A method for simultaneous reuse of dyed brine and softened and regenerated brine

Abstract

The present invention provides a method for simultaneously reusing dyeing brine and softening regeneration brine, comprising: (1) mixing dyeing brine and softening regeneration brine to obtain a mixed solution, uniformly mixing after adding alkali to the mixed solution, and obtaining a mixed solution containing precipitation; (2) rapidly separating the precipitation and brine in the mixed solution containing precipitation; (3) aerating after adding acid solution to the clear liquid obtained after separation of step (2) to adjust the pH value to 3‑4, and after aeration, adding alkali to adjust the pH value to 6‑9 to obtain recovered brine. The method provided by the present invention can realize the simultaneous reuse of the salt in dyeing brine and softening regeneration brine, and relative to the existing conventional reuse salt process used in the art, the method provided by the present invention also has the advantages of treatment agent, such as small amount of flocculant, polyacrylamide and soda ash, low running cost and simple operation.

Description

Technical Field

[0001] The invention relates to a method for simultaneously reusing dyeing brine and softening regeneration brine, belonging to the technical field of environmental protection and resource recovery. Background Art

[0002] The reactive dyeing process requires large amounts of salt and soda ash, which are typically discharged into sewage treatment plants along with wastewater, increasing the complexity of wastewater treatment and the burden of wastewater reuse. Currently, existing processes for reusing this brine include solvent extraction, membrane filtration, advanced oxidation, and coagulation and sedimentation. However, all of these processes require the addition of large amounts of acid to adjust the pH and remove the soda ash from the brine.

[0003] Currently, many printing and dyeing factories use softening resins to soften water. During their use, a large amount of regenerated brine is generated. This wastewater has high salt concentrations, especially high calcium and magnesium concentrations. Some factories directly discharge this wastewater into sewage treatment plants, while some factories use the double alkali method to reuse it. Among them, the double alkali method generally uses sodium hydroxide or calcium hydroxide to adjust the pH value of the wastewater to remove magnesium salts, and uses sodium carbonate to precipitate calcium salts. After treatment with the double alkali method, the hardness of the regenerated brine can be reduced to below 150 mg / L. It can be seen that the double alkali method requires the addition of large amounts of sodium carbonate and sodium hydroxide, and has high operating costs.

[0004] Therefore, providing a novel method for simultaneously reusing dyeing brine and softening regeneration brine has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] In order to solve the above-mentioned shortcomings and deficiencies, the object of the present invention is to provide a method for simultaneously reusing dyed brine and softened regenerated brine.

[0006] In order to achieve the above object, the present invention provides a method for simultaneously reusing dyed brine and softened regenerated brine, wherein the method for simultaneously reusing dyed brine and softened regenerated brine comprises:

[0007] (1) mixing dyeing brine and softened regenerated brine to obtain a mixed solution, adding alkali to the mixed solution and mixing uniformly to obtain a mixed solution containing a precipitate;

[0008] (2) Rapidly separating the precipitate and the brine from the mixed solution containing the precipitate;

[0009] (3) Acid is added to the clear liquid obtained after separation in step (2) to adjust the pH value to 3-4, and then aeration is performed to blow off the carbon dioxide formed by the carbonate ions. After the aeration is completed, alkali is added to adjust the pH value to 6-9 to obtain recovered brine.

[0010] As a specific embodiment of the above method of the present invention, the volume ratio of the dyeing brine to the softened regenerated brine is 2:1-1:2.

[0011] As a specific embodiment of the above method of the present invention, in step (1), alkali is added to the mixed solution to adjust the pH value to 11.5-12.5.

[0012] As a specific embodiment of the above method of the present invention, in step (1), the base includes sodium hydroxide, calcium hydroxide or potassium hydroxide.

[0013] As a specific embodiment of the above method of the present invention, in step (1), the uniform mixing can be achieved by rapid stirring.

[0014] As a specific embodiment of the above method of the present invention, wherein, in step (2), the rapid separation includes precipitation, mechanical filtration, membrane filtration or centrifugation, etc., wherein precipitation, mechanical filtration, membrane filtration or centrifugation, etc. are all conventional rapid separation methods used in the art.

[0015] As a specific embodiment of the above method of the present invention, in step (3), the acid solution includes sulfuric acid or hydrochloric acid.

[0016] As a specific embodiment of the above method of the present invention, in step (3), the aeration time is 0.5-2 hours, preferably 1 hour.

