Hydrogen chloride raw material deep dehydration system for recycling tail gas in chlor-alkali industry

Abstract

The utility model relates to a hydrogen chloride raw material deep dehydration system for chlor-alkali industrial tail gas recovery, which comprises a graphite heat exchanger, a liquid ring type vacuum unit and a drying tower, the graphite heat exchanger, the liquid ring type vacuum unit and the drying tower are sequentially connected, and the gas inlet end of the graphite heat exchanger is used for connecting chlor-alkali industrial tail gas; the gas inlet end of the liquid ring type vacuum unit is communicated with the gas outlet end of the graphite heat exchanger, the gas inlet end of the drying tower is communicated with the gas outlet end of the liquid ring type vacuum unit, the drying tower discharges the dehydrated hydrogen chloride to a recovery device, and a freezing method, a concentrated sulfuric acid drying method and a molecular sieve drying method are combined to obtain the hydrogen chloride recovery device which is relatively low in cost and high in efficiency. And the water content can be well controlled. Specifically, through the graphite heat exchanger, the liquid ring type vacuum unit and the drying tower which are connected in sequence, hydrogen chloride containing water is dehydrated in sequence, so that dehydration of hydrogen chloride is safely and efficiently completed with lower cost.

Description

Technical Field

[0001] The present application relates to the technical field of tail gas treatment, and in particular to a system for deep dehydration of hydrogen chloride raw materials for tail gas recovery in the chlor-alkali industry. Background Art

[0002] The chlor-alkali industry produces tail gas hydrogen chloride, which contains a large number of by-products. It is usually absorbed by water to form hydrochloric acid of different concentrations for sale. Water will affect the production efficiency and raw material consumption of hydrogen chloride. Due to the presence of water, side reactions may occur in the production process, which will not only consume more raw materials, but also reduce the yield of the target product. The market for electronic-grade hydrogen chloride is much better than the market for hydrochloric acid. In the process of preparing electronic-grade hydrogen chloride, a large amount of water in the tail gas of hydrogen chloride needs to be removed first. In the prior art, the freezing method and the concentrated sulfuric acid drying method have poor ability to control the moisture content, and the molecular sieve drying method has a high dehydration cost. Therefore, a hydrogen chloride dehydration device with low cost and high dehydration effect is urgently needed. Utility Model Content

[0003] In view of this, the present application proposes a deep dehydration system for hydrogen chloride raw materials for tail gas recovery in the chlor-alkali industry, which removes water from hydrogen chloride at a relatively low cost and with a relatively high dehydration efficiency.

[0004] According to one aspect of the present application, a system for deep dehydration of hydrogen chloride raw materials for tail gas recovery in the chlor-alkali industry is provided, comprising: a graphite heat exchanger, a liquid ring vacuum unit and a drying tower;

[0005] The graphite heat exchanger, the liquid ring vacuum unit and the drying tower are connected in sequence; and

[0006] The air inlet end of the graphite heat exchanger is suitable for connecting the tail gas of the chlor-alkali industry;

[0007] The air inlet end of the liquid ring vacuum unit is connected to the air outlet end of the graphite heat exchanger;

[0008] The air inlet end of the drying tower is communicated with the air outlet end of the liquid ring vacuum unit, and the drying tower discharges the dehydrated hydrogen chloride to a recovery device.

[0009] In a possible implementation, the method further includes: a buffer tank;

[0010] The buffer tank is arranged at the air inlet end of the graphite heat exchanger;

[0011] The air inlet end of the buffer tank is suitable for connecting the tail gas of the chlor-alkali industry;

[0012] The gas outlet end of the buffer tank is communicated with the gas inlet end of the graphite heat exchanger.

[0013] In one possible implementation, the buffer tank is a carbon steel tank.

