Hydrogen chloride tail gas separation and recovery method and hydrogen chloride tail gas separation and recovery system

Abstract

The application discloses a hydrogen chloride tail gas separation and recovery method and a hydrogen chloride tail gas separation and recovery system. The hydrogen chloride tail gas separation and recovery method comprises the following steps: compressing hydrogen chloride tail gas to obtain high-pressure gas; adopting a circulating solvent to absorb and treat the high-pressure gas, and obtaining a liquid-phase intermediate product; and adopting a resolution treatment on the liquid-phase intermediate product, and obtaining hydrogen chloride and a circulating solvent. The application realizes the separation of hydrogen chloride and non-condensable gas, obtains high-purity hydrogen chloride, has a simple process flow, can significantly improve the added value of hydrogen chloride, improves the quality of hydrogen chloride, reduces the waste gas treatment amount, so as to achieve the purposes of reducing production cost, improving economic benefits and reducing by-products.

Description

Technical Field

[0001] This application relates to the field of exhaust gas treatment technology, and in particular to a method and system for separating and recovering hydrogen chloride exhaust gas. Background Technology

[0002] Hydrogen chloride is an important industrial chemical substance widely used in the manufacture of rubber, pharmaceuticals, and other organic and inorganic products. High-purity hydrogen chloride also has extensive applications in the electronics industry. The by-product hydrogen chloride tail gas from chemical industrial parks contains a significant amount of organic matter and non-condensable gases, resulting in high impurities and insufficient purity. Therefore, it cannot be directly supplied to downstream PVC and epichlorohydrin production enterprises. Traditional technology typically treats this by-product hydrogen chloride tail gas by using water absorption to produce hydrochloric acid. However, due to the high organic matter content in the by-product hydrogen chloride tail gas, the hydrochloric acid produced by water absorption contains high levels of TOC and salt impurities, resulting in low-quality by-product hydrochloric acid and limiting its application. Furthermore, the current hydrochloric acid market is approaching saturation, making it difficult to sell low-quality hydrochloric acid. When chemical industrial parks are operating at high capacity, there is a high risk of low-quality by-product hydrochloric acid causing storage shortages and shutdowns.

[0003] Traditional technologies also employ a combination of falling film absorbers and water scrubbing towers, utilizing hydrochloric acid and water recycling, combined with intermediate heat removal technology, to achieve complete recovery and desorption of hydrogen chloride. However, this method generates concentrated hydrochloric acid through water absorption, and the desorption of concentrated hydrochloric acid produces hydrogen chloride gas containing water vapor, placing extremely stringent requirements on equipment materials. The equipment is prone to corrosion, resulting in high investment and maintenance costs. Alternatively, traditional technologies use pressure swing adsorption (PSA) to separate and recover chlorine and oxygen from a hydrogen chloride-hydrogen chloride mixture. Unreacted hydrogen chloride is absorbed with water, then dehydrated with concentrated sulfuric acid. The remaining mixture is then separated in a PSA unit to obtain high-purity chlorine and oxygen. However, PSA involves repeated pressure changes, resulting in high energy consumption, a large footprint, and high investment costs. Summary of the Invention

[0004] Therefore, it is necessary to provide a hydrogen chloride tail gas separation and recovery method that can separate hydrogen chloride gas from non-condensable gases in the exhaust gas, so that hydrogen chloride and non-condensable gases can be recovered and reused.

[0005] One embodiment of this application provides a method for separating and recovering hydrogen chloride tail gas.

[0006] A method for separating and recovering hydrogen chloride tail gas includes the following steps:

[0007] The tail gas of compressed hydrogen chloride is compressed to obtain high-pressure gas;

[0008] The high-pressure gas is absorbed using a circulating solvent to extract a liquid intermediate product.

[0009] Furthermore, the liquid intermediate product is subjected to analytical treatment to extract hydrogen chloride and recycled solvent.

[0010] In some embodiments, the pressure when the hydrogen chloride tail gas is compressed to obtain high-pressure gas is controlled to be 0.5 MPaG to 1.5 MPaG.

[0011] In some embodiments, a staged compression method is used when compressing hydrogen chloride tail gas to obtain high-pressure gas.

[0012] In some embodiments, the staged compression method includes the following steps: controlling the hydrogen chloride tail gas to undergo a first-stage compression treatment, wherein the pressure during the first-stage compression treatment is controlled to be 0.5 MPaG~0.7 MPaG;

[0013] The hydrogen chloride tail gas after the first stage compression is cooled.

[0014] Furthermore, the hydrogen chloride tail gas after cooling is subjected to a second-stage compression treatment, and the pressure during the second-stage compression treatment is controlled to be 0.7 MPaG~1.5 MPaG, wherein the pressure during the second-stage compression treatment is greater than the pressure during the first-stage compression treatment.

[0015] In some embodiments, a cooling medium is used for cooling.

[0016] In some embodiments, wet compression is used to obtain high-pressure gas from the compressed hydrogen chloride tail gas.

[0017] In some embodiments, the wet compression method includes the following steps: spraying an inert solvent onto the hydrogen chloride tail gas at the compression inlet, the inert solvent including one or more of chlorobenzene, toluene, and dimethyl carbonate.

[0018] In some embodiments, the circulating solvent includes one or more of chlorobenzene, methanol, ethyl acetate, and diethyl ether.

[0019] In some embodiments, the circulating solvent further includes an additive, wherein the mass ratio of the chlorobenzene to the additive is (80~90):(10~20), the additive includes γ-alumina and carbonate, the carbonate includes one or two of alkali metal carbonate and alkaline earth metal carbonate, and the mass ratio of the γ-alumina to the carbonate is (40~60):(40~60).

