Waste sulfuric acid pyrolysis to prepare sodium sulfite system

Abstract

The utility model discloses a system for preparing sodium sulfite by pyrolysis of waste sulfuric acid, comprising a waste sulfuric acid pyrolysis recovery module, a furnace gas purification module, a dry absorption reaction module and a condensation module which are sequentially connected; the waste sulfuric acid pyrolysis recovery module comprises a waste sulfuric acid storage tank, a buffer tank, a cracking furnace and a waste heat boiler which are sequentially connected, a natural gas input pipe is connected to the cracking furnace, an atomizing spray gun is also connected in the cracking furnace, the discharge end of the buffer tank is connected to the atomizing spray gun, the output end of the cracking furnace is connected to the waste heat boiler for heat exchange, the condensation module comprises a buffer barrel, a condensation crystallization group and a filter press which are sequentially connected, the liquid pipe outlets of the primary reaction tower and the secondary reaction tower are extended to the buffer barrel, and a solution adding port is also provided in the buffer barrel, and the solution adding port is used to transport NaOH solution and lithium aluminum hydride reducing agent. The advantages of the utility model compared with the prior art are that waste sulfuric acid can be recovered to prepare sodium sulfite, and the environmental ecological harm of waste sulfuric acid is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of waste sulfuric acid recovery and reuse, in particular to a system for preparing sodium sulfite by pyrolysis of waste sulfuric acid. Background Art

[0002] Sodium sulfite, also known as sulfur oxide, has a molecular formula of Na2SO3 and a molecular weight of 126.04. It is a colorless hexagonal prism crystal or white crystalline powder, and has two types: anhydrous and heptahydrate. The traditional production method of sodium sulfite is the sulfur dioxide-soda method, which burns sulfur to generate sulfur dioxide gas, which then reacts with soda ash and caustic soda to generate sodium sulfite, which is then neutralized, concentrated and dried to obtain the finished product.

[0003] With the rapid development of my country's national economy, the demand for basic chemicals such as sulfuric acid in industrial and agricultural production has increased year by year. In this process, a large amount of waste sulfuric acid will be generated. If it is not properly handled, it will cause great harm to the ecological environment. Utility Model Content

[0004] 1. Problems to be solved

[0005] The technical problem to be solved by the utility model is to overcome the above technical defects and provide a system for preparing sodium sulfite by pyrolyzing waste sulfuric acid, which can recycle waste sulfuric acid to prepare sodium sulfite and reduce the environmental ecological harm of waste sulfuric acid.

[0006] (II) Technical solution

[0007] In order to solve the above technical problems, the technical solution provided by the utility model is as follows: a system for preparing sodium sulfite by pyrolysis of waste sulfuric acid, comprising a waste sulfuric acid pyrolysis recovery module, a furnace gas purification module, a dry absorption reaction module and a condensation module which are sequentially connected;

[0008] The waste sulfuric acid pyrolysis recovery module comprises a waste sulfuric acid storage tank, a buffer tank, a cracking furnace and a waste heat boiler which are connected in sequence. The cracking furnace is connected with a natural gas input pipe, and an atomizing spray gun is also connected in the cracking furnace. The discharge end of the buffer tank is connected with the atomizing spray gun, and the output end of the cracking furnace is connected with the waste heat boiler for heat exchange.

[0009] The furnace gas purification module comprises an air preheater, an electrostatic precipitator, a venturi scrubber, a packing tower, a cooling tower, a primary electrostatic precipitator and a secondary electrostatic precipitator which are connected in sequence, and the air preheater is connected to the flue gas outlet of the waste heat boiler;

[0010] The dry absorption reaction module comprises a water seal tank, a drying tower, a primary reaction tower and a secondary reaction tower which are sequentially connected, the water seal tank is connected to the gas outlet of the secondary electric demister, the primary reaction tower and the secondary reaction tower are both provided with a spray head, the spray heads of the primary reaction tower and the secondary reaction tower are both connected with a sodium carbonate liquid supply pipe, and the end of the sodium carbonate liquid supply pipe is connected to a sodium carbonate tank;

[0011] The condensation module includes a buffer barrel, a condensation crystallization group and a filter press which are connected in sequence. The liquid pipe outlets of the primary reaction tower and the secondary reaction tower extend into the buffer barrel. The buffer barrel is also provided with a solution inlet for conveying NaOH solution and lithium aluminum hydride reducing agent.

