Separation system for chlorine-containing hydrogen fluoride

Abstract

The utility model relates to the technical field of chemical production equipment, and particularly discloses a chlorine-containing hydrogen fluoride separation system which comprises a condensing tower and an absorption separation tower which are sequentially connected, an absorption separation device comprises a tower body, a distribution disc and a filler section are sequentially arranged in the tower body from top to bottom, and a liquid inlet and a gas outlet are formed in the upper end of the tower body; a liquid outlet and an air inlet are formed in the lower end of the tower body, the air inlet and the liquid inlet are both formed in the radial direction of the tower body, and the liquid outlet and the air outlet are both formed in the axial direction of the tower body; dilute sulfuric acid is introduced into the liquid inlet. The utility model aims to solve the problem that the absorption and separation effect of chloride ions in fluosilicic acid of a separation system is not ideal in an existing production system for preparing hydrofluoric acid by a fluosilicic acid method.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical production equipment, in particular to a separation system for chlorine-containing hydrogen fluoride. Background Art

[0002] Anhydrous hydrogen fluoride (AHF) is the most basic chemical raw material in the fluorine chemical industry and is also the basis for the booming development of the fluorine chemical industry. The main industrial preparation technologies are the fluorite method and the fluorosilicic acid method. Due to problems such as high energy consumption and large pollution in the fluorite method process, the production of anhydrous hydrogen fluoride by the fluorite method is restricted. Therefore, the process for producing hydrogen fluoride by the fluorosilicic acid method has also gradually developed, mainly using by-product fluorosilicic acid from the decomposition of phosphate rock to produce phosphoric acid as the raw material; the process for producing hydrogen fluoride by the fluorosilicic acid method uses the sulfuric acid decomposition of the fluorosilicic acid method, adding concentrated sulfuric acid with a mass fraction of 90% or more to the concentrated fluorosilicic acid solution to decompose the fluorosilicic acid into hydrogen fluoride and silicon tetrafluoride gas. Most of the hydrogen fluoride is absorbed by sulfuric acid, and dilute sulfuric acid with a mass fraction of about 70% is produced; silicon tetrafluoride is difficult to absorb and escapes as a gas. This part of silicon tetrafluoride is absorbed by dilute fluorosilicic acid solution to produce white carbon black and make the dilute fluorosilicic acid become concentrated. The concentrated fluorosilicic acid reacts with concentrated sulfuric acid again, and so on in a cycle. The concentrated sulfuric acid that has absorbed hydrogen fluoride releases hydrogen fluoride through desorption, and anhydrous hydrofluoric acid can be obtained through refining. This part of the concentrated sulfuric acid mainly refers to a sulfuric acid solution with a concentration of more than 90%.

[0003] Since the chloride ion content of the externally supplied raw material fluorosilicic acid is in the range of 2000 - 3000 ppm, when the chloride ion content in the raw material fluorosilicic acid is high, it will lead to too high chloride ion content in the entire production system, increasing the internal circulation of chloride ions, thereby affecting product output and raw material and auxiliary material consumption. The existing absorption and separation device only uses two absorption towers for absorption and separation. The existing two absorption towers mainly absorb and separate impurities such as silicon tetrafluoride in HF gas, and the absorption and separation effect of chloride ions in fluorosilicic acid is not ideal. The chloride ions in and out of the entire production system are unbalanced, resulting in the continuous circulation and concentration of chloride ions in the production system. The chloride ion content in concentrated fluorosilicic acid is as high as more than 6%. Due to the property that chloride ions are easily soluble in the aqueous solution system and difficult to separate, it affects the product quality of subsequent production of hydrofluoric acid by the fluorosilicic acid method, and at the same time brings great impacts on production control, equipment corrosion, and safety and environmental protection. Summary of the Utility Model

[0004] Aiming at the deficiencies of the prior art, the technical problem solved by the utility model is to provide a separation system for chlorine-containing hydrogen fluoride, which solves the problem that the absorption and separation effect of chloride ions in fluorosilicic acid by the existing separation equipment is not ideal.

