A hot-pressing cycle ammonium removal system and method for potassium chloride brine

Abstract

The application provides a hot pressure cycle ammonium removal system and method for potassium chloride brine, aiming at solving the technical problems of strong corrosive by-products, high energy consumption or secondary pollution in the existing potassium chloride brine ammonium removal technology. The hot pressure cycle ammonium removal method comprises the following steps: S10, hot pressure ion activation, through a high-temperature and high-pressure environment, ammonium ions in the brine are converted into free ammonia; S20, flash stripping ammonium removal, through pressure reduction, the free ammonia is gasified, and the gasified ammonia is absorbed by low-temperature condensate water; S30, zeolite ion capture, the brine after step S20 is reacted with zeolite, and residual ammonia ions in the brine are captured through ion exchange. The hot pressure cycle ammonium removal method has the advantages of three-stage coupling of 'hot pressure activation-flash stripping-zeolite capture', completely avoiding the risk of NCl3, and realizing resource recycling of by-product by-product ammonia water and NH4Cl.

Description

Technical Field

[0001] This invention relates to the field of potassium chloride brine deammonium removal technology, and more specifically to a hot-pressing cyclic deammonium removal method for potassium chloride brine. Background Technology

[0002] In the chlor-alkali and potash industries, the raw material, potassium chloride brine, often contains ammonium ions (NH4⁺, 20-50 mg / L). These ions react with chlorine gas in the electrolytic cell to generate nitrogen trichloride (NCl3), a highly explosive substance. A concentration ≥5% poses an explosion risk, seriously threatening safe production. Existing ammonium removal technologies have significant drawbacks:

[0003] The direct chlorination process relies on the introduction of chlorine gas to oxidize and remove ammonium, producing highly corrosive HCl and SO4²⁻ impurities (from the reducing agent Na2S2O3), which exacerbates equipment wear and affects electrolysis efficiency.

[0004] Although the vacuum desorption method avoids the addition of chemicals, it has a low deammoniation rate (≤80%) and high energy consumption (1.2t of steam per ton of brine).

[0005] The oxidation-stripping method requires sodium hypochlorite pretreatment, and residual chloramines may generate organic halides, causing secondary pollution. Summary of the Invention

[0006] To address the technical problems of existing potassium chloride brine deammonium removal technologies, such as highly corrosive byproducts, high energy consumption, or secondary pollution, this invention provides a hot-pressing cyclic deammonium removal method for potassium chloride brine. This method features a three-stage coupling process of "hot-pressing activation - flash steam stripping - zeolite capture," which completely avoids the risk of NCl3 and enables resource recycling of byproducts such as ammonia and NH4Cl.

[0007] The technical solution of this invention is:

[0008] A hot-pressure circulating deammoniation method for potassium chloride brine includes the following steps:

[0009] S10, thermal pressure ion activation, through a high temperature and high pressure environment, promotes the conversion of ammonium ions in the brine into free ammonia;

[0010] S20, flash vaporization removes ammonium by depressurizing free ammonia and absorbing the vaporized ammonia with low-temperature condensate;

[0011] S30, zeolite ion capture, involves reacting the brine from step S20 with zeolite to capture residual ammonia ions in the brine through ion exchange.

[0012] Optionally, step S10, hot-pressing ion activation, specifically includes:

[0013] S11. Preheat the brine to 85-90℃;

[0014] S12, pressurized circulating reaction, steam at a pressure of 0.3-0.5 MPa is introduced into the container containing the brine;

[0015] S13. Continue stirring.

[0016] Optionally, in step S11, the brine is preheated using a plate heat exchanger;

[0017] In step S12, the preheated brine is introduced into the pressurized reactor, and then steam is introduced into the pressurized reactor.

[0018] In step S13, the brine is continuously stirred in the pressurized reactor for at least 20 minutes.

[0019] Optionally, step S20, flash vapor stripping of ammonium, specifically includes:

[0020] S21. Flash evaporation and pressure reduction: The activated brine is introduced into the flash evaporator and instantly depressurized to -0.09MPa upon entering the flash evaporator, thereby generating ammonia vapor bubbles in the flash evaporator.

[0021] S22, cyclone stripping: brine spirals down in the flash tower and comes into contact with low-temperature condensate at 5-10℃.

