A hydrogen chloride recovery and purification system and process
Through low-temperature separation and low-temperature heat pump distillation technology, combined with a self-sealing air-floating rotor expander, efficient recovery and purification of hydrogen chloride is achieved, solving the problems of cold source dependence and safety risks in the existing process, and achieving high-purity and high-efficiency hydrogen chloride recovery.
Patent Information
- Application Number
- CN202310276096.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-03-20
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2043-03-20
AI Technical Summary
The existing hydrogen chloride recovery and purification process requires an external cooling source, occupies a large area, and has high safety risks when operating under negative pressure, making it difficult to meet the production needs of high-purity HCl.
The low-temperature separation process and low-temperature heat pump distillation technology are adopted. Through the combination of the main heat exchanger, distillation tower and tower top reboiler, the self-sealing air-floating rotor expander is used to provide cooling capacity to achieve pre-cooling, condensation, separation and purification of hydrogen chloride-rich raw gas, avoiding external cooling sources and reducing equipment footprint.
The recovery and purification of high-purity HCl is achieved, with product purity reaching 99.99% by volume and a product yield of no less than 90%. No external cooling source is required, and the equipment is compact, occupies a small area, and has low energy consumption.
Smart Images
Figure CN116251371B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a hydrogen chloride recovery and purification system and process, belonging to the technical field of chemical industry, in particular to the technical field of recovery and purification of hydrogen chloride. Background Art
[0002] Currently, the commonly used separation process for hydrogen chloride (HCl)-rich gas containing some propylene (C3H6) and propane (C3H8) usually adopts molecular sieve adsorption, membrane separation process and low-temperature separation. However, if high-purity HCl is to be obtained, it can only be obtained through low-temperature separation.
[0003] At present, the commonly used low-temperature separation process requires cold capacity supplementation, especially the cold capacity required for tower top condensation and the cold capacity supply for heat exchange balance. It often requires the use of external cold sources, such as the cold capacity generated by refrigeration processes such as propylene and ammonia as a cold source. However, there are large safety distance requirements when storing the above refrigerants. When the device occupies a limited area, the above process will encounter bottlenecks.
[0004] When the atmospheric pressure dew point of the above-mentioned refrigerant cannot meet the required low temperature, the above-mentioned refrigeration process is no longer applicable. If it is still hoped that the atmospheric pressure dew point of the above-mentioned refrigerant can meet the required low temperature requirement, it is necessary to operate the corresponding refrigeration process under negative pressure. However, compared with positive pressure operation, the safety risk of operation under negative pressure is often higher.
[0005] In addition, if the raw gas is reheated in the low-temperature separation system and then returned to the low-temperature system through part of the medium, it is often compressed at room temperature, which also requires a larger area.
[0006] Therefore, providing a new type of hydrogen chloride recovery and purification system and process has become a technical problem that needs to be solved urgently in this field. Summary of the Invention
[0007] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide a hydrogen chloride recovery and purification system.
[0008] Another object of the present invention is to provide a hydrogen chloride recovery and purification process. This invention utilizes a low-temperature separation process to precool, condense, separate, and purify hydrogen chloride-rich feed gas, ultimately yielding a qualified HCl product. This system and process can recover and purify HCl from hydrogen chloride-rich feed gas containing impurities such as C3H6 and C3H8.
[0009] In order to achieve the above objectives, in one aspect, the present invention provides a hydrogen chloride recovery and purification system, wherein the hydrogen chloride recovery and purification system comprises:
[0010] A hydrogen chloride-rich feed gas delivery pipeline, a main heat exchanger, and a distillation tower. The main heat exchanger includes at least one hot channel and at least one cold channel. The distillation tower includes, from top to bottom, a tower top, a tower body, and a tower kettle. The top of the tower top is sealed with a tower top condenser kettle, and the tower top condenser kettle has a built-in tower top reboiler. The tower body is provided with a feed gas inlet and a distributor inside.
[0011] The hydrogen chloride-rich feed gas delivery pipeline is connected to the feed gas inlet of the tower body via any hot channel in the main heat exchanger, so that the hydrogen chloride-rich feed gas enters any hot channel in the main heat exchanger through the pipeline, is cooled and partially liquefied, and then enters the distillation tower. The bottom liquid outlet of the tower kettle is connected to any cold channel inlet in the main heat exchanger via a pipeline, and the cold channel outlet is connected to the gas inlet of the upper space of the tower kettle via a pipeline.
