GB2619836A

GB2619836A - Recovery method and recovery system for ternary precursor mother liquor

Info

Publication number: GB2619836A
Application number: GB2314020.5A
Authority: GB
Inventors: Yu Haijun; Xie Yinghao; Li Aixia; Zhang Xuemei; Li Changdong
Original assignee: Hunan Brunp Recycling Technology Co Ltd; Guangdong Brunp Recycling Technology Co Ltd; Hunan Bangpu Automobile Circulation Co Ltd
Current assignee: Hunan Brunp Recycling Technology Co Ltd; Guangdong Brunp Recycling Technology Co Ltd; Hunan Bangpu Automobile Circulation Co Ltd
Priority date: 2022-03-18
Filing date: 2022-11-14
Publication date: 2023-12-20
Anticipated expiration: 2042-11-14
Also published as: CN114620881A; WO2023173776A1; GB202314020D0; GB2619836B; DE112022002529T5; HUP2400079A1

Abstract

Disclosed are a recovery method and recovery system for a ternary precursor mother liquor. The recovery method for a ternary precursor mother liquor provided in the present invention comprises the following steps: S1, reacting sulfide ions with a ternary precursor mother liquor, and then performing solid-liquid separation; S2, reacting an oxidant with liquid phase components obtained in step S1, and then performing solid-liquid separation; S3, treating, with quicklime, liquid phase components obtained in step S2, and collecting obtained gas; S4, performing, with sulfur dioxide, aeration treatment on a residual mixture in step S3, and then performing solid liquid separation; and S5, performing crystallization treatment on liquid phase components obtained in step S4. According to the recovery method for a ternary precursor mother liquor of the present invention, solutes in the ternary precursor mother liquor can be converted into products having high economic benefits; meanwhile, the treated ternary precursor mother liquor has few impurities, and high environmental protection benefits are achieved. The present invention further provides a recovery system for implementing the recovery method.

Description

RECOVERY METHOD AND RECOVERY SYSTEM OF TERNARY PRECURSOR MOTHER LIQUOR

FIELD

c [0001] The present disclosure belongs to the technical field of wastewater treatment, and specifically relates to a recovery method and a recovery system of ternary precursor mother liquor

BACKGROUND

[0002] In recent years, the rapid development of the commercialization of electric vehicles has brought about a rapid growth in the market demand for power batteries. Power lithium batteries comprising ternary positive electrode materials are gradually occupying an important position in the power battery industry due to their high capacity, high energy density, good cycle stability, and moderate cost.

[0003] At present, industrial ternary positive electrode materials are generally prepared by calcination of Ni, Co, and Mn hydroxides (Ni"CobNInib(OH)2) as precursors with lithium. The mainstream process for preparing ternary material precursors is co-precipitation, that is, adding metal salt (usually sulfate) solution containing Ni2-Co2+ and Mn2-, NaOH solution (as a precipitating agent) and ammonia water (as a complexing agent, and NH3.H20 is the main form in ammonia water) in parallel and co-precipitating to produce spherical ternary hydroxide precursor. This process can easily control the particle size, specific surface area, morphology and tap density of the precursor, but will generate a large amount of waste water (ternary precursor mother liquor). For every ton of precursor produced, 9 to 20 cubic meters of ternary precursor mother liquor is generated (industry experience). The increase in production capacity results in a huge amount of ternary precursor mother liquor generated, which needs to be recycled and utilized by designing a method.

