A method for centrifugal separation of de-esterified raffinate acid

Abstract

The present application relates to the technical field of extraction separation, and particularly relates to a method for centrifugal separation and deesterification of raffinate acid. The present application discloses a method for centrifugal separation and deesterification of raffinate acid, which comprises introducing a mixed solution containing raffinate acid and an extractant into a centrifugal separator for separation. According to the method, the raffinate acid obtained through centrifugal separation is observed to have no oil film on the surface after being placed for more than 96 hours, while the raffinate acid without separation has an obvious oil film on the surface. Therefore, the mixed solution is separated through centrifugal separation, so that the separation effect is ensured, the production cost is reduced, the product quality is improved, and the environmental pollution is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of extraction separation, and in particular to a method for centrifugal separation and de-esterification of raffinate acid. BACKGROUND

[0002] With the development of chemical industry, phosphoric acid and its derivatives as important chemical raw materials, in agriculture, food, medicine and other fields have a wide range of applications. However, in the production process of phosphoric acid, especially in the purification section of phosphoric acid device, often produce containing trace amount of extractant raffinate acid. These trace amounts of extractant not only affect the purity of phosphate products, but also adversely affect the subsequent nitric acid phosphate fertilizer device, resulting in problems in the concentration process, and thus affecting the quality of the final product. In addition, the trace amount of extractant carried in the process condensate also brings difficulty to the water treatment workshop, increasing the cost of sewage treatment.

[0003] At present, for the removal of trace amount of extractant in raffinate acid, the common practice in the industry is to naturally stand in the mixed acid tank of phosphate device, and realize partial separation by gravity. However, this method is low in efficiency, unstable in separation effect, and difficult to completely remove trace amount of extractant, resulting in difficulty in ensuring product quality. Therefore, it is particularly important to develop a kind of efficient, stable and economical method for centrifugal separation and de-esterification of raffinate acid. SUMMARY

[0004] The present application provides a method for centrifugal separation and de-esterification of raffinate acid, which can reduce production cost, improve product quality and reduce environmental pollution while ensuring separation effect.

[0005] The technical scheme adopted by the present application to solve the technical problems is:

[0006] A method for centrifugal separation and de-esterification of raffinate acid, comprising introducing a mixed liquid containing raffinate acid and extractant into a centrifugal separator for separation.

[0007] In one or more technical solutions, the volume content ratio of extractant to raffinate acid in the mixed liquid is 99:1-80:20.

[0008] In one or more technical solutions, the volume content ratio of extractant to raffinate acid in the mixed liquid is 95:5-90:10.

[0009] In one or more technical solutions, the volume content ratio of extractant to raffinate acid in the mixed liquid is 96:4-98:2.

[0010] In one or more technical solutions, when the separation is carried out in the centrifugal separator, the frequency of stirring is controlled as variable frequency control, and the frequency range of variable frequency control is within 26-46 Hz.

[0011] In one or more of the technical solutions, the centrifugal separator has a rated power of 0.37 kW, a rated voltage of 220 V / 380 V, a rated current of 1.63 / 0.84 A, a rated frequency of 50 Hz, and a rated rotating speed of 2800-6500 r / min.

[0012] In one or more of the technical solutions, the mixed solution is introduced into the centrifugal separator by a pump for continuous centrifugal separation.

[0013] In one or more of the technical solutions, the pump has a pump-in flow rate of 15-1000 kg / h.

[0014] In one or more of the technical solutions, after the mixed solution is introduced into the centrifugal separator for separation, target raffinate acid and target extractant are obtained, the specific gravity of the target raffinate acid is 1.15-1.50 g / mL, and the specific gravity of the target extractant is 0.95-0.985 g / mL.

[0015] In one or more of the technical solutions, the weight content of the extractant in the target raffinate acid is <0.01%, and the weight content of the raffinate acid in the target extractant is <0.01%.

[0016] The application has the following beneficial effects:

[0017] The method described in the application has the best separation effect when the frequency of the stirring frequency conversion during centrifugal separation is controlled in the range of 26-46 Hz, and no entrainment phenomenon is observed by naked eye observation. This shows that the centrifugal separation technology can achieve efficient separation in a short time, and significantly improves the separation efficiency.

