Flue gas waste heat recovery system

Abstract

The utility model discloses a flue gas waste heat recovery system. The flue gas waste heat recovery system comprises a burner, a waste gas pipeline, a first heat exchanger, a second heat exchanger, a smoke exhaust fan and a flue gas exhaust pipeline, a waste gas outlet of the burner communicates with an inlet of the waste gas pipeline, an outlet of the waste gas pipeline communicates with a heat source channel inlet of the first heat exchanger, and a heat source channel outlet of the first heat exchanger communicates with a heat source channel inlet of the second heat exchanger through a pipeline. A heat source channel outlet of the second heat exchanger communicates with an inlet of a smoke exhaust fan through a pipeline, and an outlet of the smoke exhaust fan communicates with a smoke exhaust pipeline. And a cold source channel of the first heat exchanger is communicated with a protective gas pipeline. The flue gas waste heat recycling device has the advantages that the first heat exchanger and the second heat exchanger are designed, flue gas waste heat is recycled in a grading mode, the recycled waste heat can be directly supplied to users with different requirements, secondary distribution is not needed, energy consumption is saved to the maximum extent, and energy conservation and environment protection are achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a waste heat recovery technology, specifically relates to a flue gas waste heat recovery system of vertical galvanization annealing furnace of ultra -low emission. BACKGROUND

[0002] According to the requirement of domestic relevant policy, domestic partial steel enterprises, especially the steel enterprises in Hebei area, have gradually begun to implement the ultra -low emission standard of atmospheric pollutants of steel industry. In response to the relevant appeal of the country, pure reliance on the optimization of the burner cannot be realized, and increasing the necessary flue gas treatment equipment and carrying out waste heat recovery will be the only means for the enterprise to complete the task.

[0003] The vertical galvanization annealing furnace is used for annealing treatment to the strip steel, and flue gas is generated in the annealing process, and in the prior art, the flue gas is usually directly led out and then subjected to waste heat recovery, the temperature range of the flue gas is large, the recovered waste heat needs to be subjected to secondary distribution, and the content of nitrogen oxides in the flue gas does not meet the ultra -low emission requirement advocated by the country. SUMMARY

[0004] The utility model discloses a waste heat recovery system for flue gas, which aims to provide recovered waste heat for multiple users with different needs.

[0005] The utility model discloses a technical scheme that a waste heat recovery system for flue gas comprises a burner, a waste gas pipeline, a first heat exchanger, a second heat exchanger, an exhaust fan and a flue gas discharge pipeline.

[0006] The waste gas outlet of the burner is communicated with the inlet of the waste gas pipeline, the outlet of the waste gas pipeline is communicated with the heat source channel inlet of the first heat exchanger, the heat source channel outlet of the first heat exchanger is communicated with the heat source channel inlet of the second heat exchanger through a pipeline, the heat source channel outlet of the second heat exchanger is communicated with the inlet of the exhaust fan through a pipeline, and the outlet of the exhaust fan is communicated with the flue gas discharge pipeline.

[0007] The cold source channel of the first heat exchanger is communicated with the protective gas pipeline, and the protective gas pipeline is communicated with the preheating section air bellow.

[0008] According to the above scheme, the waste heat recovery system for flue gas is further provided with a denitration device, the inlet of the denitration device is communicated with the heat source channel outlet of the second heat exchanger, and the outlet of the denitration device is communicated with the inlet of the exhaust fan.

[0009] According to the above scheme, the waste heat recovery system for flue gas is further provided with a third heat exchanger, the third heat exchanger is arranged between the denitration device and the exhaust fan, the heat source channel inlet of the third heat exchanger is communicated with the outlet of the denitration device through a pipeline, and the heat source channel outlet of the third heat exchanger is communicated with the inlet of the exhaust fan through a pipeline.

[0010] According to the scheme, the flue gas waste heat recovery system is provided with a first waste gas collecting pipe; the waste gas pipeline has a plurality of waste gas pipelines, the inlet of each waste gas pipeline is communicated with the waste gas outlet of the burner, the outlet of each waste gas pipeline is communicated with the inlet of the first waste gas collecting pipe, and the outlet of the first waste gas collecting pipe is communicated with the heat source channel inlet of the first heat exchanger.