[0004] According to the above analysis, due to the limited solubility product, a certain amount of Ni2+, Co2+, Mn2+ and NaOH will undoubtedly remain in ternary precursor mother liquor, and also a large amount of NH3 -H20 and Na2SO4. In the presence of NH3 -H20, metal ions may exist freely or form complex metal ions with ammonia. In addition, there will be a certain amount of solids (precursors with small particle sizes that are not separated, equivalent to colloidal particles and accounting for about 1-5% of the total weight). Therefore, ternary precursor mother liquor has the characteristics of high heavy metal content, high ammonia nitrogen concentration (the sum of ammonia water and ammonium ions), high salt content and high alkalinity Heavy metals and ammonia contained in ternary precursor mother liquor have high economic benefit, and direct discharge of them will cause economic losses. Moreover, complex components such as heavy metal ions and alkalis have a great impact on the surrounding environment, and direct discharge also poses environmental risks [0005] In the related art, the treatment of ternary precursor mother liquor usually comprises sending it into a stripping ammonia-removing tower to perform stripping ammonia-removing, recovering the ammonia water therein, then removing heavy metals such as Ni, Co and Mn by settling, and then filtering and recovering the heavy metals, and finally, sending to the MVR (mechanical vapor recompression) system, evaporating and concentrating to recover Na2SO4 (usually containing crystal water) to prepare pure water for reuse. Although this process enables the comprehensive recovery and utilization of mother liquor wastewater and has environmental benefit, stripping ammonia-removing needs to consume a lot of steam, and the content of ammonia in the effluent is about 10 mg/L and the content of heavy metal ions is about 3 mg/L, making direct discharge posing environmental risks. In addition, preparing Na2SO4 by evaporation and concentration with MVR has high energy consumption, and the prepared sodium sulfate has low economic value in the market, with the market price of about 500 yuan/ton. Due to the poor overall economy, most manufacturers choose to discharge it and pay a certain water treatment fee.

[0006] In brief, the existing recovery method does not completely treat the ternary precursor mother liquor, and the economic benefit is poor.

SUMMARY

[0007] The present disclosure aims to solve at least one of the above-mentioned technical problems existing in the prior art. For this reason, the present disclosure proposes a method for recovering ternary precursor mother liquor, which can convert the solute in the ternary precursor mother liquor into a product with high economic benefit, and meanwhile, the treated ternary precursor mother liquor contains few impurities and has high environmental benefit.

100081 The present disclosure also provides a recovery system for uplementing the above method.

100091 According to one aspect of the present disclosure, a method for recovering ternary precursor mother liquor is proposed, comprising steps of [00101 S I. reacting the ternary precursor mother liquor with sulfur ions (52-) and performing solid-liquid separation to obtain a liquid phase component, 100111 S2. reacting the liquid phase component obtained in step Si with an oxidant and performing solid-liquid separation to obtain a liquid phase component; 100121 S3. treating the liquid phase component obtained in step S2 with quicklime (Ca0) and collecting gas; [0013] S4. subjecting a mixture remaining in step S3 to aeration with sulfur dioxide (SO2) and performing solid-liquid separation to obtain a liquid phase component; and [0014] S5. performing crystallization treatment on the liquid phase component obtained in step S4.

[0015] The mechanism of the recovery method is explained as follows: 100161 Step Si: Ternary precursor mother liquor contains a certain amount of Ni2+, Co2+, Mn2 NaOH and solids (precursors with small particle sizes that are not separated, which can be regarded as colloidal particles) and a larger amount of NH3-1420 and Na2504. Due to the complexation of a large amount of NH3, even under higher pH conditions, Ni2+ and Co2+ will not precipitate, but exists in the form of complex metal ions and some suspended Ni(OH)2 and Co(OH)2 with small particle size; [0017] NiS and CoS have smaller solubility products and are easier to precipitate than Ni(OH)2 and Co(OH)2. Therefore, in the present disclosure, reacting the ternary precursor mother liquor with sulfur ions (S2-) will generate NiS and CoS precipitation, which will be separated from the liquid phase system during solid-liquid separation. The specific reactions that occur include: -3 - [0018] Ni2 +52-=Ni5; and 100191 Co2++52-=CoS,[.

[0020] In addition, the ternary precursor mother liquor has suspended metal hydroxides with small particle size, which is equivalent to a colloidal system. Therefore, the externally introduced sulfur ions will also destroy the stability of the original colloidal system and cause the colloidal particles in it to coagulate.

[0021] That is to say, by adding only a small amount of sulfide ions, most of the metal elements can be separated from the system of the ternary precursor mother liquor.

[0022] Step 82: Since the precipitation equilibrium constant of MnS is greater than that of Mn(OH)2, manganese will not be precipitated in the form of MnS in step Sl. Therefore, the liquid phase component obtained in step 51 contains Mn2-1, Mn(OH)2 with small particle size, and unreacted S2-, NI-I3 -H20 and Na2504 in step S I. After treatment with the oxidant, manganese in Mn2 and Mn(OH)2 with small particle size will be converted from +2 valence to +4 valence, forming Mn02 precipitation, which will be separated from the liquid phase system in the form of solid phase, and the residual S2-will also be oxidized to S042-under the action of the oxidant.