[0018] The raffinate acid treated by the centrifugal separation technology is placed for more than 96 hours, and no oil film is observed on the surface by naked eye observation, while the surface of the unseparated raffinate acid has obvious oil film phenomenon. This shows that the centrifugal separation technology can effectively remove trace extractant, improve the purity and quality of the phosphate product, and enhance the market competitiveness of the product.

[0019] The centrifugal separation technology not only improves the separation efficiency, but also reduces the burden on the water treatment system. Test data shows that the extractant after separation can be effectively recovered, reducing environmental pollution and reducing the environmental protection cost of enterprises. BRIEF DESCRIPTION OF DRAWINGS

[0020] The application will be further described below in combination with the drawings and examples.

[0021] Fig. 1 A working schematic diagram of centrifugal separation for the method of raffinate acid centrifugal separation and degreasing described in the application;

[0022] Fig. 2The working schematic diagram of continuous centrifugal separation for the method of centrifugal separation and deesterification of raffinate acid. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not intended to limit the present application.

[0024] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0025] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one" or similar expressions mean any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can mean a, b, c, ab (i.e. a and b), ac, bc, or abc, wherein a, b and c can be single or multiple.

[0026] It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of the processes should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0027] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0028] The weight of the related components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio between each component, therefore, as long as the content of the related components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass mentioned in the specification of the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0029] The terms "first", "second", "third", etc. are used only for the purpose of description, to distinguish between objects, such as substances, from each other, and cannot be understood as indicating or implying relative importance or implying the number of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features.

[0030] Although the current conventional natural standing method is simple, the separation speed is slow, the separation effect is poor, and it cannot meet the requirements of modern industry for high-efficiency separation. Moreover, the presence of trace amounts of extractants in the mixed solution directly affects the purity of the phosphate product, and further affects the market competitiveness of the product; in addition, the trace amounts of extractants entering the water treatment workshop are difficult to effectively treat, which can easily cause environmental pollution and increase the environmental protection pressure and cost of enterprises. In order to solve the above technical problems, the present application provides a method for centrifugal separation and degreasing of raffinate acid as shown in Figs. 1-2 The method for centrifugal separation and degreasing of raffinate acid comprises introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator for single centrifugal separation or continuous centrifugal separation.

[0031] Specifically, the preparation of the mixed solution is as follows: after the extractant is subjected to extraction treatment (standing separation) on the feed liquid containing phosphoric acid, the upper layer obtained is the extraction feed liquid; after the extraction feed liquid is subjected to stripping treatment (standing separation), the lower layer obtained is the stripping solution, and the stripping solution is collected to obtain the mixed solution.

[0032] After the stripping treatment, part of the extractant in the extraction feed liquid is not separated cleanly, causing entrainment into the stripping solution. In large chemical production, the mixed solution obtained by multiple or multi-party collection contains a certain amount of extractant.

[0033] The mixed solution is introduced into a centrifugal separator for single centrifugal separation or continuous centrifugal separation. The centrifugal separator utilizes the centrifugal force generated by high-speed rotation to make liquids of different densities produce different trajectories under the action of centrifugal force, thereby realizing separation. In the present application, the difference in specific gravity (density) of the raffinate acid and the extractant in the mixed solution becomes the basis for centrifugal separation; in combination with the control of the rotation speed and stirring frequency of the centrifugal separator, high-efficiency separation can be realized in a short time.

[0034] In one or more embodiments, the volume content ratio of the extractant and the raffinate acid in the mixed solution is 99.9:0.1-80:20. For example, the volume content ratio of the extractant and the raffinate acid in the mixed solution is any one of 99.9:0.1, 99.8:0.2, 99.7:0.3, 99.6:0.4, 99.5:0.5, 99.4:0.6, 99.3:0.7, 99.2:0.8, 99.1:0.9, 99:1, 98:2, 97:3, 96:4, 95:5, 94:6, 93:7, 92:8, 91:9, 90:10, 89:11, 88:12, 87:13, 86:14, 85:15, 84:16, 83:17, 82:18, 81:19, 80:20.

[0035] Preferably, the volume content ratio of the extractant and the raffinate acid in the mixed solution is 99:1-90:10, and specifically can be any one of 99:1, 98:2, 97:3, 96:4, 95:5, 94:6, 93:7, 92:8, 91:9, 90:10.

