System for separating salt and extracting bromine from purified terephthalic acid membrane concentrated water

Abstract

The utility model belongs to the field of chemical raw material recovery, and discloses a system for separating salt and extracting bromine from purified terephthalic acid membrane concentrated water. The system comprises a thermal decomposition device, a nanofiltration device, a static mixer and a bromine extraction rectification device. The utility model solves the technical problems that the acid consumption is large before bromine is extracted from purified terephthalic acid wastewater, and poisoning is easily caused by leakage hidden danger in the transportation and storage process of liquid chlorine.

Description

Technical Field

[0001] The utility model belongs to the field of chemical raw material recovery, and more specifically, relates to a system for salt separation and bromine extraction from the membrane concentrated water of purified terephthalic acid. Background Art

[0002] Purified terephthalic acid is the binary carboxylic acid with the largest output, which is widely used in the production of polyester fiber, polyester, engineering polyester plastics, etc., and can also be used as the raw material of plasticizer and dye intermediate. At present, purified terephthalic acid is produced from p-xylene through catalytic oxidation. In this process, hydrobromic acid is used as the catalyst and sodium carbonate solution is used as the cleaning agent. Therefore, the purified terephthalic acid wastewater mainly contains carbonate, bicarbonate and bromide ions, and in addition, it also contains a small amount of chloride ions and sulfate ions. Among them, the added value of bromide ions is relatively high. If bromine can be extracted in the form of bromine, the wastewater treatment cost can be reduced and added value can be generated. As is well known, the bromine extraction process needs to be carried out under acidic conditions with pH < 5, otherwise the generated bromine will undergo disproportionation reaction to form sodium bromide and sodium hypobromite. However, the alkalinity of purified terephthalic acid wastewater is high, and a large amount of acid will be consumed during the acid adjustment process, which not only greatly increases the bromine extraction cost, but also generates a large amount of miscellaneous salts, resulting in new miscellaneous salt treatment costs. Therefore, how to reduce the acid consumption and extract bromine from purified terephthalic acid wastewater at low cost has become an urgent problem to be solved.

[0003] The currently mature bromine extraction process is to introduce chlorine gas into bromine-containing wastewater under acidic conditions, and then recover bromine through distillation. Patent application 202111247975.0 proposes to extract bromine by introducing chlorine gas into electronic waste. This electronic waste is different from purified terephthalic acid wastewater. It contains hydrogen chloride, hydrogen bromide, etc., and is acidic itself, so there is no problem of large acid consumption for acid adjustment. Patent application 202211026720.6 proposes to extract bromine from potassium mirabilite wastewater using sodium hypochlorite or sodium chlorate. However, it is found in actual operation that when using the above two oxidants, the extraction rate of bromine is low because it is difficult to ensure the ratio of the oxidant to the bromide ions to be oxidized, and the addition amount of the oxidant needs to be adjusted at any time according to the changes of water quality and water volume. When the oxidant is in excess, sodium hypochlorite and sodium chlorate will continue to oxidize the generated bromine to sodium hypobromite and sodium bromate, resulting in a sharp decrease in the bromine extraction rate. And after introducing sodium ions into potassium mirabilite wastewater, miscellaneous salts containing sodium salts and potassium salts will be generated, which are difficult to recover. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a system for salt separation and bromine extraction from the membrane concentrated water of purified terephthalic acid in view of the deficiencies of the prior art. The utility model solves the technical problem of large acid consumption before bromine extraction from purified terephthalic acid wastewater.

[0005] To achieve the above object, the present utility model provides a system for separating salts and extracting bromine from concentrated water of purified terephthalic acid film, and the system includes a heating and decomposition device, a nanofiltration device, a static mixer, a chlorine generation kettle, and a bromine extraction and rectification device;

[0006] The heating and decomposition device includes a concentrated water feed pump, a heating and decomposition kettle, a preheater, and a cooler;

[0007] The nanofiltration device includes a first-stage high-pressure feed pump, a first-stage nanofiltration membrane column, a second-stage high-pressure feed pump, and a second-stage nanofiltration membrane column;

[0008] The static mixer is provided with a water production inlet, a first hydrochloric acid feed inlet, and an acidified liquid outlet;

[0009] The middle part of the chlorine generation kettle is provided with a second hydrochloric acid feed inlet and a chlorine generation raw material feed inlet, the top is provided with a chlorine outlet, and the bottom is provided with a first sodium chloride aqueous solution outlet;

[0010] The bromine extraction and rectification device includes a bromine extraction and rectification tower, a first-stage condenser, a second-stage condenser, and a phase separation and reflux tank; the bromine extraction and rectification tower includes a tower body and a tower kettle connected up and down;

