A high-temperature and high-pressure waste heat recovery device for a sulfur-burning acid plant

Abstract

The application discloses a high-temperature and high-pressure waste heat recovery device for sulfuric acid production, and relates to the technical field of sulfuric acid production, in particular to a high-temperature and high-pressure waste heat recovery device for sulfuric acid production. The sulfuric acid production device comprises a sulfur burning furnace and a converter provided with five-stage converters, and the high-temperature and high-pressure waste heat recovery system comprises a fire tube boiler, low-temperature and high-temperature superheaters and first, second and third coal economizers. High-temperature gas in the sulfur burning furnace enters the first-stage converter through the fire tube boiler and the low-temperature superheater, and the gas output by the first-stage converter enters the second-stage converter through the high-temperature superheater. The gas output by the third-stage converter enters the second-stage coal economizer through a cold-heat exchanger, the gas in the fourth-stage converter enters the fifth-stage converter through the third-stage coal economizer, and the gas output by the fifth-stage converter enters the first-stage coal economizer. External feed water enters the low-temperature heat exchange pipe group in the first-stage coal economizer and the high-temperature heat exchange pipe group in the first-stage coal economizer through the second-stage coal economizer, and then enters the steam drum through the third-stage coal economizer. The steam in the steam drum enters the low-temperature superheater and then enters the high-temperature superheater. The application has the advantages of high heat energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to waste heat recovery systems, specifically to waste heat recovery devices for sulfuric acid production plants. Background Technology

[0002] Sulfur combustion and conversion are two crucial processes in sulfur-to-acid production. Sulfur combustion: Sulfur vapor reacts with oxygen in a sulfur combustion furnace to produce sulfur dioxide, releasing a large amount of heat. The sulfur combustion furnace typically produces high-temperature flue gas around 1000°C. Conversion: Sulfur dioxide is converted into sulfur trioxide in a converter with a catalyst. The converter typically consists of four or five stages. Each stage contains a catalyst, and the sulfur dioxide gas from the sulfur combustion furnace passes through each stage sequentially until the final stage, continuously converting into sulfur trioxide. The conversion of sulfur dioxide to sulfur trioxide in each stage is exothermic. Each stage has a reactant gas inlet and outlet. Sulfur dioxide gas enters from the reactant gas inlet of a particular stage and exits from the reactant gas outlet, cooling to the temperature required for the next stage of reaction before entering the next stage.

[0003] Currently, there are hundreds of sulfur-based acid production units in China. The waste heat recovery system for these units mainly recovers high and medium temperature heat energy from sulfur combustion and conversion processes.

[0004] Current waste heat recovery systems generally rely on the production of medium-pressure superheated steam at 3.82 MPa and 450 ℃ as a byproduct. This medium-pressure superheated steam is used to drive air fans and generate electricity.

[0005] To improve energy efficiency and accelerate carbon peaking, the thermal efficiency of waste heat recovery systems used in sulfuric acid production needs further research and development to achieve higher steam cycle thermal efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature and high-pressure waste heat recovery device for sulfuric acid production plants, which can provide high-temperature and high-pressure superheated steam with a pressure ≥9.0MPa(G) and a temperature ≥500℃, thereby greatly improving thermal efficiency.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant. The sulfuric acid production plant includes a sulfur incinerator and a converter. The converter contains, from bottom to top, a first-stage converter, a second-stage converter, a third-stage converter, a fourth-stage converter, and a fifth-stage converter. The high-temperature and high-pressure waste heat recovery system includes: a fire-tube boiler with a steam drum at the top, a superheater, and an economizer. The reaction gas outlet of the sulfur incinerator is connected to the flue gas inlet of the fire-tube boiler. The superheater includes a low-temperature superheater and a high-temperature superheater. The economizer includes a first-stage economizer, a second-stage economizer, and a third-stage economizer. The flue gas outlet of the fire-tube boiler is connected to the flue gas inlet of the low-temperature superheater. The flue gas outlet of the low-temperature superheater is connected to the reaction gas inlet of the first-stage converter. The reaction gas outlet of the first-stage converter is connected to the flue gas inlet of the high-temperature superheater. The flue gas outlet of the high-temperature superheater is connected to the reaction gas inlet of the second-stage converter. The reaction gas outlet of the second-stage converter is connected to the high-temperature medium inlet of a heat exchanger. The high-temperature medium outlet of the heat exchanger... The reactor is connected to the reaction gas inlet of the three-stage reformer; the reaction gas outlet of the three-stage reformer is connected to the heating medium inlet of the hot and cold heat exchanger, and the heating medium outlet of the hot and cold heat exchanger is connected to the flue gas inlet of the second-stage economizer; the reaction gas outlet of the four-stage reformer is connected to the flue gas inlet of the third-stage economizer, the flue gas outlet of the third-stage economizer is connected to the reaction gas inlet of the fifth-stage reformer, and the reaction gas outlet of the fifth-stage reformer is connected to the flue gas inlet of the first-stage economizer; high-temperature stage heat exchange tube groups and low-temperature stage heat exchange tube groups are sequentially arranged in the direction of gas flow in the first-stage economizer; the inlet of the low-temperature stage heat exchange tube group is connected to the external water supply pipe; the outlet of the low-temperature stage heat exchange tube group is connected to the inlet of the second-stage economizer; the outlet of the second-stage economizer is connected to the inlet of the high-temperature stage heat exchange tube group in the first-stage economizer; the outlet of the high-temperature stage heat exchange tube group is connected to the inlet of the third-stage economizer; the outlet of the third-stage economizer is connected to the steam drum; the steam outlet of the steam drum is connected to the steam inlet of the low-temperature superheater; and the steam outlet of the low-temperature superheater is connected to the steam inlet of the high-temperature superheater.