[0020] In some embodiments, when the high-pressure gas is absorbed using a circulating solvent, the temperature of the circulating solvent is controlled to be -40°C to 0°C.

[0021] In some embodiments, when the high-pressure gas is absorbed using a circulating solvent, the temperature of the circulating solvent is controlled to be -30°C to -10°C.

[0022] In some embodiments, the concentration of hydrogen chloride in the liquid intermediate is controlled to be 5 wt% to 20 wt%.

[0023] In some embodiments, the concentration of hydrogen chloride in the liquid intermediate is controlled to be 8 wt% to 16 wt%.

[0024] In some embodiments, when using a circulating solvent to absorb the high-pressure gas, a staged absorption method is employed.

[0025] In some embodiments, the graded absorption includes the following steps:

[0026] The high-pressure gas is subjected to a first-stage absorption treatment using a circulating solvent. The temperature of the first-stage absorption treatment is controlled at -15℃ to 0℃. The liquid intermediate product, which includes the circulating solvent, hydrogen chloride, and organic matter, as well as the exhaust gas, is collected.

[0027] The exhaust gas after the first stage absorption treatment is subjected to a second stage absorption treatment using a circulating solvent. The temperature of the second stage absorption treatment is controlled at -25℃ to -15℃. The reflux intermediate product, which includes part of the circulating solvent, hydrogen chloride and organic matter, is collected.

[0028] In addition, the reflux intermediate product is controlled to be refluxed back to the first-stage absorption treatment process for cyclic absorption.

[0029] In some embodiments, when the liquid intermediate is subjected to a analytical process, the analytical temperature is controlled to be 70°C to 120°C.

[0030] In some embodiments, when the liquid intermediate is subjected to a analytical process, the analytical temperature is controlled to be 75°C to 100°C.

[0031] In some embodiments, the desorption pressure is controlled at 6 bara to 10 bara when the liquid intermediate is desorbed.

[0032] In some embodiments, the desorption pressure is controlled at 7.5 bara to 8.5 bara when the liquid intermediate is desorbed.

[0033] In some embodiments, the hydrogen chloride tail gas separation and recovery method further includes the following step: removing impurities from the circulating solvent collected after the liquid intermediate product has been analyzed.

[0034] In some embodiments, the impurity removal process is carried out using a solvent purification system.

[0035] In some embodiments, the hydrogen chloride tail gas separation and recovery method further includes the following step: controlling the circulating solvent collected after the liquid intermediate product is analyzed to be returned to the absorption treatment process.

[0036] In some embodiments, the hydrogen chloride tail gas separation and recovery method further includes the following steps: cooling the mixed gas containing non-condensable gas and hydrogen chloride after the high-pressure gas is absorbed and treated, and then transporting it to the non-condensable gas recovery system.

[0037] One embodiment of this application also provides a hydrogen chloride tail gas separation and recovery system.

[0038] A hydrogen chloride tail gas separation and recovery system, comprising:

[0039] A compression mechanism is used to compress hydrogen chloride tail gas to obtain high-pressure gas.

[0040] An absorption tower is used to absorb the high-pressure gas by adding a circulating solvent and to extract the liquid intermediate product.

[0041] And a stripping column, used to strip the liquid intermediate product and extract hydrogen chloride and recycled solvent.

[0042] In some embodiments, the compression mechanism includes a compressor employing a wet compression method.

[0043] In some embodiments, the absorber packing in the absorber tower includes ball packing.

[0044] In some embodiments, the compression mechanism includes a first-stage compression sub-mechanism and a second-stage compression sub-mechanism.

[0045] In some embodiments, there are multiple absorption towers connected in series.

[0046] The aforementioned method for separating and recovering hydrogen chloride tail gas utilizes solvent absorption and desorption separation technology to separate hydrogen chloride from non-condensable gases in the tail gas. Specifically, in this application's method, the hydrogen chloride tail gas is separated from non-condensable gases through absorption and desorption using a circulating solvent, yielding high-purity hydrogen chloride. This application's process is simple, significantly increasing the added value and quality of hydrogen chloride while reducing waste gas treatment volume, thereby lowering production costs, improving economic efficiency, and reducing byproducts. High-quality hydrogen chloride can be used in downstream enterprises such as PVC and epichlorohydrin production plants, demonstrating a wide range of applications.

[0047] In the aforementioned hydrogen chloride tail gas separation and recovery system, the raw material tail gas containing hydrogen chloride, organic matter, and other non-condensable gases is pressurized by a compression mechanism and then enters an absorption tower. A large amount of non-condensable gas and a small amount of hydrogen chloride are collected from the top of the absorption tower. After depressurization, these are sent to the non-condensable gas recovery system. The bottom of the absorption tower collects a liquid intermediate product containing recycled solvent, hydrogen chloride, and a small amount of organic matter. This liquid intermediate product enters a desorption tower. The hydrogen chloride desorbed after heating is collected from the top of the desorption tower and sent to downstream processes. Simultaneously, a small amount of recycled solvent is collected from the bottom of the desorption tower and sent to a solvent purification system to remove organic impurities from the recycled solvent, preventing impurities from accumulating in the hydrogen chloride tail gas separation and recovery system. This hydrogen chloride tail gas separation and recovery system can directly purify hydrogen chloride gas containing non-condensable gases and organic impurities, reducing waste gas volume and by-product hydrochloric acid. It also produces high-value-added, high-purity hydrogen chloride products, achieving efficient recycling of chlorine resources in the chemical industrial park, resulting in significant economic and social benefits. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0050] Figure 1 This is a schematic diagram of a hydrogen chloride tail gas separation and recovery method according to an embodiment of this application;

[0051] Figure 2 This is a schematic diagram of a hydrogen chloride tail gas separation and recovery system according to an embodiment of this application.

