Pre-oxidation furnace hot air heating method and system coupled with heat recovery

Abstract

The invention belongs to the technical field of carbon fiber pre-oxidation furnace heating, and particularly relates to the technical field of combustion methods of waste or low-grade fuel, in particular to a pre-oxidation furnace hot air heating method and system coupled with heat recovery. According to the method, fresh air to enter the pre-oxidation furnace is divided into two parts, one path of fresh air is mixed with return air of circulating air in the previous technological process of the pre-oxidation furnace after being subjected to gradient heating for multiple times, third gradient heating is carried out, fourth gradient heating is carried out through a heat conduction oil heater, and secondary gradient heating is carried out; and then another path of fresh air which is heated for one time and not mixed is introduced, the fresh air is mixed with the mixed air heated to the temperature higher than the process temperature again, and after the process temperature is reached, the mixed air is fed into the pre-oxidation furnace. And by controlling the flow of the newly introduced fresh air, the effect of accurately controlling the temperature of the mixed air at the process temperature is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon fiber preoxidation furnace heating, specifically to the technical field of a waste or low-grade fuel combustion method, and more particularly to a preoxidation furnace hot air heating method and system coupled with heat recovery. Background Art

[0002] At present, domestic pre-oxidation furnaces mainly adopt electric heating and direct natural gas heating, which have certain shortcomings: the energy consumption of the electric heating system is extremely high, the electricity consumption of the pre-oxidation furnace group accounts for too high a proportion of the production cost, and the power grid is prone to insufficient power supply during peak power consumption; although direct natural gas heating can reduce power consumption, the combustion heater is placed in the air duct inside the furnace, and the risks of local high temperature of the heater and flue gas leakage are prominent. The temperature of the pre-oxidation hot air fluctuates greatly. When the temperature fluctuates too much, it is easy to affect the oxidation quality of the carbon fiber and even cause uncontrolled oxidation of the fiber to catch fire.

[0003] On the other hand, although the exhaust air from the pre-oxidation furnace is hot, it contains tar, making heat recovery difficult. Directly using fresh air and exhaust air for heat recovery can easily cause the tar components to undergo phase change and condense on the inner walls of the air supply duct, resulting in coking and blockage. Without heat recovery, the exhaust duct network is difficult to insulate and generates high indoor heat dissipation, impacting the workshop environment and wasting energy. Currently, there is a lack of a safe, stable, and energy-efficient method and system for heating the hot air from pre-oxidation furnaces.

[0004] Patent CN103352273A describes a temperature-adjustable pre-oxidation furnace burner device. This device utilizes a conical inner shell, a built-in U-tube thermal oil system, and a temperature-sensitive layer for coordinated temperature control. This, combined with a nano-insulation coating and an outer shell insulation layer, reduces heat loss. While this patent addresses the issue of low temperatures at both ends of the furnace, the design relies on an external power source to heat the thermal oil, resulting in high energy consumption in long-term operation.

[0005] Patent CN115707801B describes a polyacrylonitrile fiber drying and densification process. This process utilizes a circulating heat transfer oil system to perform multi-stage drying and densification of the raw fibers, while strictly controlling the surface temperature uniformity of the heated rollers. This patent improves the drawability of the polyacrylonitrile precursor during pre-oxidation while effectively reducing lint and breakage rates. This patent utilizes heat transfer oil for drying and densification, and does not involve waste heat recovery.

[0006] Therefore, it is urgent to provide a hot air heating method and system for a pre-oxidation furnace coupled with heat recovery to solve the technical problems in the above-mentioned related technologies, that is, the carbon fiber pre-oxidation furnace has high requirements for hot air temperature fluctuation, high heating energy saving, and high heating stability and safety.

[0007] It should be noted that the above information disclosed in this Background section is only for understanding the background technology of the present application concept, and therefore, it may contain information that does not constitute prior art. Summary of the Invention

[0008] The embodiments of the present disclosure at least provide a method and system for heating hot air from a pre-oxygen furnace coupled with heat recovery.

