Byproduct salt separation treatment method for flue gas desulfurization

Abstract

The invention discloses a flue gas desulfurization byproduct salt separation treatment method, which comprises a sodium salt ash dissolving system, a sodium salt ash solution filtering system, a cooling freezing crystallization system, a mother liquor evaporation system, a crystallization separation system, a dissolving cooling precipitation system and a post-treatment system, the sodium salt ash solution filtering system comprises a filtering device, the cooling and freezing system comprises a cooling and freezing device, a flue gas lithium bromide refrigerating unit, a mirabilite collecting device, a flue and a cold water pipe, and the flue gas lithium bromide refrigerating unit is connected with an original flue gas flue through the flue. The flue gas waste heat is fully utilized for refrigeration and heating, the problems that the solubility of sodium sulfate and the solubility of sodium carbonate are close, and salt separation and separation are not prone to occurring are solved, the operation cost is low, desulfurization by-products are converted into sodium sulfate and sodium carbonate finished product salt, and resources are recycled.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas desulfurization, and in particular to a method for treating by-product salt separation in flue gas desulfurization. Background Art

[0002] The desulfurization by-product of the dry desulfurization process is sodium salt ash, which includes Na2CO3, Na2SO4, a small amount of NaHCO3 and ash. The saturated solubility of Na2CO3 and Na2SO4 is similar at a certain temperature. After evaporation and crystallization, they are mixed salts and cannot be separated. This reduces the performance of the sodium salt. How to separate the salt with low energy consumption, simple process and low operation requirements is a difficult problem that needs to be studied and solved urgently. Therefore, the technicians in this field provide a method for separating the salt of flue gas desulfurization by-products to solve the problems raised in the above background technology. Summary of the invention

[0003] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for treating by-product salt separation in flue gas desulfurization.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A method for treating byproduct salt separation in flue gas desulfurization comprises: a sodium salt ash dissolution system, a sodium salt ash solution filtration system, a cooling and freezing crystallization system, a mother liquor evaporation system, a crystallization separation system, a dissolution cooling and precipitation system, and a post-treatment system.

[0005] As a further solution of the present invention, the sodium salt ash dissolution system comprises a sodium ash dissolution tank.

[0006] As a further solution of the present invention, the sodium salt ash solution filtration system includes a filtration device.

[0007] As a further solution of the present invention, the cooling and freezing system includes a cooling and freezing device, a flue gas lithium bromide refrigeration unit, a sodium sulfate collection device, a flue, and a cold water pipe. The flue gas lithium bromide refrigeration unit is connected to the original flue gas flue through the flue, and the flue gas waste heat is used for refrigeration. The cooling and freezing device is connected to the flue gas lithium bromide refrigeration unit through the cold water pipe; As a further solution of the present invention, the mother liquor evaporation system includes a primary mother liquor evaporation device and a primary heat exchanger. The hot water exchanges heat with the flue gas through the primary heat exchanger to increase the temperature, and then provides heat to the primary mother liquor evaporation device.

[0008] As a further solution of the present invention, the crystallization separation system includes a primary separation device and a primary mother liquor collection device. The mother liquor is sent to a sodium ash dissolution tank through a pipeline to recycle the mother liquor.

[0009] As a further scheme of the present invention, the dissolution, cooling and precipitation system includes a dissolution device, a cooling device, a flue gas lithium bromide refrigeration unit, a flue, a cold water pipe, a secondary separation device, and a secondary mother liquor collection device. The flue gas lithium bromide refrigeration unit is connected to the original flue gas flue through the flue, and uses the flue gas waste heat for refrigeration. The cooling device is connected to the flue gas lithium bromide refrigeration unit through a cold water pipe, and the secondary mother liquor collection device sends the secondary mother liquor to the primary mother liquor evaporation device through a pipeline for recycling.

[0010] As a further solution of the present invention, the post-processing system includes an evaporation crystallization device, a separation drying and packaging device, a secondary heat exchanger, a flue, and a hot air pipe. The secondary heat exchanger exchanges the waste heat of the flue gas with the air through the flue to form hot air, which is sent to the separation drying and packaging device through the hot air pipe to evaporate and dry the material.

[0011] As a further solution of the present invention, the evaporation crystallization device can adopt MVR, single-effect evaporation or double-effect evaporation equipment.

[0012] As a further solution of the present invention, the separation, drying and packaging device includes a centrifuge, a dryer and a packaging machine.