[0012] As an improvement, an air compressor is further provided between the buffer tank and the atomizing spray gun, and an oxygen meter is further provided at the outlet of the cracking furnace for detecting the outlet oxygen content.

[0013] As an improvement, the sewage end of the packing tower and the Venturi washing tower is also connected to a stripping tower, and the reflux end of the stripping tower is connected to the air inlet end of the first-stage electric precipitator.

[0014] As an improvement, an inclined tube settler is provided between the sewage end and the stripping tower.

[0015] As an improvement, the invention also includes a wastewater neutralization tank which is arranged at the dirt end of the inclined tube settler, the drying tower and the first-stage electrostatic precipitator and the second-stage electrostatic precipitator, and a lime dosing device is arranged near the wastewater neutralization tank.

[0016] As an improvement, a basket filter is further provided between the waste sulfuric acid storage tank and the buffer tank.

[0017] (III) Beneficial effects

[0018] Compared with the prior art, the utility model has the following advantages: in the present application, waste sulfuric acid is recovered and cracked into sulfur dioxide, and sodium sulfite is prepared with NaOH solution through a series of purification and washing, and waste liquid in the production process is recovered through a stripping tower, and waste is treated in a wastewater neutralization tank, thereby reducing pollution to the environment, making full use of the characteristics of waste sulfuric acid, and having relatively good economic development and environmental improvement significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a system for preparing sodium sulfite by thermal decomposition of waste sulfuric acid.

[0020] Figure 2 It is a structural diagram of a filter press.

[0021] Figure 3 It is a structural schematic diagram of the waste sulfuric acid pyrolysis recovery module.

[0022] Figure 4 It is a schematic diagram of the usage structure of the Venturi scrubber, packed tower and cooling tower.

[0023] As shown in the figure: 1. Waste sulfuric acid storage tank; 2. Buffer tank; 3. Cracking furnace; 4. Waste heat boiler; 5. Natural gas inlet pipe; 6. Atomizing spray gun; 7. Air preheater; 8. Electrostatic precipitator; 9. Venturi washing tower; 10. Packing tower; 11. Cooling tower; 12. Primary electrostatic precipitator; 13. Secondary electrostatic precipitator; 14. Water seal tank; 15. Drying tower; 16. Primary reaction tower; 17. Secondary reaction tower; 18. Sodium carbonate liquid supply pipe; 19. Sodium carbonate tank; 20. Buffer barrel; 21. Condensation crystallization group; 22. Filter press; 23. Solution inlet; 24. NaOH solution; 25. Lithium aluminum hydride reducing agent; 26. Air compressor; 27. Oxygen meter; 28. Desorption tower; 29. ​​Inclined tube settler; 30. Wastewater neutralization tank; 31. Lime dosing device; 32. Basket filter. DETAILED DESCRIPTION

[0024] The specific implementation of the utility model is further described below in conjunction with the accompanying drawings, wherein the same parts are represented by the same reference numerals.

[0025] It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to directions in the drawings, and the words "inside" and "outside" refer to directions toward or away from the geometric center of a specific component, respectively.

[0026] It should be noted that when an element is referred to as being "fixed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this article are for illustrative purposes only.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly connected by technicians in the technical field to which the present invention belongs. The terminology used in the specification of the present invention is for the purpose of describing specific embodiments and is not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0028] In order to make the contents of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention.

[0029] Please refer to the attached Figure 1-4 The system for preparing sodium sulfite by pyrolysis of waste sulfuric acid includes a waste sulfuric acid pyrolysis recovery module, a furnace gas purification module, a dry absorption reaction module and a condensation module which are sequentially connected.

