Flue gas waste heat utilization system

Abstract

The utility model relates to a flue gas waste heat utilization system which comprises a flue gas waste heat utilization mechanism and a user side process medium pipe, and the flue gas waste heat utilization mechanism is provided with a superheated water output pipe. A first heat exchanger and a second heat exchanger positioned at the downstream of the first heat exchanger are arranged on the user side process medium pipe; the superheated water output pipe is connected with a high-temperature fluid inlet of the first heat exchanger; a high-temperature fluid outlet of the first heat exchanger is connected with a superheated water return pipe; a high-temperature fluid inlet of the second heat exchanger is connected with a steam supply pipe, and a high-temperature fluid outlet of the second heat exchanger is connected with a condensate water return pipe. According to the flue gas waste heat utilization system, the first heat exchanger and the second heat exchanger are arranged on the user side process medium pipe, the user side process medium can be heated through superheated water and steam in sequence, the flue gas waste heat is fully utilized, meanwhile, the stability of the temperature of the user side process medium is guaranteed, and the utilization rate of the flue gas waste heat is improved. And the adverse effect of smoke waste heat fluctuation on user side production is avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of strip steel production, and specifically relates to a flue gas waste heat utilization system. Background Art

[0002] In the cold-rolled strip production line, many production processes have annealing process sections, among which the production process of annealing by fuel combustion will generate a large amount of flue gas waste heat; the waste heat of this part of flue gas still has a temperature of more than 400°C after passing through the combustion air waste heat exchanger, and still has great utilization value. Traditional extensive production processes often directly discharge this part of flue gas after mixing it with cold air, resulting in energy waste; as enterprises pay more attention to energy conservation and emission reduction, waste heat utilization technology for this part of flue gas has also emerged. At the same time, the production process sections of the unit such as strip drying, pickling, alkali washing, and cleaning require additional heating heat sources, which consume a lot of steam, electricity, etc.; therefore, using the above-mentioned flue gas waste heat for heating the production process sections such as strip drying, pickling, alkali washing, and cleaning is a waste heat utilization direction. However, the user side of the system requires a relatively stable process temperature, and the flue gas waste heat is affected by parameters such as furnace temperature, flue gas temperature, and equipment tolerance temperature, and there are large fluctuations, which will affect the process stability on the user side. Utility Model Content

[0003] The utility model relates to a flue gas waste heat utilization system, which can at least solve some defects of the prior art.

[0004] The utility model relates to a flue gas waste heat utilization system, comprising a flue gas waste heat utilization mechanism and a user-side process medium pipe, wherein the flue gas waste heat utilization mechanism has a superheated water output pipe; a first heat exchanger and a second heat exchanger are arranged on the user-side process medium pipe, and along the flow direction of the process medium, the first heat exchanger is located upstream of the second heat exchanger; the superheated water output pipe is connected to the high-temperature fluid inlet of the first heat exchanger, and the high-temperature fluid outlet of the first heat exchanger is connected to the superheated water return pipe; the high-temperature fluid inlet of the second heat exchanger is connected to a steam supply pipe, and the high-temperature fluid outlet of the second heat exchanger is connected to a condensed water return pipe.

[0005] As one of the embodiments, the flue gas waste heat utilization mechanism includes a flue gas duct connected to the flue gas outlet of the annealing furnace, the flue gas duct is sequentially connected to a third heat exchanger and a fourth heat exchanger, the low-temperature fluid inlet and the low-temperature fluid outlet of the third heat exchanger are respectively connected to a combustion air inlet pipe and a combustion air output pipe, the low-temperature fluid inlet of the fourth heat exchanger is connected to a low-temperature water inlet pipe, and the superheated water output pipe is connected to the low-temperature fluid outlet of the fourth heat exchanger.

[0006] As one of the implementation modes, the superheated water return pipe is butt-jointed with the low-temperature water inlet pipe or is connected in a bypass manner to the low-temperature water inlet pipe.

[0007] As one of the implementation modes, a first temperature detection unit is provided on the user-side process medium pipe, and the first temperature detection unit is located between the first heat exchanger and the second heat exchanger. A first valve control unit interlocked with the first temperature detection unit is provided on the superheated water output pipe.

