A pure oxygen combustion waste gas desulfurization and white smoke elimination treatment process

Abstract

This application belongs to the technical field of waste gas treatment, and discloses a desulfurization and white smoke elimination treatment process for pure oxygen combustion waste gas, which includes the following steps: The high-humidity, dust-containing, and high-temperature flue gas at 1200-1500°C discharged from the kiln furnace flue is subjected to multi-stage waste heat recovery, and then the flue gas temperature is reduced to 80-90°C. The cooled flue gas is introduced into a desulfurization spray tower and treated by a double-alkali desulfurization process. Subsequently, after passing through a demisting and dehydration chimney, waste gas desulfurization, dust removal, and dehumidification are achieved, and the discharge meets the standards. The treatment process in this application provides an ideal waste heat recovery solution, solves the problem of equipment corrosion caused by high-humidity and high-sulfur flue gas, solves the problem of equipment blockage during the double-alkali desulfurization process, and realizes the maximum resource utilization; the invention has high resource utilization rate, good economic benefits, simple structure, and is more suitable for industrial promotion and application.

Description

Technical Field

[0001] The present invention relates to the technical field of waste gas treatment, and particularly to a desulfurization and de - whitening treatment process for pure - oxygen combustion waste gas. Background Technique

[0002] During the glass melting process, sodium sulfate is generally introduced as a high - temperature clarifying agent. Sodium sulfate decomposes at high temperature to produce sulfur dioxide which enters the flue gas. The main products of natural gas - pure - oxygen combustion contain 2 / 3 water vapor and 1 / 3 carbon dioxide. With the superposition of these two conditions, in a pure - oxygen combustion glass furnace, under standard conditions, the water vapor in the flue gas condenses, and the sulfur dioxide concentration increases by 3 times, reaching 2000 - 5000mg / Nm 3 . The flue gas of the glass furnace also carries some oxide particles, such as solid impurities like SiO2, Na2CO3, CaCO3, etc. Therefore, the waste gas generated by the pure - oxygen combustion glass furnace has the characteristics of high humidity, high concentration, and high oxidability, which brings difficulties to flue gas desulfurization.

[0003] Waste gas treatment desulfurization technologies are generally divided into three categories: dry method, semi - dry method, and wet method desulfurization. Among them, wet flue gas desulfurization has higher efficiency and simpler operation than the dry method and semi - dry method. Therefore, the wet flue gas desulfurization treatment plan is preferred. In the wet desulfurization plan, the double - alkali method desulfurization process is developed on the basis of the limestone - gypsum method, which overcomes the defect of easy scaling in the pipeline of the limestone - gypsum method. However, the corrosion of equipment by high - humidity flue gas is a difficult problem, and there are also many deficiencies in using the double - alkali method for desulfurization of highly oxidizing gases.

[0004] In order to overcome the deficiencies of the flue gas desulfurization technology for high - temperature, high - humidity, high - concentration, and high - oxidation flue gas, the present invention provides a new type of flue gas desulfurization technology and process control plan. Using this process, the flue gas is first cooled and dust - removed sufficiently, the high - temperature flue gas is cooled from 1450°C to 80°C, and the waste heat is fully recovered and utilized. Then the flue gas is desulfurized, greatly reducing the treatment difficulty of high - sulfur flue gas, reducing the dosage of desulfurization agents, reducing equipment corrosion, solving the problem of pipeline blockage, realizing continuous operation of the equipment, and also achieving the "de - whitening" effect after flue gas treatment. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a desulfurization and de - whitening treatment process for pure - oxygen combustion waste gas.

[0006] The above technical object of the present invention is achieved through the following technical solutions: A desulfurization and de - whitening treatment process for pure - oxygen combustion waste gas, the treatment process includes the following steps:

[0007] The high-humidity, dust-containing, high-temperature flue gas at 1200 - 1500 °C discharged from the kiln flue is cooled to 80 - 90 °C after multi-stage waste heat recovery. The cooled flue gas is introduced into a desulfurization spray tower and treated using a dual-alkali desulfurization process. Subsequently, after passing through a demisting and dehydration chimney, waste gas desulfurization, dust removal, and dehumidification are achieved, and the emission meets the standards.