[0011] According to the scheme, the flue gas waste heat recovery system is further provided with a bypass pipeline, and the bypass pipeline is communicated with the heat source channel outlet downstream pipeline and the heat source channel inlet upstream pipeline of the second heat exchanger.

[0012] According to the scheme, the flue gas waste heat recovery system is further provided with a second waste gas collecting pipe; the first heat exchanger and the second heat exchanger are correspondingly provided with two groups respectively, the heat source channel outlets of the two groups of second heat exchangers are communicated with the inlets of the second waste gas collecting pipe through pipelines respectively; and the outlet of the second waste gas collecting pipe is communicated with the inlet of the denitration device.

[0013] According to the scheme, the second waste gas collecting pipe is further communicated with a cold air mixing pipeline.

[0014] According to the scheme, the flue gas waste heat recovery system is further provided with a third waste gas collecting pipe and a fourth waste gas collecting pipe, the inlet of the third waste gas collecting pipe is communicated with the outlet of the denitration device, and the outlet of the fourth waste gas collecting pipe is communicated with the exhaust fan;

[0015] The third waste gas collecting pipe and the fourth waste gas collecting pipe are communicated through a first branch and a second branch;

[0016] The first branch is communicated with the heat source channel of the third heat exchanger.

[0017] According to the scheme, an adjusting valve is arranged on the first branch; and an adjusting valve is arranged on the second branch.

[0018] According to the scheme, the burner is provided with an inner sleeve and an outer sleeve, the inlet of the inner sleeve is communicated with the air pipeline, and the outlet of the outer sleeve is communicated with the waste gas pipeline.

[0019] The beneficial effects of the utility model are as follows:

[0020] 1. The first heat exchanger and the second heat exchanger are arranged in the utility model, flue gas waste heat is recovered and utilized in stages, the recovered waste heat can be directly supplied to users with different demands, secondary distribution is not needed, energy consumption is saved to the maximum, and energy saving and environmental protection are achieved.

[0021] 2. The denitration device is arranged in the utility model, flue gas after two-stage heat exchange is subjected to denitration treatment, the content of nitrogen oxides in the flue gas is reduced, the content of nitrogen oxides in the flue gas meets the national ultra-low emission standard, the denitration device is arranged after the two-stage heat exchanger, flue gas after two-stage heat exchange meets the temperature requirement before entering the denitration device, and the flue gas denitration efficiency is improved.

[0022] 3、The third heat exchanger is designed, and flue gas on the waste gas pipeline is introduced into the burner to preheat the air, and the two designs further improve the flue gas waste heat utilization rate.

[0023] 4、The utility model discloses a flue gas is used to preheat the air of entering the burner, improves the temperature of air, improves the flue gas recovery efficiency.

[0024] 5、The utility model discloses a bypass pipeline, when the second heat exchanger fails, also does not need to carry out shutdown, guarantees normal production. ACCURATE DRAWING

[0025] Figure 1 It is the structure schematic diagram of one specific embodiment of the utility model.

[0026] Among them: 1 - burner, 2 - waste gas pipeline, 3 - first waste gas collecting pipe, 4 - first heat exchanger, 5 - preheating section wind box, 6 - second heat exchanger, 7 - second waste gas collecting pipe, 8 - denitration device, 9 - third waste gas collecting pipe, 10 - third heat exchanger, 11 - second branch, 12 - fourth waste gas collecting pipe, 13 - exhaust fan, 14 - bypass pipeline, 15 - cold air mixing pipeline, 16 - regulating valve, 17 - first branch, 18 - protective gas pipeline, 19 - flue gas discharge pipeline. CONCRETE IMPLEMENTING METHOD

[0027] In order to better understand the utility model, the utility model is further described below in combination with the drawings and specific embodiments.