[0005] To solve the above problems, the technical solution adopted by the present utility model is: a separation system for chlorine-containing hydrogen fluoride, including an absorption separation tower, which comprises a first separation tower, a second separation tower and a third separation tower arranged in sequence. The absorption separation device includes a tower body, and a distribution plate and a packing section are arranged in the tower body from top to bottom in sequence. An inlet for liquid and an outlet for gas are provided at the upper end of the tower body, and an outlet for liquid and an inlet for gas are provided at the lower end of the tower body. The inlet for gas and the inlet for liquid are both arranged radially along the tower body, and the outlet for liquid and the outlet for gas are both arranged axially along the tower body; dilute sulfuric acid is introduced into the inlet for liquid.

[0006] The technical principle and beneficial effects generated by this solution are as follows: After being condensed by the condensation tower, the gas containing hydrogen chloride and hydrogen fluoride enters the separation tower from the inlet for gas at the bottom of the absorption separation tower, and then exits the separation tower from the outlet for gas at the top. Dilute sulfuric acid enters the absorption separation tower from the inlet for liquid at the top of the device, and then after being dispersed by the distribution plate, the dilute sulfuric acid liquid evenly passes through the packing section and flows to the lower end of the absorption separation tower; during this process, the liquid dilute sulfuric acid fully combines and absorbs with the chlorine-containing hydrogen fluoride gas, absorbs hydrogen fluoride back into the dilute sulfuric acid and returns it to the hydrogen fluoride generation system, while the chlorine-containing impurity gas enters the next system and then is absorbed and removed from the system.

[0007] Since the hydrogen fluoride production process by the fluosilicic acid method uses the sulfuric acid decomposition of fluosilicic acid method, a large amount of sulfuric acid solution with a mass fraction of about 70% will be generated. The sulfuric acid solution is used as the absorption liquid of the absorption separation tower to absorb hydrogen fluoride in the chlorine-containing hydrogen fluoride, thereby separating chloride ions in the gas; thus increasing the separation effect of gaseous chlorine-containing hydrogen fluoride. Reducing the internal circulation loss caused by hydrogen fluoride entering the concentration system and increasing the system output under the same load conditions. The equipment has a small volume, occupies less space for on-site installation, and has a good absorption effect. At the same time, it can be used as a gas-liquid separator to remove the entrained mist in the gas phase.

[0008] Further, the length of the packing section in the absorption separation tower is 500 - 1500 mm.

[0009] Further, the diameter of the packing in the packing section is 38 - 57 mm.

[0010] Further, the height of the absorption separation tower is 2500 - 4000 mm.

[0011] Further, the diameter of the absorption separation tower is 500 - 1000 mm.

[0012] By adopting a smaller size of the absorption and separation tower, a small-sized absorption tower can usually be filled with more efficient structured packing, enabling the packing to have a larger specific surface area. Due to the larger effective specific surface area of the packing, more gas-liquid contact surfaces are provided, thus improving the mass transfer efficiency. Secondly, due to the smaller size of the packed tower, the gas can achieve a lower pressure loss in the packing during upward movement, which helps to maintain the stable operation of the system. Experimental data shows that in the absorption process carried out in a small-sized absorption and separation tower, the error between the outlet gas concentration and the simulated predicted value is small, indicating that the small-sized tower has a high absorption efficiency.

[0013] Furthermore, the concentration range of the dilute sulfuric acid is 70%-90%.

[0014] Furthermore, the distribution plate adopts a hole plate structure. A trapezoidal ring is provided at the lower end of the riser pipe of the distribution plate. A plurality of air holes are opened on the side wall of the riser pipe. 2-5 groups of air holes are evenly spaced from top to bottom, and each group is evenly distributed with 3-5 air holes along the circumferential direction. They are named the first group of air holes, the second group of air holes, the third group of air holes, and the fourth group of air holes from top to bottom in sequence. The aperture diameters of the first group and the second group of air holes are larger than those of the third group and the fourth group of air holes.