[0030] The waste sulfuric acid pyrolysis recovery module includes a waste sulfuric acid storage tank 1, a buffer tank 2, a cracking furnace 3 and a waste heat boiler 4 which are connected in sequence. The cracking furnace 3 is connected with a natural gas input pipe 5, and an atomizing spray gun 6 is also connected in the cracking furnace 3. The discharge end of the buffer tank 2 is connected with the atomizing spray gun 6, and the output end of the cracking furnace 3 is connected with the waste heat boiler 4 for heat exchange; the furnace gas purification module includes an air preheater 7, an electrostatic precipitator 8, a venturi washing tower 9, a packing tower 10, a cooling tower 11, a primary electrostatic precipitator 12 and a secondary electrostatic precipitator 13 which are connected in sequence, and the air preheater 7 is connected with the flue gas outlet of the waste heat boiler 4; the dry absorption reaction module includes a water seal tank 14, a drying tower 1 5. A primary reaction tower 16 and a secondary reaction tower 17, a water seal tank 14 is connected to the gas outlet of the secondary electrostatic precipitator 13, and a spray head is provided in the primary reaction tower 16 and the secondary reaction tower 17, and the spray heads of the primary reaction tower 16 and the secondary reaction tower 17 are connected to a sodium carbonate liquid supply pipe 18, and the end of the sodium carbonate liquid supply pipe 18 is connected to a sodium carbonate tank 19; the condensation module includes a buffer barrel 20, a condensation crystallization group 21 and a filter press 22 which are connected in sequence, and the liquid pipe outlets of the primary reaction tower 16 and the secondary reaction tower 17 extend to the buffer barrel 20, and a solution inlet 23 is also provided in the buffer barrel 20, and the solution inlet 23 conveys NaOH solution 24 and lithium aluminum hydride reducing agent 25.

[0031] When in use, an air compressor 26 is provided between the buffer tank 2 and the atomizing spray gun 6, and an oxygen meter 27 is provided at the outlet of the cracking furnace 3 for detecting the outlet oxygen content. At the same time, a stripping tower 28 is connected to the sewage end of the packed tower 10 and the venturi washing tower 9, and the reflux end of the stripping tower 28 is connected to the air inlet end of the first-stage electric precipitator 12, and an inclined tube settler 29 is provided between the sewage end and the stripping tower 28.

[0032] More specifically, it also includes a wastewater neutralization tank 30 arranged in conjunction with the inclined tube settler 29, the drying tower 15 and the dirt ends of the first-stage electrostatic precipitator 12 and the second-stage electrostatic precipitator 13. A lime dosing device 31 is provided near the wastewater neutralization tank 30, and a basket filter 32 is also provided between the waste sulfuric acid storage tank 1 and the buffer tank 2.

[0033] The Venturi washing tower is an integrated structure of tower and tank, adopts adiabatic evaporation, and the circulating acid system is not equipped with a cooler. The heat is taken away by the dilute acid cooler of the cooling tower behind. After the acid is sprinkled out of the power wave washing tower, it is settled in the inclined tube settler, and the clear liquid returns to the circulation tank at the bottom of the Venturi washing tower and enters the circulation system of the Venturi washing tower for recycling. A part of the circulating liquid is pumped into the degassing tower through the circulating pump of the Venturi washing tower. The clear liquid after desorption is sent to the sewage treatment station for centralized treatment through the circulating pump of the degassing tower. The sludge settled in the inclined tube settler is discharged into the acid ditch and sent to the sewage treatment station, where it can be neutralized with lime.

[0034] The cooling tower is also a tower and tank integrated structure. The sprinkler acid flows out from the circulation tank at the bottom of the cooling tower and is pumped into the cooling tower for recycling through the cooling tower circulation pump. The increased circulating acid is connected to the humidification tower circulation system. The heat of the entire purification system is taken away by the dilute acid cooler. In the design, a high-level water tank is set above the power wave scrubber, and the tower outlet temperature is interlocked with the tower high-level water tank outlet valve to protect downstream equipment and pipelines.