[0023] Step S3: The liquid phase component obtained in Step S2 contains a large amount of Na2SO4 and NH3. Ammonia is easily soluble in water to form NH3. H20, so the commonly used stripping ammonia-removing has high energy consumption and limited treatment effect. In the present disclosure, CaO is used to treat the liquid phase component obtained in step S2. The reaction of CaO and H20 releases a large amount of heat and generates an alkaline substance Ca(OH)2, wherein the heat can promote the decomposition of N143-H20 to generate NH3 which can escape from the liquid phase system, and Ca(OH)2 can inhibit the combination of NH3 and water to form NH3-H20 (inhibit the reverse reaction). In this step, NH3 (which may contain a certain amount of water vapor) is separated from the liquid phase system in the form of gas. The reactions that occur include: [0024] NH3.H20+Ca0=NH3 I +Ca(OH)2 [0025] Step S4: The mixture obtained in step S3 includes a large amount of Na2504 and generated Ca(OH)2 in the reaction of step S3, and also includes calcium sulfate precipitate formed by the combination of calcium ions and sulfate ions, making it difficult to separate the substances. In step 54, treating the mixture obtained in step 53 with SO2 can convert Ca(OH)2 into CaSO4-2H20 (precipitation of gypsum) and generate Na2SO4 at the same time, which also makes the reaction more complete. The reactions that occur include: 100261 Ca(OH)4±S02=CaSO4+1-140; [0027] S02+H20+CaS03=Ca(HS03)24 [0028] Ca(H503)2+Na2504+2H20=2NaH503-CaSO4-2H20,1,; and 100291 4NaHS03+3Ca(OH)2+2H20-2Na0H+Na2S03+3CaS03.2H20.

[0030] Step S5: The liquid phase component obtained in step S4 contains a large amount of Na2S03. After crystallization treatment, solid Na2S03 (which may contain a certain amount of crystallization water according to the crystallization conditions) and the treated ternary precursor mother liquor are obtained.

[0031] According to a preferred embodiment of the present disclosure, it has at least the following beneficial effects: [0032] (1) In the conventional treatment method, the additional products obtained from ternary precursor mother liquor mainly include NH3 and Na2SO4, and the price of Na2SO4 is about 500 yuan/ton; [0033] In the present disclosure, in addition to NH3, the products also includes CaSO4*2H20 and Na2503, and the market price of Na2503 is higher than 4000 yuan/ton, which has higher economic benefit compared with Na2SO4 produced by conventional technology [0034] (2) In the present disclosure, the liquid phase component obtained in step S2 is treated with CaO to obtain NH3, which omits the application of steam and has a simpler operation and lower energy consumption compared with the conventional stripping ammonia-removing method. ;[0035] (3) In the present disclosure, through the cooperation between the steps and the raw materials, the content of ammonia nitrogen in the treated ternary precursor mother liquor is < mg/L, and the sum of the content of heavy metal ions (Ni2+, Co2+ and Mn2-) < 2.5 mg/L. Compared with the conventional treatment method, the impurities in the obtained water are greatly reduced, which has significant environmental benefit; -5 - [0036] Furthermore, in the additional products obtained by the present disclosure, NiS, CoS and Mn02 can all be used for the preparation of positive electrode materials, catalysts and other materials for lithium batteries (or need to be converted before use), NH3 can be reused for the preparation of ternary precursor. Na2S03 can be widely used in industries such as textiles, printing and dyeing, leather making and papermaking, and the prepared CaSO4*2H20 can be widely used in building materials, cement raw materials, rubber, plastics, fertilizers, pesticides, paints, textiles, food, medicine, papermaking, daily chemicals, arts and crafts, culture and education industries and the like. In a word, the recovered by-products have high practical value, and thus the recovery method provided by the present disclosure has high economy and practicability.

[0037] In some embodiments of the present disclosure, the composition of the ternary precursor mother liquor comprises 6-8 g/L of ammonia nitrogen, Ni, Co and Mn with a total amount of <500 mg/L, and 100-I 20 g/L of Na2SO4, pH> I 2.