[0008] Furthermore, in the aforementioned high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant, a water spray desuperheater is installed at the steam inlet of the high-temperature superheater, and the water spray desuperheater is connected to an external water supply pipe.

[0009] Furthermore, in the aforementioned high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant, the fire-tube boiler adopts a flexible thin tube sheet structure.

[0010] Furthermore, in the aforementioned high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant, the heat exchange tubes in the superheater and economizer are all finned tubes.

[0011] Furthermore, in the aforementioned high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant, the flue gas outlet of the secondary economizer is connected to the inlet of the first absorption tower, the outlet of the first absorption tower is connected to the inlet of the medium to be heated in the cold and hot heat exchanger, the outlet of the medium to be heated in the cold and hot heat exchanger is connected to the inlet of the medium to be heated in the hot heat exchanger, and the outlet of the medium to be heated in the hot heat exchanger is connected to the inlet of the reaction gas inlet of the four-stage converter.

[0012] Furthermore, in the aforementioned high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant, the flue gas outlet of the primary economizer is connected to the inlet of the second absorption tower, and the outlet of the second absorption tower is connected to the chimney.

[0013] The advantages of this invention are: it can recover the heat generated by the sulfuric acid production unit to produce high-temperature and high-pressure superheated steam with a pressure of 9.81 MPa and a temperature of 540°C. The power generation efficiency is greatly improved by using high-temperature and high-pressure superheated steam. Therefore, this high-temperature and high-pressure waste heat recovery device can greatly improve the thermal energy utilization efficiency. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of a high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant according to the present invention. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and preferred embodiments.

[0016] like Figure 1 As shown, a high-temperature and high-pressure waste heat recovery device for a sulfuric acid production unit is disclosed. The sulfuric acid production unit includes a sulfur incinerator 2 and a converter 1. The converter 1 contains, from bottom to top, a first-stage converter 11, a second-stage converter 12, a third-stage converter 13, a fourth-stage converter 14, and a fifth-stage converter 15. The high-temperature and high-pressure waste heat recovery system includes a fire-tube boiler 4 with a steam drum 41 at the top, a superheater, and an economizer. The superheater includes a low-temperature superheater 5 and a high-temperature superheater 6. The economizer includes a first-stage economizer 31, a second-stage economizer 32, and a third-stage economizer 33. To improve heat exchange efficiency, the heat exchange tubes in the superheater and economizer in this embodiment are all finned tubes. In this embodiment, the fire-tube boiler 4 uses a flexible thin tube sheet, which greatly improves the deformation resistance of the fire-tube boiler 4 and enhances its operational stability at high temperatures.

[0017] The reaction gas outlet of the sulfur incinerator 2 is connected to the flue gas inlet of the fire-tube boiler 4. The flue gas outlet of the fire-tube boiler 4 is connected to the flue gas inlet of the low-temperature superheater 5. The flue gas outlet of the low-temperature superheater 5 is connected to the reaction gas inlet of the first-stage reformer 11. The reaction gas outlet of the first-stage reformer 11 is connected to the flue gas inlet of the high-temperature superheater 6. The flue gas outlet of the high-temperature superheater 6 is connected to the reaction gas inlet of the second-stage reformer 12. In this embodiment, the reaction gas outlet of the second-stage reformer 12 is connected to the high-temperature medium inlet 81 of the heat exchanger 8, and the high-temperature medium outlet 82 of the heat exchanger 8 is connected to the reaction gas inlet of the third-stage reformer 13.

