Multi-energy-level steam utilization system for chemical plant

Abstract

The invention discloses a multi-energy-level steam utilization system for a chemical plant, relates to the technical field of flue gas heat recovery, and aims to solve the problems of serious waste of energy and possible environmental and safety risks in a diffusion process due to the fact that most of the tail gas treatment modes of the existing chemical plant adopt a catalytic combustion method or direct emptying, torch combustion and the like. Comprising a first heat insulation hearth, a second heat insulation hearth, a fuel gas burner, a fourth steam high-temperature section heat exchange device, a fourth steam medium-temperature section heat exchange device, a turn-back type flue, a first steam high-temperature section heat exchange device, a fourth steam low-temperature section heat exchange device, a third steam low-temperature section heat exchange device and a first steam low-temperature section heat exchange device. The flue gas heat recovery system and the flue gas heat recovery method are used for flue gas heat recovery.

Description

Technical Field

[0001] This invention relates to the field of flue gas heat recovery technology, and in particular to a multi-level steam utilization system for chemical plants. Background Technology

[0002] The core of modern large-scale chemical plants lies in their complex and highly integrated technological processes, among which coal gasification for hydrogen production and ethylene cracking are two representative fundamental processes. Coal gasification for hydrogen production typically uses coal or petroleum coke as raw material, reacting it with oxygen and steam in a gasifier under high temperature and pressure to produce syngas, primarily composed of hydrogen and carbon monoxide. This syngas undergoes subsequent conversion, purification, and separation units to ultimately obtain high-purity hydrogen, while simultaneously producing a large amount of tail gas rich in CO, H2, and a small amount of CH4. Ethylene cracking, on the other hand, uses hydrocarbons such as naphtha and ethane as raw materials, undergoing high-temperature steam thermal cracking in a cracking furnace to produce key olefin products such as ethylene and propylene. This process also produces cracked gas rich in hydrogen, methane, and light hydrocarbons. After rapid cooling, compression, and cryogenic separation, this mixture extracts the main products while also separating a considerable amount of by-product fuel gas.

[0003] In typical chemical processes such as coal gasification for hydrogen production and ethylene cracking, the resulting tail gas, containing combustible components such as hydrogen, carbon monoxide, and low-carbon hydrocarbons, has a considerable calorific value. Traditional treatment methods often employ catalytic combustion, or direct venting or flare combustion, which not only result in serious energy waste but also pose environmental and safety risks during the venting process. Summary of the Invention

[0004] In order to address the problems raised in the background art, this invention provides a multi-level steam utilization system for chemical plants, which solves the problems mentioned above by using catalytic combustion, direct venting, or flare combustion for the treatment of exhaust gas in existing chemical plants. This system not only causes serious energy waste but also poses environmental and safety risks during the venting process.

[0005] The technical solution of this invention is:

[0006] A multi-level steam utilization system for chemical plants includes a first insulated furnace, a second insulated furnace, a fuel gas burner, a fourth type of high-temperature steam heat exchanger, a fourth type of medium-temperature steam heat exchanger, a deflecting flue, a first type of high-temperature steam heat exchanger, a fourth type of low-temperature steam heat exchanger, a third type of low-temperature steam heat exchanger, a first type of low-temperature steam heat exchanger, an SCR denitrification system, and a second type of low-temperature steam heat exchanger.

[0007] Multiple fuel gas burners are installed in both the first and second adiabatic furnaces. A fourth type of high-temperature steam heat exchanger is installed in the first adiabatic furnace, and a fourth type of medium-temperature steam heat exchanger is installed in the second adiabatic furnace. The top exhaust sections of the first and second adiabatic furnaces are merged and connected to a zigzag flue. The rising section of the zigzag flue is equipped with a first type of high-temperature steam heat exchanger, a fourth type of low-temperature steam heat exchanger, a third type of low-temperature steam heat exchanger, and a first type of low-temperature steam heat exchanger, arranged sequentially from bottom to top. The descending section of the zigzag flue is equipped with an SCR denitrification system, a second type of low-temperature steam heat exchanger, and the heating end of a tubular air preheater, arranged sequentially. The heating end of the tubular air preheater is located above the fuel gas burners in the first and second adiabatic furnaces.

