High pressure desorption of hydrogen chloride gas

Abstract

To provide a method for producing a hydrogen chloride.SOLUTION: A pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or above is fed into a high pressure desorption device (10), the high pressure desorption device (10) is operated at a pressure Pdes of 2 bar or above and at a temperature T from 110 to 200°C in the bottom of the high pressure desorption device, and the hydrogen chloride is desorbed in the high pressure desorption device (10).SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In many processes, HCl gas or hydrochloric acid containing various types and amounts of impurities are produced as by-products or waste streams. A variety of processing techniques have been developed to recover HCl from these by-products and waste streams.

[0003] US Patent No. 5,399, 677 describes a method for recovering HCl from hydrochloric acid contaminated with salts of aluminum and other metals. Such (waste) liquids can be formed during the processing of certain ores with HCl. According to US Patent No. 5,399, 677, the contaminated hydrochloric acid is vaporized and the HCl-containing vapor is fed to a pressure swing distillation column. The overhead product, operating at high pressure, is HCl-rich and can contain more than 90% HCl, and is sufficiently pure to be recycled in upstream processes and processes.

[0004] Patent Document 2 attempts to obtain hydrogen chloride gas containing more than 99% by weight hydrogen chloride or less than 0.03% by weight water from an aqueous solution of hydrochloric acid. To this end, Patent Document 2 discloses feeding an aqueous solution of hydrochloric acid containing more HCl than the azeotropic mixture of HCl and water to the top of a tower, and feeding a hot hygroscopic salt solution to the middle of the tower. Effluent vapor containing HCl and water leaves the top of the tower. Patent Document 2 further teaches reducing the water 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 method for concentrating hydrochloric acid described in Patent Document 3 comprises extractively distilling a raw material aqueous hydrogen chloride solution in the presence of an extractant (e.g., 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 portion of the distillation apparatus. Patent Document 3 describes that water can be removed by condensation from the hydrogen chloride gas obtained from the upper portion of the distillation apparatus.

[0006] The HCl obtained from these processes is not always sufficiently pure and in the physical state (high density, e.g., compressed, or even liquefied) desired for delivery for particularly demanding applications, such as semiconductor manufacturing, where "electronic grade HCl" is used as an etching, cleaning, and deposition gas.

[0007] Various attempts have been made to provide HCl of the desired purity and physical state (high pressure, liquefied state) for such applications. For example, US Pat. No. 5,299,433 and US Pat. No. 5,363,666 teach two completely different methods for forming such HCl. Both methods involve, in addition to upstream processing steps, compression with a compressor to form condensed (liquefied) HCl. In particular, US Pat. No. 5,299,433 describes compressing and liquefying anhydrous crude hydrogen chloride at a pressure of, for example, 2.6 MPa (absolute pressure) or more at approximately 0° C. According to the methods described in US Pat. No. 5 and US Pat. No. 5,433,666, the liquefied HCl must be further purified by distillation. US Pat. No. 5,299,433 teaches that a rectification apparatus (distillation column) such as a plate column or a packed column is preferably used for the distillation.

[0008] Compressors cannot be made entirely of (graphite-based) materials that do not corrode with HCl. Thus, the HCl gas compressed in the compressor is always contaminated to some extent by the metals and other non-HCl resistant materials of the compressor. The HCl extracts these metals and other non-HCl resistant materials from the compressor. Compressors used to compress HCl require a lot of maintenance because the HCl corrodes the compressor. In this regard, methods that include significant HCl gas compression, such as those described in US Pat. No. 5,399,433 and US Pat. No. 5,499,433, are disadvantageous because part of the purification achieved in the rectification unit requires the removal of contaminants from the upstream compressor. Furthermore, there is little room for improving the compressor to increase HCl stability and reduce maintenance requirements. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] German Utility Model No. 202020101571 [Patent Document 2] British Patent No. 669671 [Patent Document 3] European Patent No. 2909132 [Patent Document 4] European Patent Application No. 3336056 [Patent Document 5] European Patent Application No. 3336057 Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide a reliable and efficient method and unit for producing hydrogen chloride for demanding applications (e.g., electronic grade HCl, etc.) with minimal risk of contamination. [Means for solving the problem]

[0011] The object of the present invention is to provide a high-pressure desorption apparatus with pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or more, and to provide a high-pressure desorption apparatus with 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 apparatus. des The above-mentioned problems are solved by a method for producing hydrogen chloride, comprising operating a high-pressure desorption device at a high pressure and desorbing hydrogen chloride in the high-pressure desorption device.