[0012] The first gas outlet at the top of the tower is connected to the hot side channel inlet of the tower top reboiler through a pipeline, and the hot side channel outlet of the tower top reboiler is connected to the liquid inlet of the tower top through a pipeline, so as to condense part of the tower top gas and return the condensed liquid to the tower top to provide tower top reflux liquid for the distillation tower. The second gas outlet at the top of the tower is connected to another hot channel in the main heat exchanger through a pipeline via a compressor, and the outlet of the hot channel is connected to the cold side channel of the tower top reboiler through a pipeline via a first throttle valve, so that another part of the tower top gas enters another hot channel in the main heat exchanger through the pipeline via the compressor, and the outlet of the hot channel is connected to the cold side channel of the tower top reboiler through a pipeline via the first throttle valve to provide a cold source for it.
[0013] The hydrogen chloride gas outlet of the tower top condenser is connected to another cold channel inlet in the main heat exchanger through a pipeline via an expander.
[0014] In the present invention, the tower top reboiler is used to condense part of the tower top gas and return the condensed liquid to the tower top to provide tower top reflux liquid for the distillation tower.
[0015] In the present invention, the bottom reboiler of the distillation tower can be integrated with the main heat exchanger, that is, the bottom reboiler of the distillation tower only serves as a channel for the main heat exchanger. Of course, the present invention can also separately set the bottom reboiler and the main heat exchanger.
[0016] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification system of the present invention, wherein the system further includes a bottom reboiler, and the main heat exchanger includes a first hot channel and a first cold channel;
[0017] The hydrogen chloride-rich feed gas delivery pipeline is connected to the feed gas inlet of the tower body via the first hot channel in the main heat exchanger, so that the hydrogen chloride-rich feed gas enters the first hot channel through the pipeline, is cooled and partially liquefied, and then enters the distillation tower through the pipeline through the feed gas inlet. The bottom liquid outlet of the tower kettle is connected to the cold channel inlet of the tower bottom reboiler via a pipeline, and the cold channel outlet of the tower bottom reboiler is connected to the gas inlet of the upper space of the tower kettle via a pipeline.
[0018] The first gas outlet at the top of the tower is connected to the hot side channel inlet of the top reboiler through a pipeline, the hot side channel outlet of the top reboiler is connected to the liquid inlet of the top of the tower through a pipeline, the second gas outlet at the top of the tower is connected to the inlet of the hot channel of the bottom reboiler through a pipeline via a compressor, and the outlet of the hot channel of the bottom reboiler is connected to the cold side channel of the top reboiler through a pipeline via a first throttle valve;
[0019] The hydrogen chloride gas outlet of the tower top condenser is connected to the inlet of the first cold channel in the main heat exchanger through a pipeline via an expander.
[0020] The tower top reboiler used in the present invention is used to condense part of the tower top gas and return the condensed liquid to the tower top to provide tower top reflux liquid for the distillation tower, while another part of the tower top gas enters the hot channel of the tower bottom reboiler through a pipeline via a compressor, and the outlet of the hot channel of the tower bottom reboiler is connected to the cold side channel of the tower top reboiler through a pipeline via a first throttle valve to provide it with a cold source.
[0021] In a specific embodiment of the hydrogen chloride recovery and purification system described above, the overhead reboiler is a thermosyphon reboiler. The use of a thermosyphon reboiler facilitates integration, minimizing the size of the device and making it more compact while minimizing cooling losses.
[0022] In the present invention, when the tower top reboiler is a conventional reboiler, the first gas outlet at the tower top is connected to the hot side channel inlet of the tower top reboiler through a pipeline, the hot side channel outlet of the tower top reboiler is connected to the liquid inlet of the tower top through a pipeline, the second gas outlet at the tower top is connected to another hot channel in the main heat exchanger or the hot channel of the tower bottom reboiler through a pipeline via a compressor, and the outlet of the hot channel is connected to the cold side channel of the tower top reboiler through a pipeline via a first throttle valve;
[0023] When the top reboiler is a thermal siphon reboiler, the first gas outlet at the top of the tower is connected to the hot side channel inlet of the top reboiler through a pipeline, the hot side channel outlet of the top reboiler is connected to the liquid inlet of the top of the tower through a pipeline, and the outlet of another hot channel in the main heat exchanger or the hot channel of the bottom reboiler is connected to the top condenser kettle through a pipeline via a first throttle valve, so that the condensate discharged from the first throttle valve is stored in the top condenser kettle and provides a cold source for the thermal siphon reboiler.
[0024] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification system of the present invention, the bottom reboiler is a low-temperature plate-fin heat exchanger or a coiled-tube heat exchanger, preferably a low-temperature plate-fin heat exchanger.
[0025] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification system of the present invention, the main heat exchanger further includes an auxiliary cold channel, and the bottom liquid outlet of the tower kettle is further connected to the inlet of the auxiliary cold channel through a pipeline via a second throttle valve.
[0026] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification system of the present invention, the compressor is a cold compressor without a cooler.
[0027] As a specific embodiment of the hydrogen chloride recovery and purification system described above, the expander is a single-stage expander; preferably, it is a self-sealing air-floating rotor expander. More preferably, the shaft system of the self-sealing air-floating rotor expander is self-sealed using process gas HCl, which is safer and more reliable.
