A device for concentrating waste acid by using waste heat of calcination flue gas

Abstract

The utility model discloses a kind of calcination flue gas waste heat concentration waste acid device, it includes: acid liquor spray tower, it is used to mix and cooperate waste acid spray to heat, concentrate waste acid with flue gas;Alkali liquor spray tower, it is discharged by acid liquor spray tower to the acid-containing flue gas of neutralization, heat exchange and discharge by alkali liquor spray;Acid liquor recovery device, it is used to recycle waste acid after heating, concentration in acid liquor spray tower;Heat exchange device, it is arranged between acid liquor spray tower and acid liquor recovery device, for recycling alkali liquor waste heat and secondary heating to waste acid;The scheme makes full use of high, medium, low temperature section waste heat in calcination flue gas to heat, concentrate waste acid, to effectively reduce energy consumption in waste acid concentration process, operating cost is low, and recycling and utilization of ferrous sulfate crystal in waste acid is realized by evaporation, concentration, crystallization and separation.

Description

Technical Field

[0001] This utility model relates to the field of environmental protection equipment technology, specifically to a waste acid concentration device for calcination flue gas waste heat. Background Technology

[0002] Currently, titanium dioxide production in my country primarily utilizes the sulfuric acid process. In this process, approximately 7-10 tons of waste acid (18%-23% concentration) are generated for every ton of titanium dioxide produced. The main components of this waste acid are free sulfuric acid, ferrous sulfate, metatitanic acid, and other sulfates. The treatment and comprehensive utilization of this waste acid has long been a challenging environmental issue in sulfuric acid titanium dioxide production, leading to its classification as a "high-energy-consuming and high-polluting" industry.

[0003] In the metatitanic acid calcination process of sulfuric acid titanium dioxide, natural gas is often used as the energy source, generating a large amount of high-temperature exhaust gas at 400-500℃. Because the exhaust gas contains impurities such as sulfur trioxide and titanium dioxide, it easily causes corrosion and scaling blockage of equipment, making direct utilization of waste heat difficult, and direct discharge of the exhaust gas results in resource waste and environmental pollution. Utility Model Content

[0004] To address the aforementioned shortcomings of existing technologies, this utility model provides a waste acid concentration device using waste heat from calcination flue gas. This device utilizes the company's own high-temperature calcination tail gas to concentrate waste acid, achieving energy conservation, emission reduction, and carbon reduction.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A waste acid concentration device for calcination flue gas waste heat is provided, comprising: an acid spray tower for mixing flue gas and waste acid and heating and concentrating the waste acid in conjunction with waste acid spraying; an alkali spray tower for neutralizing, exchanging heat with and discharging the acid-containing flue gas discharged from the acid spray tower through alkali spraying; an acid recovery device for recovering the waste acid heated and concentrated in the acid spray tower; and a heat exchange device disposed between the acid spray tower and the acid recovery device for recovering alkali waste heat and reheating the waste acid.

[0006] Furthermore, the acid spray tower is provided with a first exhaust port, an acid spray pipe, a Venturi spray pipe, an acid inlet, and an acid tank from top to bottom. The nozzle of the Venturi spray pipe is connected to one side of the acid spray tower. The acid tank is connected to the inlet of the Venturi spray pipe and the acid spray pipe through a filter and an acid circulation pump, respectively. The Venturi spray pipe is provided with a flue gas inlet connected to an external flue gas supply pipeline. An acid outlet is provided on one side of the acid tank.

[0007] Furthermore, the acid spray pipe includes a primary spray pipe and a secondary spray pipe arranged in layers, with multi-faceted spherical packing material placed between the primary spray pipe and the secondary spray pipe.

[0008] The beneficial effects of adopting the above technical solution are as follows: This solution uses a Venturi spray pipe to uniformly mix waste acid with high-temperature flue gas, thereby performing initial heat exchange and atomizing the waste acid. Then, the flue gas passes from bottom to top through a primary spray pipe, a multi-faceted spherical packing, a secondary spray pipe, and a corrugated fiberglass demister. The atomized droplets sprayed from the primary and secondary spray pipes collide and exchange heat with the flue gas, causing the water in the droplets to vaporize into water vapor. Under the entrainment effect of the flue gas, it forms a high-humidity, low-temperature acidic flue gas that is discharged outside the tower, while the droplets with a higher specific gravity of acid sink to the bottom of the tower. This cycle is repeated to achieve the initial heating and concentration of waste acid.

