A method for separating a mixed solution containing hydrogen fluoride and sulfuric acid

Abstract

The present invention relates to the technical field of hydrogen fluoride preparation, and particularly to a method for separating a mixed solution containing hydrogen fluoride and sulfuric acid. The separation method includes: A) Concentrated fluorosilicic acid and concentrated sulfuric acid react in a reaction device to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride; B) The first part of the sulfuric acid solution containing hydrogen fluoride is subjected to two-stage separation to obtain hydrogen fluoride gas; the second part of the sulfuric acid solution containing hydrogen fluoride is heated and recycled to the reaction device. The present invention adopts two-stage separation; another path of the sulfuric acid solution containing hydrogen fluoride led out after the main reaction enters the reaction device again after being heated, with relatively low energy consumption. Therefore, the separation method provided by the present invention separates hydrogen fluoride from the sulfuric acid solution with relatively low energy consumption and can reduce fluorine loss.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen fluoride preparation, and particularly to a method for separating a mixed solution containing hydrogen fluoride and sulfuric acid. Background Art

[0002] The main reaction formula for the one-step preparation of anhydrous hydrogen fluoride from fluosilicic acid in the prior art is shown in Formula (1):

[0003]

[0004] Concentrated fluosilicic acid is decomposed by concentrated sulfuric acid to generate silicon tetrafluoride and hydrogen fluoride. The reaction principle is that concentrated sulfuric acid dilutes and releases heat, and concentrated fluosilicic acid is decomposed by heating to generate a mixed gas of HF and SiF 4 In the prior art, HF is mainly separated from the mixed gas. Specifically, the mixed gas of HF and SiF 4 is introduced into concentrated sulfuric acid. HF is absorbed by concentrated sulfuric acid, and SiF 4 is released as a gas. Subsequently, the HF is separated from the concentrated sulfuric acid by distillation; or, due to the different boiling points of HF and SiF 4 gases, HF is condensed by cooling. However, these methods have high energy consumption, many separation steps, serious fluorine loss, and poor subsequent separation effect. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for separating a mixed solution containing hydrogen fluoride and sulfuric acid. The separation method provided by the present invention separates hydrogen fluoride from the sulfuric acid solution with lower energy consumption and can reduce fluorine loss.

[0006] The present invention provides a method for separating a mixed solution containing hydrogen fluoride and sulfuric acid, comprising the following steps:

[0007] A) Concentrated fluosilicic acid and concentrated sulfuric acid react in a reaction device to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride;

[0008] B) The first part of the sulfuric acid solution containing hydrogen fluoride is separated in a two-stage manner to obtain hydrogen fluoride gas;

[0009] The second part of the sulfuric acid solution containing hydrogen fluoride is heated and recycled to the reaction device.

[0010] Preferably, in step B), any existing separation means, such as distillation separation, is adopted in the two-stage separation; after the two-stage separation, the following steps are further included:

[0011] The mother liquor obtained from the two-stage separation is stripped to obtain high-temperature hydrogen fluoride gas, which is mixed with the second part of the sulfuric acid solution containing hydrogen fluoride and then subjected to heat exchange.

[0012] Preferably, in step B), the two-stage separation of the first part of the sulfuric acid solution containing hydrogen fluoride includes:

[0013] Performing primary distillation on the first part of the sulfuric acid solution containing hydrogen fluoride at 100 - 160 °C;

[0014] Performing secondary distillation on the solution after the primary distillation at 130 - 180 °C.

[0015] Preferably, in step B), the volume ratio of the first part of the sulfuric acid solution containing hydrogen fluoride to the second part of the sulfuric acid solution containing hydrogen fluoride is 0.25 - 4:1.

[0016] Preferably, the separation system for implementing the separation method includes:

[0017] A reaction device;

[0018] A two-stage separator; the two-stage separator is connected to the first liquid outlet of the reaction device;

[0019] A sulfuric acid tower; the liquid inlet of the sulfuric acid tower is connected to the second liquid outlet of the reaction device; the liquid outlet of the sulfuric acid tower is connected to the recycled liquid inlet of the reaction device.

[0020] Preferably, it further includes: a stripping tower;

[0021] The inlet of the stripping tower is connected to the liquid outlet of the two-stage separator;

[0022] The gas outlet of the stripping tower is connected to the gas inlet of the sulfuric acid tower.

[0023] Preferably, the operating temperature of the sulfuric acid tower is higher than the operating temperature of the reaction device.

