Method for efficiently preparing chromium tanning agent with high quality from vitamin K3 chromium-containing waste liquid

Abstract

The invention discloses a method for efficiently preparing a chrome tanning agent with high quality from vitamin K3 chromium-containing waste liquid, and relates to the technical field of industrial waste liquid resource utilization. The method comprises the following steps: reacting sodium dichromate, concentrated sulfuric acid and the vitamin K3 chromium-containing waste liquid, completely oxidizing organic matters which are difficult to oxidize in the waste liquid by adopting a high-concentration hexavalent chromium oxidizing agent, reducing the content of the organic matters in the product, and increasing the content of chromium. The conventional pure glucose reduction is changed into oxidation of glucose to form a micromolecular reducing agent alcohol aldehyde acid, so that the organic matters in the waste liquid can be thoroughly eliminated. And key parameters are controlled through DCS control pipeline reaction, so that insoluble substances are reduced to the maximum extent, and the chromium content in the sugar reduction chromium powder is maximized and organic matters are minimized. The main quality index of the prepared chrome tanning agent exceeds the original national standard.

Description

Technical Field

[0001] The invention relates to the technical field of resource utilization of industrial waste liquid, and in particular to a method for efficiently and high-quality preparing a chrome tanning agent from vitamin K3 chromium-containing waste liquid. Background Art

[0002] Chrome tanning is the most mature technology in the leather industry, with the most reliable product quality and the widest suitability. Chrome tanning agents are widely used in leather production, and the demand for chrome tanning agents is large. So far, among various tanning agents, chrome tanning agents are the tanning agents with the best comprehensive performance. Chrome tanned leather has excellent properties such as good moisture and heat stability, softness, fullness, high strength, storage resistance, and water washing resistance. After more than 100 years of application, chrome tanning has many superior properties that cannot be replaced by other inorganic or organic tanning methods. The main component of chrome tanning powder is the inorganic acid salt of Cr(III). The current manufacturing method at home and abroad is to reduce Cr(VI) in dichromate to Cr(III) salt with a reducing solution in an aqueous solution and under the catalysis of sulfuric acid acidic conditions, and spray dry to form chromium sulfate powder. In view of the difference in reducing solutions, it is divided into inorganic reducing chrome tanning agents and organic reducing chrome tanning agents. Among them, organic reducing chrome tanning agents use appropriate organic matter (such as glucose) to reduce dichromate, chromic anhydride, etc. into trivalent chromium tanning liquid.

[0003] Vitamin K3 is a general term for 2-methyl-1,4-naphthoquinone and its adducts. It is an important vitamin variety and has a wide range of uses in medicine, feed additives and food. At present, in the production process of vitamin K3, the intermediate 2-methyl-1,4-naphthoquinone is usually obtained by oxidation of the raw material 2-methylnaphthalene with sodium chromium as an oxidant. Vitamin K3 produced using hexavalent chromium salt as an oxidant. This type of waste is in liquid form, mainly composed of hexavalent chromium, trivalent chromium, sulfuric acid and trace organic residues. Relevant experiments show (CN 109880944 B) that the hexavalent chromium content in vitamin K3 waste liquid is 10-20g / L, the total chromium content is 85-95g / L, the total acid content is 4.5-6.0mol / L, and 2-methylnaphthalene and vitamin K3 are both 0.7-1.3g / L. It is not only a highly toxic waste that cannot be discharged, but also an important heavy metal resource. Recycling its useful components can improve economic and environmental benefits.

[0004] Patent document CN 101289227 B provides a method for recovering chromium from waste liquid produced from vitamin K3. It records that using waste liquid produced from vitamin K3 as raw material to produce chrome tanning agent can not only effectively recycle chromium resources, but also reduce environmental pollution, which is of great significance for high-value conversion of waste. The waste liquid of vitamin K3 is distilled to dryness at 97-100°C, and the obtained chromium-containing waste residue is calcined at 400-950°C to recover high-purity (98.8-99.9%) Cr2O3. However, this method requires calcination equipment, high energy consumption, large investment, and is difficult to promote.