[0052] Explanation of reference numerals in the attached figures

[0053] 10. Hydrogen chloride tail gas separation and recovery system; 100. Compression mechanism; 200a, 200b. Absorption tower; 300. Desorption tower; 400. Circulation pump. Detailed Implementation

[0054] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0055] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0056] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0057] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0058] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0059] In this document, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain."

[0060] In this application, unless otherwise stated, the sum of the parts of each component in the composition may be 100 parts by weight. Unless otherwise specified, the percentages (including weight percentages) in this application are based on the total weight of the composition, and "wt%" in this document means mass percentage.

[0061] In this document, unless otherwise stated, the reaction steps may be performed in the order described herein or not. For example, other steps may be included between reaction steps, and the order of reaction steps may be appropriately interchanged. This is something that those skilled in the art can determine based on conventional knowledge and experience. Preferably, the reaction methods described herein are performed sequentially.

[0062] In this application, when numerical intervals (i.e., numerical ranges) are mentioned, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0064] This application provides a method for separating and recovering hydrogen chloride tail gas to solve at least one of the following technical problems in the by-product hydrogen chloride tail gas of chemical industrial parks in the traditional technology: (1) The by-product hydrogen chloride tail gas contains a lot of organic matter and nitrogen non-condensable gas, and the by-product hydrogen chloride tail gas contains a lot of impurities, resulting in insufficient purity, so it cannot be directly supplied to downstream PVC and epichlorohydrin production enterprises. (2) The traditional technology uses water absorption to prepare hydrochloric acid to treat the by-product hydrogen chloride tail gas. The hydrochloric acid prepared by water absorption also contains a high content of TOC and salt impurities, resulting in low quality of by-product hydrochloric acid. On the one hand, it limits the application of by-product hydrochloric acid, and on the other hand, it is difficult to sell low-quality hydrochloric acid, which easily leads to the risk of low-quality by-product hydrochloric acid filling the warehouse and shutting down. The following will describe the method for separating and recovering hydrogen chloride tail gas with reference to the accompanying drawings.

[0065] The composition of the hydrogen chloride tail gas is as follows: 15wt%~45wt% inert gas, 55wt%~85wt% hydrogen chloride, 0.2wt%~1wt% inert organic matter, and <0.002wt% active organic matter. Inert gases include, but are not limited to, nitrogen, argon, carbon monoxide, carbon dioxide, and other gases that do not undergo chemical reactions during compression and transportation; inert organic matter includes, but is not limited to, chlorobenzene, toluene, carbon tetrachloride, and carbonyl chloride; active organic matter refers to substances that are prone to polymerization, salt formation, and other chemical reactions during compression and transportation, generating solid blockages.

[0066] The hydrogen chloride tail gas separation and recovery method provided in one embodiment of this application is exemplary; please refer to [link to relevant documentation]. Figure 1 As shown, Figure 1 This is a schematic diagram of a hydrogen chloride tail gas separation and recovery method provided in one embodiment of this application. The hydrogen chloride tail gas separation and recovery method of this application can be used to separate hydrogen chloride from non-condensable gases in hydrogen chloride tail gas, enabling the recovery and reuse of both hydrogen chloride and non-condensable gases. This optimizes the process flow, increases the added value of hydrogen chloride, reduces waste gas treatment volume, and achieves the goals of reducing production costs, improving economic efficiency, and reducing by-products.

[0067] To more clearly illustrate the structure of the hydrogen chloride tail gas separation and recovery method, the following description, in conjunction with the accompanying drawings, will be presented.

[0068] For example, please refer to Figure 1 As shown,

[0069] A method for separating and recovering hydrogen chloride tail gas includes the following steps:

[0070] S10, high-pressure gas is obtained by compressing the tail gas of compressed hydrogen chloride.

[0071] S20. High-pressure gas is absorbed and treated using a circulating solvent to extract a liquid intermediate product containing the circulating solvent, hydrogen chloride, and organic matter.

[0072] S30. The liquid intermediate product is analyzed to extract hydrogen chloride and recycled solvent.

[0073] The aforementioned method for separating and recovering hydrogen chloride tail gas utilizes solvent absorption and desorption separation technology to separate hydrogen chloride from non-condensable gases in the tail gas. In this application's method, the hydrogen chloride tail gas is separated from non-condensable gases through absorption by a circulating solvent and high-temperature desorption, yielding high-purity hydrogen chloride. This application's process is simple, significantly increasing the added value and quality of hydrogen chloride while reducing waste gas treatment volume, thereby lowering production costs, improving economic efficiency, and reducing byproducts. High-quality hydrogen chloride can be used in downstream enterprises such as PVC and epichlorohydrin manufacturers, demonstrating a wide range of applications.

[0074] In some embodiments, the pressure at which the hydrogen chloride tail gas is compressed to obtain a high-pressure gas is controlled to be between 0.5 MPaG and 1.5 MPaG. The pressure at which the hydrogen chloride tail gas is compressed to obtain a high-pressure gas includes, but is not limited to, 0.5 MPaG, 0.7 MPaG, 0.9 MPaG, 1 MPaG, 1.1 MPaG, 1.3 MPaG, 1.4 MPaG, 1.5 MPaG, or any range between the foregoing.

[0075] In some embodiments, a staged compression method is used when compressing hydrogen chloride tail gas to obtain high-pressure gas.