[0011] The concentrated water feed pump is sequentially connected to the cold source inlet and outlet of the first-stage condenser, the preheater, the heating and decomposition kettle, and the inlet of the cooler; the outlet of the cooler and the concentrated water outlet of the second-stage nanofiltration membrane column converge and are sequentially connected to the first-stage high-pressure feed pump, the inlet of the first-stage nanofiltration membrane column, the water production outlet of the first-stage nanofiltration membrane column, the second-stage high-pressure feed pump, the inlet of the second-stage nanofiltration membrane column, the water production outlet of the second-stage nanofiltration membrane column, and the water production inlet of the static mixer;

[0012] The acidified liquid outlet of the static mixer is connected to the acidified liquid feed inlet arranged in the upper middle part of the tower body; the chlorine outlet is connected to the chlorine feed inlet arranged in the lower middle part of the tower body; the gas-phase discharge outlet arranged at the top of the tower body is sequentially connected to the heat source inlet and outlet of the first-stage condenser, the heat source inlet and outlet of the second-stage condenser, and the inlet of the phase separation and reflux tank; the phase separation and reflux tank is provided with a heavy-phase outlet and a light-phase outlet, the heavy-phase outlet is connected to the bromine extraction pipeline, and the light-phase outlet is connected to the water-phase reflux inlet arranged at the top of the tower body.

[0013] Preferably, a stirrer is arranged in the heating and decomposition kettle.

[0014] Preferably, the concentrated water outlet of the first-stage nanofiltration membrane column is connected to a sodium carbonate recovery device.

[0015] Preferably, the bottom of the chlorine generation kettle is provided with a first sodium chloride aqueous solution outlet.

[0016] Preferably, a stirrer is arranged in the chlorine generation kettle.

[0017] Preferably, the system further includes a hydrochloric acid feed pump;

[0018] The outlet of the hydrochloric acid feed pump is divided into two paths, one path is connected to the first hydrochloric acid feed port, and the other path is connected to the second hydrochloric acid feed port.

[0019] Preferably, the system further includes a chlorine production raw material feed pump, and the chlorine production raw material feed pump is connected to the chlorine production raw material feed port.

[0020] Preferably, a second sodium chloride aqueous solution outlet is provided at the bottom of the bromine extraction rectification column kettle;

[0021] The bromine extraction rectification device further includes a kettle circulating discharge pump, a kettle reboiler, a sodium chloride aqueous solution discharge pipeline and a kettle cooler; a circulating material return port is further provided at the kettle of the bromine extraction rectification column;

[0022] The second sodium chloride aqueous solution outlet is connected to the inlet of the kettle circulating discharge pump;

[0023] The outlet of the kettle circulating discharge pump is divided into two paths, one path is sequentially connected to the kettle reboiler and the circulating material return port, and the other path is sequentially connected to the kettle cooler and the sodium chloride aqueous solution discharge pipeline.

[0024] Preferably, packing and / or trays are provided inside the bromine extraction rectification column.

[0025] Preferably, the number of theoretical plates of the bromine extraction rectification column is 5 - 30.

[0026] The beneficial effects of the technical solution of the present utility model are as follows:

[0027] The present utility model solves the technical problems of large acid consumption before bromine extraction from purified terephthalic acid wastewater and potential leakage hazards during the transportation and storage of liquid chlorine, which are prone to cause poisoning.

[0028] The present utility model utilizes the unstable property of sodium bicarbonate to decompose it into sodium carbonate at high temperature, which is convenient to separate it from monovalent ions such as chloride ions and bromide ions by nanofiltration, greatly reducing the alkalinity of the nanofiltration produced water for bromine extraction, and significantly reducing the acid consumption in the acid adjustment stage before bromine extraction.

[0029] The present utility model prepares chlorine by mixing sodium hypochlorite or sodium chlorate solution with hydrochloric acid, which can not only ensure a high extraction rate of bromine, but also avoid the occurrence of chlorine leakage and poisoning accidents that may occur during the transportation and storage of liquid chlorine, and is inherently safe.

[0030] Other features and advantages of the present utility model will be described in detail in the subsequent specific implementation part. Description of the Drawings

[0031] The above and other objects, features, and advantages of the present utility model will become more apparent by describing the exemplary embodiments of the present utility model in more detail with reference to the accompanying drawings. In the exemplary embodiments of the present utility model, the same reference numerals generally represent the same components.

[0032] Figure 1 The schematic diagram of a system for extracting bromine from concentrated water of purified terephthalic acid film provided in Embodiment 1 of the present utility model is shown.

