Calcium saponification wastewater recycling process

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a calcium saponification wastewater recycling process which comprises the following steps: pretreating calcium saponification low-salt wastewater, removing fixed insoluble substances and floating oil in the wastewater, and pretreating the wastewater; neutralizing and debugging the pretreated wastewater by adopting a hydrochloric acid solution, and carrying out biological treatment to obtain secondary wastewater; performing deep treatment on the secondary wastewater to obtain a calcium chloride solution and precipitate of impurities such as iron and aluminum, and purifying the calcium chloride solution to obtain a high-purity calcium chloride solution; the low-concentration calcium chloride solution is treated on the basis of reverse osmosis and electrodialysis methods, the industrial-grade calcium chloride solution and the purified water are obtained, the purified water can be recycled, zero emission of the wastewater is achieved, great economic benefits are achieved, and the problem that the environment is polluted due to the fact that existing saponification wastewater is directly discharged with wastewater obtained after biological treatment is adopted is solved.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to a recycling process of calcium saponification wastewater. Background Art

[0002] The calcium soap wastewater produced by calcium saponification of extractants in the existing rare earth smelting process has the characteristics of large water volume, low salt content (mainly calcium chloride), and high COD. Traditional saponification wastewater treatment generally adopts a treatment method with biological method as the core, which mainly removes organic matter in the wastewater. The calcium chloride content of the treated wastewater is 2g / L-4g / L, which is low-salt wastewater. Due to the large wastewater output and high COD, the environmental pressure is relatively large. With the increasingly stringent environmental protection requirements, the discharge of calcium saponification low-salt wastewater is restricted, so the treatment of calcium saponification low-salt wastewater is of great significance and necessity. Summary of the invention

[0003] The purpose of the present invention is to provide a calcium saponification wastewater recycling process, aiming to solve the problem that the existing saponification wastewater is treated by biological treatment, has a high COD, and is directly discharged to pollute the environment.

[0004] To achieve the above object, the present invention provides a process for recycling calcium saponification wastewater, comprising the following steps:

[0005] Pre-treat the calcium saponification low-salt wastewater to remove fixed insoluble matter and floating oil in the wastewater and pre-treat the wastewater;

[0006] The pre-treated wastewater is neutralized and debugged with a hydrochloric acid solution, and then subjected to a biological treatment to obtain secondary wastewater;

[0007] The secondary wastewater is subjected to deep treatment to obtain a calcium chloride solution and iron and aluminum impurity precipitation to purify the calcium chloride solution to obtain a high-purity calcium chloride solution;

[0008] The low-concentration calcium chloride solution is treated based on reverse osmosis and electrodialysis to obtain a high-concentration industrial-grade calcium chloride solution and pure water.

[0009] The specific method of pre-treating the calcium saponification low-salt wastewater to remove the fixed insoluble matter and floating oil in the wastewater is as follows:

[0010] The calcium saponification low-salt wastewater is introduced into a sedimentation tank for static treatment to obtain static wastewater;

[0011] The stationary wastewater is introduced into a multi-media filter for filtration to remove fixed insoluble matter and floating oil in the wastewater to obtain pretreated wastewater.

[0012] Wherein, the inner filter material of the multi-media filter is one or more of quartz sand, anthracite, ceramsite, activated carbon, and the particle size is 1-10 mm.

[0013] The specific method of using hydrochloric acid solution to neutralize and debug the pre-treated wastewater and perform biological treatment to obtain secondary wastewater is as follows:

[0014] Adding hydrochloric acid solution to the pretreated wastewater and stirring to mix, neutralizing and adjusting the pH value to obtain neutral wastewater;

[0015] The neutral wastewater is subjected to biological treatment and aeration treatment to decompose organic matter and obtain secondary wastewater.

[0016] Wherein, the concentration of the hydrochloric acid solution is 30-31%, and the biological treatment includes biodegradation and biooxidation.

[0017] The specific method of deep treating the secondary wastewater to obtain the calcium chloride solution and precipitate the iron and aluminum impurities to purify the calcium chloride solution to obtain a high-purity calcium chloride solution is as follows:

[0018] Performing activated carbon filtration treatment on the secondary wastewater to remove biochemical suspended matter;

[0019] Removing organic chlorides from the secondary wastewater after filtration based on electrochemical oxidation technology;

[0020] Adding 400-mesh calcium carbonate powder to the secondary wastewater for aeration, neutralization and precipitation, controlling the pH to 8, and obtaining a calcium chloride solution and impurity precipitation such as iron and aluminum;

[0021] The impurity precipitation such as iron and aluminum is filtered to obtain a high-purity calcium chloride solution. Among them, the electrodialysis method requires an electrodialysis system, and the ion exchange membrane used in the electrodialysis system is a homogeneous membrane or a heterogeneous membrane, and the material is one or more of polyethylene, polyvinyl chloride, polystyrene and polymethyl methacrylate.