[0028] As Figure 1 Shown in a kind of flue gas waste heat recovery system, specifically a vertical galvanizing annealing furnace flue gas waste heat recovery system, including burner 1, waste gas pipeline 2, first heat exchanger 4, second heat exchanger 6, exhaust fan 13 and flue gas discharge pipeline 19;

[0029] The waste gas outlet of the burner 1 is communicated with the inlet of the waste gas pipeline 2, the outlet of the waste gas pipeline 2 is communicated with the heat source passage inlet of the first heat exchanger 4, the heat source passage outlet of the first heat exchanger 4 is communicated with the heat source passage inlet of the second heat exchanger 6 through pipeline, the heat source passage outlet of the second heat exchanger 6 is communicated with the inlet of the exhaust fan 13 through pipeline, and the outlet of the exhaust fan 13 is communicated with the flue gas discharge pipeline 19.

[0030] The cold source passage of the first heat exchanger 4 is communicated with the protective gas pipeline, and the protective gas pipeline 18 is communicated with the preheating section wind box 5.

[0031] The cold source passage of the second heat exchanger 6 is communicated with the cold source pipeline A, and the outlet of the cold source pipeline A is communicated with the user pipeline to provide hot water for the user.

[0032] The utility model discloses a vertical galvanization annealing furnace's burner 1 is double stroke's W type radiant tube burner, and the burner 1 inside pipeline is the form of bushing, that is, the burner 1 sets up inner bushing and outer bushing, and the inlet of inner bushing communicates with air pipeline, and the outlet of outer bushing communicates with waste gas pipeline 2, and air enters the burner 1 from inner bushing, and the flue gas generated by the burner 1 enters waste gas pipeline 2 through the outer bushing of the burner 1, and the flue gas of outer bushing and the air of inner bushing flow reversely, and form counter current heat exchange, and simultaneously, the burner 1 is provided with finned tube inside, improves the heat exchange efficiency of air and flue gas, and the burner 1 is the existing structure, and each waste gas pipeline 2 communicates with corresponding burner 1 respectively, Figure 1 Only one burner 1 is shown in the figure.

[0033] The utility model discloses a vertical galvanization annealing furnace's burner 1 is double stroke's W type radiant tube burner, and the burner 1 inside pipeline is the form of bushing, that is, the burner 1 sets up inner bushing and outer bushing, and the inlet of inner bushing communicates with air pipeline, and the outlet of outer bushing communicates with waste gas pipeline 2, and air enters the burner 1 from inner bushing, and the flue gas generated by the burner 1 enters waste gas pipeline 2 through the outer bushing of the burner 1, and the flue gas of outer bushing and the air of inner bushing flow reversely, and form counter current heat exchange, and simultaneously, the burner 1 is provided with finned tube inside, improves the heat exchange efficiency of air and flue gas, and the burner 1 is the existing structure, and each waste gas pipeline 2 communicates with corresponding burner 1 respectively,

[0034] Preferably, the flue gas waste heat recovery system is further provided with a denitration device 8, the inlet of the denitration device 8 communicates with the heat source passage outlet of the second heat exchanger 6, and the outlet of the denitration device 8 communicates with the inlet of the exhaust fan 13.

[0035] In the utility model, the denitration device 8 is designed, and nitrogen oxides in the flue gas can be removed to meet the emission standard.

[0036] Preferably, the flue gas waste heat recovery system is further provided with a third heat exchanger 10, the third heat exchanger 10 is arranged between the denitration device and the exhaust fan 13, the heat source passage inlet of the third heat exchanger 10 communicates with the outlet of the denitration device 8 through a pipeline, the heat source passage outlet of the third heat exchanger 10 communicates with the inlet of the exhaust fan 13 through a pipeline, and the cold source passage of the third heat exchanger 10 communicates with a cold source pipeline B.

[0037] In the utility model, the third heat exchanger 10 is designed in the flue gas waste heat recovery system, the flue gas after denitration is used to heat the water in the cold source pipeline B to generate superheated water, the superheated water is sent to a user for use, and the fourth stage waste heat utilization of the flue gas is realized.

[0038] Preferably, the flue gas waste heat recovery system is provided with a first waste gas collecting pipe 3; the waste gas pipeline 2 has a plurality of waste gas pipelines 2, the inlet of each waste gas pipeline 2 is communicated with the waste gas outlet of the burner 1, the outlet of each waste gas pipeline 2 is communicated with the inlet of the first waste gas collecting pipe 3, and the outlet of the first waste gas collecting pipe 3 is communicated with the heat source passage inlet of the first heat exchanger 4.

