JP2005527767A - How to get argon by cryogenic air decomposition - Google Patents

Abstract

The present invention relates to a method for obtaining argon by cryogenic decomposition of air. The rectification device (2, 4) has at least one air decomposition column (4), and a separation wall (5) extending in the longitudinal direction of the column is formed in the first part and the second part (6, 7). Divide. A fluid (3) having oxygen and argon is introduced into the first part (6). A stream (13) with oxygen and argon is withdrawn from the second part (7) with an argon concentration of 15-50%.

Description

  The present invention relates to a method for obtaining argon by cryogenic decomposition of air in a rectifying apparatus having three rectifying parts arranged in a row, wherein the first and second rectifying parts and the second and third rectifying parts are obtained. The parts are connected to each other on the gas side and the liquid side, respectively, and the second rectifying part has two parts, which are not connected to each other on the gas side and the liquid side, flow in parallel, A fluid with oxygen and argon is introduced into one part and a stream with oxygen and argon is taken from the second part of the two parts.

  The boiling point of argon is between the boiling point of oxygen and the boiling point of nitrogen. Argon accumulates in the middle part of the low-pressure column in the classical air cryogenic decomposition by two-stage rectification. In order to acquire argon, generally a gaseous part is taken out from this part, and a gaseous part mainly consists of oxygen and argon. The portion in which about 10% argon is accumulated is supplied to a so-called crude argon column, where oxygen and argon rectifiers are separated. Argon can be evacuated at the top of the crude argon column, liquid having mainly oxygen at the bottom can be collected, and liquid can be returned to the low pressure column.

  In practice, argon purity often higher than 95% is required. In a known manner, a crude argon column is fed with a stream having only about 10% argon. Since this stream can be concentrated to the desired high argon purity and the desired amount of product can be removed at the head of the crude argon column, a significant amount of steam must be introduced into the crude argon column where it must be rectified. Don't be. The cross section of the crude argon column must be chosen considerably larger, which results in considerable input costs.

  In particular, it is already known from the field of hydrocarbon acquisition to use so-called separation wall columns to crack ternary mixtures. In the case of a separation wall column, a part of the column is divided into two parts by a wall arranged in the longitudinal direction of the column. On the upper and lower sides of the separation wall, the two parts are joined together on the flow side. In the implementation of the corresponding method, the ternary mixture introduced into a part of one face of the separation wall can be broken down into three parts with a single column. The most easily boiled component can be obtained from the top of the separation wall column, the medium boiling component from the side opposite the separation wall feed, and the least boiled component from the bottom. Higher concentrations of mesoboiling components can be obtained at the side outlet using a separation wall column compared to a column without a separation wall.

  In cryogenic air decomposition, separation wall columns have hitherto been rarely used due to their difficult adjustments. European Patent (EP-B1) No. 0638778 describes a method for cryogenic decomposition of air in a separation wall column. The low pressure column is separated by a separation wall in the middle part. The reservoir liquid is supplied from the pressure column to one side of the separation wall, and the argon-containing fluid is taken out from the other side of the separation wall. In order to improve the control of the process, the waste stream is removed in the face of the separation wall into which the pool liquid is introduced. The process parameters are selected such that the resulting argon-containing fluid has an argon concentration of at least 70%.

  If a product with an argon concentration in the range of 70% is required, the method described in European Patent (EP-B1) 0638778 is used to reduce the number of theoretical shelves in the crude argon column. The height can be saved. However, if an argon concentration higher than 95%, for example, is required, the advantage of concentrating to a value of argon higher than 70% of the fluid discharged from the low pressure column and fed to the crude argon column is always reduced. This is due to the need for a large number of theoretical shelves in the crude argon column to remove the final percentage of oxygen from the argon in order to achieve a high argon concentration. That is, in the case of a high purity requirement, the starting concentration of the fluid introduced into the crude argon column plays a role.

  The object of the present invention is therefore to show an improved method of obtaining argon by low temperature aerolysis.

  The object is that according to the invention, the concentration of argon in the stream discharged from the second part is 15 to 50%, preferably 15 to 40%, particularly preferably 20 to 35%, according to the method of the type described at the outset. It is solved by being.

  The present invention is based on the recognition that increasing the starting concentration of argon in a stream introduced to a crude argon column with a constant amount and purity of argon product results in a decrease in the amount of vapor supplied in excess. This is advantageous as long as the crude argon column has a correspondingly reduced cross section, saving costs.

  However, increasing the argon concentration at the side outlet of the air cracking column is associated with complex implementation and costly adjustment of the air cracking column. It should be taken into account that the advantage of argon concentration at the side outlet from the air cracking column is always reduced in the case of higher product demands, as described above, in this case the theoretical shelf in the crude argon column. This is because the number of plates depends substantially on the final concentration achieved and not on the starting concentration.

