A fly ash water washing liquid quality crystallization treatment system

Abstract

The utility model provides a kind of fly ash washing liquid divides quality crystallization processing system.The system includes MVR evaporation system and cooling crystallization system.MVR evaporation system is constituted forced circulation evaporation circuit by heating chamber, separation chamber, vapor compressor etc., for concentrating washing liquid and crystallizing separation out sodium salt.Cooling crystallization system is constituted continuous type "cooling+crystal growing" two-stage crystallization process by cooling tank, cooler, crystal growing tank etc., for further cooling crystallization separation out potassium salt from the concentrated mother liquor of MVR system.The utility model realizes the efficient division quality crystallization and resource of sodium salt and potassium salt in fly ash washing liquid by the optimization coupling of two systems, with the advantages of low energy consumption, strong anti-fouling ability, stable operation, equipment investment, small footprint and high product purity, effectively solve the problems of low processing efficiency, unstable operation and high equipment investment of prior art.

Description

Technical Field

[0001] This utility model relates to wastewater treatment and resource recycling technology, and in particular to a fractional crystallization treatment system for fly ash washing liquid, belonging to the field of environmental governance technology. Background Technology

[0002] Fly ash mainly comes from the powdery substances captured during the purification process of flue gas from municipal solid waste incineration. By the end of 2021, my country's fly ash production had reached more than 10 million tons per year. The municipal solid waste collection and transportation system has been gradually improved, municipal solid waste landfills have been gradually closed, and the volume of municipal solid waste incineration has grown rapidly.

[0003] Fly ash can be exempted from being managed as hazardous waste when co-processed in cement kilns. It is encouraged that fly ash from waste incineration be pre-treated by water washing process when co-processing waste in cement kilns.

[0004] The "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration" (HJ1134-2020) requires that the soluble chlorine content of fly ash after pretreatment should not exceed 2%, and preferably not higher than 1%. The "Technical Specification for Environmental Protection of Solid Waste Co-processing in Cement Kilns" (HJ662-2013) also stipulates that the chlorine content in the materials fed into the kiln should not exceed 0.04%. The solid products after fly ash washing meet the requirements of the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration" (HJ1134-2020). However, in order to ensure normal cement production and that the clinker quality meets national standards, the blending amount in the co-processing process should be controlled below 5%.

[0005] While addressing the issue of solid fly ash disposal, the fly ash washing process generates a large amount of high-salinity scrubbing liquid. This liquid primarily contains high concentrations of sodium chloride and potassium chloride. If these two salts can be effectively separated and purified to industrial-grade standards, a leap from "hazardous waste treatment" to "resource recycling" can be achieved, aligning with the concept of a circular economy.

[0006] For high-salinity wastewater such as fly ash washing liquid, characterized by a sodium chloride concentration higher than potassium chloride, the industry commonly employs a "evaporation crystallization + cooling crystallization" process for salt separation. This approach suffers from drawbacks including small processing capacity, high overall system energy consumption, poor stability during continuous operation, and unstable salt quality. Furthermore, in the cooling crystallization unit, existing technologies such as intermittent cooling crystallization suffer from low efficiency and discontinuous operation; while continuous cooling crystallizers like the Oslo type require large equipment volumes and complex structures, resulting in high investment costs and large footprints. When scaling up processing, multiple crystallizers often need to be connected in parallel, further increasing system complexity and investment costs. Therefore, developing a high-efficiency, stable, energy-saving fly ash washing liquid fractionation crystallization treatment system capable of producing high-purity products is particularly urgent. Utility Model Content

[0007] The purpose of this invention is to address the problems of low treatment efficiency and stability and high equipment investment in current fly ash washing liquid treatment, and to propose a fly ash washing liquid fractional crystallization treatment system. This system can achieve efficient separation of sodium chloride and potassium chloride, increase the processing scale of a single unit, reduce equipment investment, and ensure the energy efficiency and operational stability of the system.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0009] A fly ash washing liquid fractional crystallization treatment system includes an MVR evaporation system and a cooling crystallization system.

[0010] The MVR evaporation system includes a heating chamber, a separation chamber, a heating chamber hot well, a steam compressor, a circulating pump, a sodium salt slurry pump, a sodium salt centrifuge, a sodium salt mother liquor tank, and a sodium salt mother liquor pump.

[0011] The upper side wall of the separation chamber is provided with a liquid inlet for receiving the fly ash washing liquid to be treated;

[0012] The top of the separation chamber is provided with a steam outlet, which is connected to the inlet of the steam compressor. The outlet of the steam compressor is connected to the shell-side inlet of the heating chamber, and the shell-side outlet of the heating chamber is connected to the hot well inlet of the heating chamber.