[0022] Optionally, step S30, zeolite ion capture, specifically includes:

[0023] S31. Zeolite treatment: Modified clinoptilolite is used, and the modified clinoptilolite is preloaded with potassium ions.

[0024] S32, Ion exchange reaction, captures residual ammonia ions in brine through ion exchange.

[0025] Optionally, step S30, zeolite ion capture, further includes:

[0026] S33. Regeneration and recycling: After the modified clinoptilolite is saturated, it is washed with a 10% potassium chloride solution to obtain an ammonium chloride solution. The ammonium chloride solution is concentrated and recycled.

[0027] A hot-pressurized circulating deammonium removal system for potassium chloride brine includes the following components connected in series:

[0028] Plate heat exchangers are used for heating brine.

[0029] A pressurized reactor is used to pressurize heated brine, and a stirrer is installed inside the pressurized reactor.

[0030] Flash distillation towers are used to separate free ammonia from brine.

[0031] Zeolite reactors are used to exchange and capture residual ammonia ions in brine.

[0032] Optionally, the flash tower includes:

[0033] The tank has a feed inlet tangentially located in the middle of its wall, a discharge outlet at the bottom, and a gas outlet at the top.

[0034] A sprayer is located at the center of the top of the tank and sprays condensate downwards.

[0035] A spiral guide plate is disposed on the inner wall of the tank and located below the feed inlet;

[0036] An annular liquid collection tank is located in the middle of the tank body and below the sprayer.

[0037] Optionally, an annular umbrella cover is provided above the spiral guide plate, and the edge of the annular liquid collection tank is located below the edge of the umbrella cover.

[0038] Optionally, a pressure reducing valve is provided on the feed inlet of the tank;

[0039] The upper surface of the spiral guide plate has a concave structure.

[0040] Compared with the prior art, the beneficial effects of the present invention are:

[0041] It has the advantages of completely avoiding the risk of NCl3 through a three-stage coupling of "hot pressing activation - flash steam stripping - zeolite capture", and the by-products ammonia water and NH4Cl can achieve resource recycling. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the process steps of the present invention;

[0044] Figure 2 A schematic diagram of a hot-pressure circulating deammoniation system for potassium chloride brine.

[0045] Figure 3 This is a schematic diagram of the structure of a flash evaporator. Detailed Implementation

[0046] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0047] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0048] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0049] Example 1:

[0050] See Figure 1 This embodiment discloses a hot-pressing cyclic deammoniation method for potassium chloride brine, comprising the following steps:

[0051] S10, thermal pressure ion activation, through a high temperature and high pressure environment, promotes the conversion of ammonium ions in the brine into free ammonia.

[0052] S20 flash steam deammoniation involves reducing pressure to vaporize free ammonia, and then absorbing the vaporized ammonia with low-temperature condensate to achieve deep deammoniation of brine.

[0053] S30, zeolite ion capture, involves reacting the brine from step S20 with zeolite to capture residual ammonia ions in the brine through ion exchange.

[0054] In this embodiment, the dissolution equilibrium of ammonium ions (NH4⁺) is changed by temperature-pressure synergistic regulation, and the directional removal and resource recovery of ammonium are achieved by combining ion replacement reaction.

[0055] By employing a three-stage coupling process of "hot pressing activation - flash steam stripping - zeolite capture", the risk of NCl3 is completely avoided, and the byproducts ammonia water and NH4Cl can achieve resource recycling.

[0056] Specifically, step S10, hot-pressing ion activation, includes:

[0057] S11. The brine is preheated to 85-90℃ through plate heat exchanger 10. Under the high temperature of 85-90℃, the equilibrium constant increases (about 100 times higher than at 25℃), which causes the ammonium ions (NH4⁺) to dissociate and generate ammonia and hydrogen ions, thus promoting the generation of ammonia.

[0058] S12. Pressurized cyclic reaction: Steam at a pressure of 0.3-0.5 MPa is introduced into the container containing the brine, and the ambient temperature is maintained at 85-90℃. By pressurizing, the supersaturation of ammonia in the brine is increased, forcing the reaction to shift to the right (i.e., forcing ammonium ions to dissociate into ammonia and hydrogen ions).