[0024] In the present invention, after the main reaction section, the sulfuric acid solution containing hydrogen fluoride is shunted, and increasing the circulation path is beneficial to reducing the treatment amount of dilute sulfuric acid, reducing the discharge of waste dilute sulfuric acid solution from the system to the external system, and improving the production efficiency of the system; at the same time, compared with the traditional one-step separation, the two-stage separation method has higher heat exchange efficiency, a compact device layout, and reduces the operating energy consumption of the system. Therefore, the separation method provided by the present invention further promotes the release of hydrogen fluoride in the mixed liquid on the basis of reducing energy consumption and improves the product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a separation flow chart of a mixed solution containing hydrogen fluoride and sulfuric acid provided by an embodiment of the present invention;

[0026] Figure 2 It is a separation flow chart of a mixed solution containing hydrogen fluoride and sulfuric acid provided by another embodiment of the present invention;

[0027] Figure 3 Separation flowchart of a mixed solution containing hydrogen fluoride and sulfuric acid provided for another embodiment of the present invention. Detailed implementation manners

[0028] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] The present invention provides a method for separating a mixed solution containing hydrogen fluoride and sulfuric acid, including the following steps:

[0030] A) Concentrated fluorosilicic acid and concentrated sulfuric acid react in a reaction device to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride;

[0031] B) Perform two-stage separation on the first part of the sulfuric acid solution containing hydrogen fluoride to obtain hydrogen fluoride gas;

[0032] Heat the second part of the sulfuric acid solution containing hydrogen fluoride and reuse it in the reaction device.

[0033] In step A):

[0034] Concentrated fluorosilicic acid and concentrated sulfuric acid react in a reaction device to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride.

[0035] In certain embodiments of the present invention, the mass concentration of the concentrated fluorosilicic acid is 25% - 55%, preferably 35% - 45%; the mass concentration of the concentrated sulfuric acid is 80% - 98%.

[0036] The present invention does not have special limitations on the reaction parameters of the concentrated fluorosilicic acid and the concentrated sulfuric acid in the reaction device, and the reaction parameters well-known to those skilled in the art can be adopted.

[0037] The temperature of the product solution after the reaction is 80 - 150 °C. In the product solution, the mass concentration of sulfuric acid is 50% - 85%. After the reaction, a small amount of hydrogen fluoride gas is contained in the gas containing silicon tetrafluoride and is released from the solution, and most of the hydrogen fluoride remains in the product solution.

[0038] In step B):

[0039] Perform two-stage separation on the first part of the sulfuric acid solution containing hydrogen fluoride to obtain hydrogen fluoride gas;

[0040] Heat the second part of the sulfuric acid solution containing hydrogen fluoride and reuse it in the reaction device.

[0041] In certain embodiments of the present invention, the two-stage separation of the first part of the sulfuric acid solution containing hydrogen fluoride includes:

[0042] Performing primary distillation on the first part of the sulfuric acid solution containing hydrogen fluoride at 100 - 160 °C;

[0043] Performing secondary distillation on the solution after the primary distillation at 130 - 180 °C.

[0044] The primary distillation is carried out in a first distillation device; the first distillation device can be a generally commercially available distillation device.

[0045] The secondary distillation is carried out in a second distillation device; the second distillation device can be a generally commercially available distillation device.

[0046] During the two-stage separation process, the sulfuric acid solution containing hydrogen fluoride is preheated by the first distillation device. At this time, hydrogen fluoride gradually releases from the solution in the form of gas, and then enters the second distillation device. At this time, most of the hydrogen fluoride releases from the sulfuric acid solution in the form of gas. Therefore, the two-stage separation can recover hydrogen fluoride in the sulfuric acid solution containing hydrogen fluoride.

[0047] Meanwhile, the two-stage separation method in a staged manner can reduce the device volume and increase the heat exchange area compared with the primary distillation, thereby reducing the energy consumption.

[0048] In certain embodiments of the present invention, after the two-stage separation, it further includes:

[0049] Performing stripping on the mother liquor obtained from the two-stage separation to obtain high-temperature hydrogen fluoride gas, mixing it with the second part of the sulfuric acid solution containing hydrogen fluoride for heat exchange. The heated sulfuric acid solution containing hydrogen fluoride is recycled to the reaction device.

[0050] The stripping can extract the residual hydrogen fluoride in the mother liquor, that is, obtain high-temperature hydrogen fluoride gas. In addition, the fluorine loss can be further reduced through stripping. The stripping is carried out in a stripping tower.

[0051] In certain embodiments of the present invention, the heat exchange is carried out in a sulfuric acid tower.

