Autoclave and a method for removing salt from an autoclave

Abstract

A vertical autoclave according to embodiments of the present disclosure is a vertical autoclave that includes an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet pump through which oxygen is introduced into the process solution, a mixer configured to mix the process solution, an inner wall, an acid-resistant brick layer disposed on the bottom and side portions of the inner wall, and an acid-resistant metal layer disposed on the top portion of the inner wall. One method of removing salt from an autoclave involves raising the level of a solution in the autoclave from a first level to a second level, such that the salt in the autoclave is immersed in the solution and the solution level is maintained at the second level. The salt dissolves in the solution while the solution level is maintained at the second level.

Description

Autoclave and a method for removing salt from an autoclave Technical background

[0001] This disclosure relates to autoclaves and a method for removing salt from an autoclave, and more particularly to vertical autoclaves and a method for removing salt from a vertical autoclave. Prior knowledge

[0002] To carry out a reaction under high temperature and high pressure conditions, an autoclave, which is a high pressure reactor, is required. Conventionally, horizontal autoclaves capable of increasing capacity by increasing their length while maintaining or even reducing their diameter have been widely used to construct a large capacity autoclave. Such conventional horizontal autoclaves are disclosed in International Patent Publication No. 2015 / 021524, United States Patent Publication No. 2015 / 0086450, United States Patent No. 9,732,400 and the like.

[0003] A common feature of these horizontal autoclaves is that the interior of an autoclave is divided into several small sections, each of which is provided with a separate agitator, thereby converting several autoclaves into a single integrated unit. This horizontal autoclave may be advantageous because it is easy to construct a horizontal autoclave, since it is possible to increase the capacity of the device by increasing the number of sections, even if its diameter is small, and a high-capacity device can be operated using small-scale agitators.

[0004] However, in the case of horizontal autoclaves, it may be necessary to install a number of agitators in one apparatus and to install a device for introducing oxygen or the like separately for each section, so that the number of necessary nozzles, etc., may increase and the operating speed of the apparatus may be reduced due to frequent failure of the apparatus.

[0005] In addition, in the case of horizontal autoclaves, the process solution reacted in each section must be delivered to the top of a blocking wall installed between adjacent sections to be transferred to the next section. However, because the top of the blocking wall is exposed to a hot gas, a large amount of salt may be seen on the top of the blocking wall due to the evaporation phenomenon of the process solution.

[0006] In addition, due to the characteristics of the horizontal autoclave, a contact interface between the process solution and the gas layer is wide in the upper part. Since the gas layer is maintained at a high temperature, a large amount of salt is deposited on the surface of the process solution and a wall part through the evaporation phenomenon of the process solution. When the deposited salt grows into a mass, it may cause the failure of the device. Therefore, it may be necessary to periodically stop the device and carry out maintenance to remove the deposited salt. Therefore, horizontal autoclaves have the disadvantage that the performance of the device is significantly reduced.

[0007] Furthermore, because horizontal autoclaves have an internal structure divided by partition walls and angular corners formed in the respective sections, the process solution is not well mixed. Detailed description of the invention Technical problem

[0008] One aspect of the present disclosure is to provide a vertical autoclave for use in a zinc process and the like, capable of providing large capacity, low production cost, and high wear resistance to slurry.

[0009] Another aspect of the present disclosure is to provide a vertical autoclave for use in zinc processing and the like, which is capable of providing a large capacity and is capable of overcoming problems such as cracking and falling of acid-resistant bricks stacked therein.

[0010] Another aspect of the present disclosure is to provide a vertical autoclave for use in a zinc process and the like, which is capable of providing a large capacity, is capable of facilitating the production of a mixing shaft, and is capable of restraining bending of the mixing shaft or the like. Technical solution

[0011] A vertical autoclave according to an embodiment of the present disclosure is a vertical autoclave that includes an inlet port through which a process solution is discharged, an outlet port through which the process solution is introduced, an oxygen inlet port through which oxygen is supplied to the process solution, and a mixer configured to mix the process solution.

[0012] The autoclave has an inner wall, an acid-resistant brick layer located on the bottom and side of the inner wall, and an acid-resistant metal layer located on the top of the inner wall.

[0013] A vertical autoclave may have an internal diameter of 5.5 meters or more.

[0014] A vertical autoclave may have an internal volume of 150 cubic meters or more.

[0015] The volume of process solution when the vertical autoclave is activated may be 100 cubic meters or more.

[0016] The autoclave may include a cap ring that covers the top of the acid-resistant brick layer on the side of the inner wall.

[0017] The autoclave may include a membrane layer between the inner wall and the acid-resistant brick layer, and the membrane layer may be positioned between the top of the acid-resistant brick layer and the cap ring.

[0018] The autoclave may include a number of latches that connect the cap ring and the acid-resistant metal layer.

[0019] The cap ring and some of the ribs may be made of the same material as the acid-resistant metal layer.

[0020] Voids may form between the latches, cap ring, and acid-resistant layers.

[0021] The inlet port may be located at the top of the interior wall and the outlet port may be located at the side of the interior wall.

[0022] The inlet port may extend into the vertical autoclave, and when the vertical autoclave is operating, the end of the inlet port may be immersed in the process solution.

[0023] The inlet port and the outlet port may be located on the side of the interior wall, and the inlet port may be located at a higher position than the outlet port.

[0024] The oxygen inlet port may be located at the bottom of the interior wall, and the vertical autoclave may include an oxygen inlet line connected to the oxygen inlet port and a cooling water passage positioned to surround the oxygen inlet port.

[0025] The vertical autoclave may include a high pressure steam line connected to the oxygen inlet line. Steam is supplied to the oxygen inlet port through the high pressure steam line.

[0026] When the vertical autoclave is operating, the level of the process solution water in the vertical autoclave can be set lower than the top of the acid-resistant brick layer provided on the side of the inner wall.

[0027] The acid-resistant metal layer may extend upwardly to the side portion of the inner wall.

[0028] In the upper part of the side part of the inner wall, the acid-resistant metal layer may extend between the inner wall and the acid-resistant brick layer.

[0029] An autoclave apparatus according to embodiments of this disclosure includes a first autoclave and a second autoclave connected in series.

[0030] Each of the first autoclave and the second autoclave is a vertical autoclave that includes an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet port through which oxygen is supplied to the process solution, a mixer configured to mix the process solution, an inner wall, an acid-resistant brick layer on the bottom and side of the inner wall, and an acid-resistant metal layer disposed on the top.

[0031] The autoclave apparatus may include a connecting pipe connecting the first autoclave and the second autoclave. The upstream portion of the connecting pipe may be associated with the first outlet port of the autoclave, and the downstream portion of the connecting pipe may be associated with the second inlet port of the autoclave.

[0032] When the first autoclave and the second autoclave are operating, the outlet port of the first autoclave may be immersed in a solution in the first autoclave and the inlet port of the second autoclave may be immersed in a solution in the second autoclave.

