Cobalt system raffinate treatment and resource utilization method

Abstract

The invention discloses a cobalt system raffinate treatment and resource utilization method, which aims at high-salt high-COD raffinate generated in a cobalt hydrometallurgy process, the high-salt high-COD raffinate firstly passes through an evaporation system, salt in waste water is concentrated and crystallized, mother liquor is dried, COD is selectively separated from generated distilled water through a nanofiltration unit, nanofiltration produced water is used for preparing industrial pure water, and the high-salt high-COD raffinate is recycled. Nanofiltration concentrated water can be repeatedly treated and utilized after being subjected to biochemical treatment and a filtering device, collaborative optimization of wastewater treatment and resource recovery is achieved, and pure water meeting the industrial standard is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a method for treating and recycling cobalt system raffinate. BACKGROUND

[0002] In the hydrometallurgical process, the raffinate saturated wastewater produced in the extraction process has the typical characteristics of high salt content and complex organic composition. The total dissolved solids (TDS) content of the wastewater is as high as 50 g / L, and often contains extraction agent residues (such as diisooctyl phosphate (P204), sulfonated kerosene) and organic phase degradation products (such as long-chain alkanes, phenolic substances), resulting in a significant increase in oil and chemical oxygen demand (COD) in the wastewater. Such production wastewater with high salinity, high oil content and high COD characteristics has obvious technical limitations when using existing conventional treatment methods.

[0003] The current high-salinity wastewater treatment technology mainly uses membrane system treatment method, that is, the wastewater is first concentrated by membrane, and then the concentrated water produced is introduced into an evaporation system to obtain by-product salt. However, this membrane concentration combined with evaporation treatment process has significant defects: as the salt concentration increases, crystallization phenomenon is easily produced in the membrane shell; at the same time, the organic matter such as oil in the wastewater will adhere to the membrane surface and internal pores. These phenomena not only reduce the membrane flux and increase the chemical cleaning frequency, but also seriously affect the service life of the membrane module. In addition, the distilled water after evaporation treatment needs to be returned to the front-end system for repeated evaporation, further increasing the operating cost.

[0004] Based on the above technical bottlenecks, it is urgent to develop an integrated process that can realize the synergistic effect of salt separation, organic matter removal and water resource reuse. In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a method for treating and recycling cobalt system raffinate, which is beneficial to prolong the service life of the membrane, especially the ceramic nanofiltration membrane.

[0006] The present application is implemented as follows:

[0007] In a first aspect, the present application provides a method for treating and recycling cobalt system raffinate, comprising the following steps:

[0008] Evaporation, the cobalt system raffinate to be treated is introduced into an evaporator for evaporation to obtain a mother liquor and a distillation component;

[0009] Nanofiltration, the distillation component passes through a nanofiltration unit to obtain nanofiltration product water with low COD concentration and nanofiltration concentrated water with high COD concentration;

[0010] In addition to the COD, the nanofiltration concentrated water is subjected to biochemical treatment and filtration by a biochemical system to obtain filtered concentrated water and filtered product water, the biochemical system comprising an anaerobic reaction tank, an aerobic reaction tank and a secondary sedimentation tank connected in sequence;

[0011] The nanofiltration product water is subjected to reverse osmosis by a reverse osmosis unit to obtain reverse osmosis product water and reverse osmosis concentrated water.

[0012] In an optional embodiment, the cobalt system raffinate to be treated is subjected to forced circulation evaporation and vacuum flash crystallization in sequence, and a vacuum pump is connected to the vacuum flash crystallization unit.

[0013] The evaporation temperature is 105-115°C.

[0014] The mother liquor is further subjected to drying treatment.

[0015] In an optional embodiment, in the nanofiltration step, the operating pressure of the nanofiltration unit is 0.9-1.2 MPa, the product water yield is 50-65%, the distillation component temperature is 25-30°C, and the pH value of the distillation component is adjusted to 3.8-4.2.

[0016] The nanofiltration unit comprises ceramic nanofiltration membranes.

[0017] In an optional embodiment, the COD content of the nanofiltration product water is 50-75 mg / L.

[0018] The COD content of the nanofiltration concentrated water is 600-900 mg / L.

[0019] In an optional embodiment, the biochemical treatment temperature is 25-40°C.

[0020] In the biochemical treatment step, the residence time of the nanofiltration concentrated water in the anaerobic reaction tank is 3.5-4.5 h, and the residence time in the aerobic reaction tank is 3.5-4.5 h.

[0021] The COD of the water discharged from the biochemical system is less than 65 mg / L.