[0008] Furthermore, 6-10 fuel gas burners are installed in both the first and second adiabatic furnaces.

[0009] Furthermore, the second type of steam low-temperature section heat exchanger is equipped with a second type of steam flow regulating valve group and a second type of steam pressure remote transmission instrument on the steam inlet pipeline, a second type of steam venting device is installed at the high point of the steam inlet pipeline, a second type of steam safety valve and a second type of steam spray desuperheating device are installed on the steam outlet pipeline, and a second type of steam condensate trap is installed at the low point of the steam outlet pipeline.

[0010] Furthermore, the third type of steam low-temperature section heat exchanger is equipped with a third type of steam flow regulating valve group and a third type of steam pressure remote transmission instrument on the steam inlet pipeline, a third type of steam upper condensate drain device is installed at the lower part of the steam inlet pipeline, a third type of steam safety valve and a third type of steam spray desuperheating device are installed on the steam outlet pipeline, and a third type of steam lower condensate drain device is installed at the lower part of the steam outlet pipeline.

[0011] Furthermore, the first type of high-temperature steam heat exchanger and the first type of low-temperature steam heat exchanger are connected in series to form the first type of steam heat exchanger. The steam inlet pipeline of the first type of low-temperature steam heat exchanger is equipped with a first type of steam flow regulating valve group and a first type of steam pressure remote transmission instrument. The lower part of the steam inlet pipeline of the first type of low-temperature steam heat exchanger is equipped with a first type of steam upper condensate drain device. The steam outlet pipeline of the first type of high-temperature steam heat exchanger is equipped with a first type of steam safety valve and a first type of steam spray desuperheating device. The lower part of the steam outlet pipeline of the first type of high-temperature steam heat exchanger is equipped with a first type of steam lower condensate drain device.

[0012] Furthermore, the fourth type of steam heat exchanger consists of a low-temperature section heat exchanger, a left heat exchange tube of a medium-temperature section heat exchanger, a high-temperature section heat exchanger, and a right heat exchange tube of a medium-temperature section heat exchanger connected in series. A fourth type of steam heat exchanger is constructed by installing a steam flow regulating valve group and a fourth type of steam pressure remote transmission instrument on the steam inlet pipeline of the low-temperature section heat exchanger. A fourth type of steam venting device and a fourth type of steam safety valve are installed on the steam outlet pipeline of the right heat exchange tube of the medium-temperature section heat exchanger. A fourth type of steam condensate trap is installed at the lower end of the steam outlet pipeline of the right heat exchange tube of the medium-temperature section heat exchanger. A fourth type of steam primary spray desuperheating device is installed on the connecting pipe between the left heat exchange tube of the medium-temperature section heat exchanger and the high-temperature section heat exchanger. A fourth type of steam secondary spray desuperheating device is installed on the connecting pipe between the high-temperature section heat exchanger and the right heat exchange tube of the medium-temperature section heat exchanger.

[0013] Furthermore, the second type of low-temperature steam heat exchanger has a steam inlet pressure of 4.5 MPa and a temperature of 250°C, and an outlet steam pressure of 4.0 MPa and a temperature of 400°C.

[0014] Furthermore, the third type of low-temperature steam heat exchanger has a steam inlet pressure of 6.5 MPa and a temperature of 220°C, and an outlet steam pressure of 6.0 MPa and a temperature of 450°C.

[0015] Furthermore, the first type of steam heat exchanger has a steam inlet pressure of 1.8 MPa and a temperature of 158°C, and an outlet steam pressure of 1.5 MPa and a temperature of 200°C.

[0016] Furthermore, the fourth type of steam heat exchanger has a steam inlet pressure of 10.8 MPa and a temperature of 350°C, and an outlet steam pressure of 9.8 MPa and a temperature of 540°C.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. A multi-stage steam utilization system for chemical plants, comprising two independent first and second adiabatic furnaces, allows for the dispersed combustion of different fuel gases, improving combustion efficiency while controlling the formation of nitrogen oxides and effectively reducing pollutant emissions. Simultaneously, a fourth type of high-temperature steam heat exchanger is installed in the first adiabatic furnace, and a fourth type of medium-temperature steam heat exchanger is installed in the second adiabatic furnace. This allows the two furnaces to accommodate different fuel gases, with varying furnace temperatures, achieving cascaded utilization and efficient distribution of thermal energy, further enhancing the overall thermal efficiency of the system.

