System and method for treating and recycling waste incineration fly ash washing wastewater

Abstract

This invention provides a system for the treatment and reuse of wastewater from the washing of fly ash from waste incineration. The system comprises a conditioning and preheating device, a first-effect evaporation unit, a second-effect evaporation unit, a third-effect evaporation unit, a parallel first-effect evaporation unit, a calcium chloride precipitation unit, a potassium chloride precipitation unit, a sodium chloride precipitation unit, and a vacuum device. The various devices and units work synergistically, and with the accompanying methods, not only can engineering construction investment be reduced by 30%-40%, but the overall production and operating costs can also be reduced by approximately 30%. Furthermore, it can fully achieve the effective treatment of wastewater and the comprehensive recycling of all resources, resulting in significant social, environmental, and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, and in particular to a system and method for treating and reusing wastewater from waste incineration fly ash washing. Background Technology

[0002] In current wastewater treatment for fly ash washing from waste incineration, a common process involves multi-effect evaporation or single-effect evaporation combined with centrifugal separation to concentrate and crystallize mixed brine containing high concentrations of sodium chloride, potassium chloride, and calcium chloride. A typical process involves conditioning the pretreated fly ash washing liquid with alkali, then feeding it into a multi-effect evaporator for initial concentration to obtain a mixed brine slurry containing the three salts. Subsequently, sodium chloride and potassium chloride are separated through dissolution and re-evaporation, and the crystals are collected using a centrifuge. This type of process has been widely applied in the resource utilization of oil and gas field wastewater and other high-salinity wastewater, aiming to achieve "zero discharge" and recover industrial salt products.

[0003] However, existing technologies still face several key challenges. Firstly, fly ash washing wastewater has a complex composition, with extremely high concentrations of sodium chloride, potassium chloride, and calcium chloride. Existing evaporation-dissolution-re-evaporation pathways struggle to achieve high-purity separation and fractional crystallization of these three salts, resulting in a final product that is often a mixed salt, limiting resource utilization. Secondly, conventional evaporation processes have low steam utilization rates and lack efficient cascade utilization of secondary steam and waste heat preheating mechanisms, leading to persistently high energy consumption when treating high-salinity wastewater. These shortcomings result in significant deficiencies in the existing processes regarding economics, energy consumption, product quality, and wastewater treatment. Summary of the Invention

[0004] To overcome the problems existing in related technologies, one of the objectives of this invention is to provide a system and method for the treatment and reuse of wastewater from waste incineration fly ash washing. This system and method exhibit excellent performance in terms of economy, energy consumption, product quality, and wastewater terminal treatment.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A system for treating and reusing wastewater from fly ash washing in waste incineration includes a conditioning and preheating device, a first-effect evaporation unit, a second-effect evaporation unit, a third-effect evaporation unit, a parallel first-effect evaporation unit, a calcium chloride precipitation unit, a potassium chloride precipitation unit, a sodium chloride precipitation unit, and a vacuum device. The first-effect evaporation unit, second-effect evaporation unit, and third-effect evaporation unit are connected sequentially. The slurry pipeline is configured in a co-current direction from the first-effect evaporation unit to the third-effect evaporation unit, and the parallel first-effect evaporation unit is connected to the second-effect evaporation unit within the slurry pipeline. The raw material pipeline is configured in a counter-current direction from the third-effect evaporation unit to the first-effect evaporation unit, and the parallel first-effect evaporation unit is connected to the first-effect evaporation unit within the raw material pipeline. The calcium chloride precipitation unit is connected to the parallel first-effect evaporation unit, the sodium chloride precipitation unit is connected to the third-effect evaporation unit, and the vacuum device is connected to the third-effect evaporation unit and regulates the internal pressure of the third-effect evaporation unit.

[0006] Furthermore, the conditioning and preheating device consists of a conditioning tank and a preheater, and the conditioning tank is connected to the triple-effect evaporation unit through the preheater.

[0007] Furthermore, the first-effect evaporation unit consists of a first-effect evaporation vessel, a first-stage flash evaporation vessel, a second-stage flash evaporation vessel, and a cooling crystallization vessel connected in sequence. The first-effect evaporation vessel is connected to the first-effect evaporation unit, and the cooling crystallization vessel is connected to the parallel first-effect evaporation unit and the potassium chloride precipitation unit, respectively.

[0008] Furthermore, the calcium chloride precipitation unit consists of an atomizing pump and a spray granulator, and the spray granulator is connected to a parallel single-effect evaporation unit via the atomizing pump.