[0022] In an optional embodiment, the filtration comprises sequentially subjecting the nanofiltration concentrated water after biochemical treatment to a multi-medium filter, a disc filter device and an ultrafiltration unit for filtration.

[0023] The filtered concentrated water is returned to the biochemical system for biochemical treatment, and the filtered product water is returned to the nanofiltration step for nanofiltration.

[0024] In an optional embodiment, in the reverse osmosis step, the operating pressure of the reverse osmosis unit is 2.3-3.0 MPa, and the product water yield is 75-90%.

[0025] And / or, the reverse osmosis concentrated water returns to the nanofiltration step, and the distillation components are subjected to nanofiltration treatment.

[0026] In an optional embodiment, the conductivity of the reverse osmosis water is < 10 muS / cm, and the turbidity is ≤ 0.1 NTU.

[0027] And / or, the COD concentration of the reverse osmosis concentrated water is 240 mg / L-280 mg / L.

[0028] In an optional embodiment, the concentration of magnesium ions in the cobalt system raffinate is 2000 mg / L-3000 mg / L, the concentration of sulfate ions is 15000 mg / L-25000 mg / L, the concentration of chloride ions is 450 mg / L-550 mg / L, the concentration of ammonium ions is 20000 mg / L-30000 mg / L, and the concentration of oil is 15 mg / L-20 mg / L.

[0029] In an optional embodiment, the operating pressure of the nanofiltration unit, reverse osmosis device, and ultrafiltration device is detected and adjusted: when the COD concentration of the nanofiltration water, filtration water, or reverse osmosis water increases, the frequency of the booster pump is reduced, and the operating pressure of the membrane is reduced.

[0030] And / or, when the operating pressure of the nanofiltration unit, ultrafiltration device, or reverse osmosis device increases, the nanofiltration unit, ultrafiltration device, and reverse osmosis device enter a shutdown state, the membrane cleaning unit is started, and the device with increased operating pressure is cleaned, and after cleaning, the nanofiltration unit, ultrafiltration device, and reverse osmosis device are started.

[0031] The present application has the following beneficial effects:

[0032] The present application provides a method for treating and recycling cobalt system raffinate, which is suitable for high-salt and high-COD raffinate generated in the cobalt hydrometallurgy process. The method first concentrates and crystallizes the salts in the wastewater through an evaporator, which facilitates the subsequent drying of the mother liquor. The distillate produced during evaporation is selectively separated by a nanofiltration unit, and the nanofiltration water is used to prepare industrial pure water. The nanofiltration concentrated water can be reused after biochemical treatment and filtration, achieving the synergistic optimization of wastewater treatment and resource recovery, and obtaining pure water that meets industrial standards. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those of ordinary skill in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0034] Figure 1 The flow chart of Example 1 in the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturer are adopted. If the manufacturers of the reagents or instruments are not indicated, they are all conventional products that can be purchased in the market.

[0036] In a first aspect, the present application provides a method for treating and recycling cobalt system raffinate, comprising the following steps:

[0037] Evaporation, making the cobalt system raffinate to be treated enter an evaporator for evaporation to obtain a mother liquor and a distillation component;

[0038] Nanofiltration, making the distillation component pass through a nanofiltration unit to obtain nanofiltration product water with low COD concentration and nanofiltration concentrated water with high COD concentration;

[0039] COD removal, adopting a biochemical system to perform biochemical treatment and filtration on the nanofiltration concentrated water to obtain filtered concentrated water and filtered product water, and the biochemical system comprises an anaerobic reaction tank, an aerobic reaction tank and a secondary sedimentation tank connected in sequence;

[0040] Reverse osmosis, making the nanofiltration product water pass through a reverse osmosis unit to obtain reverse osmosis product water and reverse osmosis concentrated water.

[0041] The present application provides a method for treating and recycling cobalt system raffinate. The high-salt high-COD raffinate generated in the cobalt hydrometallurgy process is first passed through an evaporator to concentrate and crystallize the salts in the wastewater, which is convenient for subsequent drying of the mother liquor. In the evaporation process, the distillation water generated is selectively separated by a nanofiltration unit, the nanofiltration product water is used to prepare industrial pure water, and the nanofiltration concentrated water can be repeatedly treated and utilized after biochemical treatment and filtration, realizing the synergistic optimization of wastewater treatment and resource recycling, and obtaining pure water meeting the industrial standards.

