Heat storage heat exchanger applied to intermittent high-temperature flue gas waste heat and regulation and control method

Abstract

The invention discloses a heat storage heat exchanger applied to intermittent high-temperature flue gas waste heat and a regulation and control method, and the heat storage heat exchanger comprises a cold fluid inlet, a heat exchange pipe, a heat storage body, fins, a cold fluid outlet, a flue gas inlet, a flue gas outlet, a heat storage body cold end temperature measuring point and a heat storage body hot end temperature measuring point, the flue gas outlet is formed in the bottom of the heat storage heat exchanger, the heat exchange pipe penetrates through the middle of the heat storage heat exchanger, one end of the heat exchange pipe is a cold fluid inlet, the other end of the heat exchange pipe is a cold fluid outlet, the fins are welded to the heat exchange pipe, the space between the fins and the heat exchange pipe is filled with the heat storage body, and the heat storage body wraps the periphery of the heat exchange pipe. The cold end temperature measuring point of the heat accumulator is arranged at the cold fluid inlet, the hot end temperature measuring point of the heat accumulator is arranged at the cold fluid outlet, a gap is reserved between the fin and the heat accumulator, the expansion joint is filled with heat conduction oil, and the heat accumulator is a solid heat accumulation layer; the solid heat storage material is arranged, so that the heat exchanger has a heat storage function and is applied to intermittent flue gas waste heat recovery.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat storage heat exchangers, and in particular relates to a heat storage heat exchanger applied to intermittent high-temperature flue gas waste heat and a control method. Background Art

[0002] Most of the existing heat exchangers do not have the ability to store heat. When used for intermittent flue gas waste heat recovery, they need to be equipped with heat accumulators or molten salt heat storage tanks to generate relatively stable heat carriers for downstream processes. Take the converter as an example. The converter is an important part of the steel process and will generate a large amount of waste heat during the production process. The high-temperature flue gas generated by the converter is intermittent and discontinuous. Currently, it is used by waste heat boilers, steam heat accumulators and saturated generator sets. Chinese invention patent 201610266132.8 discloses a heat storage type waste heat power generation system and method based on intermittent high-temperature flue gas. The system includes a smelting furnace, a main flue gas pipeline, a first flow control valve, a second flow control valve, a third flow control valve, a level I heat storage device, a first flue gas bypass, a second flue gas bypass, a level II heat storage device, a fourth flow control, a fifth flow control valve, a sixth flow control valve, a chimney, an induced draft fan, an electrostatic precipitator, a generator, a steam turbine, a feed water pump, and a waste heat boiler. The above scheme utilizes the heat transfer capacity of graphite and effectively solves the problem of waste heat recovery of flue gas at the outlet of the smelting furnace by switching the bypass during the heat exchange process, thus achieving the purpose of stabilizing the inlet flue gas temperature of the waste heat boiler. However, the heat storage capacity of this scheme is limited, resulting in low efficiency of the heat exchanger.

[0003] Therefore, the present invention provides a heat storage heat exchanger and a control method for intermittent high-temperature flue gas waste heat to solve the technical problems existing in the above-mentioned background technology. Summary of the invention

[0004] In response to the problems raised by the above background technology, the present invention provides a heat storage heat exchanger and a control method for intermittent high-temperature flue gas waste heat. Solid heat storage materials are provided to enable the heat exchanger to have a heat storage function, which can be applied to intermittent flue gas waste heat recovery.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A heat storage heat exchanger used for intermittent high-temperature flue gas waste heat, comprising a cold fluid inlet, a heat exchange tube, a heat storage body, a fin, a cold fluid outlet, a flue gas inlet, a flue gas outlet, a heat storage body cold end temperature measuring point and a heat storage body hot end temperature measuring point, the flue gas inlet is arranged at the top of the heat storage heat exchanger, the flue gas outlet is arranged at the bottom of the heat storage heat exchanger, the heat exchange tube is arranged through the middle of the heat storage heat exchanger, one end of the heat exchange tube is the cold fluid inlet, and the other end is the cold fluid outlet, the fin is welded on the heat exchange tube, the heat storage body is filled between the fin and the heat exchange tube, the heat storage body is coated and arranged around the heat exchange tube, the heat storage body cold end temperature measuring point is arranged at the cold fluid inlet, the heat storage body hot end temperature measuring point is arranged at the cold fluid outlet, a gap is left between the fin and the heat storage body, the gap is an expansion joint, the expansion joint is filled with heat transfer oil, and the heat storage body is a solid heat storage layer.