[0022] The invention discloses a recycling process for calcium saponification wastewater, which comprises the following steps: pre-treating calcium saponification low-salt wastewater, removing fixed insolubles and floating oil in the wastewater, and pre-treating the wastewater; neutralizing and debugging the pre-treated wastewater with a hydrochloric acid solution, and performing a biochemical treatment to obtain secondary wastewater; performing a deep treatment on the secondary wastewater to obtain a calcium chloride solution and iron and aluminum impurity precipitation, and purifying the calcium chloride solution to obtain a high-purity calcium chloride solution; and treating the low-concentration calcium chloride solution based on a reverse osmosis and electrodialysis method to obtain an industrial-grade calcium chloride solution and pure water. The process realizes effective treatment and resource utilization of calcium saponification low-salt wastewater by comprehensively using technical means such as pre-treatment, neutralization treatment, biochemical treatment, deep treatment, recycling, and the like. This process not only reduces the pollution of wastewater discharge to the environment, but also improves the utilization rate of resources. The high-concentration industrial-grade calcium chloride solution and pure water obtained can be recycled, and the high-concentration industrial-grade calcium chloride solution can be directly sold or further evaporated and concentrated to produce industrial solid calcium chloride for sale. It not only achieves zero discharge of wastewater, but also can achieve huge economic benefits. The water circulation rate of this calcium saponification process and comprehensive wastewater recycling technology can reach more than 93.3%, which is expected to take a new step in green environmental protection and solve the problem that the existing saponification wastewater uses biological treatment of wastewater with high COD and is directly discharged to pollute the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 The present invention provides a flow chart of a calcium saponification wastewater recycling process.

[0025] Figure 2 It is a flow chart of the specific method of pre-treating calcium saponification low-salt wastewater to remove fixed insoluble matter and floating oil in the wastewater.

[0026] Figure 3 The specific flow chart is that the pre-treated wastewater is neutralized and debugged with a hydrochloric acid solution, and then subjected to a biological treatment to obtain secondary wastewater.

[0027] Figure 4 The invention is a flow chart of a specific method for deeply treating secondary wastewater, obtaining calcium chloride solution and precipitating iron and aluminum impurities to purify the calcium chloride solution to obtain a high-purity calcium chloride solution. DETAILED DESCRIPTION

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0029] See also Figures 1 to 4 The present invention provides a calcium saponification wastewater recycling process, comprising the following steps:

[0030] S1 pre-treats the calcium saponification low-salt wastewater to remove fixed insoluble matter and floating oil in the wastewater and pre-treats the wastewater;

[0031] Specific method:

[0032] S11 introduces the calcium saponification low-salt wastewater into a sedimentation tank for static treatment to obtain static wastewater;

[0033] In the embodiment of the present invention, the purpose of standing is to precipitate the solid insoluble matter in the calcium saponification low-salt wastewater.

[0034] S12 introduces the stationary wastewater into a multi-media filter for filtration to remove fixed insoluble matter and floating oil in the wastewater to obtain pretreated wastewater.

[0035] In an embodiment of the present invention, the solid insoluble matter in the saponification wastewater is filtered out, and the filter material in the multi-media filter is one or more of quartz sand, anthracite, ceramsite, and activated carbon, with a particle size of 1-10 mm. The purpose of removing the fixed insoluble matter and floating oil in the wastewater is to create favorable conditions for subsequent treatment steps.

[0036] S2 uses hydrochloric acid solution to neutralize and debug the pretreated wastewater, and performs biological treatment to obtain secondary wastewater;

[0037] Specific method:

[0038] S21 adds hydrochloric acid solution to the pretreated wastewater and stirs and mixes, neutralizes and adjusts the pH value to obtain neutral wastewater;

[0039] In the embodiment of the present invention, the concentration of the hydrochloric acid solution is 30-31%, which reduces the pH value of the pretreated wastewater to neutral or close to neutral, providing suitable environmental conditions for subsequent biochemical treatment.

[0040] S22 performs biological treatment and aeration treatment on the neutral wastewater to decompose organic matter and obtain secondary wastewater.

[0041] In the embodiment of the present invention, the biological treatment includes biodegradation and biooxidation, and in this treatment process, the metabolism of microorganisms is used to decompose organic matter in the wastewater into harmless substances such as carbon dioxide and water.