[0042] In an optional embodiment, the cobalt system raffinate to be treated is sequentially passed through a forced circulation evaporator and a vacuum flash crystallizer, and a vacuum pump is connected to the vacuum flash crystallizer;

[0043] and / or, the evaporation temperature is 105-115°C, for example 105°C, 106°C, 108°C, 110°C, 112°C, 114°C, 115°C;

[0044] and / or, further comprising drying the mother liquor to obtain a byproduct salt.

[0045] The high-salt raffinate enters the evaporator for concentration crystallization and drying to obtain a miscellaneous salt. The distillation components produced during evaporation contain part of the light component organic matter (COD content is about 300-400 mg / L), which cannot be directly reused and needs to be further treated. In the evaporator, the circulating evaporator first concentrates the dilute solution to a certain concentration, the concentrated solution enters the vacuum flash crystallizer, the vapor produced by flashing is removed by the vacuum pump to maintain the stability of the system, and the concentrated solution is further concentrated and crystallized in the crystallizer.

[0046] In an optional embodiment, in the nanofiltration step, the operating pressure of the nanofiltration unit is 0.9-1.2 MPa, the water production rate is 50%-65%, the distillation component temperature is 25-30°C, and the distillation component pH value is adjusted to 3.8-4.2.

[0047] In an optional embodiment, the operating pressure of the nanofiltration unit is 0.9-1.2 MPa, for example 0.9 MPa, 0.95 MPa, 1.0 MPa, 1.1 MPa, 1.15 MPa, or 1.2 MPa, which is the core driving force of nanofiltration and needs to balance the osmotic pressure and the membrane tolerance. This pressure range can effectively push the water molecules to pass through the membrane pores while retaining divalent ions and large molecular organic matter. Too low pressure will lead to a decrease in water production rate, and too high pressure will easily cause membrane pollution and damage, directly affecting the stable realization of the 50%-65% water production rate.

[0048] In an optional embodiment, the water production rate of the nanofiltration unit is 50%-65%, for example 50%, 53%, 56%, 59%, 62%, or 65%. The determination of the water production rate needs to take into account the water resource utilization rate and the membrane pollution risk. This range can avoid excessive enrichment of solutes in the concentrated solution, reduce the membrane flux decay caused by concentration polarization, and at the same time provide feed liquid with appropriate concentration for the subsequent distillation process. If the water production rate is too high, the concentrated solution is prone to super-saturation and cause fouling; if it is too low, the treatment efficiency is reduced, and it forms a dynamic match with the pressure of 0.9-1.2 MPa.

[0049] In optional embodiments, the distillation component temperature is 25-30℃, such as 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, which on one hand reduces the heating energy consumption (especially suitable for vacuum distillation), and on the other hand avoids the decomposition of heat-sensitive substances. This temperature is consistent with the normal temperature characteristics of the nanofiltration water production, reduces the fluctuation of the system thermal load, and at the same time cooperates with the weakly acidic environment (pH 3.8-4.2) to inhibit the precipitation of calcium and magnesium ions, preventing the distillation equipment from scaling.

[0050] In optional embodiments, the pH value is 3.8-4.2, such as 3.8, 3.9, 4.0, 4.1, 4.2, which can dissolve part of the metal hydroxide, protect the nanofiltration membrane and distillation equipment from corrosion, and at the same time promote the morphological stability of organic matter, improve the nanofiltration rejection rate and distillation separation efficiency. This parameter cooperates with the temperature to provide a stable chemical environment for the nanofiltration water production into the distillation link, and finally realizes the efficient operation of the whole process.

[0051] In optional embodiments, the nanofiltration unit includes a ceramic nanofiltration membrane, which is resistant to pollution and still maintains stable flux under the condition of pH < 7 and high COD, and is less susceptible to pollution than traditional nanofiltration membranes.

[0052] In optional embodiments, the COD content of the nanofiltration water production is 50-75 mg / L, such as 50 mg / L, 55 mg / L, 60 mg / L, 65 mg / L, 70 mg / L, 75 mg / L, which is relatively low and can be further treated by reverse osmosis to produce pure water.

[0053] In optional embodiments, the COD content of the nanofiltration concentrated water is 600-900 mg / L, such as 600 mg / L, 650 mg / L, 700 mg / L, 750 mg / L, 800 mg / L, 850 mg / L, 900 mg / L, which is relatively high and can be further treated in a biochemical treatment system to reduce COD.