[0033] The first autoclave may be installed in a higher position than the second autoclave.

[0034] The autoclave apparatus may include at least one flash tank (flash vessel) connected to the outlet port of the second autoclave.

[0035] A method of removing salt from an autoclave according to the presently described embodiments includes raising the level of a solution in the autoclave from a first level to a second level, such that salt from the autoclave is immersed in the solution and the solution level is maintained at the second level.

[0036] The salt dissolves in the solution while the solution level is maintained at the second level.

[0037] The salt may be soluble in water.

[0038] The solution level is maintained at the second level for one to six hours.

[0039] The method may include reducing the solution level again from the second level to the first level.

[0040] The autoclave is a vertical autoclave comprising an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet port through which oxygen is supplied to the process solution, a mixer configured to mix the process solution, an inner wall, an acid-resistant brick layer on the bottom and side of the inner wall, and an acid-resistant metal layer disposed on the top.

[0041] The second level may be lower than the top level of the acid-resistant brick layer.

[0042] The autoclave may include a cap ring that covers the top of the acid-resistant brick layer on the side of the inner wall.

[0043] The second level may be lower than the lowest level of the cap ring. Beneficial effects

[0044] By placing acid-resistant bricks in the lower and side portions of the inner wall of the autoclave that are in contact with the process solution, it is possible to reduce the manufacturing cost of the autoclave and increase the abrasion resistance against the slurry in the process solution.

[0045] Also, by placing a layer of an acid-resistant metal in the upper dome portion where it is difficult to place acid-resistant bricks between the inner wall of the autoclave and where the stacked bricks are easily tripped or the acid-resistant bricks may easily fall off, the difficulty in manufacturing a high-capacity autoclave can be reduced and the stability of the autoclave can be increased.

[0046] In addition, in the production of a large-capacity vertical autoclave, the height of the autoclave can be reduced while the diameter of the autoclave is increased. Therefore, by preventing the length of the mixing shaft from increasing excessively, the mixing shaft can be kept from bending.

[0047] In addition, the process solution entering the autoclave and the process solution discharged from the autoclave do not enter the gas phase section. Therefore, it is possible to prevent the generation of salt at the inlet port, outlet port, inlet pipe and / or outlet pipe and to prevent the inlet port, outlet port, inlet pipe and / or outlet pipe from being blocked by salt.

[0048] In addition, the height of the autoclave solution is relatively higher than that of the horizontal autoclave for the same amount of process solution. Therefore, it is possible to ensure that the oxygen introduced from the bottom of the autoclave into the process solution has sufficient residence time (or sufficient reaction time), so that the oxygen reaction efficiency is improved.

[0049] In addition, the interface area between the solution and the gas phase portion in the autoclave is relatively small compared to a horizontal autoclave. Therefore, the amount of salt produced at the interface between the solution and the gas phase portion can be reduced.

[0050] In addition, the interior of the autoclave has a circular horizontal cross-section. Therefore, the autoclave does not have angular corners like a horizontal autoclave. Therefore, the shaking efficiency can also be increased.

[0051] In addition, the solution level can be easily adjusted with a simple operation. Therefore, the produced salt can be easily removed by raising the solution level above the produced salt for a predetermined period of time. Brief description of the shapes

[0052] Figures 1A to 1D are cross-sectional views illustrating an autoclave according to an embodiment of the present disclosure;

[0053] Figure 2 is an enlarged view of section A in the autoclave of Figure 1A;

[0054] Figure 3 is an enlarged view of an oxygen inlet port in an autoclave, in accordance with embodiments of the present disclosure;

[0055] Figures 4A to 4D are views illustrating a method for removing salt produced in an autoclave, in accordance with embodiments of the present disclosure;

[0056] Figure 5 is a view showing a structure in which autoclaves are connected in series in accordance with embodiments of the present disclosure;

[0057] Figure 6 is a process flowchart for recovering hematite according to embodiments of this disclosure.

[0058] Figure 7 is a graph showing the X-ray diffraction (XRD) spectrum of an iron precipitate as a function of reaction temperature.

[0059] Figure 8 is a graph showing the spectrum according to X-ray diffraction spectroscopy of a material produced and adhered to the reactor wall. and

[0060] Figure 9 is a diagram of an installation of an autoclave apparatus according to embodiments of the present disclosure. A state of being for invention

[0061] Figures 1A through 1D are cross-sectional views, each illustrating an autoclave 100 according to embodiments of the present disclosure.

[0062] Referring to FIGS. 1A to 1D, the autoclave 100 has a vertical structure. In other words, unlike a horizontal autoclave in which the interior is divided into a series of sections and a mixer is provided separately in each section, the interior of the vertical autoclave 100 is provided as a single space rather than being divided into a number of sections.

[0063] An autoclave 100 according to the present disclosure includes an inlet port 10, 13, 15 or 17 through which a process solution is introduced, an outlet port 20 or 25 through which the process solution is discharged, an oxygen inlet port 30 through which oxygen is supplied to the process solution, a mixer 40 for mixing the process solution, an outer shell 50, an acid-resistant organic layer 60, an acid-resistant metal layer 70 and a cap ring 80.

[0064] The shape of the autoclave 100 is determined by the outer shell 50, which includes an outer wall 50b that contacts the outside of the autoclave 100 and an inner wall 50a that defines the interior space of the autoclave 100.

[0065] The interior of the autoclave 100 has a circular horizontal cross-section. Therefore, there are no angular corners in the interior of the autoclave 100 like in a horizontal autoclave, so that the stirring efficiency can be improved.

[0066] The autoclave 100 may be divided into an upper part T, a side part S and a lower part B, where the upper part T and the lower part B have a dome-shaped structure. In addition, the side part S may be formed perpendicular to the ground surface.

[0067] The bottom portion B and the side portion S of the inner wall 50a of the autoclave 100 may be installed with an acid-resistant brick layer 60. When performing a high-temperature, high-pressure acid leaching process in the autoclave 100, the water level of a solution L including the process solution in the autoclave 100 may be adjusted to be lower than the top portion of the acid-resistant brick layer 60 accumulated on the side portion S of the inner wall 50a. That is, the solution L is in contact with the acid-resistant brick layer 60, but may not be in contact with the acid-resistant layer 70. In addition, a gas phase portion G may be mainly in contact with the acid-resistant metal layer 70.

[0068] A large amount of slurry in the solution L is produced by an acid leaching process carried out at high temperature and high pressure. In order to resist abrasion caused by the circulation of slurry and acid conditions, an acid-resistant brick layer is formed by stacking bricks, which is excellent in acid resistance and abrasion resistance. As the bricks, various types of commercially available acid-resistant bricks can be used, and may be selected depending on the type of acid in question, the abrasion characteristics of the slurry, etc. As explained above, by installing the bottom portion B and the side portion S of the inner wall 50a of the autoclave 100, which are in contact with the solution L, with the acid-resistant brick layer, the abrasion resistance caused by the slurry in the solution can be increased and the manufacturing cost of the autoclave apparatus can be reduced.