[0009] In a first aspect, embodiments of the present disclosure provide a method for heating hot air from a pre-oxidation furnace coupled with heat recovery, wherein the fresh air to be fed into the pre-oxidation furnace is divided into two paths. One path of fresh air is subjected to multiple gradient heating steps and then mixed with the other path of fresh air. After reaching the process temperature, the mixed air is fed into the pre-oxidation furnace. The method specifically includes the following steps: Step S1: connect the first waste heat recovery device, the second waste heat recovery device, the thermal oil heater, and the pre-oxidation furnace in sequence, connect the air supply pipe to the air inlet of the pre-oxidation furnace, and connect the air outlet of the pre-oxidation furnace to the second waste heat recovery device and the thermal oil heater; Step S2: fresh air is passed to the first waste heat recovery device, and the fresh air exchanges heat with the first waste heat recovery device, and the temperature of the fresh air rises from the ambient temperature T0 to T1; Step S3: The fresh air passes through the first waste heat recovery device and is split into two routes: the main pipe and the supply air pipe. The fresh air in the main pipe enters the second waste heat recovery device for heat exchange, and the fresh air temperature rises from T1 to T2. Step S4: the fresh air passes through the second waste heat recovery device, and the circulating air in the pre-oxidation furnace is mixed with the fresh air passing through the second waste heat recovery device, thereby raising the temperature of the mixed air from T2 to T3; Step S5: The mixed air enters the thermal oil heater to exchange heat with the oil, and the mixed air temperature rises from T3 to T4; In step S6, the mixed air is mixed with the fresh air in the air supply duct, the temperature is reduced from T4 to T5, and the mixed air enters the pre-oxidation furnace.

[0010] In an optional embodiment, the target temperature of the exhaust port of the thermal oil heater is set to T4, and the actual temperature of the exhaust port of the thermal oil heater is T a4 ; If T a4 <T4, then increase the power of the thermal oil heater and raise the temperature T a4 To T4; If T a4 > T4, then reduce the power of the thermal oil heater and lower the temperature T a4 To T4.

[0011] In an optional embodiment, the target temperature of the air inlet of the pre-oxidation furnace is set to T5, and the actual temperature is reduced to T5 after the mixed air of the thermal oil heater is mixed with the fresh air in the air supply pipe. a5 ; If Ta5 <T5, then increase the circulating air flow and reduce the proportion of fresh air in the air supply duct to increase T a5 To T5; If T a5 > T5, reduce the circulating air flow and increase the proportion of fresh air in the air supply duct to reduce T a5 To T5.

[0012] In an optional embodiment, the target oxygen concentration in the pre-oxidation furnace is set to C1, and the actual oxygen concentration in the pre-oxidation furnace is C0; If C0 < C1, increase the fresh air volume Q1 to increase the oxygen concentration in the pre-oxidation furnace, and at the same time increase the exhaust air volume Q2 of the pre-oxidation furnace. The exhaust air volume Q2 is 1 to 1.2 times of Q1 to maintain the pressure in the furnace at a negative pressure, until the oxygen concentration in the furnace C0 = C1; If C0>C1, reduce the exhaust air volume of the pre-oxidation furnace and reduce the fresh air volume at the same time to reduce the oxygen concentration in the pre-oxidation furnace until C0=C1.

[0013] In a second aspect, an embodiment of the present disclosure further provides a pre-oxygen furnace hot air heating system coupled with heat recovery, which is applied to perform the pre-oxygen furnace hot air heating method coupled with heat recovery as described above, and the pre-oxygen furnace hot air heating system coupled with heat recovery comprises: A main pipeline, and a first waste heat exchanger, a second waste heat exchanger, a thermal oil heater and a pre-oxidation furnace connected in sequence through the main pipeline; The exhaust port of the pre-oxidation furnace is connected between the second waste heat exchanger and the thermal oil heater; There is also an air supply duct between the thermal oil heater and the pre-oxidation furnace, and the other end of the air supply duct is connected between the first waste heat exchanger and the second waste heat exchanger.

[0014] In an optional embodiment, the exhaust port of the pre-oxidation furnace is respectively equipped with an exhaust pipe and a circulation pipe, the circulation pipe is connected between the second waste heat exchanger and the thermal oil heater, and the exhaust pipe is connected to the second waste heat exchanger; Wherein, a third solenoid valve and a fourth solenoid valve are installed on the exhaust pipe and the circulation pipe respectively to control the opening of the exhaust pipe and the circulation pipe; Furthermore, the gas exhausted from the pre-oxidation furnace enters the exhaust duct and the circulation duct respectively to form an exhaust airflow and a circulation airflow.

[0015] In an optional embodiment, a thermal oil furnace is provided on one side of the thermal oil heater, and a circulating oil circuit is provided inside the thermal oil furnace and the thermal oil heater; And, the thermal oil furnace is connected to the circulating oil circuit of the thermal oil heater; One side of the thermal oil furnace is connected to a natural gas source.

[0016] In an optional embodiment, one end of the thermal oil boiler is connected to a third waste heat exchanger, and circulating cooling water is provided inside the third waste heat exchanger, and the flue gas of the thermal oil boiler exchanges heat with the circulating cooling water of the third waste heat exchanger; The third waste heat exchanger is connected to the first waste heat exchanger.