[0019] 2. A multi-stage steam heat exchange network is formed by the fourth type of high-temperature steam heat exchange device, the fourth type of medium-temperature steam heat exchange device, the first type of high-temperature steam heat exchange device, the fourth type of low-temperature steam heat exchange device, the third type of low-temperature steam heat exchange device, and the first type of low-temperature steam heat exchange device. This network facilitates heat exchange between the flue gas in the first insulated furnace, the second insulated furnace, and the return flue, fully recovering waste heat from flue gas in different temperature zones and significantly improving energy utilization efficiency.

[0020] 3. Water spray desuperheating devices are installed on the connecting pipes of the first type of steam heat exchanger, the second type of low-temperature steam heat exchanger, and the third type of low-temperature steam heat exchanger to regulate the steam temperature at each stage and prevent the outlet steam temperature from exceeding the design temperature. A two-stage water spray desuperheating device is designed on the connecting pipes on the tube screen between the furnace heating surfaces of the fourth type of steam heat exchanger to prevent the tube screen inside the insulated furnace from overheating and the metal wall temperature from exceeding the material's allowable temperature preset value. It also controls the outlet steam temperature of the fourth type of steam heat exchanger to prevent it from exceeding the temperature limit, thereby protecting the tube screen, pipelines, and subsequent related equipment. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention;

[0022] Figure 2 for Figure 1 A longitudinal sectional view;

[0023] Figure 3 for Figure 1 Sectional view at AA;

[0024] Figure 4 This is a system flow diagram of the second type of low-temperature steam heat exchanger.

[0025] Figure 5 This is a system flow diagram of the third type of low-temperature steam heat exchanger.

[0026] Figure 6 This is a system flow diagram of the first type of steam heat exchanger;

[0027] Figure 7 This is a system flow diagram for the fourth type of steam heat exchanger.

[0028] In the diagram: 1. First adiabatic furnace; 2. Second adiabatic furnace; 3. Fuel gas burner; 4. Fourth type of high-temperature steam heat exchanger; 5. Fourth type of medium-temperature steam heat exchanger; 6. Reversible flue; 7. First type of high-temperature steam heat exchanger; 8. Fourth type of low-temperature steam heat exchanger; 9. Third type of low-temperature steam heat exchanger; 10. First type of low-temperature steam heat exchanger; 11. SCR denitrification system; 12. Second type of low-temperature steam heat exchanger; 13. Tubular air preheater; 14. Second type of steam flow regulating valve assembly; 15. Second type of steam pressure remote transmission instrument; 16. Second type of steam venting device; 17. Second type of steam condensate trap; 18. Second type of steam safety valve; 19. Second type of steam spray desuperheating device; 20. Third type of steam flow regulating valve assembly. 21. Valve assembly; 22. Third type of steam pressure remote transmission instrument; 23. Third type of steam upper condensate drain device; 24. Third type of steam lower condensate drain device; 25. Third type of steam safety valve; 26. Third type of steam spray desuperheating device; 27. First type of steam flow regulating valve assembly; 28. First type of steam pressure remote transmission instrument; 29. ​​First type of steam upper condensate drain device; 30. First type of steam safety valve; 31. First type of steam spray desuperheating device; 32. Fourth type of steam flow regulating valve assembly; 33. Fourth type of steam pressure remote transmission instrument; 34. Fourth type of steam venting device; 35. Fourth type of steam condensate drain device; 36. Fourth type of steam safety valve; 37. Fourth type of steam primary spray desuperheating device; 38. Fourth type of steam secondary spray desuperheating device. Detailed Implementation

[0029] Specific implementation method one: See Figure 1-3 As shown, a multi-level steam utilization system for chemical plants is provided in this embodiment, comprising a first insulated furnace 1, a second insulated furnace 2, a fuel gas burner 3, a fourth type of high-temperature steam heat exchanger 4, a fourth type of medium-temperature steam heat exchanger 5, a deflecting flue 6, a first type of high-temperature steam heat exchanger 7, a fourth type of low-temperature steam heat exchanger 8, a third type of low-temperature steam heat exchanger 9, a first type of low-temperature steam heat exchanger 10, an SCR denitrification system 11, and a second type of low-temperature steam heat exchanger 12.