[0076] In some embodiments, the staged compression method includes the following steps: controlling the hydrogen chloride tail gas to undergo a first-stage compression treatment, wherein the pressure during the first-stage compression treatment is controlled to be 0.5 MPaG~0.7 MPaG;

[0077] The hydrogen chloride tail gas after the first stage compression process is cooled.

[0078] Furthermore, the hydrogen chloride tail gas after cooling is subjected to a second-stage compression treatment, and the pressure during the second-stage compression treatment is controlled to be 0.7 MPaG~1.5 MPaG, wherein the pressure during the second-stage compression treatment is greater than the pressure during the first-stage compression treatment.

[0079] In some embodiments, a cooling medium is used for cooling.

[0080] In some of these implementations, the cooling medium includes circulating water.

[0081] In some embodiments, wet compression is used to obtain high-pressure gas from the compressed hydrogen chloride tail gas.

[0082] In some embodiments, the wet compression method includes the following steps: spraying an inert solvent onto the hydrogen chloride tail gas at the compression inlet, the inert solvent including one or more of chlorobenzene, toluene, and dimethyl carbonate.

[0083] In some embodiments, the circulating solvent includes one or more of chlorobenzene, methanol, ethyl acetate, and diethyl ether.

[0084] In some embodiments, the circulating solvent further includes an additive. The mass ratio of chlorobenzene to the additive is (80-90):(10-20), for example, 80:20, 85:15, 90:10, or other ratios. The additive includes γ-alumina and carbonates, wherein the carbonates include one or both of alkali metal carbonates and alkaline earth metal carbonates. The mass ratio of γ-alumina to the carbonate is (40-60):(40-60), for example, 40:60, 45:55, 50:50, 55:45, 60:40, or other ratios. The circulating solvent containing the additive can reduce the hydrogen chloride impurity content in gaseous or liquid hydrocarbons to below 0.5 ppm.

[0085] In some embodiments, the alkali metal carbonate includes one or more of Li2CO3, Na2CO3, K2CO3, Rb2CO3, and Cs2CO3.

[0086] In some embodiments, when using a circulating solvent to absorb high-pressure gas, the temperature of the circulating solvent is controlled to be between -40°C and 0°C. For example, the temperature of the circulating solvent may be, but is not limited to, -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, or any range between the foregoing.

[0087] In some embodiments, when using a circulating solvent to absorb high-pressure gas, the temperature of the circulating solvent is controlled to be -10°C to -30°C.

[0088] In some embodiments, the concentration of hydrogen chloride in the liquid intermediate is controlled to be 5 wt% to 20 wt%. For example, the concentration of hydrogen chloride in the liquid intermediate may be controlled to be, but is not limited to, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 17 wt%, 18 wt%, 20 wt%, or any range between the two aforementioned.

[0089] In some embodiments, the concentration of hydrogen chloride in the liquid intermediate is controlled to be 8 wt% to 16 wt%.

[0090] In some embodiments, when using a circulating solvent to absorb high-pressure gases, a staged absorption method is employed.

[0091] In some embodiments, graded absorption includes the following steps:

[0092] The high-pressure gas is first-stage absorbed by a circulating solvent. The temperature of the first-stage absorption process is controlled at -15℃ to 0℃. The liquid intermediate product, including the circulating solvent, hydrogen chloride and organic matter, as well as the exhaust gas, are extracted.

[0093] The exhaust gas after the first stage of absorption treatment is subjected to a second stage of absorption treatment using a circulating solvent. The temperature of the second stage of absorption treatment is controlled at -25℃ to -15℃. The reflux intermediate product, which includes part of the circulating solvent, hydrogen chloride and a small amount of organic matter, and the mixed gas, which includes non-condensable gas and a small amount of hydrogen chloride, are collected.

[0094] In addition, the intermediate products are controlled to be recycled back to the first-stage absorption process for further absorption.

[0095] Staged absorption can improve the utilization rate of cold energy and circulating solvent, reduce the circulating solvent volume by 10%, thereby saving energy used for heating and cooling the circulating solvent, and achieving an overall energy saving of about 12%.

[0096] In some embodiments, when performing the desorption treatment on the liquid intermediate product, the desorption temperature is controlled to be 70°C to 120°C. For example, when performing the desorption treatment on the liquid intermediate product, the value of the desorption temperature includes, but is not limited to: 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, or any range between the foregoing.

[0097] In some embodiments, the desorption temperature is controlled at 75°C to 100°C when the liquid intermediate is desorbed.

[0098] In some embodiments, the desorption pressure is controlled to be 6 bara to 10 bara when desorbing the liquid intermediate. For example, the value of the desorption pressure when desorbing the liquid intermediate includes, but is not limited to, 6 bara, 7 bara, 8 bara, 9 bara, 10 bara or any range between the two mentioned above.

[0099] In some embodiments, the desorption pressure is controlled at 7.5 bara to 8.5 bara when the liquid intermediate is desorbed.

[0100] In some embodiments, the hydrogen chloride tail gas separation and recovery method further includes the following step: removing impurities from the circulating solvent collected after analyzing the liquid intermediate product.

[0101] In some embodiments, the impurity removal process is carried out using a solvent purification system.

[0102] In some embodiments, the hydrogen chloride tail gas separation and recovery method further includes the following step: controlling the circulating solvent collected after the liquid phase intermediate product is analyzed and then refluxed to the absorption treatment process.