[0036] More preferably, the volume content ratio of the extractant and the raffinate acid in the mixed solution is 98:2-95:5, and specifically can be any one of 98:2, 97:3, 96:4, 95:5.

[0037] In one or more embodiments, when the centrifugal separation is performed in the centrifugal separator, the frequency of stirring is controlled to be 26-46 Hz, and / or the frequency of stirring is not fixed.

[0038] Specifically, the frequency of stirring is adjusted within 26-46 Hz. The variable frequency stirring can control the centrifugal force by adjusting the stirring frequency, thereby optimizing the separation effect.

[0039] In one or more embodiments, the rated power of the centrifugal separator is 0.37 kW, the rated voltage is 220 V / 380 V, the rated current is 1.63 / 0.84 A, the rated frequency is 50 Hz, and the rated rotational speed is 2800-6500 r / min.

[0040] Specifically, the rated rotational speed of 2800-6500 r / min can generate sufficient centrifugal force to ensure effective separation of the extractant and the raffinate acid with different specific gravities. If the actual rotational speed is lower than 2800-6500 r / min, the centrifugal force is insufficient, the separation effect is poor, and the separation may not be complete. If the actual rotational speed exceeds 2800-6500 r / min, the centrifugal force may be increased, which can cause excessive wear of the equipment, increase energy consumption, and even damage the equipment.

[0041] In one or more embodiments, the mixed solution is introduced into the centrifugal separator by a pump for continuous centrifugal separation. The pump has a pump flow rate of 15-1000 kg / h.

[0042] Specifically, by pumping the mixed solution, a continuous production process can be achieved, avoiding the problems of low efficiency and discontinuous production caused by intermittent operation.

[0043] Specifically, the flow rate range of 15-1000 kg / h ensures that the mixed solution enters the centrifugal separator at an appropriate rate, so that the centrifugal separator operates in an optimal state, thereby achieving high separation efficiency.

[0044] Too high a flow rate can cause the mixed solution to enter the centrifugal separator too quickly, and the centrifugal separator cannot complete effective separation in a short time, resulting in a decrease in separation efficiency and a large amount of extractant still entrained in the raffinate acid. Too low a flow rate can cause the mixed solution to enter the centrifugal separator too slowly, prolonging the separation process and affecting production efficiency.

[0045] In one or more embodiments, after the mixed solution is introduced into the centrifugal separator for separation, the target raffinate acid and the target extractant are obtained; the specific gravity of the target raffinate acid is 1.15-1.50 g / mL, and the specific gravity of the target extractant is 0.95-0.985 g / mL.

[0046] Specifically, the specific gravities of the target raffinate acid and the target extractant are designed within a certain range, and the density difference between them is utilized to ensure effective separation during the centrifugal separation process. The specific gravity of the target raffinate acid is relatively high (1.15-1.50 g / mL), while the specific gravity of the target extractant is relatively low (0.95-0.985 g / mL), which allows the two substances to quickly separate under the action of centrifugal force, achieving high separation efficiency.

[0047] In one or more embodiments, the weight content of the extractant in the target raffinate acid is <0.01%, and the weight content of the raffinate acid in the target extractant is <0.01%.

[0048] Specifically, the target raffinate acid is a phosphoric acid solution, and the target extractant is an organic extractant, which can extract phosphoric acid from the feed liquid containing phosphoric acid to form an extraction feed liquid.

[0049] More specifically, the organic extractant is a mixture of tributyl phosphate and an additive in a weight ratio of 6:4; the additive is preferably kerosene.

[0050] The weight content of the extractant in the target raffinate acid and the weight content of the raffinate acid in the target extractant can be detected by gas chromatography or high performance liquid chromatography. The weight content of the extractant in the target raffinate acid is less than 0.01%, i.e. the total weight content of tri-butyl phosphate and kerosene is less than 0.01% when the target raffinate acid is subjected to gas chromatography or high performance liquid chromatography; the weight content of the raffinate acid (phosphoric acid) in the target extractant is less than 0.01%.

[0051] Example 1

[0052] A method for centrifugal separation and de-esterification of raffinate acid, comprising introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator for centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0053] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 99:1, the density of the raffinate acid in the mixed solution ranges from 1.45 to 1.50 g / mL, and the density of the extractant ranges from 0.98 to 0.985 g / mL. The rated rotation speed of the centrifugal separator is 2800 r / min, and the stirring frequency is adjusted within 26-46 Hz during centrifugal separation.