[0028] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification system of the present invention, the main heat exchanger and the tower top condenser are both low-temperature plate-fin heat exchangers or coil-wound heat exchangers, preferably low-temperature plate-fin heat exchangers.
[0029] On the other hand, the present invention also provides a hydrogen chloride recovery and purification process, wherein the hydrogen chloride recovery and purification process comprises:
[0030] The hydrogen chloride-rich feed gas is cooled to partially liquefy and then enters the distillation tower where it undergoes gas-liquid separation and distribution in the distributor. The gas gradually rises to the top of the tower while the liquid flows to the bottom of the tower.
[0031] The bottom liquid in the tower kettle is partially vaporized and returned to the upper space of the tower kettle to replenish the rising gas of the distillation tower. A part of the top gas is condensed and returned to the top of the tower to provide reflux liquid for the distillation tower. Another part of the top gas is pressurized and heated to provide a heat source for the partial vaporization of the bottom liquid. This part of the top gas is condensed to obtain a condensate, which is decompressed and cooled to provide a cold source for the condensation of a part of the top gas.
[0032] The liquid HCl in the condensate is heated by the gas at the top of the tower and then vaporized. The vaporized HCl is first expanded to cool down, and then heat-exchanged with the hydrogen chloride-rich feed gas before being discharged.
[0033] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification process of the present invention, the process further includes: reducing the pressure and cooling a portion of the tower bottom liquid, exchanging heat with the hydrogen chloride-rich feed gas, and then sending the reheated tower bottom liquid to a hydrocarbon recovery system for further recovery.
[0034] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification process of the present invention, the pressure of the hydrogen chloride-rich feed gas is 5-35 barA, preferably 8-30 barA, more preferably 8-15 barA, and the temperature is 0-40°C.
[0035] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification process of the present invention, the volume concentration of hydrogen chloride gas is not less than 70%, and the volume concentration of impurity gas is not more than 30%, based on the total volume of the hydrogen chloride-rich feed gas.
[0036] The hydrogen chloride-rich feed gas targeted by the present invention includes tail gas from epichlorohydrin reaction, tail gas from allyl chloride reaction, and industrial gas or tail gas with similar composition to the above tail gas. Among them, impurity gases other than hydrogen chloride in the hydrogen chloride-rich feed gas include C3H6 and C3H8.
[0037] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification process of the present invention, the hydrogen chloride-rich feed gas is cooled to partially liquefy the hydrogen chloride and other impurity gases therein to obtain a gas-liquid mixture, and then the gas-liquid mixture enters a distillation tower; wherein the cooling temperature is not lower than -35°C.
[0038] As a specific embodiment of the hydrogen chloride recovery and purification process of the present invention, another portion of the top gas is pressurized and heated (the saturation temperature of the gas is increased after compression in the compressor) to a temperature at least 2°C higher than that of the bottom liquid, and then used as a heat source for vaporizing the bottom liquid. In this case, stable heat exchange between the two is ensured.
[0039] As a specific embodiment of the hydrogen chloride recovery and purification process described above, the vaporized HCl is expanded and cooled in a self-sealed air-floating rotor expander. The expansion work of the vaporized HCl (cold gas) can provide cooling for the cold box or the entire system.
[0040] As a specific embodiment of the above-mentioned hydrogen chloride recovery and purification process of the present invention, the operating pressure of the distillation tower is 5-15 barA, preferably 8-10 barA, the operating temperature of the tower top is not lower than -40°C, and the operating temperature of the tower bottom is not lower than -30°C.
[0041] In the present invention, if HCl gas needs to be produced, the gas stream in the top condenser of the distillation tower, that is, the gas stream formed by heat exchange between the condensate after decompression and cooling and a portion of the tower top gas, can be directly expanded and cooled, and then heat exchanged with the hydrogen chloride-rich feed gas. After reheating, HCl gas can be obtained. When a small amount of liquid HCl is required as a by-product, the liquid stream in the top condenser of the distillation tower, that is, the condensate after decompression and cooling, can be directly extracted in small amounts and sent to corresponding liquid storage facilities for storage.
[0042] Compared with the prior art, the beneficial technical effects achieved by the present invention include:
[0043] The hydrogen chloride recovery and purification system and process provided by the present invention utilize a low-temperature separation process / low-temperature heat pump distillation process in a distillation tower to enrich HCl in the hydrogen chloride-rich feed gas in the top gas phase of the distillation tower. Impurity components such as C3H6 and C3H8 are directly enriched in the bottom liquid phase of the distillation tower. A portion of the top gas phase is pressurized and heated to serve as a heat source for a bottom reboiler. The condensed portion of the top gas phase is depressurized and cooled, then returned to a top condenser to provide a cold source for condensing a portion of the top gas in the top reboiler. Liquid HCl in the condensed portion of the top gas is heated by the top gas and then vaporized. The vaporized HCl is first expanded and cooled, and then heat-exchanged with the hydrogen chloride-rich feed gas before being discharged.
