High-pressure desorption of hydrogen chloride gas

Abstract

The present invention relates to a method for producing hydrogen chloride, comprising feeding pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or more into a high-pressure desorber (10), and heating the high-pressure desorber (10) at a temperature T of 110 to 200°C at the bottom of the high-pressure desorber at a pressure P of 2 bar or more. des The hydrogen chloride is desorbed in the high pressure desorber (10).

Description

Technical Field

[0001] The present invention relates to a method and unit for producing hydrogen chloride (HCl), and a component set for constructing the unit of the present invention.

Background Art

[0002] In many processes, HCl gas and hydrochloric acid containing various types and amounts of impurities are generated as by-products and waste streams. Various treatment technologies have been developed to recover HCl from such by-products and waste streams.

[0003] Patent Document 1 describes a method for recovering HCl from hydrochloric acid contaminated with salts of aluminum and other metals. Such (waste) liquids can be formed when treating certain ores with HCl. According to Patent Document 1, the contaminated hydrochloric acid is vaporized and the HCl-containing vapor is fed to a pressure swing distillation column. The product at the top of the column operating at high pressure is rich in HCl and can contain more than 90% HCl and is pure enough to be recycled (recirculated) in upstream and treatment processes.

[0004] In Patent Document 2, attempts have been made to obtain hydrogen chloride gas containing more than 99% by weight of hydrogen chloride or less than 0.03% by weight of water from an aqueous hydrochloric acid solution. For this purpose, Patent Document 2 discloses feeding an aqueous hydrochloric acid solution containing more HCl than the azeotropic mixture of HCl and water to the upper part of a column and feeding a hot hygroscopic salt solution to the middle part of the column. The effluent vapor containing HCl and moisture exits from the top of the column. Further, Patent Document 2 teaches reducing the moisture content of the HCl effluent vapor to less than 0.03% by weight by passing the vapor through a water-cooled condenser, a refrigerated aftercooler, and finally a mist separator.

[0005] The hydrochloric acid concentration method described in Patent Document 3 involves extractive distillation of an aqueous hydrogen chloride solution of a raw material in the presence of an extractant (for example, sulfuric acid, magnesium chloride and / or calcium chloride) in a distillation apparatus, and recovering hydrogen chloride vapor and / or hydrogen chloride gas from the upper part of the distillation apparatus. Patent Document 3 describes that water can be removed from the hydrogen chloride gas obtained from the upper part of the distillation apparatus by condensation.

[0006] The HCl obtained from such a process is not necessarily sufficiently pure and is not in the physical state (high-density state, for example, compressed state or even liquefied state) desired for delivery for particularly demanding applications. Such particularly demanding applications include semiconductor manufacturing, in which case "electronic grade HCl" is used as an etching gas, a cleaning gas, or a film-forming gas.

[0007] Various attempts have been made to provide HCl with the purity and physical state (high-pressure state, liquefied state) desired for such applications. For example, Patent Document 4 and Patent Document 5 teach two completely different methods for forming such HCl. Both methods involve, in addition to upstream processing steps, forming liquefied (liquefied) HCl by compression with a compressor. In particular, Patent Document 5 describes compressing and liquefying anhydrous crude hydrogen chloride at a pressure of 2.6 MPa (absolute pressure) or more, for example, at approximately 0°C. According to the methods described in Patent Document 4 and Patent Document 5, the liquefied HCl must be further purified by distillation. Patent Document 5 teaches that a rectification apparatus (distillation column) such as a tray column or a packed column is preferably used for distillation.

[0008] It is not possible to make a compressor solely from materials that are not corroded by HCl (graphite-based). Therefore, the HCl gas compressed within the compressor is always contaminated to some extent by the metal of the compressor and other non-HCl-resistant materials. HCl extracts these metals and other non-HCl-resistant materials from the compressor. Compressors used for compressing HCl require a lot of maintenance because HCl corrodes the compressor. In this regard, methods involving significant HCl gas compression, such as those described in Patent Documents 4 and 5, have drawbacks, and some of the purification achieved in the rectification unit requires removing contaminants from the upstream compressor. Furthermore, there is little room for improving the compressor to enhance HCl stability and reduce the need for maintenance.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0010] The problem of the present invention is to provide a reliable and efficient method and unit for producing hydrogen chloride with minimal risk of contamination for demanding applications (such as electronic grade HCl, etc.).