[0054] Example 2

[0055] A method for centrifugal separation and de-esterification of raffinate acid, comprising introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator for centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0056] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 80:20, the density of the raffinate acid in the mixed solution ranges from 1.15 to 1.18 g / mL, and the density of the extractant ranges from 0.95 to 0.96 g / mL. The rated rotation speed of the centrifugal separator is 6500 r / min, and the stirring frequency is adjusted within 26-46 Hz during centrifugal separation.

[0057] Example 3

[0058] A method for centrifugal separation and de-esterification of raffinate acid, comprising introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator for centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0059] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 90:10, the density of the raffinate acid in the mixed solution ranges from 1.25 to 1.30 g / mL, and the density of the extractant ranges from 0.97 to 0.98 g / mL. The rated rotation speed of the centrifugal separator is 4500 r / min, and the stirring frequency is adjusted within 26-46 Hz during centrifugal separation.

[0060] Example 4

[0061] A method for centrifugal separation of raffinate acid, comprising: introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator through a pump for continuous centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0062] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 95:5, the density of the raffinate acid in the mixed solution ranges from 1.45 to 1.50 g / mL, and the density of the extractant ranges from 0.98 to 0.985 g / mL.

[0063] The rated rotating speed of the centrifugal separator is 2800 r / min, and the frequency of stirring is adjusted within 26-46 Hz during centrifugal separation.

[0064] The pump-in flow rate of the pump for conveying the mixed solution is 15 kg / h.

[0065] Example 5

[0066] A method for centrifugal separation of raffinate acid, comprising: introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator through a pump for continuous centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0067] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 96:4, the density of the raffinate acid in the mixed solution ranges from 1.15 to 1.20 g / mL, and the density of the extractant ranges from 0.95 to 0.965 g / mL.

[0068] The rated rotating speed of the centrifugal separator is 6500 r / min, and the frequency of stirring is adjusted within 26-46 Hz during centrifugal separation.

[0069] The pump-in flow rate of the pump for conveying the mixed solution is 1000 kg / h.

[0070] Example 6

[0071] A method for centrifugal separation of raffinate acid, comprising: introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator through a pump for continuous centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0072] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 98:2, the density of the raffinate acid in the mixed solution ranges from 1.35 to 1.40 g / mL, and the density of the extractant ranges from 0.96 to 0.97 g / mL.

[0073] The rated rotating speed of the centrifugal separator is 4400 r / min, and the frequency of stirring is adjusted within 26-46 Hz during centrifugal separation.

[0074] The pump-in flow rate of the pump conveying the mixed solution is 200 kg / h.

[0075] Comparative Example 1

[0076] A method for centrifugal separation of raffinate acid to remove ester, comprising introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator for centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0077] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 99:1, the density of the raffinate acid in the mixed solution ranges from 1.45 g / mL to 1.50 g / mL, and the density of the extractant ranges from 0.98 g / mL to 0.985 g / mL. The rated rotation speed of the centrifugal separator is 1000 r / min, and the frequency of stirring is adjusted within 26 Hz to 46 Hz during centrifugal separation.

[0078] Comparative Example 2

[0079] A method for centrifugal separation of raffinate acid to remove ester, comprising introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator for centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0080] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 99:1, the density of the raffinate acid in the mixed solution ranges from 1.05 g / mL to 1.09 g / mL, and the density of the extractant ranges from 0.98 g / mL to 0.985 g / mL. The rated rotation speed of the centrifugal separator is 10000 r / min, and the frequency of stirring is adjusted within 26 Hz to 46 Hz during centrifugal separation.

[0081] Comparative Example 3

[0082] A method for centrifugal separation of raffinate acid to remove ester, comprising introducing a mixed solution containing raffinate acid and extractant into a centrifugal separator for centrifugal separation, and obtaining target extractant and target raffinate acid after separation.

[0083] The volume content ratio of the extractant and the raffinate acid in the mixed solution is 95:5, the density of the raffinate acid in the mixed solution ranges from 1.25 g / mL to 1.30 g / mL, and the density of the extractant ranges from 0.98 g / mL to 0.985 g / mL.