[0103] In some embodiments, the hydrogen chloride tail gas separation and recovery method further includes the following steps: cooling the mixed gas containing non-condensable gas and hydrogen chloride obtained after absorbing the high-pressure gas, and then conveying it to a non-condensable gas recovery system. This application enables the recovery and reuse of hydrogen chloride and non-condensable gas generated during the separation process.

[0104] One embodiment of this application also provides a hydrogen chloride tail gas separation and recovery system 10.

[0105] A hydrogen chloride tail gas separation and recovery system 10 includes a compression mechanism 100, an absorption tower, and a stripping tower 300 connected in sequence.

[0106] The compression mechanism 100 is used to compress hydrogen chloride tail gas to obtain high-pressure gas.

[0107] The absorption tower is used to absorb high-pressure gases by adding a circulating solvent and extract a liquid intermediate product including the circulating solvent, hydrogen chloride, and organic matter.

[0108] The stripping tower 300 is used to strip liquid intermediate products and extract hydrogen chloride and recycled solvent.

[0109] In some embodiments, the absorption tower, while absorbing high-pressure gas, can simultaneously extract a mixed gas comprising non-condensable gases and a small amount of hydrogen chloride. This mixed gas, after cooling, is sent to a non-condensable gas recovery system for further processing.

[0110] In some embodiments, the compression mechanism 100 includes a compressor employing a wet compression method.

[0111] In some embodiments, the absorber packing in the absorber tower includes Q-PAC (Q-ball Packing). Q-PAC packing is made of HAC material. Q-PAC packing offers significant advantages in terms of efficiency and pressure drop.

[0112] In some embodiments, the compression mechanism 100 includes a first-stage compression sub-mechanism and a second-stage compression sub-mechanism.

[0113] In some implementations, see Figure 2 As shown, there are multiple absorption towers. Multiple absorption towers 200a and 200b are connected in series.

[0114] In some implementations, see Figure 2 As shown, a circulating pump 400 is installed on the pipeline between absorption towers 200a and 200b and desorption tower 300.

[0115] In the aforementioned hydrogen chloride tail gas separation and recovery system 10, the raw material tail gas containing hydrogen chloride, organic matter, and other non-condensable gases is pressurized by the compression mechanism 100 and then enters the absorption towers 200a and 200b. A large amount of non-condensable gas and a small amount of hydrogen chloride are collected from the top of the absorption towers 200a and 200b. After depressurization, they can be sent to the non-condensable gas recovery system. The bottom of the absorption towers 200a and 200b collects a liquid intermediate product containing circulating solvent, hydrogen chloride, and a small amount of organic matter. The liquid intermediate product enters the desorption tower 300. The hydrogen chloride desorbed by heating is collected from the top of the desorption tower 300 and sent to the downstream process. The circulating solvent after desorption in the bottom of the desorption tower 300 can be returned to the upstream absorption towers 200a and 200b for reuse after cooling. At the same time, a small amount of circulating solvent is collected from the bottom of the desorption tower 300 and sent to the solvent purification system to remove organic impurities in the circulating solvent and prevent impurities from accumulating in the hydrogen chloride tail gas separation and recovery process. The aforementioned hydrogen chloride tail gas separation and recovery system 10 can directly purify hydrogen chloride containing non-condensable gases and organic impurities, reducing the amount of waste gas and by-product hydrochloric acid, while producing high-value-added high-purity hydrogen chloride products, realizing efficient recycling of chlorine resources in the chemical industrial park, and having significant economic and social benefits.

[0116] Example 1

[0117] This embodiment provides a method for separating and recovering hydrogen chloride tail gas. This method employs... Figure 1 The hydrogen chloride tail gas separation and recovery system 10 shown is illustrated.

[0118] Hydrogen chloride tail gas from a chemical industrial park was collected, containing 80 wt% hydrogen chloride. In this embodiment, the circulating solvent includes chlorobenzene and an auxiliary agent, with a mass ratio of 90:10 between chlorobenzene and the auxiliary agent. The auxiliary agent includes γ-alumina and Na2CO3 in a mass ratio of 1:1.

[0119] The hydrogen chloride tail gas separation and recovery method of this embodiment includes the following steps:

[0120] S10. Control the hydrogen chloride tail gas to enter the compression mechanism 100 for compression to obtain high pressure gas with a pressure of 0.9 MPaG.

[0121] S20. Control the high-pressure gas to enter the first absorption tower 200a, with a feed flow rate of approximately 300 kg / h. The first absorption tower 200a uses circulating solvent chlorobenzene for the first-stage absorption treatment of the high-pressure gas, with a chlorobenzene dosage of 0.6 t / h and a temperature control of -10℃. The exhaust gas is collected from the top of the first absorption tower 200a.

[0122] The exhaust gas is controlled to enter the second absorption tower 200b. The top of the second absorption tower 200b uses chlorobenzene, a circulating solvent, for the second-stage absorption treatment of the exhaust gas. The chlorobenzene dosage is 0.7t / h, and the temperature is controlled at -20℃.

[0123] The reflux intermediate product, which includes part of the recycled solvent, part of the hydrogen chloride and a small amount of organic matter, is collected from the bottom of the second absorption tower 200b and refluxed back to the first absorption tower 200a for recycling absorption. The mixed gas, which includes non-condensable gas and a small amount of hydrogen chloride, is collected from the top of the second absorption tower 200b and sent to the downstream processing unit.

[0124] After the first absorption tower 200a and the second absorption tower 200b are in equilibrium, the bottom of the first absorption tower 200a yields a liquid intermediate product containing recycled solvent, hydrogen chloride and a small amount of organic matter, and the concentration of hydrogen chloride in the liquid intermediate product is controlled to be 18 wt%.