Means for Solving the Problems

[0011] This problem is solved by a method for producing hydrogen chloride in which pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or more is supplied into a high-pressure desorption device, and the high-pressure desorption device is operated at a pressure P of 2 bar or more at a temperature T of 100 to 200 °C at the bottom of the high-pressure desorption device to desorb hydrogen chloride in the high-pressure desorption device. des It is solved by a method for producing hydrogen chloride.

[0012] According to the present invention, the desorbed hydrogen chloride is automatically obtained at the high pressure P des and contains no (non-volatile) contaminants due to the compression of HCl in the compressor. Therefore, compression downstream of the hydrogen chloride can be partially or completely avoided. The initial compression stage, i.e., the compression stage due to a larger initial HCl gas volume than the downstream compression stage, can be completely avoided. With fewer compression stages, the hydrogen chloride becomes purer compared to hydrogen chloride that is only compressed by a compressor. Since this method can be carried out at a relatively low temperature, particularly using corrosion-stable materials, the hydrogen chloride produced according to the method of the present invention is pure. For example, the introduction of metal contaminants is necessarily lower than in methods involving more HCl gas compression.

[0013] Instead of increasing the pressure of hydrogen chloride by compression in a compressor, the pressure can be increased in highly concentrated hydrochloric acid, which is a liquid, using a pump (e.g., a centrifugal pump), thereby improving reliability and efficiency. The hydrochloric acid pump is much more reliable than a hydrogen chloride gas compressor and is highly efficient because at least partially avoiding frequent maintenance of the fragile HCl gas compressor.

[0014] Since hydrogen chloride is desorbed in the high-pressure desorption device, the hydrogen chloride produced according to the present invention is a gas when it exits the high-pressure desorption device. This gas may contain droplets of entrained liquid. The hydrogen chloride gas can be converted, for example, into liquid hydrogen chloride after exiting the high-pressure desorption device. However, depending on the customer's requirements and the specific process carried out at the customer's site, the hydrogen chloride is often kept in a gaseous state and supplied to a process that consumes hydrogen chloride gas. According to the present invention, P desIt is widely adaptable according to the compression of hydrogen chloride desired by the customer. The present invention is not limited with respect to the phase of the hydrogen chloride produced, and the invention of the present disclosure refers to the "method for producing hydrogen chloride" without restricting the present invention with respect to the phase (gas phase, liquid phase, solid phase) of hydrogen chloride.

[0015] According to the present invention, the pressurized highly concentrated hydrochloric acid supplied to the high-pressure desorption device has a hydrogen chloride concentration of 35% by weight or more. This means that 100 grams of hydrochloric acid contains 35 grams or more of HCl. As can be understood from FIGS. 3A and 3B below, such highly concentrated hydrochloric acid has a low boiling point at high pressure. This promotes the desorption of HCl. The highly concentrated hydrochloric acid has, for example, a hydrogen chloride concentration of 40 to 60% by weight. This enables operation at low temperatures and avoids equipment problems. Since the temperature inside the device does not approach a dangerous temperature (around 200°C in the case of resin-impregnated graphite equipment), the life of the corrosion-stable (graphite-based) equipment inside the high-pressure desorption device is extended. The use of such a hydrogen chloride concentration leads to a long equipment life, a reliable equipment design, and less downtime for the unit including the high-pressure desorption device. Preferably, the highly concentrated hydrochloric acid has a hydrogen chloride concentration of 40 to 58% by weight, more preferably 40 to 56% by weight, and most preferably 40 to 55% by weight.

[0016] Any pressure P of 2 bar or more des is suitable for the present invention because it necessarily results in a pressurized desorbed hydrogen chloride product that is denser and occupies less volume than the unpressurized hydrogen chloride product. P des can be 3 bar or more, preferably 4 bar or more, for example, 5 bar or more. Such a high P des suggests that desorbed hydrogen chloride having approximately the same pressure is produced by the high-pressure desorption device. Such a high P des The operation at P is an elegant method of providing HCl at the high pressure required at the manufacturing site with little or no downstream compression required. Compressors for HCl gas frequently fail and some require significant maintenance, but this can be avoided by the present invention. P descan be, for example, in the range of 6 to 20 bar, preferably in the range of 6 to 15 bar, and most preferably in the range of 6 to 13 bar. Particularly preferred pressure P des is 10 bar.