[0017] In an optional embodiment, the pre-oxygen furnace hot air heating system coupled with heat recovery also includes a control module, a first solenoid valve is installed on the main pipeline, a second solenoid valve is installed on the air supply pipeline, and the second solenoid valve is electrically connected to the control module.

[0018] The beneficial effect of the present invention is that the present invention performs gradient heating of the fresh air by arranging multiple waste heat recovery devices, and then heats the circulating air in the pre-oxidation furnace with the fresh air, and then heats this part of the fresh air to above the process temperature through a thermal oil heater, and finally introduces preheated fresh air to mix it again, cools the mixed airflow to the process temperature, and replenishes the oxygen content.

[0019] The beneficial effect of this invention is that, by introducing an innovative design of indirect heating using a thermal oil furnace, this solution fundamentally avoids the risk of direct heating of the circulating air by traditional natural gas direct combustion. This technical approach completely isolates the natural gas combustion heat source from the circulating air flow, effectively eliminating the potential risk of localized overheating causing carbon fiber tow combustion.

[0020] This solution achieves continuous maintenance of flue gas temperature through an innovative design that efficiently exchanges heat between the high-temperature flue gas discharged from the pre-oxidation furnace and the fresh air in the waste heat recovery system. Specifically, the circulating cooling water first exchanges heat with the flue gas from the thermal oil furnace. After the circulating cooling water temperature is raised, it is transported to the first waste heat exchanger for heat exchange with the fresh air. The fresh air temperature is raised to above the critical point of tar condensation, and then transported to the second waste heat exchanger for heat exchange with the flue gas from the pre-oxidation furnace. This ensures that the flue gas from the pre-oxidation furnace itself remains at a stable high temperature throughout the entire transportation process, thus completely preventing the phase change and condensation of tar components caused by sudden temperature drops, effectively eliminating the risk of coking and blockage on the inner wall of the pipeline. At the same time, heat recovery is achieved from the high-temperature exhaust air, reducing heat loss and insulation requirements of the high-temperature exhaust duct.

[0021] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purposes and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A flow chart of a method for heating a pre-oxygen furnace with hot air coupled with heat recovery provided in an embodiment of the present disclosure; Figure 2 A schematic structural diagram of a pre-oxygen furnace hot air heating system coupled with heat recovery provided in an embodiment of the present disclosure; Figure 3 A schematic diagram of the connection relationship of a main pipeline provided in an embodiment of the present disclosure; Figure 4 A schematic diagram of the connection relationship of a waste heat recovery pipeline provided in an embodiment of the present disclosure.

[0025] In the picture: 1. First waste heat exchanger; 2. Second waste heat exchanger; 3. Thermal oil heater; 4. Thermal oil furnace; 5. Third waste heat exchanger; 6. Pre-oxidation furnace; 7. Natural gas source; 8. Control module; 11. Main duct; 12. Air supply duct; 13. Exhaust duct; 14. Circulation duct; 15. Waste heat recovery duct; 21. First fan; 22. Second fan; 23. Third fan; 24. Fourth fan; 25. Water pump; 31. First solenoid valve; 32. Second solenoid valve; 33. Third solenoid valve; 34. Fourth solenoid valve; 35. Fifth solenoid valve; 36. Sixth solenoid valve; 37. Seventh solenoid valve; 41. First temperature sensor; 42. Second temperature sensor; 51. Oxygen content sensor. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present disclosure, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present disclosure without making any creative efforts shall fall within the scope of protection of the present disclosure.

[0027] Research has found that the pre-oxidation process in the carbon fiber preparation process plays a decisive role in the performance of carbon fiber. At present, domestic pre-oxidation furnaces mainly use electric heating and direct natural gas heating, which have certain shortcomings: the energy consumption of the electric heating system is extremely high, the power consumption of the pre-oxidation furnace group accounts for too high a proportion of the production cost, and the power grid is prone to power shortage during peak hours; although direct natural gas heating can reduce power consumption, the combustion heater is placed in the air duct inside the furnace, and the risks of local high temperature and flue gas leakage are prominent. The pre-oxidation hot air temperature fluctuates greatly. When the temperature fluctuates too much, it is easy to affect the oxidation quality of the carbon fiber and even cause uncontrolled oxidation of the fiber and fire.