100381 In some embodiments of the present disclosure, in step Si, a ratio of the amount of substance of the sulfur ions to the volume of the ternary precursor mother liquor is 0.035-0.11 mol/m3.

[0039] In some embodiments of the present disclosure, in step Si, the source of S2-includes at least one of sodium sulfide (Na2S) and potassium sulfide.

100401 In some embodiments of the present disclosure, in step Si, the source of s2 includes sodium sulfide (Na2S).

[0041] In the case that the source of S2-is sodium sulfide (Na2S), the purity of the sodium sulfite obtained in step S5 is higher, and impurities introduced by other sources of S2-can be avoided.

[0042] In some embodiments of the present disclosure, in the case that the source of S2-is Na2S, a ratio of the mass of Na25 to the volume of the ternary precursor mother liquor is 5-15 g/m3.

[0043] In some embodiments of the present disclosure, in step S I, the method for the solid-liquid separation includes at least one of settlement and filtration.

[0044] In some embodiments of the present disclosure, in step S2, a ratio of the amount of substance of the oxidant to the volume of the liquid phase component obtained in step Si is 2-3 100451 In some embodiments of the present disclosure, in step S2, the oxidant includes at least one of hydrogen peroxide (H,02) and sodium peroxide.

[0046] In some preferred embodiments of the present disclosure, in step S2, the oxidant includes hydrogen peroxide (11202).

[0047] In some embodiments of the present disclosure, in the case that the oxidant is H202 and S2-is derived from Na2S, the reactions that occur in step S2 include: [0048] Na25+4H202=Na2SO4+4H20; and 10 [0049] Mn(OH)2-4-1202=Mn02[,±21-120.

[0050] In some embodiments of the present disclosure, in step S2, the method for the solid-liquid separation includes at least one of settlement and filtration.

[0051] In some embodiments of the present disclosure, in step 52, in the case that the method for solid-liquid separation includes settlement, the required settling time is 30-60 min. [0052] In some embodiments of the present disclosure, in step 53, a ratio of the mass of CaO to the volume of the liquid phase component obtained in step S2 is 40-55 g/L.

100531 In some embodiments of the present disclosure, in step S3, collecting gas comprises blowing gas to a mixed system obtained after treating with CaO and collecting the blown gas by condensation.

100541 In some embodiments of the present disclosure, the blown gas comprises air.

[0055] In some embodiments of the present disclosure, the flow rate of the air is 60-120 L/min.

[0056] In some embodiments of the present disclosure, blowing gas to the mixed system obtained after treating with CaO is carried out for 3-6 h. [0057] Blowing gas to the mixed system obtained after treating with Cala can blow the produced NH3 out of the system in time, suppress the reaction of NH3 with water as much as possible, and improve the recovery rate of NH3.

[0058] The sodium sulfate contained in the liquid phase component obtained in step S2 will also inhibit the generation of NH3 to a certain extent (the reaction of sodium sulfate and calcium generates slightly soluble calcium sulfate, which hinders the progress of the reaction), and blowing gas can promote the contact between the quicklime and the liquid phase component, which weakens the influence of Na2SO4 to a certain extent.

[0059] Blowing gas to the mixed system obtained after treating with CaO can also increase the contact between CaO and the liquid phase component obtained in step S2 and promote the generation of NH3.

100601 In some embodiments of the present disclosure the condensation takes place in a condenser.

[0061] In step S3, the gas obtained by condensation is mainly NH3, which can be recycled to prepare new ternary precursors, and the gas that fails to condense is mainly the air introduced by blowing gas and can be directly discharged from the system, or it can be recycled to blow gas to the mixed system obtained after treating with CaO, so as to achieve the purpose of saving costs.

[0062] In some embodiments of the present disclosure, in step S4, the flow rate of the aeration is 601 20 Limin.

[0063] In some embodiments of the present disclosure, the pH of the mixture obtained after the aeration is 6-7 [0064] When the pH of the mixture obtained after the aeration is 6-7, the aeration is stopped.

[0065] In some embodiments of the present disclosure, in step S4, after the unreacted SO2 escapes from the reaction system, it can be collected again for the aeration, so as to save costs.

[0066] In some embodiments of the present disclosure, in step S4, the method for solid-liquid separation includes filtration; preferably, the filtration includes at least one of atmospheric filtration and pressure filtration.