[0017] All pressures described in this application are absolute pressures.

[0018] According to the present invention, the desorption device operates at a temperature T of 110 to 200 °C at the bottom of the high-pressure desorption device. Within this temperature range, it is possible to actually desorb hydrogen chloride from highly concentrated hydrochloric acid supplied into the high-pressure desorption device. As is obvious to those skilled in the art, highly concentrated hydrochloric acid is very HCl-rich, and when the high-pressure desorption device operates at low pressure, a low temperature of only 110 °C or slightly above 110 °C is sufficient. When the highly concentrated hydrochloric acid is not so HCl-rich and the high-pressure desorption device operates at a higher pressure, a high temperature of 200 °C or slightly below 200 °C is preferably selected. The temperature T is preferably in the range of 120 to 175 °C, for example, in the range of 120 to 165 °C. This brings about a long service life and good reliability of corrosion-stable equipment. As a result, many downtime periods for maintenance of the high-pressure desorption device can be avoided, and the overall reliability and efficiency of the method of the present invention can be further improved.

[0019] The above method can be implemented at any site where pressurized highly concentrated hydrochloric acid is available as defined in this application.

[0020] At many sites, such pressurized highly concentrated hydrochloric acid is not available. Therefore, the present invention includes an optional upstream treatment technique for forming pressurized highly concentrated hydrochloric acid from low-concentrated hydrochloric acid that is generated at various sites but cannot be discharged from that site for environmental protection reasons.

[0021] At least a part of the highly concentrated hydrochloric acid can be formed in an absorption device, in which a hydrogen chloride-containing gas is absorbed into the low-concentration hydrochloric acid. This enables the operation of the high-pressure desorption device of the present disclosure at any site where a hydrogen chloride-containing gas (e.g., waste gas) that is overall sufficiently HCl-rich and hydrochloric acid are available, for making the hydrochloric acid have an HCl concentration of 35% by weight or more.

[0022] Typically, the absorption device operates at a pressure P des lower than pressure P abs . P abs can be in the range of 1 to 10 bar, for example, 2.5 to 7.5 bar. The pressure P des is, for example, 1 bar or more higher than P abs , preferably 1.5 bar or more higher, most preferably 2 bar or more higher, for example 2.5 bar or more higher. The pressure P des is, in particular, 1 to 15 bar higher than P abs , preferably 1.5 to 13 bar higher, most preferably 2 to 11 bar higher, for example 2.5 bar to 10 bar higher.

[0023] In many sites, only the (liquid) hydrochloric acid (waste) stream is available and needs to be treated, while the hydrogen chloride-containing gas is not available. To make the present invention applicable to such sites, a preferred method of the present invention includes the generation of such a hydrogen chloride-containing gas. Therefore, in a preferred method of the present invention, at least a part of the hydrogen chloride-containing gas to be absorbed into the low-concentration hydrochloric acid is formed in a low-pressure desorption device.

[0024] The term "low" in the "low-pressure desorption device" is used to clarify that this desorption device operates at a pressure lower than that of the high-pressure desorption device. The pressure in the low-pressure desorption device is typically slightly higher than the pressure in the absorption device, and no compressor is required to direct the hydrogen chloride-containing gas from the low-pressure desorption device into the absorption device.

[0025] The low-pressure stripping device can be supplied with hydrochloric acid at a sufficient concentration. According to a preferred method of the present invention, at least a part of the liquid obtained at the bottom of the high-pressure stripping device is recycled (recirculated) into the low-pressure stripping device. The HCl concentration of the liquid obtained at the bottom of the high-pressure stripping device is high enough to strip a hydrogen chloride-containing gas at a sufficient concentration at the low pressure inside the low-pressure stripping device, and is well-suited to concentrate a common hydrochloric acid (waste) stream available at many sites in an absorber.