[0013] The bottom liquid outlet of the separation chamber is divided into two paths: one path is connected to the inlet of the heating chamber tube side through a circulation pump, and the outlet of the heating chamber tube side is connected to the return port of the separation chamber circulating liquid through a pipeline, forming a concentrated liquid circulation loop; the other path is connected to the inlet of the sodium salt centrifuge through a sodium salt slurry pump, the liquid phase outlet of the sodium salt centrifuge is connected to the inlet of the sodium salt mother liquor tank, and the outlet of the sodium salt mother liquor tank is connected to the inlet of the sodium salt mother liquor pump.

[0014] The cooling crystallization system includes a cooling tank, a cooler, a cooling crystallization circulation pump, a circulating water storage tank, a cooling water circulation pump, a potassium salt slurry pump, a crystal growth tank, a potassium salt centrifuge, a potassium salt mother liquor tank, and a potassium salt mother liquor pump.

[0015] The inlet of the cooling tank is connected to the outlet of the sodium salt mother liquor pump and is used to receive concentrated mother liquor from the MVR system.

[0016] The cooling tank outlet is divided into two paths: one path is connected to the inlet of the cooling crystallization circulation pump; the other path is connected to the inlet of the potassium salt slurry pump.

[0017] The outlet of the cooling crystallization circulation pump is connected to the inlet of the cooler tube side, and the outlet of the cooler tube side is connected to the liquid return port of the cooling tank, forming a salt solution cooling circulation loop.

[0018] The outlet of the potassium salt slurry pump is connected to the inlet of the crystal growth tank, the outlet of the crystal growth tank is connected to the inlet of the potassium salt centrifuge, the liquid phase outlet of the potassium salt centrifuge is connected to the inlet of the potassium salt mother liquor tank, and the outlet of the potassium salt mother liquor tank is connected to the inlet of the circulation pump through the potassium salt mother liquor pump to achieve mother liquor reflux. After exchanging heat with the low-temperature incoming liquid in the heating chamber hot well, the distilled water is discharged to the outlet pool.

[0019] Furthermore, the cooler shell-side outlet is connected to the inlet of the circulating water storage tank, and the circulating water storage tank outlet is connected to the cooler shell-side inlet via a cooling water circulation pump, forming a cooling water circulation loop.

[0020] Furthermore, the heating chamber is a horizontal double-pass shell-and-tube heat exchanger, which is beneficial for improving heat transfer efficiency and reducing scaling.

[0021] Furthermore, the steam compressor is a single-stage high-speed centrifugal compressor with a temperature rise of 18-20°C. This temperature rise range can achieve the best energy efficiency balance while ensuring evaporation efficiency.

[0022] Furthermore, the evaporation intensity of the separation chamber is designed to be 0.9-1.2 m³ / (m³·s), which helps to form sodium chloride crystals with uniform particle size and reduce mist entrainment.

[0023] Furthermore, the material entering the sodium salt centrifuge has a visible salt content of 5%-10%. Controlling this feed concentration can ensure that the sodium chloride crystals have good separation effect and high purity.

[0024] Furthermore, the cooler is a vertical single-pass shell-and-tube heat exchanger, which is suitable for cooling crystallization conditions and is easy to manage and maintain.

[0025] Furthermore, the temperature difference between the outlet and inlet of the cooler shell side is controlled at 1℃-2℃. A smaller temperature difference control is conducive to achieving a mild and stable cooling process, promoting the slow growth of potassium chloride crystals, and forming large and uniform crystals.

[0026] Furthermore, the material entering the potassium salt centrifuge can be expected to have a salt content of 20%-30%. Controlling this high concentration of feed can ensure the potassium chloride crystallization rate and system processing efficiency.

[0027] Compared with existing technologies, the fly ash washing liquid fractional crystallization treatment system of this invention has the following advantages:

[0028] 1) The MVR forced circulation evaporation crystallization process is adopted to make full use of the latent heat of secondary steam, which significantly reduces the system energy consumption. At the same time, the forced circulation mode effectively reduces equipment scaling and clogging, ensuring the stability and reliability of the system in long-term operation.

[0029] 2) The cooling and crystallization process adopts a continuous operation mode, which, compared with the intermittent process, enables continuous feeding and discharging of materials, greatly improving the overall processing efficiency and capacity of the crystallization system.

[0030] 3) The cooling crystallization system adopts a two-stage process of "cooling + crystal growth", which is a key optimization of the traditional integrated crystallizer. Cooling and crystal growth operate independently under their respective optimal working conditions, which greatly reduces the volume of the crystal growth tank. This not only solves the inherent problems of traditional equipment in terms of operational stability and product quality, but also significantly reduces equipment investment and floor space. Attached Figure Description

[0031] Figure 1 Process flow diagram of the fly ash washing liquid fractionation crystallization treatment system.