[0052] The high-temperature hydrogen fluoride gas is transported to the sulfuric acid tower, and heat exchange is carried out with the sulfuric acid solution containing hydrogen fluoride entering the sulfuric acid tower, thereby increasing the temperature of the sulfuric acid solution recycled to the reaction device and increasing the starting temperature of the subsequent two-stage separation.

[0053] In certain embodiments of the present invention, the volume ratio of the first part of the sulfuric acid solution containing hydrogen fluoride to the second part of the sulfuric acid solution containing hydrogen fluoride is 0.25 - 4:1.

[0054] The system for implementing the separation method of the present invention includes a reaction device. The present invention does not impose any special restrictions on the type and size of the reaction device, and a reaction vessel well-known to those skilled in the art can be used; it also includes a two-stage separation device; the two-stage separation device is connected to the first liquid outlet of the reaction device. In some embodiments of the present invention, the two-stage separator includes a first distillation device and a second distillation device connected in sequence. The liquid inlet of the first distillation device is connected to the first liquid outlet of the reaction device; the liquid inlet of the second distillation device is connected to the liquid outlet of the first distillation device. Both the first distillation device and the second distillation device can be general commercially available distillation devices.

[0055] Furthermore, the system for implementing the separation method of the present invention further includes a sulfuric acid tower. In some embodiments of the present invention, the operating temperature of the sulfuric acid tower is higher than that of the reaction device. The liquid inlet of the sulfuric acid tower is connected to the second liquid outlet of the reaction device; the liquid outlet of the sulfuric acid tower is connected to the recycled liquid inlet of the reaction device. The sulfuric acid tower can be a general commercially available sulfuric acid tower.

[0056] In some embodiments of the present invention, the separation system further includes: a stripping tower. The inlet of the stripping tower is connected to the liquid outlet of the two-stage separator; the gas outlet of the stripping tower is connected to the gas inlet of the sulfuric acid tower. The stripping tower can be a general commercially available stripping tower.

[0057] The present invention does not impose any special restrictions on the material of the connecting pipes between the above-mentioned various devices, and the materials of the connecting pipes well-known to those skilled in the art can be used.

[0058] Another sulfuric acid solution containing hydrogen fluoride led out after the reaction of the present invention is heated in the sulfuric acid tower and then enters the reaction device again, which increases the reaction feed temperature, and further increases the starting temperature of the subsequent two-stage separation, reducing the energy consumption required for subsequent distillation; at the same time, the two-stage separation method can increase the heat exchange area and reduce the device volume compared with single-stage distillation, which is beneficial to further reducing the overall operating energy consumption of the system. The separation method provided by the present invention can effectively separate hydrogen fluoride and silicon tetrafluoride.

[0059] The present invention does not impose any special restrictions on the source of the raw materials used above, and they can be general commercially available ones.

[0060] In order to further illustrate the present invention, the following describes in detail a separation method for a mixed solution containing hydrogen fluoride and sulfuric acid provided by the present invention in combination with embodiments, but it should not be construed as a limitation on the protection scope of the present invention.

[0061] Example 1

[0062] Adopt asFigure 1 The separation system shown separates a mixed solution containing hydrogen fluoride and sulfuric acid, including the following steps:

[0063] 1) Concentrated fluosilicic acid (mass concentration of 45%) and concentrated sulfuric acid (mass concentration of 98%) react in a reaction device to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride; the temperature of the product solution after the reaction is 100°C, and in the product solution, the mass concentration of sulfuric acid is 75%;

[0064] 2) Perform two-stage separation on the first part of the sulfuric acid solution containing hydrogen fluoride:

[0065] Perform primary distillation on part of the sulfuric acid solution containing hydrogen fluoride in a first distillation device at 100°C;

[0066] Perform secondary distillation on the solution after the primary distillation in a second distillation device at 130°C;

[0067] After the two-stage separation, hydrogen fluoride gas and mother liquor are obtained; after detection, the residual fluorine rate in the mother liquor is 0.32%.

[0068] The mother liquor obtained from the two-stage separation is transported to a stripping tower for stripping to obtain high-temperature hydrogen fluoride gas, which is transported to a sulfuric acid tower to exchange heat with the second part of the sulfuric acid solution containing hydrogen fluoride entering the sulfuric acid tower; the operating temperature of the sulfuric acid tower is higher than the operating temperature of the reaction device;

[0069] The sulfuric acid solution in the sulfuric acid tower is recycled to the reaction device;

[0070] The volume ratio of the first part of the sulfuric acid solution containing hydrogen fluoride to the second part of the sulfuric acid solution containing hydrogen fluoride is 0.25 - 4:1.