[0012] According to the present invention, the hydrogen chloride that is released is des is automatically obtained in the process and does not contain any (non-volatile) contaminants due to the compression of HCl in the compressor. Downstream compression of hydrogen chloride can therefore be partially or completely avoided. An earlier compression stage, i.e. due to an initial HCl gas volume larger than the downstream compression stages, can be completely avoided. Fewer compression stages result in purer hydrogen chloride compared to hydrogen chloride brought to a compressed state only in the compressor. The hydrogen chloride produced according to the process of the invention is pure, since the process can be carried out at relatively low temperatures, particularly using corrosion-stable materials. For example, the introduction of metal contaminants is necessarily lower than in processes with more HCl gas compression.

[0013] Rather than increasing the pressure of hydrogen chloride by compressing it in a compressor, a pump (e.g., a centrifugal pump) can be used to increase the pressure in the liquid, highly concentrated hydrochloric acid, improving reliability and efficiency. Hydrochloric acid pumps are much more reliable than hydrogen chloride gas compressors and are also highly efficient because the frequent maintenance of fragile HCl gas compressors is at least partially avoided.

[0014] Because hydrogen chloride is desorbed in the high pressure desorber, the hydrogen chloride produced in accordance with the present invention is gaseous as it exits the high pressure desorber. This gas may contain entrained liquid droplets. After exiting the high pressure desorber, the hydrogen chloride gas may be converted, for example, to liquid hydrogen chloride. However, depending on the customer's requirements and the specific processes being carried out at the customer's site, the hydrogen chloride is often kept in gaseous form and fed to a process that consumes hydrogen chloride gas. In accordance with the present invention, P descan be widely adapted depending on the compression of hydrogen chloride desired by the customer. The present invention is not limited with respect to the phase of hydrogen chloride produced, and the invention disclosed herein refers to a "method for producing hydrogen chloride" without limiting the 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 fed to the high pressure desorption apparatus has a hydrogen chloride concentration of 35% by weight or more. This means that 100 grams of hydrochloric acid contains 35 grams of HCl or more. As can be seen from the following Figures 3A and 3B, 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 a hydrogen chloride concentration of, for example, 40-60% by weight. This allows operation at low temperatures to avoid equipment problems. The life of corrosion-stable (graphite-based) equipment in the high pressure desorption apparatus is extended because the temperature in the apparatus does not approach dangerous temperatures (around 200°C for resin-impregnated graphite equipment). The use of such hydrogen chloride concentrations leads to long equipment life, reliable equipment design, and less downtime of the unit including the high pressure desorption apparatus. Preferably, the highly concentrated hydrochloric acid has a hydrogen chloride concentration of 40-58% by weight, more preferably 40-56% by weight, and most preferably 40-55% by weight.

[0016] Any pressure P above 2 bar des is suitable for the present invention because it necessarily results in a pressurized desorbed hydrogen chloride product that is denser and takes up less volume than the unpressurized hydrogen chloride product. des can be 3 bar or more, preferably 4 bar or more, for example 5 bar or more. des suggests that desorbed hydrogen chloride with approximately the same pressure is produced by the high-pressure desorber. des Operation at 1000 rpm is an elegant method for providing HCl at the high pressures required at production sites with little or no downstream compression. Compressors for HCl gas frequently fail and require significant maintenance, which can be avoided by the present invention. 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 pressures P des is 10 bar.

[0017] All pressures stated herein are absolute pressures.

[0018] According to the invention, the desorber operates at a temperature T of 110-200°C at the bottom of the high-pressure desorber. Within this temperature range, it is possible to actually desorb hydrogen chloride from the highly concentrated hydrochloric acid fed into the high-pressure desorber. As will be clear to those skilled in the art, a low temperature of only 110°C or just above 110°C is sufficient if the highly concentrated hydrochloric acid is very HCl-rich and the high-pressure desorber operates at low pressure. If the highly concentrated hydrochloric acid is not very HCl-rich and the high-pressure desorber operates at higher pressure, a high temperature of 200°C or just below 200°C is preferably selected. The temperature T is preferably in the range of 120-175°C, for example in the range of 120-165°C. This results in a long life and good reliability of the corrosion-stable equipment. As a result, many downtimes for maintenance of the high-pressure desorber can be avoided, further improving the overall reliability and efficiency of the process of the invention.