[0032] 1-Heating chamber; 2-Separation chamber; 3-Heating chamber hot well; 4-Steam compressor; 5-Circulating pump; 6-Sodium salt slurry pump; 7-Sodium salt centrifuge; 8-Sodium salt mother liquor tank; 9-Sodium salt mother liquor pump; 10-Cooling tank; 11-Cooler; 12-Cooling crystallization circulating pump; 13-Circulating water temporary storage tank; 14-Cooling water circulating pump; 15-Potassium salt slurry pump; 16-Crystallization tank; 17-Potassium salt centrifuge; 18-Potassium salt mother liquor tank; 19-Potassium salt mother liquor pump. Detailed Implementation

[0033] The present invention will be further described below with reference to the embodiments:

[0034] Example

[0035] As attached Figure 1 As shown, the fly ash washing liquid fractional crystallization treatment system provided by the present invention mainly consists of two parts: an MVR evaporation system and a cooling crystallization system.

[0036] The MVR evaporation system includes a heating chamber 1, a separation chamber 2, a heating chamber hot well 3, a steam compressor 4, a circulation pump 5, a sodium salt slurry pump 6, a sodium salt centrifuge 7, a sodium salt mother liquor tank 8, and a sodium salt mother liquor pump 9.

[0037] The upper sidewall of the separation chamber 2 is provided with an inlet for fly ash washing liquid from outside the system. The top of the separation chamber 2 is provided with a steam outlet, which connects to the inlet of the steam compressor 4. The outlet of the steam compressor 4 connects to the shell-side inlet of the heating chamber 1, and the shell-side outlet of the heating chamber 1 connects to the inlet of the heating chamber hot well 3. The steam compressor 4 compresses the secondary steam generated in the separation chamber 2 and sends it to the shell side of the heating chamber 1 as a heat source to heat the tube-side material. In this embodiment, the heating chamber 1 uses a horizontal double-pass shell-and-tube heat exchanger, and the steam compressor 4 uses a single-stage high-speed centrifugal compressor with the compressor temperature rise controlled at 18-20℃. The evaporation intensity of the separation chamber 2 is 0.9-1.2 m³ / (m³·s), which helps to form uniformly sized sodium chloride crystals and reduces mist entrainment.

[0038] The bottom liquid outlet of separation chamber 2 is divided into two paths: the first path connects to the inlet of circulation pump 5, the outlet of circulation pump 5 connects to the tube-side inlet of heating chamber 1, and the tube-side outlet of heating chamber 1 connects to the circulating liquid return port of separation chamber 2, allowing the material to circulate forcibly between the tube-side of separation chamber 2 and heating chamber 1 via circulation pump 5; the second path connects to the inlet of sodium salt slurry pump 6, the outlet of sodium salt slurry pump 6 connects to the inlet of sodium salt centrifuge 7, the liquid phase outlet of the dehydration system of sodium salt centrifuge 7 connects to the inlet of sodium salt mother liquor tank 8, and the outlet of sodium salt mother liquor tank 8 connects to the inlet of sodium salt mother liquor pump 9, sending the concentrated mother liquor after centrifugal separation of sodium salt into the cooling crystallization system. In this embodiment, the feed to the dehydration system of sodium salt centrifuge 7 can be 5-10% salt content.

[0039] The cooling crystallization system includes a cooling tank 10, a cooler 11, a cooling crystallization circulation pump 12, a circulating water storage tank 13, a cooling water circulation pump 14, a potassium salt slurry pump 15, a crystal growth tank 16, a potassium salt centrifuge 17, a potassium salt mother liquor tank 18, and a potassium salt mother liquor pump 19.

[0040] The inlet of cooling tank 10 is connected to the outlet of sodium salt mother liquor pump 9 to receive concentrated mother liquor from the MVR system; the outlet of cooling tank 10 is divided into two paths: one path is connected to the inlet of cooling crystallization circulation pump 12; the other path is connected to the inlet of potassium salt slurry pump 15; the outlet of cooling crystallization circulation pump 12 is connected to the tube-side inlet of cooler 11, and the tube-side outlet of cooler 11 is connected to the liquid return port of cooling tank 10, forming a material cooling circulation loop; the shell-side inlet of cooler 11 is connected to the outlet of cooling water circulation pump 14, and the shell-side outlet of cooler 11 is connected to the inlet of circulating water storage tank 13, and the outlet of circulating water storage tank 13 is connected to the inlet of cooling water circulation pump 14, forming a cooling water circulation loop; in this embodiment, cooler 11 adopts a vertical single-tube shell-and-tube heat exchanger, and cooling water circulation pump 14 adopts a high-flow circulation pump to control the temperature difference between the inlet and outlet of cooling water in the shell side of cooler 11 at 1-2℃.