[0044] The hydrogen chloride recovery and purification system and process provided by the present invention can return impurities such as C3H6 and C3H8 contained in the hydrogen chloride-rich feed gas to the upstream olefin separation system for further separation and recovery. The purity of the resulting HCl product can reach as high as 99.99% by volume, and the product yield can be at least 90%.
[0045] Furthermore, the hydrogen chloride recovery and purification system and process provided by the present invention do not introduce refrigerants such as propylene and ammonia. Instead, the heat and cooling required at the top and bottom of the distillation tower are coupled in a design. Furthermore, during implementation, a self-sealed air-floating rotor expander is used to supplement the cooling required by the entire system, such as the cooling capacity of a compressor (specifically, a cold compressor). The entire cryogenic distillation system does not require external cooling and heating sources, and can achieve separation and purification of HCl components simply by matching the cold and hot streams of its own cryogenic distillation with a heat pump distillation method. Compared with other processes, this system offers advantages in terms of both energy consumption and floor space.
[0046] The hydrogen chloride recovery and purification system and process provided by the present invention can be used in newly built hydrogen chloride recovery plants, and can also be used in renovation projects of existing epichlorohydrin, allyl chloride and other plants to recover HCl products.
[0047] In summary, the hydrogen chloride recovery and purification system and process provided by the present invention require a small number of equipment, have a more compact cold box equipment, occupy a small area, have low energy consumption, have high HCl recovery efficiency and purity, have a simpler process, and are more stable in operation. BRIEF DESCRIPTION OF THE DRAWINGS
[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0049] Figure 1 This is a schematic structural diagram of the hydrogen chloride recovery and purification system provided in Example 1 of the present invention.
[0050] Description of main figures:
[0051] E100, main heat exchanger; 121, first hot aisle; 122, first cold aisle; 123, second cold aisle; C101, distillation tower; E102, bottom reboiler; 125, second hot aisle; 124, third cold aisle; V101, overhead condenser; E101, thermosyphon reboiler; K101, cold compressor; JT101, first throttle valve; JT102, second throttle valve; T101, self-sealing air-floating rotor expander;
[0052] 101-102, 105, 113, 109-110, 115-117, first pipeline-second pipeline, third pipeline, fourth pipeline, fifth pipeline-sixth pipeline, seventh pipeline-ninth pipeline;
[0053] 103, 114, 111-112, 106-108, first pipeline, second pipeline, third pipeline-fourth pipeline, fifth pipeline-seventh pipeline;
[0054] 104. Branch pipeline. DETAILED DESCRIPTION
[0055] It should be noted that the term "comprise" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or apparatus.
[0056] The "range" disclosed in the present invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e., any lower limit can be combined with any upper limit to form a range. For example, a range of 60-120 and 80-110 is listed for a particular parameter, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values listed are 1 and 2, and the maximum range values listed are 3, 4, and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.
[0057] In the present invention, unless otherwise specified, the numerical range "ab" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed in this invention, and "0-5" is merely an abbreviation for these numerical combinations.
[0058] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.
[0059] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.
[0060] In the present invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method comprising steps (a) and (b) indicates that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method further comprising step (c) indicates that step (c) may be added to the method in any order, for example, the method may comprise steps (a), (b) and (c), or may comprise steps (a), (c) and (b), or may comprise steps (c), (a) and (b), etc.
[0061] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the attached table, drawings and examples. The following embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.
[0062] Example 1
[0063] This embodiment provides a hydrogen chloride recovery and purification system, the structural diagram of which is shown in FIG. Figure 1 As shown, from Figure 1 It can be seen that the hydrogen chloride recovery and purification system includes:
[0064] A main heat exchanger E100, a distillation tower C101, and a bottom reboiler E102. The main heat exchanger E100 is provided with a first hot channel 121, a first cold channel 122, and a second cold channel 123 (corresponding to an auxiliary cold channel); the bottom reboiler E102 is provided with a second hot channel 125 and a third cold channel 124; the distillation tower C101 comprises, from top to bottom, a tower top, a tower body, and a tower bottom. A tower top condenser V101 is sealed on the upper part of the tower top, and a thermosyphon reboiler E101 is built in the tower top condenser V101. A raw gas inlet is provided on the tower body, and a distributor is provided therein.