[0005] Patent document CN 104386752 B provides a method for preparing basic chromium sulfate using the residual night obtained from the production of menadione, which records that the vitamin K3 waste liquid is concentrated, uniformly mixed with industrial sugar in a certain molar ratio, and reacted in a pressure reactor at 100-300°C and 0-4MPa for 0.5-4h. Then, a small amount of hexavalent chromium that has not reacted in the feed liquid is reduced to trivalent chromium with a reducing liquid, and the basicity is adjusted with an alkaline liquid, and spray-dried to prepare a basic chromium sulfate product. This method requires a pressure reactor, which has problems such as high difficulty in operation and low safety. In addition, the use of alkaline liquid to adjust the chrome tanning agent has a great impact on the chrome tanning agent product and the quality of tanned leather, and it is difficult to apply it on a large scale industrially.

[0006] Patent document CN 101348425 B provides a method for co-producing menadione with chrome tanning agent, which records the balance of reactant ratio according to the components of vitamin K3 waste liquid: taking the mother liquor (oxidation residual liquid) for preparing vitamin K3 menadione, according to the stoichiometric (see chemical formula): 4Na2Cr2O7+12H2SO4+C6H 12 O6→8Cr(OH)SO4+4Na2SO4+3CO2+14H2O

[0007] The Cr(VI) content is measured and converted into sodium chromium sulfate (NaCr2O7), the residual sulfuric acid is supplemented with sodium chromium sulfate, and the glucose reducing solution is slowly added after the temperature is raised. The resulting solution is spray-dried to obtain basic chromium sulfate (CN 101348425 B). The method has low investment, fast effect and low cost.

[0008] However, in the reaction between dichromate and glucose, the components of glucose after oxidation and decomposition are complex, and glucose is oxidized and degraded into small molecular oxides such as formic acid, formaldehyde, and oxalic acid. Different reaction conditions will generate different ratios of small molecular oxidation products, which will cause instability in the purity, alkalinity, hydrolysis, water solubility, size of the complex and pH of the solution of the chrome tanning agent.

[0009] Therefore, how to effectively treat the chromium-containing waste liquid of vitamin K3 while significantly improving the quality accuracy and stability of chrome tanning agent products and making them suitable for large-scale production is a technical problem that needs to be solved.

[0010] In view of this, the present invention is proposed. Summary of the invention

[0011] The object of the present invention is to provide a method for preparing a chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3.

[0012] The present invention is achieved in that:

[0013] In a first aspect, the present invention provides a method for efficiently and high-quality preparing a chrome tanning agent from chromium-containing waste liquid of vitamin K3, comprising:

[0014] 100 parts of dichromate, 100 parts of vitamin K3 chromium-containing waste liquid and 60-70 parts of 98% concentrated sulfuric acid are stirred and dissolved and heated to 80-100° C. to obtain an oxidizing solution;

[0015] Oxidizing 15 to 20 parts of glucose, 30 to 40 parts of hydrogen peroxide solution and 1 to 2 parts of 98% concentrated sulfuric acid at 80 to 100° C. to obtain a reducing solution;

[0016] The oxidizing liquid and the reducing liquid are respectively injected into a pipeline reactor and mixed to carry out a contact reaction. The temperature and pressure are monitored by a DCS control system. Finally, the hexavalent chromium in the reaction liquid is detected online. The reaction is carried out until the hexavalent chromium in the product is completely reduced to trivalent chromium and the organic carbon is minimized. The reaction solution is then spray-dried to obtain a powdered chrome tanning agent.

[0017] In an optional embodiment, the method of mixing the oxidizing liquid and the reducing liquid in the pipeline reactor includes: contacting and mixing the oxidizing liquid and the reducing liquid, and the addition time of the oxidizing liquid and the reducing liquid is consistent, both of which are 1.5-2.0 hours.

[0018] In an optional embodiment, the mass ratio of the oxidizing liquid to the reducing liquid is 1.2-1.5:1.

[0019] In an optional embodiment, during the contact reaction process, a DCS control system is used to control the temperature of the reaction system to 80-100° C. and the pressure to normal pressure.

[0020] In an optional embodiment, when the hexavalent chromium in the product is not completely reduced to trivalent chromium, sodium bisulfite is added to continue the reduction until the hexavalent chromium in the product is completely reduced to trivalent chromium.

[0021] In an optional embodiment, the mass percentage concentration of the hydrogen peroxide solution is 20-30%.