[0009] Furthermore, the potassium chloride precipitation unit consists of a first washing machine and a first centrifuge, and the first centrifuge is connected to a first-effect evaporation unit through the first washing machine.

[0010] Furthermore, the sodium chloride precipitation unit consists of a second washing machine and a second centrifuge, with the second centrifuge connected to the triple-effect evaporation unit via the second washing machine.

[0011] The second objective of this invention is to provide a method for treating and reusing wastewater from waste incineration fly ash washing, comprising the following steps: Step 1: Wastewater conditioning. The pretreated wastewater from the incineration fly ash washing process is conditioned and preheated in conditioning and preheating device 1 with alkali to obtain raw brine. Step 2: The raw brine is fed into a triple-effect evaporation unit. After evaporation, the raw material is passed through a raw material pipeline to a double-effect evaporation unit for evaporation, then to a first-effect evaporation unit for evaporation followed by flash evaporation and cooling. It then enters a parallel first-effect evaporation unit for further evaporation, and finally passes through a calcium chloride precipitation unit to obtain anhydrous calcium chloride. The salt slurry obtained from evaporation in the first, second, and third-effect evaporation units is passed through a salt slurry pipeline to a first, second, and third-effect evaporation unit for evaporation, and then passes through a sodium chloride precipitation unit to obtain sodium chloride. The raw material flashes and cools as it passes through the first-effect evaporation unit to obtain salt slurry, which then passes through a potassium chloride precipitation unit to obtain wet potassium chloride.

[0012] Preferably, the alkali conditioning process in step one involves setting the pH to 8.0-8.5 and the preheating process involves setting the temperature to 60°C.

[0013] Preferably, in step two, the potassium chloride content in the material in the first-effect evaporation unit is 130-150 g / L, and the operating pressure in the third-effect evaporation unit is no greater than 12 kPa.

[0014] Preferably, the calcium chloride content in the salt slurry obtained after evaporation in the parallel single-effect evaporation unit in step two is 35% to 45%, and the operating temperature of the calcium chloride precipitation unit is 400-500℃.

[0015] The beneficial effects of this invention are as follows: Significant economic benefits: Compared with the traditional two-step process for producing sodium chloride and potassium chloride, this method can reduce production and operating costs by about 40% and save more than 30% on project construction investment, demonstrating its significant economic value.

[0016] Significant social and environmental benefits: This technology effectively treats wastewater while achieving comprehensive recycling of all resources; its comprehensive production energy consumption can achieve energy savings (steam and electricity) of about 30% compared with the two-step method, with significant energy saving and carbon reduction effects, and has high social and environmental benefits.

[0017] High resource utilization rate and environmentally friendly: It realizes the complete recycling of chemical raw materials contained in the wastewater from fly ash washing in waste incineration, with a recovery rate of over 99% for each chemical raw material, eliminating the pollution problems that may be caused to the environment by fly ash landfill or simple wastewater treatment and discharge.

[0018] Low energy consumption: The extraction of sodium chloride and potassium chloride can reduce the overall energy consumption by about 40% compared with the traditional two-step method; the extraction of anhydrous calcium chloride will reduce the power consumption by about 15%.

[0019] The entire system has a simple process and high stability: The "one-step method" adopted by this technology has a shorter process flow and fewer control points than the traditional "two-step method". The entire system has a simpler process, higher system stability, and is easier to operate. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a system for treating and reusing wastewater from waste incineration fly ash washing, as described in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the conditioning and preheating device in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a single-effect evaporation unit in an embodiment of the present invention; Figure 4 This is a schematic diagram of the calcium chloride precipitation unit in an embodiment of the present invention; Figure 5 This is a schematic diagram of the potassium chloride precipitation unit in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the sodium chloride precipitation unit in an embodiment of the present invention; Figure 7 This is a process flow diagram of a method for treating and reusing wastewater from waste incineration fly ash washing in an embodiment of the present invention, wherein the solid line represents the calcium chloride preparation process, the dashed line represents the sodium chloride preparation process, and the dotted line represents the potassium chloride preparation process.