[0007] It is further defined that it also includes a cold fluid inlet regulating valve group, which is arranged at the rear end of the cold fluid inlet. With such a structural design, the cold fluid inlet regulating valve group is used to adjust the inlet amount of saturated steam according to working conditions.

[0008] It is further defined that the fin is an annular fin, the cross section of which is T-shaped, and the straight-shaped portion of the T-shape faces outward.

[0009] It is further defined that the heat exchange tubes can be arranged in one group or multiple groups.

[0010] It is further defined that when the temperature measured at the temperature measuring point at the cold end of the heat storage body and the temperature measuring point at the hot end of the heat storage body reaches at least 350° C., the cold fluid inlet regulating valve group is opened.

[0011] A control method for a heat storage heat exchanger applied to intermittent high-temperature flue gas waste heat comprises the following steps:

[0012] Step 1: Start the heat storage heat exchanger, and the flue gas enters from the flue gas inlet. At this time, the cold fluid inlet regulating valve group is in the closed state;

[0013] Step 2: The heat storage body is continuously heated. After one or more cycles, when the temperature measuring points at the cold end of the heat storage body and the temperature measuring points at the hot end of the heat storage body reach at least 350°C, the cold fluid inlet regulating valve group is opened;

[0014] Step 3: Saturated steam enters the heat exchange tube and is then heated by the heat storage body and fins to become superheated steam;

[0015] Step 4: When the flue gas temperature or flow rate at the flue gas inlet decreases, and the temperature of the temperature measuring point at the hot end of the heat storage body decreases, the load reduction adjustment rate of the cold fluid inlet regulating valve group is controlled within 5% / min, specifically, the inlet amount of saturated steam is reduced at a rate of 5% / min, and the cold fluid outlet is maintained to meet the steam inlet requirements of the steam turbine;

[0016] Step 5: When the flue gas temperature or flow rate at the flue gas inlet increases, causing the temperature measuring point at the hot end of the heat storage body to increase, the load regulation rate of the cold fluid inlet regulating valve group is controlled within 10% / min, specifically, the intake of saturated steam is increased at a rate of 10% / min, and the cold fluid outlet is maintained to meet the steam inlet requirements of the turbine.

[0017] It is further defined that the heat storage heat exchanger has a minute-level heat storage function, specifically 0-7min and 23-30min, a total of 14 minutes, the heat storage body releases heat; from 7-23min the heat storage body absorbs heat.

[0018] It is further defined that the flue gas inlet temperature of the heat storage heat exchanger is 100°C in the first 5 minutes; it rises to 400°C in 5-7 minutes and then continues for 16 minutes; it drops to 100°C in 23-25 ​​minutes and continues until the end of the cycle; the cold fluid in the heat exchange tube is saturated steam of 1.0 MPa.

[0019] Beneficial effects of the present invention:

[0020] 1. This solution provides a heat storage heat exchanger and a control method for intermittent high-temperature flue gas waste heat. By setting a solid heat storage layer in the heat exchanger, the heat storage heat exchanger has a minute-level heat storage function.

[0021] 2. This scheme reduces the amount of thermal storage body used by setting up the thermal storage body cold end temperature measuring point, the thermal storage body hot end temperature measuring point and the cold fluid inlet regulating valve group, and utilizing the load regulation capability of the back-end equipment. When the cold fluid flow rate remains unchanged during the thermal storage body charging and discharging process, the heat released by the thermal storage body during the heat release process is large, and the amount of thermal storage body used is large; by using the regulating means, the cold fluid flow rate during the heat release process is reduced, thereby reducing the heat release and reducing the amount of thermal storage body used. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention can be further illustrated by the non-limiting examples given in the accompanying drawings;

[0023] Figure 1 A cross-sectional view of an embodiment of a heat storage heat exchanger and a control method for intermittent high-temperature flue gas waste heat according to the present invention;