[0039] Preferably, the flue gas waste heat recovery system is further provided with a bypass pipeline 14, and the bypass pipeline 14 is communicated with a pipeline downstream of the heat source passage outlet of the second heat exchanger 6 and a pipeline upstream of the heat source passage inlet.

[0040] In the utility model, the design of the bypass pipeline 14, when the second heat exchanger 6 fails, the unit does not need to stop, the flue gas flowing out from the first heat exchanger 4 does not pass through the second heat exchanger 6, and directly flows to the subsequent process through the bypass pipeline 14.

[0041] Preferably, the flue gas waste heat recovery system is further provided with a second waste gas collecting pipe 7; the first heat exchanger 4 and the second heat exchanger 6 are correspondingly provided with two groups respectively, the heat source passage outlets of the two groups of second heat exchangers 6 are communicated with the inlet of the second waste gas collecting pipe 7 through pipelines respectively; and the outlet of the second waste gas collecting pipe 7 is communicated with the inlet of the denitration device 8.

[0042] Preferably, the second waste gas collecting pipe 7 is further communicated with a cold air mixing pipeline 15 to mix cold air in the second waste gas collecting pipe 7.

[0043] In the utility model, after the flue gas completes the third stage waste heat recovery, enters the second waste gas collecting pipe 7, according to the requirement of the denitration device 8 to the flue gas temperature, the amount of mixed cold air is adjusted, so that the flue gas is best matched with the denitration temperature.

[0044] Preferably, the flue gas waste heat recovery system is further provided with a third waste gas collecting pipe 9 and a fourth waste gas collecting pipe 12, the inlet of the third waste gas collecting pipe 9 is communicated with the outlet of the denitration device 8, and the outlet of the fourth waste gas collecting pipe 12 is communicated with the exhaust fan 13.

[0045] The third waste gas collecting pipe 9 and the fourth waste gas collecting pipe 12 are communicated through a first branch 17 and a second branch 11;

[0046] The first branch 17 is communicated with the heat source passage of the third heat exchanger 10, and an adjusting valve 16 is arranged on the first branch 17;

[0047] An adjusting valve 16 is arranged on the second branch 11.

[0048] In the utility model, the design of the second branch 11, when the third heat exchanger 10 fails, the unit does not need to stop, the flue gas flowing out from the third waste gas collecting pipe 9 directly enters the fourth waste gas collecting pipe 12 through the second branch 11.

[0049] In this invention, the flue gas from the third waste gas collection pipe 9 is divided into two paths. Most of the flue gas passes through the third heat exchanger 10 on the first branch 17 to complete the fourth stage of waste heat recovery. The design of the second branch 11 allows for adjustment of the flue gas volume on the first branch 17 and the second branch 11 according to different loads of the annealing furnace. Furthermore, it allows the flue gas flowing from the third waste gas collection pipe 9 to directly enter the fourth waste gas collection pipe 12 via the second branch 11 without shutting down the machine in case of a malfunction in the third heat exchanger 10. A detection pipeline is connected to the second branch 11, and a regulating valve 16 is installed on the detection pipeline. This allows for adjustment of the flue gas volume as needed and monitoring of the flue gas temperature on the detection pipeline, strictly controlling the flue gas temperature to ensure it reaches the temperature required for discharge into the chimney.

[0050] The heat exchangers and denitrification devices involved in this utility model are all mature equipment in the industry, and their structures and functions are existing, so they will not be described in detail here.