[0030] Multiple fuel gas burners 3 are installed in both the first insulated furnace 1 and the second insulated furnace 2. A fourth type of high-temperature steam heat exchanger 4 is installed in the first insulated furnace 1, and a fourth type of medium-temperature steam heat exchanger 5 is installed in the second insulated furnace 2. The top exhaust sections of the first insulated furnace 1 and the second insulated furnace 2 are merged and connected to the zigzag flue 6. The flue gas rising section of the zigzag flue 6 is provided with a first type of high-temperature steam heat exchanger 7, a fourth type of low-temperature steam heat exchanger 8, a third type of low-temperature steam heat exchanger 9, and a first type of low-temperature steam heat exchanger 10 in sequence from bottom to top. The descending flue gas section of the zigzag flue 6 is provided with an SCR denitrification system 11, a second type of low-temperature steam heat exchanger 12, and the heating end of a tubular air preheater 13 in sequence. The heating end of the tubular air preheater 13 is located above the fuel gas burners 3 in the first insulated furnace 1 and the second insulated furnace 2.

[0031] Furthermore, the first adiabatic furnace 1 and the second adiabatic furnace 2 are arranged side by side, with their bottoms fixedly supported by fixed columns. The upper ends of the first adiabatic furnace 1 and the second adiabatic furnace 2 merge into a common flue gas passage, ensuring smooth introduction of flue gas into the zigzag flue 6. The fourth type of high-temperature steam heat exchanger 4 and the fourth type of medium-temperature steam heat exchanger 5 are self-supporting heat exchange tubes, with their upper and lower ends connected to the furnace top and bottom plates respectively through compensation fixing mechanisms to ensure thermal expansion compensation space. The zigzag flue 6 has an inverted U-shaped structure. The left side of the zigzag flue 6 is connected to the top flue gas exhaust section of the first adiabatic furnace 1 and the second adiabatic furnace 2, and the right side has a flue gas outlet connected to the subsequent dust removal system, ensuring that the flue gas meets emission standards after multi-stage heat exchange and denitrification treatment. The SCR denitrification system 11 is arranged at the top of the descending flue gas section of the zigzag flue 6. The SCR denitrification system 11 is used for efficient catalytic reduction of nitrogen oxides under high-temperature flue gas conditions. The fourth type of high-temperature steam heat exchanger 4, the fourth type of medium-temperature steam heat exchanger 5, the first type of high-temperature steam heat exchanger 7, the fourth type of low-temperature steam heat exchanger 8, the third type of low-temperature steam heat exchanger 9, and the first type of low-temperature steam heat exchanger 10 form a multi-stage steam heat exchange network to exchange heat with the flue gas in the first insulated furnace 1, the second insulated furnace 2, and the return flue 6, fully recovering the waste heat of flue gas in different temperature zones and significantly improving energy utilization efficiency.

[0032] This invention utilizes two independent first adiabatic furnaces 1 and second adiabatic furnaces 2 to disperse the combustion of different fuel gases, thereby improving combustion efficiency while controlling the formation of nitrogen oxides and effectively reducing pollutant emissions. Simultaneously, a fourth type of high-temperature steam heat exchanger 4 is installed in the first adiabatic furnace 1, and a fourth type of medium-temperature steam heat exchanger 5 is installed in the second adiabatic furnace 2. This allows the two furnaces to accommodate different fuel gases, resulting in different temperatures within the furnaces and achieving cascaded utilization and efficient distribution of thermal energy, further enhancing the overall thermal efficiency of the system.

[0033] Specific Implementation Method Two: See Figure 1-3 As shown, in this embodiment, 6-10 fuel gas burners 3 are provided in both the first adiabatic furnace 1 and the second adiabatic furnace 2.