[0022] In an optional embodiment, the hexavalent chromium content in the chromium-containing waste liquid of vitamin K3 is 10-15 g / L, the total acid content is 4.5-5.0 mol / L, and the 2-methylnaphthalene and vitamin K3 are both 0.7-1.3 g / L.

[0023] In an optional embodiment, the spray drying conditions are: an inlet temperature of 160-180°C, an outlet temperature of 110-120°C, and a tower top wind pressure of 280-340Pa.

[0024] In an optional embodiment, the dichromate includes any one of sodium dichromate or potassium dichromate.

[0025] In an optional embodiment, before spray drying the reaction solution, the reaction solution is further cooled to 45-50° C. and stirred for 3-4 hours.

[0026] The present invention has the following beneficial effects:

[0027] The method for preparing a chrome tanning agent from a chromium-containing waste liquid of vitamin K3 provided by the present invention is efficient and high-quality. By reacting glucose, hydrogen peroxide solution and sulfuric acid in advance, glucose can be pre-oxidized into aldol acid whose main component is smaller molecules (glucose is completely oxidized into aldol acid), which is conducive to the subsequent complete reduction of hexavalent chromium. It also avoids the situation that the purity, alkalinity, hydrolysis, water solubility, size of the complex and pH instability of the chrome tanning agent and its solution are easily caused by the direct reaction of glucose with dichromate. In addition, the oxidizing liquid is sodium dichromate, concentrated sulfuric acid and K3 waste liquid containing organic matter are first reacted, and a high-concentration hexavalent chromium oxidant is used to completely oxidize the organic matter in the waste liquid that is more difficult to oxidize, reduce the organic matter content of the product, and increase the chromium content. Finally, a pipeline reactor is used to make the redox solution contact evenly, and a DCS control system monitors key parameters such as temperature and pressure to prevent overheating of the reaction and carbonization of organic matter. The main quality indicators of the prepared chrome tanning agent exceed the original national standard (GB / T 24331-2009). DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0029] The present invention provides a method for preparing a chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3, which comprises:

[0030] S1. Stir and dissolve 100 parts of dichromate, 100 parts of chromium-containing waste liquid of vitamin K3 and 60-70 parts of concentrated sulfuric acid with a content of 98% and raise the temperature to 80-100° C. to obtain an oxidizing solution.

[0031] Dichromates include but are not limited to any one of sodium dichromate or potassium dichromate. The hexavalent chromium content in the chromium-containing waste liquid of vitamin K3 is 10-15 g / L, the total acid content is 4.5-5.0 mol / L, and the 2-methylnaphthalene and vitamin K3 are both 0.7-1.3 g / L. In the present invention, dichromate, vitamin K3 chromium-containing waste liquid and concentrated sulfuric acid (H2SO4) are stirred and dissolved, and a high-concentration hexavalent chromium oxidant is used to completely oxidize the organic matter that is difficult to oxidize in the chromium-containing waste liquid of vitamin K3, thereby reducing the organic matter content of the product and increasing the chromium content.

[0032] S2. Oxidize 15 to 20 parts of glucose, 30 to 40 parts of hydrogen peroxide solution and 1 to 2 parts of 98% concentrated sulfuric acid at 80 to 100° C. to obtain a reducing solution; the mass percentage concentration of the hydrogen peroxide solution is 20-30%.

[0033] In the present invention, by reacting glucose, hydrogen peroxide solution and sulfuric acid in advance, glucose can be pre-oxidized into aldol acid whose main component is smaller molecules (in step S2 of the present invention, glucose is completely oxidized into aldol acid), thereby improving the complete oxidation effect, ensuring that hexavalent chromium is completely reduced with minimal organic matter, and increasing the chromium content.

[0034] When glucose directly reacts with dichromate, the components after glucose oxidation and decomposition are complex, in which glucose is oxidized and degraded into small molecular oxides such as formic acid, formaldehyde, and oxalic acid. Different reaction conditions will lead to different ratios of small molecular oxidation products, causing instability in the purity, alkalinity, hydrolysis, water solubility, size of the complex and pH of the solution of the chrome tanning agent.