[0125] S30. The liquid intermediate product is controlled to enter the stripping column 300. The temperature of the bottom of the stripping column 300 is controlled at 80℃, the temperature of the top is controlled at -39℃, and the stripping pressure is controlled at 6 bara. The stripping process is carried out, and hydrogen chloride gas is collected from the top of the column, while the circulating solvent is collected from the bottom. The circulating solvent collected from the bottom and the hydrogen chloride gas collected from the top of the column can exchange heat to recover heat and achieve cooling. After testing, the gas phase collected from the top of the stripping column 300 is product HCl with a purity of 99.3%, which is sent out as a high-quality hydrogen chloride product.

[0126] Example 2

[0127] This embodiment provides a method for separating and recovering hydrogen chloride tail gas. This method employs... Figure 1 The hydrogen chloride tail gas separation and recovery system 10 shown is illustrated.

[0128] Take hydrogen chloride tail gas from a chemical industrial park. The hydrogen chloride tail gas contains 83 wt% hydrogen chloride.

[0129] The hydrogen chloride tail gas separation and recovery method of this embodiment includes the following steps:

[0130] S10. Control the hydrogen chloride tail gas to be compressed to a pressure of 0.7 MPaG through the first stage compression sub-mechanism, and then compressed to a pressure of 1 MPaG through the second stage compression sub-mechanism. The hydrogen chloride tail gas is cooled to 25°C by circulating water between the first stage compression and the second stage compression.

[0131] S20. Control the high-pressure gas to enter the first absorption tower 200a, with a feed flow rate of approximately 300 kg / h. The first absorption tower 200a uses circulating solvent chlorobenzene for the first-stage absorption treatment of the high-pressure gas, with a chlorobenzene dosage of 0.7 t / h and a temperature control of -15℃. The exhaust gas is collected from the top of the first absorption tower 200a.

[0132] The exhaust gas is controlled to enter the second absorption tower 200b. The top of the second absorption tower 200b uses chlorobenzene, a circulating solvent, for the second-stage absorption treatment of the exhaust gas. The chlorobenzene dosage is 0.8t / h, and the temperature is controlled at -22℃.

[0133] The reflux intermediate product, which includes part of the recycled solvent, part of the hydrogen chloride and a small amount of organic matter, is collected from the bottom of the second absorption tower 200b and refluxed back to the first absorption tower 200a for recycling absorption. The mixed gas, which includes non-condensable gas and a small amount of hydrogen chloride, is collected from the top of the second absorption tower 200b and sent to the downstream processing unit.

[0134] After the first absorption tower 200a and the second absorption tower 200b are in equilibrium, the bottom of the first absorption tower 200a yields a liquid intermediate product containing recycled solvent, hydrogen chloride and a small amount of organic matter, and the concentration of hydrogen chloride in the liquid intermediate product is controlled to be 16 wt%.

[0135] S30. The liquid intermediate product is controlled to enter the stripping column 300. The temperature of the bottom of the stripping column 300 is controlled at 100℃, the temperature of the top is controlled at -39℃, and the stripping pressure is controlled at 8 bara. The stripping process is carried out, and hydrogen chloride gas is collected from the top of the column, while the circulating solvent is collected from the bottom. The circulating solvent collected from the bottom and the hydrogen chloride gas collected from the top of the column can exchange heat to recover heat and achieve cooling. After testing, the gaseous product collected from the top of the stripping column 300 is HCl with a purity of 99.4%, which is sent out as a high-quality hydrogen chloride product.

[0136] Furthermore, compared to Example 1, Example 2 can reduce energy consumption by 10% and lower operating costs.

[0137] Example 3

[0138] This embodiment provides a method for separating and recovering hydrogen chloride tail gas. This method employs... Figure 1 The hydrogen chloride tail gas separation and recovery system 10 shown is illustrated.

[0139] Take hydrogen chloride tail gas from a chemical industrial park. The hydrogen chloride tail gas contains 80 wt% hydrogen chloride.

[0140] The hydrogen chloride tail gas separation and recovery method of this embodiment includes the following steps:

[0141] S10. Control the hydrogen chloride tail gas to enter the compression mechanism 100 for compression to obtain high pressure gas with a pressure of 0.9 MPaG.

[0142] S20. Control the inflow of high-pressure gas into the absorption tower at a feed rate of approximately 300 kg / h. The high-pressure gas undergoes first-stage absorption treatment at the top of the absorption tower using circulating solvent chlorobenzene at a rate of 0.6 t / h, with the temperature controlled at -10℃. The top gas from the absorption tower, consisting of a mixture of non-condensable gases and a small amount of hydrogen chloride, is sent to the downstream processing unit. The bottom gas from the absorption tower is a liquid intermediate product containing the circulating solvent, hydrogen chloride, and a small amount of organic matter. The concentration of hydrogen chloride in the liquid intermediate product is controlled at 18 wt%.

[0143] S30. The liquid intermediate product is controlled to enter the stripping column 300. The temperature of the bottom of the stripping column 300 is controlled at 80℃, the temperature of the top is controlled at -39℃, and the stripping pressure is controlled at 6 bara. The stripping process is carried out, and hydrogen chloride gas is collected from the top of the column, while the circulating solvent is collected from the bottom. The circulating solvent collected from the bottom and the hydrogen chloride gas collected from the top of the column can exchange heat to recover heat and achieve cooling. After testing, the gaseous product collected from the top of the stripping column 300 is HCl with a purity of 99.21%, which is sent out as a high-quality hydrogen chloride product.