[0021] Figure label: 1. Conditioning and preheating device; 11. Conditioning tank; 12. Preheater; 2. First-effect evaporation unit; 21. First-effect evaporation kettle; 22. First-stage flash evaporation kettle; 23. Second-stage flash evaporation kettle; 24. Cooling crystallization kettle; 3. Second-effect evaporation unit; 4. Third-effect evaporation unit; 5. Parallel first-effect evaporation unit; 6. Calcium chloride precipitation unit; 61. Atomizing pump; 62. Spray granulator; 7. Potassium chloride precipitation unit; 71. First washer; 72. First centrifuge; 8. Sodium chloride precipitation unit; 81. Second washer; 82. Second centrifuge; 9. Vacuum device. Detailed Implementation

[0022] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0023] Example 1 See Figure 1This embodiment provides a system for treating and reusing wastewater from waste incineration fly ash washing, including a conditioning and preheating device 1, a first-effect evaporation unit 2, a second-effect evaporation unit 3, a third-effect evaporation unit 4, a parallel first-effect evaporation unit 5, a calcium chloride precipitation unit 6, a potassium chloride precipitation unit 7, a sodium chloride precipitation unit 8, and a vacuum device 9. The first-effect evaporation unit 2, the second-effect evaporation unit 3, and the third-effect evaporation unit 4 are connected sequentially. The slurry pipeline is configured to flow in the forward direction from the first-effect evaporation unit 2 to the third-effect evaporation unit 4, and the parallel first-effect evaporation unit 5 is connected to the second-effect evaporation unit 3 in the slurry pipeline. The raw material pipeline is configured to flow in the counter-current direction from the third-effect evaporation unit 4 to the first-effect evaporation unit 2, and the parallel first-effect evaporation unit 5 is connected to the first-effect evaporation unit 2 in the raw material pipeline. The calcium chloride precipitation unit 6 is connected to the parallel first-effect evaporation unit 5, the sodium chloride precipitation unit 8 is connected to the third-effect evaporation unit 4, and the vacuum device 9 is connected to the third-effect evaporation unit 4 and regulates the internal pressure of the third-effect evaporation unit 4.

[0024] See Figure 1 and Figure 2 The conditioning and preheating device 1 consists of a conditioning tank 11 and a preheater 12. The conditioning tank 11 is connected to the triple-effect evaporation unit 4 through the preheater 12.

[0025] See Figure 1 and Figure 3 The first-effect evaporation unit 2 is composed of a first-effect evaporation vessel 21, a first-stage flash evaporation vessel 22, a second-stage flash evaporation vessel 23 and a cooling crystallization vessel 24 connected in sequence. The first-effect evaporation vessel 21 is connected to the first-effect evaporation unit 2, and the cooling crystallization vessel 24 is connected to the parallel first-effect evaporation unit 5 and the potassium chloride precipitation unit 7, respectively.

[0026] See Figure 1 and Figure 4 The calcium chloride precipitation unit 6 consists of an atomizing pump 61 and a spray granulator 62. The spray granulator 62 is connected to the parallel single-effect evaporation unit 5 through the atomizing pump 61.

[0027] See Figure 1 and Figure 5 The potassium chloride precipitation unit 7 consists of a first washing machine 71 and a first centrifuge 72. The first centrifuge 72 is connected to the first-effect evaporation unit 2 through the first washing machine 71.

[0028] See Figure 1 and Figure 6 The sodium chloride precipitation unit 8 consists of a second washing machine 81 and a second centrifuge 82. The second centrifuge 82 is connected to the triple-effect evaporation unit 4 through the second washing machine 81.

[0029] Example 2 See Figure 7A method for treating and reusing wastewater from waste incineration fly ash washing includes the following steps: Step 1: Wastewater conditioning. The pretreated wastewater from the incineration fly ash washing process is conditioned with alkali in conditioning and preheating device 1 until the pH is equal to 8.0, and then preheated to 60°C to obtain raw material brine. Step 2: The raw brine is fed into the triple-effect evaporation unit 4, which operates at a pressure of 12 kPa. The raw material obtained after evaporation passes through the raw material pipeline sequentially through the second-effect evaporation unit 3 for evaporation, and then through the first-effect evaporation unit 2 for evaporation followed by flash evaporation and cooling. At this point, the potassium chloride content in the material in the first-effect evaporation unit 2 is 130 g / L. The material then enters the parallel first-effect evaporation unit 5 for further evaporation. The calcium chloride content in the salt slurry obtained after evaporation in the parallel first-effect evaporation unit 5 is 35%. The slurry then passes through the calcium chloride precipitation unit 6 at a working temperature of 400°C to obtain anhydrous calcium chloride. The salt slurry obtained after evaporation in the first-effect evaporation unit 2, the second-effect evaporation unit 3, and the third-effect evaporation unit 4 passes through the salt slurry pipeline sequentially through the first-effect evaporation unit 2, the second-effect evaporation unit 3, and the third-effect evaporation unit 4, and then through the sodium chloride precipitation unit 8 to obtain sodium chloride. The raw material flashes and cools as it passes through the first-effect evaporation unit 2, and the resulting salt slurry passes through the potassium chloride precipitation unit 7 to obtain wet potassium chloride.