[0034] Furthermore, in the first insulated furnace 1 and the second insulated furnace 2, there are preferably eight fuel gas burners 3, which can stably and fully burn fuel gases of various calorific values, and disperse the heat load in the furnace, control the generation of nitrogen oxides, and avoid the formation of local high temperature zones.

[0035] Specific implementation method three: See Figure 4 As shown, in this embodiment, the second type of steam low-temperature section heat exchanger 12 is provided with a second type of steam flow regulating valve group 14 and a second type of steam pressure remote transmission instrument 15 on the steam inlet pipeline. A second type of steam venting device 16 is provided at a high point on the steam inlet pipeline of the second type of steam low-temperature section heat exchanger 12. A second type of steam safety valve 18 and a second type of steam spray desuperheating device 19 are provided on the steam outlet pipeline of the second type of steam low-temperature section heat exchanger 12. A second type of steam condensate trap 17 is provided at a low point on the steam outlet pipeline of the second type of steam low-temperature section heat exchanger 12.

[0036] Furthermore, the second type of low-temperature steam heat exchanger 12 is located in the middle of the flue gas descending section of the zigzag flue 6, between the SCR denitrification system 11 and the tubular air preheater 13. A second type of steam flow regulating valve group 14 and a flow meter are installed on the steam inlet pipeline of the second type of low-temperature steam heat exchanger 12 to regulate the flow rate of incoming steam, thereby adjusting the steam flow rate to match the relationship between steam temperature and fuel. A second type of remote steam pressure instrument 15 is used to monitor the steam inlet pressure of each stage. A remote pressure instrument and a temperature thermocouple instrument are also installed at the steam outlet of the second type of low-temperature steam heat exchanger 12 to monitor changes in outlet steam pressure and prevent steam overheating or abnormal pressure. A second type of steam spray desuperheating device 19 is used to cool the steam outlet pipeline of the second type of low-temperature steam heat exchanger 12, and a remote pressure instrument and a flow regulating valve group are arranged on the inlet pipeline of the second type of steam condensate device 17 to regulate the condensate flow rate in real time.

[0037] Detailed Implementation Method Four: See [link] Figure 5 As shown, the third type of steam low-temperature section heat exchanger 9 in this embodiment is equipped with a third type of steam flow regulating valve group 20 and a third type of steam pressure remote transmission instrument 21 on the steam inlet pipeline. A third type of steam upper condensate drain device 22 is installed at the lower part of the steam inlet pipeline of the third type of steam low-temperature section heat exchanger 9. A third type of steam safety valve 24 and a third type of steam spray desuperheating device 25 are installed on the steam outlet pipeline of the third type of steam low-temperature section heat exchanger 9. A third type of steam lower condensate drain device 23 is installed at the lower part of the steam outlet pipeline of the third type of steam low-temperature section heat exchanger 9.

[0038] Furthermore, the third type of low-temperature steam heat exchanger 9 is located in the middle of the flue gas rising section of the zigzag flue 6, and is situated between the first type of low-temperature steam heat exchanger 10 and the third type of low-temperature steam heat exchanger 9. The valves and instruments of the third type of low-temperature steam heat exchanger 9 are configured in the same way as in Specific Embodiment Three.

[0039] Specific implementation method five: See Figure 6 As shown, in this embodiment, the first type of high-temperature steam heat exchanger 7 and the first type of low-temperature steam heat exchanger 10 are connected in series to form the first type of steam heat exchanger. The first type of low-temperature steam heat exchanger 10 is provided with a first type of steam flow regulating valve group 26 and a first type of steam pressure remote transmission instrument 27 on the steam inlet pipeline. The first type of upper steam condensate drain device 28 is provided at the lower part of the steam inlet pipeline of the first type of low-temperature steam heat exchanger 10. The first type of steam safety valve 30 and the first type of steam spray desuperheating device 31 are provided on the steam outlet pipeline of the first type of high-temperature steam heat exchanger 7. The first type of lower steam condensate drain device 29 is provided at the lower part of the steam outlet pipeline of the first type of high-temperature steam heat exchanger 7.