[0008] As one of the implementation modes, a first bypass pipe is provided on the superheated water output pipe, two ends of the first bypass pipe are respectively connected to two sides of the first valve control unit, and a first bypass valve is provided on the first bypass pipe.

[0009] As one of the implementation modes, the first valve control unit includes a first regulating valve and two first manual shut-off valves arranged at both sides of the first regulating valve.

[0010] As one of the implementation modes, a second temperature detection unit is provided on the user-side process medium pipe, the second temperature detection unit is located downstream of the second heat exchanger, and a second valve control unit interlocked with the second temperature detection unit is provided on the steam supply pipe.

[0011] As one of the implementation modes, a second bypass pipe is provided on the steam supply pipe, two ends of the second bypass pipe are respectively connected to two sides of the second valve control unit, and a second bypass valve is provided on the second bypass pipe.

[0012] As one of the implementation modes, the second valve control unit includes a second regulating valve and two second manual shut-off valves arranged at the front and rear sides of the second regulating valve.

[0013] As one of the implementation modes, the first heat exchanger and / or the second heat exchanger is a plate heat exchanger, a shell and tube heat exchanger or a tube-fin heat exchanger.

[0014] The utility model has at least the following beneficial effects:

[0015] The flue gas waste heat utilization system provided by the utility model arranges the first heat exchanger and the second heat exchanger on the process medium pipe on the user side, and can heat the process medium on the user side by superheated water and steam in turn, while fully utilizing the flue gas waste heat, ensuring the stability of the temperature of the process medium on the user side, and avoiding the adverse effect of the flue gas waste heat fluctuation on the production on the user side. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of the arrangement structure of the user-side process medium pipe provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] like Figure 1 The embodiment of the utility model provides a flue gas waste heat utilization system, including a flue gas waste heat utilization mechanism and a user-side process medium pipe 1, wherein the flue gas waste heat utilization mechanism has a superheated water output pipe 22; a first heat exchanger 21 and a second heat exchanger 31 are arranged on the user-side process medium pipe 1, and along the flow direction of the process medium, the first heat exchanger 21 is located upstream of the second heat exchanger 31; the superheated water output pipe 22 is connected to the high-temperature fluid inlet of the first heat exchanger 21, and the high-temperature fluid outlet of the first heat exchanger 21 is connected to the superheated water return pipe 23; the high-temperature fluid inlet of the second heat exchanger 31 is connected to a second heat exchanger 32, and the high-temperature fluid outlet of the second heat exchanger 31 is connected to a condensed water return pipe 33.

[0020] Preferably, the above-mentioned flue gas waste heat utilization mechanism is for waste heat utilization of annealing furnace flue gas. In one embodiment, the flue gas waste heat utilization mechanism includes a flue gas duct connected to the flue gas outlet of the annealing furnace, the flue gas duct is connected in series with a third heat exchanger and a fourth heat exchanger in sequence, the low-temperature fluid inlet and the low-temperature fluid outlet of the third heat exchanger are respectively connected to the combustion air inlet pipe and the combustion air outlet pipe, the low-temperature fluid inlet of the fourth heat exchanger is connected to the low-temperature water inlet pipe, and the superheated water outlet pipe 22 is connected to the low-temperature fluid outlet of the fourth heat exchanger. In the third heat exchanger, the high-temperature flue gas exchanges heat with the combustion air, which can heat the combustion air to 500-600°C and reduce the temperature of the high-temperature flue gas to 400-500°C; the third heat exchanger can adopt an air-to-air heat exchanger. The flue gas after heat exchange with the combustion air enters the fourth heat exchanger, and this part of the flue gas exchanges heat with low-temperature water, heating the low-temperature water to form superheated water; wherein, the temperature of the low-temperature water supplied by the low-temperature water inlet pipe is preferably in the range of 80-95°C, and the temperature of the superheated water obtained is in the range of 120-140°C; the fourth heat exchanger can adopt a gas-liquid heat exchanger.

[0021] Furthermore, the superheated water return pipe 23 is connected to the low-temperature water inlet pipe or is connected to the low-temperature water inlet pipe in a bypass manner, so that the superheated water return can be returned to the fourth heat exchanger to be heated and circulated. In another embodiment, the superheated water after heat exchange can be used as cleaning water for the cleaning process section, and the superheated water return pipe 23 is connected to the cleaning water pipeline of the cleaning process section.