[0026] The present invention also relates to a unit for producing hydrogen chloride, which unit comprises the following two: A high-pressure stripping device for stripping hydrogen chloride from pressurized highly concentrated hydrochloric acid. The high-pressure stripping device comprises a high-pressure inlet for supplying pressurized highly concentrated hydrochloric acid into the high-pressure stripping device, an upper high-pressure outlet for hydrogen chloride that can be stripped inside the high-pressure stripping device, and a lower high-pressure outlet for the liquid that can be obtained at the bottom of the high-pressure stripping device; and, A sub-unit connected to the high-pressure inlet and the lower high-pressure outlet and configured to be able to regenerate at least a part of the pressurized highly concentrated hydrochloric acid supplied through the high-pressure inlet from at least a part of the liquid that can be obtained through the lower high-pressure outlet. All the processing equipment shown on the left side of the high-pressure stripping device in Figure 2 is an example of such a sub-unit. However, any other processing equipment connected to the high-pressure inlet and the lower high-pressure outlet and configured to be able to regenerate at least a part of the pressurized highly concentrated hydrochloric acid supplied through the high-pressure inlet from at least a part of the liquid that can be obtained through the lower high-pressure outlet is a suitable sub-unit.

[0027] According to the present invention, the high-pressure stripping device can preferably operate at a pressure that is 5 bar or more higher than the ambient atmospheric pressure, more preferably 6 bar or more higher, for example 7 bar or more higher.

[0028] The high-pressure stripping device is preferably a high-pressure stripping column.

[0029] The internal structure of the high-pressure desorption device is typically corrosion-resistant to pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or more at a temperature of 110°C. Those skilled in the art will understand that such corrosion resistance can be achieved, for example, by using a graphite or carbon internal structure column (column) lined (lined) with PTFE sold under the name Polyfluoron (registered trademark) by SGL. Also, in the case of a particularly small pilot plant (test facility), a tantalum column (column) or a column (column) lined (lined) with tantalum can also be used.

[0030] Preferred units and methods of the present invention include a pump configured to supply highly concentrated hydrochloric acid against a high back pressure from a high-pressure desorption device under a pressure of 2 bar or more, particularly 6 bar or more, within the high-pressure desorption device. The pump is typically a corrosion-resistant centrifugal pump and supplies highly concentrated hydrochloric acid into the high-pressure desorption device. The pump replaces the first or a plurality of stages of the downstream hydrogen chloride compression unit. This is advantageous because the pump is much smaller and requires less maintenance than a compressor. This contributes to high process efficiency because many downtime periods of the units of the present invention can be avoided. Certain units of the present invention do not include a compressor for compressing the HCl-containing gas. Certain methods of the present invention do not include the compression of the HCl-containing gas. Particularly preferred units and methods of the present invention do not include a compressor to maintain a high pressure P of 2 bar or more, preferably 6 bar or more, within the high-pressure desorption device. des for this purpose.

[0031] Furthermore, the present invention relates to a hydrogen chloride supply unit comprising a high-pressure desorption device for desorbing hydrogen chloride from pressurized highly concentrated hydrochloric acid, the high-pressure desorption device comprising a high-pressure inlet for supplying pressurized highly concentrated hydrochloric acid into the high-pressure desorption device, an upper high-pressure outlet for hydrogen chloride that can be desorbed within the high-pressure desorption device, and a lower high-pressure outlet for the liquid that can be obtained at the bottom of the high-pressure desorption device, and the hydrogen chloride supply unit further comprising a hydrogen chloride filling device connected to the upper high-pressure outlet.

[0032] The term "hydrogen chloride filling device" includes any device configured to be able to separate a (continuous) hydrogen chloride fluid stream (which can be in liquid or gaseous state) into a spatially separated predetermined amount of hydrogen chloride fluid (such as various grades of liquefied hydrogen chloride gas supplied by various suppliers such as BOC, Linde, Praxair, etc.) that can be filled into a suitable tube trailer, ton container, or cylinder.

[0033] The hydrogen chloride filling device can be connected, for example, to an upper high-pressure outlet such that the hydrogen chloride passing through the high-pressure outlet is directed towards a high-pressure condenser, from the high-pressure condenser towards a high-pressure demister, and from the high-pressure demister towards the hydrogen chloride filling device. P des If it is high, even liquefied hydrogen chloride can be obtained by cooling (and condensing), that is, the labor of compressing hydrogen chloride gas is reduced. The hydrogen chloride filling device can be connected, for example, to an upper high-pressure outlet such that the hydrogen chloride passing through the high-pressure outlet is directed towards a hydrogen chloride cleaning and liquefaction unit, and from the hydrogen chloride cleaning and liquefaction unit towards the hydrogen chloride filling device. Any unit that reduces the impurity content in hydrogen chloride is regarded as a hydrogen chloride cleaning unit. Appropriate equipment for such a hydrogen chloride cleaning and liquefaction unit is obvious to those skilled in the art and is described, for example, in Patent Document 4 and Patent Document 5. Those skilled in the art can design the hydrogen chloride cleaning unit such that the hydrogen chloride filled into the filling device meets the specifications desired by the customer.

