Triple-effect evaporation system

Abstract

The utility model discloses a triple-effect evaporation system which comprises a first-effect separator, a first first-effect evaporator, a second first-effect evaporator, a second-effect separator, a second-effect evaporator, a third-effect separator and a third-effect evaporator. A circulation port of the first-effect separator is connected with a liquid inlet of the first first-effect evaporator through a circulation pipeline, and a liquid outlet of the first first-effect evaporator is connected with a liquid return port of the first-effect separator through a circulation pipeline; liquid outlets of the first-effect separator, the second-effect separator and the third-effect separator are respectively provided with a liquid outlet pump, and circulating ports of the first-effect separator, the second-effect separator and the third-effect separator are respectively provided with a circulating pump; an outlet of a circulating pump of the first-effect separator is connected with a liquid inlet of a second first-effect evaporator through a standby circulating pipeline, and a liquid outlet of the second first-effect evaporator is connected with a liquid return opening of the first-effect separator through a standby circulating pipeline; and the first single-effect evaporator and the second single-effect evaporator are respectively provided with a steam inlet. According to the utility model, the tube nest cleaning of the non-stop single-effect evaporator is realized, the production continuity can be kept, and the productivity is improved.

Description

Technical Field

[0001] This utility model belongs to the field of hydrometallurgical technology, specifically relating to a triple-effect evaporation system. Background Technology

[0002] With the widespread application of rare earth functional materials in high-tech fields, domestic rare earth enterprises generally use concentrated sulfuric acid roasting to process rare earth concentrates. This produces a mixed sulfuric acid rare earth solution, which is then converted through ammonia saponification, generating rare earth chloride solution and a large amount of ammonium sulfate wastewater. Besides ammonium sulfate, this wastewater also contains impurity ions such as calcium, magnesium, chloride, and fluorine. Common ammonium sulfate wastewater treatment processes mainly employ pretreatment, membrane treatment, MVR (Medium-Voltage Reduction), and triple-effect evaporators to achieve "zero discharge." Due to the influence of upstream processes, even after hardening treatment, the ammonium sulfate wastewater still contains high levels of impurity ions such as calcium, magnesium, sulfate, and oxalate. As the concentration of the mother liquor increases, calcium, magnesium, and silicon ions easily combine with sulfate and oxalate ions in the triple-effect evaporator to form scale, clogging the tubes. Since the first effect has the highest temperature in the triple-effect evaporation process, the clogging of the first-effect evaporator is most severe. The evaporation system, often the final step in the crystallization process, is affected by impurity ions such as calcium, magnesium, sulfate, oxalate, and silicon ions in the wastewater, resulting in severe scaling and corrosion of the equipment. Especially in the first-effect evaporation system of a triple-effect evaporator, the highest temperature causes severe blockage of the tubes, requiring frequent shutdowns for tube cleaning, which disrupts continuous production.

[0003] Commonly used methods to delay scaling include:

[0004] Method 1: Use scale inhibitors.

[0005] Increasing the supersaturation of the feed solution and forming a smooth protective film on the tube surface prevents scale formation. When the concentration of scale ions in the feed solution is too high, the scale inhibitor is basically ineffective, requiring continuous addition of the agent, which is costly.

[0006] Method 2: Perform regular cleaning of the tubes.

[0007] When the flow rate of the evaporator tubes is insufficient and the system pressure rises, it is necessary to shut down the system for high-pressure tube cleaning. After high-pressure cleaning, the tubes can be restored to their original state. However, high-pressure cleaning requires a system shutdown. Depending on the degree of tube blockage, each high-pressure cleaning requires a shutdown of 2-4 days. The shutdown period will seriously affect production operations and cause huge energy waste during start-up and shutdown. Therefore, it is necessary to choose a method for high-pressure tube cleaning without shutting down the system to improve production efficiency.

[0008] Research has revealed that during the evaporation of ammonium sulfate wastewater in a triple-effect evaporator, the scale deposits in each evaporator are different. The scale deposits in the first-effect evaporator are mainly calcium oxalate and magnesium oxalate, while those in the second and third-effect evaporators are mainly ammonium sulfate crystals. Therefore, the scale deposits in the first-effect evaporator are the most severe and the cleaning is the most difficult.

