Multi-stage segmented treatment system for high-halogen flue gas

Abstract

The utility model relates to the field of flue gas treatment, and provides a multi-stage segmented treatment system for high-halogen flue gas. Comprising a defluorination tower, a dechlorination tower and a desulfurization tower which are sequentially connected in series, the bottom in the defluorination tower is connected with a calcium hydroxide solution tank and a calcium chloride solution tank through a circulating pump, the bottom of the defluorination tower is connected with a calcium fluoride recovery system through a pipeline, and the bottom of the dechlorination tower is connected with an acid liquor storage tank through a pipeline and a discharge pump. The desulfurization tower is connected with a limestone slurry tank through a slurry pump, a spraying device in the dechlorination tower pumps slurry from the bottom through a circulating pump and sprays the slurry downwards, and the bottom of the dechlorination tower is connected with a gypsum recovery system through a pipeline and a gypsum discharge pump. According to respective characteristics of hydrogen fluoride, hydrogen chloride and sulfur dioxide, targeted absorption is carried out in different sections, so that mutual interference of different acidic gases is avoided, and the absorption efficiency is improved; the purity of the absorbed by-products in each section is also improved, and the recycled by-products can be reutilized.

Description

Technical Field

[0001] This utility model relates to the field of flue gas treatment, specifically to a multi-stage segmented treatment system for high-halogen flue gas. Background Technology

[0002] The incineration of organic solid waste generates high-halogen flue gas containing chlorine, sulfur, and fluorine. Traditional flue gas treatment systems primarily use single- or two-stage desulfurization towers to indiscriminately absorb acidic gases such as hydrogen fluoride, hydrogen chloride, and sulfur dioxide. When using the common limestone-gypsum method for desulfurization, chloride and calcium ions continuously accumulate in the desulfurization liquid, forcing an increase in the open-circuit water flow and exacerbating the pressure on subsequent desulfurization wastewater treatment. This is particularly severe in flue gas treatment systems using high-halogen organic materials as feedstock. Furthermore, due to the different properties of hydrogen fluoride, hydrogen chloride, and sulfur dioxide, interference between different acidic gases during the treatment process reduces absorption efficiency, resulting in complex byproducts that are difficult to effectively recover and reuse. Summary of the Invention

[0003] In order to overcome the shortcomings of existing technologies in flue gas treatment, such as mutual interference between different components of gases and the difficulty in reusing complex by-products, this utility model provides a multi-stage segmented treatment system for high-halogen flue gas.

[0004] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0005] A multi-stage, segmented treatment system for high-halogen flue gas includes a defluorination tower, a dechlorination tower, and a desulfurization tower connected in series. The defluorination tower has a flue gas inlet at its center. The bottom of the defluorination tower is connected to a calcium hydroxide solution tank and a calcium chloride solution tank via a circulating pump. A spraying device is installed inside the defluorination tower, which draws solution from the bottom of the tower and sprays it downwards via the circulating pump. The bottom of the defluorination tower is connected to a calcium fluoride recovery system via a pipeline. The top of the defluorination tower is connected to the flue gas inlet at the center of the dechlorination tower via a pipeline. The dechlorination tower is equipped with a flushing water tank. The spraying device inside the dechlorination tower draws water from the bottom and sprays it through a circulating pump. The bottom of the dechlorination tower is connected to an acid storage tank through a pipe and a discharge pump. The top of the dechlorination tower is connected to the flue gas inlet in the middle of the desulfurization tower through a pipe. The desulfurization tower is connected to a limestone slurry tank through a slurry pump. The spraying device inside the dechlorination tower draws slurry from the bottom and sprays it downwards through a circulating pump. The bottom of the dechlorination tower is connected to a gypsum recovery system through a pipe and a gypsum discharge pump. The top of the desulfurization tower is equipped with a tail gas emission port.