[0015] By providing a plurality of air holes on the side wall of the riser pipe, it is convenient for the gas to flow out evenly from the riser pipe, so as to be fully contacted with the liquid. By setting air holes with different aperture diameters, the aperture diameter of the upper air holes is larger than that of the lower air holes, so that it is easier for the upper gas to flow out from the air holes during the upward movement of the gas; the lowermost air holes are inclined to facilitate the outflow of the gas.

[0016] Furthermore, the absorption and separation tower is made of steel lined with tetrafluoroethylene. The inner lining of the tetrafluoroethylene pipe has excellent corrosion resistance, and the outer steel sleeve can effectively protect the inner lining of the tetrafluoroethylene pipe from external force damage, and at the same time enhance the strength and pressure resistance performance of the whole pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of an embodiment of the present invention.

[0018] Figure 2 It is a schematic diagram of the structure of the riser pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following is further detailed through specific embodiments:

[0020] The reference numerals in the accompanying drawings of the specification include: tower body 1, air inlet 2, air outlet 3, liquid inlet 4, liquid outlet 5, distribution plate 6, riser pipe 61, first group of air holes 62, second group of air holes 63, third group of air holes 64, fourth group of air holes 65, trapezoidal ring 66, packing section 7.

[0021] The embodiment is basically as shown in the appended Figure 1As shown: A separation system for chlorine-containing hydrogen fluoride includes a condensation tower and an absorption separation tower connected in sequence. The absorption separation device includes a tower body 1. Inside the tower body 1, a distribution tray 6 and a packing section 7 are arranged in sequence from top to bottom. At the upper end of the tower body 1, there are a liquid inlet 4 and a gas outlet 3. At the lower end of the tower body 1, there are a liquid outlet 5 and a gas inlet 2. The gas inlet 2 and the liquid inlet 4 are both arranged radially along the tower body 1. The liquid outlet 5 and the gas outlet 3 are both arranged axially along the tower body 1. Dilute sulfuric acid is introduced into the liquid inlet 4, and the concentration range of the dilute sulfuric acid is 70%-90%.

[0022] The length of the packing section 7 in the absorption separation tower is 500 - 1500 mm, and the diameter of the packing is 38 - 57 mm. In this embodiment, it is preferably that the length of the packing section 7 is 1000 mm and the packing diameter is 45 mm. The height of the absorption separation tower is 2500 - 4000 mm, and the diameter is 500 - 1000 mm. In this embodiment, the height is preferably 3000 mm and the diameter is 650 mm. The absorption separation tower is made of steel-lined tetrafluoro material. By adopting a smaller size of the absorption separation tower, a small-sized absorption tower can usually be filled with more effective structured packing, making the packing have a larger specific surface area. Due to the larger effective specific surface area of the packing, more gas-liquid contact surfaces are provided, thereby improving the mass transfer efficiency. Secondly, due to the smaller size of the packed tower, the gas can achieve a lower pressure loss in the packing during the upward movement, which helps to maintain the stable operation of the system. Experimental data shows that in the absorption process carried out in a small-sized absorption separation tower, the error between the outlet gas concentration and the simulated predicted value is small, and the absorption separation tower with the size of this solution has a high absorption efficiency.

[0023] As Figure 2 shown, the distribution tray 6 adopts a hole plate structure. At the lower end of the riser pipe 61 of the distribution tray 6, there is a trapezoidal ring 66. A plurality of air holes are opened on the side wall of the riser pipe 61. Four groups of air holes are evenly spaced from top to bottom. Each group is evenly distributed with 4 air holes along the circumferential direction. They are named the first group of air holes 62, the second group of air holes 63, the third group of air holes 64, and the fourth group of air holes 65 from top to bottom. The aperture of the first group and the second group of air holes 63 is 5 mm, the aperture of the third group and the fourth group of air holes 65 is 4 mm. The fourth group of air holes 65 is located on the trapezoidal ring 66 and is inclined downward, and the inclination angle is 30°.