[0054] In optional embodiments, the temperature of the biochemical treatment is 25-40℃, such as 25℃, 28℃, 31℃, 34℃, 37℃, 40℃;

[0055] And / or, in the biochemical treatment step, the residence time of the nanofiltration concentrated water in the anaerobic reaction tank is 3.5-4.5 h, such as 3.5 h, 3.7 h, 3.9 h, 4.1 h, 4.3 h, 4.5 h; and the residence time in the aerobic reaction tank is 3.5-4.5 h, such as 3.5 h, 3.7 h, 3.9 h, 4.1 h, 4.3 h, 4.5 h;

[0056] And / or, the COD of the water discharged from the biochemical system is less than 65 mg / L.

[0057] The biochemical system can be continuously operated stably under this condition, because the distillation component itself has a temperature, which can increase the temperature of the biochemical system, so that the operation of the biochemical system is not limited by the seasonal environmental temperature, solving the problems of difficult degradation of COD in traditional high-salt concentrated water and operation of the biochemical system being limited by temperature, and the COD removal rate can be reduced by 80% compared with the way of directly membrane separation or pure evaporation to obtain the distillation component.

[0058] In an optional embodiment, the filtration includes sequentially passing the nanofiltration concentrated water after biochemical treatment through a multi-medium filter, a disc filter device, and an ultrafiltration unit for filtration.

[0059] And / or, the filtered concentrated water is returned to the biochemical system for biochemical treatment, and the filtered water is returned to the nanofiltration step for nanofiltration.

[0060] The biochemical treatment of the distillation component contains some suspended solids, which are treated by the multi-medium filter, the disc filter device, and the ultrafiltration unit to obtain the filtered water, i.e. the ultrafiltration water, which can be transferred to the nanofiltration unit for treatment, and the filtered concentrated water can be returned to the biochemical unit to increase the recovery rate of water resources.

[0061] In an optional embodiment, in the reverse osmosis step, the operating pressure of the reverse osmosis unit is 2.3-3.0 MPa, and the water production rate is 75%-90%.

[0062] And / or, the reverse osmosis concentrated water is returned to the nanofiltration step for nanofiltration treatment together with the distillation component.

[0063] In an optional embodiment, the operating pressure of the reverse osmosis unit is 2.3-3.0 MPa, for example, the operating pressure of 2.3 MPa, 2.4 MPa, 2.6 MPa, 2.8 MPa, or 3.0 MPa is the core power of the reverse osmosis unit, which overcomes the osmotic pressure of the solution to push water molecules to penetrate the semi-permeable membrane and can intercept ions and small molecules; if the pressure is insufficient, the water production rate will drop sharply, and if the pressure is too high, the membrane structure may be damaged and the energy consumption will increase.

[0064] In an optional embodiment, the water production rate of the reverse osmosis unit is 75%-90%, for example, the water production rate of 75%, 78%, 81%, 84%, 87%, or 90% can balance the water resource utilization rate and the risk of membrane pollution: too high can easily cause concentration polarization and fouling, and too low will waste raw water.

[0065] The operating pressure and the water production rate are positively correlated, for example, the increase of the pressure can increase the water production rate, but it needs to be controlled within the range of membrane tolerance, so as to achieve efficient desalination and economy in cooperation, which is suitable for high-purity water preparation scenarios.

[0066] In an optional embodiment, the conductivity of the reverse osmosis water is <10 μS / cm, and the turbidity is ≤0.1 NTU, meeting the requirements of industrial standards.

[0067] In an optional embodiment, the COD concentration of the reverse osmosis concentrated water is 240 mg / L-280 mg / L, for example, 240 mg / L, 250 mg / L, 260 mg / L, 270 mg / L, 280 mg / L, which can be returned to the nanofiltration unit for further treatment.

[0068] In an optional embodiment, the concentration of magnesium ions in the cobalt system raffinate is 2000 mg / L-3000 mg / L, for example, 2000 mg / L, 2200 mg / L, 2400 mg / L, 2600 mg / L, 2800 mg / L, 3000 mg / L; the concentration of sulfate ions is 15000 mg / L-25000 mg / L, for example, 15000 mg / L, 17000 mg / L, 19000 mg / L, 21000 mg / L, 23000 mg / L, 25000 mg / L; the concentration of chloride ions is 450 mg / L-550 mg / L, for example, 450 mg / L, 475 mg / L, 500 mg / L, 525 mg / L, 550 mg / L; the concentration of ammonium ions is 20000 mg / L-30000 mg / L, for example, 20000 mg / L, 22000 mg / L, 24000 mg / L, 26000 mg / L, 28000 mg / L, 30000 mg / L; the concentration of oil is 15 mg / L-20 mg / L, for example, 15 mg / L, 16 mg / L, 17 mg / L, 18 mg / L, 19 mg / L, 20 mg / L.