[0009] Therefore, a measure needs to be provided in the triple-effect evaporation system to avoid performing the cleaning of the first-effect tubes under shutdown conditions. Utility Model Content

[0010] The purpose of this invention is to provide a triple-effect evaporation system that enables tube cleaning of the single-effect evaporator without stopping production, thus maintaining continuous production and increasing capacity.

[0011] The technical solution is as follows:

[0012] A triple-effect evaporation system includes: a first-effect separator, a first-effect evaporator, a second-effect evaporator, a second-effect separator, a second-effect evaporator, a third-effect separator, and a third-effect evaporator. The circulation port of the first-effect separator is connected to the inlet of the first-effect evaporator via a circulation pipe, and the outlet of the first-effect evaporator is connected to the return port of the first-effect separator via a circulation pipe. The outlet of the first-effect separator is connected to the inlet of the second-effect separator via a separation pipe, and the circulation port of the second-effect separator is connected to the inlet of the second-effect evaporator via a circulation pipe. The outlet of the second-effect evaporator is connected to the return port of the second-effect separator via a circulation pipe. The liquid inlet of the triple-effect separator is connected via a separation pipeline. The circulation port of the triple-effect separator is connected to the liquid inlet of the triple-effect evaporator via a circulation pipeline. The liquid outlet of the triple-effect evaporator is connected to the liquid return port of the triple-effect separator via a circulation pipeline. The liquid outlets of the first-effect separator, second-effect separator, and triple-effect separator are each equipped with a liquid outlet pump, and the circulation ports are each equipped with a circulation pump. The outlet of the circulation pump of the first-effect separator is connected to the liquid inlet of the second first-effect evaporator via a spare circulation pipeline. The liquid outlet of the second first-effect evaporator is connected to the liquid return port of the first-effect separator via a spare circulation pipeline. The first and second first-effect evaporators are each equipped with a steam inlet.

[0013] Furthermore, control valves are installed at the inlet and outlet of the first and second effect evaporators, respectively.

[0014] Furthermore, the circulation ports and liquid outlets of the first-effect separator, second-effect separator, and third-effect separator are located at the bottom, while the liquid inlet is located at the top.

[0015] Furthermore, regulating valves are installed at the circulation port, liquid outlet, liquid inlet, and liquid return port of the first-effect separator, second-effect separator, and third-effect separator.

[0016] Furthermore, the liquid outlet and liquid inlet of the double-effect evaporator and the triple-effect evaporator are respectively equipped with regulating valves, and a steam inlet is provided at the top.

[0017] This utility model has the following advantages compared with the prior art:

[0018] 1. This utility model has great promotional value for the use of triple-effect evaporation system to treat high-hardness, high-COD wastewater, improves the continuity of the production system, and can reduce unplanned system shutdowns caused by tube blockage.

[0019] This invention completes the cleaning of the triple-effect evaporator tubes without stopping the machine. The cleaning method is simple and feasible, and can be easily used on a large scale for the evaporation and crystallization of ammonium sulfate, ammonium chloride, and magnesium sulfate. It has low operating costs and maintains the stable operation of the system.

[0020] Because the ammonium sulfate wastewater generated during the rare earth transformation process has high hardness, and the residual oxalate content is high after the addition of oxalic acid reagent in the pretreatment, the first-effect evaporator is prone to scaling after concentration in the triple-effect evaporator. When the scaling is severe and high-pressure cleaning of the scale is required, this utility model realizes high-pressure cleaning without stopping the production, which can maintain the continuity of production and improve the production capacity.

[0021] 2. The tube cleaning process of the single-effect evaporator does not require system shutdown, which increases production capacity and reduces energy waste caused by frequent start-ups and shutdowns.

[0022] The switching process is short, generally completed within one hour, and the tube cleaning process does not require system shutdown. Comparing the five months before and seven months after the implementation of this invention, before implementation, the equipment required high-pressure cleaning of the first-effect evaporator tubes due to scaling, resulting in a 10-day shutdown. After implementation, the equipment required high-pressure cleaning of the first-effect evaporator tubes due to scaling, resulting in a 3-day shutdown. Through data comparison, the cumulative downtime was reduced by 7 days, improving the continuity and stability of production.

[0023] 3. During the switching of the single-effect evaporator, frequent start-up and shutdown are not required, reducing energy waste.