  Tests have shown that the minimum amount of vapor that must be supplied to a regular function in a crude argon column first decreases with increasing argon concentration, but remains constant from 50% argon concentration. That is, the subsequent argon accumulation at the side outlet to a value higher than 50% does not further reduce the amount of vapor introduced into the crude argon column, and therefore does not give rise to the possibility of subsequent cross-sectional reduction of the crude argon column. Only the advantage of high argon concentration in the mixture fed to the crude argon column is maintained. Since the number of theoretical shelves in the crude argon column is substantially independent of the starting concentration when the argon purity requirement is high, the subsequent increase in the argon concentration in the stream removed from the air cracking column is no longer important. This situation has been studied in detail within the framework of the present invention and it has been found that an argon concentration of 15-50% in the stream withdrawn from the second part is particularly advantageous.

  In practice, it has been found that the implementation of a process for removing a stream having an argon concentration of 15 to 40%, preferably 20 to 35%, from the second part has particular advantages.

  The present invention is particularly advantageous when a separation wall column is used. In this case, the rectification device has at least one air cracking column, which has three rectification sections arranged in one row, with the rectification sections adjacent to each other on the gas side and liquid side, respectively. Are connected to each other. The middle rectifying part has one separating wall, which separates the rectifying part into two parts. Gas exchange and liquid exchange between the two parts by the separation wall are prevented inside the second rectification part. However, the two parts are joined on the flow side with the rectifying part present above and below it.

  Instead of a separation wall column, it can be divided into two parallel flow-through parts by two columns arranged parallel to each other. The liquid is discharged from the first air decomposition column at an intermediate position and supplied to the second column. Gas is withdrawn from the first air decomposition column at the second intermediate position and introduced into the second column. The gas produced at the head of the second column and the liquid from the second column pool are preferably returned to the first air cracking column at two intermediate positions. The part separated on the two flow sides is realized in this embodiment by two parallel connected columns rather than a separation wall.

  Depending on the implementation from the second part, the stream withdrawn from or from the air cracking column is preferably led to a crude argon column. The resulting mainly liquid liquid with oxygen is preferably returned to the second part, ie the part from which the argon-containing part is removed.

  The present invention is preferably suitable for a rectification apparatus having a pressure column and a low pressure column, in which a separation wall is arranged in the low pressure column and oxygen is accumulated in the first part from the pressure column, preferably a pool liquid. Is introduced.

  The advantages of the process according to the invention are shown in particular when argon having a purity higher than 95%, preferably higher than 98% and / or argon having an oxygen content of less than 100 ppm, preferably less than 10 ppm, is obtained in a crude argon column. . The invention is particularly advantageous when the crude argon column is loaded with more than 100 theoretical shelves, preferably 150-200 theoretical shelves. In this case, the structural height of the crude argon column is in any case determined by the number of theoretical shelves required for high final purity. The diameter of the crude argon column can be clearly reduced compared to conventional methods without a separation column.

  Advantageously, the air cracking column is charged with packing for rectification. In this case, it is advantageous if the packing is arranged in many overlapping parts, so-called beds, in which the liquid to be rectified and / or the gas to be rectified are collected in two beds, respectively. , Newly dispensed to the next packed bed. When using other fittings or devices instead of packing for rectification in an air cracking column, collection devices and / or distributions at defined intervals in the air cracking column to avoid bad partitioning in the column It is likewise advantageous to provide a device.

  The separation wall between the two separate parts in the air cracking column is preferably adjacent to the upper or lower end of the packed bed, respectively, or by a collector / distributor if other column fittings are used. It ends at the upper or lower end of the corresponding part divided from the part. In any case, since the collector / distributor is arranged at this collision position of the two column portions, it is not necessary to prepare an additional collector / distributor when using the separation wall. Only the collector / distributor placed directly on the separation wall must be modified so that the liquid is dispensed in the desired manner in two parts separated from each other by the separation wall. This corresponds to the case where a second column arranged in parallel to the first air decomposition column is used instead of the separation wall column.

  In that case, the air decomposition column, especially the low-pressure column of the double column apparatus, is divided into four parts or, if packing is used, four packing beds, and a separation wall is prepared at the height of the second and third parts. It has been shown to be particularly advantageous.

  A mass exchange part is used which causes the same pressure drop for the gas to rise advantageously in the first part and the second part.

  The invention and details of the invention are explained in more detail below by means of an embodiment shown in the drawings.

  FIG. 1 shows an apparatus for carrying out the method of the present invention, FIG. 2 shows another embodiment of the present invention, FIG. 3 shows the specific vapor amount to be supplied to a crude argon column depending on the argon concentration, and FIG. Indicates the argon yield depending on the argon concentration in the steam supplied to the crude argon column.