[0017] As a specific embodiment of the above method of the present invention, in step (3), the base includes sodium hydroxide, calcium hydroxide or potassium hydroxide.

[0018] As a specific embodiment of the above method of the present invention, when the salt in the dyeing brine is sodium chloride, the method further includes directly recycling the recovered brine into the dyeing process and / or the softening resin regeneration process.

[0019] As a specific embodiment of the above-described method of the present invention, when the salt in the dyeing brine is sodium sulfate, the method further includes first using a NF membrane to separate the recovered brine into produced water and concentrated water, then reusing the produced water to the softening resin regeneration process, and reusing the concentrated water to the dyeing process.

[0020] The NF membrane is a conventional device, and the salt separation operation performed using the NF membrane is also a conventional technical means in the art, and those skilled in the art can perform the operation as needed.

[0021] The method provided by the present invention can realize the simultaneous recycling of salt in dyeing brine and softening regenerated brine. At the same time, compared with the existing conventional salt recycling process used in the field, the method provided by the present invention also has the advantages of less use of treatment agents such as flocculants, polyacrylamide and soda ash, low operating costs and simple operation. DETAILED DESCRIPTION

[0022] It should be noted that the term "comprise" and any variations thereof in the description and claims of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, products or apparatus.

[0023] The "range" disclosed in the present invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e., any lower limit can be combined with any upper limit to form a range. For example, a range of 60-120 and 80-110 is listed for a particular parameter, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values listed are 1 and 2, and the maximum range values listed are 3, 4, and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0024] In the present invention, unless otherwise specified, the numerical range "ab" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed in this invention, and "0-5" is merely an abbreviation for these numerical combinations.

[0025] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0026] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0027] In the present invention, unless otherwise specified, the term "two" used in this specification means "at least two".

[0028] In the present invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method comprising steps (a) and (b) indicates that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method further comprising step (c) indicates that step (c) may be added to the method in any order, for example, the method may comprise steps (a), (b) and (c), or may comprise steps (a), (c) and (b), or may comprise steps (c), (a) and (b), etc.

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the attached table and examples. The following embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0030] Example 1

[0031] This embodiment provides a method for simultaneously reusing dyed brine and softened regenerated brine, wherein the method for simultaneously reusing dyed brine and softened regenerated brine includes:

[0032] (a) collecting dyeing brine and placing it into a dyeing brine collection tank, wherein the dyeing brine has a pH of 11.5, a chroma of 2560 times (calculated by dilution multiple method), a sodium chloride concentration of 83 g / L, and a soda ash concentration of 21 g / L; collecting softened backwash brine, i.e., softened regenerated brine, into a softened backwash brine collection tank, wherein the sodium chloride concentration in the softened backwash brine is 57 g / L and the total hardness (calcium chloride and magnesium chloride) is 12400 mg / L;

[0033] (b) mixing the dyed brine and the softened regenerated brine in a volume ratio of 1:1 to obtain a mixed solution, wherein the mixed solution has a pH of 11.1, a hardness of 6200 mg / L, a chromaticity of 1280 times (calculated by a dilution multiple method), and a sodium chloride concentration of 70 g / L;

[0034] (c) adding 1.1 g / L sodium hydroxide to the mixed solution to adjust the pH to 12.0, and stirring at a speed of 200 r / min for 5 min to uniformly stir, thereby causing a large amount of precipitate (calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, etc.) to appear in the mixed solution to obtain a mixed solution containing a precipitate, and then quickly separating the precipitate and brine in the mixed solution containing the precipitate by a precipitation method;

[0035] The supernatant obtained by separation was taken and its chroma was measured. The chroma was measured to be 8 times (calculated by dilution multiple method), and the removal rate was 99.4%. The calcium carbonate hardness was 85 mg / L, and the removal rate was 98.6%.

[0036] (d) adding 1.5 g / L of hydrochloric acid to the supernatant obtained after separation in step (c) to adjust the pH to 3.8 to remove residual carbonate ions, aerating the mixture for 1 hour, and then adding 0.1 g / L of sodium hydroxide to adjust the pH to 8.0 to obtain a recovered brine having an alkalinity of 186 mg / L.

[0037] Since the salt in the dyeing brine used in this embodiment is sodium chloride, the recovered brine can be directly reused in the dyeing process and / or the softening resin regeneration process.