[0069] The upper portion T of the inner wall 50a of the autoclave 100 may be provided with an acid-resistant metal layer 70. The acid-resistant metal layer 70 may be formed of stainless steel, titanium-clad (Ti-Clad) or the like, and has high acid resistance.

[0070] Generally, the upper part of the autoclave is arched and the bricks are stacked on it. Since the larger capacity autoclave has a larger radius of curvature of the upper part of the autoclave, it is more difficult to stack the acid-resistant bricks on the upper part of the high-capacity autoclave. In addition, due to the vibration of a mixer installed on the upper part of the autoclave, cracks may be formed in the acid-resistant brick layer stacked on the upper part, or the brick may be released and fall off the acid-resistant brick layer, which may collide with the high-speed stirring elements. For this reason, in the related art, the horizontal autoclave structure is the only way that can increase the processing capacity by increasing the length in the horizontal direction, while enabling the stability of the upper brick surface by reducing the radius of curvature of the brick layer stacked on the upper part.

[0071] According to embodiments of the present disclosure, by installing the acid-resistant metal layer 70 in the upper T section of the autoclave 100, where it is difficult to install the acid-resistant brick layer in the inner wall 50a of the autoclave 100, the risk of the upper brick falling off is substantially eliminated while maintaining the abrasion resistance of the slurry in the process solution. Furthermore, even if the autoclave space is not expanded horizontally, by increasing the autoclave diameter and vertical length, it is possible to achieve a stable operation of a large-capacity vertical autoclave, the implementation of which has not been tested in the past. For example, according to embodiments of the present disclosure, the inner diameter of the autoclave 100 may be at least about 5.5 meters or more.

[0072] According to embodiments of the present disclosure, by installing the acid-resistant layer 70 100 in the upper part T of the autoclave and causing a portion of the saturated water vapor in the gas phase portion G to condense and flow out as condensed water from the surface of the acid-resistant metal layer 70, not only does it avoid salt deposition on the inner wall 50a of the autoclave 100, but also dissolves a small amount of previously formed salt. Therefore, the operation rate of the apparatus can be improved.

[0073] The acid-resistant metal layer 70 may extend to an upper portion of the side portion S of the inner wall 50a. In addition, the acid-resistant metal layer 70 may extend between the inner wall 50a and the acid-resistant brick layer at the upper end of the side portion S of the inner wall 50a.

[0074] The process solution is introduced into the autoclave 100 through inlet port 10, 13, 15 or 17 and discharged out of the autoclave 100 through outlet port 20 or 25.

[0075] Referring to FIGS. 1A to 1C, the inlet port 10, 13, or 15 may be formed in the upper portion T of the inner wall 50a.

[0076] Referring to Figure 1A, the process solution input through the input port 10 can be the input of solution L through the gas phase section G.

[0077] Referring to FIG. 1B , the inlet port 13 extends into the autoclave 100, and one end of the inlet port 13 extending into the autoclave 100 can be positioned in the gas phase portion G without being immersed in the solution L. In addition, one end of the inlet port 13 may be positioned adjacent to the interface between the solution L and the gas phase portion.

[0078] In the autoclave of Figures 1A and 1B, since the incoming process solution is supplied to the gas phase section G through the inlet port 10 or 13 in a short time, no salt is produced.

[0079] Referring to FIG. 1C , the inlet port 15 extends into the interior of the autoclave 100 , and one end of the inlet port 15 extending into the interior of the autoclave 100 may be immersed in the solution L. In addition, one end of the inlet port 15 may be located in the vicinity between the solution L and the gas phase portion G. This can prevent the inlet port 15 from being bent or damaged by the mixed process solution even if the process solution (i.e., solution L) in the autoclave 100 is stirred at high speed.

[0080] Referring to FIG. 1D, the inlet port 17 may be formed in the side portion S of the inner wall 50a. That is, the end of the inlet port 17 may be located in the solution L. Accordingly, the process solution entering the autoclave 100 may not be supplied in the gas phase portion G.

[0081] In the autoclave of Figures 1C and 1D, the process solution inlet to the autoclave is not supplied to the gas phase section, so that salt can be generated at the inlet port and the inlet port can be protected from being blocked by salt.

[0082] Referring again to FIGS. 1A to 1D, the outlet port 20 or 25 may be formed in the side portion S of the inner wall 50a. The outlet port 20 or 25 is formed in the solution L of the autoclave 100 and therefore the process solution discharged from the autoclave 100 may not be supplied to the gas phase portion G. The outlet port 20 or 25 may also not extend into the interior of the autoclave 100. This prevents the outlet port 20 or 25 from being bent or damaged by the agitated process solution even if the process solution (i.e., solution L) in the autoclave 100 is agitated at a high speed.

[0083] Referring to FIG. 1D, both the inlet port 17 and the outlet port 25 are formed in the side portion S of the inner wall 50a, and the inlet port 17 is located at a higher position than the port 25.

[0084] According to embodiments of the present disclosure, since the process solution discharged from the autoclave does not enter the gas phase section, salt generation at the outlet port can be suppressed, and clogging of the outlet port by salt can be prevented.

[0085] The oxygen inlet port 30 is for introducing oxygen as an oxidizing agent for oxidizing the process solution (i.e., solution L), and the oxygen inlet port 30 may be formed in the lower portion B of the inner wall 50a. When oxygen is introduced through the lower portion of the autoclave 100, a sufficient residence time (or sufficient reaction time) of oxygen in the process solution can be obtained, so that the oxygen reaction efficiency can be improved.

[0086] An oxygen inlet line 30a is connected to the oxygen inlet port 30, and a high-pressure steam line 30b communicates with the oxygen inlet line 30a. The oxygen inlet flows through the oxygen inlet line 30a to the process solution through the oxygen inlet port 30. When a predetermined amount of oxygen is continuously introduced through the oxygen inlet port, the process solution does not return to the oxygen inlet port 30 and the oxygen inlet line 30a. However, while the autoclave is actually operating, a small amount of the process solution may enter the oxygen inlet port due to a change in the inlet pressure value, the inlet flow rate, or the like of oxygen. The inlet process solution is vaporized at the hot oxygen inlet port, and the dissolved components in the process solution are attached to the inner wall of the oxygen inlet port and block a pipe, preventing the entry of oxygen. If maintenance is required after the machine has stopped operating to clean the pipe, this may slow down the machine's operation.In the autoclave 100 according to the present disclosure, a high pressure steam line 30b is connected to the oxygen inlet line 30a so as to introduce a small amount of steam at a predetermined time interval such that the saturation phenomenon of the oxygen inlet pump can be destroyed by the re-entry of the reflux process solution into the autoclave 100 and the redissolution of the adhered salt by the water condensed from the steam.