[0008] Furthermore, the multi-stage waste heat recovery steps for the high-temperature flue gas are as follows:

[0009] S1. The high-humidity, dust-containing, high-temperature flue gas at 1200 - 1500 °C first passes through a primary high-temperature waste heat exchanger, and the flue gas temperature is reduced to 480 - 500 °C;

[0010] Among them, the refrigerant medium is normal-temperature air, which is heated to 290 - 300 °C through the primary high-temperature waste heat exchanger for subsequent product drying process;

[0011] S2. The medium-high temperature flue gas at 480 - 500 °C undergoes gas-gas heat exchange through a secondary shell-and-tube waste heat exchanger, so that the flue gas temperature is reduced to 290 - 300 °C;

[0012] Among them, the refrigerant medium is air at 125 - 130 °C, and the air temperature is heated to 260 - 270 °C through the secondary shell-and-tube waste heat exchanger, which is also used for the subsequent product drying process;

[0013] S3. The flue gas cooled to 290 - 300 °C enters a tertiary gravity heat pipe exchanger, so that the flue gas temperature is reduced to 175 - 180 °C;

[0014] Among them, the refrigerant medium is normal-temperature air, which is heated to 125 - 130 °C through the tertiary gravity heat pipe exchanger and serves as the refrigerant medium for the secondary shell-and-tube waste heat exchanger;

[0015] S4. The flue gas cooled to 175 - 180 °C enters a fluoroplastic heat exchanger through a draft fan for gas-water heat exchange, so that the flue gas temperature is reduced to 80 - 90 °C;

[0016] Among them, the refrigerant medium is water at 60 °C. The refrigerant medium passes through the fluoroplastic heat exchanger, and the temperature rises to 80 - 85 °C, which is used for producing hot water.

[0017] By adopting the above technical solutions, the treatment process provides an ideal waste heat recovery solution, solves the problem of equipment corrosion caused by high-humidity and high-sulfur flue gas, solves the problem of equipment blockage during the dual-alkali desulfurization process, and realizes the maximum resource utilization.

[0018] Furthermore, spray nozzles are provided inside the spray tower, and the spray nozzles are divided into circulating desulfurization liquid spray nozzles and alkali liquid spray nozzles;

[0019] Among them, the circulating desulfurization liquid nozzle is a single-fluid nozzle, which is divided into volute type and swirl type nozzle. The absorption liquid in the circulating water pool is pumped into the spray tower through the circulating liquid pump, and fully contacts with the flue gas to achieve the purpose of desulfurization;

[0020] The alkali solution spray head adopts a dual-fluid structure, and the sodium hydroxide solution in the alkali solution tank is replenished into the spray tower through a centrifugal pump, which is beneficial to reduce the alkalinity of the circulation system and thus avoid the problem of system blockage.

[0021] By adopting the above technical solution, the absorption liquid in the circulating water pool is pumped into the spray tower through the circulating liquid pump, and fully contacts with the flue gas to achieve the purpose of desulfurization. The alkali solution is directly added to the spray tower to supplement the sulfite ions lost in the double alkali desulfurization system, which is conducive to reducing the alkalinity of the circulation system, thereby avoiding the problem of system blockage.

[0022] Furthermore, the sulfite in the circulating water pool needs to be continuously replaced by lime through chemical reaction. The replacement process is completed by the lime silo, material scale, primary reaction tank, secondary reaction tank, vertical flow sedimentation tank and mud press. The quicklime is stored in the lime silo, weighed by the material scale, stirred and mixed with a part of the circulating liquid in the primary reaction tank to produce a chemical reaction, and then continues to enter the secondary reaction tank for chemical reaction. The sodium hydroxide solution replaced after the reaction flows back to the circulating water pool through the upper part of the secondary reaction tank, and the desulfurized gypsum produced by the precipitation is discharged from the body through the mud press and used as a building material.

[0023] Furthermore, each connecting ring is designed with temperature and pressure detection, and the circulating water pool is designed with pH value detection function, making the system feasible for process control.

[0024] Furthermore, the first-stage high-temperature waste heat exchanger is made of high-temperature resistant alloy material.