[0013] The beneficial effects of the present invention are: The flue gas lithium bromide refrigeration unit utilizes the flue gas waste heat for refrigeration, provides a cold source for the cooling and freezing device and the cooling device, and realizes the preliminary and deep salt separation effect; the primary heat exchanger utilizes the flue gas waste heat to heat the process water, and provides a heat source for the primary mother liquor evaporation device, and realizes the secondary salt separation effect; the secondary heat exchanger utilizes the flue gas waste heat to heat the air, and provides a heat source for the drying device, and realizes the generation of salt separation finished products. The present invention has a simple process, low investment, and low energy consumption, and is worthy of promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a schematic flow chart of a method for treating by-products of flue gas desulfurization by salt separation.

[0015] In the figure: 1. sodium ash dissolving tank; 2. filtering device; 3. cooling and freezing device; 4. flue gas lithium bromide refrigeration unit; 5. sodium sulfate collecting device; 6. primary mother liquor evaporating device; 7. primary separation device; 8. primary mother liquor collecting device; 9. dissolving device; 10. cooling device; 11. secondary separation device; 12. secondary mother liquor collecting device; 13. evaporation and crystallization device; 14. separation, drying and packaging device; 15. secondary heat exchanger; 16. flue; 17. cold water pipe; 18. primary heat exchanger; 19. flue; 20. hot air pipe. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. It should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "setting" should be understood in a broad sense. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0017] Reference Figure 1 A method for treating by-product salt separation of flue gas desulfurization, comprising: a sodium salt ash dissolution system, a sodium salt ash solution filtration system, a cooling and freezing crystallization system, a mother liquor evaporation system, a crystallization separation system, a dissolution cooling and precipitation system, and a post-treatment system. The method makes full use of the waste heat of flue gas for refrigeration and heating, solves the problem that the solubility of sodium sulfate and sodium carbonate is relatively close and it is not easy to separate and precipitate salts, has low operating costs, and converts the desulfurization by-product (sodium salt ash) into sodium sulfate and sodium carbonate finished salts, thereby recycling resources.

[0018] In the present invention, the sodium salt ash dissolution system comprises a sodium ash dissolution tank 1 .

[0019] In the present invention, the sodium salt ash solution filtering system includes a filtering device 2 .

[0020] In the present invention, the cooling and freezing system comprises a cooling and freezing device 3, a flue gas lithium bromide refrigeration unit 4, a sodium sulfate collection device 5, a flue 16, and a cold water pipe 17. The flue gas lithium bromide refrigeration unit 4 is connected to the original flue gas flue through the flue 16, and the flue gas waste heat is used for refrigeration. The cooling and freezing device 3 is connected to the flue gas lithium bromide refrigeration unit 4 through the cold water pipe 17; In the present invention, the mother liquor evaporation system includes a primary mother liquor evaporation device 6 and a primary heat exchanger 18 . The hot water exchanges heat with the flue gas through the primary heat exchanger 18 to increase the temperature, and then provides heat to the primary mother liquor evaporation device 6 .

[0021] In the present invention, the crystallization separation system comprises a primary separation device 7 and a primary mother liquor collection device 8. The mother liquor is sent to the sodium ash dissolution tank 1 through a pipeline, and the mother liquor is recycled.

[0022] In the present invention, the dissolution cooling precipitation system comprises a dissolution device 9, a cooling device 10, a flue gas lithium bromide refrigeration unit 4, a flue 16, a cold water pipe 17, a secondary separation device 11, and a secondary mother liquor collection device 12. The flue gas lithium bromide refrigeration unit 4 is connected to the original flue gas flue through the flue 16, and the flue gas waste heat is used for refrigeration. The cooling device 10 is connected to the flue gas lithium bromide refrigeration unit 4 through the cold water pipe 17. The secondary mother liquor collection device 12 sends the secondary mother liquor to the primary mother liquor evaporation device 6 for recycling through a pipeline.

[0023] In the present invention, the post-processing system includes an evaporation crystallization device 13, a separation drying and packaging device 14, a secondary heat exchanger 15, a flue 19, and a hot air pipe 20. The secondary heat exchanger 15 exchanges the waste heat of the flue gas with the air through the flue 19 to form hot air, which is sent to the separation drying and packaging device 14 through the hot air pipe 20 to evaporate and dry the material.

[0024] In the present invention, the evaporation crystallization device 13 can adopt MVR, single-effect evaporation or double-effect evaporation equipment.

[0025] In the present invention, the separation, drying and packaging device 14 includes a centrifuge, a dryer and a packaging machine.