[0042] S3 performs deep treatment on the secondary wastewater to obtain a calcium chloride solution and iron and aluminum impurity precipitation, and purifies the calcium chloride solution to obtain a high-purity calcium chloride solution;

[0043] Specific method:

[0044] S31 performs activated carbon filtration treatment on the secondary wastewater to remove biogenic suspended solids;

[0045] In the embodiment of the present invention, activated carbon filtration can remove suspended solids, large particles and some oils and fats in the wastewater.

[0046] S32 removes organic matter from the secondary wastewater after filtration based on electrochemical oxidation technology;

[0047] In the embodiment of the present invention, the organic matter includes kerosene, P507 extractant and other difficult-to-degrade organic matter.

[0048] Electrochemical oxidation or electrochemical oxidation combined process can improve the organic matter removal efficiency and reduce energy consumption by optimizing electrode materials and electrolytic cell structure.

[0049] S33: adding 400 mesh calcium carbonate powder to the secondary wastewater for aeration, neutralization and precipitation, and controlling the pH to 8 to obtain a calcium chloride solution and impurity precipitation such as iron and aluminum;

[0050] In the embodiment of the present invention, 400 mesh calcium carbonate powder is added to the secondary wastewater to convert it into impurity precipitation such as iron and aluminum and 0.2-0.4% low concentration calcium chloride (CaCl 2 ) aqueous solution, the chemical reaction principle is:

[0051] 3CaCO 3 +2FeCl 3 +3H 2 O→2Fe(OH)3↓+CaCl 2 +CO 2 ↑ (1)

[0052] 3CaCO 3 +2AlCl 3 +3H 2 O→2Al(OH)3↓+CaCl 2 +CO 2 ↑ (2)

[0053] S34 filters the iron and aluminum impurities and precipitates the calcium chloride solution for purification to obtain a high-purity calcium chloride solution.

[0054] S4 treats the low-concentration calcium chloride solution based on reverse osmosis and electrodialysis to obtain a high-concentration industrial-grade calcium chloride solution and pure water.

[0055] In the embodiment of the present invention, the electrodialysis method requires an electrodialysis system. The ion exchange membrane used in the electrodialysis system is a homogeneous membrane or a heterogeneous membrane, and the material is one or more of polyethylene, polyvinyl chloride, polystyrene, and polymethyl methacrylate; the operating pressure of the reverse osmosis system is 2.0Mpa-6.0Mpa, and the electrodialysis system is specifically a system composed of several electrodialysis membrane stacks in parallel, that is, the water inlet pipes of all electrodialysis membrane stacks are connected to the total water inlet pipe of the electrodialysis system, and all electrodialysis The high-concentration water pipe of the membrane stack is connected to the total high-concentration water pipeline of the electrodialysis system, and the low-concentration water pipes of all electrodialysis membrane stacks are connected to the total low-concentration water pipeline of the electrodialysis system. The ultrafiltration water is used as raw water and enters the total water inlet pipeline of the electrodialysis system through the electrodialysis raw water pump and then enters each electrodialysis membrane stack. After electrodialysis separation, the high-concentration water of each electrodialysis membrane stack enters the total concentrate water pipeline of the electrodialysis system as a high-concentration calcium chloride solution. The low-concentration water of each electrodialysis membrane stack enters the total low-concentration water pipeline of the electrodialysis system and enters the reverse osmosis system.

[0056] Among them, the electrodialysis membrane stack is an existing technology on the market (refer to an electrodialyzer CN201821116829.8). It is composed of anion and cation exchange membranes and separators arranged and pressed in sequence, and a DC electric field is applied to the plates on both sides of the membrane. The total number of membrane stacks required = total membrane area / single membrane stack area = total processing capacity / unit membrane area processing capacity / single membrane stack area is calculated, where the unit membrane area processing capacity is 20-50L / m 2 ·h

[0057] This process achieves effective treatment and resource utilization of calcium saponification low-salt wastewater by comprehensively using pretreatment, neutralization treatment, biochemical treatment, deep treatment and recycling techniques. This process not only reduces the pollution of wastewater discharge to the environment, but also improves the utilization rate of resources. The high-concentration industrial-grade calcium chloride solution obtained can be sold or further prepared into industrial solid calcium chloride, and the pure water can be directly recycled, which not only achieves zero discharge of wastewater, but also achieves huge economic benefits. The water circulation rate of this calcium saponification process and wastewater comprehensive recycling technology can reach more than 93.3%, which is expected to reach a new level in green environmental protection and solve the problem that the existing calcium saponification low-salt wastewater is treated by biological treatment, has high COD, and is directly discharged to pollute the environment.