[0006] Furthermore, the calcium fluoride recovery system includes a water collection pit, which is connected to the bottom of the defluorination tower. The water collection pit is connected to a flocculation tank via a water collection pump. The flocculation tank is connected to a coagulation aid tank via an overflow pipe. The coagulation aid tank is connected to a sedimentation tank via an overflow pipe. The top of the sedimentation tank is connected to a clear water tank via an overflow pipe. The bottom of the sedimentation tank is connected to a filter press via a pipe.

[0007] Furthermore, the clear water tank is connected to a defluorination tower or a flushing water tank via a clear water pump.

[0008] Furthermore, the gypsum recovery system includes a mixing tank connected to a gypsum discharge pump. The top of the mixing tank is connected to a wastewater tank or a desulfurization tower via an overflow pipe. The bottom of the mixing tank is connected to a vacuum belt filter via a pipe. The filtrate outlet of the vacuum belt filter is connected to a filtrate pool via a gas-water separator. The filtrate pool is connected to a limestone slurry tank or a desulfurization tower via a pipe and a filtrate pump.

[0009] Furthermore, demisters are installed below the top outlets of the defluorination tower, dechlorination tower, and desulfurization tower, respectively. Each demister includes a baffle plate with a zigzag channel and spray pipes distributed on the upper and lower sides of the baffle plate. The spray pipes are connected to a flushing water tank.

[0010] Furthermore, a side stirring device is installed at the bottom of the defluorination tower.

[0011] Furthermore, a pulse device is installed at the bottom of the dechlorination tower, the pulse device including a pulse suspension pump installed outside the dechlorination tower and an aeration pipe installed inside the dechlorination tower.

[0012] Furthermore, a side stirring device and an oxidation fan are installed at the bottom of the desulfurization tower, and the oxidation fan supplies air into the dechlorination tower through a pipeline.

[0013] After adopting the above technical solution, the beneficial effects of this utility model are as follows: Based on the characteristics of hydrogen fluoride, hydrogen chloride, and sulfur dioxide, the fluorine, chlorine, and sulfur in the high-halogen flue gas are treated separately through a three-stage treatment method, and targeted absorption is carried out in different stages. This not only avoids the interference between different acidic gases and improves the absorption efficiency, but also improves the purity of the absorption by-products in each stage. The recovered by-products, calcium fluoride, dilute hydrochloric acid, and gypsum, can be reused. Attached Figure Description

[0014] Figure 1 This is a system schematic diagram of the present invention.

[0015] In the diagram: 1. Defluorination tower; 2. Dechlorination tower; 3. Desulfurization tower; 4. Transfer pump; 5. Side agitator; 6. Spray pipe; 7. Water collection pit; 8. Flocculation tank; 9. Coagulation aid tank; 10. Sedimentation tank; 11. Clear water tank; 12. Filter press; 13. Washing water tank; 14. Pulse device; 15. Acid storage tank; 16. Limestone slurry tank; 17. Oxidation blower; 18. Mixing tank; 19. Wastewater tank; 20. Vacuum belt filter; 21. Gas-water separator; 22. Filtration tank; 23. Demister; 24. Calcium hydroxide solution tank; 25. Calcium chloride solution tank. Detailed Implementation

[0016] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings:

[0017] As shown in the figure, a multi-stage segmented treatment system for high-halogen flue gas includes a defluorination tower 1, a dechlorination tower 2, and a desulfurization tower 3 connected in series, used to absorb hydrogen fluoride, hydrogen chloride, and sulfur dioxide gases generated during the incineration of organic solid waste.