[0087] Agitator 40 is provided to extend into autoclave 100 through upper portion T of inner wall 50a. Agitator 40 facilitates the reaction of the process solution by agitating solution L during the leaching process. Agitator 40 includes a first agitator blade 40a and a second agitator blade 40b, wherein first agitator blade 40a agitates the upper portion of solution L and second agitator blade 40b agitates the lower portion of solution.

[0088] Compared to a conventional apparatus, the autoclave 100 according to embodiments of the present disclosure is capable of providing a large capacity and is capable of improving the stability of the apparatus. The inner diameter of the autoclave 100 may be about 5.5 meters or more, and the inner volume of the autoclave 100 may be 150 cubic meters or more. Furthermore, during operation of the autoclave 100, the volume of the process solution (i.e., solution L) may be 100 cubic meters or more.

[0089] Additionally, the autoclave 100 according to embodiments of this disclosure may be used in the wet processing of a metal.

[0090] Figure 2 is an enlarged view of section A in autoclave 100 of Figure 1A.

[0091] Referring to Figure 2, a membrane layer 90 is provided between the inner wall 50a and the acid-resistant brick layer 60. The membrane layer 90 prevents the process solution within the autoclave 100 from flowing into the inner wall 50a and may include a waterproofing material.

[0092] On the inner wall side 50a, a cap ring 80 is provided to cover the upper portion of the acid-resistant brick layer. The cap ring 80 may be formed of the same material as the acid-resistant layer 70. The cap ring 80 is formed along the inner wall 50a of the autoclave 100 on the upper portion of the acid-resistant brick layer.

[0093] The upper end of the side portion S of the inner wall 50a may be installed with the acid-resistant metal layer 70, and the membrane layer 90 may be formed between the acid-resistant layer 70 and the acid-resistant brick layer 60 at the upper end of the side portion S of the inner wall 50a. In addition, the membrane layer 90 may be formed to extend between the upper end of the acid-resistant brick layer 60 and the cap ring 80.

[0094] The cap ring 80 and the acid-resistant metal layer 70 are connected to each other by a number of ribs 83. The ribs 83 serve as supports for supporting the cap ring 80 and may be made of the same material as the acid-resistant metal layer 70.

[0095] Cavities 85 may be formed between a plurality of lugs 83, the cap ring 80 and the acid-resistant metal layer 70. When a process is carried out using the autoclave 100, the internal temperature of the autoclave 100 may rise to 150°C or higher, and as a result, the acid-resistant brick layer may expand or contract. These cavities 85 are capable of preventing mechanical breakage of the cap ring 80 and the ribs 83 when the acid-resistant brick layer 60 expands or contracts.

[0096] Figure 3 is an enlarged view of an oxygen inlet port in an autoclave according to embodiments of the present disclosure.

[0097] Referring to Figure 3, the autoclave may include a cooling water passage 31 provided to surround the oxygen inlet port 30. Cooling water can flow through the cooling water passage 31 as needed.

[0098] In high temperature and acidic conditions, corrosion of the autoclave may be accelerated. The cooling water passage 31 is capable of reducing the temperature of the oxygen inlet pump 30 by heat exchange through the inlet and outlet of the cooling water. As a result, the cooling water passage 31 may reduce corrosion of the autoclave around the oxygen inlet port 30.

[0099] Figures 4A to 4D are views illustrating a method for removing salt generated in an autoclave, according to embodiments of the present disclosure. For ease of explanation, a salt removal method will be described with reference to the autoclave 100 described with reference to Figure 1A. However, a person of ordinary skill in the art can understand that the salt removal method according to embodiments of the present disclosure is also applicable to the autoclaves 100 with reference to Figures 1B to 1D.

[0100] Referring to FIG. 4A, the SL salt may be produced in the autoclave 100 as a natural process used with the autoclave 100. The SL salt may be produced when a portion of the process solution is evaporated and thus may be produced primarily in the vicinity of the IF interface between the solution L and the gas phase portion G. For example, the SL salt may be produced at the surface of the acid-resistant brick layer 60 or at the surface of the mixer 40 near the IF interface between the solution L and the gas phase portion G. The produced SL salt may be soluble in water. The IF surface of the solution L in the autoclave 100 during the natural process may be defined as the first surface.

[0101] Referring to FIG. 4B , the IF level of solution L in autoclave 100 is increased to a second level above the first level so that the produced salt SL may be immersed in solution L. For example, the increased IF level of solution L may be accomplished by entering process solution into autoclave 100 through inlet port 10, while avoiding discharge of process solution from autoclave 100 by blocking outlet port 20. As another example, the increased IF level of solution L may be accomplished by increasing the amount of process solution entering through inlet port 10 from the amount of process solution discharged through outlet port 20.

[0102] The increased level (i.e., the second level) of the IF of the solution L is set lower than the upper level of the acid-resistant brick layer 60. Therefore, even if the IF level of the solution L is increased to the second level, the solution L may not come into contact with the acid-resistant metal layer 70, and damage to the acid-resistant metal layer 70 by the slurry in the solution L can be prevented.

[0103] The increased level (i.e., the second level) of IF solution L may be located below the lower level of the cap ring 80. Therefore, even if the IF level of solution L is increased to the second level, solution L may not contact the cap ring 80, preventing damage to the cap ring 80 by the slurry in solution L.

[0104] Referring to Figure 4C, the salt SL is removed by maintaining the surface IF of the solution L at a second surface for a predetermined period of time. The water-soluble salt SL can be dissolved and removed from the solution L as it remains immersed in a solution L for a predetermined period of time. For example, the surface of the solution L may be maintained at a second surface for about 1 hour to about 6 hours.

[0105] Referring to Figure 4D, after the salt SL is removed, the IF level of the solution L is reduced to a level in a natural process (i.e., the first level). The natural process using the autoclave 100 may then be repeated.

[0106] As described above, according to embodiments of the present disclosure, salt can be removed from the autoclave 100 by a simple method of raising the level of solution L and maintaining the level for a predetermined period of time without removing the process solution in the autoclave 100. Therefore, the operational efficiency of the autoclave 100 can be improved.

[0107] Figure 5 is a schematic diagram illustrating a structure in which autoclaves are connected in series according to embodiments of the present disclosure.

[0108] Referring to Figure 5, a first autoclave 100a and a second autoclave 100b are connected in series. The first autoclave 100a may be one of the autoclaves described with reference to Figures 1A to 1C. The second autoclave 100b may be the autoclaves described with reference to Figure 1D.

[0109] When the first and second autoclaves 100a and 100b are operating, the process solution may be introduced through the inlet port 10 of the first autoclave 100a and may be supplied to the reaction process in the first autoclave 100a. The process solution supplied to the reaction process in the first autoclave 100a may be introduced into the second autoclave 100b through a first connecting pipe 110 and may be supplied to the reaction process. The upstream side of the first connecting pipe 110 corresponds to the outlet port 20 of the first autoclave 100a, and the downstream side of the first connecting pipe 110 may be connected to the inlet port 10 of the second autoclave 100b.