[0038] Comparative Example 1

[0039] This comparative example treats the dyeing brine separately to reuse the salt therein, which comprises the following steps:

[0040] The dyeing brine was collected and placed in a dyeing brine collection tank, wherein the pH value of the dyeing brine was 11.5, the chroma was 2560 times (calculated by the dilution multiple method), the sodium chloride concentration was 83 g / L, and the soda ash concentration was 21 g / L. 9 g / L of flocculant (ferrous chloride) was added to the dyeing brine collection tank, and the mixture was stirred at 200 r / min for 5 minutes. 5 mg / L of polyacrylamide was then added and stirred for 30 minutes. The mixture was then precipitated and separated. The supernatant was measured to have a chroma of 8 times, and a removal rate of 99.7%.

[0041] Then, 1.6 g / L of hydrochloric acid was added to the dyeing brine collection pool to adjust the pH value to 3.8 and then aerated for 1 hour. Then, 0.1 g / L of sodium hydroxide was added to adjust the pH value to 8.0 to obtain recycled brine. The alkalinity of the recycled brine was 168 mg / L.

[0042] Comparative Example 2

[0043] This comparative example separately treats the softened backwash brine to reuse the salt therein, which includes the following steps:

[0044] Collecting softened backwash brine, i.e., softened regenerated brine, into a softened backwash brine collection tank, wherein the sodium chloride concentration in the softened backwash brine is 57 g / L and the total hardness (calcium chloride and magnesium chloride) is 12400 mg / L, adding 10 g / L of sodium carbonate and 2 g / L of sodium hydroxide to the softened backwash brine collection tank, adjusting the pH value to 12.0, and stirring at a speed of 200 r / min for 30 min, followed by precipitation separation;

[0045] The supernatant obtained after separation was taken and 1.5 g / L of hydrochloric acid was added thereto to adjust the pH value to 4.0. The mixture was aerated for 1 hour, and then 0.1 g / L of sodium hydroxide was added to adjust the pH value to 7.5 to obtain recovered brine. At this time, the alkalinity of the recovered brine was 205 mg / L, the hardness was 96 mg / L, and the removal rate was 99.2%.

[0046] Among them, in Example 1, dyeing brine and softened regeneration brine are comprehensively treated, Comparative Example 1 treats dyeing brine alone, and Comparative Example 2 treats softened backwash brine alone. The dosage of the reagents in Example 1 and Comparative Examples 1-2 is shown in Table 1 below.

[0047] Table 1

[0048]

[0049] As can be seen from Table 1 above, the comprehensive treatment of dyeing brine and softened regenerated brine in Example 1 of the present invention can achieve the simultaneous reuse of salt in the dyeing brine and the softened regenerated brine. Compared with the separate treatment of dyeing brine in Comparative Example 1 and the separate treatment of softened backwash brine in Comparative Example 2, the comprehensive treatment of dyeing brine and softened regenerated brine in Example 1 of the present invention does not require additional addition of flocculants, polyacrylamide and soda ash, and has many advantages such as low treatment agent usage, low operating cost and simple operation.

[0050] Example 2

[0051] This embodiment provides a method for simultaneously reusing dyed brine and softened regenerated brine, wherein the method for simultaneously reusing dyed brine and softened regenerated brine includes:

[0052] (a) collecting dyeing brine into a dyeing brine collection tank, wherein the dyeing brine has a pH of 11.4, a chroma of 1280 times (calculated by dilution multiple method), a sodium sulfate concentration of 60 g / L, and a soda ash concentration of 15 g / L; collecting softened backwash brine, i.e., softened regenerated brine, into a softened backwash brine collection tank, wherein the sodium chloride concentration in the softened backwash brine is 48 g / L and the total hardness (calcium chloride and magnesium chloride) is 17400 mg / L;

[0053] (b) mixing the dyed brine and the softened regenerated brine in a volume ratio of 1:1 to obtain a mixed solution, wherein the mixed solution has a pH of 11.1, a hardness of 8700 mg / L, a chromaticity of 640 times (calculated by a dilution multiple method), a sodium sulfate concentration of 30 g / L, and a sodium chloride concentration of 24 g / L;

[0054] (c) adding 1.3 g / L sodium hydroxide to the mixed solution to adjust the pH to 12.0, and stirring at a speed of 200 r / min for 5 minutes to uniformly stir, at which time a large amount of precipitate (calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, etc.) appears in the mixed solution to obtain a mixed solution containing the precipitate, and then using a tubular membrane for rapid separation to obtain the precipitate and the supernatant;