[0026] Working principle: the sodium salt ash, a by-product of the desulfurization device, and process water enter the sodium ash dissolution tank 1, and the dissolution temperature is controlled at 35°C to form a mixed salt saturated solution. After passing through the filtering device 2, insoluble impurities are removed to form a sodium sulfate alkali salt solution, which is sent to the cooling and freezing device 3 through a pipeline. The flue gas lithium bromide refrigeration unit 4 is connected to the original flue gas flue through the flue 16, and the flue gas waste heat is used for refrigeration. The chilled water of the flue gas lithium bromide refrigeration unit 4 enters the cooling and freezing device 3 through the cold water pipe 17, and the sodium sulfate alkali salt solution is cooled to 0°C. At this time, sodium sulfate (Na2SO4·10H2O) is precipitated and collected by the sodium sulfate collection device 5. The mother liquor after cooling and freezing the sodium sulfate precipitated enters the primary mother liquor evaporation device 6, and the primary heat exchanger 18 is used The process water is heated by flue gas waste heat, and the hot water enters the primary mother liquor evaporation device 6 to heat the mother liquor to 35°C and then enters the primary separation device 7. At this time, a large amount of Na2CO3 + a small amount of Na2SO4 is precipitated. The primary mother liquor collection device 8 sends the mother liquor after crystallization and separation to the sodium ash dissolution tank 1, and the mother liquor is recycled. The precipitated Na2CO3 + Na2SO4 is dissolved in water in the dissolution device 9 until saturated and enters the cooling device 10. The flue gas lithium bromide refrigeration unit 4 is continued to be refrigerated to 20°C, and passes through the secondary separation device 11. At this time, Na2CO3·10H2O is precipitated, and the secondary mother liquor collection device 12 continues to send the secondary mother liquor to the primary mother liquor evaporation device 6 for recycling. Na2CO3·10H2O enters the post-processing system, and the secondary heat exchanger 15 uses the flue gas waste heat to provide drying heat. After passing through the evaporation crystallization device 13 and the separation drying and packaging device 14 in sequence, it forms a finished product Na2CO3 with a purity that meets the standard.

[0027] In this application, structures and connection relationships that are not described in detail are all prior arts, and their structures and principles are well-known technologies and will not be described in detail here.

[0028] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for treating by-products of flue gas desulfurization by salt separation, characterized in that: include: Sodium salt ash dissolution system, sodium salt ash solution filtration system, cooling and freezing crystallization system, mother liquor evaporation system, crystallization separation system, dissolution cooling and precipitation system, and post-processing system.

2. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The sodium salt ash dissolution system comprises a sodium ash dissolution tank (1).

3. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The sodium salt ash solution filtering system comprises a filtering device (2).

4. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The cooling and freezing system comprises a cooling and freezing device (3), a flue gas lithium bromide refrigeration unit (4), a sodium sulfate collection device (5), a flue gas (16), and a cold water pipe (17). The flue gas lithium bromide refrigeration unit (4) is connected to the original flue gas flue via the flue gas (16) to utilize flue gas waste heat for refrigeration. The cooling and freezing device (3) is connected to the flue gas lithium bromide refrigeration unit (4) via the cold water pipe (17).

5. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The mother liquor evaporation system comprises a primary mother liquor evaporation device (6) and a primary heat exchanger (18); hot water exchanges heat with flue gas through the primary heat exchanger (18) to increase the temperature, and then provides heat to the primary mother liquor evaporation device (6).

6. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The crystallization separation system comprises a primary separation device (7) and a primary mother liquor collection device (8); the mother liquor is sent to a sodium ash dissolution tank (1) through a pipeline, and the mother liquor is recycled.

7. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The dissolution, cooling and precipitation system comprises a dissolution device (9), a cooling device (10), a flue gas lithium bromide refrigeration unit (4), a flue (16), a cold water pipe (17), a secondary separation device (11), and a secondary mother liquor collection device (12). The flue gas lithium bromide refrigeration unit (4) is connected to the original flue gas flue through the flue (16) and uses the flue gas waste heat for refrigeration. The cooling device (10) is connected to the flue gas lithium bromide refrigeration unit (4) through the cold water pipe (17). The secondary mother liquor collection device (12) sends the secondary mother liquor to the primary mother liquor evaporation device (6) through a pipeline for recycling.

8. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The post-processing system comprises an evaporation crystallization device (13), a separation drying and packaging device (14), a secondary heat exchanger (15), a flue (19), and a hot air pipe (20). The secondary heat exchanger (15) exchanges the waste heat of the flue gas with air through the flue (19) to form hot air, which is then sent to the separation drying and packaging device (14) through the hot air pipe (20) to evaporate and dry the material.

9. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The evaporation crystallization device (13) may adopt MVR, single-effect evaporation or double-effect evaporation equipment.

10. The method for treating by-products of flue gas desulfurization according to claim 1, characterized in that: The separation, drying and packaging device (14) comprises a centrifuge, a dryer and a packaging machine.

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