[0022] In one embodiment, if Figure 1 , the user-side process medium pipe 1 is provided with a first temperature detection unit 26, the first temperature detection unit 26 is located between the first heat exchanger 21 and the second heat exchanger 31, and the superheated water output pipe 22 is provided with a first valve control unit 24 interlocked with the first temperature detection unit 26. Based on this design, the superheated water flow rate is adjusted by detecting the process medium temperature at the outlet side of the first heat exchanger 21, which can ensure the accuracy and stability of the process medium temperature control and save the amount of superheated water. Among them, the first valve control unit 24 and the first temperature detection unit 26 can be electrically connected to the workshop console, and the interlocking control involved is a conventional automatic control means, and no additional programming is required.

[0023] Preferably, if Figure 1 The first valve control unit 24 includes a first regulating valve and two first manual shut-off valves arranged on the front and rear sides of the first regulating valve, wherein the first regulating valve is an automatic valve, which is interlocked with the first temperature detection unit 26 for control; setting the manual shut-off valve can ensure the safety of system operation.

[0024] Preferably, if Figure 1 The superheated water output pipe 22 is provided with a first bypass pipe 25, the two ends of the first bypass pipe 25 are respectively connected to the two sides of the first valve control unit 24, and a first bypass valve is provided on the first bypass pipe 25. By providing the first bypass pipe 25, the continuous operation of the system can be ensured when the first valve control unit 24 fails, thereby improving the operation reliability and safety of the above-mentioned flue gas waste heat utilization system.

[0025] In one embodiment, if Figure 1 , the user-side process medium pipe 1 is provided with a second temperature detection unit 36, the second temperature detection unit 36 ​​is located downstream of the second heat exchanger 31, and the second heat exchanger 32 is provided with a second valve control unit 34 interlocked with the second temperature detection unit 36. Based on this design, by detecting the process medium temperature at the outlet side of the second heat exchanger 31 to adjust the steam flow, the accuracy and stability of the process medium temperature control can be guaranteed, while saving steam consumption. Among them, the second valve control unit 34 and the second temperature detection unit 36 ​​can be electrically connected to the workshop console, and the interlocking control involved is a conventional automatic control method, and no additional programming is required.

[0026] Preferably, if Figure 1 The second valve control unit 34 includes a second regulating valve and two second manual shut-off valves arranged on the front and rear sides of the second regulating valve, wherein the second regulating valve is an automatic valve, which is interlocked with the second temperature detection unit 36 ​​for control; setting the manual shut-off valve can ensure the safety of system operation.

[0027] Preferably, if Figure 1 The second heat exchanger 32 is provided with a second bypass pipe 35, the two ends of which are respectively connected to the two sides of the second valve control unit 34, and a second bypass valve is provided on the second bypass pipe 35. By providing the second bypass pipe 35, the continuous operation of the system can be ensured when the second valve control unit 34 fails, thereby improving the operating reliability and safety of the above-mentioned flue gas waste heat utilization system.

[0028] The first temperature detection unit 26 / the second temperature detection unit 36 ​​mentioned above can adopt a thermal resistor or other temperature detection elements with remote transmission function, which are not listed here one by one.

[0029] The first heat exchanger 21 and / or the second heat exchanger 31 may be a plate heat exchanger, a shell and tube heat exchanger or a tube-fin heat exchanger, and may be selected according to parameters / characteristics such as temperature, pressure, corrosiveness, etc. of the process medium.

[0030] In this embodiment, the user side can be at least one of the production process sections such as the strip drying process section, the pickling process section, the alkali washing process section, and the cleaning process section, and the process medium on the user side corresponds to drying air, acid solution, alkali solution, cleaning water, etc.

[0031] In this system, preferably, the process medium temperature at the outlet side of the first heat exchanger 21 is set according to the maximum process medium temperature allowed by the user-side process; the process medium temperature at the outlet side of the second heat exchanger 31 is set according to the minimum process medium temperature of the user-side process.