[0024] The main component symbols are explained as follows: cold fluid inlet 1, cold fluid inlet regulating valve group 2, heat exchange tube 3, heat storage body 4, fin 5, cold fluid outlet 6, flue gas inlet 7, flue gas outlet 8, heat storage body cold end temperature measuring point 9, heat storage body hot end temperature measuring point 10. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0027] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] like Figure 1 As shown, a heat storage heat exchanger for intermittent high-temperature flue gas waste heat of the present invention comprises a cold fluid inlet 1, a heat exchange tube 3, a heat storage body 4, a fin 5, a cold fluid outlet 6, a flue gas inlet 7, a flue gas outlet 8, a heat storage body cold end temperature measuring point 9 and a heat storage body hot end temperature measuring point 10, wherein the flue gas inlet 7 is arranged at the top of the heat storage heat exchanger, the flue gas outlet 8 is arranged at the bottom of the heat storage heat exchanger, the heat exchange tube 3 is arranged through the middle of the heat storage heat exchanger, and one end of the heat exchange tube 3 is a cold fluid inlet 1 , the other end is a cold fluid outlet 6, the fin 5 is welded on the heat exchange tube 3, the space between the fin 5 and the heat exchange tube 3 is filled with a heat storage body 4, the heat storage body 4 is wrapped around the heat exchange tube 3, the cold end temperature measuring point 9 of the heat storage body is set at the cold fluid inlet 1, and the hot end temperature measuring point 10 of the heat storage body is set at the cold fluid outlet 6. A gap is left between the fin 5 and the heat storage body 4, and the gap is an expansion joint. The expansion joint is filled with heat transfer oil, and the heat storage body 4 is a solid heat storage layer.

[0029] Preferably, it further comprises a cold fluid inlet regulating valve group 2, which is arranged at the rear end of the cold fluid inlet 1. With such a structural design, the cold fluid inlet regulating valve group 2 is used to adjust the inlet amount of saturated steam according to working conditions.

[0030] Preferably, the fin 5 is an annular fin, and its cross section is T-shaped, with the straight-line portion of the T-shape facing outward.

[0031] Preferably, the heat exchange tubes 3 can be arranged in one group or multiple groups.

[0032] Preferably, when the temperature measured at the heat storage body cold end temperature measuring point 9 and the heat storage body hot end temperature measuring point 10 reaches at least 350° C., the cold fluid inlet regulating valve group 2 is opened.

[0033] A control method for a heat storage heat exchanger applied to intermittent high-temperature flue gas waste heat comprises the following steps:

[0034] Step 1: Start the heat storage heat exchanger, and the flue gas enters from the flue gas inlet 7. At this time, the cold fluid inlet regulating valve group 2 is in the closed state;

[0035] Step 2: The heat storage body 4 is continuously heated. After one or more cycles, when the temperature of the heat storage body cold end measuring point 9 and the temperature of the heat storage body hot end measuring point 10 reach at least 350° C., the cold fluid inlet regulating valve group 2 is opened;

[0036] Step 3: Saturated steam enters the heat exchange tube 3 and is then heated by the heat storage body 4 and the fins 5 to become superheated steam;

[0037] Step 4: When the flue gas temperature or flow rate at the flue gas inlet 7 decreases, and causes the temperature of the heat storage body hot end temperature measuring point 10 to decrease, the load reduction adjustment rate of the cold fluid inlet regulating valve group 2 is controlled within 5% / min, specifically, the inlet amount of saturated steam is reduced at a rate of 5% / min, and the cold fluid outlet 6 is maintained to meet the steam inlet requirements of the steam turbine;

[0038] Step 5: When the flue gas temperature or flow rate at the flue gas inlet 7 increases, causing the temperature measuring point 10 of the hot end of the heat storage body to increase, the load regulation rate of the cold fluid inlet regulating valve group 2 is controlled within 10% / min, specifically, the intake of saturated steam is increased at a rate of 10% / min, and the cold fluid outlet 6 is maintained to meet the steam inlet requirements of the turbine.

[0039] Preferably, the heat storage heat exchanger has a minute-level heat storage function, specifically, from 0 to 7 minutes and from 23 to 30 minutes, a total of 14 minutes, during which the heat storage body 4 releases heat; from 7 to 23 minutes, the heat storage body 4 absorbs heat.