[0034] The present invention also relates to a set of parts for constructing the unit of the present invention, and the set of parts includes a high-pressure desorption device for desorbing hydrogen chloride gas from pressurized highly concentrated hydrochloric acid, and the desorption device a high-pressure inlet for supplying pressurized highly concentrated hydrochloric acid into the high-pressure desorption device, an upper high-pressure outlet for the hydrogen chloride gas that can be desorbed within the high-pressure desorption device, a lower high-pressure outlet for the liquid that can be obtained at the bottom of the high-pressure separation device, The component set further includes an absorption device having an outlet for highly concentrated hydrochloric acid, The component set is designed such that the outlet for highly concentrated hydrochloric acid is connected via a pump to the high-pressure inlet to pressurize the highly concentrated hydrochloric acid from the upper high-pressure outlet and supply it into the high-pressure separation device through the high-pressure inlet.

[0035] The component set may further include a low-pressure separation device having an inlet for the liquid. Preferably, the component set is designed such that the inlet for the liquid is connected to the lower high-pressure outlet to recycle at least a portion of the liquid obtained at the bottom of the high-pressure separation device into the low-pressure separation device through the inlet for the liquid.

[0036] (a) The method for producing hydrogen chloride according to the present invention, (b) the unit for producing hydrogen chloride according to the present invention, (c) the hydrogen chloride supply unit according to the present invention, and (d) all features described in the present application regarding the component set of the present invention are not limited thereto. Features described with respect to any of (a), (b), (c), and (d) may be features of the others among (a), (b), (c), and (d).

[0037] The present invention is illustrated with respect to the drawings described below. The drawings are for illustrative purposes only and do not limit the scope of the claims.

Brief Description of the Drawings

[0038]

Figure 1

Figure 2

Figure 3A

Figure 3B

Best Mode for Carrying Out the Invention

[0039] The high-pressure desorption device 10 shown in FIG. 1 is a high-pressure desorption column (column) lined with PTFE, and includes a high-pressure inlet 13 for supplying highly concentrated hydrochloric acid pressurized in the device 10, a lower high-pressure outlet 14 for the liquid that can be obtained at the bottom of the device 10, and an upper high-pressure outlet 15 for the hydrogen chloride gas that can be desorbed in the device 10. The bottom is heated by a high-pressure reboiler 11. The water contained in the desorbed hydrogen chloride gas exits the device through the outlet 15 and is condensed in the high-pressure condenser 12. The cooled hydrogen chloride gas exits the condenser 12 through line 18, and the condensed liquid is recycled into the device 10. Although not all details are shown, FIG. 1 shows that the desorption device may include a column internal structure 16 (for example, made of CFRC or CFRP, and of the Sigrabond (registered trademark) chemical product line manufactured by SGL) and a liquid distributor 19. Also, FIG. 1 is simplified and does not show the means for imparting high pressure and corrosion stability to the column. Even when highly concentrated hydrochloric acid, which is extremely corrosive and pressurized, is supplied into the column through the inlet 13, the column can operate for a long time at a high bottom temperature T of 110 to 200 °C and a high pressure P of up to 20 bar. des Therefore, it is possible to fully implement the method of the present invention in a device as shown in FIG. 1.

[0040] FIG. 2 shows the high-pressure desorption device 10 (such as that shown in FIG. 1) as a component of the unit according to the present invention. This unit further includes an absorption device 20 and a low-pressure desorption device 30.

[0041] The absorption device 20 includes a supply port 21 for low-concentration hydrochloric acid, an inlet 22 for the hydrogen chloride-containing gas, and an outlet 23 for highly concentrated hydrochloric acid. Highly concentrated hydrochloric acid can be formed within the absorption device 20, and within the absorption device, the hydrogen chloride-containing gas supplied through the inlet 22 is absorbed into the low-concentration hydrochloric acid. After the highly concentrated hydrochloric acid exits the absorption device through the outlet 23, it is at a high pressure P. desIt is pumped to transport highly concentrated hydrochloric acid against it, preheated in a heat exchanger, and supplied into the high-pressure desorption device 10 through the inlet 13.