[0018] The defluorination tower 1 is used to absorb hydrogen fluoride gas from flue gas. The flue gas enters from the middle of the tower. The tower draws solutions from calcium hydroxide solution tank 24 and calcium chloride solution tank 25 via a transfer pump 4, forming a solution pool in its lower section. A side stirrer 5 is installed on the side wall of the defluorination tower 1 to maintain solution homogeneity. Multiple vertically distributed spray pipes 6 are installed above the flue gas inlet in the defluorination tower 1. A circulating pump draws solution from the bottom and sprays it downwards to absorb and treat the hydrogen fluoride in the flue gas. The purpose of adding calcium chloride solution is to maintain an environment of excess calcium and chloride ions within the tower, promoting the formation of calcium fluoride precipitate through the common ion effect and inhibiting the absorption of hydrogen chloride gas. The generated calcium fluoride deposits at the bottom of the defluorination tower and is eventually collected in a collection pit 7 via a pipeline.

[0019] The slurry in the collection pit 7 is pumped into the flocculation tank 8. After flocculation in the flocculation tank 8 and the coagulation aid tank 9, it overflows into the sedimentation tank 10 for sedimentation. The clear liquid at the top of the sedimentation tank 10 overflows into the clear water tank 11 for collection. The clear liquid can be pumped into the defluorination tower 1 for continued use. The sediment at the bottom of the sedimentation tank 10 enters the filter press 12 through a pipeline for filtration. The filter residue is calcium fluoride, a byproduct that can be recycled as an additive to improve the fluidity of incinerator slag. The filtrate from the filter press can be collected and reused in the clear water tank.

[0020] After hydrogen fluoride absorption, the flue gas enters the flue gas inlet in the middle of the dechlorination tower 2 through a pipe from the top of the defluorination tower 1. The dechlorination tower 2 is used to absorb hydrogen chloride gas from the flue gas. Clean water from the flushing water tank 13 is injected into the dechlorination tower 2, and a circulating pump sends the clean water from the bottom of the tower to a spray device inside the dechlorination tower for spraying. The hydrogen chloride gas is absorbed by the clean water, forming dilute hydrochloric acid, which is collected at the bottom of the dechlorination tower. A pulse device 14 is installed at the bottom of the dechlorination tower, which pulses and sprays the gas below the liquid level through an external pulse suspension pump and internal spray pipes. The hydrochloric acid at the bottom of the dechlorination tower 2 is finally collected in an acid storage tank 15 by an acid discharge pump.

[0021] The top gas outlet of dechlorination tower 2 is connected to the flue gas inlet in the middle of desulfurization tower 3 via a pipeline. Desulfurization tower 3 is used to absorb sulfur dioxide gas in the flue gas, employing the limestone-gypsum method. Slurry is injected into desulfurization tower 3 from limestone slurry tank 16 via a slurry pump. A spraying device inside dechlorination tower 3 draws slurry from the bottom and sprays it downwards via a circulating pump. A side stirring device and an oxidation fan 17 are installed at the bottom of the desulfurization tower, and the oxidation fan 17 supplies air into the dechlorination tower via a pipeline. The sulfur dioxide in the slurry produces sulfurous acid, which reacts with lime to form calcium sulfite. The calcium sulfite is oxidized to form calcium sulfate precipitate, i.e., gypsum, a byproduct. The desulfurized flue gas is discharged from the top of the desulfurization tower, and the bottom of dechlorination tower 3 is connected to a gypsum recovery system via a pipeline and a gypsum discharge pump.

[0022] The gypsum recovery system includes a mixing tank 18. The slurry at the bottom of the desulfurization tower 3 enters the mixing tank 18, is stirred and settles. The wastewater at the top overflows back into the desulfurization tower 3 or the wastewater tank 19. The gypsum slurry at the bottom enters the vacuum belt filter 20 through a pipeline for filtration. The filtered solid is gypsum and is recycled. The filtered liquid and some gas are separated by a gas-liquid separator 21. The gas is vented and the liquid enters the filtrate tank 22 for collection. The liquid in the filtrate tank 22 is pumped into the desulfurization tower 3 or the limestone slurry tank 16 through a filtrate pump.