[0025] By adopting the above technical solution, the first-stage high-temperature waste heat exchanger is made of high-temperature resistant alloy material and has high creep resistance.

[0026] Furthermore, the two-stage tube-in-tube waste heat exchanger is made of metal alloy material, and vertical tube bundle heat transfer tubes are used inside.

[0027] By adopting the above technical solution, the structure is conducive to the precipitation of smoke dust, the sulfur-containing solid oxides are removed from the system, and the smoke dust content of the system is reduced.

[0028] Furthermore, the three-stage gravity heat pipe heat exchanger uses corrosion-resistant ND steel as the main material. The interior of the three-stage gravity heat pipe heat exchanger is composed of rows of gravity heat pipes, and a dust collection bin is arranged at the bottom.

[0029] By adopting the above technical solutions, it is beneficial to the sedimentation of soot, and sulfur-containing solid oxides are also excluded from the system, reducing the subsequent disposal pressure. During the entire pretreatment process, the maximum utilization of waste heat recovery resources is achieved, and at the same time, the load of subsequent desulfurization and dust removal is reduced.

[0030] Furthermore, the fluoroplastic heat exchanger is composed of a fiberglass body and fluoroplastic pipes.

[0031] By adopting the above technical solutions, the fluoroplastic heat exchanger is composed of a fiberglass body and fluoroplastic pipes, has a powerful self-cleaning function and excellent corrosion resistance, and reduces the dust content in the flue gas.

[0032] In summary, the present invention has the following beneficial effects:

[0033] 1. In the present application, the treatment process provides an ideal waste heat recovery solution, solves the problems of equipment corrosion caused by high-humidity and high-sulfur flue gas, solves the problem of equipment blockage during the double-alkali method desulfurization process, and realizes the maximum resource utilization; the present invention has high resource utilization rate, good economic benefits, simple structure, and is more suitable for industrial promotion and application;

[0034] 2. In the present application, the absorption liquid in the circulation water tank is pumped into the spray tower by the circulation liquid pump to fully contact with the flue gas to achieve the desulfurization purpose. The alkali liquor is directly added to the spray tower as a supplement to the sulfite ions lost in the double-alkali method desulfurization system, which is beneficial to reducing the alkalinity of the circulation system, thereby avoiding the problem of system blockage;

[0035] 3. In the present application, through the combined use of a secondary shell-and-tube waste heat exchanger and a tertiary gravity heat pipe exchanger, the lowest temperature point of the secondary shell-and-tube waste heat exchanger is controlled at about 215 °C, far from the flue gas condensation point, avoiding the corrosion of the pipes of the shell-and-tube heat exchanger. At the same time, taking advantage of the anti-low-temperature corrosion of the tertiary gravity heat pipe exchanger, the flue gas temperature is lowered to close to the flue gas condensation point, maximizing the recovery of waste heat and improving the waste heat utilization efficiency to meet the demand for hot air volume in subsequent product drying. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the overall structural schematic diagram of an embodiment of the present invention.

[0037] In the figure: 1. Primary high-temperature waste heat exchanger; 2. Secondary shell-and-tube waste heat exchanger; 3. Tertiary gravity heat pipe exchanger; 4. Induced draft fan; 5. Fluoroplastic heat exchanger; 6. Spray tower; 7. Demisting and dehydrating chimney; 8. Circulation water tank; 9. Lime silo; 10. Weighing scale; 11. Primary reaction tank; 12. Secondary reaction tank; 13. Vertical flow sedimentation tank; 14. Sludge press; 15. Alkali liquor tank; 16. Circulation liquid pump. DETAILED DESCRIPTION OF THE INVENTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application; obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0039] Embodiment 1

[0040] As Figure 1 shown, the embodiments of the present application disclose a desulfurization and white smoke elimination treatment process for pure oxygen combustion waste gas, including the following steps:

[0041] S1. The high-humidity, dust-containing, and high-temperature flue gas at 1200 °C generated by pure oxygen combustion discharged from the kiln furnace flue is first passed through a primary high-temperature waste heat exchanger 1 made of a high-temperature resistant alloy material to reduce the flue gas temperature to 480 °C. The refrigerant medium for cooling is normal-temperature air, which is heated from normal temperature to 290 °C for subsequent product drying process;