[0042] The low-pressure desorption device 30 is preferably a desorption tower (column), and includes a low-pressure reboiler 31, a top product stream outlet 32 for the hydrogen chloride-containing gas, and a low-pressure sump (drain) outlet 36. The low-pressure desorption device 30 is further provided with a flash vessel 33. A part of the liquid obtained at the bottom of the high-pressure desorption device 10 is recycled (recirculated) into the low-pressure desorption device 30 through the flash vessel 33. In the low-pressure desorption device 30, a hydrogen chloride-containing gas is formed and passed through the top product stream outlet 32 for the gas. The vapor formed in the flash vessel 33 is supplied into the hydrogen chloride-containing gas, and the hydrogen chloride-containing gas is supplied into the absorption device 20 through the inlet 22. At the bottom, the outlet 36 is passed through, and excess heat can be transferred to the highly concentrated hydrochloric acid pressurized from the bottom in the heat exchanger, and the pressurized highly concentrated hydrochloric acid is supplied into the device 10 through the inlet 13. The term "low pressure" when used with respect to the device 30 refers to being at a lower pressure compared to the pressure in the device 10. However, the pressure in the low-pressure desorption device 30 is typically sufficiently higher than the ambient atmospheric pressure.

[0043] As is clear, both the low-pressure desorption device and the absorption device as shown in FIG. 2 are sub-units connected to the high-pressure inlet 13 and the lower high-pressure outlet 14, and are configured to be able to regenerate at least a part of the pressurized highly concentrated hydrochloric acid supplied through the inlet 13 from at least a part of the liquid that can be obtained through the outlet 14.

[0044] To carry out the method of the present invention, a unit as shown in FIG. 2 can be operated, for example, under the following conditions: Composition at the supply port 21: hydrochloric acid (33 wt% HCl in water);

[0045] The following table gives examples of parameters for operating the devices 10, 20, and 30;

[0046]

Table 1

[0047] The pump is configured to be able to transport highly concentrated hydrochloric acid against high pressure P des and is configured to be able to transport highly concentrated hydrochloric acid against high pressure P

[0048] The weak acid discharged through the low-pressure sample outlet 36 contains 18% by weight of HCl. This weak acid can be treated, for example, using a solution of a hygroscopic salt such as CaCl2, by breaking the azeotropic mixture.

[0049] After removing residual moisture from the hydrogen chloride gas discharged through the outlet 15 by drying in the high-pressure condenser 12, the residual droplets conveyed by the flow obtained from the condenser 12 can be further removed using a high-pressure demister (not shown). This results in a very low residual water content.

[0050] Figures 3A and 3B show the boiling points in °C for various hydrogen chloride mass contents (horizontal axis) of the HCl / H2O binary system. These drawings show the boiling points at pressures of 2 bar (bottom curve), 5 bar (middle curve), and 11 bar (top curve). The arrows in Figures 3A and 3B indicate the thermal separation in the low-pressure desorption device 30 and the high-pressure desorption device 10, respectively. Thus, the arrows show how the present invention efficiently utilizes the very sharp decrease in the boiling point of the HCl / H2O binary system at hydrogen chloride mass contents exceeding 0.35, i.e., HCl concentrations exceeding 35% by weight.

Explanation of symbols

[0051] 10 High-pressure desorption device 11 High-pressure reboiler 12 High-pressure condenser 13 Tower inlet for pressurized highly concentrated hydrochloric acid 14 Lower high-pressure outlet 15 Upper high-pressure outlet 16 Internal tower structure 18 Line for cooled hydrogen chloride gas 19 Liquid distributor 20 Absorption device 21 Supply port for low-concentration hydrochloric acid 22 Inlet for hydrogen chloride-containing gas 23 Outlet for high-concentration hydrochloric acid 30 Low-pressure desorption device 31 Low-pressure reboiler 32 Top product outlet for hydrogen chloride-containing gas 33 Flash chamber 36 Low-pressure sample outlet

Claims

1. A method for producing hydrogen chloride, comprising: feeding pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or more into a high-pressure desorption device (10); operate the high-pressure separation device (10) at a temperature T of 110 to 200 °C and a pressure P of 2 bar or more at the bottom of the high-pressure separation device ｄｅｓ therein, desorbing hydrogen chloride in the high-pressure desorption device; at least a part of the highly concentrated hydrochloric acid being formed in an absorption device (20), and a hydrogen chloride-containing gas being absorbed in low-concentration hydrochloric acid in the absorption device; at least a part of the hydrogen chloride-containing gas absorbed in the low-concentration hydrochloric acid being formed in a low-pressure desorption device (30); a method in which at least a part of the liquid obtained at the bottom of the high-pressure desorption device (10) is recycled into the low-pressure desorption device (30).