[0024] Because the ammonium sulfate wastewater generated during the rare earth transformation process contains high levels of impurity ions such as calcium, magnesium, and silicon, it easily forms scale during the evaporation and concentration process due to its high concentration. This necessitates periodic cleaning and unclogging, reducing equipment operating rates and increasing various production costs. The frequent cleaning and unclogging, with each cleaning cycle lasting approximately 2-3 days, severely restricts production and impacts enterprise efficiency. Adding a new evaporation system involves a large initial investment and is not economically viable. By adding a single-effect evaporator prone to scaling, and enabling two sets of single-effect evaporators to be used interchangeably, the entire system can be kept running continuously, achieving continuous production, increasing capacity, and reducing energy waste caused by frequent start-ups and shutdowns. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structural principle of the triple-effect evaporation system in this utility model. Detailed Implementation

[0026] The following description fully illustrates specific embodiments of the present invention to enable those skilled in the art to practice and reproduce them.

[0027] like Figure 1 The diagram shown is a schematic diagram of the structure of the triple-effect evaporation system in this utility model.

[0028] The triple-effect evaporation system includes: a first-effect separator 1, a first-effect evaporator 2, a second-effect evaporator 3, a second-effect separator 4, a second-effect evaporator 5, a triple-effect separator 6, and a triple-effect evaporator 7.

[0029] The circulation port of the first-effect separator 1 is connected to the inlet of the first-effect evaporator 2 via a circulation pipe, and the outlet of the first-effect evaporator 2 is connected to the return port of the first-effect separator 1 via a circulation pipe. The outlet of the first-effect separator 1 is connected to the inlet of the second-effect separator 4 via a separation pipe, and the circulation port of the second-effect separator 4 is connected to the inlet of the second-effect evaporator 5 via a circulation pipe. The outlet of the second-effect evaporator 5 is connected to the return port of the second-effect separator 4 via a circulation pipe. The outlet of the second-effect separator 4 is connected to the inlet of the third-effect separator 6 via a separation pipe, and the circulation port of the third-effect separator 6 is connected to... The liquid inlet of the triple-effect evaporator 7 and the liquid outlet of the triple-effect evaporator 7 are connected to the liquid return port of the triple-effect separator 6 through a circulation pipeline; the liquid outlets of the first-effect separator 1, the second-effect separator 4, and the triple-effect separator 6 are respectively equipped with liquid outlet pumps 8, and the circulation ports are respectively equipped with circulation pumps 9; the outlet of the circulation pump 9 of the first-effect separator 1 is connected to the liquid inlet of the second first-effect evaporator 3 through a spare circulation pipeline, and the liquid outlet of the second first-effect evaporator 3 is connected to the liquid return port of the first-effect separator 1 through a spare circulation pipeline; the first first-effect evaporator 2 and the second first-effect evaporator 3 are respectively equipped with steam inlets, which are used to connect to steam pipelines.

[0030] The inlet and outlet of the first-effect evaporator 2 and the second-effect evaporator 3 are respectively equipped with control valves.

[0031] The circulation port and liquid outlet of the single-effect separator 1, the double-effect separator 4, and the triple-effect separator 6 are located at the bottom, and the liquid inlet is located at the top. The circulation port, liquid outlet, liquid inlet, and liquid return port of the single-effect separator 1, the double-effect separator 4, and the triple-effect separator 6 are each equipped with a regulating valve.

[0032] The liquid outlet and liquid inlet of the double-effect evaporator 5 and the triple-effect evaporator 7 are respectively equipped with regulating valves, and steam inlets are also provided.

[0033] The triple-effect evaporation system employs the following process:

[0034] Ammonium sulfate wastewater enters the first-effect separator 1 through the inlet. The first solid-liquid separation of the ammonium sulfate wastewater is carried out in the first-effect separator 1. The ammonium sulfate wastewater enters the first-effect evaporator 2 through the circulation port. The first-effect evaporator 2 heats and concentrates the ammonium sulfate wastewater with the help of steam. The concentrated ammonium sulfate wastewater returns to the first-effect separator 1 through the return port.

[0035] The ammonium sulfate wastewater separated in the first stage enters the second-effect separator 4 through the inlet. The second solid-liquid separation is carried out in the second-effect separator 4. The ammonium sulfate wastewater enters the second-effect evaporator 5 through the circulation port. The second-effect evaporator 5 uses steam to heat and concentrate the ammonium sulfate wastewater. The concentrated ammonium sulfate wastewater returns to the second-effect separator 4 through the return port.