[0033] The description of the reference numerals is as follows:

[0034] 11 - Concentrated water feed pump; 12 - Heating decomposition kettle; 13 - Preheater; 14 - Cooler; 15 - Concentrated water feed port; 16 - Pyrolysis concentrated water outlet; 17 - Purified terephthalic acid film concentrated water supply device;

[0035] 21 - First - stage high - pressure feed pump; 22 - First - stage nanofiltration membrane column; 23 - Inlet of the first - stage nanofiltration membrane column; 24 - Product water outlet of the first - stage nanofiltration membrane column; 25 - Concentrated water outlet of the first - stage nanofiltration membrane column; 26 - Sodium carbonate recovery device;

[0036] 31 - Second - stage high - pressure feed pump; 32 - Second - stage nanofiltration membrane column; 33 - Inlet of the second - stage nanofiltration membrane column; 34 - Product water outlet of the second - stage nanofiltration membrane column; 35 - Concentrated water outlet of the second - stage nanofiltration membrane column;

[0037] 41 - Static mixer; 42 - Product water inlet; 43 - First hydrochloric acid feed port; 44 - Acidified liquid outlet;

[0038] 51 - Hydrochloric acid feed pump; 52 - Feed pump for raw materials for chlorine production; 53 - Chlorine generation kettle; 54 - Second hydrochloric acid feed port; 55 - Feed port for raw materials for chlorine production; 56 - First sodium chloride aqueous solution outlet; 57 - Chlorine outlet; 58 - Hydrochloric acid supply device; 59 - Raw material supply device for chlorine production;

[0039] 61 - Tower kettle, 62 - Tower body, 63 - Tower kettle circulating discharge pump; 64 - Tower kettle reboiler; 65 - Tower kettle cooler; 66 - First - stage condenser; 67 - Second - stage condenser; 68 - Phase - separation reflux tank; 69 - Chlorine feed port; 610 - Acidified liquid feed port; 611 - Gas - phase discharge port; 612 - Aqueous - phase reflux port; 613 - Second sodium chloride aqueous solution outlet; 614 - Heavy - phase outlet; 615 - Light - phase outlet; 616 - Bromine. Detailed implementation manners

[0040] The preferred embodiments of the present utility model will be described in more detail below. Although the preferred embodiments of the present utility model are described below, it should be understood that the present utility model can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present utility model more thorough and complete, and to fully convey the scope of the present utility model to those skilled in the art.

[0041] The present utility model provides a system for separating and extracting bromine from concentrated water of purified terephthalic acid film, the system comprising a heating and decomposition device, a nanofiltration device, a static mixer, a chlorine gas generation kettle and a bromine extraction rectification device;

[0042] The heating and decomposition device comprises a concentrated water feed pump, a heating and decomposition kettle, a preheater and a cooler;

[0043] The nanofiltration device comprises a first-stage high-pressure feed pump, a first-stage nanofiltration membrane column, a second-stage high-pressure feed pump and a second-stage nanofiltration membrane column;

[0044] The static mixer is provided with a water production inlet, a first hydrochloric acid feed inlet and an acidified liquid outlet;

[0045] The middle part of the chlorine gas generation kettle is provided with a second hydrochloric acid feed inlet and a chlorine gas production raw material feed inlet, the top is provided with a chlorine gas outlet, and the bottom is provided with a first sodium chloride aqueous solution outlet;

[0046] The bromine extraction rectification device comprises a bromine extraction rectification tower, a first-stage condenser, a second-stage condenser and a phase separation reflux tank; the bromine extraction rectification tower comprises a tower body and a tower kettle which are connected up and down;

[0047] The concentrated water feed pump is sequentially connected to the cold source inlet and outlet of the first-stage condenser, the preheater, the heating and decomposition kettle and the inlet of the cooler; the outlet of the cooler and the concentrated water outlet of the second-stage nanofiltration membrane column converge and are sequentially connected to the first-stage high-pressure feed pump, the inlet of the first-stage nanofiltration membrane column, the water production outlet of the first-stage nanofiltration membrane column, the second-stage high-pressure feed pump, the inlet of the second-stage nanofiltration membrane column, the water production outlet of the second-stage nanofiltration membrane column and the water production inlet of the static mixer;

[0048] The acidified liquid outlet of the static mixer is connected to the acidified liquid feed inlet arranged in the upper middle part of the tower body; the chlorine gas outlet is connected to the chlorine gas feed inlet arranged in the lower middle part of the tower body; the gas-phase discharge outlet arranged at the top of the tower body is sequentially connected to the heat source inlet and outlet of the first-stage condenser, the heat source inlet and outlet of the second-stage condenser and the inlet of the phase separation reflux tank; the phase separation reflux tank is provided with a heavy phase outlet and a light phase outlet, the heavy phase outlet is connected to the bromine extraction pipeline, and the light phase outlet is connected to the water phase reflux inlet arranged at the top of the tower body.