[0019] The above described method can be carried out at any site where pressurized highly concentrated hydrochloric acid is available as defined herein.

[0020] At many sites, such pressurized, highly concentrated hydrochloric acid is not available, and so the present invention includes optional upstream processing techniques to form pressurized, highly concentrated hydrochloric acid from the less concentrated hydrochloric acid that is produced at a wide variety of sites but which cannot be discharged from the sites for environmental reasons.

[0021] At least a portion of the highly concentrated hydrochloric acid can be formed in an absorber in which hydrogen chloride-containing gas is absorbed into the less concentrated hydrochloric acid, allowing the high pressure desorber of the present disclosure to operate at any site where hydrogen chloride-containing gas (e.g., waste gas) and hydrochloric acid are available that are, in aggregate, sufficiently HCl-rich to provide the hydrochloric acid with an HCl concentration of 35% by weight or greater.

[0022] Typically, the absorber is des Lower pressure P abs It works in P abs The pressure P can be in the range of 1 to 10 bar, for example, 2.5 to 7.5 bar. des For example, P abs The pressure P may be at least 1 bar higher, preferably at least 1.5 bar higher, most preferably at least 2 bar higher, for example at least 2.5 bar higher. des In particular, P abs is 1 to 15 bar higher, 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 a (liquid) hydrochloric acid (waste) stream is available and needs to be treated, while a hydrogen chloride-containing gas is not. To make the present invention applicable in such sites, a preferred method of the present invention includes the generation of such a hydrogen chloride-containing gas. Thus, in a preferred method of the present invention, at least a portion of the hydrogen chloride-containing gas to be absorbed in the low-concentration hydrochloric acid is formed in a low-pressure desorber.

[0024] The term "low" in "low pressure desorber" is used to clarify that the desorber operates at a lower pressure than the high pressure desorber. The pressure in the low pressure desorber is typically slightly higher than the pressure in the absorber so that a compressor is not required to direct the hydrogen chloride-containing gas from the low pressure desorber into the absorber.

[0025] The low pressure desorber may be supplied with hydrochloric acid of sufficient concentration. According to a preferred method of the invention, at least a portion of the liquid obtained at the bottom of the high pressure desorber is recycled (recirculated) into the low pressure desorber. The HCl concentration of the liquid obtained at the bottom of the high pressure desorber is high enough to desorb a sufficient concentration of hydrogen chloride-containing gas at low pressure in the low pressure desorber and is sufficiently suitable to concentrate in an absorber the typical hydrochloric acid (waste) stream available on many sites.

[0026] The present invention also relates to a unit for producing hydrogen chloride, said unit comprising: A high pressure desorption apparatus for desorbing hydrogen chloride from pressurized highly concentrated hydrochloric acid, the high pressure desorption apparatus comprising a high pressure inlet for feeding pressurized highly concentrated hydrochloric acid into the high pressure desorption apparatus, an upper high pressure outlet for hydrogen chloride that may be desorbed in the high pressure desorption apparatus, and a lower high pressure outlet for liquid that may be obtained at the bottom of the high pressure desorption apparatus; A subunit connected to the high pressure inlet and the lower high pressure outlet, and configured to be able to regenerate at least a portion of the pressurized highly concentrated hydrochloric acid provided via the high pressure inlet from at least a portion of the liquid available through the lower high pressure outlet. All of the processing equipment shown to the left of the high pressure desorption device in Figure 2 are examples of such subunits. 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 portion of the pressurized highly concentrated hydrochloric acid provided via the high pressure inlet from at least a portion of the liquid available through the lower high pressure outlet, is a suitable subunit.

[0027] According to the present invention, the high pressure desorption apparatus may preferably operate at a pressure of 5 bar or more above the surrounding atmospheric pressure, more preferably 6 bar or more above, for example 7 bar or more above.

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

[0029] The internals of the high pressure desorber are 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 appreciate that such corrosion resistance can be achieved using columns with graphite or carbon internals lined with, for example, PTFE, sold by SGL under the name Polyfluoron®. Tantalum columns or tantalum-lined columns are also available, especially for small pilot plants.