[0059] S13. Continue stirring the brine in the pressurized reactor 20 for at least 20 minutes.

[0060] In actual experiments, under conditions of 90℃ and 0.5 MPa, the ammonia conversion rate can reach 62% after 20 minutes of treatment with 30 mg / L NH4⁺ brine.

[0061] Step S20, flash steam stripping and ammonium removal, specifically includes:

[0062] S21. Flash evaporation and depressurization: The activated high-temperature and high-pressure brine is introduced into the flash evaporator 30 and is instantly depressurized to -0.09MPa (close to vacuum) through two-stage pressure reducing valves. The first stage depressurizes to 0.1MPa and the second stage depressurizes to -0.09MPa, thereby generating ammonia vapor bubbles in the flash evaporator 30.

[0063] In the initial state (after completing step S13), ammonium ions in the brine have been partially converted into free ammonia and exist in the brine in a dissolved state. The brine enters the flash tower 30, which is in a near-vacuum state. The sudden pressure drop causes the saturation solubility of dissolved ammonia to drop sharply by 93.5%. The equilibrium partial pressure of ammonia is higher than the operating pressure, causing the dissolved ammonia to become supersaturated instantly and undergo explosive vaporization, forming a large number of ammonia vapor bubbles.

[0064] According to Henry's Law, the equilibrium partial pressure of ammonia after pressure reduction is ( ) and operating pressure ( )relation: (H = 0.76 MPa⋅L / mol). When At that time, gasification occurs spontaneously (the measured gasification rate reaches over 93.5%).

[0065] S22, Cyclone Stripping: Brine spirals downwards within flash tower 30, enhancing ammonia separation. The separated ammonia comes into contact with low-temperature condensate at 5-10℃. This strengthens gas-liquid separation and prevents bubble aggregation and breakage. Simultaneously, the spirally descending brine, under centrifugal force, causes bubbles to rise tightly against the tower wall, extending their path without aggregation.

[0066] The bubble clusters are captured by the sprayed low-temperature condensate, and the concentration of ammonia in the gas phase drops sharply (from 15,000 ppm to below 200 ppm). The swirling flow field increases the gas-liquid mass transfer coefficient to 1.8 times that of a conventional straight column.

[0067] Step S30, zeolite ion capture, specifically includes:

[0068] S31. Zeolite treatment: Modified clinoptilolite is used, and the modified clinoptilolite is preloaded with potassium ions.

[0069] First, select the materials:

[0070] Natural clinoptilolite is selected, and after crushing and screening, clinoptilolite with a particle size of 1-2 mm is selected.

[0071] Then, acid washing and activation are performed:

[0072] The selected clinoptilolite was soaked in a 3 mol / L hydrogen chloride solution with a solid-liquid ratio of 1:5 and stirred at 80°C for 2 hours.

[0073] Then rinse with clean water until neutral (pH=6-7) to remove clogging ions such as iron and calcium ions.

[0074] Acid washing and activation can increase the specific surface area from 350 m² / g to 420 m² / g and the micropore volume by 40%.

[0075] Preload potassium ions:

[0076] The acid-washed and activated clinoptilolite was immersed in a 1.5 mol / L potassium chloride solution with a solid-liquid ratio of 1:4 and shaken at 60°C for 4 hours. After completion, it was washed with water to remove free potassium ions from the surface.

[0077] Final thermal stabilization:

[0078] Dry at 120℃ for 2 hours, then sieve to remove debris, ensuring that more than 95% of the particles are intact.

[0079] Modified clinoptilolite is the core material for deep deammoniation in this invention. By performing dual modification of natural zeolite through acid activation and potassium ion preloading, its selective adsorption capacity for NH4⁺ is significantly improved.

[0080] Acid washing and pore enlargement expose more negatively charged sites in the silicon-aluminum framework. After potassium ion preloading, the radii of potassium ions are more matched with those of ammonium ions (K⁺=138 pm, NH₄⁺=143 pm), thereby improving selectivity through the synergistic effect of size sieving and electrostatic attraction.

[0081] S32, Ion exchange reaction, capturing residual ammonia ions in brine through ion exchange. The flash-distilled brine is introduced into zeolite reactor 40, where residual ammonium ions in the brine are exchanged through modified clinoptilolite preloaded with potassium ions.