[0009] Furthermore, the alkali spray tower is provided with a second exhaust port, a multi-layered alkali spray pipe, a first air inlet, a liquid replenishment port, and an alkali tank from top to bottom. The alkali tank is connected to the alkali spray pipe via an alkali circulation pump, and the first air inlet is connected to the first exhaust port.

[0010] Furthermore, corrugated fiberglass demisters are installed in both the acid spray tower above the acid spray pipe and the alkali spray tower above the alkali spray pipe, and drain outlets are installed on one side of the bottom of both the acid tank and the alkali tank.

[0011] The beneficial effects of adopting the above technical solution are as follows: the acidic flue gas discharged from the acid spray tower is cooled, dehumidified, and neutralized by multi-layer alkaline spraying, and discharged after demisting, while the temperature of the alkaline solution increases during the circulating spraying process.

[0012] Furthermore, the heat exchange device includes a heat exchanger and a water source high-temperature heat pump. The heat exchanger is installed on the connecting pipeline between the acid outlet and the acid recovery device, and the water source high-temperature heat pump is installed on the connecting pipeline between the alkali tank and the alkali spray pipe. The heat exchanger and the water source high-temperature heat pump are connected through a hot water circulation pipeline, and a hot water circulation pump is installed on the hot water circulation pipeline.

[0013] The beneficial effects of adopting the above technical solution are as follows: the water source high temperature heat pump uses high temperature alkaline solution as heat source, the hot water circulation pump pressurizes the hot water and then reheats the low temperature hot water through the water source high temperature heat pump, and the high temperature hot water exchanges heat with the pre-heated and concentrated waste acid through the heat exchanger, thereby forming high temperature acid solution.

[0014] Furthermore, the acid recovery device includes a flash tank, a crystallizer, and a fine filter. The acid outlet is connected to the inlet on one side of the flash tank via a filter and an acid transfer pump. The outlet at the bottom of the flash tank is connected to the top of the crystallizer. A supernatant outlet is provided on one side of the crystallizer. The bottom of the crystallizer is connected to the fine filter, which includes an acid outlet and a ferrous sulfate crystal outlet.

[0015] The beneficial effects of adopting the above technical solution are as follows: the water in the high-temperature acid solution is evaporated by the flash tank, and ferrous sulfate crystals are precipitated in the crystallizer of the high-concentration acid solution. The supernatant of the acid solution is sent to the external secondary concentration process through the supernatant outlet, and the acid solution containing ferrous sulfate crystals is sent to the fine filter for filtration and separation to recover the ferrous sulfate crystals. The filtered high-concentration acid solution is sent to the external secondary concentration process for deep concentration, thereby realizing the recycling of waste acid.

[0016] Furthermore, a U-shaped condenser is installed between the flash tank and the alkali spray tower. The U-shaped condenser is installed on the connecting pipeline between the alkali tank and the alkali spray pipe. The air inlet of the U-shaped condenser is connected to the exhaust port at the top of the flash tank. The top and bottom of the U-shaped condenser are respectively equipped with an exhaust port and a liquid collection tank. The bottom of the liquid collection tank is equipped with a drain outlet.

[0017] The beneficial effects of adopting the above technical solution are as follows: the water vapor evaporated in the flash tank is condensed by the U-shaped condenser and recycled to the collection tank for periodic discharge; the non-condensable gas is discharged to the vacuum pump process; and the cold source of the condenser is the alkaline solution cooled by the heat pump, thereby achieving the heating of the alkaline solution.

[0018] Furthermore, the heat exchange device includes a heat exchanger and a water source high-temperature heat pump. The heat exchanger is installed on the connecting pipeline between the acid outlet and the flash tank, and the water source high-temperature heat pump is installed on the connecting pipeline between the alkali tank and the alkali spray pipe. The heat exchanger and the water source high-temperature heat pump are connected through a hot water circulation pipeline, and a hot water circulation pump is installed on the hot water circulation pipeline.

[0019] The beneficial effects of adopting the above technical solution are as follows: the water source high temperature heat pump uses high temperature alkaline solution as heat source, the hot water circulation pump pressurizes the hot water and then reheats the low temperature hot water through the water source high temperature heat pump, and the high temperature hot water exchanges heat with the pre-heated and concentrated waste acid through the heat exchanger, thereby forming high temperature acid solution.