100671 Before the solid-liquid separation in step 53, the system contains lime milk (slightly soluble Ca(OH)2 as the main component) and Na2SO4, and it is difficult to directly process the mixture of the two. Therefore, step S4 is added, in which the two are converted into water-soluble Na2S03 and water-insoluble CaSO4.2H20. On the one hand, it facilitates the solid-liquid separation of each component, and on the other hand, the obtained products have higher -g -economic value, which improves the economy of the recovery method.

100681 In some embodiments of the present disclosure, in step S5, the crystallization treatment includes evaporative concentration, cooling crystallization, solid-liquid separation and solid-phase drying, which are performed successively [0069] In step S5, the water evaporated by evaporative concentration and solid-phase drying and the clear liquid produced by solid-liquid separation are the ternary precursor mother liquor after the treatment by the recovery method.

[0070] According to yet another aspect of the present disclosure, a recovery system of ternary precursor mother liquor is provided for implementing the recovery method.

100711 The recovery system comprises a mother liquor tank, a first filter, a settling tank, a second filter, an ammonia-removing tower, a filter press and a crystallization system connected in sequence via a pipeline.

100721 According to a preferred embodiment of the present disclosure, the recovery system has at least the following beneficial effects: [0073] Through the setting of the recovery system, the present disclosure can fully utilize the raw materials and recover the by-products, with good economic and environmental benefits.

[0074] In some embodiments of the present disclosure, a blast blower is connected to the ammonia-removing tower.

[0075] In some embodiments of the present disclosure, a condenser is connected to the 20 ammonia-removing tower.

[0076] In some embodiments of the present disclosure, the condenser is provided with an exhaust port and a liquid discharge port.

[0077] In some embodiments of the present disclosure, the condenser arid the blast blower are connected via the pipeline.

100781 In some embodiments of the present disclosure, when the recovery method is implemented with the recovery system, the recovery method comprises steps of: [0079] S I Adding S2-into the mother liquor tank storing the ternary precursor mother liquor for precipitation reaction; 100801 Transferring the obtained mixture to the first filter via the pipeline for filtration pretreatment to obtain a filter cake (NiS and CoS) and the liquid phase component obtained in step Si; [0081] S2. Transferring the liquid phase component obtained in step S I to the settling tank via the pipeline, adding the oxidant to the settling tank, settling after the reaction, and transferring the mixture obtained in this step to the second filter via the pipeline for filtration to obtain filter residue (1v1n02) and the liquid phase component obtained in step S2; [0082] S3. Sending the liquid phase component obtained in step S2 into the ammonia-removing tower via the pipeline, and adding Ca0 to the ammonia-removing tower to generate NH3; [0083] Starting the blast blower to blow air into the ammonia-removing tower, in which the generated NH3 escapes from the ammonia-removing tower along with the air and is transferred to the condenser, operating the condenser to condense NH3 into a liquid (ammonia water NH3 1120), which is recovered from the liquid discharge port, and blowing the air along the pipeline through the blast blower continuously to the ammonia-removing tower until the blowing ends, exhausting the air from the system through the exhaust port.

[0084] S4. Through the blast blower, subjecting the liquid phase component obtained in step S3 to aeration with SO2, in which the flow path of SO4 is the circulation of the blast blower, the ammonia-removing tower, the condenser and the ammonia-removing tower, during which the condenser does not work; stopping the aeration when the pH value in the ammonia-removing tower is 6-7, and recovering the remaining SO4 from the exhaust port.

[0085] Then transferring the mixture in the ammonia-removing tower to the filter press via the pipeline for solid-liquid separation to obtain a filter cake (gypsum) and liquid phase component obtained in step 54; [0086] S5. Transferring the liquid phase component obtained in step S4 to the crystallization system via the pipeline for crystallization to obtain Na2503 and the treated ternary precursor mother liquor.

BRIEF DESCRIPTION OF DRAWINGS

100871 The present disclosure is further described below in conjunction with the drawings and embodiments, in which: [00881 FIG. 1 is a schematic structural diagram of a recovery system used in Example 1 of the present disclosure.

[0089] Reference numbers in the drawings are listed as follows: 100901 100, mother liquor tank; 200, first filter; 300, settling tank; 400, second filter; 500, ammonia-removing tower, 510, blast blower, 520, condenser, 521, liquid discharge port, 522, exhaust port; 600, filter press; 700, crystallization system; and 800, pipeline.