[0040] Furthermore, the first type of steam heat exchanger consists of two parts connected in series: a first type of high-temperature steam heat exchanger 7 and a first type of low-temperature steam heat exchanger 10. The first type of high-temperature steam heat exchanger 7 is located at the lowest part of the flue gas rising section of the zigzag flue duct 6, adjacent to the common exhaust channel at the upper end of the first insulated furnace 1 and the second insulated furnace 2, ensuring that the high-temperature flue gas preferentially contacts the first type of high-temperature steam heat exchanger 7 to achieve efficient energy recovery. The first type of low-temperature steam heat exchanger 10 is arranged at the highest point of the flue gas rising section of the zigzag flue duct 6 to absorb waste heat from the flue gas, further improving thermal efficiency. The valves and instruments of the first type of steam heat exchanger are configured the same as in specific embodiment three.

[0041] Specific implementation method six: See Figure 7As shown, in this embodiment, the fourth type of steam heat exchanger consists of a low-temperature section heat exchanger 8, a left heat exchanger tube of a medium-temperature section heat exchanger 5, a high-temperature section heat exchanger 4, and a right heat exchanger tube of a medium-temperature section heat exchanger 5 connected in series to form a fourth type of steam heat exchanger. A fourth type of steam flow regulating valve group 32 and a fourth type of steam pressure remote transmission instrument 33 are installed on the steam inlet pipeline of the low-temperature section heat exchanger 8. A fourth type of steam flow regulating valve group 32 and a fourth type of steam pressure remote transmission instrument 33 are installed on the steam outlet pipeline of the right heat exchanger tube of the medium-temperature section heat exchanger 5. The steam venting device 34 and the fourth type of steam safety valve 36 are provided. A fourth type of steam condensate drain device 35 is installed at the lower end of the steam outlet pipeline of the right heat exchanger of the fourth type of steam intermediate temperature section heat exchanger 5. A fourth type of steam primary water spray desuperheating device 37 is installed on the connecting pipe between the left heat exchanger of the fourth type of steam intermediate temperature section heat exchanger 5 and the fourth type of steam high temperature section heat exchanger 4. A fourth type of steam secondary water spray desuperheating device 38 is installed on the connecting pipe between the fourth type of steam high temperature section heat exchanger 4 and the right heat exchanger of the fourth type of steam intermediate temperature section heat exchanger 5.

[0042] Furthermore, the pressure and temperature parameters of the fourth type of steam are higher than those of the first, second, and third types of steam. The fourth type of steam is heated three times through the first insulated furnace 1, the second insulated furnace 2, and the return flue 6. The fourth type of steam flows sequentially through the low-temperature section heat exchanger 8, the left heat exchanger tube of the medium-temperature section heat exchanger 5, the high-temperature section heat exchanger 4, and the medium-temperature section heat exchanger 5 before being discharged through the steam outlet pipeline, thus achieving cascaded utilization of heat.

[0043] Water spray desuperheating devices are designed on the connecting pipes on the tube screens between the furnace heating surfaces of the left heat exchanger tube of the fourth type of steam medium-temperature section heat exchanger 5 and the right heat exchanger tubes of the fourth type of steam high-temperature section heat exchanger 4 and the fourth type of steam medium-temperature section heat exchanger 5. These two-stage water spray desuperheating devices prevent overheating of the tube screens inside the insulated furnace and prevent the metal wall temperature from exceeding the material's allowable temperature limit. They also control the outlet steam temperature of the fourth type of steam heat exchanger to prevent it from exceeding the limit, thus protecting the tube screens, pipes, and subsequent related equipment.

[0044] Detailed implementation method seven: See Figure 4 As shown, the second type of steam low-temperature section heat exchanger 12 in this embodiment has a steam inlet pressure of 4.5 MPa and a temperature of 250°C, and an outlet steam pressure of 4.0 MPa and a temperature of 400°C.

[0045] Detailed Implementation Method Eight: See also Figure 5 As shown, the third type of steam low-temperature section heat exchanger 9 in this embodiment has a steam inlet pressure of 6.5 MPa and a temperature of 220°C, and an outlet steam pressure of 6.0 MPa and a temperature of 450°C.