[0065] The first pipeline 101, i.e., the hydrogen chloride-rich feed gas delivery pipeline, is connected to the inlet of the first hot channel 121 in the main heat exchanger E100. The outlet of the first hot channel 121 is connected to the feed gas inlet of the tower body via the second pipeline 102, so that the hydrogen chloride-rich feed gas enters the first hot channel 121 via the first pipeline 101, is cooled and partially liquefied, and then enters the distillation tower C101 via the second pipeline 102 through the feed gas inlet. The bottom liquid outlet of the tower reactor is connected to the inlet of the third cold channel 124 of the bottom reboiler E102 via the first pipeline 103 and the branch pipeline 104. The outlet of the third cold channel 124 of the bottom reboiler E102 is connected to the gas inlet of the upper space of the tower reactor via the third pipeline 105.
[0066] The first gas outlet at the top of the tower is connected to the hot side channel inlet of the thermosyphon reboiler E101 through the fourth pipeline 113, and the hot side channel outlet of the thermosyphon reboiler E101 is connected to the liquid inlet of the top of the tower through the second pipeline 114, so that part of the top gas enters the thermosyphon reboiler E101, is condensed and then returns to the top of the tower to provide top reflux liquid for the distillation tower C101; the second top gas outlet at the top of the tower is connected to the inlet of the cold compressor K101 through the fifth pipeline 109, and the outlet of the cold compressor K101 is connected to the inlet of the second hot channel 125 of the bottom reboiler E102 through the sixth pipeline 110, and the outlet of the second hot channel 125 is connected to the top condenser V101 through the third pipeline 111, the first throttle valve JT101, and the fourth pipeline 112, so as to provide a cold source for the built-in thermosyphon reboiler E101;
[0067] The hydrogen chloride gas outlet of the tower top condenser V101 is connected to the inlet of the first cold channel 122 through the seventh pipeline 115, the self-sealing air-floating rotor expander T101, and the eighth pipeline 116. The outlet of the first cold channel 122 is connected to the ninth pipeline 117.
[0068] The bottom liquid outlet of the tower kettle is also connected to the inlet of the second throttle valve JT102 through the first pipe 103, the branch pipe 104, and the fifth pipe 106. The outlet of the second throttle valve JT102 is connected to the inlet of the second cold channel 123 in the main heat exchanger E100 through the sixth pipe 107. The outlet of the second cold channel 123 is connected to the seventh pipe 108.
[0069] In this embodiment, the main heat exchanger E100, the tower bottom reboiler E102, and the tower top condenser V101 are all low-temperature plate-fin heat exchangers.
[0070] Example 2
[0071] This embodiment provides a hydrogen chloride recovery and purification system, wherein the hydrogen chloride recovery and purification system includes:
[0072] A hydrogen chloride-rich feed gas delivery pipeline, a main heat exchanger, and a distillation tower, wherein the main heat exchanger includes a first hot channel, a second hot channel, a first cold channel, a second cold channel, and a third cold channel (corresponding to an auxiliary cold channel). That is, compared to Example 1, this embodiment integrates a bottom reboiler into the main heat exchanger, wherein the second hot channel and the second cold channel in the main heat exchanger are equivalent to the hot channel and the cold channel in the bottom reboiler, respectively. The distillation tower includes, from top to bottom, a tower top, a tower body, and a tower kettle. The upper portion of the tower top is sealed with a tower top condenser kettle, and the tower top condenser kettle has a built-in thermosyphon reboiler. The tower body is provided with a feed gas inlet, and a distributor is provided therein.
[0073] A hydrogen chloride-rich feed gas delivery pipeline is connected to the inlet of the first hot channel in the main heat exchanger, and the outlet of the first hot channel is connected to the feed gas inlet of the tower body through a second pipeline, so that the hydrogen chloride-rich feed gas enters the first hot channel through the first pipeline, is cooled and partially liquefied, and then enters the distillation tower through the second pipeline and the feed gas inlet. The bottom liquid outlet of the tower reactor is connected to the inlet of the second cold channel in the main heat exchanger through a first pipeline and a branch pipeline. The outlet of the second cold channel in the main heat exchanger is connected to the gas inlet of the upper space of the tower reactor through a third pipeline.
[0074] The first gas outlet at the top of the tower is connected to the hot side channel inlet of the thermosyphon reboiler through a fourth pipeline, and the hot side channel outlet of the thermosyphon reboiler is connected to the liquid inlet of the top of the tower through a second pipeline, so that part of the top gas enters the thermosyphon reboiler and returns to the top of the tower after being condensed to provide top reflux liquid for the distillation tower; the second top gas outlet at the top of the tower is connected to the inlet of the cold compressor through a fifth pipeline, and the outlet of the cold compressor is connected to the inlet of the second hot channel of the bottom reboiler through a sixth pipeline, and the outlet of the second hot channel is connected to the top condenser through a third pipeline, a first throttle valve, and a fourth pipeline to provide a cold source for its built-in thermosyphon reboiler;
[0075] The hydrogen chloride gas outlet of the top condenser is connected to the inlet of the first cold channel in the main heat exchanger through the seventh pipeline, the self-sealing air-floating rotor expander, and the eighth pipeline. The outlet of the first cold channel in the main heat exchanger is connected to the ninth pipeline.