DETAILED DESCRIPTION

[0091] Hereinafter, the concept of the present disclosure and the technical effects produced by the present disclosure will be described clearly and completely in conjunction with the embodiments, so as to fully understand the purpose, features and effects of the present disclosure.

It is apparent that the described embodiments are only a part of the embodiments of the present disclosure, rather than all of them. All the other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without any creative work fall into the scope of the present disclosure.

[0092] In the description of the present disclosure, the meaning of several means one or more and the meaning of multiple means two or more. Greater than, less than, exceeding, etc. are understood as not including this number, while above, below, within, etc. are understood as including this number. If there are descriptions about the first and second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance, or implicitly indicating the number of the indicated technical features or the order of the indicated technical features.

[0093] In the description of the present disclosure, unless otherwise clearly defined, words such as setting, installation and connection should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present

- -

disclosure in combination with the specific content of the technical solution.

100941 Unless otherwise specified, the ternary precursor mother liquor used in the present disclosure comprises 8 g/L of ammonia nitrogen, Ni, Co and Mn with a total amount of about 38 mg/L, and about 120 g/L of Na2SO4, with a pH of 12.3.

Example 1

[0095] In this example, a ternary precursor mother liquor was recovered with a recovery system as shown in FIG. 1 by the following specific process: [0096] Si. The ternary precursor mother liquor was collected in mother liquor tank 100, and Na2S was added to mother liquor tank 100 for settlement. The ratio of the mass of Na25 to the volume of the ternary precursor mother liquor was 5 g/m3.

[0097] After settling, the mixture in mother liquor tank 100 was transferred to first filter 200 via pipeline 800 for filtration, and a filter cake with NiS and CoS as the main components as well as filtrate were obtained. The filter cake was then discharged from first filter 200 (indicated by the downward arrow of first filter 200 in HG. 1).

[0098] The filtrate obtained in this step comprised 8 g/L of ammonia nitrogen, Ni, Co and Mn with a total amount of about 10 mg/L, and about 120 g/L of Na2SO4, with a pH of 12.4.

[0099] 52. The filtrate obtained in step Si was transferred to settling tank 300 via pipeline 800, and,02 was added to settling tank 300 at a ratio of 2 molrn /3 H202of filtrate to settle for 30 mm, [00100] The mixture in settling tank 300 entered second filter 400 via pipeline 800. After the solid-liquid separation, a filter residue with Mn02 as the main component and filtrate were obtained. The filter residue was then discharged from second filter 400 (indicated by the downward arrow of second filter 400 in FIG. 1).

[00101] The filtrate obtained in this step comprised about 8 g/L of ammonia nitrogen, about 0.3 mg/L of Ni, about 0.3 mg/L of Co, about 0.1 mg/L of Mn, and about 122 g/L of Na2504.

[00102] S3. The filtrate obtained in step 52 was sent into ammonia-removing tower 500, and CaO was added to ammonia-removing tower 500. The ratio of the mass of CaO to the volume of the filtrate was 40 g/L.

-12 - [00103] Then blast blower 510 was started to blow air into ammonia-removing tower 500 at an air flow of 60 L/min for 6 h, during which a mixture of the generated NH3 and air entered condenser 520 (set temperature -15°C) from the top of ammonia-removing tower 500. Ammonia water condensed by condenser 520 (With the blowing, a part of water vapor would be brought out when ammonia was discharged, and ammonia itself also combined with a certain amount of water; therefore, after the condensation, ammonia water was generated instead of liquid ammonia) was discharged from it through liquid discharge port 521, and the gas that was not condensed (air) was continuously blown into ammonia-removing tower 500 by blast blower 510 along pipeline 800 for continuous circulation. The gas that was not condensed (air) after the end of the circulation was exhausted from condenser 520 through exhaust port 522.

[00104] In the ammonia water recovered in this step, the mass concentration of ammonia was 18.2%.

[00105] In the residual liquid phase component in ammonia-removing tower 500, the ammonia nitrogen was 8 mg/L, and the recovery rate of ammonia was greater than 99% (1 -ammonia nitrogen content in the liquid phase component obtained in this step/ammonia nitrogen content in the ternary precursor mother liquor).