[0058] In order to better understand the present technical solution, the following embodiments are provided for further explanation:

[0059] Example: Taking the process of purifying calcium chloride as an example to obtain calcium chloride solution and iron and aluminum impurity precipitation

[0060] Step 1: Place a certain amount of saponified wastewater in an aeration neutralization tank, add 400-mesh calcium carbonate powder, and when the aeration pH value reaches above 8, stop the aeration reaction and perform solid-liquid separation.

[0061] Step 2: Take the filtrate after the solid-liquid separation and put it into a non-diaphragm electrolytic cell, the anode of which is a mesh flat plate Ti / PbO 2 Oxide coated electrode, stainless steel material as cathode, the anode and cathode areas are the same, pH value is adjusted to -26 ~ 7, constant current electrolysis is carried out at room temperature, current density is 50mA / cm, sampling is carried out at regular intervals, COD monitoring is carried out, and electrolysis is carried out until COD is less than 10mg / L.

[0062] Step 3: The calcium chloride solution from which organic matter is removed in step 2 is first pre-treated by an activated carbon tank, and then enters an RO treatment device to obtain 15-16% brine and pure water, and the pure water can be directly returned to production for recycling. The 15-16% brine is concentrated by an electrodialyzer, and the concentrated phase calcium chloride concentration reaches more than 20%, which is an industrial calcium chloride solution, which can be sold or further processed into solid industrial calcium chloride; the dilute phase is about 10% brine, which is returned to the electrodialysis cycle for concentration.

[0063] The above disclosure is only a preferred embodiment of the lime saponification wastewater recycling process of the present invention. Of course, it cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A calcium saponification wastewater recycling process, characterized in that: The following steps are involved: Pre-treat the calcium saponification low-salt wastewater to remove fixed insoluble matter and floating oil in the wastewater and pre-treat the wastewater; The pre-treated wastewater is neutralized and debugged with a hydrochloric acid solution, and then subjected to a biological treatment to obtain secondary wastewater; The secondary wastewater is subjected to deep treatment to obtain a calcium chloride solution and iron and aluminum impurity precipitation to purify the calcium chloride solution to obtain a high-purity calcium chloride solution; The low-concentration calcium chloride solution is treated based on reverse osmosis and electrodialysis to obtain a high-concentration industrial-grade calcium chloride solution and pure water.

2. The calcium saponification wastewater recycling process according to claim 1, characterized in that: The specific method of pre-treating the calcium saponification low-salt wastewater to remove the fixed insoluble matter and floating oil in the wastewater is as follows: The calcium saponification low-salt wastewater is introduced into a sedimentation tank for static treatment to obtain static wastewater; The stationary wastewater is introduced into a multi-media filter for filtration to remove fixed insoluble matter and floating oil in the wastewater to obtain pretreated wastewater.

3. The calcium saponification wastewater recycling process as claimed in claim 2, characterized in that: The inner filter material of the multi-media filter is one or more of quartz sand, anthracite, ceramsite, and activated carbon, and the particle size is 1-10 mm.

4. The calcium saponification wastewater recycling process according to claim 1, characterized in that: The specific method of using hydrochloric acid solution to neutralize and debug the pre-treated wastewater and perform biological treatment to obtain secondary wastewater is: Adding hydrochloric acid solution to the pretreated wastewater and stirring to mix, neutralizing and adjusting the pH value to obtain neutral wastewater; The neutral wastewater is subjected to biological treatment and aeration treatment to decompose organic matter and obtain secondary wastewater.

5. The calcium saponification wastewater recycling process as claimed in claim 4, characterized in that: The concentration of the hydrochloric acid solution is 30-31%, and the biological treatment includes biodegradation and biooxidation.

6. The calcium saponification wastewater recycling process according to claim 1, characterized in that: The specific method of deeply treating the secondary wastewater to obtain the calcium chloride solution and the iron and aluminum impurity precipitation, and purifying the calcium chloride solution to obtain the high-purity calcium chloride solution is as follows: Performing activated carbon filtration treatment on the secondary wastewater to remove biochemical suspended matter; Removing organic matter from the secondary wastewater after filtration based on electrochemical oxidation technology; Adding 400-mesh calcium carbonate powder to the secondary wastewater for aeration, neutralization and precipitation, and controlling the pH to 8 to obtain a calcium chloride solution and iron and aluminum impurity precipitates; The iron and aluminum impurity precipitate is filtered to obtain a high-purity calcium chloride solution.

7. The calcium saponification wastewater recycling process according to claim 6, characterized in that: The electrodialysis method requires an electrodialysis system. The ion exchange membrane used in the electrodialysis system is a homogeneous membrane or a heterogeneous membrane, and the material is one or more of polyethylene, polyvinyl chloride, polystyrene and polymethyl methacrylate.

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