[0049] In one example, a stirrer is arranged in the heating and decomposition kettle.

[0050] In one example, the concentrated water outlet of the primary nanofiltration membrane column is connected to the sodium carbonate recovery device.

[0051] In one example, a first sodium chloride aqueous solution outlet is provided at the bottom of the chlorine generation kettle.

[0052] In one example, a stirrer is provided inside the chlorine generation kettle.

[0053] In one example, the system further includes a hydrochloric acid feed pump;

[0054] The outlet of the hydrochloric acid feed pump is divided into two paths, one path is connected to the first hydrochloric acid feed port, and the other path is connected to the second hydrochloric acid feed port.

[0055] In one example, the system further includes a chlorine raw material feed pump, and the chlorine raw material feed pump is connected to the chlorine raw material feed port.

[0056] In one example, a second sodium chloride aqueous solution outlet is provided at the bottom of the bromine extraction distillation column kettle;

[0057] The bromine extraction distillation device further includes a kettle circulating discharge pump, a kettle reboiler, a sodium chloride aqueous solution discharge pipeline, and a kettle cooler; a circulating material return port is further provided at the kettle of the bromine extraction distillation column;

[0058] The second sodium chloride aqueous solution outlet is connected to the inlet of the kettle circulating discharge pump;

[0059] The outlet of the kettle circulating discharge pump is divided into two paths, one path is sequentially connected to the kettle reboiler and the circulating material return port, and the other path is sequentially connected to the kettle cooler and the sodium chloride aqueous solution discharge pipeline.

[0060] In one example, packing and / or trays are provided inside the bromine extraction distillation column.

[0061] In one example, the number of theoretical plates of the bromine extraction distillation column is 5 - 30.

[0062] In the present utility model, the hydrochloric acid supply device is connected to the inlet of the hydrochloric acid feed pump, and the chlorine raw material supply device is connected to the inlet of the chlorine raw material feed pump.

[0063] In the present utility model, the internal parts and pipelines related to the shells of the static mixer, the chlorine generation kettle, and the bromine extraction distillation column are all made of anti-corrosion materials, such as PTFE, PVDF, ceramics, enamel, glass, etc.

[0064] The present utility model further provides a method for salt separation and bromine extraction from the concentrated water of purified terephthalic acid film. The method uses the above system and includes the following steps:

[0065] S1: Thermal decomposition

[0066] The purified terephthalic acid film concentrated water is preheated and then sent to the heating decomposition kettle; in the heating decomposition kettle, the bicarbonate radicals in the purified terephthalic acid film concentrated water decompose and transform into carbonate radicals to obtain pyrolysis concentrated water;

[0067] S2: Nanofiltration for salt separation

[0068] After cooling down the pyrolysis concentrated water, it is sent to the nanofiltration device together with the divalent ion concentrated water from the secondary nanofiltration membrane column for two-stage nanofiltration treatment. The divalent ions are retained. The primary concentrated water is obtained at the concentrated water outlet of the primary nanofiltration membrane column, and the primary product water is obtained at the product water outlet of the primary nanofiltration membrane column. The primary product water is sent to the inlet of the secondary nanofiltration membrane column. The divalent ion concentrated water is obtained at the concentrated water outlet of the secondary nanofiltration membrane column, and the monovalent ion product water is obtained at the product water outlet of the secondary nanofiltration membrane column;

[0069] S3: Bromine extraction

[0070] The monovalent ion product water and hydrochloric acid are sent into the static mixer for mixing to obtain an acidified solution; the acidified solution is sent into the bromine extraction distillation column from the upper middle part of the column body, and chlorine gas is sent into the bromine extraction distillation column from the lower middle part of the column body to obtain a top distillate. After condensation and phase separation, a heavy phase material and a light phase material are obtained. The heavy phase material is discharged from the system through a bromine extraction pipeline to recover bromine, and the light phase material is refluxed to the top of the bromine extraction distillation column.

[0071] In one example, in step S1:

[0072] The purified terephthalic acid film concentrated water is obtained by subjecting purified terephthalic acid wastewater to pretreatment and membrane separation treatment; the pretreatment is at least one of resin adsorption, electrochemistry, biochemical treatment, and extraction; the membrane separation treatment is at least one of ultrafiltration, nanofiltration, and reverse osmosis;

[0073] The temperature of the preheated purified terephthalic acid film concentrated water is 95 - 100 °C;

[0074] The residence time of the purified terephthalic acid film concentrated water in the heating decomposition kettle is 1 - 120 min, preferably 10 - 100 min.