[0020] The beneficial effects of this utility model are as follows: This solution fully utilizes the waste heat from the high, medium, and low temperature sections of the calcination flue gas to heat and concentrate the waste acid, thereby effectively reducing energy consumption during the waste acid concentration process and achieving low operating costs. Furthermore, it recovers and utilizes ferrous sulfate crystals from the waste acid through evaporation, concentration, crystallization, and separation. The flue gas in this solution is cooled, dehumidified, and neutralized after passing through multi-faceted spherical packing, a corrugated fiberglass demister, waste acid spraying, and alkaline spraying, thus reducing the emission of harmful gases such as sulfur dioxide and sulfur trioxide to meet green emission requirements. This solution is suitable for treating 20-35% concentration waste acid generated in the sulfuric acid process for titanium dioxide production and can be widely promoted and applied. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a waste acid concentration device using waste heat from calcination flue gas.

[0022] Among them, 1. Acid spray tower, 11. First exhaust port, 12. Venturi spray pipe, 13. Acid inlet, 14. Acid tank, 15. Filter, 16. Acid circulation pump, 17. Flue gas inlet, 18. Acid outlet, 19. Primary spray pipe, 110. Secondary spray pipe, 111. Multi-faceted spherical packing, 2. Alkali spray tower, 21. Second exhaust port, 22. Alkali spray pipe, 23. First air inlet, 24. Makeup 25. Alkali tank, 26. Alkali circulation pump, 3. Corrugated fiberglass demister, 4. Drain outlet, 5. Flash tank, 6. Crystallizer, 61. Supernatant outlet, 7. Fine filter, 71. Acid outlet, 72. Ferrous sulfate crystal outlet, 8. Acid transfer pump, 9. U-shaped condenser, 91. Collection tank, 10. Heat exchanger, 11. High-temperature heat pump from water source, 12. Hot water circulation pipeline, 13. Hot water circulation pump. Detailed Implementation

[0023] The specific embodiments of this utility model are described below to enable those skilled in the art to understand this utility model. However, it should be understood that this utility model is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of this utility model as defined and determined by the appended claims, these changes are obvious. All utility model creations utilizing the concept of this utility model are within the scope of protection.

[0024] like Figure 1 As shown, the waste acid concentration device for calcination flue gas waste heat in this scheme includes: an acid spray tower 1, which is used to mix flue gas and waste acid and heat and concentrate the waste acid in conjunction with waste acid spraying; an alkali spray tower 2, which neutralizes and exchanges heat on the acid-containing flue gas discharged from the acid spray tower 1 through alkali spraying and then discharges it; an acid recovery device, which is used to recover the waste acid heated and concentrated in the acid spray tower 1; and a heat exchange device, which is set between the acid spray tower 1 and the acid recovery device, for recovering the alkali waste heat and reheating the waste acid.

[0025] As an optional implementation, the acid spray tower 1 is provided with a first exhaust port 11, an acid spray pipe, a venturi spray pipe 12, an acid inlet 13, and an acid tank 14 from top to bottom. The spray port of the venturi spray pipe 12 is connected to one side of the acid spray tower 1. The acid tank 14 is connected to the inlet of the venturi spray pipe 12 and the acid spray pipe through a filter 15 and an acid circulation pump 16, respectively. The venturi spray pipe 12 is provided with a flue gas inlet 17 connected to an external flue gas supply pipeline. An acid outlet 18 is provided on one side of the acid tank 14. The acid spray pipe includes a primary spray pipe 19 and a secondary spray pipe 110 arranged in layers. A multi-faceted spherical packing 111 is provided between the primary spray pipe 19 and the secondary spray pipe 110.

[0026] The working principle of acid spray tower 1 is as follows: waste acid with a concentration of 20% and containing ferrous sulfate enters the acid tank 14 at the bottom of acid spray tower 1 through acid inlet 13. Then, the waste acid is pressurized by filter 15 and acid circulation pump 16 and enters the tower in three paths. One path is connected to the inlet of Venturi spray pipe 12 for mixing with flue gas and performing primary heat exchange. The other two paths are connected to primary spray pipe 19 and secondary spray pipe 110 respectively, thus performing secondary and tertiary heat exchange. The calcination flue gas at 450℃ enters the tower through Venturi spray pipe 12, collides and exchanges heat with the acid spray liquid, and then evaporates the water in the acid droplets. The evaporated water vapor is discharged to alkaline spray tower 2 with the flue gas under the action of the induced draft fan. The acid with a larger specific gravity in the droplets settles into acid tank 14. This cycle is repeated to initially concentrate the waste acid and heat it.