[0018] The reaction gas outlet of the three-stage converter 13 is connected to the heating medium inlet 71 of the hot and cold heat exchanger 7, and the heating medium outlet 72 of the hot and cold heat exchanger 7 is connected to the flue gas inlet of the secondary economizer 32. In this embodiment, the flue gas outlet of the secondary economizer 32 is connected to the inlet of the first absorption tower 9, the outlet of the first absorption tower 9 is connected to the heating medium inlet 73 of the hot and cold heat exchanger 7, the heating medium outlet 74 of the hot and cold heat exchanger 7 is connected to the heating medium inlet 83 of the hot and cold heat exchanger 8, and the heating medium outlet 84 of the hot and cold heat exchanger 8 is connected to the reaction gas inlet of the four-stage converter 14.

[0019] The reaction gas outlet of the four-stage converter 14 is connected to the flue gas inlet of the three-stage economizer 33, the flue gas outlet of the three-stage economizer 33 is connected to the reaction gas inlet of the five-stage converter 15, and the reaction gas outlet of the five-stage converter 15 is connected to the flue gas inlet of the first-stage economizer 31. In this embodiment, the flue gas outlet of the first-stage economizer 31 is connected to the inlet of the second absorption tower 34, and the outlet of the second absorption tower 34 is connected to the chimney 35.

[0020] The high-temperature stage heat exchange tube group 311 and the low-temperature stage heat exchange tube group 312 are arranged sequentially in the direction of gas flow inside the first-stage economizer 31.

[0021] The inlet of the low-temperature stage heat exchanger tube assembly 312 is connected to the external feedwater pipe 10, and the outlet of the low-temperature stage heat exchanger tube assembly 312 is connected to the inlet of the secondary economizer 32. The outlet of the secondary economizer 32 is connected to the inlet of the high-temperature stage heat exchanger tube assembly 311 in the primary economizer 31. The outlet of the high-temperature stage heat exchanger tube assembly 311 is connected to the inlet of the tertiary economizer 33, and the outlet of the tertiary economizer 33 is connected to the steam drum 41. The steam outlet of the steam drum 41 is connected to the steam inlet of the low-temperature superheater 5, and the steam outlet of the low-temperature superheater 5 is connected to the steam inlet of the high-temperature superheater 6. In this embodiment, a water spray desuperheater 61 is provided at the steam inlet of the high-temperature superheater 6, and the water spray desuperheater 61 is connected to the external feedwater pipe 10.

[0022] The working principle is as follows: Flue gas flow: The sulfur incinerator 2 produces reactive gas, with a temperature reaching approximately 1000℃. The main component of the reactive gas is sulfur dioxide. The reactive gas enters the low-temperature superheater 5 via the fire-tube boiler 4. The temperature at the flue gas outlet of the low-temperature superheater 5 is approximately 420℃, which meets the temperature requirements of the catalytic reaction in the first-stage converter 11. The catalytic reaction in each stage converter is exothermic; therefore, the gas temperature at the outlet of the reactive gas in each stage converter is significantly higher than the temperature required for the catalytic reaction within the converter.

[0023] The temperature of the reactant gas at the outlet of the first-stage reformer 11 reaches approximately 600°C. This reactant gas then enters the high-temperature superheater 6, where the flue gas outlet temperature is approximately 440°C, meeting the temperature requirements for the catalytic reaction in the second-stage reformer 12. The reactant gas undergoes a catalytic reaction in the second-stage reformer 12, where the outlet temperature reaches approximately 520°C. The reactant gas from the outlet of the second-stage reformer 12 then enters the heat exchanger 8 via the high-temperature medium inlet 81. The high-temperature medium outlet 82 of the heat exchanger 8 has a temperature of approximately 400°C. The gas output from the high-temperature medium outlet 82 of the heat exchanger 8 then enters the third-stage reformer 13 for further catalytic reaction.

[0024] The reaction gas that completes the catalytic reaction in the three-stage converter 13 enters the heat exchanger 7 as a heating medium. The gas that has released heat energy enters the secondary economizer 32 from the heat exchanger 7, and then enters the first absorption tower 9 from the flue gas outlet of the secondary economizer 32. The first absorption tower 9 absorbs sulfur trioxide in the reaction gas, and the unconverted sulfur dioxide gas enters the heat exchanger 7 from the outlet of the first absorption tower 9 through the inlet 73 of the heat exchanger 7.