[0030] Example 3 See Figure 7 A method for treating and reusing wastewater from waste incineration fly ash washing includes the following steps: Step 1: Wastewater conditioning. The pretreated wastewater from the incineration fly ash washing process is conditioned with alkali in conditioning and preheating device 1 until the pH reaches 8.25, and then preheated to 60°C to obtain raw material brine. Step 2: The raw brine is fed into the triple-effect evaporation unit 4, which operates at a pressure of 12 kPa. The raw material obtained after evaporation passes through the raw material pipeline sequentially through the second-effect evaporation unit 3 for evaporation, and then through the first-effect evaporation unit 2 for evaporation followed by flash evaporation and cooling. At this point, the potassium chloride content in the material in the first-effect evaporation unit 2 is 140 g / L. The material then enters the parallel first-effect evaporation unit 5 for further evaporation. The calcium chloride content in the salt slurry obtained after evaporation in the parallel first-effect evaporation unit 5 is 40%. The slurry then passes through the calcium chloride precipitation unit 6 at a working temperature of 450°C to obtain anhydrous calcium chloride. The salt slurry obtained after evaporation in the first-effect evaporation unit 2, the second-effect evaporation unit 3, and the third-effect evaporation unit 4 passes through the salt slurry pipeline sequentially through the first-effect evaporation unit 2, the second-effect evaporation unit 3, and the third-effect evaporation unit 4, and then through the sodium chloride precipitation unit 8 to obtain sodium chloride. The raw material flashes and cools as it passes through the first-effect evaporation unit 2, and the resulting salt slurry passes through the potassium chloride precipitation unit 7 to obtain wet potassium chloride.

[0031] Example 4 See Figure 7A method for treating and reusing wastewater from waste incineration fly ash washing includes the following steps: Step 1: Wastewater conditioning. The pretreated wastewater from the incineration fly ash washing process is conditioned with alkali in conditioning and preheating device 1 until the pH is equal to 8.5, and then preheated to 60°C to obtain raw material brine. Step 2: The raw brine is fed into the triple-effect evaporation unit 4, which operates at a pressure of 12 kPa. The raw material obtained after evaporation passes through the raw material pipeline sequentially through the second-effect evaporation unit 3 for evaporation, and then through the first-effect evaporation unit 2 for evaporation followed by flash evaporation and cooling. At this point, the potassium chloride content in the material in the first-effect evaporation unit 2 is 150 g / L. The material then enters the parallel first-effect evaporation unit 5 for further evaporation. The calcium chloride content in the salt slurry obtained after evaporation in the parallel first-effect evaporation unit 5 is 45%. The slurry then passes through the calcium chloride precipitation unit 6, which operates at a temperature of 600°C, to obtain anhydrous calcium chloride. The salt slurry obtained after evaporation in the first-effect evaporation unit 2, the second-effect evaporation unit 3, and the third-effect evaporation unit 4 passes through the salt slurry pipeline sequentially through the first-effect evaporation unit 2, the second-effect evaporation unit 3, and the third-effect evaporation unit 4, and then through the sodium chloride precipitation unit 8 to obtain sodium chloride. The raw material flashes and cools as it passes through the first-effect evaporation unit 2, and the resulting salt slurry passes through the potassium chloride precipitation unit 7 to obtain wet potassium chloride.

[0032] This invention provides a method for treating and reusing wastewater from waste incineration fly ash washing. It innovatively employs a one-step method to precisely extract sodium chloride, potassium chloride, and calcium chloride from a quaternary aqueous solution. Compared to the traditional two-step extraction process, this eliminates the secondary dissolution and re-evaporation separation of the potassium and sodium mixed salts, significantly reducing the overall system's steam (thermal energy) and electrical energy consumption. Furthermore, it innovatively combines evaporation desalination and deep concentration of the calcium chloride solution into a single evaporation system, resulting in a simpler process, easier operation, and lower costs; thus significantly reducing project construction investment.