[0028] On the other hand, although the exhaust air from the pre-oxidation furnace is hot, it contains tar, making heat recovery difficult. Directly using fresh air and exhaust air for heat recovery can easily cause the tar components to undergo phase change and condense on the inner walls of the air supply duct, resulting in coking and blockage. Without heat recovery, the exhaust duct network is difficult to insulate and generates high indoor heat dissipation, impacting the workshop environment and wasting energy. Currently, there is a lack of a safe, stable, and energy-efficient method and system for heating the hot air from pre-oxidation furnaces.

[0029] At present, there is an urgent need to provide a hot air heating method and system for a pre-oxidation furnace coupled with heat recovery to solve the technical problem in the above-mentioned related technologies that the carbon fiber pre-oxidation furnace has high requirements for temperature fluctuations, and conventional heaters are unable to cope with the local high temperature in the air duct in the furnace, resulting in thermal runaway of the carbon fiber raw materials.

[0030] The defects in the above solutions are the results obtained by the inventors after practice and careful research. Therefore, the process of discovering the above problems and the solutions proposed by this disclosure for the above problems below should be the contributions made by the inventors to this disclosure during the disclosure process.

[0031] The following describes some embodiments of the present invention in detail with reference to the accompanying drawings. The following embodiments and features thereof may be combined with one another unless they conflict. Furthermore, in the accompanying drawings, the thickness of components may be exaggerated or reduced to effectively illustrate the technical content.

[0032] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0033] Based on the above research, the present disclosure provides a method for heating hot air from a pre-oxidation furnace coupled with heat recovery. The method divides the fresh air to be fed into the pre-oxidation furnace 6 into two paths. One path of fresh air is subjected to multiple gradient heating steps and then mixed with the other path of fresh air. After reaching the process temperature, the mixed air is fed into the pre-oxidation furnace 6. The method specifically includes the following steps: Step S1, sequentially connect the first waste heat recovery device, the second waste heat recovery device, the thermal oil heater 3, and the pre-oxidation furnace 6, connect the air supply pipe to the air inlet of the pre-oxidation furnace 6, and connect the air outlet of the pre-oxidation furnace 6 to the second waste heat recovery device and the thermal oil heater 3; Step S2: fresh air is passed to the first waste heat recovery device, and the fresh air exchanges heat with the first waste heat recovery device, and the temperature of the fresh air rises from the ambient temperature T0 to T1; Step S3: The fresh air passes through the first waste heat recovery device and is split into two routes: the main pipe and the supply air pipe. The fresh air in the main pipe enters the second waste heat recovery device for heat exchange, and the fresh air temperature rises from T1 to T2. Step S4: the fresh air passes through the second waste heat recovery device, and the circulating air in the pre-oxidation furnace 6 is mixed with the fresh air passing through the second waste heat recovery device, thereby raising the temperature of the mixed air from T2 to T3; Step S5: The mixed air enters the thermal oil heater 3 to exchange heat with the oil, and the temperature of the mixed air rises from T3 to T4; In step S6 , the mixed air is mixed with the fresh air in the air supply duct, and the temperature is reduced from T4 to T5 , and the mixed air enters the pre-oxidation furnace 6 .

[0034] In the above steps, T0 is the ambient temperature, T1 is preferably 30°C to 70°C, T2 is preferably 50°C to 100°C, T3 is preferably 120°C to 170°C, T4 is preferably 260°C to 280°C, and T5 is preferably 200°C to 250°C. That is, the fresh air passes through the first waste heat recovery device, and the temperature rises from the ambient temperature T0 (20℃-30℃) to T1 (30℃~70℃). The fresh air passes through the second waste heat recovery device, and the temperature rises from T1 (30℃~70℃) to T2 (50℃~100℃). After the fresh air is mixed with the circulating air, the temperature rises from T2 (50℃~100℃) to T3 (120℃~170℃). The mixed air enters the thermal oil heater 3 for heat exchange with the oil, and the temperature rises from T3 (120℃~170℃) to T4 (260℃~280℃). The mixed air mixes with the fresh air in the air supply duct, and the temperature drops from T4 (260℃~280℃) to T5 (200℃~250℃).

[0035] According to the above steps, after one channel of fresh air is heated twice, it is mixed with the return air of the circulating air from the previous process in the pre-oxidation furnace 6 and subjected to the third gradient heating. At this time, the temperature of the mixed air formed by the fresh air and the circulating air has reached a relatively high level. Then, the fourth gradient heating is performed through the thermal oil heater 3, so that the temperature of the mixed air can be heated to a level higher than the process temperature in a short time. Then, another channel of fresh air that has only been heated once and has not been mixed is introduced, so that this fresh air is mixed again with the mixed air heated to a level higher than the process temperature. By controlling the flow rate of the newly introduced fresh air, the temperature of the mixed air can be accurately controlled at the process temperature.