[0082] The modified zeolite preloaded with potassium ions exhibits a selectivity of 3.2-3.5 for ammonium ions, thus preferentially adsorbing ammonium ions and undergoing the reaction: zeolite-K+ Zeolite - + .

[0083] During the operation, the flash-evaporated brine is passed through the zeolite bed at an empty tower flow rate of 8 m / h, and the contact time is controlled to be greater than or equal to 10 min, thereby reducing the residual ammonium ions in the brine to below 0.1 mg / L.

[0084] S33. Regeneration and recycling: After the modified clinoptilolite is saturated, it is washed with a 10% potassium chloride solution to obtain an ammonium chloride solution. The ammonium chloride solution is concentrated and recycled. Ammonium chloride can be used as a fertilizer by-product.

[0085] During backwashing, first use a counter-current water flow at a rate of 2 BV / h to rinse for at least 5 minutes to remove particulate impurities.

[0086] Then, a 10% potassium chloride solution is passed through the zeolite bed at a flow rate of 1.5 BV / h for 60 minutes to release the ammonium ions adsorbed on the zeolite bed. Finally, the bed is rinsed with deionized water until the chloride ion concentration in the effluent is less than 10 mg / L.

[0087] In this embodiment, the entire hot-press cycle deammoniation method includes:

[0088] Safety benefits: The entire process is chlorine-free, with an ammonium ion concentration in the effluent of less than 0.1 mol / L, reducing the risk by 100% compared to traditional chlorination methods and completely eliminating the risk of NCl3 explosion. Furthermore, the maximum pressure throughout the process is only 0.5 MPa (Class III pressure vessel), and the temperature in all processes except for clinoptilolite treatment is below 100℃.

[0089] Environmental benefits: No waste residue is generated throughout the process, and the wastewater reuse rate can reach over 95%. Simultaneously, the removal rate of heavy metal ions by zeolite adsorption reaches over 90%. Furthermore, compared to traditional technologies, this technology reduces carbon emissions per ton of brine treated by 40%.

[0090] Resource recycling: Ammonium recovery rate >90%, potassium loss <2%, and by-product revenue covers 1 / 3 of operating costs.

[0091] Example 2:

[0092] like Figure 2As shown in the figure, this embodiment discloses a hot-pressurized circulating deammonium removal system for potassium chloride brine, which includes a plate heat exchanger 10, a pressurized reactor 20, a flash evaporator 30 and a zeolite reactor 40 connected in series.

[0093] The brine is heated to a specified temperature of 85-90°C after passing through the plate heat exchanger 10.

[0094] The heated brine then enters a pressurized reactor, where it undergoes thermal activation. The pressure inside the pressurized reactor reaches 0.3-0.5 MPa. A stirrer is also installed inside the pressurized reactor to agitate the brine.

[0095] The hot-pressed activated brine enters flash distillation tower 30, where free ammonia is separated from the brine. Finally, residual ammonia ions in the brine are exchanged and captured in zeolite reactor 40.

[0096] Specifically, such as Figure 3 As shown, the flash evaporator 30 includes a tank 31, a sprayer 32, a spiral guide plate 33, and an annular liquid collection tank 34.

[0097] The tank body 31 has a feed inlet 35 located in the middle of its wall. Brine enters the tank body 31 through the feed inlet 35, which is tangentially positioned along the inner wall of the tank body 31, ensuring the brine enters tangentially as well. Preferably, the feed inlet 35 of the tank body 31 is equipped with a pressure-reducing valve, allowing the brine to release pressure instantaneously upon entering the tank body 31.

[0098] A spiral guide plate 33 is positioned below the feed inlet 35, and the spiral direction of the spiral guide plate 33 is the same as the flow direction of the brine on the inner wall of the tank 31, causing the brine to flow along the top surface of the spiral guide plate 33 within the tank 31. Preferably, the upper surface of the spiral guide plate 33 has a concave structure. By setting the spiral guide plate 33, ammonia bubbles are caused to rise against the current due to buoyancy, extending the path of gas-liquid contact in the swirling flow field.

[0099] Sprayer 32 is located on the top of tank 31. Sprayer 32 sprays low-temperature condensate (5-10℃) downwards to absorb ammonia and generate dilute ammonia water with a concentration of about 8%.