[0046] Detailed implementation method nine: See Figure 6 As shown, the steam inlet pressure of the first type of steam heat exchanger in this embodiment is 1.8 MPa, the temperature is 158°C, and the outlet steam pressure is 1.5 MPa, the temperature is 200°C.

[0047] Detailed Implementation Method Ten: See [link] Figure 7 As shown in this embodiment, the steam inlet pressure of the fourth type of steam heat exchanger is 10.8 MPa, the temperature is 350°C, and the steam outlet pressure is 9.8 MPa, the temperature is 540°C.

[0048] During operation, after the fuel gas burners 3 in the first and second adiabatic furnaces 1 and 2 are ignited, the high-temperature flue gas flows through the first and second adiabatic furnaces 1 and 2, heating the fourth type of high-temperature steam heat exchanger 4 and the fourth type of medium-temperature steam heat exchanger 5. It then enters the reversible flue 6, where it further exchanges heat with the first type of high-temperature steam heat exchanger 7, the fourth type of low-temperature steam heat exchanger 8, the third type of low-temperature steam heat exchanger 9, and the first type of low-temperature steam heat exchanger 10, gradually reducing the flue gas temperature. Subsequently, the flue gas enters the SCR denitrification system 11 for denitrification treatment. Next, the flue gas flows through the second type of low-temperature steam heat exchanger 12 for final steam heat exchange. Finally, the flue gas enters the heating end of the tubular air preheater 13, which provides preheated air to the fuel gas burners 3 in the first and second adiabatic furnaces 1 and 2 to improve combustion efficiency. At this point, the flue gas has completed all heat exchange and is discharged through the flue gas outlet at the lower end of the reversible flue 6.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-stage steam utilization system for chemical plants, characterized in that: It includes a first insulated furnace (1), a second insulated furnace (2), a fuel gas burner (3), a fourth type of high-temperature steam heat exchange device (4), a fourth type of medium-temperature steam heat exchange device (5), a zigzag flue (6), a first type of high-temperature steam heat exchange device (7), a fourth type of low-temperature steam heat exchange device (8), a third type of low-temperature steam heat exchange device (9), a first type of low-temperature steam heat exchange device (10), an SCR denitrification system (11), and a second type of low-temperature steam heat exchange device (12). Multiple fuel gas burners (3) are installed in both the first insulated furnace (1) and the second insulated furnace (2). A fourth type of high-temperature steam heat exchange device (4) is installed in the first insulated furnace (1), and a fourth type of medium-temperature steam heat exchange device (5) is installed in the second insulated furnace (2). The top exhaust sections of the first insulated furnace (1) and the second insulated furnace (2) are merged and connected to the zigzag flue (6). The flue gas rising section of the zigzag flue (6) is equipped with the first type of high-temperature steam heat exchange device from bottom to top. The descending flue gas section of the flue gas duct (6) is provided with the heating end of the SCR denitrification system (11), the second type of steam low temperature section heat exchange device (12), and the tubular air preheater (13). The heating end of the tubular air preheater (13) is located at the upper end of the fuel gas burner (3) in the first insulated furnace (1) and the second insulated furnace (2).

2. The multi-level steam utilization system for chemical plants according to claim 1, characterized in that: There are 6-10 fuel gas burners (3) in both the first insulated furnace (1) and the second insulated furnace (2).

3. The multi-level steam utilization system for chemical plants according to claim 1, characterized in that: The second type of steam low temperature section heat exchanger (12) is equipped with a second type of steam flow regulating valve group (14) and a second type of steam pressure remote transmission instrument (15) on the steam inlet pipeline. The second type of steam venting device (16) is installed at the high point of the steam inlet pipeline of the second type of steam low temperature section heat exchanger (12). The second type of steam safety valve (18) and the second type of steam spray desuperheating device (19) are installed on the steam outlet pipeline of the second type of steam low temperature section heat exchanger (12). The second type of steam condensate device (17) is installed at the low point of the steam outlet pipeline of the second type of steam low temperature section heat exchanger (12).