[0036] By using gradient heating, the temperature of each local area in the pipeline is relatively controllable, and there is no problem of sudden temperature rise or drop. In addition, in the last heating stage, that is, the heating stage of the thermal oil heater 3, the mixed air has reached a higher temperature level, and there will be no local overheating or excessive temperature fluctuations, thereby avoiding the problem of uncontrolled oxidation or even combustion of the carbon fiber material.

[0037] On the other hand, setting the thermal oil heater 3 to heat the mixed air to a temperature exceeding the process temperature and introducing unheated fresh air for secondary mixing can ensure that the temperature of the mixed air is uniformly and accurately controlled before entering the pre-oxidation furnace 6. At the same time, the introduced fresh air can also supplement the oxygen content of the mixed air.

[0038] In at least one embodiment, in order to monitor the temperature of the mixed air discharged from the thermal oil heater 3 and perform precise control, a temperature sensor can be provided at the exhaust port of the thermal oil heater 3, and the target temperature of the exhaust port of the thermal oil heater 3 is set to T4 (260°C~280°C), and the actual temperature of the exhaust port of the thermal oil heater 3 is T a4 If T a4 <T4, then increase the power of thermal oil heater 3 and raise the temperature T a4 To T4; if T a4 > T4, then reduce the power of the thermal oil heater 3 and lower the temperature T a4 Through the above settings, when the system temperature fluctuates due to some factors, the temperature sensor can be used to continuously monitor and control the power of the thermal oil heater 3, ensuring that the actual temperature of the exhaust port of the thermal oil heater 3 can be adjusted in time to return to and maintain T4 (260℃~280℃).

[0039] In at least one embodiment, in order to monitor the mixed air temperature at the air inlet of the pre-oxidation furnace 6 and ensure that the mixed air temperature entering the pre-oxidation furnace 6 is maintained at the process temperature, a temperature sensor can be installed at the air inlet of the pre-oxidation furnace 6, and the target temperature of the air inlet of the pre-oxidation furnace 6 is set to T5 (200°C~250°C). After the mixed air passes through the thermal oil heater 3 and is mixed with the fresh air in the air supply pipe, the actual temperature is reduced to T a5 If T a5 <T5, increase the flow rate of mixed air and reduce the flow rate of fresh air in the air supply duct to increase T a5 To T5; if T a5 > T5, reduce the flow of mixed air and increase the flow of fresh air in the air supply duct to reduce T a5 Through the above arrangement, when the temperature of the mixed air entering the pre-oxidation furnace 6 changes, the flow rate of the mixed air and the flow rate of the unheated fresh air can be adjusted synchronously to accurately adjust the temperature of the mixed air entering the pre-oxidation furnace 6.

[0040] It should be noted that although the temperature of the mixed air entering the pre-oxidation furnace 6 can be adjusted by adjusting the flow rate of the mixed air or the flow rate of the unheated fresh air alone, the unheated fresh air will also affect the oxygen content of the mixed air that finally enters the pre-oxidation furnace 6. Therefore, the adjustment of a single factor will directly lead to a change in the oxygen content of the mixed air. Therefore, it is necessary to adjust the two factors at the same time to ensure that while maintaining the temperature, the oxygen content is also maintained within the range that meets the process requirements.

[0041] Specifically, in at least one embodiment, an oxygen content sensor 51 can be installed at the air inlet of the pre-oxidation furnace 6, and the target oxygen concentration in the pre-oxidation furnace 6 is set to C1, and the actual oxygen concentration in the pre-oxidation furnace 6 is C0; if C0 < C1, the fresh air volume Q1 is increased to increase the oxygen concentration of the pre-oxidation furnace 6, and the exhaust air volume Q2 of the pre-oxidation furnace 6 is increased at the same time, and the exhaust air volume Q2 of the pre-oxidation furnace 6 is increased, and the exhaust air volume Q2 is 1 to 1.2 times that of Q1 to maintain the pressure state in the furnace as a negative pressure, and the vacuum degree is -30Pa to 0Pa, until the oxygen concentration in the furnace C0=C1; if C0>C1, the exhaust air volume of the pre-oxidation furnace 6 is reduced, and the fresh air volume is reduced at the same time to reduce the oxygen concentration of the pre-oxidation furnace 6 until C0=C1.

[0042] In addition, refer to Figure 2 The embodiment of the present disclosure also provides a pre-oxidation furnace hot air heating system coupled with heat recovery, which is used to perform the pre-oxidation furnace hot air heating method coupled with heat recovery as described above. The pre-oxidation furnace hot air heating system coupled with heat recovery includes: a main pipeline 11, and a first waste heat exchanger 1, a second waste heat exchanger 2, a thermal oil heater 3 and a pre-oxidation furnace 6 connected in sequence through the main pipeline 11.