[0069] The treatment method of the present application can be used for resource treatment of wastewater with high salinity, high oil content and high COD characteristics, and can obtain pure water meeting industrial standards.

[0070] In an optional embodiment, the operating pressure of the nanofiltration unit, reverse osmosis device and ultrafiltration device is detected and adjusted: when the COD concentration of the nanofiltration product water, filtration product water or reverse osmosis product water rises, the frequency of the booster pump is reduced, and the operating pressure of the membrane is reduced;

[0071] And / or, when the operating pressure of the nanofiltration unit, ultrafiltration device or reverse osmosis device rises, the nanofiltration unit, ultrafiltration device and reverse osmosis device enter a shutdown state, the membrane cleaning unit is started, and the device with rising operating pressure is cleaned. After cleaning, the nanofiltration unit, ultrafiltration device and reverse osmosis device start operating.

[0072] Monitoring whether the method is stable at any time is beneficial to avoid shortening the service life of the equipment caused by the increase of the operating pressure.

[0073] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0074] Embodiment 1

[0075] The embodiment provides a cobalt system raffinate treatment and resource utilization method, which specifically comprises the following steps: Figure 1 As shown in the figure, specifically comprising the following steps:

[0076] (1) The high-salt raffinate is evaporated and concentrated in the MVR evaporator, the produced mother liquor is dried, and the distillation components are subjected to subsequent unit treatment; in the nanofiltration unit, under the conditions that the ceramic nanofiltration membrane operating pressure is 1.2 MPa, the distillation component temperature is 25 DEG C, and the pH value is adjusted to 4.0, the water production rate is 65%, the distillation components are subjected to nanofiltration unit treatment, the nanofiltration unit water production COD concentration is controlled to be 72 mg / L, the nanofiltration concentrated water COD concentration is 712 mg / L, and the nanofiltration unit water production enters the raw water tank of the reverse osmosis membrane, and the concentrated water enters the biochemical system wastewater front liquid tank.

[0077] (2) Under the operating conditions that the reverse osmosis unit operating pressure is 2.5 MPa and the water production rate is 80%, the nanofiltration unit water production is treated, the obtained reverse osmosis water production conductivity is 8 mu S / cm, and the concentrated water side COD concentration is 240 mg / L, which enters the biochemical system wastewater front liquid tank.

[0078] (3) The concentrated water produced through the ceramic nanofiltration membrane and the reverse osmosis unit is mixed and collected in the biochemical system front liquid tank, and then enters the combined biochemical system of anaerobic + aerobic + secondary sedimentation tank for treatment, the operation temperature is 30 DEG C, the concentrated water stays in the anaerobic reaction tank for 4.5 h, and stays in the aerobic reaction tank for 4.5 h, so that the COD of the effluent after the biochemical system treatment is less than 65 mg / L, and the distillation components treated by the biochemical system are subjected to multi-medium filter, disc filter device and ultrafiltration unit treatment to obtain ultrafiltration water production, which returns to the front liquid water tank of the nanofiltration unit for repeated treatment and recycling; the ultrafiltration concentrated water returns to the biochemical system.

[0079] (4) Further comprising a water quality monitoring automatic adjusting system for detecting and adjusting the operating pressure of the nanofiltration unit, the reverse osmosis device and the ultrafiltration device: when the COD concentration of the nanofiltration water production, the filtration water production or the reverse osmosis water production rises, the frequency of the booster pump is reduced, and the operating pressure of the membrane is reduced; when the operating pressure of the nanofiltration unit, the ultrafiltration device or the reverse osmosis device rises, the nanofiltration unit, the ultrafiltration device and the reverse osmosis device enter the shutdown state, the membrane cleaning unit is started, the device with the rising operating pressure is cleaned, after the cleaning is completed, the nanofiltration unit, the ultrafiltration device and the reverse osmosis device start to operate.

[0080] Embodiment 2

[0081] The embodiment provides a cobalt system raffinate treatment and resource utilization method, which specifically comprises the following steps:

[0082] (1) The high-salt raffinate is continuously evaporated and concentrated in an MVR evaporator to crystallize and obtain a byproduct salt, the mother liquor produced is dried, the distillation components produced in the evaporation process are subjected to subsequent unit treatment, in the nanofiltration unit, under the conditions that the operating pressure of the ceramic nanofiltration membrane is 1.0 MPa, the temperature of the distillation components is 30°C, and the pH value is adjusted to 4.0, the water production rate is 60%, the distillation components are treated in the nanofiltration unit, the COD concentration of the water produced by the nanofiltration unit is controlled to be 68 mg / L, and the COD concentration of the concentrated water of the nanofiltration unit is 682 mg / L, the water produced by the nanofiltration unit enters the raw water tank of the reverse osmosis unit, and the concentrated water enters the wastewater front tank of the biochemical system.