[0035] To this end, the present invention utilizes glucose, hydrogen peroxide solution and sulfuric acid to react in advance, so that glucose can be pre-oxidized into aldol acids whose main components are smaller molecules. Specifically, the reaction products of glucose pre-oxidized into aldol acids with smaller molecules are relatively complex, and it is difficult to clearly define the exact reaction equation; but it is easy to understand that glucose can be oxidized by hydrogen peroxide solution to obtain small molecule aldol acids, thereby achieving the effect of completely reducing hexavalent chromium. As for which small molecule aldol acids these are and what proportion these three are, the present invention does not make a specific discussion. As long as glucose, hydrogen peroxide solution and sulfuric acid are pre-reacted according to the above-mentioned proportion, the effect of the present invention can be achieved.

[0036] In the present invention, glucose, hydrogen peroxide solution and sulfuric acid are used for pre-reaction, which is beneficial to the subsequent complete reduction of hexavalent chromium and avoids the situation that the purity, alkalinity, hydrolysis, water solubility, complex size and pH instability of the chrome tanning agent and its solution are easily caused by the direct reaction of glucose with dichromate.

[0037] S3. Inject the oxidizing liquid and reducing liquid into the pipeline reactor respectively to mix and carry out contact reaction. Use the DCS control system to monitor the temperature and pressure. Finally, conduct online detection of the hexavalent chromium in the reaction liquid. React until the hexavalent chromium in the product is completely reduced to trivalent chromium and the organic carbon is minimized. Then, spray dry the reaction solution to obtain a powdered chrome tanning agent.

[0038] Specifically, the oxidizing liquid and the reducing liquid are contacted and mixed, and the addition time of the oxidizing liquid and the reducing liquid is consistent, both of which are 1.5-2.0 hours. The mass ratio of the oxidizing liquid to the reducing liquid is 1.2-1.5:1. During the contact reaction process, the temperature of the reaction system is controlled to be 80-100°C and the pressure is normal pressure by using a DCS control system.

[0039] In the present invention, the pipeline reactor is used to make the oxidizing liquid and the reducing liquid fully contact each other. At the same time, the DCS control system controls and monitors the reaction process throughout the process, effectively avoiding the occurrence of overheating of the reaction, carbonization of organic matter, etc.

[0040] When the hexavalent chromium in the product is not completely reduced to trivalent chromium, sodium bisulfite is added to continue the reduction until the hexavalent chromium in the product is completely reduced to trivalent chromium, so as to minimize the organic carbon. Before the reaction solution is spray-dried, the reaction solution is cooled to 45-50°C and stirred for 3-4 hours. By continuing to stir the reaction after cooling, the overall reaction can be made more complete, and then spray drying is performed. The conditions for spray drying are an inlet temperature of 160-180°C, an outlet temperature of 110-120°C, and a tower top wind pressure of 280-340Pa. The reaction solution can be turned into powder by spray drying.

[0041] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0042] Example 1

[0043] This embodiment provides a method for preparing a chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3, which comprises:

[0044] S1, 100 parts of dichromate, 100 parts of chromium-containing waste liquid of vitamin K3 and 60 parts of concentrated sulfuric acid with a content of 98%, stirring and dissolving, heating to 95° C., to obtain an oxidizing solution;

[0045] The hexavalent chromium content in the chromium-containing waste liquid of vitamin K3 is 12g / L, the total acid content is 4.8mol / L, and the 2-methylnaphthalene and vitamin K3 are both 1g / L.

[0046] S2. 15 parts of glucose, 30 parts of 25% hydrogen peroxide solution and 1.5 parts of sulfuric acid are oxidized at 90° C. to form a reducing solution.

[0047] S3. Inject the oxidizing liquid and reducing liquid into the pipeline reactor for contact mixing. The addition time of the oxidizing liquid and reducing liquid is 1.5h. The mass ratio of the oxidizing liquid to the reducing liquid is 1.3:1. During the contact reaction, the temperature of the reaction system is controlled to 80℃ and normal pressure by the DCS control system. At the same time, the hexavalent chromium in the reaction liquid is detected online. If necessary, sodium bisulfite is added to completely reduce the hexavalent chromium in the product to trivalent chromium and minimize organic carbon; the reaction solution is cooled to 45℃ and stirred for 4 hours, and pumped into the spray dryer. According to the inlet temperature of 170℃, the outlet temperature of 115℃, and the wind pressure of 310Pa at the top of the tower, it is sprayed into a powdered chrome tanning agent, and the packaging and storage are completed.