[0084] The rated rotation speed of the centrifugal separator is 2800 r / min, and the frequency of stirring is adjusted within 26 Hz to 46 Hz during centrifugal separation.

[0085] The pump-in flow rate of the pump conveying the mixed solution is 5 kg / h.

[0086] Specifically, the density of the raffinate acid, the density of the extractant in the mixed solution in Examples 1-6 and Comparative Example 1 were calculated by detecting the density of the upper layer of the mixed solution and the lower layer of the mixed solution.

[0087] The target raffinate acid and the target extractant prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to content detection and density detection, and were observed after standing at room temperature for 120 h. The detection results are summarized in Table 1 below.

[0088] Table 1

[0089]

[0090]

[0091] From Table 1, it can be seen that in all examples, the weight content of the extractant in the target raffinate acid is less than 0.01%, and the weight content of the raffinate acid in the target extractant is also less than 0.01%, so the centrifugal separation technology can effectively separate the raffinate acid and the extractant; the separated raffinate acid and the extractant both show good stability, without layering or oil film phenomenon, and remain stable after standing for a long time.

[0092] Examples 4-6 use pumping to realize continuous production, and even under different flow conditions (such as 15 kg / h to 1000 kg / h), stable separation effect can be maintained, which is an important advantage for industrial application. The method described in the application significantly improves production efficiency.

[0093] In Comparative Example 1, the rated speed of the centrifugal separator is only 1000 r / min, which is much lower than 2800-6500 r / min in the examples. Because the lower speed means that the centrifugal force generated is not enough to effectively separate the liquids with different densities, resulting in more extractant residues in the raffinate acid, the weight content of the extractant in the target raffinate acid is 0.5%, and the weight content of the raffinate acid in the target extractant is 0.35%.

[0094] In Comparative Example 2, the centrifugal separator has a very high speed (10000 r / min), but the density of the raffinate acid in the mixed solution is close to that of the extractant (1.05-1.09 g / mL vs 0.98-0.985 g / mL), which makes it difficult for the two to completely separate at high speed. In addition, too high speed can also cause excessive wear of the equipment and affect the separation efficiency. Therefore, the weight content of the extractant in the target raffinate acid is 0.8%, and the weight content of the raffinate acid in the target extractant is as high as 5.3%.

[0095] In Comparative Example 3, the pump-in flow rate of the pump delivering the mixture is only 5 kg / h, which is much lower than the 15-1000 kg / h in the examples. The low flow rate can cause the mixture to enter the centrifugal separator at a too slow speed, thus prolonging the separation time and reducing the separation efficiency. Meanwhile, the slow feeding speed can also cause the material to stay in the separator for too long, increasing the possibility of re-mixing of the two phases. Therefore, the weight content of the extractant in the target raffinate acid is 0.4%, and the weight content of the raffinate acid in the target extractant is 0.7%.

[0096] The above description is merely preferred embodiments of the present application, but not to limit the present application. Any modification, equivalent replacement and improvement made within the principle and spirit of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for centrifugal separation of deesterified raffinate acid, characterized by, The mixture containing the raffinate acid and the extractant is introduced into a centrifugal separator for separation; The volume content ratio of the extractant and the raffinate acid in the mixture is 96:4-98:2; The frequency of stirring is controlled by frequency conversion when the separation is carried out in the centrifugal separator; The rotating speed of the centrifugal separator is 2800-6500 r / min; The mixture is introduced into the centrifugal separator by a pump for continuous centrifugal separation; The pump flow rate of the mixture introduced by the pump is 15-1000 kg / h; The target raffinate acid and the target extractant are obtained after the mixture is introduced into the centrifugal separator for separation; the specific gravity of the target raffinate acid is 1.15-1.50 g / mL, and the specific gravity of the target extractant is 0.95-0.985 g / mL; The weight content of the extractant in the target raffinate acid is <0.01%, and the weight content of the raffinate acid in the target extractant is <0.01%; The mixture is prepared as follows: after the extractant is used to extract the feed liquid containing phosphoric acid, the upper layer is the extracted feed liquid; the extracted feed liquid is subjected to stripping treatment, and the lower layer is the stripping liquid; the stripping liquid is collected to obtain the mixture.

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