4. The multi-level steam utilization system for chemical plants according to claim 1, characterized in that: The third type of steam low temperature section heat exchanger (9) is equipped with a third type of steam flow regulating valve group (20) and a third type of steam pressure remote transmission instrument (21) on the steam inlet pipeline. The third type of steam upper condensate drain device (22) is installed at the lower part of the steam inlet pipeline of the third type of steam low temperature section heat exchanger (9). The third type of steam safety valve (24) and the third type of steam spray desuperheating device (25) are installed on the steam outlet pipeline of the third type of steam low temperature section heat exchanger (9). The third type of steam lower condensate drain device (23) is installed at the lower part of the steam outlet pipeline of the third type of steam low temperature section heat exchanger (9).

5. The multi-level steam utilization system for chemical plants according to claim 1, characterized in that: The first type of steam high temperature section heat exchange device (7) and the first type of steam low temperature section heat exchange device (10) are connected in series to form the first type of steam heat exchange device. The first type of steam low temperature section heat exchange device (10) is equipped with a first type of steam flow regulating valve group (26) and a first type of steam pressure remote transmission instrument (27) on the steam inlet pipeline. The first type of steam upper condensate drain device (28) is installed at the lower part of the steam inlet pipeline of the first type of steam low temperature section heat exchange device (10). The first type of steam safety valve (30) and the first type of steam spray desuperheating device (31) are installed on the steam outlet pipeline of the first type of steam high temperature section heat exchange device (7). The first type of steam lower condensate drain device (29) is installed at the lower part of the steam outlet pipeline of the first type of steam high temperature section heat exchange device (7).

6. The multi-level steam utilization system for chemical plants according to claim 1, characterized in that: The fourth type of steam heat exchanger consists of a low-temperature section heat exchanger (8), a left heat exchanger tube of a medium-temperature section heat exchanger (5), a high-temperature section heat exchanger (4), and a right heat exchanger tube of a medium-temperature section heat exchanger (5). The fourth type of steam heat exchanger is connected in series. A fourth type of steam flow regulating valve group (32) and a fourth type of steam pressure remote transmission instrument (33) are installed on the steam inlet pipeline of the fourth type of low-temperature section heat exchanger (8). A fourth type of steam venting device (33) is installed on the steam outlet pipeline of the right heat exchanger tube of the fourth type of medium-temperature section heat exchanger (5). 4) and the fourth type of steam safety valve (36), the fourth type of steam outlet pipe of the right heat exchanger of the fourth type of steam medium temperature section heat exchanger (5) is equipped with a fourth type of steam condensate drain device (35) at the bottom, the fourth type of steam first-stage water spray desuperheating device (37) is installed on the connecting pipe between the left heat exchanger of the fourth type of steam medium temperature section heat exchanger (5) and the fourth type of steam high temperature section heat exchanger (4), and the fourth type of steam second-stage water spray desuperheating device (38) is installed on the connecting pipe between the fourth type of steam high temperature section heat exchanger (4) and the right heat exchanger of the fourth type of steam medium temperature section heat exchanger (5).

7. The multi-level steam utilization system for chemical plants according to claim 3, characterized in that: The second type of low-temperature steam heat exchanger (12) has a steam inlet pressure of 4.5 MPa and a temperature of 250°C, and an outlet steam pressure of 4.0 MPa and a temperature of 400°C.

8. The multi-level steam utilization system for chemical plants according to claim 4, characterized in that: The third type of low-temperature steam heat exchanger (9) has a steam inlet pressure of 6.5 MPa and a temperature of 220°C, and an outlet steam pressure of 6.0 MPa and a temperature of 450°C.

9. The multi-stage steam utilization system for chemical plants according to claim 5, characterized in that: The first type of steam heat exchanger has a steam inlet pressure of 1.8 MPa and a temperature of 158°C, and an outlet steam pressure of 1.5 MPa and a temperature of 200°C.

10. The multi-level steam utilization system for chemical plants according to claim 6, characterized in that: The fourth type of steam heat exchanger has a steam inlet pressure of 10.8 MPa and a temperature of 350°C, and an outlet steam pressure of 9.8 MPa and a temperature of 540°C.

Images