[0043] Reference Figure 3 The exhaust port of pre-oxidation furnace 6 is equipped with a tee. One end of the tee is connected to pre-oxidation furnace 6, and the other two ends are connected to exhaust pipe 13 and circulation pipe 14, respectively. Circulation pipe 14 is connected to main pipe 11 between second waste heat exchanger 2 and thermal oil heater 3, and exhaust pipe 13 is connected to second waste heat exchanger 2. The gas exhausted from pre-oxidation furnace 6 passes through the tee and is split into two streams: one enters circulation pipe 14 to form a circulating airflow, and the other enters exhaust pipe 13 to form an exhaust airflow.

[0044] Specifically, refer to Figure 3 , Xinfengyan f1 Direction after passing through the first waste heat exchanger 1 is divided into two paths, one of which continues along the main pipe 11, that is, continues along f1 direction, after passing through the second waste heat exchanger 2, and along f12 The circulating airflow flowing in the direction of f1The other fresh air enters the air supply duct 12, which is located between the first waste heat exchanger 1 and the second waste heat exchanger 2, and the other end extends to the outlet of the thermal oil heater 3. The fresh air in the air supply duct 12 flows along the f2 The second waste heat exchanger 2 and the thermal oil heater 3 are bypassed in the direction and mixed with the mixed air in the main pipe 11 for the second time. f1 The gas discharged from the pre-oxidation furnace 6 is divided into f11 The exhaust airflow flows in the direction and along f12 Circulating airflow flowing in the same direction.

[0045] Reference Figure 3 The exhaust airflow passes through the second waste heat exchanger 2, where it exchanges heat with the fresh air that has passed through the first waste heat exchanger 1, thereby performing a second gradient heating on the fresh air. The circulating airflow enters the main duct 11 and mixes with the fresh air that has passed through the second waste heat exchanger 2, thereby performing a third gradient heating on the fresh air.

[0046] Reference Figure 3 In at least one embodiment, a third solenoid valve 33 and a fourth solenoid valve 34 are respectively installed on the exhaust duct 13 and the circulation duct 14 to control the opening of the exhaust duct 13 and the circulation duct 14 to adjust the ratio of the exhaust airflow and the circulation airflow discharged from the pre-oxidation furnace 6 into the exhaust duct 13 or the circulation duct 14.

[0047] Reference Figure 4 In at least one embodiment, a thermal oil furnace 4 is provided on one side of the thermal oil heater 3, and a circulating oil circuit is provided inside the thermal oil furnace 4 and the thermal oil heater 3. The thermal oil furnace 4 is in communication with the circulating oil circuit of the thermal oil heater 3. One side of the thermal oil furnace 4 is connected to a natural gas source 7. Through the above arrangement, the natural gas source 7 continuously supplies natural gas into the thermal oil furnace 4, and burns and heats the oil in the thermal oil furnace 4. A hot oil pump is provided between the circulating oil circuit of the thermal oil furnace 4 and the circulating oil circuit of the thermal oil heater 3, thereby sending the oil in the thermal oil furnace 4 into the thermal oil heater 3, and returning it to the thermal oil furnace 4 through the other end, thereby continuously heating the thermal oil heater 3, so that the thermal oil heater 3 performs a fourth gradient heating on the hot mixed air.

[0048] Reference Figure 4In at least one embodiment, one end of the thermal oil boiler 4 is connected to the third waste heat exchanger 5, and the third waste heat exchanger 5 has circulating cooling water inside. The flue gas of the thermal oil boiler 4 exchanges heat with the circulating cooling water of the third waste heat exchanger 5. In addition, the third waste heat exchanger 5 is connected to the first waste heat exchanger 1 through two waste heat recovery pipes 15. After the circulating cooling water is heated, it passes through one of the waste heat recovery pipes 15 along the f3 The heat is then transported to the first waste heat exchanger 1 for heat exchange with fresh air, and then passes through another waste heat recovery pipe 15 along the f 3 The waste heat is then transported back to the third waste heat exchanger 5. A water pump 25 is installed on at least one waste heat recovery pipe 15 to circulate the cooling water. That is, after the natural gas heats the thermal oil boiler 4, the flue gas enters the third waste heat exchanger 5 and heats it. The third waste heat exchanger 5 then heats the first waste heat exchanger 1 via the circulating cooling water. This fully utilizes the residual heat of the flue gas after the natural gas heats the thermal oil heater 3.