[0033] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figure to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figure. For example, if the device in the figure is inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0034] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for treating and reusing wastewater from waste incineration fly ash washing, characterized in that, The system includes a conditioning and preheating device (1), a first-effect evaporation unit (2), a second-effect evaporation unit (3), a third-effect evaporation unit (4), a parallel first-effect evaporation unit (5), a calcium chloride precipitation unit (6), a potassium chloride precipitation unit (7), a sodium chloride precipitation unit (8), and a vacuum device (9). The first-effect evaporation unit (2), the second-effect evaporation unit (3), and the third-effect evaporation unit (4) are connected in sequence. The salt slurry pipeline is configured in a co-current direction from the first-effect evaporation unit (2) to the third-effect evaporation unit (4), and the salt slurry pipeline contains... The parallel first-effect evaporation unit (5) is connected to the second-effect evaporation unit (3); its raw material pipeline is configured to flow in the counter-current direction from the third-effect evaporation unit (4) to the first-effect evaporation unit (2), and the parallel first-effect evaporation unit (5) is connected to the first-effect evaporation unit (2) in the raw material pipeline, the calcium chloride precipitation unit (6) is connected to the parallel first-effect evaporation unit (5), the sodium chloride precipitation unit (8) is connected to the third-effect evaporation unit (4), and the vacuum device (9) is connected to the third-effect evaporation unit (4) and regulates the internal pressure of the third-effect evaporation unit (4).

2. The system according to claim 1, characterized in that, The conditioning and preheating device (1) consists of a conditioning tank (11) and a preheater (12). The conditioning tank (11) is connected to the triple-effect evaporation unit (4) through the preheater (12).

3. The system according to claim 1, characterized in that, The first-effect evaporation unit (2) consists of a first-effect evaporation kettle (21), a first-stage flash evaporation kettle (22), a second-stage flash evaporation kettle (23), and a cooling crystallization kettle (24) connected in sequence. The first-effect evaporation kettle (21) is connected to the first-effect evaporation unit (2), and the cooling crystallization kettle (24) is connected to the parallel first-effect evaporation unit (5) and the potassium chloride precipitation unit (7), respectively.

4. The system according to claim 1, characterized in that, The calcium chloride precipitation unit (6) consists of an atomizing pump (61) and a spray granulator (62), and the spray granulator (62) is connected to the parallel single-effect evaporation unit (5) through the atomizing pump (61).

5. The system according to claim 1, characterized in that, The potassium chloride precipitation unit (7) consists of a first washing machine (71) and a first centrifuge (72), and the first centrifuge (72) is connected to the first-effect evaporation unit (2) through the first washing machine (71).

6. The system according to claim 1, characterized in that, The sodium chloride precipitation unit (8) consists of a second washing machine (81) and a second centrifuge (82), and the second centrifuge (82) is connected to the triple-effect evaporation unit (4) through the second washing machine (81).

7. A method for treating and reusing wastewater from waste incineration fly ash washing, characterized in that, Includes the following steps: Step 1: Wastewater conditioning. The pretreated wastewater from the fly ash washing process is conditioned and preheated in a conditioning and preheating device (1) with alkali to obtain raw brine. Step 2: The raw material brine is fed into the triple-effect evaporation unit (4). The raw material obtained after evaporation is passed through the raw material pipeline in sequence through the double-effect evaporation unit (3) and the first-effect evaporation unit (2) for evaporation, flashing and cooling. It then enters the parallel first-effect evaporation unit (5) for evaporation and passes through the calcium chloride precipitation unit (6) to obtain anhydrous calcium chloride. The salt slurry obtained after evaporation in the first-effect evaporation unit (2), the second-effect evaporation unit (3) and the triple-effect evaporation unit (4) is passed through the salt slurry pipeline in sequence through the first-effect evaporation unit (2), the second-effect evaporation unit (3) and the triple-effect evaporation unit (4) and then passes through the sodium chloride precipitation unit (8) to obtain sodium chloride. When the raw material passes through the raw material pipeline through the first-effect evaporation unit (2) for flashing and cooling, the resulting salt slurry passes through the potassium chloride precipitation unit (7) to obtain wet potassium chloride.

8. The method according to claim 7, characterized in that, In step one, the alkali conditioning process conditions are a pH of 8.0-8.5 and a preheating process conditions of 60°C.

9. The method according to claim 7, characterized in that, In step two, the potassium chloride content in the material in the first-effect evaporation unit (2) is 130-150 g / L, and the operating pressure in the third-effect evaporation unit (4) is no more than 12 kPa.

10. The method according to claim 7, characterized in that, The calcium chloride content in the salt slurry obtained after evaporation in the parallel single-effect evaporation unit (5) in step two is 35% to 45%, and the working temperature of the calcium chloride precipitation unit (6) is 400-500℃.

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