[0032] Preferably, the steam temperature is in the range of 150-170°C. The steam source can be exogenous steam or self-produced steam of the flue gas waste heat utilization system. For example, the flue gas duct connected to the flue gas outlet of the annealing furnace is connected with the first flue gas branch pipe and the second flue gas branch pipe. The third heat exchanger and the fourth heat exchanger are arranged on the first flue gas branch pipe to prepare superheated water; a waste heat boiler is arranged on the second flue gas branch pipe to prepare steam. The prepared steam can be stored by a steam accumulator to ensure the stability of the steam flow required by the second heat exchanger 31; or, the flue gas duct is connected in series with the third heat exchanger, the fourth heat exchanger and the waste heat boiler in sequence, and the flue gas discharged from the fourth heat exchanger enters the waste heat boiler for further waste heat utilization to prepare steam. A flue gas combustion device can be further arranged between the fourth heat exchanger and the waste heat boiler. By burning the combustible gas in the flue gas, the flue gas temperature can be increased, thereby improving the waste heat utilization effect and steam quality.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A flue gas waste heat utilization system, comprising a flue gas waste heat utilization mechanism and a user-side process medium pipe, characterized in that: The flue gas waste heat utilization mechanism has a superheated water output pipe; the first heat exchanger and the second heat exchanger are arranged on the user-side process medium pipe, and along the flow direction of the process medium, the first heat exchanger is located upstream of the second heat exchanger; the superheated water output pipe is connected to the high-temperature fluid inlet of the first heat exchanger, and the high-temperature fluid outlet of the first heat exchanger is connected to the superheated water return pipe; the high-temperature fluid inlet of the second heat exchanger is connected to a steam supply pipe, and the high-temperature fluid outlet of the second heat exchanger is connected to the condensed water return pipe.

2. The flue gas waste heat utilization system according to claim 1, characterized in that: The flue gas waste heat utilization mechanism includes a flue gas duct connected to the flue gas outlet of the annealing furnace, the flue gas duct is connected in series with a third heat exchanger and a fourth heat exchanger in sequence, the low-temperature fluid inlet and the low-temperature fluid outlet of the third heat exchanger are respectively connected to a combustion air inlet pipe and a combustion air output pipe, the low-temperature fluid inlet of the fourth heat exchanger is connected to a low-temperature water inlet pipe, and the superheated water output pipe is connected to the low-temperature fluid outlet of the fourth heat exchanger.

3. The flue gas waste heat utilization system according to claim 2, characterized in that: The superheated water return pipe is butt-jointed with the low-temperature water inlet pipe or is connected in a side connection with the low-temperature water inlet pipe.

4. The flue gas waste heat utilization system according to claim 1, characterized in that: The user-side process medium pipe is provided with a first temperature detection unit, the first temperature detection unit is located between the first heat exchanger and the second heat exchanger, and the superheated water output pipe is provided with a first valve control unit interlocked with the first temperature detection unit.

5. The flue gas waste heat utilization system according to claim 4, characterized in that: The superheated water output pipe is provided with a first bypass pipe, two ends of the first bypass pipe are respectively connected to two sides of the first valve control unit, and a first bypass valve is provided on the first bypass pipe.

6. The flue gas waste heat utilization system according to claim 4, characterized in that: The first valve control unit includes a first regulating valve and two first manual cut-off valves arranged at both sides of the first regulating valve.

7. The flue gas waste heat utilization system according to claim 1, characterized in that: A second temperature detection unit is provided on the user-side process medium pipe, and the second temperature detection unit is located downstream of the second heat exchanger. A second valve control unit interlocked with the second temperature detection unit is provided on the steam supply pipe.

8. The flue gas waste heat utilization system according to claim 7, characterized in that: The steam supply pipe is provided with a second bypass pipe, both ends of the second bypass pipe are respectively connected to two sides of the second valve control unit, and a second bypass valve is provided on the second bypass pipe.

9. The flue gas waste heat utilization system according to claim 7, characterized in that: The second valve control unit includes a second regulating valve and two second manual cut-off valves arranged at both sides of the second regulating valve.

10. The flue gas waste heat utilization system according to claim 1, characterized in that: The first heat exchanger and / or the second heat exchanger is a plate heat exchanger, a shell and tube heat exchanger or a tube-fin heat exchanger.

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