[0083] (2) Under the operating conditions that the operating pressure of the reverse osmosis unit is 2.8 MPa and the water production rate is 85%, the water produced by the nanofiltration unit is treated to obtain reverse osmosis water with an electrical conductivity of 7 μS / cm, which is reused, and the COD concentration of the concentrated water on the side is 250 mg / L, which enters the wastewater front tank of the biochemical system.

[0084] (3) The concentrated water produced by the ceramic nanofiltration membrane and the reverse osmosis unit is mixed and collected in the biochemical system front tank, and then enters the combined biochemical system of anaerobic + aerobic + secondary sedimentation tank for treatment, the operating temperature is 35°C, the residence time of the concentrated water in the anaerobic reaction tank is 4 h, and the residence time in the aerobic reaction tank is 4 h, so that the COD of the effluent treated by the biochemical system is less than 65 mg / L, and the distillation components treated by the biochemical system pass through the multi-medium filter, the disc filter device and the ultrafiltration unit to obtain ultrafiltration water, which returns to the front tank of the nanofiltration unit for repeated treatment and recycling; the ultrafiltration concentrated water returns to the biochemical system.

[0085] (4) It also includes a water quality monitoring and automatic adjusting system for detecting and adjusting the operating pressure of the nanofiltration unit, the reverse osmosis device and the ultrafiltration device: when the COD concentration of the nanofiltration water, the filtration water or the reverse osmosis water increases, the frequency of the booster pump is reduced to reduce the operating pressure of the membrane; when the operating pressure of the nanofiltration unit, the ultrafiltration device or the reverse osmosis device rises, the nanofiltration unit, the ultrafiltration device and the reverse osmosis device enter the shutdown state, the membrane cleaning unit is started, the device with rising operating pressure is cleaned, after cleaning, the nanofiltration unit, the ultrafiltration device and the reverse osmosis device are started.

[0086] Example 3:

[0087] The embodiment provides a cobalt system raffinate treatment and resource utilization method, which specifically comprises the following steps:

[0088] (1) The high-salt raffinate is evaporated and concentrated in the MVR evaporator, the mother liquor produced is dried, and the distillation components are subjected to subsequent unit treatment. In the nanofiltration unit, under the conditions of a nanofiltration unit operating pressure of 0.9 MPa, a distillation component temperature of 30°C, and a pH value adjusted to 4.0, the water production rate is 50%, the distillation component is treated in the nanofiltration unit, the COD concentration of the nanofiltration unit water production is controlled to be 63 mg / L, the COD concentration of the nanofiltration concentrated water is 642 mg / L, and the nanofiltration unit water production enters the raw water tank of the reverse osmosis unit, and the concentrated water enters the biochemical system wastewater front tank.

[0089] (2) Under the operating conditions of a reverse osmosis unit operating pressure of 3.0 MPa and a water production rate of 90%, the nanofiltration unit water production is treated to obtain a reverse osmosis water production with an electrical conductivity of 9 μS / cm for reuse, and the concentrated water side has a COD concentration of 272 mg / L, which enters the biochemical system wastewater front tank.

[0090] (3) The concentrated water produced by the ceramic nanofiltration membrane and the reverse osmosis unit is mixed and collected in the biochemical system front tank, and then enters the combined biochemical system of anaerobic + aerobic + secondary sedimentation tank for treatment, with an operating temperature of 40°C, a residence time of the concentrated water in the anaerobic reaction tank of 3.5 h, and a residence time in the aerobic reaction tank of 3.5 h, so that the COD of the effluent after biochemical system treatment is less than 65 mg / L. The distillation components treated by the biochemical system are subjected to multi-medium filter, disc filter device and ultrafiltration unit to obtain ultrafiltration water production, which returns to the front tank of the nanofiltration unit for repeated treatment and recycling; the ultrafiltration concentrated water returns to the biochemical system.