[0144] Furthermore, compared to Example 1, Example 3 reduces the solvent circulation volume by 10%, saving energy used for heating and cooling the circulating solvent, and achieving an overall energy saving of approximately 12%.

[0145] Comparative Example 1

[0146] This comparative example provides a method for separating and recovering hydrogen chloride tail gas, which is basically the same as that in Example 1, except that methanol is used as the circulating solvent in Comparative Example 3.

[0147] After testing, the gas phase extracted from the top of the analytical column 300 was found to be HCl with a purity of 98.5%.

[0148] Comparative Example 2

[0149] This comparative example provides a method for separating and recovering hydrogen chloride tail gas, which is basically the same as that in Example 1, except that the circulating solvent in Comparative Example 1 is ethyl acetate.

[0150] After testing, the gas phase extracted from the top of the analytical column 300 was found to be HCl with a purity of 98.2%.

[0151] Comparative Example 3

[0152] This comparative example provides a method for separating and recovering hydrogen chloride tail gas, which is basically the same as that in Example 1, except that the circulating solvent in Comparative Example 3 is diethyl ether.

[0153] After testing, the gas phase extracted from the top of the analytical column 300 was found to be HCl with a purity of 98%.

[0154] Comparative Example 4

[0155] This comparative example provides a method for separating and recovering hydrogen chloride tail gas, which is basically the same as that in Example 2, except that the circulating solvent chlorobenzene in Comparative Example 4 does not contain any additives.

[0156] After testing, the gas phase extracted from the top of the analytical column 300 was found to be HCl with a purity of 96%.

[0157] Comparative Example 5

[0158] This comparative example provides a method for separating and recovering hydrogen chloride tail gas. This method is basically the same as that in Example 2, except that the concentration of hydrogen chloride in the liquid intermediate product in Comparative Example 5 is controlled at 3 wt%, which means that the concentration of hydrogen chloride in the liquid intermediate product is too low.

[0159] After testing, the gas phase extracted from the top of the analytical column 300 was found to be HCl with a purity of 98%. In order to maintain the concentration of HCl at the top of the column, there is a drawback of increasing the amount of circulating solvent and wasting energy.

[0160] Comparative Example 6

[0161] This comparative example provides a method for separating and recovering hydrogen chloride tail gas. This method is basically the same as that in Example 2, except that the concentration of hydrogen chloride in the liquid intermediate product in Comparative Example 6 is controlled at 24 wt%, which means that the concentration of hydrogen chloride in the liquid intermediate product is too high.

[0162] Testing revealed that the vapor extracted from the top of the analytical column 300 was HCl with a purity of 98.2%, exceeding the equipment's pressure design limit and posing a safety risk.

[0163] Comparative Example 7

[0164] This comparative example provides a method for separating and recovering hydrogen chloride tail gas. This method is basically the same as that in Example 3, except that the desorption temperature in Comparative Example 7 is controlled at 50°C, which is too low.

[0165] After testing, the gas phase extracted from the top of the analytical column 300 was found to be HCl with a purity of 98.2%, which has the disadvantage of high HCl content in the bottom liquid.

[0166] Comparative Example 8

[0167] This comparative example provides a method for separating and recovering hydrogen chloride tail gas. This method is basically the same as that in Example 3, except that the desorption temperature in Comparative Example 8 is controlled at 140°C, which is too high.

[0168] Testing revealed that the vapor extracted from the top of the analytical column 300 was HCl with a purity of 98.2%. The increased reflux ratio resulted in energy waste.

[0169] In summary, compared with traditional technologies, the hydrogen chloride tail gas separation and recovery method of this application has at least the following beneficial effects:

[0170] (1) Hydrogen chloride in hydrogen chloride tail gas can be recovered and purified. The hydrogen chloride recovery rate is >95%, and the purity of hydrogen chloride is increased from 70%~80% in traditional technology to 99.9%, obtaining high-purity and high-quality hydrogen chloride. High-purity and high-quality hydrogen chloride can be sent to the external market, which reduces the amount of waste gas treatment in the chemical industrial park on the one hand, and also increases the added value of the product on the other hand.

[0171] (2) The separated nitrogen and other non-condensable gases can be reused in the upstream system or extracted for other processes, thereby improving resource utilization and reducing material and energy consumption.

[0172] (3) By designing a solvent distillation system downstream, the impurities absorbed in the solvent are removed, ensuring that the solvent can be repeatedly recycled, effectively controlling the solvent cost and also controlling the recycling cost.

[0173] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0174] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0175] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for separating and recovering hydrogen chloride tail gas, characterized in that, Includes the following steps: High-pressure gas is obtained by compressing hydrogen chloride tail gas; The high-pressure gas is absorbed and treated using a circulating solvent to extract a liquid intermediate product; wherein the circulating solvent includes one or more of chlorobenzene, methanol, ethyl acetate and diethyl ether, and the circulating solvent also includes an auxiliary agent, which includes γ-alumina and carbonates. Furthermore, the liquid intermediate product is subjected to analytical treatment to extract hydrogen chloride and recycled solvent.

2. The method for separating and recovering hydrogen chloride tail gas according to claim 1, characterized in that, The pressure of the compressed hydrogen chloride tail gas to obtain high-pressure gas is controlled at 0.5 MPaG~1.5 MPaG.

3. The method for separating and recovering hydrogen chloride tail gas according to claim 1, characterized in that, When compressing hydrogen chloride tail gas to obtain high-pressure gas, a staged compression method is used.