[0027] As an optional implementation, the alkali spray tower 2 is provided with a second exhaust port 21, a multi-layered alkali spray pipe 22, a first air inlet 23, a liquid replenishment port 24, and an alkali tank 25 from top to bottom. The alkali tank 25 is connected to the alkali spray pipe 22 through an alkali circulation pump 26, and the first air inlet 23 is connected to the first exhaust port 11. Both the acid spray tower 1 located above the acid spray pipe and the alkali spray tower 2 located above the alkali spray pipe 22 are provided with corrugated fiberglass demisters 3. Drainage ports 4 are provided on one side of the bottom of the acid tank 14 and on one side of the bottom of the alkali tank 25.

[0028] The working principle of the alkaline spray tower 2 is as follows: the acidic flue gas discharged from the acid spray tower 1 is cooled, dehumidified, and neutralized by multi-layer alkaline spraying, and discharged after being demisted by the corrugated fiberglass demister 3; at the same time, the temperature of the alkaline solution can be increased during the circulating spraying process.

[0029] As an optional implementation, the acid recovery device includes a flash tank 5, a crystallizer 6, and a fine filter 7. The acid outlet 18 is connected to the inlet on one side of the flash tank 5 via a filter 15 and an acid transfer pump 8. The outlet at the bottom of the flash tank 5 is connected to the top of the crystallizer 6. A supernatant outlet 61 is provided on one side of the crystallizer 6. The bottom of the crystallizer 6 is connected to the fine filter 7. The fine filter 7 includes an acid outlet 71 and a ferrous sulfate crystal outlet 72.

[0030] This scheme uses a flash tank 5 to evaporate the water in the high-temperature acid solution. The higher concentration of acid solution precipitates ferrous sulfate crystals in the crystallizer 6. The supernatant of the acid solution is sent to an external secondary concentration process through the supernatant outlet 61. The acid solution containing ferrous sulfate crystals is sent to a fine filter 7 for filtration and separation to recover the ferrous sulfate crystals. The filtered higher concentration acid solution is sent to an external secondary concentration process for deep concentration, thereby realizing the recycling of waste acid.

[0031] As an optional implementation, a U-shaped condenser 9 is installed between the flash tank 5 and the alkali spray tower 2. The U-shaped condenser 9 is installed on the connecting pipe between the alkali tank 25 and the alkali spray pipe 22. The air inlet of the U-shaped condenser 9 is connected to the exhaust port at the top of the flash tank 5. The top and bottom of the U-shaped condenser 9 are respectively provided with an exhaust port and a collection tank 91. The bottom of the collection tank 91 is provided with a drain port 4. The water vapor evaporated in the flash tank 5 is condensed by the U-shaped condenser 9 and recycled to the collection tank 91 for periodic discharge. Non-condensable gases are discharged through the exhaust port of the U-shaped condenser 9. The cold source of the condenser is alkali cooled by a heat pump, which realizes the heating of the alkali.

[0032] As an optional implementation, the heat exchange device includes a heat exchanger 10 and a water source high-temperature heat pump 11. The heat exchanger 10 is installed on the connecting pipeline between the acid outlet 18 and the flash tank 5, and the water source high-temperature heat pump 11 is installed on the connecting pipeline between the alkali tank 25 and the alkali spray pipe 22. The heat exchanger 10 and the water source high-temperature heat pump 11 are connected by a hot water circulation pipeline 12, and a hot water circulation pump 13 is installed on the hot water circulation pipeline 12. The water source high-temperature heat pump 11 uses high-temperature alkali as a heat source, and the hot water circulation pump 13 pressurizes the hot water and reheats the low-temperature hot water through the water source high-temperature heat pump 11. The high-temperature hot water exchanges heat with the pre-heated and concentrated waste acid through the heat exchanger 10, thereby forming a high-temperature acid solution.