[0035] When the utility model is implemented:

[0036] S1. Waste sulfuric acid flows from the bottom of the waste sulfuric acid storage tank through the process pipeline, passes through the basket filter and enters the underground buffer tank, and then is sent to the atomizing spray gun through a vertical pump to fully contact with compressed air and atomize into the cracking furnace. At the same time, the natural gas is preheated in the cracking furnace, and the air with a temperature reaching the set value is fully burned to generate high temperature, so that the waste sulfuric acid is completely cracked at a high temperature of up to 1000-1200°C, and all the sulfur in the waste sulfuric acid is converted into SO2. The oxygen content at the outlet of the waste acid cracking furnace is controlled by an oxygen meter. The amount of sulfuric acid, natural gas and compressed air at the waste acid cracking furnace are adjusted according to the oxygen content to control the temperature at about 1050°C. The SO2 concentration of the furnace gas at the outlet of the waste acid cracking furnace is about 10%. After the furnace gas passes through the waste heat boiler, the temperature drops to 700°C, of ​​which the superheated steam generated by the waste heat boiler is sold outside. The furnace gas is cooled to 320°C by the air preheater and then enters the purification section;

[0037] S2. The furnace gas from the electrostatic precipitator or the air heat exchanger of the cracking section has a temperature of about 320°C. It enters the Venturi washing tower and is pumped into the interior of the Venturi washing tower with dilute sulfuric acid of about 20% through a dilute acid pump. The dilute sulfuric acid fully contacts the furnace gas from the electrostatic precipitator in the interior of the Venturi washing tower to reduce its temperature to 55°C. The furnace gas then enters the packing tower and is reversely flushed with a large amount of dilute acid in the packing tower. The furnace gas then enters the cooling tower to further remove harmful substances such as mineral dust, arsenic, and fluorine. In order to remove arsenic in the purification section without precipitating arsenic from the acid solution, the concentration of the dilute acid is controlled at 20% and the temperature is controlled at 55°C, so that the arsenic trioxide in the raw gas is dissolved in the dilute sulfuric acid. At the same time, a certain amount of sodium sulfate, water glass, broken glass bottles, broken tiles or broken porcelain rings are added to the 20% purified dilute acid circulation tank to fix the fluoride in the dilute acid. The fluorine fixation rate is above 90%, and fluorosilicate is produced and precipitated and discharged.

[0038] The gas temperature drops below 40°C, and the acid mist particles further increase in size. The sewage discharged from the packing tower is desorbed and SO2 is recovered in the desorption tower and then sent to the sewage treatment station. The SO2 gas returns to the system and then passes through the first and second level electrostatic demisters to remove the acid mist in the high voltage electric field. The acid mist content in the outlet gas is <0.005g / Nm3. The purified gas enters the dry absorption section, and there is a safety water seal tank in front of the drying tower.

[0039] S3. Countercurrent contact between sulfur dioxide gas and sodium carbonate, secondary contact reaction tower

[0040] S4. Take out the desulfurized waste liquid after filtering and precipitation in step S2, precipitate the oxygen dissolved in the desulfurized waste liquid through a vacuum pump under vacuum and extract it through a vacuum pump, add NaOH solution to the desulfurized waste liquid so that the pH value of the desulfurized waste liquid is 9-11, and heat the desulfurized waste liquid until Na2SO4 is completely converted into Na2SO3, and add lithium aluminum hydride reducing agent while adding NaOH solution;

[0041] S5. Preparation of anhydrous sodium sulfite by cooling and crystallization: The desulfurization waste liquid generating Na2SO3 in step S3 is cooled to precipitate Na2SO3 crystals until no more Na2SO3 crystals are precipitated, and the Na2SO3 crystals are separated from the desulfurization waste liquid by filtration.

[0042] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0043] The standard parts used in the utility model can be purchased from the market, and special-shaped parts can be customized according to the description in the specification and the drawings. The specific connection methods of each part adopt the conventional means such as mature bolts, rivets, welding, etc. in the prior art. The machinery, parts and equipment all adopt the conventional models in the prior art, and the circuit connection adopts the conventional connection method in the prior art, which will not be described in detail here. The content not described in detail in this specification belongs to the prior art known to professional and technical personnel in this field.