4. The method for separating and recovering hydrogen chloride tail gas according to claim 3, characterized in that, The staged compression method includes the following steps: controlling the hydrogen chloride tail gas to undergo a first-stage compression treatment, wherein the pressure during the first-stage compression treatment is controlled to be 0.5 MPaG~0.7 MPaG; The hydrogen chloride tail gas after the first stage compression process is cooled. Furthermore, the hydrogen chloride tail gas after cooling is subjected to a second-stage compression treatment, and the pressure during the second-stage compression treatment is controlled to be 0.7 MPaG~1.5 MPaG, wherein the pressure during the second-stage compression treatment is greater than the pressure during the first-stage compression treatment.

5. The method for separating and recovering hydrogen chloride tail gas according to claim 4, characterized in that, The cooling process is performed using a cooling medium.

6. The method for separating and recovering hydrogen chloride tail gas according to claim 1, characterized in that, When compressing hydrogen chloride tail gas to obtain high-pressure gas, a wet compression method is used.

7. The method for separating and recovering hydrogen chloride tail gas according to claim 6, characterized in that, The wet compression method includes the following steps: spraying an inert solvent onto the hydrogen chloride tail gas at the compression inlet, wherein the inert solvent includes one or more of chlorobenzene, toluene, and dimethyl carbonate.

8. The method for separating and recovering hydrogen chloride tail gas according to claim 1, characterized in that, The mass ratio between the chlorobenzene and the auxiliary is (80~90):(10~20), the carbonate includes one or two of alkali metal carbonates and alkaline earth metal carbonates, and the mass ratio between the γ-alumina and the carbonate is (40~60):(40~60).

9. The method for separating and recovering hydrogen chloride tail gas according to claim 1, characterized in that, When using a circulating solvent to absorb the high-pressure gas, the temperature of the circulating solvent is controlled to be -40℃ to 0℃.

10. The method for separating and recovering hydrogen chloride tail gas according to claim 9, characterized in that, When using a circulating solvent to absorb the high-pressure gas, the temperature of the circulating solvent is controlled to be -10℃ to -30℃.

11. The method for separating and recovering hydrogen chloride tail gas according to claim 1, characterized in that, The concentration of hydrogen chloride in the liquid intermediate is controlled to be 5wt%~20wt%.

12. The method for separating and recovering hydrogen chloride tail gas according to claim 11, characterized in that, The concentration of hydrogen chloride in the liquid intermediate is controlled to be 8 wt% to 16 wt%.

13. The method for separating and recovering hydrogen chloride tail gas according to any one of claims 1 to 12, characterized in that, When using a circulating solvent to absorb the high-pressure gas, a staged absorption method is employed.

14. The method for separating and recovering hydrogen chloride tail gas according to claim 13, characterized in that, The graded absorption includes the following steps: The high-pressure gas is subjected to a first-stage absorption treatment using a circulating solvent. The temperature of the first-stage absorption treatment is controlled at -15℃ to 0℃. The liquid intermediate product, which includes the circulating solvent, hydrogen chloride, and organic matter, as well as the exhaust gas, is collected. The exhaust gas is subjected to a second-stage absorption treatment using a circulating solvent. The temperature of the second-stage absorption treatment is controlled at -15℃ to -25℃, and a reflux intermediate product including the circulating solvent, hydrogen chloride, and organic matter is collected. In addition, the process of controlling the reflux intermediate product to be refluxed back to the first-stage absorption treatment for cyclic absorption.

15. The method for separating and recovering hydrogen chloride tail gas according to any one of claims 1 to 12, 14, characterized in that, When performing the analytical treatment on the liquid intermediate product, the analytical temperature is controlled to be 70℃~120℃.

16. The method for separating and recovering hydrogen chloride tail gas according to claim 15, characterized in that, When performing the analytical treatment on the liquid intermediate product, the analytical temperature is controlled at 75℃~100℃.

17. The method for separating and recovering hydrogen chloride tail gas according to any one of claims 1 to 12, 14, and 16, characterized in that, When performing the analytical treatment on the liquid intermediate product, the analytical pressure is controlled to be 6 bara to 10 bara.

18. The method for separating and recovering hydrogen chloride tail gas according to claim 17, characterized in that, When performing the analytical treatment on the liquid intermediate product, the analytical pressure is controlled at 7.5 bara to 8.5 bara.

19. The method for separating and recovering hydrogen chloride tail gas according to any one of claims 1 to 12, 14, 16, and 18, characterized in that, It also satisfies at least one of the following conditions: (1) It also includes the following steps: removing impurities from the collected circulating solvent using a solvent refining system; (2) It also includes the following steps: controlling the return of the extracted circulating solvent to the absorption treatment process; (3) It also includes the following steps: cooling the mixed gas containing non-condensable gas and hydrogen chloride after the high-pressure gas is absorbed and treated, and then transporting it to the non-condensable gas recovery system.

20. A hydrogen chloride tail gas separation and recovery system, characterized in that, The method for separating and recovering hydrogen chloride tail gas according to any one of claims 1 to 19 includes: A compression mechanism is used to compress hydrogen chloride tail gas to obtain high-pressure gas. An absorption tower is used to absorb the high-pressure gas by adding a circulating solvent and to extract the liquid intermediate product. And a stripping column, used to strip the liquid intermediate product and extract hydrogen chloride and recycled solvent.

21. The hydrogen chloride tail gas separation and recovery system according to claim 20, characterized in that, It also satisfies at least one of the following conditions: (1) The compression mechanism includes a compressor that uses a wet compression method; (2) The absorption packing in the absorption tower includes ball-type Parker packing; (3) The compression mechanism includes a first-stage compression sub-mechanism and a second-stage compression sub-mechanism; (4) There are multiple absorption towers, and the multiple absorption towers are connected in series.

Images