[0014] In a possible implementation, the graphite heat exchanger includes: a primary graphite heat exchanger and a secondary graphite heat exchanger;

[0015] The air inlet end of the primary graphite heat exchanger is connected to the air outlet end of the buffer tank;

[0016] The air inlet end of the secondary graphite heat exchanger is connected to the air outlet end of the primary graphite heat exchanger, and the air outlet end of the secondary graphite heat exchanger is connected to the air inlet end of the liquid ring vacuum unit.

[0017] In a possible implementation, the cooling water temperature of the primary graphite heat exchanger is 5 degrees;

[0018] The cooling water temperature of the secondary graphite heat exchanger is -35 degrees.

[0019] In one possible implementation, the circulating liquid of the liquid ring vacuum unit is concentrated sulfuric acid.

[0020] In a possible implementation, the drying tower includes: a primary drying tower and a secondary drying tower;

[0021] The air inlet end of the primary drying tower is connected to the air outlet end of the ring vacuum unit;

[0022] The air inlet end of the secondary drying tower is connected to the air outlet end of the primary drying tower, and the dehydrated hydrogen chloride at the air outlet end of the secondary drying tower is sent to a recovery device.

[0023] In a possible implementation, molecular sieves are provided inside the primary drying tower and the secondary drying tower.

[0024] The beneficial effects of the deep dehydration system of hydrogen chloride raw materials for recovery of tail gas from the chlor-alkali industry of the embodiment of the present application are as follows: by combining the freezing method, the concentrated sulfuric acid drying method and the molecular sieve drying method, a relatively low-cost system with better control of moisture content is obtained. Specifically, the present application sequentially dehydrates the hydrogen chloride containing water through a graphite heat exchanger, a liquid ring vacuum unit and a drying tower connected in sequence. Among them, the graphite heat exchanger dehydrates the hydrogen chloride containing water to a small content by using the freezing method, the liquid ring vacuum unit dehydrates the hydrogen chloride containing water in large quantities by using the concentrated sulfuric acid drying method, and finally the drying tower deeply dehydrates the hydrogen chloride containing water, thereby completing the dehydration of hydrogen chloride safely and efficiently at a low cost.

[0025] Other features and aspects of the present application will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the present application and, together with the description, serve to explain the principles of the present application.

[0027] Figure 1 A schematic diagram of a system for deep dehydration of hydrogen chloride raw material for tail gas recovery in the chlor-alkali industry according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0028] Various exemplary embodiments, features and aspects of the present application will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0029] Among them, it needs to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the utility model or simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the utility model.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0031] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0032] In addition, in order to better illustrate the present application, numerous specific details are given in the following specific embodiments. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present application.

[0033] See also Figure 1The deep dehydration system of hydrogen chloride raw material for recovering tail gas from chlor-alkali industry of the embodiment of the present application comprises: a graphite heat exchanger 200, a liquid ring vacuum unit 300 and a drying tower 400. The graphite heat exchanger 200, the liquid ring vacuum unit 300 and the drying tower 400 are connected in sequence, and the air inlet end of the graphite heat exchanger 200 is used to connect the tail gas from chlor-alkali industry, the air inlet end of the liquid ring vacuum unit 300 is connected to the air outlet end of the graphite heat exchanger 200, the air inlet end of the drying tower 400 is connected to the air outlet end of the liquid ring vacuum unit 300, and the drying tower 400 discharges the dehydrated hydrogen chloride to the recovery equipment.

[0034] In this embodiment, by combining the freezing method, the concentrated sulfuric acid drying method and the molecular sieve drying method, a system with relatively low cost and better control of moisture content is obtained. Specifically, the present application sequentially dehydrates the hydrogen chloride containing water through the graphite heat exchanger 200, the liquid ring vacuum unit 300 and the drying tower 400 connected in sequence. Among them, the graphite heat exchanger 200 dehydrates the hydrogen chloride containing water to a small content by using the freezing method, the liquid ring vacuum unit 300 dehydrates the hydrogen chloride containing water partially and in large quantities by using the concentrated sulfuric acid drying method, and finally the drying tower 400 deeply dehydrates the hydrogen chloride containing water, thereby completing the dehydration of hydrogen chloride safely and efficiently at a low cost.