[0051] Example 1

[0052] like Figure 1 The illustrated flue gas waste heat recovery system includes a burner 1, multiple waste gas pipelines 2, two first heat exchangers 4, two second heat exchangers 6, two exhaust fans 13, a flue gas discharge pipeline 19, two first waste gas collection pipes 3, second waste gas collection pipes 7, third waste gas collection pipes 9, and a fourth waste gas collection pipe 12. The burner 1 is a double-stroke W-type radiant tube burner. The exhaust gas outlet of the burner 1 is connected to each exhaust gas pipeline 2. There are eleven exhaust gas pipelines 2 in total, of which six exhaust gas pipelines 2 form one group and the other five exhaust gas pipelines 2 form another group. The vertical galvanizing annealing furnace is equipped with burners 1, and the exhaust gas outlet of the burner 1 is connected to the corresponding exhaust gas pipeline 2 according to its arrangement position. The outlet of the exhaust gas pipeline 2 in the same group is connected to one of the first exhaust gas collection pipes 3. The first exhaust gas collection pipe 3, the heat source channel of a first heat exchanger 4, and the heat source channel of a second heat exchanger 6 are connected in sequence. The five exhaust gas pipelines 2, the first exhaust gas collection pipe 3, the heat source channel of the first heat exchanger 4, and the heat source channel of the second heat exchanger 6 in the other group are connected in sequence. The cold source channel of the first heat exchanger 4 is connected to the protective gas pipeline 18. The cold source channel of the second heat exchanger 6 is connected to the cold source pipeline A. The inlet and outlet of the heat source channel of the second heat exchanger 6 are also provided with bypass pipelines 14 connecting the two. The heat source channel outlets of the first heat exchanger 4 and the second heat exchanger 6 are both connected to the second waste gas collection pipe 7. The outlet of the second waste gas collection pipe 7 is sequentially connected to the denitrification device 8 and the third waste gas collection pipe 9. The third waste gas collection pipe 9 is connected to the fourth waste gas collection pipe 12 through the first branch 17 and the second branch 11. The first branch 17 is connected to the heat source channel of the third heat exchanger 10. Regulating valves 16 are respectively installed on the first branch 17 and the second branch 11. The outlet of the fourth waste gas collection pipe 12 is connected to the inlet of the exhaust fan 13, and the outlet of the exhaust fan 13 is connected to the flue gas emission pipe 19.

[0053] Example 2

[0054] Example 2 is the same as Example 1 in other aspects, except for the following configuration: two sets of exhaust fans 13 are provided, one for standby and one for use; the outlet of the fourth exhaust gas collection pipe 12 is connected to the inlet of the two exhaust fans 13 respectively, and the outlet of the two exhaust fans 13 is connected to the flue gas emission pipe 19 respectively.

[0055] This embodiment is used in a vertical galvanizing annealing furnace to treat the flue gas generated during strip annealing. The specific working principle is as follows:

[0056] 1. The flue gas generated by the combustion of burner 1 exchanges heat with the air in the opposite direction inside burner 1 to preheat the air; after exchanging heat with the air, the temperature of the flue gas drops to about 650℃ and flows out from burner 1, and proceeds to the next process through exhaust gas pipeline 2.

[0057] 2. The exhaust gas pipeline 2 is divided into two groups, which respectively introduce the flue gas generated by the burner 1 into the corresponding first exhaust gas collection pipe 3, and then into the first heat exchanger 4 through the first exhaust gas collection pipe 3 to preheat the protective gas from the preheating section air box 5. The preheated protective gas flows back into the preheating section air box 5 and is sprayed onto the surface of the strip steel to preheat the steel, realizing the second stage of waste heat utilization of the flue gas. The temperature of the flue gas flowing out of the first heat exchanger 4 drops to about 570-580℃.

[0058] 3. The denitrification device 8 uses a medium-temperature catalyst, with a matching flue gas temperature of 230℃~380℃. To match the operating temperature of the denitrification catalyst, a second heat exchanger 6 is installed before the denitrification device 8. The flue gas flowing out of the first heat exchanger 4 enters the second heat exchanger 6 to heat the water in the cold source pipeline A, generating superheated water for supply to other users, thus realizing the third-stage waste heat utilization of the flue gas. To further ensure that the flue gas temperature entering the denitrification device 8 is reduced to below 380℃, a cold air mixing pipeline 15 can be installed in the second waste gas collection pipe 7, which controls the flue gas temperature entering the denitrification device 8 and protects the denitrification device 8.

[0059] 4. The flue gas flowing out from the second heat exchanger 6 enters the denitrification device 8 to remove nitrogen oxides from the flue gas, reducing the nitrogen oxide content in the flue gas to below the emission standard.