[0024] By arranging a plurality of air holes on the side wall of the riser pipe 61, it is convenient for the gas to flow out evenly from the riser pipe 61, so as to be fully contacted with the liquid. By setting air holes with different apertures, the aperture of the upper air holes is larger than that of the lower air holes, so that it is easier for the upper gas to flow out from the air holes during the upward movement of the gas; the lowermost air holes are inclined, which is convenient for the gas to flow out.

[0025] The chlorine-containing hydrogen fluoride gas enters the separation tower through the gas inlet 2 at the bottom of the absorption separation tower, and then discharges from the gas outlet 3 at the top of the tower. Dilute sulfuric acid enters the absorption separation tower through the liquid inlet 4 at the top of the device, and then after being dispersed by the distribution plate 6, the dilute sulfuric acid liquid evenly passes through the packing section 7 and flows to the lower end of the absorption separation tower; during this process, the liquid dilute sulfuric acid fully combines and absorbs with the chlorine-containing hydrogen fluoride gas, absorbs hydrogen fluoride back into the dilute sulfuric acid and returns to the hydrogen fluoride generation system, while the chlorine-containing impurity gas enters the next system and then is absorbed and removed from the system.

[0026] Since the hydrogen fluoride production process by the fluosilicic acid method uses the sulfuric acid decomposition of fluosilicic acid method, a large amount of dilute sulfuric acid will be generated. Using the dilute sulfuric acid as the absorption liquid in the absorption separation tower to absorb hydrogen fluoride in the chlorine-containing hydrogen fluoride, thereby separating the chloride ions in the gas; thus increasing the separation effect of the gas-phase chlorine-containing hydrogen fluoride. Reducing the internal circulation loss caused by hydrogen fluoride entering the concentration system and increasing the system output under the same load conditions. The equipment has a small volume, occupies less space for on-site installation, and has a good absorption effect. At the same time, it can be used as a gas-liquid separator to remove the entrained mist in the gas phase.

[0027] The above are only the embodiments of the present invention, and common knowledge such as the specific structures and characteristics known in the solutions is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to explain the content of the claims.

Claims

1. A separation system for chlorofluorohydrogen, characterized in that: It includes a condensation tower and an absorption separation tower connected in sequence. The absorption separation device includes a tower body, in which a distribution plate and a packing section are sequentially arranged from top to bottom. The upper end of the tower body is provided with a liquid inlet and a gas outlet, and the lower end of the tower body is provided with a liquid outlet and a gas inlet. The gas inlet and the liquid inlet are both arranged radially along the tower body, and the liquid outlet and the gas outlet are both arranged axially along the tower body; a sulfuric acid solution is introduced into the liquid inlet.

2. The separation system of hydrogen chloride fluoride according to claim 1, characterized in that: The length of the packing section in the absorption separation tower is 500 - 1500 mm.

3. The separation system for chlorine-containing hydrogen fluoride according to claim 1, characterized in that: The diameter of the packing in the packing section is 38 - 57 mm.

4. A separation system for chlorine-containing hydrogen fluoride according to claim 1, characterized in that: The height of the absorption separation tower is 2500 - 4000 mm.

5. The separation system for chlorofluorohydrogen according to claim 1, characterized in that: The diameter of the absorption separation tower is 500 - 1000 mm.

6. The separation system for chlorofluorohydrogen according to claim 1, characterized in that: The concentration range of the sulfuric acid solution is 70% - 90%.

7. The separation system of hydrogen chloride fluoride according to claim 1, characterized in that: The distribution plate adopts a hole plate structure. A trapezoidal ring is provided at the lower end of the riser pipe of the distribution plate. A plurality of air holes are opened on the side wall of the riser pipe. The air holes are evenly spaced in 2 - 5 groups from top to bottom, and each group is evenly distributed with 3 - 5 air holes in the circumferential direction. They are named the first group of air holes, the second group of air holes, the third group of air holes, and the fourth group of air holes from top to bottom. The aperture diameters of the first group and the second group of air holes are larger than those of the third group and the fourth group of air holes.

8. The separation system for chlorine-containing hydrogen fluoride according to claim 1, characterized in that: The absorption separation tower is made of steel lined with polytetrafluoroethylene.

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