[0110] When the first and second autoclaves 100a and 100b are operating, the outlet port 20 of the first autoclave 100a is immersed in the solution L in the first autoclave 100a, and the inlet port of the second autoclave 100b is immersed in the solution L of the second autoclave 100b. Therefore, the process solution entering from the first autoclave 100a to the second autoclave 100b through the first connecting pipe 110 may not be supplied to the gas phase portion G. Therefore, the generation of salt in the first connecting pipe 110 can be prevented.

[0111] The first autoclave 100a may be mounted at a position higher than the second autoclave 100b. For example, the first autoclave 100a may be mounted at a position from about 10 centimeters to about 100 centimeters higher than the second autoclave 100b. This may allow the process solution to flow from the first autoclave 100a to the second autoclave 100b while preventing the backflow of the process solution from the second autoclave 100b to the first autoclave 100a.

[0112] One or more flash tanks (flash vessels) 200a and 200b may be connected to the outlet port 20 of the second autoclave 100b. For example, as shown in FIG. 5, a first flash tank (flash vessel) 200a and a second flash tank (flash vessel) 200b may be connected to the second autoclave 100b in series. The first flash tank (flash vessel) 200a may be connected to the second autoclave 100b via a connecting pipe 120, and the second flash tank (flash vessel) 200b may be connected to the first flash tank (flash vessel) 200a via a third connecting pipe 130.

[0113] The high pressure process solution discharged from the second autoclave 100b may be compressed by the first and second flash tanks (flash vessels) 200a and 200b. For example, the high pressure process solution discharged from the second autoclave 100b may be compressed to atmospheric pressure by the first and second flash tanks (flash vessels) 200a and 200b.

[0114] In Figure 5, two autoclaves 100a and 100b and two flash tanks (flash vessels) 200a and 200b are connected in series, but the present disclosure is not limited thereto. For example, only one flash tank (flash vessel) may be connected to the outlet port 20 of the second autoclave 100b, or three or more flash tanks (flash vessels) may be connected to the outlet port 20. In addition, the various types of autoclaves described above may also be further connected in series between the second autoclave 100b and the first flash tank (flash vessel) 200a.

[0115] Next, a zinc process performed using an autoclave according to embodiments of this disclosure will be described.

[0116] In general, in the zinc process, iron (Fe) and copper (Cu) are leached together with sulfuric acid in the leaching process of zinc raw materials into sulfuric acid (=acid washing) and the iron in the Fe(III) state present in the leaching solution is reduced to Fe(II) using a reducing agent such as concentrated zinc. The remaining sulfuric acid in the reduced solution is neutralized to a more neutral pH using a neutralizing agent such as calcine and then fed to a solid-liquid separation to obtain a neutral zinc sulfate solution.

[0117] A significant amount of Fe(II) is dissolved in a neutral zinc sulfate solution and fed to an iron removal process to remove iron.

[0118] Copper in an iron removal process solution is separated by solid-liquid separation, and then a reducing agent is added thereto so that copper (Cu) in the form of dissolved copper sulfate (CuSO4) is reduced and precipitated as (Cu) cement, which is copper metal powder, thereby removing copper. However, in the above-mentioned iron removal process, components such as Cu (II) in the process solution act as catalysts to accelerate the oxidation of Fe (II) to Fe (III) in the iron precipitation reaction to facilitate the production of jarosite. Therefore, higher temperatures and higher pressures are required to precipitate iron from the zinc sulfate solution in the form of hematite.

[0119] The present disclosure aims to reduce the reaction temperature and pressure of the iron precipitation process to a lower level than the related art. To reduce the reaction temperature and pressure, it is necessary to neutralize a zinc sulfate solution so that the catalyst components are removed. Furthermore, when even a small amount of Fe (III) is present in the solution, this is the condition under which jarosite precipitates. Therefore, it is necessary to completely reduce Fe (III) to Fe (II) in the zinc sulfate solution to enter the iron precipitation process.

[0120] Figure 6 is a flowchart that discloses a process for recovering hematite according to the present embodiments.

[0121] In the zinc process, a zinc sulfate solution is prepared by leaching zinc-containing raw materials, such as zinc concentrate, a calcine produced by roasting zinc concentrate, or zinc ferrite, in sulfuric acid at atmospheric pressure. The sulfuric acid remaining in the leaching process is first neutralized using calcine so that its impurities are removed. The iron components leached together in the leaching process of the raw materials do not precipitate in the neutralization process, and therefore the iron components remain in the process solution after neutralization.

[0122] Referring to Figure 6, a zinc sulfate solution is fed to a conditioning process as an input solution to the conditioning process. In the conditioning process, the input solution to the conditioning process is fed to a conditioning reactor 1 and discharged as an air cake in a filter 3 using a thickener 2, and the post-airing process solution is transferred to the iron precipitation process so as to be fed to the iron precipitation process as an input solution.

[0123] In the iron precipitation process, the iron precipitation process input solution is fed to the iron precipitation reactor 4, the solid portion is separated as hematite through the thickener 5 and filter 6, and the solution is transferred to the neutralization process as a post-iron precipitation process solution.

[0124] In the present disclosure, catalyst components such as copper are removed by using a reducing agent in the neutralization process inlet solution to recover iron as hematite at a lower temperature and pressure than conventional methods, and the conditioning process is used to reduce the Fe(III) present in small amounts to Fe(II).

[0125] The aeration process includes a reduction step which is carried out by introducing a reducing agent, the oxidation-reduction potential (ORP) of the post-aeration process solution is adjusted by the type and amount of reducing agent input. In addition, the reducing agent is introduced into the aeration reactor 1 where the aeration process input solution is introduced.

[0126] The post-aeration process solution is the input solution to the iron precipitation process, which is the next process.

[0127] In this disclosure, the oxidation-reduction potential of the iron process inlet solution is adjusted to -100 mV or less. Specifically, the oxidation-reduction potential is adjusted to -400 mV or less. When the oxidation-reduction potential is higher than -100 mV, a jarosite is partially mixed and therefore the iron content of the iron precipitation cake may be reduced to less than 50%. When the oxidation-reduction potential is higher than -100 mV, higher temperature and higher pressure conditions are required to produce hematite.

[0128] Conversely, when the redox potential is -100 mV or less, the reduction space is dominant and hematite may be produced at lower temperatures and pressures than when the redox potential is higher than -100 mV. In this case, the iron content of the iron precipitate may be 50% or more.

[0129] When the oxidation-reduction potential is -400 mV or lower, finer hematite is produced at relatively low temperatures and low pressures.

[0130] In order to further reduce the oxidation-reduction potential, the input amount of reducing agent may be increased, so that the oxidation-reduction potential can be adjusted according to economic efficiency.

[0131] The pH of the input solution to the iron precipitation process is adjusted to about 3 to 5.5.