[0060] 5. The flue gas treated by the denitrification device 8 is still at a higher temperature than the emission temperature, so it enters the third heat exchanger 10 to heat the hot water in the cold source pipeline B. The generated superheated water is supplied to the user. After heat exchange, the temperature of the flue gas drops to below 200℃, which meets the emission temperature requirements. It then enters the chimney and is discharged through the exhaust fan 13 and the flue gas emission pipeline 19.

[0061] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0062] Finally, it should be noted that the above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A flue gas heat recovery system, characterized by, The system comprises a burner, a waste gas pipeline, a first heat exchanger, a second heat exchanger, an exhaust fan and a flue gas discharge pipeline. The waste gas outlet of the burner is communicated with the inlet of the waste gas pipeline, the outlet of the waste gas pipeline is communicated with the heat source passage inlet of the first heat exchanger, the heat source passage outlet of the first heat exchanger is communicated with the heat source passage inlet of the second heat exchanger through a pipeline, the heat source passage outlet of the second heat exchanger is communicated with the inlet of the exhaust fan through a pipeline, and the outlet of the exhaust fan is communicated with the flue gas discharge pipeline. The cold source passage of the first heat exchanger is communicated with the protective gas pipeline, and the protective gas pipeline is communicated with the preheating section air tank.

2. The flue gas heat recovery system of claim 1, wherein, The flue gas waste heat recovery system is further provided with a denitration device, the inlet of the denitration device is communicated with the heat source passage outlet of the second heat exchanger, and the outlet of the denitration device is communicated with the inlet of the exhaust fan.

3. The flue gas heat recovery system of claim 2, wherein, The flue gas waste heat recovery system is further provided with a third heat exchanger, the third heat exchanger is arranged between the denitration device and the exhaust fan, the heat source passage inlet of the third heat exchanger is communicated with the outlet of the denitration device through a pipeline, and the heat source passage outlet of the third heat exchanger is communicated with the inlet of the exhaust fan through a pipeline.

4. The flue gas heat recovery system of claim 3, wherein, The flue gas waste heat recovery system is provided with a first waste gas collecting pipe, the waste gas pipeline has a plurality of waste gas pipelines, the inlet of each waste gas pipeline is communicated with the waste gas outlet of the burner, the outlet of each waste gas pipeline is communicated with the inlet of the first waste gas collecting pipe, and the outlet of the first waste gas collecting pipe is communicated with the heat source passage inlet of the first heat exchanger.

5. The flue gas heat recovery system of claim 4, wherein, The flue gas waste heat recovery system is further provided with a bypass pipeline, the bypass pipeline is communicated with the downstream pipeline of the heat source passage outlet of the second heat exchanger and the upstream pipeline of the heat source passage inlet.

6. A flue gas heat recovery system as claimed in claim 4 or 5, characterised in that, The flue gas waste heat recovery system is further provided with a second waste gas collecting pipe, the first heat exchanger and the second heat exchanger are correspondingly provided with two groups respectively, the heat source passage outlets of the two groups of second heat exchangers are respectively communicated with the inlet of the second waste gas collecting pipe through pipelines, and the outlet of the second waste gas collecting pipe is communicated with the inlet of the denitration device.

7. The flue gas heat recovery system of claim 6, wherein, The second waste gas collecting pipe is further communicated with a cold air mixing pipeline.

8. The flue gas heat recovery system of claim 6, wherein, The flue gas waste heat recovery system is further provided with a third waste gas collecting pipe and a fourth waste gas collecting pipe, the inlet of the third waste gas collecting pipe is communicated with the outlet of the denitration device, and the outlet of the fourth waste gas collecting pipe is communicated with the exhaust fan. The third waste gas collecting pipe and the fourth waste gas collecting pipe are communicated through a first branch and a second branch. The first branch is communicated with the heat source passage of the third heat exchanger.

9. The flue gas heat recovery system of claim 8, wherein, Adjusting valves are arranged on the first branch and the second branch.

10. The flue gas heat recovery system of claim 8, wherein, The burner is provided with an inner sleeve and an outer sleeve, the inlet of the inner sleeve is communicated with the air pipeline, and the outlet of the outer sleeve is communicated with the waste gas pipeline.

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