[0030] A preferred unit or method of the present invention comprises a pump, which is configured to supply highly concentrated hydrochloric acid against a high back pressure from the high pressure desorber, which is at a pressure of 2 bar or more, particularly 6 bar or more, in the high pressure desorber. The pump is typically a corrosion-resistant centrifugal pump, which supplies highly concentrated hydrochloric acid in the high pressure desorber. The pump replaces one or more stages of a downstream hydrogen chloride compression unit. This is advantageous because the pump is much smaller than the compressor and requires less maintenance. This contributes to high process efficiency, since many downtimes of the unit of the present invention can be avoided. A particular unit of the present invention will not comprise a compressor for compressing the HCl-containing gas. A particular method of the present invention will not include compression of the HCl-containing gas. A particularly preferred unit or method of the present invention comprises a high pressure P2 gas in the high pressure desorber, which is at a pressure of 2 bar or more, particularly 6 bar or more. des In order to maintain this, the compressor is not provided.

[0031] The present invention further 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 feeding pressurized highly concentrated hydrochloric acid into the high-pressure desorption device, an upper high-pressure outlet for hydrogen chloride that may be desorbed in the high-pressure desorption device, and a lower high-pressure outlet for liquid that may be obtained at the bottom of the high-pressure desorption device, the hydrogen chloride supply unit also comprising a hydrogen chloride filling device connected to the upper high-pressure outlet.

[0032] The term "hydrogen chloride filling equipment" includes any equipment configured to separate a (continuous) hydrogen chloride fluid stream (which may be in liquid or gaseous state) into spatially separated quantities of hydrogen chloride fluid (e.g., various grades of liquefied hydrogen chloride gas from various suppliers such as BOC, Linde, Praxair, etc.) that can be filled into suitable tube trailers, tonne containers, or cylinders.

[0033] The hydrogen chloride charging device may be connected, for example, to the upper high-pressure outlet so that hydrogen chloride passing through the high-pressure outlet is directed to a high-pressure condenser, from the high-pressure condenser to a high-pressure demister, and from the high-pressure demister to the hydrogen chloride charging device. des If the hydrogen chloride gas pressure is high, even liquefied hydrogen chloride can be obtained by cooling (and condensation), which means that the effort of compressing hydrogen chloride gas is reduced. The hydrogen chloride charging device can be connected to the upper high-pressure outlet, for example, so that the hydrogen chloride passing through the high-pressure outlet is directed to the hydrogen chloride cleaning and liquefaction unit, and from the hydrogen chloride cleaning and liquefaction unit to the hydrogen chloride charging device. Any unit that reduces the impurity content in hydrogen chloride is considered as a hydrogen chloride cleaning unit. Suitable equipment for such a hydrogen chloride cleaning and liquefaction unit is clear to a person skilled in the art, and is described, for example, in US Pat. No. 5,999,333 and US Pat. No. 5,999,333. A person skilled in the art can design the hydrogen chloride cleaning unit so that the hydrogen chloride charged to the charging device meets the specifications desired by the customer.

[0034] The present invention also relates to a set of parts for constructing a unit of the present invention, said set of parts comprising a high-pressure desorption device for desorbing hydrogen chloride gas from pressurized highly concentrated hydrochloric acid, said 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 gas that can be desorbed in the high pressure desorption device; a lower high pressure outlet for liquid available at the bottom of the high pressure desorption device, The set of parts also includes an absorption device with an outlet for highly concentrated hydrochloric acid, The part set is designed so that the outlet for highly concentrated hydrochloric acid can be connected to the high pressure inlet via a pump, and the highly concentrated hydrochloric acid from the upper high pressure outlet can be pressurized and supplied into the high pressure desorption device via the high pressure inlet.

[0035] The part set may further comprise a low-pressure desorption device having an inlet for liquid, the part set being preferably designed so that the inlet for liquid can be connected to the lower high-pressure outlet so that at least a portion of the liquid obtained at the bottom of the high-pressure desorption device can be recycled (recirculated) into the low-pressure desorption device via the inlet for liquid.

[0036] Any features described herein with respect to (a) the method for producing hydrogen chloride according to the invention, (b) the unit for producing hydrogen chloride according to the invention, (c) the hydrogen chloride supply unit according to the invention, and (d) the set of parts according to the invention are not intended to be limiting, and features described with respect to any of (a), (b), (c), and (d) may be features of the others of (a), (b), (c), and (d).