[0023] Demisters 23 are installed below the top outlets of the defluorination tower 1, dechlorination tower 2, and desulfurization tower 3, respectively. The demisters include a baffle plate with a zigzag channel and spray pipes distributed on the upper and lower sides of the baffle plate. The clean water for the spray pipes is supplied by a flushing water tank 13 and a flushing water pump.

Claims

1. A multi-stage segmented treatment system for high-halogen flue gas, characterized in that, The system comprises a defluorination tower, a dechlorination tower, and a desulfurization tower connected in series. The defluorination tower has a flue gas inlet at its center. A calcium hydroxide solution tank and a calcium chloride solution tank are connected to the bottom of the defluorination tower via a circulating pump. A spraying device is installed inside the defluorination tower, drawing solution from the bottom of the tower and spraying it downwards via the circulating pump. A calcium fluoride recovery system is connected to the bottom of the defluorination tower via a pipeline. The top of the defluorination tower is connected to the flue gas inlet at the center of the dechlorination tower via a pipeline. The dechlorination tower is connected to a flushing water tank. A spraying device inside the dechlorination tower draws water from the bottom via a circulating pump and sprays it downwards. An acid storage tank is connected to the bottom of the dechlorination tower via a pipeline and a discharge pump. The top of the dechlorination tower is connected to the flue gas inlet at the center of the desulfurization tower via a pipeline. A limestone slurry tank is connected to the desulfurization tower via a slurry pump. A spraying device inside the dechlorination tower draws slurry from the bottom via a circulating pump and sprays it downwards. A gypsum recovery system is connected to the bottom of the dechlorination tower via a pipeline and a gypsum discharge pump. A tail gas emission outlet is located at the top of the desulfurization tower.

2. The high-halogen flue gas multi-stage segmented treatment system according to claim 1, characterized in that, The calcium fluoride recovery system includes a water collection pit connected to the bottom of the defluorination tower. The water collection pit is connected to a flocculation tank via a water collection pump. The flocculation tank is connected to a coagulation aid tank via an overflow pipe. The coagulation aid tank is connected to a sedimentation tank via an overflow pipe. The top of the sedimentation tank is connected to a clear water tank via an overflow pipe. The bottom of the sedimentation tank is connected to a filter press via a pipe.

3. The high-halogen flue gas multi-stage segmented treatment system according to claim 2, characterized in that, The clear water tank is connected to the defluorination tower or the flushing water tank via a clear water pump.

4. The high-halogen flue gas multi-stage segmented treatment system according to claim 1, characterized in that, The gypsum recovery system includes a mixing tank connected to a gypsum discharge pump. The top of the mixing tank is connected to a wastewater tank or a desulfurization tower via an overflow pipe. The bottom of the mixing tank is connected to a vacuum belt filter via a pipe. The filtrate outlet of the vacuum belt filter is connected to a filtrate pool via a gas-water separator. The filtrate pool is connected to a limestone slurry tank or a desulfurization tower via a pipe and a filtrate pump.

5. The high-halogen flue gas multi-stage segmented treatment system according to claim 1, characterized in that, Demisters are installed below the top outlets of the defluorination tower, dechlorination tower, and desulfurization tower, respectively. Each demister includes a partition with a zigzag channel and spray pipes distributed on the upper and lower sides of the partition. The spray pipes are connected to a flushing water tank.

6. The multi-stage segmented treatment system for high-halogen flue gas according to claim 1, characterized in that, The bottom of the defluorination tower is equipped with a side stirring device.

7. The high-halogen flue gas multi-stage segmented treatment system according to claim 1, characterized in that, The bottom of the dechlorination tower is equipped with a pulse device, which includes a pulse suspension pump installed on the outside of the dechlorination tower and an aeration pipe installed inside the dechlorination tower.

8. The high-halogen flue gas multi-stage segmented treatment system according to claim 1, characterized in that, The bottom of the desulfurization tower is equipped with a side stirring device and an oxidation fan, and the oxidation fan supplies air into the dechlorination tower through a pipeline.

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