[0075] In one example, in step S2:

[0076] The temperature of the pyrolysis concentrated water after cooling down is < 40 °C;

[0077] The water production rate of the monovalent ion product water is 30 - 70%;

[0078] The method further includes discharging the primary concentrated water from the system to recover sodium carbonate.

[0079] In the present utility model, the two-stage nanofiltration treatment intercepts divalent ions (carbonate, sulfate) in the pyrolysis concentrated water, thereby obtaining produced water containing monovalent ions (chloride ion, bromide ion) and the divalent ion concentrated water.

[0080] In one example, in step S3:

[0081] The pH of the acidifying solution is < 5; in the preparation of the acidifying solution: the mass of hydrochloric acid used per liter of the produced water containing monovalent ions is 8 - 12 g, and the mass fraction of hydrochloric acid is 30 - 35%;

[0082] The operating pressure of the bromine extraction rectification column is 0.1013 - 0.2 MPa;

[0083] The preparation method of the chlorine gas includes sending hydrochloric acid and the raw material for preparing chlorine gas to a chlorine gas generation kettle for reaction, obtaining an aqueous sodium chloride solution at the bottom of the chlorine gas generation kettle, and obtaining the chlorine gas at the top of the chlorine gas generation kettle; the raw material for preparing chlorine gas is an aqueous sodium hypochlorite solution and / or an aqueous sodium chlorate solution;

[0084] The bromine extraction rectification column also obtains an aqueous sodium chloride solution at the bottom of the column. The method further includes dividing the aqueous sodium chloride solution at the bottom of the column into two parts after passing it through a bottom circulation discharge pump, returning one part to the bromine extraction rectification column through a bottom reboiler, and discharging the other part out of the system through a pipeline for discharging the aqueous sodium chloride solution after cooling.

[0085] In one example, when the raw material for preparing chlorine gas is only an aqueous sodium hypochlorite solution, the feeding molar ratio of hydrochloric acid to sodium hypochlorite in the chlorine gas generation kettle is (1.5 - 2.5):1.

[0086] In one example, when the raw material for preparing chlorine gas is only an aqueous sodium chlorate solution, the feeding molar ratio of hydrochloric acid to sodium chlorate in the chlorine gas generation kettle is (5.5 - 6.5):1.

[0087] The following examples and comparative examples use purified terephthalic acid wastewater generated by a purified terephthalic acid production device of an enterprise in Zhejiang. After pretreatment and reverse osmosis membrane concentration, the purified terephthalic acid membrane concentrated water is obtained. The ion detection in the membrane concentrated water is carried out by titration method and ion chromatography method. The bromine purity detection is carried out according to the standard QB / T 2021 - 2022.

[0088] The composition of the purified terephthalic acid membrane concentrated water before being treated by the systems and methods of the examples and comparative examples is shown in Table 1.

[0089] Table 1

[0090]

[0091] Example 1

[0092] This embodiment provides a system for separating salts and extracting bromine from the concentrated water of purified terephthalic acid film, as Figure 1 shown. The system includes a heating and decomposition device, a nanofiltration device, a static mixer, a chlorine generation kettle, and a bromine extraction and rectification device;

[0093] The heating and decomposition device includes a concentrated water feed pump 11, a heating and decomposition kettle 12, a preheater 13, and a cooler 14; a stirrer is arranged in the heating and decomposition kettle;

[0094] The nanofiltration device includes a first-stage high-pressure feed pump 21, a first-stage nanofiltration membrane column 22, a second-stage high-pressure feed pump 31, and a second-stage nanofiltration membrane column 32; both the first-stage nanofiltration membrane column 22 and the second-stage nanofiltration membrane column 32 adopt a stacked-tube nanofiltration membrane (DT type);

[0095] The static mixer 41 is provided with a water production inlet 42, a first hydrochloric acid feed inlet 43, and an acidified liquid outlet 44;

[0096] The middle of the chlorine generation kettle 53 is provided with a second hydrochloric acid feed inlet 54 and a chlorine generation raw material feed inlet 55, the top is provided with a chlorine outlet 57, and the bottom is provided with a first sodium chloride aqueous solution outlet 56; a stirrer is arranged in the chlorine generation kettle 55;

[0097] The bromine extraction and rectification device includes a bromine extraction and rectification tower, a first-stage condenser 66, a second-stage condenser 67, a phase separation reflux tank 68, a tower kettle circulating discharge pump 63, a tower kettle reboiler 64, a sodium chloride aqueous solution discharge pipeline, and a tower kettle cooler 65; the bromine extraction and rectification tower includes a tower body 62 (with a diameter of 50 mm and a height of 2 m, filled with glass spring packing with a diameter of 4 mm) and a tower kettle 61 (with a volume of 5 L) connected up and down;