[0076] The bottom liquid outlet of the tower kettle is also connected to the inlet of the second throttle valve through the first pipe, the branch pipe, and the fifth pipe. The outlet of the second throttle valve is connected to the inlet of the third cold channel in the main heat exchanger through the sixth pipe. The outlet of the third cold channel in the main heat exchanger is connected to the seventh pipe.
[0077] In this embodiment, the main heat exchanger, the tower bottom reboiler, and the tower top condenser are all low-temperature plate-fin heat exchangers.
[0078] Example 3
[0079] This embodiment provides a hydrogen chloride recovery and purification process, which utilizes the hydrogen chloride recovery and purification system provided in Example 1. The process includes the following specific steps:
[0080] The tail gas from upstream epichlorohydrin and / or allyl chloride units is pretreated to obtain hydrogen chloride-rich feed gas. The hydrogen chloride-rich feed gas has a pressure of less than 15 barA, for example, 8-15 barA, and a temperature within the range of 0-40°C. The composition is as follows:
[0081] C3H6 1.628v%;
[0082] C3H8 1.250v%;
[0083] HCl 97.122v%;
[0084] The hydrogen chloride-rich feed gas enters the first hot channel 121 of the main heat exchanger E100 via the first pipeline 101, where it is cooled to a temperature of not less than -35°C, so that the hydrogen chloride, C3H6, and C3H8 gases therein are partially liquefied to form a gas-liquid mixture. The gas-liquid mixture then enters the middle portion (tower body) of the distillation tower C101 via the second pipeline 102. The gas-liquid mixture is subjected to gas-liquid separation and distribution in a distributor within the distillation tower C101. The gas gradually rises from the distributor to the top of the distillation tower as rising gas within the distillation tower C101, and the liquid gradually flows from the distributor to the bottom of the tower as descending liquid within the distillation tower C101. Mass and heat transfer are achieved during the contact between the rising and descending gas and liquid.
[0085] Part of the bottom liquid of the distillation tower C101 enters the third cold channel 124 of the bottom reboiler E102 through the first pipeline 103 and the branch pipeline 104. After being partially vaporized in the bottom reboiler E102, it returns to the upper space of the bottom of the distillation tower C101 through the third pipeline 105. The return flow from the bottom reboiler E102 contains both gas and liquid phases and needs to be separated in the upper space of the bottom to replenish the rising gas for the distillation tower C101. Another part of the bottom liquid enters the second throttle valve JT102 through the first pipeline 103, the branch pipeline 104, and the fifth pipeline 106. After being reduced in pressure and temperature, it enters the second cold channel 123 of the main heat exchanger E100 through the sixth pipeline 107 to exchange heat with the hydrogen chloride-rich feed gas. After being reheated, it is sent out of the boundary area through the seventh pipeline 108, such as to a hydrocarbon recovery system for further recovery.
[0086] A portion of the overhead gas from the distillation tower C101 enters the submerged thermosyphon reboiler E101 built into the tower top condenser V101 via the fourth pipeline 113, and after being condensed, returns to the tower top along the second pipeline 114, providing overhead reflux liquid for the distillation tower C101. Another portion of the overhead gas is led to the cold compressor K101 via the fifth pipeline 109. The temperature of the pressurized overhead gas is higher than the temperature of the tower bottom liquid (the temperature of the pressurized overhead gas is at least 2°C higher than the tower bottom liquid). The heated overhead gas enters the second hot channel 125 of the tower bottom reboiler E102 via the sixth pipeline 110, providing a reboil heat source for the tower bottom liquid. This portion of the overhead gas is condensed in the tower bottom reboiler to obtain a condensate, which enters the first throttle valve JT101 via the third pipeline 111. After being reduced in pressure and temperature, it enters the tower top condenser V101 along the fourth pipeline 112, providing a cold source for the condensation of a portion of the overhead gas in the thermosyphon reboiler E101.
[0087] In the thermosyphon reboiler E101, as part of the overhead gas condenses, the liquid HCl in the condensate is heated by the overhead gas and vaporized. The vaporized HCl gas (temperature is -35°C) enters the self-sealed air-floating rotor expander T101 along the seventh pipeline 115. After expansion and cooling, it enters the first cold channel 122 of the main heat exchanger E100 through the eighth pipeline 116. After reheating, it is sent out of the boundary area through the ninth pipeline 117, which is the hydrogen chloride gas product obtained after recovery and purification.
[0088] The material parameters in this embodiment are shown in Table 1 below.