[0048] Example 2

[0049] This embodiment provides a method for preparing a chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3, which comprises:

[0050] S1, 100 parts of dichromate, 100 parts of chromium-containing waste liquid of vitamin K3 and 70 parts of concentrated sulfuric acid with a content of 98%, stirring and dissolving, heating to 90° C., to obtain an oxidizing solution;

[0051] The hexavalent chromium content in the chromium-containing waste liquid of vitamin K3 is 10g / L, the total acid content is 4.5mol / L, and the 2-methylnaphthalene and vitamin K3 content are both 0.7g / L.

[0052] S2. 18 parts of glucose, 35 parts of 20% hydrogen peroxide solution and 1 part of sulfuric acid are oxidized at 98° C. to form a reducing solution.

[0053] S3. Inject the oxidizing liquid and reducing liquid into the pipeline reactor respectively for contact mixing. The addition time of the oxidizing liquid and reducing liquid is 2.0h. The mass ratio of the oxidizing liquid to the reducing liquid is 1.5:1. During the contact reaction, the temperature of the reaction system is controlled to 90°C and normal pressure by the DCS control system. At the same time, the hexavalent chromium in the reaction liquid is detected online. If necessary, sodium bisulfite is added to completely reduce the hexavalent chromium in the product to trivalent chromium and minimize organic carbon; the reaction solution is cooled to 50°C and stirred for 3 hours, and pumped into the spray dryer. According to the inlet temperature of 160°C, the outlet temperature of 110°C, and the wind pressure of 280Pa at the top of the tower, it is sprayed into a powdered chrome tanning agent, and the packaging and storage are completed.

[0054] Example 3

[0055] This embodiment provides a method for preparing a chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3, which comprises:

[0056] S1, 100 parts of dichromate, 100 parts of chromium-containing waste liquid of vitamin K3 and 65 parts of concentrated sulfuric acid with a content of 98%, stirring and dissolving, heating to 80° C., to obtain an oxidizing solution;

[0057] The hexavalent chromium content in the chromium-containing waste liquid of vitamin K3 is 15g / L, the total acid content is 5.0mol / L, and the 2-methylnaphthalene and vitamin K3 content are both 1.3g / L.

[0058] S2. 20 parts of glucose, 40 parts of 30% hydrogen peroxide solution and 2 parts of sulfuric acid are oxidized at 80° C. to form a reducing solution.

[0059] S3. Inject the oxidizing liquid and reducing liquid into the pipeline reactor respectively for contact mixing. The addition time of the oxidizing liquid and reducing liquid is 1.8h. The mass ratio of the oxidizing liquid to the reducing liquid is 1.2:1. During the contact reaction, the temperature of the reaction system is controlled to 100℃ and normal pressure by the DCS control system. At the same time, the hexavalent chromium in the reaction liquid is detected online. If necessary, sodium bisulfite is added to completely reduce the hexavalent chromium in the product to trivalent chromium and minimize organic carbon; the reaction solution is cooled to 48℃ and stirred for 3.5 hours, and pumped into the spray dryer. According to the inlet temperature of 180℃, the outlet temperature of 120℃, and the wind pressure of 340Pa at the top of the tower, it is sprayed into a powdered chrome tanning agent, and the packaging and storage are completed.

[0060] Comparative Example 1

[0061] The present comparative example provides a method for preparing a chrome tanning agent by utilizing chromium-containing waste liquid of vitamin K3, which comprises: charging 100 parts of chromium-containing waste liquid of vitamin K3 into a reactor equipped with a temperature control and stirring device, adding 100 parts of sodium dichromate, and then adding 60 parts of 98% concentrated sulfuric acid, and stirring until the dichromate is completely dissolved; adding 15 parts of glucose at 95°C to completely reduce the hexavalent chromium to trivalent chromium; continuing stirring at the reaction temperature for 1 hour, aging for 24 hours, and spray drying to obtain the chrome tanning agent.

[0062] Comparative Example 2

[0063] The present comparative example provides a method for preparing a chrome tanning agent by utilizing chromium-containing waste liquid of vitamin K3, which comprises: firstly adding 100 parts of chromium-containing waste liquid of vitamin K3 into a normal temperature dissolver, and then sequentially adding 100 parts of sodium dichromate and 15 parts of glucose into the normal temperature dissolver, stirring to completely dissolve them to obtain a mixed solution; placing the mixed solution in a high-pressure reactor, reacting for 8 hours at a temperature of 160°C and a pressure of 1.8MPa, to obtain a chrome tanning liquid.