[0035] In a specific embodiment, the deep dehydration system of hydrogen chloride raw material recovered from chlor-alkali industrial tail gas also includes: a buffer tank 100, the buffer tank 100 is arranged at the air inlet end of the graphite heat exchanger 200, and the air inlet end is used to connect the chlor-alkali industrial tail gas, and the air outlet end is connected to the air inlet end of the graphite heat exchanger 200, and the buffered hydrogen chloride containing water is delivered to the graphite heat exchanger 200.

[0036] In this embodiment, the buffer tank 100 mainly functions to stabilize the flow of gas and ensure that the gas can flow smoothly before entering the graphite heat exchanger 200. When the hydrogen chloride tail gas enters the buffer tank 100, the space inside the tank can effectively reduce the pressure fluctuation and flow rate change of the gas. In this way, after passing through the buffer tank 100, the gas can enter the graphite heat exchanger 200 more evenly. At the same time, the buffer tank 100 can also play a certain buffering role to prevent the sudden change of gas flow from causing impact on subsequent processing equipment.

[0037] In addition, during the dehydration process of hydrogen chloride tail gas, the buffer tank 100 can also help reduce the moisture content in the gas. By reducing the flow rate of the gas and increasing the residence time of the gas in the tank, the moisture has more opportunities to separate from the gas, thereby improving the efficiency of the dehydration process.

[0038] In this embodiment, the buffer tank 100 is a carbon steel tank, which has good adsorption performance and chemical stability. The activated carbon in the carbon steel tank has a large number of micropores and specific surface area, which can effectively adsorb hydrogen chloride gas, thereby playing a role of buffering and storage. The carbon steel tank can also withstand a certain pressure and temperature, and has a high safety performance.

[0039] According to the above-mentioned embodiment, in a specific embodiment, the graphite heat exchanger 200 includes: a primary graphite heat exchanger 210 and a secondary graphite heat exchanger 220, the air inlet end of the primary graphite heat exchanger 210 is connected to the air outlet end of the buffer tank 100, the air inlet end of the secondary graphite heat exchanger 220 is connected to the air outlet end of the primary graphite heat exchanger 210, and the air outlet end of the secondary graphite heat exchanger 200 is connected to the air inlet end of the liquid ring vacuum unit 300, and the hydrogen chloride gas containing water is subjected to secondary heat exchange to remove the water in the hydrogen chloride gas, and both the primary graphite heat exchanger 210 and the secondary heat exchanger adopt a refrigeration method to reduce the partial pressure of water in the hydrogen chloride and control the water content between 500 and 1000 ppm.

[0040] In this embodiment, the cooling water temperature of the first-stage graphite heat exchanger 210 is 5 degrees, and the cooling water temperature of the second-stage graphite heat exchanger 200 is -35 degrees.

[0041] In a specific embodiment, the circulating liquid of the liquid ring vacuum unit 300 is concentrated sulfuric acid, which has strong water absorption. When the hydrogen chloride gas containing water passes through the liquid ring vacuum unit 300, the concentrated sulfuric acid can absorb the water in the gas, thereby reducing the water content in the hydrogen chloride.

[0042] In a specific embodiment, the drying tower 400 includes: a primary drying tower 410 and a secondary drying tower 420, the air inlet end of the primary drying tower 410 is connected to the air outlet end of the ring vacuum unit, the air inlet end of the secondary drying tower 420 is connected to the air outlet end of the primary drying tower 410, the dehydrated hydrogen chloride at the air outlet end of the secondary drying tower 420 is sent to the recovery device, and the molecular sieve is provided inside the primary drying tower 410 and the secondary drying tower 400. Specifically, the process of removing moisture from hydrogen chloride by molecular sieve in the drying tower 400 mainly includes three steps of adsorption, regeneration and cooling. Adsorption: When the hydrogen chloride gas containing water passes through the molecular sieve drying tower 400, water molecules will be adsorbed on the surface of the molecular sieve, that is, the water molecules are adsorbed by the molecular sieve and fixed on its surface. Regeneration: When the molecular sieve is saturated with adsorption, a regeneration operation is required to release the moisture adsorbed on the molecular sieve. Heating is usually used to release the adsorbed moisture by increasing the temperature of the molecular sieve.