[0042] S2. The medium-high temperature flue gas at 480 °C is subjected to gas-gas heat exchange through a secondary shell-and-tube waste heat exchanger 2 made of a metal alloy material, so that the flue gas temperature is reduced to 290 °C. The internal part of the secondary shell-and-tube waste heat exchanger 2 adopts vertical tube bundles as heat transfer tubes, and the refrigerant medium is air at 125 °C. The air temperature is heated to 260 °C through the secondary shell-and-tube waste heat exchanger 2 and used for subsequent product drying process;

[0043] S3. The flue gas cooled to 290 °C enters a tertiary gravity heat pipe exchanger 3, so that the flue gas temperature is reduced to 175 °C. The tertiary gravity heat pipe exchanger 3 uses corrosion-resistant ND steel as the main material. The internal part of the tertiary gravity heat pipe exchanger 3 consists of rows of gravity heat pipes, and a dust hopper is arranged at the lower part to precipitate and separate out part of the soot in the flue gas;

[0044] The refrigerant medium is normal-temperature air, which is heated to air at 125 °C through the tertiary gravity heat pipe exchanger 3 and used as the refrigerant medium of the secondary shell-and-tube waste heat exchanger 2. The flue gas outlet temperature of the tertiary gravity heat pipe exchanger 3 is accurately controlled at 15 °C above the flue gas condensation point to prevent the occurrence of flue gas condensation and corrosion phenomena;

[0045] S4. The flue gas cooled to 175 °C enters a fluoroplastic heat exchanger 5 through a draft fan 4 for gas-water heat exchange, so that the flue gas temperature is reduced to 80 °C;

[0046] The refrigerant is water at 60°C. The refrigerant passes through the fluoroplastic heat exchanger 5, and the temperature is raised to 80°C for the production of hot water. The fluoroplastic heat exchanger 5 is composed of a glass fiber reinforced plastic body and a fluoroplastic tube, which precipitates the high-humidity water vapor in the flue gas in the form of condensed water, reducing the flue gas volume by more than 40%, thereby reducing the load of the exhaust gas treatment desulfurization system. At the same time, the condensed water captures the dust in the flue gas during the precipitation process. The fluoroplastic heat exchanger 5 has a strong self-cleaning function, which reduces the dust content of the flue gas.

[0047] S5, the low-temperature flue gas coming out of the fluoroplastic heat exchanger 5 continues to enter the spray tower 6 for washing and desulfurization, and finally is discharged into the atmosphere after passing through the demisting and dehydrating chimney 7;

[0048] Among them, the spray tower 6 is equipped with a circulating water pool 8, an alkali liquid tank 15 and a circulating liquid pump 16. The circulating water pool 8 is used to store sulfur dioxide absorption liquid, the alkali liquid tank 15 is used to supplement the alkali liquid in the double alkali desulfurization process, and the circulating liquid pump 16 provides power for the spray tower 6 spraying operation. A spray head is arranged inside the spray tower 6, and the spray head is divided into a circulating desulfurization liquid nozzle and an alkali liquid spray head. The circulating desulfurization liquid nozzle is a single-fluid nozzle, which is further divided into a volute type and a swirl type nozzle. The absorption liquid in the circulating water pool 8 is pumped into the spray tower 6 through the circulating liquid pump 16, and is fully contacted with the flue gas to achieve the purpose of desulfurization. The alkali liquid spray head adopts a dual-fluid structure, and the sodium hydroxide solution in the alkali liquid tank 15 is supplemented into the spray tower 6 through a centrifugal pump, which is beneficial to reduce the alkalinity of the circulation system, thereby avoiding the problem of system blockage;

[0049] The sulfite in the circulating water pool 8 needs to be continuously replaced by lime through chemical reaction. The replacement process is completed by the lime bin 9, the material scale 10, the primary reaction tank 11, the secondary reaction tank 12, the vertical flow sedimentation tank 13, and the mud press 14. The quicklime is stored in the lime bin 9, weighed by the material scale 10, stirred and mixed with a part of the circulating liquid in the primary reaction tank 11 to produce a chemical reaction, and then continues to enter the secondary reaction tank 12 for chemical reaction. After the reaction, the sodium hydroxide solution replaced is refluxed to the circulating water pool 8 through the upper part of the secondary reaction tank 12, and the desulfurized gypsum produced by the precipitation is discharged from the body through the mud press 14 and used as a building material.