[0064] Comparative Example 3

[0065] This comparative example is substantially the same as Example 1, except that in this comparative example, the glucose in the reducing solution of Example 1 is replaced by sulfur dioxide.

[0066] Comparative Example 4

[0067] This comparative example is basically the same as Example 1, except that this comparative example is not carried out in a pipeline reactor. The specific operation is as follows:

[0068] S1, 100 parts of dichromate, 100 parts of chromium-containing waste liquid of vitamin K3 and 60 parts of concentrated sulfuric acid with a content of 98%, stirring and dissolving, heating to 95° C., to obtain an oxidizing solution;

[0069] The hexavalent chromium content in the chromium-containing waste liquid of vitamin K3 is 12g / L, the total acid content is 4.8mol / L, and the 2-methylnaphthalene and vitamin K3 are both 1g / L.

[0070] S2. 15 parts of glucose, 30 parts of 25% hydrogen peroxide solution and 1.5 parts of sulfuric acid are oxidized at 90° C. to form a reducing solution.

[0071] S3. Add all the oxidizing liquid and reducing liquid into the container for contact mixing, control the temperature of the reaction system to 80°C and normal pressure, and at the same time, conduct online detection of hexavalent chromium in the reaction liquid. If necessary, add sodium bisulfite to completely reduce the hexavalent chromium in the product to trivalent chromium and minimize organic carbon; cool the reaction solution to 45°C and stir for 4 hours, pump it into a spray dryer, and spray it into a powdered chrome tanning agent at an inlet temperature of 170°C, an outlet temperature of 115°C, and a tower top wind pressure of 310Pa, and complete packaging and warehousing.

[0072] Experimental example

[0073] The chrome tanning agents prepared in the above examples and comparative examples were tested for Cr2O3 content, alkalinity and insoluble particles according to the national standard "Powdered Chrome Tanning Agents for Leather Making" (GB / T24331-2009). The test results are shown in Table 1.

[0074] Table 1. Statistical table of product measurement results for different examples

[0075] sample <![CDATA[Cr2O3 / %]]> Measured alkalinity / % Insoluble particles / % Example 1 24.72 32.93 0.1 Example 2 25.1 33.06 0.1 Example 3 24.98 32.96 0.1 Comparative Example 1 24.3 31.1 0.5 Comparative Example 2 24.1 31.5 0.3 Comparative Example 3 26.4 33.6 0.5 Comparative Example 4 22.7 30.1 0.3

[0076] It can be seen from the above table that the powdered chrome tanning agents prepared in Examples 1-3 of the present invention not only have higher chromium content and alkalinity, but also have fewer insoluble particles.

[0077] In Comparative Example 1, glucose is directly added to a mixed solution of chromium-containing waste liquid of vitamin K3, sodium dichromate and concentrated sulfuric acid. At this time, the components of glucose after oxidation and decomposition are complex, resulting in a product with a chromium content and alkalinity significantly lower than those in Example 1, and a significantly higher insoluble particulate matter than those in Example 1.

[0078] In Comparative Example 2, glucose is directly reacted with chromium-containing waste liquid of vitamin K3 and sodium dichromate. At this time, the components after oxidative decomposition of glucose are complex. Even under high pressure conditions, the chromium content and alkalinity of the product are significantly lower than those in Example 1, and the insoluble particulate matter is significantly higher than that in Example 1.

[0079] In Comparative Example 3, sulfur dioxide is used as a reducing agent. Although it can increase the chromium content and alkalinity, the content of insoluble particles is also significantly higher than that of other embodiments and comparative examples. This is because sulfur dioxide easily reacts with substances in the reaction system to produce insoluble particles.

[0080] In Comparative Example 4, the reaction was not carried out in a pipeline reactor. At this time, the reaction process was difficult to control, and the contact uniformity between the oxidant and the reductant was poor, resulting in the product chromium content and alkalinity being significantly lower than those in Example 1, and the insoluble particulate matter being significantly higher than those in Example 1.

[0081] In addition, the chrome tanning agent obtained by the present invention is compared with typical products at home and abroad. Please refer to Table 2 for the comparison results.