[0098] The concentrated water feed pump 11 is sequentially connected to the cold source inlet and outlet of the first-stage condenser 66, the preheater 13, the heating and decomposition kettle 12, and the inlet of the cooler 14; the outlet of the cooler 14 and the concentrated water outlet 35 of the second-stage nanofiltration membrane column are combined and sequentially connected to the first-stage high-pressure feed pump 21, the inlet 23 of the first-stage nanofiltration membrane column, the water production outlet 24 of the first-stage nanofiltration membrane column, the second-stage high-pressure feed pump 31, the inlet 33 of the second-stage nanofiltration membrane column, the water production outlet 34 of the second-stage nanofiltration membrane column, and the water production inlet 42 of the static mixer; the concentrated water outlet 25 of the first-stage nanofiltration membrane column is connected to the sodium carbonate recovery device 26.

[0099] The acidified liquid outlet 44 of the static mixer is connected to the acidified liquid inlet 610 provided in the upper middle part of the tower body (the height of the acidified liquid inlet from the tower kettle is 1.8 m); the chlorine gas outlet 27 of the chlorine gas generation kettle is connected to the chlorine gas inlet 69 provided in the lower middle part of the tower body (the height of the chlorine gas inlet from the tower kettle is 0.2 m); the gas-phase discharge port 611 provided at the top of the tower body is sequentially connected to the heat source inlet and outlet of the first-stage condenser 66, the heat source inlet and outlet of the second-stage condenser 67, and the inlet of the phase separation reflux tank 68; the phase separation reflux tank 68 is provided with a heavy-phase outlet 614 and a light-phase outlet 615, the heavy-phase outlet 614 is connected to the bromine extraction pipeline, and the light-phase outlet 615 is connected to the aqueous-phase reflux port 612 provided at the top of the tower body.

[0100] A second sodium chloride aqueous solution outlet 613 is provided at the bottom of the tower kettle of the bromine extraction rectification tower; a circulating material return port is further provided in the tower kettle of the bromine extraction rectification tower; the second sodium chloride aqueous solution outlet 613 is connected to the inlet of the tower kettle circulating discharge pump 63; the outlet of the tower kettle circulating discharge pump 63 is divided into two paths, one path is sequentially connected to the tower kettle reboiler 64 and the circulating material return port, and the other path is sequentially connected to the tower kettle cooler 65 and the sodium chloride aqueous solution discharge pipeline;

[0101] The system further includes a hydrochloric acid feed pump 51 and a chlorine gas production raw material feed pump 52; the outlet of the hydrochloric acid feed pump 51 is divided into two paths, one path is connected to the first hydrochloric acid inlet 43, and the other path is connected to the second hydrochloric acid inlet 54; the chlorine gas production raw material feed pump 52 is connected to the chlorine gas production raw material inlet 55.

[0102] The internal parts and pipelines related to the shell of the static mixer 41, the chlorine gas generation kettle 53, and the bromine extraction rectification tower are all made of glass.

[0103] This embodiment further provides a method for separating salts and extracting bromine from the concentrated water of purified terephthalic acid film. The method uses the above system and includes the following steps:

[0104] S1: Heating decomposition

[0105] Start the stirrer in the heating decomposition kettle 12, continuously feed the purified terephthalic acid film concentrated water preheated to 100 °C at a residence time of 20 min, the feed flow rate is 2 L / h, keep the liquid level constant, the bicarbonate in the purified terephthalic acid film concentrated water decomposes and converts into carbonate, and then continuously extract the pyrolyzed concentrated water after decomposition according to the feed flow rate. The CO3 in the pyrolyzed concentrated water is 2- 51510 mg / L, and the HCO3 is - 1130 mg / L.

[0106] S2: Nanofiltration salt separation

[0107] Cool the pyrolysis concentrated water to a temperature below 40°C and send it together with the divalent ion concentrated water from the secondary nanofiltration membrane column 32 to the nanofiltration device for two-stage nanofiltration treatment. The divalent ions are retained. The primary concentrated water is obtained at the concentrated water outlet 25 of the primary nanofiltration membrane column, and the primary product water is obtained at the product water outlet 24 of the primary nanofiltration membrane column. Send the primary product water to the inlet 33 of the secondary nanofiltration membrane column. The divalent ion concentrated water is obtained at the concentrated water outlet 35 of the secondary nanofiltration membrane column, and the monovalent ion product water is obtained at the product water outlet 34 of the secondary nanofiltration membrane column;

[0108] The water production rate of the primary product water of the primary nanofiltration membrane column is 70%, the water production rate of the monovalent ion product water of the secondary nanofiltration membrane column is 75%, and the total water production rate is 52.5%.