[0040] Preferably, the flue gas inlet temperature of the heat storage heat exchanger is 100°C in the first 5 minutes; it rises to 400°C at 5-7 minutes and then continues for 16 minutes; it drops to 100°C at 23-25 ​​minutes and continues until the end of the cycle; the cold fluid in the heat exchange tube 3 is saturated steam at 1.0 MPa.

[0041] The working principle of this embodiment is:

[0042] The converter flue gas of this device is intermittently generated, and the inlet flue gas flow rate changes periodically. In the first 5 minutes of each cycle, the flue gas volume is approximately equal to 0, and in the 5-7 minutes, the flue gas volume rises to 72000Nm 3 / h and maintain for about 16 minutes, the flue gas volume drops to 0 in 23-25 ​​minutes and continues until the end of the cycle, and each cycle is about 30 minutes. The flue gas inlet temperature of the heat storage heat exchanger of the present invention is 100°C in the first 5 minutes; it rises to 400°C in 5-7 minutes, and then continues for 16 minutes; it drops to 100°C in 23-25 ​​minutes and continues until the end of the cycle; the cold fluid in the heat exchange tube 3 is 1.0MPa saturated steam, and its temperature is 179.9°C, which needs to be heated to 239.9°C, and the steam flow rate can vary from 30% to 100%, and the load increase adjustment rate is controlled at 10% / min, and the load reduction adjustment rate is controlled at 5% / min.

[0043] It should be noted that the flue gas temperature varies between 100 and 400°C, and the fluid in the tube needs to be heated to 239.9°C. When the flue gas temperature is lower than 240°C, the heat storage body 4 heats the fins 5 and the fluid in the heat exchange tube 3. If the heat storage body 4 is not provided, when the flue gas temperature is lower than 240°C, the steam temperature cannot reach 240°C, and the inlet steam at this time is 179.9°C, and the steam heats the flue gas.

[0044] When the device is started, flue gas enters from the flue gas inlet 7, the cold fluid inlet regulating valve group 2 is in a closed state, and the heat storage body 4 is heated. After one or more cycles, when the temperature measuring point 9 at the cold end of the heat storage body and the temperature measuring point 10 at the hot end of the heat storage body reach 350°C, the cold fluid inlet regulating valve group 2 opens, and saturated steam enters the heat exchange tube 3, and is then heated by the heat storage body 4 and the fins 5 to become superheated steam. When the flue gas temperature at the flue gas inlet 7 decreases or the flow rate decreases, causing the temperature of the temperature measuring point 10 at the hot end of the heat storage body to decrease, the load reduction regulation rate of the cold fluid inlet regulating valve group 2 is controlled within 5% / min (reducing the amount of saturated steam entering at a rate of 5% / min), and the cold fluid outlet 6 is maintained to meet the steam inlet requirements of the turbine; thereafter, when the flue gas temperature at the flue gas inlet 7 increases or the flow rate increases, causing the temperature measuring point 10 at the hot end of the heat storage body to increase, the load increase regulation rate of the cold fluid inlet regulating valve group 2 is controlled within 10% / min (increasing the amount of saturated steam entering at a rate of 10% / min), and the cold fluid outlet 6 is maintained to meet the steam inlet requirements of the turbine.

[0045] In summary, this solution provides a solid heat storage layer in the heat exchanger, so that the heat storage heat exchanger has a minute-level heat storage function. In addition, by providing a heat storage body cold end temperature measuring point 9, a heat storage body hot end temperature measuring point 10 and a cold fluid inlet regulating valve group 2, the load regulation capability of the back-end equipment is utilized to reduce the use of the heat storage body 4. When the cold fluid flow rate remains unchanged during the heat charging and discharging process of the heat storage body 4, the heat released during the heat release process of the heat storage body 4 is large, and the use of the heat storage body 4 is large; the cold fluid flow rate in the heat release process is reduced by regulating means, thereby reducing the heat release and reducing the use of the heat storage body 4.