[0049] Reference Figure 2 In at least one embodiment, the pre-oxidation furnace hot air heating system coupled with heat recovery further includes a control module 8 to control the opening and closing of each pipeline and the degree of opening, and to monitor the temperature and oxygen content within the main pipeline 11. Furthermore, a first solenoid valve 31 is installed in the main pipeline 11 between the second waste heat exchanger 2 and the thermal oil heater 3. A second solenoid valve 32 is installed in the supply air pipeline 12. A fifth solenoid valve 35 is installed at the exhaust port of the pre-oxidation furnace 6. A third solenoid valve 33 is installed in the exhaust pipeline 13. A fourth solenoid valve 34 is installed in the circulation pipeline 14. A sixth solenoid valve 36 is installed between the natural gas source 7 and the thermal oil boiler 4. A seventh solenoid valve 37 is installed in the waste heat recovery pipeline 15. A first temperature sensor 41 is installed at the exhaust port of the thermal oil heater 3, and a second temperature sensor 42 is installed at the air inlet of the pre-oxidation furnace 6. An oxygen content sensor 51 is also installed at the air inlet of the pre-oxidation furnace 6. All of these components are electrically connected to the control module 8. The control module 8 can receive feedback from the first temperature sensor 41 to control the opening of the sixth solenoid valve 36, thereby adjusting the flow rate of the natural gas source 7 and, in turn, the heating power of the thermal oil furnace 4. The control module 8 can receive feedback from the second temperature sensor 42 to adjust the opening of the fourth solenoid valve 34 and the second solenoid valve 32, thereby adjusting the proportion of recirculating air and the proportion of fresh air entering the supply air duct 12. The control module 8 can receive feedback from the oxygen content sensor 51 to adjust the opening of the third solenoid valve 33 and the fourth solenoid valve 34, thereby adjusting the proportion of recirculating air entering the circulation duct 14. In addition, the operator can also set the corresponding control logic according to actual conditions to control other components and implement related functions, which will not be detailed here.

[0050] Reference Figure 2 In at least one embodiment, in order to control the continuous and stable flow of airflow in each pipeline, a first fan 21 is installed at the starting position of the main pipeline 11, a second fan 22 is installed at the air inlet of the pre-oxidation furnace 6, a third fan 23 is installed at the end position of the main pipeline 11, and a fourth fan 24 is installed at the air inlet of the thermal oil furnace 4.

[0051] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. With the above-mentioned ideal embodiment of the present invention as inspiration, through the above-mentioned description, relevant staff can make various changes and modifications without departing from the scope of the technical idea of ​​the disclosed embodiment. The technical scope of the disclosed embodiment is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for heating a pre-oxygen furnace with hot air coupled with heat recovery, characterized in that: The fresh air to be fed into the pre-oxidation furnace is divided into two paths. One path of fresh air is heated multiple times by gradient heating and then mixed with the other path of fresh air. After reaching the process temperature, it is fed into the pre-oxidation furnace. The specific steps include: Step S1, sequentially connecting the first waste heat recovery device, the second waste heat recovery device, the thermal oil heater (3), and the pre-oxidation furnace (6), connecting the air supply pipe to the air inlet of the pre-oxidation furnace (6), and connecting the air outlet of the pre-oxidation furnace (6) to the second waste heat recovery device and the thermal oil heater (3); Step S2: fresh air is passed to the first waste heat recovery device, and the fresh air exchanges heat with the first waste heat recovery device, and the temperature of the fresh air rises from the ambient temperature T0 to T1; Step S3: The fresh air passes through the first waste heat recovery device and is split into two routes: the main pipe and the supply air pipe. The fresh air in the main pipe enters the second waste heat recovery device for heat exchange, and the fresh air temperature rises from T1 to T2. Step S4, the fresh air passes through the second waste heat recovery device, and the circulating air in the pre-oxidation furnace (6) is mixed with the fresh air passing through the second waste heat recovery device, thereby raising the temperature of the mixed air from T2 to T3; Step S5, the mixed air enters the thermal oil heater (3) to exchange heat with the oil, and the temperature of the mixed air rises from T3 to T4; In step S6, the mixed air is mixed with the fresh air in the air supply duct, the temperature is reduced from T4 to T5, and the mixed air enters the pre-oxidation furnace (6).

2. The hot air heating method for a pre-oxygen furnace coupled with heat recovery according to claim 1, characterized in that: Set the target temperature of the exhaust port of the thermal oil heater (3) to T4, and the actual temperature of the exhaust port of the thermal oil heater (3) to T a4 ; If T a4 <T4, then increase the power of the thermal oil heater (3) and raise the temperature T a4 To T4; If T a4 > T4, then reduce the power of the thermal oil heater (3) and lower the temperature T a4 To T4.