[0109] The compositions of the primary concentrated water and the monovalent ion product water are shown in Table 2.

[0110] Table 2

[0111]

[0112] S3: Bromine extraction

[0113] Continuously feed the monovalent ion product water and the hydrochloric acid aqueous solution into the static mixer 41 according to "1 L of the monovalent ion product water, the mass of the hydrochloric acid aqueous solution is 10.6 g, and the mass fraction of hydrochloric acid is 32%" to obtain an acidified solution (pH = 3);

[0114] Continuously feed hydrochloric acid (mass fraction 32%) and sodium hypochlorite aqueous solution (available chlorine 9%) into the chlorine generation kettle 53 according to a molar ratio of 2:1 for reaction. The temperature of the chlorine generation kettle 53 is 45°C. An aqueous sodium chloride solution (discharged from the system through the first aqueous sodium chloride solution outlet 56) is obtained at the bottom of the chlorine generation kettle 53, and chlorine gas is obtained at the top of the chlorine generation kettle 53;

[0115] Continuously feed the acidified solution into the bromine extraction rectification column from the upper middle part of the column body 62 at a rate of 1 L / h, and feed chlorine gas into the bromine extraction rectification column from the lower middle part of the column body 62 at a chlorine ratio of 105% to obtain the top distillate. After condensation and phase separation, a heavy-phase material and a light-phase material are obtained. The heavy-phase material (bromine content 96.5%, bromine extraction rate 95.5%) is discharged from the system through the bromine extraction pipeline to recover bromine 616, and the light-phase material is refluxed to the top of the bromine extraction rectification column;

[0116] An aqueous sodium chloride solution at the bottom of the column is also obtained at the bottom 61 of the bromine extraction rectification column. After passing the aqueous sodium chloride solution at the bottom of the column through the bottom circulation discharge pump 63, it is divided into two parts. One part is refluxed to the bromine extraction rectification column through the bottom reboiler 64, and the other part is discharged from the system through the aqueous sodium chloride solution discharge pipeline after cooling.

[0117] Example 2

[0118] This example provides a method for extracting bromine from concentrated water of purified terephthalic acid film by salt separation. The difference between this example and Example 1 is only that:

[0119] In the preparation of the chlorine gas, hydrochloric acid (with a mass fraction of 32%) and sodium chlorate aqueous solution are continuously fed into the chlorine gas generation kettle 53 in a molar ratio of 6:1 for reaction. The temperature of the chlorine gas generation kettle 53 is 45°C. An aqueous sodium chloride solution is obtained at the bottom of the chlorine gas generation kettle 53, and chlorine gas is obtained at the top of the chlorine gas generation kettle 53;

[0120] The bromine content obtained is 96.8%, and the bromine extraction rate is 95.7%.

[0121] Comparative Example 1

[0122] This comparative example provides a method for extracting bromine from concentrated water of purified terephthalic acid film by salt separation. The difference between this comparative example and Example 1 is only that:

[0123] 1. In this comparative example, the heating decomposition in step S1 is not carried out, and the concentrated water of purified terephthalic acid film is directly sent to the nanofiltration device together with the divalent ion concentrated water from the secondary nanofiltration membrane column for two-stage nanofiltration treatment.

[0124] The water production rate of the first-stage water production of the first-stage nanofiltration membrane column is 70%, the water production rate of the monovalent ion water production of the second-stage nanofiltration membrane column is 75%, and the total water production rate is 52.5%.

[0125] The compositions of the first-stage concentrated water and the monovalent ion water production in this comparative example are shown in Table 3.

[0126] Table 3

[0127]

[0128] 2. In step S3, the monovalent ion water production and the hydrochloric acid aqueous solution are continuously fed into the static mixer according to "1 L of the monovalent ion water production, the mass of the hydrochloric acid aqueous solution is 147.6 g, and the mass fraction of hydrochloric acid therein is 32%" to obtain an acidified solution (pH = 3);

[0129] The bromine content obtained in this comparative example is 96.2%, and the bromine extraction rate is 95.3%.

[0130] This comparative example does not carry out the heating decomposition in step S1 of Example 1, resulting in a large amount of bicarbonate entering the bromine extraction step. Therefore, the consumption of hydrochloric acid in the acidification stage of the monovalent ion water production is 14 times that of Example 1.