[0055] (d) adding 1.4 g / L of hydrochloric acid to the supernatant obtained after separation in step (c) to adjust the pH to 3.8 to remove remaining carbonate ions, aerating the mixture for 1 hour, and then adding 0.1 g / L of sodium hydroxide to adjust the pH to 8.0 to obtain a recovered brine having an alkalinity of 186 mg / L, a chromaticity of 8 times (calculated by dilution multiple method), a removal efficiency of 98.8%, and a calcium carbonate hardness of 94 mg / L, a removal efficiency of 98.9%;

[0056] Since the salt in the dyeing brine used in this embodiment is sodium sulfate, the method further includes first using a NF membrane to separate the recovered brine into produced water and concentrated water. The produced water is a sodium chloride solution with a concentration of 60 g / L, which can be directly reused in the softening resin regeneration process. The concentrated water contains 100 g / L sodium sulfate and 10 g / L sodium chloride, and can be reused in the dyeing process after adjusting the concentration.

[0057] Comparative Example 3

[0058] This comparative example treats the dyeing brine separately to reuse the salt therein, which comprises the following steps:

[0059] The dyed brine was collected and placed in a dyed brine collection tank, wherein the pH value of the dyed brine was 11.4, the chroma was 1280 times (calculated by the dilution multiple method), the sodium sulfate concentration was 60 g / L, and the soda ash concentration was 15 g / L. 7 g / L of flocculant (ferrous sulfate heptahydrate) was added to the dyed brine collection tank, and the mixture was stirred at a speed of 200 r / min for 5 minutes. 5 mg / L of polyacrylamide was then added and stirred for 30 minutes. The mixture was then precipitated and separated. The chroma of the supernatant was measured to be 8 times (calculated by the dilution multiple method), and the removal rate was 99.4%;

[0060] Then add 1.3g / L of hydrochloric acid to the dyeing brine collection pool to adjust the pH value to 3.8, then aerate for 1h, and then add 0.1g / L of sodium hydroxide to adjust the pH value to 8.0. At this time, the alkalinity of the recovered brine is 146mg / L. After further concentration through the NF membrane, a sodium sulfate solution with a concentration of 100g / L can be obtained, which is reused in the dyeing process.

[0061] Comparative Example 4

[0062] This comparative example separately treats the softened backwash brine to reuse the salt therein, which includes the following steps:

[0063] Collecting softened backwash brine, i.e., softened regenerated brine, into a softened backwash brine collection tank, wherein the sodium chloride concentration in the softened backwash brine is 48 g / L and the total hardness (calcium chloride and magnesium chloride) is 17400 mg / L; adding 15 g / L of sodium carbonate and 2.5 g / L of sodium hydroxide to the softened backwash brine collection tank, adjusting the pH value to 12.0, and stirring at a speed of 200 r / min for 30 minutes, and then separating by a tubular membrane;

[0064] 2 g / L of hydrochloric acid was added to the separated produced water to adjust the pH value to 4.0, followed by aeration for 1 hour, and 0.1 g / L of sodium hydroxide was continued to be added to adjust the pH value to 7.5. At this time, the alkalinity of the recycled brine obtained was 188 mg / L, the hardness was 135 mg / L, and the removal rate was 99.2%, which could be reused in the softening regeneration process.

[0065] Among them, Example 2 comprehensively treats dyeing brine and softened regeneration brine, Comparative Example 3 treats dyeing brine alone, and Comparative Example 4 treats softened backwash brine alone. The dosages of the reagents in Example 2 and Comparative Examples 3-4 are shown in Table 2 below.

[0066] Table 2

[0067]

[0068] As can be seen from Table 2 above, the comprehensive treatment of dyeing brine and softened regenerated brine in Example 2 of the present invention can achieve the simultaneous reuse of salt in the dyeing brine and the softened regenerated brine. Compared with the separate treatment of dyeing brine in Comparative Example 3 and the separate treatment of softened backwash brine in Comparative Example 4, the comprehensive treatment of dyeing brine and softened regenerated brine in Example 2 of the present invention does not require additional addition of flocculants, polyacrylamide and soda ash, and has many advantages such as low treatment agent usage, low operating cost and simple operation.

[0069] In summary, the method provided by the embodiment of the present invention can realize the simultaneous recycling of salt in dyed brine and softened regenerated brine. At the same time, compared with the existing conventional salt recycling process used in the art, the method provided by the embodiment of the present invention also has the advantages of small amount of treatment agents such as flocculants, polyacrylamide and soda ash, low operating cost and simple operation.