[0046] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A heat storage heat exchanger used for intermittent high-temperature flue gas waste heat, characterized in that: The heat exchanger comprises a cold fluid inlet (1), a heat exchange tube (3), a heat storage body (4), a fin (5), a cold fluid outlet (6), a smoke inlet (7), a smoke outlet (8), a heat storage body cold end temperature measuring point (9) and a heat storage body hot end temperature measuring point (10), wherein the smoke inlet (7) is arranged at the top of the heat storage heat exchanger, the smoke outlet (8) is arranged at the bottom of the heat storage heat exchanger, the heat exchange tube (3) is arranged through the middle of the heat storage heat exchanger, one end of the heat exchange tube (3) is the cold fluid inlet (1), and the other end is the cold fluid outlet (6), The fin (5) is welded on the heat exchange tube (3), and a heat storage body (4) is used to fill the space between the fin (5) and the heat exchange tube (3). The heat storage body (4) is arranged around the heat exchange tube (3), and the cold end temperature measuring point (9) of the heat storage body is arranged at the cold fluid inlet (1), and the hot end temperature measuring point (10) of the heat storage body is arranged at the cold fluid outlet (6). A gap is left between the fin (5) and the heat storage body (4), and the gap is an expansion joint. The expansion joint is filled with heat transfer oil, and the heat storage body (4) is a solid heat storage layer.

2. The heat storage heat exchanger used for intermittent high-temperature flue gas waste heat according to claim 1, characterized in that: It also comprises a cold fluid inlet regulating valve group (2), wherein the cold fluid inlet regulating valve group (2) is arranged at the rear end of the cold fluid inlet (1).

3. The heat storage heat exchanger for intermittent high-temperature flue gas waste heat according to claim 1, characterized in that: The fin (5) is an annular fin, and its cross section is T-shaped, with the straight-line part of the T-shape facing outwards.

4. The heat storage heat exchanger for intermittent high-temperature flue gas waste heat according to claim 1 is characterized in that: The heat exchange tubes (3) may be arranged in one group or in multiple groups.

5. The heat storage heat exchanger for intermittent high-temperature flue gas waste heat according to claim 1, characterized in that: When the temperature measured at the heat storage body cold end temperature measuring point (9) and the heat storage body hot end temperature measuring point (10) reaches at least 350° C., the cold fluid inlet regulating valve group (2) opens.

6. A control method for a heat storage heat exchanger used for intermittent high-temperature flue gas waste heat, characterized in that: The steps include: Step 1: Start the heat storage heat exchanger, and the flue gas enters from the flue gas inlet (7), and the cold fluid inlet regulating valve group (2) is in a closed state; Step 2: The heat storage body (4) is continuously heated. After one or more cycles, when the temperature of the heat storage body cold end measuring point (9) and the temperature of the heat storage body hot end measuring point (10) reach at least 350° C., the cold fluid inlet regulating valve group (2) is opened; Step 3: Saturated steam enters the heat exchange tube (3), and is then heated by the heat storage body (4) and the fins (5) to become superheated steam; Step 4: When the flue gas temperature or flow rate at the flue gas inlet (7) decreases, and causes the temperature of the heat storage body hot end temperature measuring point (10) to decrease, the load reduction adjustment rate of the cold fluid inlet regulating valve group (2) is controlled within 5% / min, specifically, the inlet amount of saturated steam is reduced at a rate of 5% / min, and the cold fluid outlet (6) is maintained to meet the steam inlet requirements of the steam turbine; Step 5: When the flue gas temperature or flow rate at the flue gas inlet (7) increases, causing the temperature measuring point (10) at the hot end of the heat storage body to increase, the load regulation rate of the cold fluid inlet regulating valve group (2) is controlled within 10% / min, specifically, the inlet amount of saturated steam is increased at a rate of 10% / min, and the cold fluid outlet (6) is maintained to meet the steam inlet requirements of the turbine.

7. The control method of a heat storage heat exchanger applied to intermittent high-temperature flue gas waste heat according to claim 6 is characterized in that: The heat storage heat exchanger has a minute-level heat storage function, specifically, from 0 to 7 minutes and from 23 to 30 minutes, a total of 14 minutes, the heat storage body (4) releases heat; from 7 to 23 minutes, the heat storage body (4) absorbs heat.

8. The control method of a heat storage heat exchanger applied to intermittent high-temperature flue gas waste heat according to claim 6 is characterized in that: The flue gas inlet temperature of the heat storage heat exchanger is 100°C in the first 5 minutes; it rises to 400°C at 5-7 minutes and then continues for 16 minutes; it drops to 100°C at 23-25 ​​minutes and continues until the end of the cycle; the cold fluid in the heat exchange tube (3) is saturated steam at 1.0 MPa.

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