[0025] The gas temperature at the outlet of the first absorption tower 9 is around 80℃. The reaction gas output from the first absorption tower 9 is heated sequentially in the cold heat exchanger 7 and the hot heat exchanger 8 to reach the reaction temperature of 400℃ required by the four-stage converter 14, and then enters the four-stage converter 14 for further conversion. The gas that has completed conversion in the four-stage converter 14 enters the three-stage economizer 33, and the gas from the flue gas outlet of the three-stage economizer 33 enters the five-stage converter 15 for the final conversion.

[0026] The gas that has completed the catalytic reaction in the five-stage converter 15 enters the first-stage economizer 31. The flue gas outlet temperature of the five-stage converter 15 is 425℃. The gas in the first-stage economizer 31 passes sequentially through the high-temperature stage heat exchange tube group 311 and the low-temperature stage heat exchange tube group 312 and is then output from the flue gas outlet of the first-stage economizer 31 to the second absorption tower 34 for absorption. After the second absorption tower 34 absorbs sulfur trioxide, the remaining tail gas is directly discharged through the chimney 35.

Claims

1. A high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant, the sulfuric acid production plant including a sulfur incinerator and a converter, wherein the converter is provided with a first-stage converter, a second-stage converter, a third-stage converter, a fourth-stage converter, and a fifth-stage converter arranged sequentially from bottom to top, and the high-temperature and high-pressure waste heat recovery system includes: The boiler is a fire-tube boiler with a steam drum at the top, a superheater, and an economizer. The reaction gas outlet of the sulfur-burning furnace is connected to the flue gas inlet of the fire-tube boiler. The boiler is characterized by: the superheater including a low-temperature superheater and a high-temperature superheater; the economizer including a primary economizer, a secondary economizer, and a tertiary economizer; the flue gas outlet of the fire-tube boiler is connected to the flue gas inlet of the low-temperature superheater; the flue gas outlet of the low-temperature superheater is connected to the reaction gas inlet of the first-stage reformer; the reaction gas outlet of the first-stage reformer is connected to the flue gas inlet of the high-temperature superheater; the flue gas outlet of the high-temperature superheater is connected to the reaction gas inlet of the second-stage reformer; the reaction gas outlet of the second-stage reformer is connected to the high-temperature medium inlet of the heat exchanger; the high-temperature medium outlet of the heat exchanger is connected to the reaction gas inlet of the third-stage reformer; the reaction gas outlet of the third-stage reformer is connected to the heating medium inlet of the heat exchanger; the heating medium outlet of the heat exchanger is connected to the flue gas inlet of the secondary economizer; the reaction gas outlet of the fourth-stage reformer is connected to the flue gas inlet of the tertiary economizer; and the flue gas outlet of the tertiary economizer is connected to... The reactant gas inlet of the five-stage converter and the reactant gas outlet of the five-stage converter are connected to the flue gas inlet of the first-stage economizer. In the first-stage economizer, high-temperature stage heat exchanger tube groups and low-temperature stage heat exchanger tube groups are sequentially arranged in the direction of gas flow. The inlet of the low-temperature stage heat exchanger tube group is connected to the external feedwater pipe, and the outlet of the low-temperature stage heat exchanger tube group is connected to the inlet of the second-stage economizer. The outlet of the second-stage economizer is connected to the inlet of the high-temperature stage heat exchanger tube group in the first-stage economizer, and the outlet of the high-temperature stage heat exchanger tube group is connected to the inlet of the third-stage economizer. The outlet of the third-stage economizer is connected to the steam drum, and the steam outlet of the steam drum is connected to the steam inlet of the low-temperature superheater. The steam outlet of the low-temperature superheater is connected to the steam inlet of the high-temperature superheater. The flue gas outlet of the second-stage economizer is connected to the inlet of the first absorption tower, and the outlet of the first absorption tower is connected to the inlet of the medium to be heated in the cold-hot heat exchanger. The outlet of the medium to be heated in the cold-hot heat exchanger is connected to the inlet of the medium to be heated in the hot-hot heat exchanger, and the outlet of the medium to be heated in the hot-hot heat exchanger is connected to the reactant gas inlet of the fourth-stage converter.

2. The high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant according to claim 1, characterized in that: A water spray desuperheater is installed at the steam inlet of the high-temperature superheater, and the water spray desuperheater is connected to an external water supply pipe.

3. A high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant according to claim 1, characterized in that: Fire-tube boilers employ flexible thin tube sheet structures.

4. A high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant according to claim 1, characterized in that: The heat exchange tubes in the superheater and economizer are all finned tubes.

5. A high-temperature and high-pressure waste heat recovery device for a sulfuric acid production plant according to claim 1, 2, 3, or 4, characterized in that: The flue gas outlet of the primary economizer is connected to the inlet of the second absorption tower, and the outlet of the second absorption tower is connected to the chimney.

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