[0132] When the pH of the iron precipitation process inlet solution is less than 3, the sulfuric acid in the air conditioning process inlet solution reacts with the reducing agent, resulting in an increase in the amount of reducing agent used. When the pH is greater than 5.5, zinc precipitates in the form of zinc sulfate salt (nZn(OH)2·mZnSO4), resulting in zinc loss in the process solution, and the precipitated zinc salt can adhere to the device in the iron precipitation process, reducing the performance of the device.

[0133] The amount of reducing agent input may vary depending on the composition of the conditioning process inlet solution, such as the concentration of Fe (III) and copper (Cu) present in the conditioning process inlet solution. The amount of reducing agent input can be determined depending on the value of the oxidation-reduction potential (ORP).

[0134] As the reducing agent, an inorganic reducing agent such as zinc or aluminum powder or an organic reducing agent can be used. Zinc powder is a good reducing agent because of its very good reducing power. When a concentration of zinc having a weak reducing power is used as a reducing agent, unlike the present disclosure, the ORP value decreases to a level of about 200 mV and cannot be adjusted to zero mV or less.

[0135] Components such as copper present in the feed solution of the conditioning process are precipitated in the form of copper cement containing high amounts of copper in the conditioning process and discharged as a prepared cake. Therefore, after the conditioning process, the feed solution is subjected to solid-liquid separation, copper can be recovered in a copper recovery process. According to the present disclosure, copper cement can be obtained as a by-product in a conditioning process, which is a pre-processing step of the iron precipitation process.

[0136] A post-aeration process solution is transferred through this process to the precipitation process to produce the iron contained therein in the form of hematite.

[0137] The iron deposition process includes a pre-pressurization step and oxidation with oxygen and steam.

[0138] The zinc concentration in the iron precipitation process inlet solution is adjusted to about 120 to 150 g / L. When the zinc concentration in the iron precipitation process inlet solution is more than 150 g / L, zinc sulfate monohydrate (ZSM) salt may be produced at a temperature between 135 and 150°C, which is the temperature condition of the iron precipitation process in the present disclosure. When the zinc concentration in the iron precipitation process inlet solution is less than 120 g / L, the scale of a plant must be increased to produce the same amount of zinc, which is not desirable due to the plant operation cost and plant investment cost.

[0139] The iron concentration of the iron precipitation process inlet solution is adjusted to 5 to 20 g / L. Although it is not a problem even at low iron concentrations in terms of hematite production and quality, while the iron concentration in the iron precipitation process inlet solution is less than 5 g / L, this process is not economical in terms of operational efficiency. When the iron concentration in the post-aeration process solution is higher than 20 g / L, the acid concentration in the process solution after the iron precipitation reaction increases, resulting in a decrease in the iron precipitation rate. Therefore, as jarosite is produced, the iron content in the iron precipitate may decrease.

[0140] The high-temperature, high-pressure pressing and oxidation step in the iron deposition step can be performed using an autoclave.

[0141] In this disclosure, even if a zinc sulfate solution having a high zinc concentration of about 120 to 150 g / L in the process solution is used in the iron precipitation step using an autoclave, the recovered iron is recovered as hematite at a temperature in the range of 135°C to 150°C and at a pressure of about 5 to 10 barg, which is lower than the temperature and pressure in the related art. In a preferred embodiment, the autoclave processing time for iron recovery is about 30 minutes to 3 hours. The iron precipitation process of the present disclosure is capable of recovering hematite of excellent quality at a lower temperature and pressure than the related art, even when a conventional horizontal autoclave is used. However, when the described high-precision vertical autoclave is used, since the process is carried out at a lower temperature and lower pressure than related techniques, stability in the part where the acid-resistant brick lining and the acid-resistant metal lining of the inner wall of the autoclave are in contact with each other or the like can be safer.

[0142] When the pressure inside the autoclave is less than 5 barg, the partial pressure of oxygen inside the autoclave is reduced by 2 barg or less, and the iron removal rate is reduced. Meanwhile, when the pressure inside the autoclave is more than 10 barg, it is necessary to increase the pressure of the oxygen and zinc solution supplied to the autoclave to 13 barg or higher, which is higher than the pressure inside the autoclave, which may increase the investment cost of the device.

[0143] When the temperature inside the autoclave is less than 135°C, jarosite begins to form as an iron precipitate, and the iron content in the iron precipitate may decrease to less than 50%. When the temperature inside the autoclave is higher than 150°C, it has no effect on the production of hematite. However, the saturated zinc in the process solution precipitates as zinc sulfate monohydrate, resulting in an increase in the zinc content in the iron precipitate and a decrease in the relative iron content. In addition, zinc sulfate monohydrate may adhere to the inner wall of the autoclave or a pipe in the form of salt, which may cause problems in the facility. Considering the reduction in zinc recovery due to the precipitation of zinc sulfate monohydrate, the temperature range inside the autoclave is about 135 to 150°C.

[0144] Furthermore, at temperatures of about 60°C or higher, the solubility of zinc sulfate decreases with increasing temperature. In the related art, the temperature range for producing hematite is about 180°C or higher, but according to the present disclosure, hematite can be produced at temperatures of about 135 to 150°C.

[0145] Thus, according to the present disclosure, the zinc concentration in the process inlet solution can be increased by performing the iron recovery process as hematite at a lower temperature than related techniques. By maintaining a zinc concentration higher than related techniques, the scale of the zinc production plant can be reduced and operating costs can be reduced by facilitating the operation.

[0146] In addition, hematite produced in the iron precipitation process may be separated from the zinc sulfate solution via concentrator 5 and filter 6 and may be introduced into the iron precipitation process in the form of granules.

[0147] Therefore, the present disclosure solves problems such as degraded operating efficiency and increased equipment wear due to increased solid particles in the process solution, which may arise when the produced hematite is reintroduced into the iron precipitation process as grains.

[0148] In the following, the content of embodiments of the present disclosure will be described in detail.

[0149] Example 1

[0150] In Example 1, using a zinc sulfate solution prepared by adjusting the ORP by varying the amount of zinc powder input to each neutralization conditioning process input solution, i.e., a zinc sulfate leaching solution, the efficiency of the iron precipitation reaction was observed depending on the ORP value under reaction conditions of 140°C and 7 barg in an autoclave. When zinc powder is introduced, the ORP of the zinc sulfate solution is further reduced and Fe(II) becomes more stable in the process. The iron precipitation reaction in Example 1 was carried out without introducing hematite grains.

[0151] The efficiency of the iron precipitation reaction was observed using a zinc sulfate solution whose ORP was adjusted to be in the range of +200 to -400 mV (vs. Ag / AgCl) when a silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode and under reaction conditions of 140°C and 7 barg. The ORP in the conditioning process was analyzed by varying the input amount of zinc powder and the iron content in the iron precipitates using ICP-AES spectroscopy.