[0100] The annular liquid collection tank 34 is located above the spiral guide plate 33 and the feed inlet 35, and below the sprayer 32. A level gauge is installed in the annular liquid collection tank 34, and a pneumatic drain valve is installed at the outlet.

[0101] Dilute ammonia water is collected by setting up an annular collection tank 34. When the liquid level in the collection tank reaches the designated position, the pneumatic drain valve is activated to discharge the dilute ammonia water.

[0102] Preferably, an annular umbrella cover 36 is provided above the spiral guide plate 33, and the edge of the annular collection tank 34 is located below the edge of the umbrella cover 36. By providing the umbrella cover 36, dilute ammonia water can be prevented from falling onto the spiral guide plate 33 and mixing with the brine.

[0103] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for hot-pressing and circulating deammonium removal from potassium chloride brine, characterized in that, Includes the following steps: S10, thermal pressure ion activation, through a high temperature and high pressure environment, promotes the conversion of ammonium ions in the brine into free ammonia; S20, flash vaporization removes ammonium by depressurizing free ammonia and absorbing the vaporized ammonia with low-temperature condensate; S30, zeolite ion capture, which involves reacting the brine from step S20 with zeolite to capture residual ammonium ions in the brine through ion exchange; Specifically, step S10, hot-pressing ion activation, includes: S11. Preheat the brine to 85-90℃; S12, pressurized circulating reaction, steam at a pressure of 0.3-0.5 MPa is introduced into the container containing the brine; S13. Continue stirring; Step S20, flash steam stripping of ammonium, specifically includes: S21. Flash evaporation and depressurization: The activated brine is introduced into the flash evaporator and is instantly depressurized to -0.09MPa through two stages of pressure reducing valves. The first stage depressurizes to 0.1MPa and the second stage depressurizes to -0.09MPa, thereby generating ammonia vapor bubbles in the flash evaporator. S22, cyclone stripping: brine spirals down in the flash tower and comes into contact with low-temperature condensate at 5-10℃; Step S30, zeolite ion capture, specifically includes: S31. Zeolite treatment: Acid activation and potassium ion preloading of natural clinoptilolite. S32, Ion exchange reaction, captures residual ammonium ions in brine through ion exchange.

2. The hot-pressing cyclic deammoniation method according to claim 1, characterized in that: In step S11, the brine is preheated by a plate heat exchanger. In step S12, the preheated brine is introduced into the pressurized reactor, and then steam is introduced into the pressurized reactor. In step S13, the brine is continuously stirred in the pressurized reactor for at least 20 minutes.

3. The hot-pressing cyclic deammoniation method according to claim 1, characterized in that, The step S30 zeolite ion capture also includes: S33. Regeneration and recycling: After the modified clinoptilolite is saturated, it is washed with a 10% potassium chloride solution to obtain an ammonium chloride solution. The ammonium chloride solution is concentrated and recycled.

4. The hot-pressing cyclic deammoniation method according to any one of claims 1-3, characterized in that, The hot-press cyclic deammonium removal method is implemented using a hot-press cyclic deammonium removal system, which comprises, in series: Plate heat exchangers are used for heating brine. A pressure reactor is used to pressurize heated brine, and a stirrer is installed inside the pressure reactor. Flash distillation towers are used to separate free ammonia from brine. Zeolite reactors are used to exchange and capture residual ammonium ions in brine. The flash evaporator includes: The tank has a tangential inlet in the middle of its wall, an outlet at its bottom, and a gas outlet at its top. A pressure reducing valve is provided on the inlet of the tank. A sprayer is located at the center of the top of the tank and sprays condensate downwards. A spiral guide plate is disposed on the inner wall of the tank and located below the feed inlet; An annular liquid collection tank is located in the middle of the tank body and below the sprayer.

5. The hot-pressing cyclic deammoniation method according to claim 4, characterized in that, An annular umbrella cover is provided above the spiral guide plate, and the edge of the annular liquid collection tank is located below the edge of the umbrella cover.

6. The hot-pressing cyclic deammoniation method according to claim 4, characterized in that: The upper surface of the spiral guide plate has a concave structure.

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