2. The method according to claim 1, wherein the highly concentrated hydrochloric acid has a hydrogen chloride concentration of 40 to 60% by weight.

3. the pressure P ｄｅｓ The method according to claim 1, wherein the pressure P is in the range of 6 to 20 bar.

4. The method according to claim 1, wherein the temperature T is in the range of 120 to 175 °C.

5. The absorption device (20) operates at a pressure P ｄｅｓ lower than the pressure P ａｂｓ The method according to claim 1, wherein the method is performed.

6. In a unit for producing hydrogen chloride by the method according to claim 1, a high-pressure desorption device (10) for desorbing hydrogen chloride from pressurized highly concentrated hydrochloric acid, comprising: a high-pressure inlet (13) for feeding pressurized highly concentrated hydrochloric acid into the high-pressure desorption device (10); an upper high-pressure outlet (15) for hydrogen chloride desorbed in the high-pressure desorption device (10); and a lower high-pressure outlet (14) for the liquid obtained at the bottom of the high-pressure desorption device (10), the high-pressure desorption device (10); a subunit connected to the high-pressure inlet (13) and the lower high-pressure outlet (14), the subunit being configured to regenerate at least a part of the pressurized highly concentrated hydrochloric acid supplied through the high-pressure inlet (13) from at least a part of the liquid obtained through the lower high-pressure outlet (14); the subunit comprising a low-pressure desorption device (30) and an absorption device (20) having an outlet (23) for highly concentrated hydrochloric acid, the unit being designed to connect the outlet (23) for highly concentrated hydrochloric acid to the high-pressure inlet (13) and pressurize the highly concentrated hydrochloric acid from the outlet (23) and supply it into the high-pressure desorption device (10) through the high-pressure inlet (13). The low-pressure separation device (30) is provided with an inlet for liquid, the inlet for liquid is connected to the lower high-pressure outlet (14), and at least a part of the liquid obtained at the bottom of the high-pressure separation device (10) is recycled into the low-pressure separation device (30) through the inlet for liquid.

7. The unit according to claim 6, wherein the high-pressure separation device (10) is configured to operate at a pressure 5 bar or more higher than the ambient atmospheric pressure.

8. The unit according to claim 6, wherein the internal structure of the high-pressure separation device (10) is corrosion-resistant to pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or more at a temperature of 110 °C.

9. The unit according to claim 6, comprising a pump configured to supply highly concentrated hydrochloric acid against the high back pressure from the high-pressure separation device under a pressure of 2 bar or more.

10. The unit according to claim 6, which does not include a compressor for maintaining the inside of the high-pressure separation device at a high pressure P of 2 bar or more. ｄｅｓ ​

11. The unit according to claim 6, further comprising a hydrogen chloride filling device connected to the upper high-pressure outlet (15).

12. In a parts set for constructing the unit according to any one of claims 6 to 11, a high-pressure separation device (10) for desorbing hydrogen chloride from pressurized highly concentrated hydrochloric acid, a high-pressure inlet (13) for supplying pressurized highly concentrated hydrochloric acid into the high-pressure separation device (10), an upper high-pressure outlet (15) for hydrogen chloride desorbed in the high-pressure separation device (10), and a high-pressure separation device (10) comprising a lower high-pressure outlet (14) for liquid obtained at the bottom of the high-pressure separation device (10), an absorption device (20) comprising an outlet (23) for highly concentrated hydrochloric acid, the outlet (23) for highly concentrated hydrochloric acid is connected to the high-pressure inlet (13) via a pump, and is designed to pressurize the highly concentrated hydrochloric acid from the outlet (23) and supply it into the high-pressure separation device (10) through the high-pressure inlet (13), further comprising a low-pressure separation device (30) having an inlet for liquid, the inlet for liquid is connected to the lower high-pressure outlet (14), and is further designed such that at least a part of the liquid obtained at the bottom of the high-pressure separation device (10) is recycled into the low-pressure separation device (30) through the inlet for liquid.

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