[0070] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, substitutions of equivalent components, or equivalent changes and modifications made within the scope of patent protection, should still fall within the scope of this patent. Furthermore, the technical features of this invention may be freely combined with one another, with other technical inventions, and with other technical inventions.

Claims

1. A method for simultaneously reusing dyeing brine and softening regenerated brine, characterized in that: The method for simultaneously reusing dyed brine and softened regenerated brine comprises: (a) collecting dyeing brine and placing it into a dyeing brine collection tank, wherein the dyeing brine has a pH of 11.5, a chromaticity of 2560 times as measured by a dilution multiple method, a sodium chloride concentration of 83 g / L, and a soda ash concentration of 21 g / L; collecting softened backwash brine, i.e., softened regenerated brine, into a softened backwash brine collection tank, wherein the softened backwash brine has a sodium chloride concentration of 57 g / L and a total hardness of 12400 mg / L as calculated by calcium chloride and magnesium chloride; (b) mixing the dyed brine and the softened regenerated brine in a volume ratio of 1:1 to obtain a mixed solution, wherein the mixed solution has a pH of 11.1, a hardness of 6200 mg / L, a chromaticity of 1280 times as measured by a dilution multiple method, and a sodium chloride concentration of 70 g / L; (c) adding 1.1 g / L sodium hydroxide to the mixed solution to adjust the pH to 12.0, and stirring at a speed of 200 r / min for 5 min to uniformly stir, thereby generating a large amount of precipitate in the mixed solution, wherein the precipitate includes calcium carbonate, magnesium carbonate, calcium hydroxide, and magnesium hydroxide, to obtain a mixed solution containing the precipitate, and then rapidly separating the precipitate and the brine in the mixed solution containing the precipitate by a precipitation method; The supernatant obtained by separation was taken and its chroma was measured. The chroma measured by the dilution multiple method was 8 times, and the removal rate was 99.4%. The calcium carbonate hardness was 85 mg / L, and the removal rate was 98.6%. (d) adding 1.5 g / L of hydrochloric acid to the supernatant obtained after separation in step (c) to adjust the pH to 3.8 to remove residual carbonate ions, aerating for 1 hour, and then adding 0.1 g / L of sodium hydroxide to adjust the pH to 8.0 to obtain a recovered brine having an alkalinity of 186 mg / L; Reuse the recovered brine directly in the dyeing process and / or softening resin regeneration process; or; (a) collecting dyeing brine into a dyeing brine collection tank, wherein the dyeing brine has a pH of 11.4, a chromaticity of 1280 times as measured by the dilution multiple method, a sodium sulfate concentration of 60 g / L, and a soda ash concentration of 15 g / L; collecting softened backwash brine, i.e., softened regenerated brine, into a softened backwash brine collection tank, wherein the sodium chloride concentration in the softened backwash brine is 48 g / L, and the total hardness as calculated as calcium chloride and magnesium chloride is 17400 mg / L; (b) mixing the dyed brine and the softened regenerated brine in a volume ratio of 1:1 to obtain a mixed solution, wherein the mixed solution has a pH of 11.1, a hardness of 8700 mg / L, a color of 640 times calculated by a dilution multiple method, a sodium sulfate concentration of 30 g / L, and a sodium chloride concentration of 24 g / L; (c) adding 1.3 g / L sodium hydroxide to the mixed solution to adjust the pH to 12.0, and stirring at a speed of 200 r / min for 5 minutes to uniformly stir, at which time a large amount of precipitate appears in the mixed solution, the precipitate including calcium carbonate, magnesium carbonate, calcium hydroxide, and magnesium hydroxide, to obtain a mixed solution containing the precipitate, and then using a tubular membrane for rapid separation to obtain the precipitate and the supernatant; (d) adding 1.4 g / L of hydrochloric acid to the supernatant obtained after separation in step (c) to adjust the pH to 3.8 to remove remaining carbonate ions, aerating for 1 hour, and then adding 0.1 g / L of sodium hydroxide to adjust the pH to 8.0 to obtain a recovered brine. The recovered brine has an alkalinity of 186 mg / L, a color of 8 times as measured by the dilution multiple method, a removal efficiency of 98.8%, and a calcium carbonate hardness of 94 mg / L, a removal efficiency of 98.9%; First, the NF membrane is used to separate the recovered brine into product water and concentrated water. The product water is a sodium chloride solution with a concentration of 60g / L, which can be directly reused in the softening resin regeneration process. The concentrated water contains 100g / L sodium sulfate and 10g / L sodium chloride, and can be reused in the dyeing process after adjusting the concentration.

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