[0071] Raw material fluosilicic acid and raw material concentrated sulfuric acid react in a reaction device to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride; as described above, after the reaction, it is split into two streams of sulfuric acid solution containing hydrogen fluoride, and the sulfuric acid solution containing hydrogen fluoride in circulation is introduced into the sulfuric acid tower; the initial concentrated sulfuric acid flows through the silicon tetrafluoride generation tower, and the silicon tetrafluoride gas generated in this area contains H 2 O, HF, H 2 SO 4Impurities such as steam enter the sulfuric acid solution. In the sulfuric acid tower, the recycled sulfuric acid solution containing hydrogen fluoride is mixed with the sulfuric acid solution flowing through the silicon tetrafluoride generation tower and reused as the raw material sulfuric acid in the main reaction zone. In this solution, the hydrogen fluoride gas returned to the sulfuric acid tower from each route can be further dried and absorbed through the above-mentioned circulation pipeline, such as the high-temperature hydrogen fluoride gas obtained by stripping and the light-component gas recovered by rectification, and the soluble impurities contained in the gas are removed. The hydrogen fluoride gas in the sulfuric acid tower is transported to the silicon tetrafluoride generation tower for drying.

[0072] In this embodiment, the mother liquor separated in the distillation zone is stripped to obtain high-temperature hydrogen fluoride gas and transported to the sulfuric acid tower; the initial concentrated sulfuric acid enters the silicon tetrafluoride generation tower and the sulfuric acid tower in sequence to dry the silicon tetrafluoride gas led out from the main reaction zone and the high-temperature hydrogen fluoride gas obtained by stripping; the initial concentrated sulfuric acid enters the silicon tetrafluoride generation tower and is mixed with the recycled sulfuric acid solution containing hydrogen fluoride in the sulfuric acid tower and then reused in the main reaction zone. This process absorbs heat during the sulfuric acid circulation, raises the temperature of the reaction zone, reduces the steam consumption required for separating the sulfuric acid solution containing hydrogen fluoride, and can significantly reduce energy consumption. After detection, the total recovery rate of hydrogen fluoride is 98.5%.

[0073] Comparative Example 1

[0074] The difference between this comparative example and Example 1 is that only one-stage distillation is used, and the temperature of the one-stage distillation is 100 °C. After detection, the residual fluorine rate in the mother liquor is 1.80%.

[0075] Comparative Example 2

[0076] The difference between this comparative example and Example 1 is that only one-stage distillation is used, and the temperature of the one-stage distillation is 130 °C. The residual fluorine rate in the mother liquor is 1.50%.

[0077] Example 2

[0078] The difference between this example and Example 1 is that the temperature of the first-stage distillation is 100 °C, and the temperature of the second-stage distillation is 180 °C. After the two-stage separation, hydrogen fluoride gas and mother liquor are obtained; after detection, the residual fluorine rate in the mother liquor is 0.27%.

[0079] Example 3

[0080] The difference between this example and Example 1 is that the temperature of the first-stage distillation is 120 °C, and the temperature of the second-stage distillation is 150 °C. After the two-stage separation, hydrogen fluoride gas and mother liquor are obtained; after detection, the residual fluorine rate in the mother liquor is 0.24%.

[0081] Example 4

[0082] The difference between this embodiment and Embodiment 1 is that the primary distillation temperature is 160°C, the secondary distillation temperature is 180°C. After the two-stage separation, hydrogen fluoride gas and mother liquor are obtained. After detection, the residual fluorine rate in the mother liquor is 0.22%.

[0083] Embodiment 5

[0084] This embodiment uses a separation system as shown in Figure 2 to separate the mixed solution of hydrogen fluoride and sulfuric acid. The difference from Embodiment 1 is that

[0085] it does not contain a stripping column and specifically includes:

[0086] including the following steps:

[0087] 1) Concentrated fluorosilicic acid (mass concentration of 45%) and concentrated sulfuric acid (mass concentration of 98%) react in a reaction device to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride. The temperature of the product solution after the reaction is 100°C, and in the product solution, the mass concentration of sulfuric acid is 75%.

[0088] 2) Perform two-stage separation on the first part of the sulfuric acid solution containing hydrogen fluoride:

[0089] Perform primary distillation on a part of the sulfuric acid solution containing hydrogen fluoride in a first distillation device at 100°C.

[0090] Perform secondary distillation on the solution after the primary distillation in a second distillation device at 130°C.

[0091] After the two-stage separation, hydrogen fluoride gas and mother liquor are obtained. After detection, the residual fluorine rate in the mother liquor is 0.36.