[0050] In this embodiment, each connecting ring is designed with temperature and pressure detection, and the circulating water pool 8 is designed with a pH value detection function, so that the system has the feasibility of process control.

[0051] The use principle of a pure oxygen combustion waste gas desulfurization and deoxidation treatment process in this embodiment is:

[0052] This treatment process provides an ideal waste heat recovery solution, solves the problems of equipment corrosion caused by high-humidity and high-sulfur flue gas, solves the problem of equipment blockage during the double-alkali flue gas desulfurization process, and realizes the maximum resource utilization; the invention has high resource utilization rate, good economic benefits, and a simple structure, and is more suitable for industrial promotion and application. The absorption liquid in the circulation water tank 8 is pumped into the spray tower 6 by the circulation liquid pump 16 to fully contact with the flue gas to achieve the purpose of desulfurization. The alkali liquid is directly added to the spray tower 6 as a supplement to the sulfite ions lost in the double-alkali desulfurization system, which is beneficial to reducing the alkalinity of the circulation system and thus avoiding the problem of system blockage.

[0053] Through the combined use of the secondary shell-and-tube waste heat exchanger 2 and the tertiary gravity heat pipe exchanger 3, the lowest temperature point of the secondary shell-and-tube waste heat exchanger 2 is controlled at about 215°C, far from the flue gas condensation point, avoiding the corrosion of the pipes of the shell-and-tube heat exchanger. At the same time, taking advantage of the anti-low-temperature corrosion of the tertiary gravity heat pipe exchanger 3, the flue gas temperature is lowered to close to the flue gas condensation point, maximizing the recovery of waste heat and wind, improving the waste heat utilization efficiency, and meeting the demand for hot air volume in the subsequent product drying.

[0054] Example 2

[0055] As Figure 1 shown, the embodiment of the present application discloses a pure oxygen combustion waste gas desulfurization and dewhitening treatment process, including the following steps:

[0056] S1. The high-humidity, dust-containing, and high-temperature flue gas generated by pure oxygen combustion discharged from the kiln furnace flue is first passed through the primary high-temperature waste heat exchanger 1 made of high-temperature resistant alloy materials to reduce the flue gas temperature to 500°C. The refrigerant medium for cooling is normal-temperature air, which is heated from normal temperature to 300°C for the subsequent product drying process.

[0057] S2. The medium-high temperature flue gas at 500°C is subjected to gas-gas heat exchange through the secondary shell-and-tube waste heat exchanger 2 made of metal alloy materials, so that the flue gas temperature is reduced to 300°C. The internal of the secondary shell-and-tube waste heat exchanger 2 adopts vertical tube bundle heat transfer tubes, and the refrigerant medium is air at 130°C. The air temperature is heated to 270°C through the secondary shell-and-tube waste heat exchanger 2 and used for the subsequent product drying process.

[0058] S3. The flue gas cooled to 300°C enters the tertiary gravity heat pipe exchanger 3, so that the flue gas temperature is reduced to 180°C. The tertiary gravity heat pipe exchanger 3 uses corrosion-resistant ND steel as the main material. The internal of the tertiary gravity heat pipe exchanger 3 is composed of rows of gravity heat pipes, and a dust hopper is arranged at the lower part to precipitate and separate part of the dust in the flue gas.