[0152] Table 1 Example 1 Comparative Example 2 Comparative Example 1 Invention Example 2 Invention Example 3 Invention ORP (mV) +200 0 -100 -200 -400 Percent iron in sediment 35.3 45.4 52.1 55.9 56.6 Jarosite sediment ○ △ Ⅹ Ⅹ Ⅹ

[0153] Table 1 shows the iron precipitation behavior with respect to the ORP value according to Example 1. According to Table 1, in the case of a zinc sulfate solution not subjected to the conditioning process (Comparative Example 1), the iron precipitate was precipitated as yellow jarosite and the iron content was very low, i.e. 35.3%. On the other hand, when the zinc sulfate solution was subjected to the conditioning condition, i.e., using an ORP of 0 mV (vs. Ag / AgCl) or less, the iron content was 45.4% and it was possible to obtain hematite containing a small amount of jarosite. Under the ORP condition of -100 mV (vs. Ag / AgCl) or less, hematite with an iron content of 52% or more could be obtained.

[0154] Example 2

[0155] In Example 2, the efficiency of the iron precipitation reaction was observed depending on the reaction temperature in the temperature range of 120°C or higher using a zinc sulfate solution containing 145 g zinc / liter under a pressure of 7 barg. The iron precipitation reaction in Example 2 was carried out without introducing hematite grains.

[0156] The ORP was adjusted to -400 mV (vs. Ag / AgCl) using zinc powder as a reducing agent, a zinc sulfate solution having a zinc concentration of 145 g / L, an iron concentration of 12.4 g / L and a pH of 4.5 was introduced into an autoclave, the reaction was carried out for 2 hours, in which the reaction temperature was adjusted to 120-160°C at a pressure of 7 barg and then the temperature was reduced to room temperature. The post-reaction solution containing hematite was supplied to solid-liquid separation by a vacuum purifier, and the iron content in the iron precipitate was analyzed quantitatively using ICP-AES spectroscopy.

[0157] Table 2 Comparative Example 3 Comparative Example 4 Invention Example 4 Invention Example 5 Invention Example 6 Comparative Example 5 Temperature (°C) 120 130 135 140 150 160 Iron after-reaction solution (g / l) 2.1 1.6 0.7 0.5 0.4 0.4 Sulfuric acid (g / l) 14.3 19.2 20.9 21.2 21.5 21.5 Iron in precipitate (%) 38.7 45.3 55.7 56.6 57.7 58.4 Iron precipitation rate (%) 83.1 87.1 94.4 96.0 96.8 96.8 Jarosite production ○ △ Ⅹ Ⅹ Ⅹ ZSM production Ⅹ Ⅹ Ⅹ Ⅹ Ⅹ ○

[0158] Table 2 shows the iron precipitation behavior depending on the reaction temperature according to Example 2. Referring to Table 2 and Figure 7, iron was precipitated in the form of a yellowish-brown powder at 120°C, and the crystal structure of the precipitate obtained was analyzed by X-ray diffraction (XRD). As a result, it was observed that jarosite was formed. At 130°C, most of the iron precipitated as hematite, but in a form associated with jarosite. At temperatures higher than 135°C, hematite having an iron content of 55% or more was obtained regardless of the reaction temperature. However, at 160°C, the solubility of zinc sulfate in the reaction solution decreased significantly, and the supersaturated zinc content precipitated and adhered to the inner wall and the end of the autoclave. The adhered precipitate crystal was observed using X-ray diffraction analysis and the precipitates were found to be zinc sulfate monohydrate (ZSM, ZnSO4H2O) as seen in Figure 8. The deposited ZSM may adhere to the inside of pipes and devices, which may reduce the power of the device.

[0159] Therefore, when the zinc concentration in the zinc sulfate solution is 145 g / L, iron may be precipitated and recovered in the zinc sulfate solution in the form of hematite at a temperature of 135°C or higher under a pressure of 7 barg.

[0160] Example 3

[0161] The ORP was adjusted to -400 mV (vs. Ag / AgCl) with zinc powder as a reducing agent, a zinc sulfate solution containing a zinc concentration of 145 g / L, an iron concentration of 12.4 g / L and a pH of 4.5 was introduced into the autoclave and the reaction was carried out for 2 hours, in which the pressure was adjusted by applying oxygen to 5 to 15 barg at 145°C, and then the temperature was reduced to room temperature. The iron precipitation reaction in Example 3 was carried out without introducing hematite grains.

[0162] Table 3 Comparative Example 6 Invention Example 7 Invention Example 8 Invention Example 9 Invention Example 10 Invention Example 11 Pressure 3 barg 5 barg 7 barg 8 barg 10 barg 15 barg Iron after-reaction solution (g / l) 3.5 1.2 0.5 0.5 0.4 0.4 Sulfuric acid (g / l) 17.1 21.2 21.2 21.5 22.1 22.3 Percentage of iron in sediment 49.2 50.1 56.6 56.9 57.2 58.2 Percentage of iron deposition 71.8 90.3 96.0 96.1 96.8 97.1 Jarosite production Ⅹ Ⅹ Ⅹ Ⅹ Ⅹ Ⅹ ZSM production Ⅹ Ⅹ Ⅹ Ⅹ Ⅹ Ⅹ Ⅹ

[0163] Table 3 relates to the pressure-dependent iron precipitation behavior according to Example 3. According to Table 3, hematite having an iron content of 50% or more is obtained in iron precipitates at a pressure of 5 barg or more. In the disclosure of Examples 1 to 3, the iron precipitation process was carried out in a state in which no hematite seeds were introduced. It was observed that hematite was formed at the temperature (from about 135 to 150°C) and relatively low process pressure (about 5 to 10 barg), even if no hematite seeds were introduced.

[0164] Figure 9 is a diagram of an installation of an autoclave apparatus according to embodiments of the present disclosure.

[0165] Referring to FIG. 9, an autoclave apparatus includes first and second autoclaves 100a and 100b configured to admit oxygen therein to oxidize Fe(II) contained in a zinc sulfate solution to produce hematite, first and second flash means 200a and 200b configured to depressurize a high-pressure reaction solution discharged from the second autoclave 100b to atmospheric pressure, and a cooler 300 configured to cool a compressed zinc sulfate solution having a temperature of about 100°C compressed in the first and second flash means 200a and 200b, so that the compressed zinc sulfate solution is filtered using a filter press. The structure in which the first and second autoclaves 100a and 100b and the first and second flash means 200a and 200b are connected is substantially the same as that described in FIG.

[0166] The process solution is initially heated as a heat exchange solution from the cooler 300 and then heated by the first and second heaters 310 and 320 using the steam recovered in the first and second heaters 310 and 320. Thereafter, the process solution is heated to a final reaction temperature in a heat exchanger 330 configured for heat exchange using steam and then fed into the first autoclave 100a.