[0041] The outlet of the potassium salt slurry pump 15 is connected to the inlet of the crystal growth tank 16, the outlet of the crystal growth tank 16 is connected to the inlet of the potassium salt centrifuge 17, the liquid phase outlet of the dehydration system of the potassium salt centrifuge 17 is connected to the inlet of the potassium salt mother liquor tank 18, the outlet of the potassium salt mother liquor tank 18 is connected to the inlet of the potassium salt mother liquor pump 19, and the outlet of the potassium salt mother liquor pump 19 is connected to the inlet of the circulation pump 5 of the MVR evaporation system, realizing mother liquor reflux. In this embodiment, the apparent salt content of the feed to the dehydration system of the potassium salt centrifuge 17 is 20-30%.

[0042] The system described in this invention achieves efficient separation and resource utilization of sodium and potassium salts in fly ash washing liquid through the ingenious coupling of two-stage crystallization. Furthermore, it achieves energy conservation, consumption reduction, and stable operation through the recycling of energy and materials.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A fractional crystallization treatment system for fly ash washing liquid, characterized in that, include: MVR evaporation system and cooling crystallization system: The MVR evaporation system includes a heating chamber (1), a separation chamber (2), a heating chamber hot well (3), a steam compressor (4), a circulation pump (5), a sodium salt slurry pump (6), a sodium salt centrifuge (7), a sodium salt mother liquor tank (8), and a sodium salt mother liquor pump (9). The upper shell side wall of the separation chamber (2) is provided with a liquid inlet; The top shell of the separation chamber (2) is provided with a steam outlet, which is connected to the shell-side inlet of the heating chamber (1) through a steam compressor (4), and the shell-side outlet of the heating chamber (1) is connected to the inlet of the heating chamber hot well (3); The liquid outlet at the bottom of the separation chamber (2) is divided into two paths: one path is connected to the inlet of the heating chamber (1) via the circulating pump (5), and the outlet of the heating chamber (1) via the circulating liquid return port of the separation chamber (2); the other path is connected to the inlet of the sodium salt centrifuge (7) via the sodium salt slurry pump (6), the liquid phase outlet of the sodium salt centrifuge (7) is connected to the inlet of the sodium salt mother liquor tank (8), and the outlet of the sodium salt mother liquor tank (8) is connected to the inlet of the sodium salt mother liquor pump (9). The cooling crystallization system includes a cooling tank (10), a cooler (11), a cooling crystallization circulation pump (12), a circulating water storage tank (13), a cooling water circulation pump (14), a potassium salt slurry pump (15), a crystal growth tank (16), a potassium salt centrifuge (17), a potassium salt mother liquor tank (18), and a potassium salt mother liquor pump (19). The inlet of the cooling tank (10) is connected to the outlet of the sodium salt mother liquor pump (9); The outlet of the cooling tank (10) is divided into two paths: one path is connected to the inlet of the cooling crystallization circulation pump (12); the other path is connected to the inlet of the potassium salt slurry pump (15). The outlet of the cooling crystallization circulation pump (12) is connected to the inlet of the tube side of the cooler (11), and the outlet of the tube side of the cooler (11) is connected to the liquid return port of the cooling tank (10). The outlet of the potassium salt slurry pump (15) is connected to the inlet of the crystal growth tank (16), the outlet of the crystal growth tank (16) is connected to the inlet of the potassium salt centrifuge (17), the liquid phase outlet of the potassium salt centrifuge (17) is connected to the inlet of the potassium salt mother liquor tank (18), and the outlet of the potassium salt mother liquor tank (18) is connected to the inlet of the circulating pump (5) through the potassium salt mother liquor pump (19).

2. The fly ash washing liquid fractional crystallization treatment system according to claim 1, characterized in that, The shell-side outlet of the cooler (11) is connected to the inlet of the circulating water storage tank (13), and the outlet of the circulating water storage tank (13) is connected to the shell-side inlet of the cooler (11) through the cooling water circulation pump (14).

3. The fly ash washing liquid fractional crystallization treatment system according to claim 1, characterized in that, The heating chamber (1) is a horizontal double-pass shell-and-tube heat exchanger.

4. The fly ash washing liquid fractional crystallization treatment system according to claim 1, characterized in that, The steam compressor (4) is a single-stage high-speed centrifugal compressor.

5. The fly ash washing liquid fractional crystallization treatment system according to claim 1, characterized in that, The cooler (11) is a vertical single-pass tubular heat exchanger.

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