[0037] The invention will be illustrated with reference to the drawings described below, which are for illustration purposes only and are not limiting of the claims. [Brief description of the drawings]

[0038] [Figure 1] FIG. 1 is a simplified process flow diagram of a high pressure desorption apparatus suitable for the process of the present invention. [Diagram 2] FIG. 1 is a simplified process flow diagram of a unit according to the present invention. [Figure 3A] 1 is a graph showing boiling points at various hydrochloric acid concentrations (low concentration range). [Figure 3B] 1 is a graph showing boiling points at various hydrochloric acid concentrations (high concentration range). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] The high pressure desorption apparatus 10 shown in FIG. 1 is a PTFE-lined high pressure desorption column with a high pressure inlet 13 for feeding pressurized highly concentrated hydrochloric acid into the apparatus 10, a lower high pressure outlet 14 for liquid that may be obtained at the bottom of the apparatus 10, and an upper high pressure outlet 15 for hydrogen chloride gas that may be desorbed in the apparatus 10. The bottom is heated in a high pressure reboiler 11. The water contained in the desorbed hydrogen chloride gas leaves the apparatus via outlet 15 and is condensed in a high pressure condenser 12. The cooled hydrogen chloride gas leaves the condenser 12 via line 18 and the condensed liquid is recycled into the apparatus 10. Although not all details are shown, FIG. 1 shows that the desorption apparatus may include a column internal 16 (e.g., made of CFRC or CFRP, Sigrabond® chemical line from SGL) and a liquid distributor 19. Also, FIG. 1 is simplified and does not show the means for providing high pressure and corrosion stability of the column. Even when highly corrosive pressurized and highly concentrated hydrochloric acid is fed into the column through inlet 13, the column will continue to operate at high bottom temperatures T of 110-200° C. and high pressures P of up to 20 bar. des Therefore, the method of the present invention can be carried out satisfactorily in an apparatus such as that shown in FIG.

[0040] Figure 2 shows a high pressure desorber 10 (as shown in Figure 1) as part of a unit according to the invention. The unit further comprises an absorber 20 and a low pressure desorber 30.

[0041] The absorber 20 comprises an inlet 21 for low concentration hydrochloric acid, an inlet 22 for hydrogen chloride-containing gas and an outlet 23 for high concentration hydrochloric acid. High concentration hydrochloric acid can be formed in the absorber 20, in which the hydrogen chloride-containing gas fed via inlet 22 is absorbed in the low concentration hydrochloric acid. After leaving the absorber through outlet 23, the high concentration hydrochloric acid is mixed with the high pressure P desThe highly concentrated hydrochloric acid is pumped against the high pressure desorber 10, preheated in a heat exchanger, and fed into the high pressure desorber 10 via inlet 13.

[0042] The low-pressure desorber 30 is preferably a desorption column, and comprises a low-pressure reboiler 31, a top product outlet 32 ​​for hydrogen chloride-containing gas, and a low-pressure sump outlet 36. The low-pressure desorber 30 further comprises a flash vessel 33. Part of the liquid obtained at the bottom of the high-pressure desorber 10 is recycled to the low-pressure desorber 30 via the flash vessel 33. In the low-pressure desorber 30, a hydrogen chloride-containing gas is formed and passed to the top product outlet 32 ​​for gas. The vapor formed in the flash vessel 33 is fed into the hydrogen chloride-containing gas, which is fed into the absorber 20 via the inlet 22. The bottom is passed through an outlet 36, allowing excess heat to be transferred in a heat exchanger from the bottom to the pressurized highly concentrated hydrochloric acid, which is fed into the device 10 via the inlet 13. The term "low pressure" when used with respect to apparatus 30 refers to a pressure that is low compared to the pressure within apparatus 10. However, the pressure within low pressure desorption apparatus 30 is typically significantly greater than the surrounding atmospheric pressure.

[0043] It is clear that both the low pressure desorber and the absorber as shown in FIG. 2 are considered as subunits connected to the high pressure inlet 13 and the lower high pressure outlet 14 and configured so as to be able to regenerate at least a portion of the pressurized highly concentrated hydrochloric acid supplied via inlet 13 from at least a portion of the liquid obtainable through outlet 14.

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

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

[0046] [Table 1]

[0047] The pump is a high-pressure P des The present invention is configured to be capable of transporting highly concentrated hydrochloric acid against the

[0048] The weak acid discharged through the low pressure sump outlet 36 contains 18% HCl by weight. This weak acid can be treated by breaking the azeotrope, for example, with a solution of a hygroscopic salt such as CaCl.