[0167] In the present embodiment, the flash tank (flash vessel) is configured to be divided into a first flash tank (flash vessel) 200a and a second flash tank (flash vessel) 200b in order to improve the thermal efficiency when the process solution is heated by the steam generated in the flash tank (flash vessel). At this time, the generated steam may reduce the energy loss by directly heating the process solution using the first heater 310 and the second heater 320, which are respectively connected to the first flash tank (flash vessel) 200a and the second flash tank (flash vessel) 200b. As described above, in the present embodiment, by providing the process solution to the autoclave through three heating steps, 90% or more of the energy of the process solution discharged from the autoclave may be recovered, and thus the amount of steam used to maintain the reaction temperature at a high temperature may be reduced by 80% or more.

[0168] While the present disclosure has been described in connection with certain embodiments thereof, it is to be understood that one of ordinary skill in the art can make various changes and modifications therein without departing from the spirit and scope of the present disclosure. It is also to be understood that such changes and modifications fall within the scope of the claims appended hereto.

Claims

claims 1. A vertical autoclave comprising an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet port through which oxygen is supplied to the process solution, an agitator configured to mix the process solution, an inner wall, an acid-resistant brick layer lined on a lower portion and a side portion of the inner wall, and an acid-resistant metal layer lined on an upper portion of the inner wall, wherein the acid-resistant brick layer does not extend onto the upper portion of the inner wall such that the upper portion of the inner wall is not lined with the acid-resistant brick layer.

2. The vertical autoclave of claim 1, wherein the vertical autoclave has an inner diameter of 5.5 m or more.

3. The vertical autoclave of claim 1, wherein the vertical autoclave has an inner volume of 150 m3 or more.

4. The vertical autoclave of claim 1, wherein a volume of the process solution is 100 m3 or more when the vertical autoclave is operated.

5. A vertical autoclave comprising: an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet port through which oxygen is supplied to the process solution, an agitator configured to mix the process solution, an inner wall, an acid-resistant brick layer lined on a lower portion and a side portion of the inner wall, an acid-resistant metal layer lined on an upper portion of the inner wall, and a cap ring which covers an upper portion of the acid-resistant brick layer on the side portion of the inner wall.

6. The vertical autoclave of claim 5, further comprising a membrane layer provided between the inner wall and the acid-resistant brick layer, wherein the membrane layer is provided to extend between the upper portion of the acid-resistant brick layer and the cap ring.

7. The vertical autoclave of claim 5, further comprising a plurality of ribs which connect the cap ring and the acid-resistant metal layer.

8. The vertical autoclave of claim 7, wherein the cap ring and the plurality of ribs are formed of a same material as the acid-resistant metal layer.

9. The vertical autoclave of claim 7, wherein voids are formed among the plurality of ribs, the cap ring, and the acid-resistant metal layer.

10. The vertical autoclave of claim 1, wherein the inlet port is disposed in the upper portion of the inner wall, and the outlet port is disposed in the side portion of the inner wall.

11. The vertical autoclave of claim 10, wherein the inlet port extends to an inside of the vertical autoclave, and when the vertical autoclave is operated, an end of the inlet port is immersed in the process solution.

12. The vertical autoclave of claim 1, wherein the inlet port and the outlet port are disposed in the side portion of the inner wall, and the inlet port is disposed at a position higher than the outlet port.

13. A vertical autoclave comprising: an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet port through which oxygen is supplied to the process solution, an agitator configured to mix the process solution, an inner wall, an acid-resistant brick layer lined on a lower portion and a side portion of the inner wall, and an acid-resistant metal layer lined on an upper portion of the inner wall,wherein the oxygen inlet port is disposed in the lower portion of the inner wall, and the vertical autoclave further includes: an oxygen inlet line connected to the oxygen inlet port; and a cooling water passage disposed to surround the oxygen inlet port.

14. The vertical autoclave of claim 13, further comprising a high-pressure steam line communicating with the oxygen inlet line, wherein steam is supplied through the high-pressure steam line to the oxygen inlet port.

15. The vertical autoclave of claim 1, wherein, when the vertical autoclave is operated, a water level of the process solution in the vertical autoclave is adjusted to be lower than an upper portion of the acid-resistant brick layer provided on the side portion of the inner wall.

16. The vertical autoclave of claim 1, wherein the acid-resistant metal layer is lined to extend to an upper end of the side portion of the inner wall.

17. The vertical autoclave of claim 16, wherein, at the upper end of the side portion of the inner wall, the acid-resistant metal layer extends between the inner wall and the acid-resistant brick layer.

18. An autoclave apparatus comprising a first autoclave and a second autoclave, which are connected in series, wherein each of the first autoclave and the second autoclave is a vertical autoclave comprising an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet port through which oxygen is supplied to the process solution, an agitator configured to mix the process solution, an inner wall, an acid-resistant brick layer lined on a lower portion and a side portion of the inner wall, and an acid-resistant metal layer lined on an upper portion of the inner wall, wherein the acid-resistant brick layer does not extend onto the upper portion of the inner wall such that the upper portion of the inner wall is not lined with the acid-resistant brick layer.

19. The autoclave apparatus of claim 18, further comprising a connection pipe which connects the first autoclave and the second autoclave to each other, wherein an upper stream side of the connection pipe corresponds to the outlet port of the first autoclave, and a lower stream side of the connection pipe corresponds to the inlet port of the second autoclave.

20. The autoclave apparatus of claim 19, wherein, when the first autoclave and the second autoclave are operated, the outlet port of the first autoclave is immersed in a solution in the first autoclave, and the inlet port of the second autoclave is immersed in a solution in the second autoclave.

21. The autoclave apparatus of claim 18, wherein the first autoclave is installed at a position higher than the second autoclave.

22. The autoclave apparatus of claim 18, further comprising at least one flash vessel connected to the outlet port of the second autoclave.

23. A method of removing salt from an autoclave, the method comprising: raising a surface level of a solution in the autoclave from a first level to a second level such that salt in the autoclave is immersed in the solution; and maintaining the surface level of the solution at the second level, wherein the salt is dissolved in the solution while the surface level of the solution is maintained at the second level.

24. The method of claim 23, wherein the salt is water-soluble.

25. The method of claim 23, wherein the process of maintaining the surface level of the solution at the second level is performed for one hour to six hours.

26. The method of claim 23, further comprising lowering the surface level of the solution from the second level to the first level.

27. The method of claim 23, wherein the autoclave is a vertical autoclave comprising an inlet port through which a process solution is introduced, an outlet port through which the process solution is discharged, an oxygen inlet port through which oxygen is supplied to the process solution, an agitator configured to mix the process solution, an inner wall, an acid-resistant brick layer lined on a lower portion and a side portion of the inner wall, and an acid-resistant metal layer lined on an upper portion of the inner wall.

28. The method of claim 27, wherein the second level is lower than an uppermost surface level of the acid-resistant brick layer.

29. The method of claim 27, wherein the autoclave further comprises a cap ring which covers an upper portion of the acid-resistant brick layer on the side portion of the inner wall.

30. The method of claim 29, wherein the second level is lower than a lowermost surface level of the cap ring.

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