementation method of this embodiment is as follows: when it is necessary to recover the waste heat of the exhaust gas of the industrial furnace 1, first, the high-temperature exhaust gas (800-1400°C) generated by the industrial furnace 1 is introduced into the silicon carbide ceramic heat exchanger 15 by the exhaust fan 14 through the exhaust pipe 6. At the same time, the induced draft fan 17 introduces air into the silicon carbide ceramic heat exchanger 15 through the air pipe 16. The air and the high-temperature exhaust gas exchange heat. The air after heat exchange is sent to the air supply end of the industrial furnace 1 through the air supply pipe 18, and the exhaust gas after heat exchange is discharged from the outlet end. The exhaust gas temperature after heat exchange in the silicon carbide ceramic heat exchanger 15 is 900-1000°C. Then the pressure detection meter 9 monitors the exhaust gas pressure after heat exchange in real time. When the pressure detection meter 9 detects When the exhaust gas pressure is greater than 4MPa, the PLC controller controls the electric regulating valve 11 to open, and the exhaust gas enters the drum module 3 through the exhaust gas branch pipe 8, generating 0.5-4MPa steam to be supplied to the steam network; when the pressure detection gauge 9 detects that the exhaust gas pressure is ≤4MPa, the PLC controller controls the electric regulating valve 10 to open, and the exhaust gas enters the molten salt energy storage module 2 through the exhaust gas branch pipe 7, storing the exhaust gas heat in the binary molten salt. The exhaust gas temperature after passing through the molten salt energy storage module 2 and the drum module 3 is 300-500℃; then the exhaust gas enters the ORC generator set 4 through the exhaust pipe 12 for power generation, and the exhaust gas temperature after passing through the ORC generator set 4 is 200-300℃. The exhaust gas then enters the catalytic purification module 13 through the exhaust pipe 12 to filter harmful gases. At the same time, the temperature sensor 22 monitors the exhaust gas temperature entering the catalytic purification module 13 in real time. When the temperature monitored by the temperature sensor 22 is less than 200°C, the PLC controller will control the electric regulating valve 4 21 to start, and at the same time control the opening of the electric regulating valve 3 20, so that the exhaust gas at 300-500°C before entering the ORC generator set is mixed with the original exhaust gas and enters the catalytic purification module 13. When the temperature monitored by the temperature sensor 22 is continuously less than 100°C, the PLC controller will control the electric regulating valve 5 26 to start, and the exhaust gas at 900-1000°C in the exhaust pipe enters the shell through 24. To increase the temperature of the catalytic bed, when the temperature monitored by the temperature sensor is ≥350°C, the PLC controller will control the electric regulating valve four 21 and the electric regulating valve five 26 to close, and at the same time restore the opening of the electric regulating valve three 20, thereby dynamically adjusting the temperature of the exhaust gas entering the catalytic purification module 13 and improving the activity of the catalyst. The temperature of the exhaust gas after passing through the catalytic purification module 13 is about 100°C; then the purified exhaust gas enters the spiral coil 28 and exchanges heat with the air entering from the air inlet 30. The air after heat exchange enters the air pipe 16 through the air branch pipe 31, and the preheated part enters the air in the silicon carbide ceramic heat exchanger 15. The exhaust gas after heat exchange is discharged into the chimney 5 and finally discharged.

[0018] The above is only an embodiment of the present invention, and the common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A cascade recovery system for waste heat from industrial furnace exhaust, characterized in that: The invention comprises an industrial furnace (1), a molten salt energy storage module (2), a drum module (3) and a chimney (5), wherein the exhaust gas outlet of the industrial furnace (1) is connected to an exhaust gas pipe (6), one end of the exhaust gas pipe (6) is respectively connected to an exhaust gas branch pipe 1 (7) and an exhaust gas branch pipe 2 (8), one end of the exhaust gas branch pipe 1 (7) is connected to the inlet of the molten salt energy storage module (2), one end of the exhaust gas branch pipe 2 (8) is connected to the inlet of the drum module (3), a pressure detection gauge (9) is provided on the exhaust gas pipe (6), and the exhaust gas branch pipes 1 (7) and 2 (8) are respectively connected to the exhaust gas branch pipe 1 (7) and 2 (8). An electric regulating valve 1 (10) and an electric regulating valve 2 (11) are respectively provided, the pressure detection gauge (9) is electrically connected to a PLC sensor, the electric regulating valve 1 (10) and the electric regulating valve 2 (11) are electrically connected to the PLC sensor, the exhaust gas outlets of the molten salt energy storage module (2) and the steam drum module (3) are both connected to an exhaust pipe (12), one end of the exhaust pipe (12) is connected to the chimney (5), and the exhaust pipe (12) is sequentially connected to the ORC generator set (4), the catalytic purification module (13) and the exhaust fan (14).

2. The industrial furnace exhaust gas waste heat cascade recovery system according to claim 1, characterized in that: The exhaust pipe (6) is connected to a silicon carbide ceramic heat exchanger (15), the air inlet of the silicon carbide ceramic heat exchanger (15) is connected to an air pipe (16), one end of the air pipe (16) is connected to an induced draft fan (17), and an air supply pipe (18) is connected between the air outlet of the silicon carbide ceramic heat exchanger (15) and the air inlet end of the industrial furnace (1).

3. The industrial furnace exhaust gas waste heat cascade recovery system according to claim 1, characterized in that: One end of the discharge pipe (12) close to the inlet of the ORC generator set (4) is connected to a bypass discharge pipe (19), one end of the bypass discharge pipe (19) is connected to one end of the discharge pipe (12) close to the inlet of the catalytic purification module (13), one end of the discharge pipe (12) close to the inlet of the ORC generator set (4) and the bypass discharge pipe (19) are respectively provided with an electric regulating valve three (20) and an electric regulating valve four (21), one end of the discharge pipe (12) close to the inlet of the catalytic purification module (13) is provided with a temperature sensor (22), the temperature sensor (22) is electrically connected to a PLC controller, and the electric regulating valve three (20) and the electric regulating valve four (21) are electrically connected to the PLC controller.

4. The industrial furnace exhaust gas waste heat cascade recovery system according to claim 3, characterized in that: The outer wall of the catalytic purification module (13) is covered with a shell (23), one side of the shell (23) is connected to an air intake pipe (24), and the other side is connected to an exhaust pipe (25), one end of the exhaust pipe (25) is connected to an end of the discharge pipe (12) close to the inlet of the ORC generator set (4), and the air intake pipe (24) and the exhaust pipe (25) are respectively provided with an electric regulating valve five (26) and a one-way valve (27), and the electric regulating valve five (26) is electrically connected to a PLC controller.

5. The industrial furnace exhaust gas waste heat cascade recovery system according to claim 2, characterized in that: One end of the exhaust pipe (12) close to the outlet of the catalytic purification module (13) is connected to a spiral coil (28), a cavity (29) is sleeved on the spiral coil (28), one side of the cavity (29) is connected to an air inlet (30), and the other side is connected to an air branch pipe (31), and the air branch pipe (31) is connected to the air pipe (16).

6. The industrial furnace exhaust gas waste heat cascade recovery system according to claim 1, characterized in that: The catalytic purification module (13) adopts a double-section honeycomb ceramic carrier with pore densities of 50 ppi and 30 ppi respectively.

7. The industrial furnace exhaust waste heat cascade recovery system according to claim 1, characterized in that: The catalyst loaded on the catalytic purification module (13) is a CeO2-MnO2-ZrO2 ternary catalyst.

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