[0059] The refrigerant medium is normal-temperature air, which is heated to 130°C air by the three-stage gravity heat pipe heat exchanger 3 and serves as the refrigerant medium of the secondary shell-and-tube waste heat exchanger 2. The flue gas outlet temperature of the three-stage gravity heat pipe heat exchanger 3 is precisely controlled to be 15°C above the flue gas condensation point to prevent flue gas condensation and corrosion;

[0060] S4. The flue gas cooled to 180°C enters the fluoroplastic heat exchanger 5 through the induced draft fan 4 for gas-water heat exchange, reducing the flue gas temperature to 90°C;

[0061] The refrigerant medium is water at 60°C. The refrigerant medium passes through the fluoroplastic heat exchanger 5 and its temperature rises to 85°C for hot water production. The fluoroplastic heat exchanger 5 consists of a fiberglass body and fluoroplastic tubes, which separates the high-humidity water vapor in the flue gas in the form of condensate, reducing the flue gas volume by more than 40% and reducing the load of the waste gas treatment desulfurization system. At the same time, during the precipitation of the condensate, the dust in the flue gas is captured together. The fluoroplastic heat exchanger 5 has a powerful self-cleaning function, reducing the dust content of the flue gas;

[0062] S5. The low-temperature flue gas coming out of the fluoroplastic heat exchanger 5 continues to enter the spray tower 6 for washing and desulfurization, and finally is discharged into the atmospheric environment through the demisting and dehydration chimney 7;

[0063] Among them, the spray tower 6 is equipped with a circulation water tank 8, an alkali liquid tank 15 and a circulation liquid pump 16. The circulation water tank 8 is used for storing the sulfur dioxide absorption liquid, the alkali liquid tank 15 is used for supplementing the alkali liquid in the double-alkali method desulfurization, and the circulation liquid pump 16 provides the power for the spraying operation of the spray tower 6. The spray tower 6 is internally provided with spray heads, which are divided into circulating desulfurization liquid spray heads and alkali liquid spray heads. The circulating desulfurization liquid spray heads are single-fluid spray heads, which are further divided into volute type and swirl type spray heads. The absorption liquid in the circulation water tank 8 is pumped into the spray tower 6 through the circulation liquid pump 16 to fully contact with the flue gas to achieve the desulfurization purpose. The alkali liquid spray heads adopt a double-fluid structure, and the sodium hydroxide solution in the alkali liquid tank 15 is supplemented into the spray tower 6 through a centrifugal pump, which is beneficial to reducing the alkalinity of the circulation system and thus avoiding the problem of system blockage;

[0064] The sulfite in the circulation water tank 8 needs to be continuously replaced through chemical reactions with lime. The replacement process is jointly completed by the lime bin 9, the weighing scale 10, the first-stage reaction tank 11, the second-stage reaction tank 12, the upflow sedimentation tank 13 and the sludge press 14. Quicklime is stored in the lime bin 9, weighed by the weighing scale 10, stirred and mixed with a part of the circulating liquid in the first-stage reaction tank 11 to produce a chemical reaction, and then continues to enter the second-stage reaction tank 12 for chemical reaction. The sodium hydroxide solution replaced after the reaction flows back to the circulation water tank 8 from the upper part of the second-stage reaction tank 12. The desulfurization gypsum produced by precipitation is discharged out of the body through the sludge press 14 and used as building materials.

[0065] In this embodiment, each adapter ring is designed with temperature and pressure detection, and the circulation water tank 8 is designed with a pH value detection function, enabling the system to have the feasibility of process control.

[0066] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A desulfurization and white smoke elimination treatment process for pure oxygen combustion exhaust gas, characterized in that, The treatment process includes the following steps: The high-humidity, dust-containing, high-temperature flue gas at 1200 - 1500 °C discharged from the kiln flue is subjected to multi-stage waste heat recovery, after which the flue gas temperature is reduced to 80 - 90 °C. The cooled flue gas is introduced into the desulfurization spray tower (6), and is treated using the double-alkali desulfurization process. Subsequently, after passing through the demisting and dehydration chimney (7), waste gas desulfurization, dust removal, and dehumidification are achieved, and the emissions meet the standards; The steps of multi-stage waste heat recovery of the high-temperature flue gas are as follows: S1. The high-humidity, dust-containing, high-temperature flue gas at 1200 - 1500 °C first passes through the primary high-temperature waste heat exchanger (1), reducing the flue gas temperature to 480 - 500 °C; Among them, the refrigerant medium is normal-temperature air, which is heated to 290 - 300 °C through the primary high-temperature waste heat exchanger (1) for use in the subsequent product drying process; S2. The medium-high temperature flue gas at 480 - 500 °C undergoes gas-gas heat exchange through the secondary shell-and-tube waste heat exchanger (2), reducing the flue gas temperature to 290 - 300 °C; Among them, the refrigerant medium is air at 125 - 130 °C, and the air temperature is heated to 260 - 270 °C through the secondary shell-and-tube waste heat exchanger (2), also for use in the subsequent product drying process; S3. The flue gas cooled to 290 - 300 °C enters the tertiary gravity heat pipe exchanger (3), reducing the flue gas temperature to 175 - 180 °C; Among them, the refrigerant medium is normal-temperature air, which is heated to 125 - 130 °C through the tertiary gravity heat pipe exchanger (3) and serves as the refrigerant medium for the secondary shell-and-tube waste heat exchanger (2); S4. The flue gas cooled to 175 - 180 °C enters the fluoroplastic heat exchanger (5) through the induced draft fan (4) for gas-water heat exchange, reducing the flue gas temperature to 80 - 90 °C; Among them, the refrigerant medium is water at 60 °C. The refrigerant medium passes through the fluoroplastic heat exchanger (5), and the temperature rises to 80 - 85 °C for use in producing hot water.