[00106] 54. Through blasting blower 510, gas SO2 was blown into the mixture obtained in ammonia-removing tower 500 in step S3 at a flow rate of 60 L/min. When the pH in ammonia-removing tower 500 was 6-7, the blowing of SO2 was stopped. During the period, the unreacted SO2 entered blasting blower 510 through condenser 520 along the top of ammonia-removing tower 500, and was blown into ammonia-removing tower 500 again by blasting blower 510 for continues circulation. After the end of the circulation, the remaining SO2 was recovered from exhaust port 522.

[00107] After aeration with SO2, the mixture in ammonia-removing tower 500 was transferred to filter press 600 via pipeline 800 for filtration, and a filter cake gypsum (discharged from filter press 600, indicated by the downward arrow of filter press 600 in FIG. 1) and filtrate were obtained.

[00108] In this step, the gypsum comprised, by mass percentage content, 18.8% of Ca, 49.3% of S042-, 1.3% of Na, 1.9% of S032-, and 28.7% of water and other impurities (without drying). -3-

[00109] S5. The filtrate obtained in step S4 was transferred to crystallization system 700 via pipeline 800 and subjected to evaporative concentration, cooling crystallization and drying in sequence, and the product Na2S03 (the discharge path was shown in the right arrow of crystallization system 700 in FIG. I) was obtained.

[00110] The product sodium sulfite obtained in this step comprised, by mass percentage content, 95.7% of Na2S03, 0.7% of Ca, and 3.3% of S042-.

1001111 In this example, the components of the filtrate and filter cake obtained in each step and the results such as the recovery rate of ammonia nitrogen are summarized in Tables 1 to 3.

Example 2

1001121 In this example, a ternary precursor mother liquor was recovered. It differs from Example 1 specifically in the following aspects: 1001131 1) In step Si, the ratio of the mass of Na2S to the volume of the ternary precursor mother liquor was 10 g/m3, [00114] 2) In step S2, the ratio of the amount of substance of H202 to the volume of the filtrate was 2.5 mol/m3; [00115] 3) In step S3, the ratio of the mass of Ca0 to the volume of the filtrate was 50 g/L; [00116] 4) In step S3, blowing air was carried out at a flow rate of 90 L/min for 5 h; 1001171 5) In step S4, the flow rate of SO2 was 90 Lim n 1001181 (6) The components of the filtrate and filter residue obtained in each step and the recovery rate of ammonia nitrogen were different. The specific results are summarized in Tables 1-3.

Example 3

[00119] In this example, a ternary precursor mother liquor was recovered. It differs from Example I specifically in the following aspects: [00120] I) In step Si, the ratio of the mass of Na2S to the volume of the ternary precursor mother liquor was 15 gin?; [00121] 2) In step S2, the ratio of the amount of substance of H202 to the volume of the filtrate -14 -was 3 mains; 1001221 3) In step S3, the ratio of the mass of Ca0 to the volume of the filtrate was 55 g/1_,; [00123] 4) In step S3, blowing air was carried out at a flow rate of 120 L/min for 3 h; [00124] 5) In step S4, the flow rate of SO2 was 120 L/min; 1001251 (6) The components of the filtrate and filter residue obtained in each step and the recovery rate of ammonia nitrogen were different. The specific results are summarized in Tables 1-3. The results of Examples 1-3 illustrate that combined with the recovery system provided by the present disclosure, the recovery method provided by the present disclosure can fully recover heavy metal elements and ammonia nitrogen in ternary precursor mother liquor. After recovery, the content of heavy metal ions in the aqueous phase was < 0.5 mg/ L, and the content of ammonia nitrogen was < 8 mg/L.

1001261 For the convenience of comparison, the recovery of ammonia nitrogen in Examples 1-3 is summarized in Table 1.

Table 1 Mass concentration and recovery rate of ammonia recovered in the Examples 1-3 Example 1 Example 2 Example 3 Mass concentration of recovered ammonia % 18.2 19.6 20.3 Recovery rate of ammonia % 99.0 99.1 99.2 1001271 The mass percentage content of ammonia in the commercially available concentrated ammonia water is >15wt % (about 7.4 mol/L). The concentration of the ammonia water recovered by the present disclosure is 18.2-20.3% (9-10.01 mol/L). The concentration of the ammonia water used for preparing ternary precursor is generally 2-10 mol/L. 'that is, the concentrated ammonia water recovered by the present disclosure can be used for preparing ternary precursor directly or after dilution, which realizes the repeated utilization of ammonia water and has high economic benefit.