[0091] (4) It also includes a water quality monitoring and automatic adjustment system for detecting and adjusting the operating pressure of the nanofiltration unit, the reverse osmosis device, and the ultrafiltration device: when the COD concentration of the nanofiltration water production, the filtration water production, or the reverse osmosis water production increases, the frequency of the booster pump is reduced, and the operating pressure of the membrane is reduced; when the operating pressure of the nanofiltration unit, the ultrafiltration device, or the reverse osmosis device increases, the nanofiltration unit, the ultrafiltration device, and the reverse osmosis device enter a shutdown state, the membrane cleaning unit is started, the device with increased operating pressure is cleaned, and after cleaning, the nanofiltration unit, the ultrafiltration device, and the reverse osmosis device are started.

[0092] Comparative Example 1

[0093] The comparative example provides a cobalt system raffinate treatment and resource utilization method, which is mainly different from example 1 in that in step (1), the high-salt raffinate does not undergo evaporation concentration and is directly introduced into a nanofiltration unit for treatment, the operating pressure is 1.0 MPa, the water production rate is 40%, the nanofiltration concentrated water with high salt content after concentration and the nanofiltration water with low salt content are obtained, the nanofiltration concentrated water is evaporated and concentrated to obtain distillation components, and the nanofiltration water is introduced into a reverse osmosis unit for step (2), under the conditions of an operating pressure of 2.0 MPa and a water production rate of 60%, the reverse osmosis water is used as reclaimed water for reuse, and the reverse osmosis concentrated water is introduced into a biochemical unit for step (3), and when the effluent COD is less than 200 mg / L, the effluent is filtered by a filtration unit and then introduced into a nanofiltration unit.

[0094] Comparative example 2

[0095] The comparative example provides a cobalt system raffinate treatment and resource utilization method, which is mainly different from example 1 in that the distillation components are first introduced into a reverse osmosis unit and then into an evaporation unit. In step (1), the high-salt raffinate does not undergo evaporation concentration and is directly introduced into a reverse osmosis unit for treatment, the operating pressure is 2.0 MPa, the water production rate is 60%, the reverse osmosis concentrated water with high salt content after concentration and the reverse osmosis water with low salt content are obtained, the reverse osmosis concentrated water is evaporated and concentrated to obtain distillation components, and the reverse osmosis water is introduced into a nanofiltration unit for step (2), the SS (suspended solids) and COD in the water are separated, the operating pressure is 2.0 MPa, the water production rate is 75%, the effluent COD is controlled to be less than 200 mg / L, the SS is less than 1 mg / L, part of the nanofiltration water is used as condensate water for reuse, the nanofiltration concentrated water is introduced into a biochemical unit for step (3), and the effluent is filtered by a filtration unit and then introduced into a nanofiltration unit.

[0096] The salt content, conductivity, turbidity, COD and pure water recovery rate of the water sample prepared by the method of each of the above examples and comparative examples are shown in Table 1.

[0097] Table 1

[0098]

[0099] Note: The pure water recovery rate is the ratio of the volume of pure water obtained to the volume of high-salt raffinate.

[0100] In the application, the high-salt raffinate produced by the extraction process in the cobalt system enters the evaporator to obtain by-product salt, and the high-COD concentration distillation component produced is subjected to nanofiltration by a ceramic nanofiltration membrane, so that the COD concentration of the nanofiltration product water is reduced to 50 mg / L-75 mg / L, and then the nanofiltration product water is subjected to reverse osmosis by a reverse osmosis membrane to produce reverse osmosis product water for reuse; the concentrated water produced by the ceramic nanofiltration membrane and the reverse osmosis is subjected to treatment in a biochemical system to reduce the COD concentration, and then the suspended solids are treated by filtration, and the filtration product water is returned to the nanofiltration unit, and the filtration concentrated water is returned to the biochemical unit, and the distillation component is repeatedly treated to increase the water resource recovery rate, so as to finally achieve the purpose of zero discharge of distilled water and resource recycling.

[0101] In the application, the steps can realize the treatment of the salt in the raffinate, the removal of the COD in the distillation component produced after evaporation, and the resource utilization of the distillation component. Compared with the methods of coagulation sedimentation, Fenton oxidation, and membrane concentration of salt, the application not only reduces the consumption of related auxiliary materials, but also reduces the cleaning frequency of the membrane unit, increases the continuous and stable operation time of the membrane device, and prolongs the service life of the membrane. The application realizes the treatment of the salt in the raffinate, the deep removal of the COD in the distillation component, and the resource utilization of the distillation component by "evaporation crystallization + nanofiltration separation + biochemical synergy", and has technical feasibility and economy. The application not only realizes the treatment of the high-salt raffinate, but also achieves the green and environmentally friendly purpose of zero discharge of wastewater treatment.