[0092] Transport the second part of the sulfuric acid solution containing hydrogen fluoride to a sulfuric acid tower for heating and recycle it to the reaction device. The operating temperature of the sulfuric acid tower is higher than that of the reaction device.

[0093] The volume ratio of the first part of the sulfuric acid solution containing hydrogen fluoride to the second part of the sulfuric acid solution containing hydrogen fluoride is 0.25 - 4:1.

[0094] Embodiment 6

[0095] Use a separation system as shown in Figure 3 to separate the mixed solution of hydrogen fluoride and sulfuric acid,

[0096] without a stripping column, specifically including:

[0097] including the following steps:

[0098] 1) Concentrated fluosilicic acid (mass concentration of 45%) and concentrated sulfuric acid (mass concentration of 98%) react in a reaction device to produce silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride; the temperature of the product solution after the reaction is 100 °C, and in the product solution, the mass concentration of sulfuric acid is 75%;

[0099] 2) The first part of the sulfuric acid solution containing hydrogen fluoride is subjected to two-stage separation:

[0100] Part of the sulfuric acid solution containing hydrogen fluoride is subjected to primary distillation in a first distillation device at 100 °C;

[0101] The solution after the primary distillation is subjected to secondary distillation in a second distillation device at 130 °C;

[0102] After the two-stage separation, hydrogen fluoride gas and mother liquor are obtained; after detection, the residual fluorine rate in the mother liquor is 0.35.

[0103] The second part of the sulfuric acid solution containing hydrogen fluoride is transported to a sulfuric acid tower for heating and recycled to the reaction device; the operating temperature of the sulfuric acid tower is higher than the operating temperature of the reaction device;

[0104] The volume ratio of the first part of the sulfuric acid solution containing hydrogen fluoride to the second part of the sulfuric acid solution containing hydrogen fluoride is 0.25 - 4:1.

[0105] 3) The hydrogen fluoride gas obtained after the two-stage separation is passed through an HF generation tower to remove moisture and then introduced into a purification tower for pre-purification to remove high-boiling-point impurity sulfuric acid.

[0106] The relevant data of the above embodiments and comparative examples are shown in Table 1.

[0107] Table 1 Relevant parameters and effects of Examples 1 - 6 and Comparative Examples 1 - 2

[0108]

[0109] In this embodiment, the residual fluorine rate is in mass percentage, and the calculation formula is the ratio of the residual fluorine mass after separation to the total mass of the sulfuric acid solution containing hydrogen fluoride.

[0110] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for separating a mixed solution containing hydrogen fluoride and sulfuric acid, comprising the following steps: A) Concentrated fluosilicic acid and concentrated sulfuric acid react in a reaction device to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride; B) Subject the first part of the sulfuric acid solution containing hydrogen fluoride to two-stage separation to obtain hydrogen fluoride gas; Subjecting the first part of the sulfuric acid solution containing hydrogen fluoride to two-stage separation includes: Performing first-stage distillation on the first part of the sulfuric acid solution containing hydrogen fluoride at 100 - 160 °C; Performing second-stage distillation on the solution after the first-stage distillation at 130 - 180 °C; Heating the second part of the sulfuric acid solution containing hydrogen fluoride and recycling it to the reaction device; The volume ratio of the first part of the sulfuric acid solution containing hydrogen fluoride to the second part of the sulfuric acid solution containing hydrogen fluoride is 0.25 - 4:

1.

2. The separation method according to claim 1, characterized in that, in step B), after the two-stage separation, it further includes: Stripping the mother liquor obtained from the two-stage separation to obtain high-temperature hydrogen fluoride gas, mixing it with the second part of the sulfuric acid solution containing hydrogen fluoride, and then performing heat exchange.

3. The separation method according to claim 1, characterized in that, The separation system for implementing the separation method includes: A reaction device; A two-stage separator; the two-stage separator is connected to the first liquid outlet of the reaction device; A sulfuric acid tower; the liquid inlet of the sulfuric acid tower is connected to the second liquid outlet of the reaction device; the liquid outlet of the sulfuric acid tower is connected to the recycled liquid inlet of the reaction device.

4. The separation method according to claim 3, characterized in that, it further includes: A stripping tower; The inlet of the stripping tower is connected to the liquid outlet of the two-stage separator; The gas outlet of the stripping tower is connected to the gas inlet of the sulfuric acid tower.

5. The separation method according to claim 3, characterized in that, The operating temperature of the sulfuric acid tower is higher than the operating temperature of the reaction device.

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