[0082] Table 2. Main quality index control table of basic chromium sulfate tanning agent products

[0083]

[0084] The main quality indicators of the new HLS-C chromium powder produced by the technology of this invention exceed the original national standard (GB / T24331-2009). Compared with the original national standard, it is mainly reflected in:

[0085] 1) Effective matter (Cr2O3): lower than imported products and 0.5% higher than the national standard product content.

[0086] 2) Reliability: Except for the same Cr(VI), basicity (B), water-insoluble matter and pH value are all improved.

[0087] 3) Safety: The new formaldehyde standard exceeds that of foreign products.

[0088] In summary, the present invention provides a method for preparing a chrome tanning agent from a vitamin K3 chromium-containing waste liquid with high efficiency and quality. By reacting glucose, hydrogen peroxide solution and sulfuric acid in advance, glucose can be pre-oxidized into aldol acid (glucose is completely oxidized to aldol acid) whose main component is smaller molecules, which is conducive to the subsequent complete reduction of hexavalent chromium. And it avoids the situation that the purity, alkalinity, hydrolysis, water solubility, complex size and pH instability of the chrome tanning agent caused by the direct reaction of glucose with dichromate are easily caused. In addition, the oxidizing liquid is sodium dichromate, concentrated sulfuric acid and vitamin K3 chromium-containing waste liquid containing organic matter are first reacted, and a high-concentration hexavalent chromium oxidant is used to completely oxidize the organic matter that is more difficult to oxidize in the waste liquid, reduce the organic matter content of the product, and increase the chromium content. Finally, a pipeline reactor is used to make the redox solution contact evenly, and the DCS control system monitors key parameters such as temperature and pressure, which can prevent overheating of the reaction and carbonization of organic matter, and can effectively reduce the hexavalent chromium in the system, and the product has less organic matter content and high chromium content.

[0089] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3, characterized in that: It includes: 100 parts of dichromate, 100 parts of chromium-containing waste liquid of vitamin K3 and 60-70 parts of concentrated sulfuric acid with a content of 98% are stirred and dissolved and heated to 80-100° C. to obtain an oxidizing solution; Oxidizing 15 to 20 parts of glucose, 30 to 40 parts of hydrogen peroxide solution and 1 to 2 parts of 98% concentrated sulfuric acid at 80 to 100° C. to obtain a reducing solution; The oxidizing liquid and the reducing liquid are respectively injected into a pipeline reactor for mixing and contact reaction, and the temperature and pressure are monitored by a DCS control system. Finally, the hexavalent chromium in the reaction liquid is detected online. The reaction is carried out until the hexavalent chromium in the product is completely reduced to trivalent chromium and the organic carbon is minimized. Subsequently, the reaction liquid is spray-dried to obtain a powdered chrome tanning agent.

2. The method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: The method for mixing the oxidizing liquid and the reducing liquid in the pipeline reactor comprises: contacting and mixing the oxidizing liquid and the reducing liquid, and the adding time of the oxidizing liquid and the reducing liquid is consistent, both of which are 1.5-2.0 hours.

3. The method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: The mass ratio of the oxidizing liquid to the reducing liquid is 1.2-1.5:

1.

4. The method for preparing chrome tanning agent with high efficiency and high quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: During the contact reaction, the temperature of the reaction system is controlled to be 80-100° C. and the pressure to be normal pressure by using a DCS control system.

5. The method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: When the hexavalent chromium in the product is not completely reduced to trivalent chromium, sodium bisulfite is added to continue the reduction until the hexavalent chromium in the product is completely reduced to trivalent chromium.

6. The method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: The mass percentage concentration of the hydrogen peroxide solution is 20-30%.

7. The method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: The hexavalent chromium content in the chromium-containing waste liquid of vitamin K3 is 10-15 g / L, the total acid content is 4.5-5.0 mol / L, and the 2-methylnaphthalene and vitamin K3 content are both 0.7-1.3 g / L.

8. The method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: The spray drying conditions are as follows: an inlet temperature of 160-180° C., an outlet temperature of 110-120° C., and a tower top wind pressure of 280-340 Pa.

9. The method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: The dichromate includes any one of sodium dichromate or potassium dichromate.

10. The method for preparing chrome tanning agent with high efficiency and quality from chromium-containing waste liquid of vitamin K3 according to claim 1, characterized in that: Before the reaction solution is spray-dried, the reaction solution is cooled to 45-50° C. and stirred for 3-4 hours.

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