[0102] The above only describes the preferred embodiments of the application and is not used to limit the application. The application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A method for treating and utilizing cobalt system raffinate, characterized in that, Includes the following steps: Evaporation: The cobalt system raffinate to be treated is fed into an evaporator for evaporation to obtain mother liquor and distilled components; Nanofiltration allows the distilled components to pass through a nanofiltration unit to obtain nanofiltration permeate with low COD concentration and nanofiltration concentrate with high COD concentration. In addition to COD, a biological system is used to treat and filter the nanofiltration concentrate to obtain filtered concentrate and filtered permeate. The biological system includes an anaerobic reaction tank, an aerobic reaction tank and a secondary sedimentation tank connected in sequence. Reverse osmosis is used to pass the nanofiltration permeate through a reverse osmosis unit to obtain reverse osmosis permeate and reverse osmosis concentrate.

2. The method for treating and utilizing the raffinate of a cobalt system according to claim 1, characterized in that, In the evaporation step, the cobalt system raffinate to be treated passes through a forced circulation evaporator and a vacuum flash crystallizer in succession, and the vacuum flash crystallizer is connected to a vacuum pump. And / or, the evaporation temperature is 105℃-115℃; And / or, it also includes drying the mother liquor.

3. The method for treating and utilizing the raffinate of the cobalt system according to claim 1, characterized in that, In the nanofiltration step, the operating pressure of the nanofiltration unit is 0.9MPa-1.2MPa, the water production rate is 50%-65%, the temperature of the distillation component is 25℃-30℃, and the pH value of the distillation component is adjusted to 3.8-4.

2. And / or, the nanofiltration unit includes a ceramic nanofiltration membrane.

4. The method for treating and utilizing the raffinate of the cobalt system according to claim 1, characterized in that, The COD content of the nanofiltration permeate is 50 mg / L-75 mg / L; And / or, the COD content of the nanofiltration concentrate is 600 mg / L-900 mg / L.

5. The method for treating and utilizing the raffinate of the cobalt system according to claim 1, characterized in that, The temperature for the biochemical treatment is 25℃-40℃; And / or, in the biochemical treatment step, the nanofiltration concentrate has a residence time of 3.5h-4.5h in the anaerobic reactor and a residence time of 3.5h-4.5h in the aerobic reactor; And / or, the COD of the water discharged through the biological treatment system is less than 65 mg / L.

6. The method for treating and utilizing the raffinate of a cobalt system according to claim 1, characterized in that, The filtration process involves sequentially passing the biochemically treated nanofiltration concentrate through a multi-media filter, a disc filter, and an ultrafiltration unit. And / or, the filtered concentrate is returned to the biological system for biological treatment, and the filtered permeate is returned to the nanofiltration step for nanofiltration.

7. The method for treating and utilizing the raffinate of a cobalt system according to claim 1, characterized in that, In the reverse osmosis step, the operating pressure of the reverse osmosis unit is 2.3MPa-3.0MPa, and the water production rate is 75%-90%. And / or, the reverse osmosis concentrate is returned to the nanofiltration step and subjected to nanofiltration treatment together with the distillation components.

8. The method for treating and utilizing the raffinate of a cobalt system according to claim 1, characterized in that, The conductivity of the reverse osmosis permeate is <10 μS / cm, and the turbidity is ≤0.1 NTU. And / or, the COD concentration of the reverse osmosis concentrate is 240 mg / L-280 mg / L.

9. The method for treating and utilizing the raffinate of a cobalt system according to claim 1, characterized in that, The concentrations of magnesium ions in the cobalt system raffinate are 2000 mg / L-3000 mg / L, sulfate ions are 15000 mg / L-25000 mg / L, chloride ions are 450 mg / L-550 mg / L, ammonium ions are 20000 mg / L-30000 mg / L, and oil content is 15 mg / L-20 mg / L.

10. The method for treating and utilizing the raffinate of a cobalt system according to claim 6, characterized in that, It also includes detecting and adjusting the operating pressure of the nanofiltration unit, reverse osmosis device, and ultrafiltration device: when the COD concentration of nanofiltration permeate, filtration permeate, or reverse osmosis permeate increases, the frequency of the booster pump is reduced, and the operating pressure of the membrane is reduced. And / or, when the operating pressure of the nanofiltration unit, ultrafiltration unit, or reverse osmosis unit increases, the nanofiltration unit, ultrafiltration unit, and reverse osmosis unit enter a shutdown state, the membrane cleaning unit is started to clean the unit with increased operating pressure, and after cleaning is completed, the nanofiltration unit, ultrafiltration unit, and reverse osmosis unit start operation.

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