[0036] The ammonium sulfate wastewater from the secondary separation enters through the inlet of the triple-effect separator 6, where a third solid-liquid separation is performed. The ammonium sulfate wastewater then enters the triple-effect evaporator 7 through the circulation port. The triple-effect evaporator 7 uses steam to heat and concentrate the ammonium sulfate wastewater. The concentrated ammonium sulfate wastewater then returns to the triple-effect separator 6 through the return port.

[0037] When it is necessary to remove scale buildup from the first-effect evaporator 2, close the control valves on the inlet and outlet sides of the first-effect evaporator 2, and open the control valves on the inlet and outlet sides of the second-effect evaporator 3. The heating and concentration process is then directed to the second-effect evaporator 3, and the first-effect evaporator 2 stops operating. The scale buildup area of ​​the first-effect evaporator 2 is then cleaned, allowing the first-effect separator 1 to complete the tube cleaning of the first-effect evaporator 2 without shutting down.

[0038] The second-effect evaporator 3 also requires cleaning to remove scale. This allows for switching between the first-effect evaporators 2 and 3 on the first-effect separator 1. The first-effect evaporators 2 and 3 are used in parallel online to address key scaling areas of the evaporation equipment, enabling uninterrupted operation during periodic maintenance and increasing production capacity.

[0039] Before the upgrade of the ammonium sulfate wastewater evaporator system, the average amount of ammonium sulfate wastewater treated was 1426 m³. 3 / d, after the renovation, from June to December, an average of 1553m³ of ammonium sulfate wastewater was treated. 3 / d. By switching to a single-effect evaporator, the number of operating days is effectively increased, and the daily wastewater treatment capacity is increased by approximately 130m³. 3 / d.

[0040] The terminology used in this invention is descriptive and exemplary, and not restrictive. Since this invention can be embodied in various forms without departing from the spirit or essence of the technical solution, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A triple-effect evaporation system, characterized in that, include: Single-effect separator, first-effect evaporator, second-effect evaporator, second-effect separator, second-effect evaporator, third-effect separator, third-effect evaporator; The circulation port of the first-effect separator is connected to the inlet of the first-effect evaporator via a circulation pipe, and the outlet of the first-effect evaporator is connected to the return port of the first-effect separator via a circulation pipe. The outlet of the first-effect separator is connected to the inlet of the second-effect separator via a separation pipe, and the circulation port of the second-effect separator is connected to the inlet of the second-effect evaporator via a circulation pipe. The outlet of the second-effect evaporator is connected to the return port of the second-effect separator via a circulation pipe. The outlet of the second-effect separator is connected to the inlet of the third-effect separator via a separation pipe, and the circulation port of the third-effect separator is connected to... The liquid inlet of the triple-effect evaporator is connected via a circulation pipeline, and the liquid outlet of the triple-effect evaporator is connected to the liquid return port of the triple-effect separator via the circulation pipeline. The liquid outlets of the first-effect separator, the second-effect separator, and the third-effect separator are each equipped with a liquid outlet pump, and the circulation ports are each equipped with a circulation pump. The outlet of the circulation pump of the first-effect separator is connected to the liquid inlet of the second-effect evaporator via a spare circulation pipeline, and the liquid outlet of the second-effect evaporator is connected to the liquid return port of the first-effect separator via a spare circulation pipeline. The first-effect evaporator and the second-effect evaporator are each equipped with a steam inlet.

2. The triple-effect evaporation system as described in claim 1, characterized in that, The inlet and outlet of the first-effect evaporator and the second-effect evaporator are each equipped with a control valve.

3. The triple-effect evaporation system as described in claim 1, characterized in that, The circulation ports and liquid outlets of the first-effect separator, second-effect separator, and third-effect separator are located at the bottom, while the liquid inlet is located at the top.

4. The triple-effect evaporation system as described in claim 1, characterized in that, The circulation port, liquid outlet, liquid inlet, and liquid return port of the single-effect separator, double-effect separator, and triple-effect separator are each equipped with a regulating valve.

5. The triple-effect evaporation system as described in claim 1, characterized in that, The liquid outlet and inlet of the double-effect evaporator and triple-effect evaporator are respectively equipped with regulating valves, and a steam inlet is provided at the top.

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