[0044] The above description of the utility model and its implementation methods is not restrictive. The drawings show only one implementation method of the utility model, and the actual structure is not limited thereto. In short, if ordinary technicians in this field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention of the utility model, they should all fall within the protection scope of the utility model.

Claims

1. A system for preparing sodium sulfite by pyrolysis of waste sulfuric acid, characterized in that: It includes a waste sulfuric acid pyrolysis recovery module, a furnace gas purification module, a dry absorption reaction module and a condensation module which are sequentially connected; The waste sulfuric acid pyrolysis recovery module comprises a waste sulfuric acid storage tank (1), a buffer tank (2), a cracking furnace (3) and a waste heat boiler (4) which are connected in sequence, the cracking furnace (3) is connected with a natural gas input pipe (5), an atomizing spray gun (6) is also connected inside the cracking furnace (3), the discharge end of the buffer tank (2) is connected with the atomizing spray gun (6), and the output end of the cracking furnace (3) is connected with the waste heat boiler (4) for heat exchange; The furnace gas purification module comprises an air preheater (7), an electrostatic precipitator (8), a venturi scrubber (9), a packing tower (10), a cooling tower (11), a primary electrostatic precipitator (12) and a secondary electrostatic precipitator (13) which are connected in sequence, and the air preheater (7) is connected to the flue gas outlet of the waste heat boiler (4); The dry absorption reaction module comprises a water seal tank (14), a drying tower (15), a primary reaction tower (16) and a secondary reaction tower (17) which are sequentially connected, the water seal tank (14) is connected to the gas outlet of the secondary electric demister (13), the primary reaction tower (16) and the secondary reaction tower (17) are both provided with a spray head, the spray heads of the primary reaction tower (16) and the secondary reaction tower (17) are both connected to a sodium carbonate liquid supply pipe (18), and the end of the sodium carbonate liquid supply pipe (18) is connected to a sodium carbonate tank (19); The condensation module comprises a buffer barrel (20), a condensation crystallization group (21) and a filter press (22) which are sequentially connected, and the liquid pipe outlets of the primary reaction tower (16) and the secondary reaction tower (17) extend into the buffer barrel (20). The buffer barrel (20) is also provided with a solution inlet (23), and the solution inlet (23) is used to transport a NaOH solution (24) and a lithium aluminum hydride reducing agent (25).

2. The system for preparing sodium sulfite by pyrolysis of waste sulfuric acid according to claim 1, characterized in that: An air compressor (26) is also provided between the buffer tank (2) and the atomizing spray gun (6), and an oxygen meter (27) is also provided at the outlet of the cracking furnace (3) for detecting the oxygen content at the outlet.

3. The system for preparing sodium sulfite by pyrolysis of waste sulfuric acid according to claim 1, characterized in that: The sewage ends of the packing tower (10) and the Venturi washing tower (9) are also connected to a stripping tower (28), and the reflux end of the stripping tower (28) is connected to the air inlet end of the first-stage electric demister (12).

4. The system for preparing sodium sulfite by pyrolysis of waste sulfuric acid according to claim 3, characterized in that: An inclined tube settler (29) is provided between the sewage end and the desorption tower (28).

5. The system for preparing sodium sulfite by pyrolysis of waste sulfuric acid according to claim 4, characterized in that: It also includes a wastewater neutralization tank (30) arranged in coordination with the inclined tube settler (29), the drying tower (15) and the waste ends of the first-stage electrostatic precipitator (12) and the second-stage electrostatic precipitator (13), and a lime dosing device (31) is arranged near the wastewater neutralization tank (30).

6. The system for preparing sodium sulfite by pyrolysis of waste sulfuric acid according to claim 1, characterized in that: A basket filter (32) is also provided between the waste sulfuric acid storage tank (1) and the buffer tank (2).

Images