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

[0050] In Figures 3A and 3B the boiling point in °C (vertical axis) is shown for various hydrogen chloride mass contents (horizontal axis) of the HCl / H2O binary system. The figures 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 desorber 30 and the high pressure desorber 10, respectively. Thus, the arrows show how the present invention efficiently exploits the very sharp drop in the boiling point of the HCl / H2O binary system at hydrogen chloride mass contents above 0.35, i.e., HCl concentrations above 35 wt.%. [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 Tower internal structure 18 Line for cooled hydrogen chloride gas 19 Liquid distributor 20 Absorber 21 Supply port for low concentration hydrochloric acid 22 Inlet for hydrogen chloride-containing gas 23 Outlet for highly concentrated hydrochloric acid 30 Low Pressure Desorption Apparatus 31 Low pressure reboiler 32 Top product outlet for hydrogen chloride-containing gas 33 Flash Room 36 Low pressure sump outlet

Claims

1. 1. A method for producing hydrogen chloride, comprising: Supplying pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or more into a high pressure desorption apparatus (10); The high-pressure desorption device (10) is heated to a temperature T of 110 to 200° C. at the bottom of the high-pressure desorption device and a pressure P of 2 bar or more. ｄｅｓ Operate in Desorbing hydrogen chloride in said high pressure desorption device.

2. 2. The method of 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 is in the range of 6 to 20 bar.

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

5. 2. The method of claim 1, wherein at least a portion of the highly concentrated hydrochloric acid is formed in an absorber (20) in which hydrogen chloride-containing gas is absorbed in the less concentrated hydrochloric acid.

6. The absorber (20) is ｄｅｓ Lower pressure P ａｂｓ The method of claim 5 , operating in

7. 6. The method of claim 5, wherein at least a portion of the hydrogen chloride-containing gas absorbed in the less concentrated hydrochloric acid is formed in a low pressure desorber (30).

8. 8. The method according to claim 7, wherein at least a portion of the liquid obtained at the bottom of the high pressure desorber (10) is recycled into the low pressure desorber (30).

9. In a unit for producing hydrogen chloride, A high pressure desorption apparatus (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 high-pressure desorption apparatus (10) comprising a lower high-pressure outlet (14) for liquid obtained at the bottom of said high-pressure desorption apparatus (10); a sub-unit connected to said high pressure inlet (13) and said lower high pressure outlet (14), said sub-unit configured to regenerate at least a portion of the pressurized highly concentrated hydrochloric acid supplied via said high pressure inlet (13) from at least a portion of the liquid obtained through said lower high pressure outlet (14).

10. 10. A unit as claimed in claim 9, wherein the high pressure desorber (10) is adapted to operate at a pressure of at least 5 bar above the surrounding atmospheric pressure.

11. 10. The unit of claim 9, wherein the internal structure of the high pressure desorber (10) is resistant to corrosion by pressurized highly concentrated hydrochloric acid having a hydrogen chloride concentration of 35% by weight or more at a temperature of 110°C.

12. 10. The unit of claim 9, further comprising a pump configured to deliver highly concentrated hydrochloric acid against high back pressure from the high pressure desorber, which is at a pressure of 2 bar or more.

13. The inside of the high-pressure desorption device is subjected to a high pressure P ｄｅｓ 11. The unit of claim 10, which does not include a compressor for maintaining

14. In the hydrogen chloride supply unit, A high pressure desorption apparatus (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 high-pressure desorption apparatus (10) comprising a lower high-pressure outlet (14) for liquid obtained at the bottom of said high-pressure desorption apparatus (10); and a hydrogen chloride filling device connected to the upper high pressure outlet (15).

15. A parts set for constructing a unit according to any one of claims 9 to 14, A high pressure desorption apparatus (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 high-pressure desorption apparatus (10) comprising a lower high-pressure outlet (14) for liquid obtained at the bottom of said high-pressure desorption apparatus (10); an absorber (20) having an outlet (23) for highly concentrated hydrochloric acid, A part set designed to connect the highly concentrated hydrochloric acid outlet (23) to the high pressure inlet (13) via a pump, and to pressurize the highly concentrated hydrochloric acid from the outlet (23) and supply it into the high pressure desorption device (10) via the high pressure inlet (13).

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