[0089] Table 1
[0090]
[0091] In this embodiment, the operating pressure of the distillation tower is 7-9 barA, the operating temperature at the tower top is -40 to -35°C, and the operating temperature at the tower bottom is -30 to -27°C. Under these conditions, stable operation of the system is ensured. Combined with the material parameters shown in Table 1, in this embodiment, a HCl product with a purity of 99.99% by volume can be obtained at the tower top, and the HCl recovery rate is not less than 90%.
[0092] In summary, the hydrogen chloride recovery and purification system and process provided by the embodiments of the present invention adopt a low-temperature separation process / low-temperature heat pump distillation process in a distillation tower to enrich HCl in the hydrogen chloride-rich feed gas in the top gas phase of the distillation tower, and impurity components such as C3H6 and C3H8 are directly enriched in the bottom liquid phase of the distillation tower. A portion of the top gas phase is pressurized and heated and serves as a heat source for the bottom reboiler. The condensed portion of the top gas phase is depressurized and cooled and then returned to the top condenser to provide a cold source for condensing a portion of the top gas in the thermosiphon reboiler. The liquid HCl in the condensed portion of the top gas is heated by the top gas and then vaporized. The vaporized HCl is first expanded and cooled, and then discharged after heat exchange with the hydrogen chloride-rich feed gas.
[0093] The hydrogen chloride recovery and purification system and process provided by the embodiments of the present invention can return impurities such as C3H6 and C3H8 contained in the hydrogen chloride-rich feed gas to the upstream olefin separation system for further separation and recovery. The purity of the resulting HCl product can reach as high as 99.99% by volume, and the product yield can be at least 90%.
[0094] Furthermore, the hydrogen chloride recovery and purification system and process provided by the embodiments of the present invention do not introduce refrigerants such as propylene and ammonia. Instead, the heat and cooling required at the top and bottom of the distillation tower are coupled in a design. Furthermore, during implementation, a self-sealing air-floating rotor expander is used to supplement the cooling required by the entire system, such as the cooling capacity of a compressor (specifically, a cold compressor). The entire cryogenic distillation system does not require external cooling and heating sources, and can achieve HCl component separation and purification solely by matching the cold and hot streams of its own cryogenic distillation with a heat pump distillation method. Compared with other processes, this system offers advantages in terms of both energy consumption and floor space.
[0095] The hydrogen chloride recovery and purification system and process provided in the embodiments of the present invention can be used in newly built hydrogen chloride recovery plants, and can also be used in renovation projects of existing epichlorohydrin, allyl chloride and other plants to recover HCl products.
[0096] Therefore, the hydrogen chloride recovery and purification system and process provided by the embodiments of the present invention require less equipment, have a more compact cold box equipment, occupy a smaller area, have lower energy consumption, have high HCl recovery efficiency and purity, have a simpler process, and are more stable in operation.
[0097] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, substitutions of equivalent components, or equivalent changes and modifications made within the scope of patent protection, should still fall within the scope of this patent. Furthermore, the technical features of this invention may be freely combined with one another, with other technical inventions, and with other technical inventions.
Claims
1. A hydrogen chloride recovery and purification system, characterized in that: The hydrogen chloride recovery and purification system comprises: a hydrogen chloride-rich feed gas delivery pipeline, a main heat exchanger, and a distillation tower. The main heat exchanger comprises at least one hot channel and at least one cold channel. The distillation tower comprises, from top to bottom, a tower top, a tower body, and a tower bottom. A tower top condenser is sealed above the tower top, and a tower top condenser is built into the tower top reboiler. A feed gas inlet is provided in the tower body, and a distributor is disposed therein. The hydrogen chloride-rich raw gas delivery pipeline is connected to the raw gas inlet of the tower body via any hot channel in the main heat exchanger, the bottom liquid outlet of the tower kettle is connected to any cold channel inlet in the main heat exchanger via a pipeline, and the cold channel outlet is connected to the gas inlet of the upper space of the tower kettle via a pipeline; The first gas outlet at the top of the tower is connected to the hot side channel inlet of the tower top reboiler through a pipeline, the hot side channel outlet of the tower top reboiler is connected to the liquid inlet of the tower top through a pipeline, the second gas outlet at the top of the tower is connected to another hot channel in the main heat exchanger through a pipeline via a compressor, and the outlet of the hot channel is connected to the cold side channel of the tower top reboiler through a pipeline via a first throttle valve; The hydrogen chloride gas outlet of the tower top condenser is connected to another cold channel inlet in the main heat exchanger through a pipeline via an expander; The system further comprises a bottom reboiler, and the main heat exchanger comprises a first hot channel and a first cold channel; The hydrogen chloride-rich feed gas delivery pipeline is connected to the feed gas inlet of the tower body via the first hot channel in the main heat exchanger, the bottom liquid outlet of the tower kettle is connected to the cold channel inlet of the tower bottom reboiler via a pipeline, and the cold channel outlet of the tower bottom reboiler is connected to the gas inlet of the upper space of the tower kettle via a pipeline; The first gas outlet at the top of the tower is connected to the hot side channel inlet of the top reboiler through a pipeline, the hot side channel outlet of the top reboiler is connected to the liquid inlet of the top of the tower through a pipeline, the second gas outlet at the top of the tower is connected to the inlet of the hot channel of the bottom reboiler through a pipeline via a compressor, and the outlet of the hot channel of the bottom reboiler is connected to the cold side channel of the top reboiler through a pipeline via a first throttle valve; The hydrogen chloride gas outlet of the tower top condenser is connected to the inlet of the first cold channel in the main heat exchanger through a pipeline via an expander.