[0033] In summary, this solution fully utilizes the waste heat from the high, medium, and low temperature sections of the calcination flue gas to heat and concentrate the waste acid, thereby effectively reducing energy consumption during the waste acid concentration process and achieving low operating costs. Furthermore, it recovers and utilizes ferrous sulfate crystals from the waste acid through evaporation, concentration, crystallization, and separation. The flue gas in this solution is cooled, dehumidified, and neutralized after passing through multi-faceted spherical packing 111, a corrugated fiberglass demister 3, waste acid spraying, and alkaline spraying, thus reducing the emission of harmful gases such as sulfur dioxide and sulfur trioxide, meeting green emission requirements. This solution is suitable for treating 20-35% concentration waste acid generated in the sulfuric acid process for titanium dioxide production and can be widely promoted and applied.

Claims

1. A device for concentrating waste acid using waste heat from calcination flue gas, characterized in that, include: Acid spray tower is used to mix flue gas with waste acid and to heat and concentrate the waste acid in conjunction with waste acid spraying; An alkaline spray tower neutralizes, exchanges heat with, and discharges acidic flue gas discharged from an acid spray tower by spraying alkaline solution. An acid recovery device is used to recover waste acid that has been heated and concentrated in an acid spray tower. A heat exchange device is installed between the acid spray tower and the acid recovery device to recover the waste heat of the alkali solution and reheat the waste acid.

2. The waste acid concentration device for calcination flue gas waste heat according to claim 1, characterized in that, The acid spray tower is provided with a first exhaust port, an acid spray pipe, a Venturi spray pipe, an acid inlet, and an acid tank from top to bottom. The nozzle of the Venturi spray pipe is connected to one side of the acid spray tower. The acid tank is connected to the inlet of the Venturi spray pipe and the acid spray pipe through a filter and an acid circulation pump, respectively. The Venturi spray pipe is provided with a flue gas inlet connected to an external flue gas supply pipeline. An acid outlet is provided on one side of the acid tank.

3. The waste acid concentration device for calcination flue gas waste heat according to claim 2, characterized in that, The acid spray pipe includes a primary spray pipe and a secondary spray pipe arranged in layers, with multi-faceted spherical packing material disposed between the primary spray pipe and the secondary spray pipe.

4. The waste acid concentration device for calcination flue gas waste heat according to claim 2, characterized in that, The alkaline spray tower is provided with a second exhaust port, a multi-layered alkaline spray pipe, a first air inlet, a liquid replenishment port, and an alkaline tank from top to bottom. The alkaline tank is connected to the alkaline spray pipe via an alkaline circulation pump, and the first air inlet is connected to the first exhaust port.

5. The waste acid concentration device for calcination flue gas waste heat according to claim 4, characterized in that, Both the acid spray tower located above the acid spray pipe and the alkali spray tower located above the alkali spray pipe are equipped with corrugated fiberglass demisters. Drainage outlets are provided on one side of the bottom of the acid tank and one side of the bottom of the alkali tank.

6. The waste acid concentration device for calcination flue gas waste heat according to claim 4, characterized in that, The acid recovery device includes a flash tank, a crystallizer, and a fine filter. The acid outlet is connected to the inlet on one side of the flash tank via a filter and an acid transfer pump. The outlet at the bottom of the flash tank is connected to the top of the crystallizer. A supernatant outlet is provided on one side of the crystallizer. The bottom of the crystallizer is connected to the fine filter. The fine filter includes an acid outlet and a ferrous sulfate crystal outlet.

7. The waste acid concentration device for calcination flue gas waste heat according to claim 6, characterized in that, A U-shaped condenser is installed between the flash tank and the alkali spray tower. The U-shaped condenser is installed on the connecting pipe between the alkali tank and the alkali spray pipe. The air inlet of the U-shaped condenser is connected to the exhaust port at the top of the flash tank. The top and bottom of the U-shaped condenser are respectively provided with an exhaust port and a liquid collection tank. The bottom of the liquid collection tank is provided with a drain outlet.

8. The waste acid concentration device for calcination flue gas waste heat according to claim 6, characterized in that, The heat exchange device includes a heat exchanger and a water source high-temperature heat pump. The heat exchanger is installed on the connecting pipeline between the acid outlet and the flash tank, and the water source high-temperature heat pump is installed on the connecting pipeline between the alkali tank and the alkali spray pipe. The heat exchanger and the water source high-temperature heat pump are connected through a hot water circulation pipeline, and a hot water circulation pump is installed on the hot water circulation pipeline.

Images