[0043] In a specific embodiment, a low-cost and low-water removal freezing method and concentrated sulfuric acid drying method are first used to remove a large amount of water in hydrogen chloride, and finally the hydrogen chloride gas containing a small amount of water enters the drying tower 400 for fine dehydration, thereby increasing the dehydration depth at a low dehydration cost.

[0044] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A deep dehydration system for hydrogen chloride raw materials for tail gas recovery in chlor-alkali industry, characterized in that: include: Graphite heat exchangers, liquid ring vacuum units and drying towers; The graphite heat exchanger, the liquid ring vacuum unit and the drying tower are connected in sequence; and The air inlet end of the graphite heat exchanger is suitable for connecting the tail gas of the chlor-alkali industry; The air inlet end of the liquid ring vacuum unit is connected to the air outlet end of the graphite heat exchanger; The air inlet end of the drying tower is communicated with the air outlet end of the liquid ring vacuum unit, and the drying tower discharges the dehydrated hydrogen chloride to a recovery device.

2. The deep dehydration system for hydrogen chloride raw material for tail gas recovery in the chlor-alkali industry according to claim 1, characterized in that: Also includes: Buffer tank; The buffer tank is arranged at the air inlet end of the graphite heat exchanger; The air inlet end of the buffer tank is suitable for connecting the tail gas of the chlor-alkali industry; The gas outlet end of the buffer tank is communicated with the gas inlet end of the graphite heat exchanger.

3. The deep dehydration system for hydrogen chloride raw material for tail gas recovery in the chlor-alkali industry according to claim 2, characterized in that: The buffer tank is a carbon steel tank.

4. The deep dehydration system for hydrogen chloride raw material for tail gas recovery in the chlor-alkali industry according to claim 3, characterized in that: The graphite heat exchanger comprises: a primary graphite heat exchanger and a secondary graphite heat exchanger; The air inlet end of the primary graphite heat exchanger is connected to the air outlet end of the buffer tank; The air inlet end of the secondary graphite heat exchanger is connected to the air outlet end of the primary graphite heat exchanger, and the air outlet end of the secondary graphite heat exchanger is connected to the air inlet end of the liquid ring vacuum unit.

5. The deep dehydration system for hydrogen chloride raw material for tail gas recovery in the chlor-alkali industry according to claim 4, characterized in that: The cooling water temperature of the first-stage graphite heat exchanger is 5 degrees; The cooling water temperature of the secondary graphite heat exchanger is -35 degrees.

6. The deep dehydration system for hydrogen chloride raw material for tail gas recovery in the chlor-alkali industry according to any one of claims 1 to 3, characterized in that: The circulating liquid of the liquid ring vacuum unit is concentrated sulfuric acid.

7. The deep dehydration system for hydrogen chloride raw material for tail gas recovery in the chlor-alkali industry according to any one of claims 1 to 3, characterized in that: The drying tower comprises: a primary drying tower and a secondary drying tower; The air inlet end of the primary drying tower is connected to the air outlet end of the ring vacuum unit; The air inlet end of the secondary drying tower is connected to the air outlet end of the primary drying tower, and the dehydrated hydrogen chloride at the air outlet end of the secondary drying tower is sent to a recovery device.

8. The deep dehydration system for hydrogen chloride raw material for tail gas recovery in the chlor-alkali industry according to claim 7, characterized in that: Molecular sieves are arranged inside the primary drying tower and the secondary drying tower.

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