1001281 The present disclosure also summarizes the components of the gypsum obtained in Examples 1-3, as shown in Table 2.

Table 2 Component (by mass percentage content) of gypsum recovered in Examples 1-3 Example 1 Example 2 Example 3 Calcium % 18.8 19.3 19.6 S042-% 49.3 49.8 50.1 Na % 1.3 0.8 0.7 S032-% 1.9 1.5 1.7 Water and other impurities % 28.7 28.6 27.9 [00129] Results in Table 2 show that the gypsum recovered by the present disclosure had low content of sulfite. Therefore, the obtained gypsum had stable quality, and thus can meet the requirements of building materials, cement raw materials, rubber, plastics, fertilizers, pesticides, paints, textiles, food, medicine, papermaking, daily chemicals, arts and crafts, culture and education industries and the like, which can obtain huge economic benefit [00130] The present disclosure also summarizes the components of the sodium sulfite obtained in Examples I -3, as shown in Table 3.

Table 3 Component (by mass percentage content) of sodium sulfite recovered in Examples 1-3 Example 1 Example 2 Example 3 Na2S03 % 95.7 96.1 96.3 Ca % 0.7 0.8 0.8 S042 1⁄4 3.3 2.7 2.6 [00131] Results in Table 3 show that the sodium sulfite recovered by the present disclosure had a high purity and can be widely used in industries such as textiles, printing and dyeing, leather making and papermak ng, which can obtain huge economic benefit. -16-

[001321 The embodiments of the present disclosure have been described in detail above in conjunction with the drawings. However, the present disclosure is not limited to the above-mentioned embodiments. Various modifications can be made without departing from the purpose of the present disclosure within the scope of knowledge possessed by those of ordinary skill in the art. In addition, in the case of no conflict, the embodiments of the present disclosure and the features in the embodiments may be combined with each other.

Claims

CLAIMS1. A method for recovering ternary precursor mother liquor, comprising steps of: Sl. reacting the ternary precursor mother liquor with sulfur ions and performing solid-liquid separation to obtain a liquid phase component; S2. reacting the liquid phase component obtained in step Si with an oxidant and performing solid-liquid separation to obtain a liquid phase component; 53, treating the liquid phase component obtained in step S2 with quicklime and collecting gas S4. subjecting a mixture remaining in step S3 to aeration with sulfur dioxide and performing solid-liquid separation to obtain a liquid phase component; and S5. performing crystallization treatment on the liquid phase component obtained in step S4.
2. The method according to claim I, wherein in step Si, a ratio of the amount of substance of the sulfur ions to the volume of the ternary precursor mother liquor is 0.035-0. I I mol/m3.
3. The method according to claim 1, wherein in step S2, a ratio of the amount of substance of the oxidant to the volume of the liquid phase component obtained in step 51 is 2-3 moUm3.
4. The method according to claim 1, wherein in step S3, a ratio of the mass of the quicklime to the volume of the liquid phase component obtained in step S2 is 40-55 g/L.
5. The method according to any one of claims 1 to 4, wherein in step 53, collecting gas comprises blowing gas to a mixed system obtained after treating with the quicklime and collecting gas by condensation.
6. The method according to claim 1, wherein in step S4, a flow rate of sulfur dioxide in the aeration is 60-120 L/min.
7. The method according to claim 1, wherein in step 54, a pH of the mixture obtained after c the aeration is 6-7.
8. A recovery system of ternary precursor mother liquor for mplement ng the method according to any one of claims 1 to 7, wherein the recovery system comprises a mother liquor tank (100), a first filter (200), a settling tank (300), a second filter (400), an ammonia-removing tower (500), a filter press (600) and a crystallization system (700) connected in sequence via a pipeline (SOO).
9. The recovery system according to claim 8, wherein a blast blower (510) is connected to the ammonia-removing tower (500).
10. The recovery system according to claim 8, wherein a condenser (520) is connected to the ammonia-removing tower (500).