3. The hot air heating method for a pre-oxygen furnace coupled with heat recovery according to claim 1, characterized in that: The target temperature of the air inlet of the pre-oxidation furnace (6) is set to T5. After the mixed air from the thermal oil heater (3) is mixed with the fresh air in the air supply pipe, the actual temperature is reduced to T a5 ; If T a5 <T5, then increase the circulating air flow and reduce the proportion of fresh air in the air supply duct to increase T a5 To T5; If T a5 > T5, reduce the circulating air flow and increase the proportion of fresh air in the air supply duct to reduce T a5 To T5.

4. The hot air heating method for a pre-oxygen furnace coupled with heat recovery according to claim 1, characterized in that: The target oxygen concentration in the pre-oxidation furnace (6) is set to C1, and the actual oxygen concentration in the pre-oxidation furnace (6) is set to C0; If C0<C1, then the fresh air volume Q1 is increased to increase the oxygen concentration of the pre-oxidation furnace (6), and at the same time, the exhaust air volume Q2 of the pre-oxidation furnace (6) is increased, and the exhaust air volume Q2 is set to be 1 to 1.2 times of Q1 to maintain the pressure state in the furnace at a negative pressure, until the oxygen concentration C0 in the furnace equals C1; If C0>C1, reduce the exhaust air volume of the pre-oxidation furnace (6) and reduce the fresh air volume at the same time to reduce the oxygen concentration in the pre-oxidation furnace (6) until C0=C1.

5. A pre-oxygen furnace hot air heating system coupled with heat recovery, characterized in that: The method for heating hot air from a pre-oxygen furnace coupled with heat recovery according to any one of claims 1 to 4 is applied, and the pre-oxygen furnace hot air heating system coupled with heat recovery comprises: A main pipeline (11), and a first waste heat exchanger (1), a second waste heat exchanger (2), a thermal oil heater (3), and a pre-oxidation furnace (6) connected in sequence through the main pipeline (11); The exhaust port of the pre-oxidation furnace (6) is connected between the second waste heat exchanger (2) and the thermal oil heater (3); An air supply pipe (12) is provided between the thermal oil heater (3) and the pre-oxidation furnace (6), and the other end of the air supply pipe (12) is connected between the first waste heat exchanger (1) and the second waste heat exchanger (2).

6. The pre-oxidation furnace hot air heating system coupled with heat recovery according to claim 5, characterized in that: The exhaust port of the pre-oxidation furnace (6) is respectively equipped with an exhaust pipe (13) and a circulation pipe (14), the circulation pipe (14) is connected between the second waste heat exchanger (2) and the thermal oil heater (3), and the exhaust pipe (13) is connected to the second waste heat exchanger (2); Wherein, a third solenoid valve (33) and a fourth solenoid valve (34) are respectively installed on the exhaust pipe (13) and the circulation pipe (14) to control the opening of the exhaust pipe (13) and the circulation pipe (14); Furthermore, the gas exhausted from the pre-oxidation furnace (6) enters the exhaust pipe (13) and the circulation pipe (14) respectively to form an exhaust gas flow and a circulation gas flow.

7. The pre-oxygen furnace hot air heating system coupled with heat recovery according to claim 5, characterized in that: A thermal oil furnace (4) is provided on one side of the thermal oil heater (3), and a circulating oil circuit is provided inside the thermal oil furnace (4) and the thermal oil heater (3); Furthermore, the thermal oil furnace (4) is connected to the circulating oil circuit of the thermal oil heater (3); One side of the thermal oil furnace (4) is connected to a natural gas source (7).

8. The pre-oxidation furnace hot air heating system coupled with heat recovery according to claim 5, characterized in that: One end of the thermal oil furnace (4) is connected to a third waste heat exchanger (5), and circulating cooling water is provided inside the third waste heat exchanger (5). The flue gas of the thermal oil furnace (4) exchanges heat with the circulating cooling water of the third waste heat exchanger (5); The third waste heat exchanger (5) is connected to the first waste heat exchanger (1).

9. The pre-oxidation furnace hot air heating system coupled with heat recovery according to claim 5, characterized in that: The pre-oxygen furnace hot air heating system coupled with heat recovery further includes a control module (8), a first solenoid valve (31) is installed on the main pipeline (11), a second solenoid valve (32) is installed on the air supply pipeline (12), and the second solenoid valve (32) is electrically connected to the control module (8).

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