2. The hydrogen chloride recovery and purification system according to claim 1, characterized in that: The tower top reboiler is a thermosyphon reboiler.
3. The hydrogen chloride recovery and purification system according to claim 1, characterized in that: The tower bottom reboiler is a low-temperature plate-fin heat exchanger or a coiled tube heat exchanger.
4. The hydrogen chloride recovery and purification system according to claim 3, characterized in that: The tower bottom reboiler is a low-temperature plate-fin heat exchanger.
5. The hydrogen chloride recovery and purification system according to any one of claims 1 to 4, characterized in that: The main heat exchanger further includes an auxiliary cold channel, and the bottom liquid outlet of the tower kettle is further connected to the inlet of the auxiliary cold channel via a pipeline and a second throttle valve.
6. The hydrogen chloride recovery and purification system according to any one of claims 1 to 4, characterized in that: The compressor is a cold compressor.
7. The hydrogen chloride recovery and purification system according to any one of claims 1 to 4, characterized in that: The expander is a single-stage expander; The main heat exchanger and the tower top condenser are both low-temperature plate-fin heat exchangers or coiled-tube heat exchangers.
8. The hydrogen chloride recovery and purification system according to claim 7, characterized in that: The expander is a self-sealing air-floating rotor expander.
9. The hydrogen chloride recovery and purification system according to claim 7, characterized in that: The main heat exchanger and the tower top condenser are both low-temperature plate-fin heat exchangers.
10. A hydrogen chloride recovery and purification process, characterized in that: The hydrogen chloride recovery and purification process is implemented using the hydrogen chloride recovery and purification system according to any one of claims 1 to 9, which comprises: The hydrogen chloride-rich feed gas is cooled to partially liquefy the hydrogen chloride and other impurity gases therein to obtain a gas-liquid mixture, which is then passed into a distillation tower and subjected to gas-liquid separation and distribution in a distributor, with the gas gradually rising to the top of the tower and the liquid flowing to the bottom of the tower; wherein the cooling temperature is not less than -35°C; The bottom liquid in the tower kettle is partially vaporized and returned to the upper space of the tower kettle to replenish the rising gas of the distillation tower. A part of the top gas is condensed and returned to the top of the tower to provide reflux liquid for the distillation tower. Another part of the top gas is pressurized and heated to a temperature more than 2°C higher than the bottom liquid and used as a heat source for vaporizing the bottom liquid. This part of the top gas is condensed to obtain condensate, which is decompressed and cooled to provide a cold source for condensing part of the top gas. The liquid HCl in the condensate is heated by the overhead gas and then vaporized. The vaporized HCl is first cooled by expansion and then heat-exchanged with the hydrogen chloride-rich feed gas before being discharged. The process further includes: reducing the pressure and cooling a portion of the tower bottom liquid, exchanging heat with the hydrogen chloride-rich feed gas, and then sending the reheated tower bottom liquid to a hydrocarbon recovery system for further recovery.
11. The hydrogen chloride recovery and purification process according to claim 10, characterized in that: The pressure of the hydrogen chloride-rich raw gas is 5-35 barA and the temperature is 0-40°C; Based on the total volume of the hydrogen chloride-rich feed gas, the volume concentration of the hydrogen chloride gas is not less than 70%, and the volume concentration of the impurity gas is not more than 30%.
12. The hydrogen chloride recovery and purification process according to claim 11, characterized in that: The pressure of the hydrogen chloride-rich raw gas is 8-30 barA.
13. The hydrogen chloride recovery and purification process according to claim 12, characterized in that: The pressure of the hydrogen chloride-rich feed gas is 8-15 barA.
14. The hydrogen chloride recovery and purification process according to claim 10, characterized in that: The operating pressure of the distillation tower is 5-15 barA, the operating temperature of the tower top is not lower than -40°C, and the operating temperature of the tower bottom is not lower than -30°C.
15. The hydrogen chloride recovery and purification process according to claim 14, characterized in that: The operating pressure of the distillation tower is 8-10 barA.