[0131] The embodiments of the present utility model have been described above. The above description is exemplary and not exhaustive, and is also not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A system for extracting bromine from concentrated water of purified terephthalic acid film by desalting, characterized in that, The system includes a thermal decomposition device, a nanofiltration device, a static mixer, a chlorine generation kettle, and a bromine extraction rectification device; The thermal decomposition device includes a concentrated water feed pump, a thermal decomposition kettle, a preheater, and a cooler; The nanofiltration device includes a first-stage high-pressure feed pump, a first-stage nanofiltration membrane column, a second-stage high-pressure feed pump, and a second-stage nanofiltration membrane column; The static mixer is provided with a product water inlet, a first hydrochloric acid feed inlet, and an acidified liquid outlet; In the middle of the chlorine generation kettle, there are a second hydrochloric acid feed inlet and a chlorine production raw material feed inlet. At the top, there is a chlorine outlet, and at the bottom, there is a first sodium chloride aqueous solution outlet; The bromine extraction rectification device includes a bromine extraction rectification tower, a first-stage condenser, a second-stage condenser, and a phase separation reflux tank; the bromine extraction rectification tower includes a tower body and a tower kettle connected up and down; The concentrated water feed pump is sequentially connected to the cold source inlet and outlet of the first-stage condenser, the preheater, the thermal decomposition kettle, and the inlet of the cooler; the outlet of the cooler and the concentrated water outlet of the second-stage nanofiltration membrane column converge and are sequentially connected to the first-stage high-pressure feed pump, the inlet of the first-stage nanofiltration membrane column, the product water outlet of the first-stage nanofiltration membrane column, the second-stage high-pressure feed pump, the inlet of the second-stage nanofiltration membrane column, the product water outlet of the second-stage nanofiltration membrane column, and the product water inlet of the static mixer; The acidified liquid outlet of the static mixer is connected to the acidified liquid feed inlet arranged in the upper middle part of the tower body; the chlorine outlet is connected to the chlorine feed inlet arranged in the lower middle part of the tower body; the gas-phase discharge outlet arranged at the top of the tower body is sequentially connected to the heat source inlet and outlet of the first-stage condenser, the heat source inlet and outlet of the second-stage condenser, and the inlet of the phase separation reflux tank; the phase separation reflux tank is provided with a heavy-phase outlet and a light-phase outlet. The heavy-phase outlet is connected to the bromine extraction pipeline, and the light-phase outlet is connected to the water-phase reflux inlet arranged at the top of the tower body.

2. The system for separating salts and extracting bromine from the concentrated water of purified terephthalic acid film according to claim 1, characterized in that, A stirrer is arranged in the thermal decomposition kettle.

3. The system for separating salts and extracting bromine from concentrated water of purified terephthalic acid film according to claim 1, wherein, The concentrated water outlet of the first-stage nanofiltration membrane column is connected to a sodium carbonate recovery device.

4. The system for extracting bromine from concentrated water and separating salts of purified terephthalic acid film according to claim 1, wherein At the bottom of the chlorine generation kettle, there is a first sodium chloride aqueous solution outlet.

5. The system for separating salts and extracting bromine from concentrated water of purified terephthalic acid film according to claim 1, wherein A stirrer is arranged in the chlorine generation kettle.

6. The system for separating salts and extracting bromine from concentrated water of purified terephthalic acid film according to claim 1, wherein, The system further includes a hydrochloric acid feed pump; The outlet of the hydrochloric acid feed pump is divided into two paths. One path is connected to the first hydrochloric acid feed inlet, and the other path is connected to the second hydrochloric acid feed inlet.

7. The system for separating bromine from concentrated water of purified terephthalic acid film according to claim 1, characterized in that, The system further includes a chlorine production raw material feed pump, and the chlorine production raw material feed pump is connected to the chlorine production raw material feed inlet.

8. The system for salt separation and bromine extraction from purified terephthalic acid membrane concentrated water according to claim 1, wherein At the bottom of the tower kettle of the bromine extraction rectification tower, there is a second sodium chloride aqueous solution outlet; The bromine extraction rectification device further includes a tower kettle circulating discharge pump, a tower kettle reboiler, a sodium chloride aqueous solution discharge pipeline, and a tower kettle cooler; the tower kettle of the bromine extraction rectification tower is further provided with a circulating material return port; The second sodium chloride aqueous solution outlet is connected to the inlet of the tower kettle circulating discharge pump; The outlet of the tower kettle circulating discharge pump is divided into two paths. One path is sequentially connected to the tower kettle reboiler and the circulating material return port, and the other path is sequentially connected to the tower kettle cooler and the sodium chloride aqueous solution discharge pipeline.

9. The system for separating salts and extracting bromine from concentrated water of purified terephthalic acid film according to claim 1, characterized in that, Packings and / or trays are arranged in the bromine extraction rectification tower.

10. The system for separating salts and extracting bromine from concentrated water of purified terephthalic acid film according to claim 9, characterized in that, The number of theoretical plates of the bromine extraction rectification tower is 5 - 30.

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