2. A pure oxygen combustion waste gas desulfurization and de - whitening treatment process according to claim 1, characterized in that: The spray tower (6) is internally equipped with spray nozzles, which are divided into circulating desulfurization liquid spray nozzles and alkali liquid spray nozzles; Among them, the circulating desulfurization liquid spray nozzles are single-fluid spray nozzles, which are further divided into volute type and swirl type spray nozzles. The absorption liquid in the circulating water tank (8) is pumped into the spray tower (6) through the circulating liquid pump (16) to fully contact the flue gas to achieve the desulfurization purpose; The alkali liquid spray nozzles adopt a double-fluid structure, and the sodium hydroxide solution in the alkali liquid tank (15) is supplemented into the spray tower (6) through the centrifugal pump, which is beneficial to reducing the alkalinity of the circulation system, thus avoiding the problem of system blockage.

3. A pure oxygen combustion waste gas desulfurization and de - whitening treatment process according to claim 2, characterized in that: The sulfite in the circulating water pool (8) needs to be continuously replaced by lime for chemical reaction. The replacement process is completed by the lime bin (9), the material scale (10), the primary reaction tank (11), the secondary reaction tank (12), the vertical flow sedimentation tank (13) and the mud press (14). The quicklime is stored in the lime bin (9), weighed by the material scale (10), stirred and mixed with a part of the circulating liquid in the primary reaction tank (11) to produce a chemical reaction, and then continues to enter the secondary reaction tank (12) for chemical reaction. After the reaction, the sodium hydroxide solution replaced is returned to the circulating water pool (8) through the upper part of the secondary reaction tank (12), and the desulfurized gypsum produced by the precipitation is discharged from the body through the mud press (14) and used as a building material.

4. A pure oxygen combustion waste gas desulfurization and de - whitening treatment process according to claim 3, characterized in that: Each connecting ring is designed with temperature and pressure detection, and the circulating water pool (8) is designed with a pH value detection function, so that the system has the feasibility of process control.

5. A pure oxygen combustion waste gas desulfurization and white smoke elimination treatment process according to claim 1, characterized in that: The first-stage high-temperature waste heat exchanger (1) is made of high-temperature resistant alloy material.

6. A pure oxygen combustion waste gas desulfurization and white smoke elimination treatment process according to claim 1, characterized in that: The two-stage tube-in-tube waste heat exchanger (2) is made of metal alloy material and has vertical tube bundle heat transfer tubes inside.

7. A pure oxygen combustion waste gas desulfurization and white smoke elimination treatment process according to claim 1, characterized in that: The three-stage gravity heat pipe heat exchanger (3) uses corrosion-resistant ND steel as the main material. The interior of the three-stage gravity heat pipe heat exchanger (3) is composed of rows of gravity heat pipes, and a dust collection bin is arranged at the bottom.

8. A pure oxygen combustion waste gas desulfurization and white smoke elimination treatment process according to claim 1, characterized in that: The fluoroplastic heat exchanger (5) is composed of a glass fiber reinforced plastic body and a fluoroplastic tube.

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