  FIG. 1 shows a rectifying portion of a cryogenic air decomposition apparatus for obtaining argon. Charge air 1 is introduced into pressure column 2 after corresponding cleaning and cooling. The liquid in which oxygen collected at the bottom of the pressure column 2 is accumulated is transferred to the low pressure column 4 through the conduit 3.

  The low pressure column 4 is formed as a separation wall column. A packing is prepared in the low-pressure column 4 as a rectifying part, and the packing is arranged in a plurality of overlapping beds 19, 20, 21, and 22. Each bed has a height of about 6 m. Collecting / dispensing devices 23, 24, 25, 26, 27 are provided for collecting and distributing the liquid flowing down in the low-pressure column 4 between each two beds.

  A separation wall 5 is arranged in the middle part of the low-pressure column 4 and divides the low-pressure column 4 into two parts 6 and 7. In this case, the separating wall 5 extends over the entire length of the two intermediate packing beds 20 and 21. Gas exchange and liquid exchange between the two separated parts 6, 7 are not possible in this part.

  On the other hand, the upper and lower beds 19 and 22 of the separated parts 6 and 7 extend over the entire cross section of the low-pressure column 4, and the gas flow or rising or lowering separately into the two parts 6 and 7 or The liquid flow combines again.

  Reservoir liquid is supplied from the pressure column 2 to the low pressure column 4 via the conduit 3 to the separated portion 6. Turbine air can be further introduced into the low-pressure column 4 via the conduit 12. Gaseous product nitrogen can be obtained by the conduit 8 at the head of the low pressure column 4. Further, an impure nitrogen discharge port 9 is prepared above the divided portions 6 and 7. Gaseous or liquid product oxygen can be withdrawn from the bottom of the low pressure column 4 via conduits 10 and 11.

  The two parts 6 and 7 are fitted with a packing having the same specific surface area. The vapor rising in the low pressure column 4 undergoes the same pressure loss in the two parts 6, 7. The descending liquid is distributed into the two parts 6 and 7 using the distribution devices 24 and 25. The same amount of liquid is preferably provided in the two parts 6,7. It is important to have different liquid feeds in sections 6 and 7 to optimize the performance of the method. The distribution of the rising vapor to the two parts 6, 7 is naturally advantageously adjusted depending on the amount of liquid flowing opposite and the pressure loss in the packing beds 20, 21.

  A stream 13 comprising mainly argon and oxygen is taken from part 7 with an argon concentration of 35% and introduced into a crude argon column 14 equipped with packing. The oxygen-argon mixture is rectified in a crude argon column 14. Argon generated at the head of the crude argon column 14 is condensed by the head condenser 15, a part is obtained as a product 16 with a residual oxygen content of less than 10 ppm, and a part thereof is returned to the crude argon column 14 as a reflux liquid 17. Supply. Liquid oxygen is collected at the bottom of the crude argon column 14 and returned to a separate portion 7 of the low pressure column 4 via conduit 18.

  A separation wall 5 separates the pool liquid feed 3 from the pressure column 2 and the turbine air 12 from the argon exhaust stream 13 in the low pressure column 4. In this way, a significantly higher argon concentration can be adjusted in the argon discharge stream 13 than a column without separation walls.

  FIG. 2 shows an embodiment of the present invention in which a parallel side column 30 is provided instead of the separation wall 5. In the two figures, the same parts are given the same reference numerals.

  In this case, the low-pressure column 4 is formed without a separation wall. A part of the liquid descending from the rectifying part 22 is distributed to the beds 20 and 21 by the distributor 24, and the bed forms the first part. The second part is realized by the side column 30. A part of the liquid descending from the packing bed 22 is removed from the low pressure column 4 by the conduit 31 and supplied to the head of the side column 30. The gas generated at the head of the side column 30 is returned to the low pressure column 4 above the packing bed 21 by a conduit 32. Correspondingly, liquid is introduced from the side column 30 to the low pressure column 4 via the conduit 33 or from the low pressure column 14 to the side column 30 via the conduit 34.

  The processing method in the embodiment according to FIGS. 1 and 2 is the same, slightly in FIG. 2 the rectifying parts 20, 21 of the low pressure column 4 represent the first part 6 and the side column 30 represents the second part 7. . Correspondingly, streams 3 and 12 are introduced into the low pressure column 4 and the argon containing stream 13 is removed from the side column 30.

  Within the framework of the present invention, the specific steam volume to be supplied to the crude argon column 14 by a simulation test, that is, the steam volume related to the argon product volume, is measured depending on the argon concentration of the steam. The measured dependence is shown in FIG. In this case, an argon product purity of 98.5% and a constant argon yield, ie a constant ratio of argon product to argon content in the charge air, are started.

  The straight curve shows the theoretical minimum steam volume with an infinite number of theoretical shelves. The dotted curve shows the course of the state calculated with 50 theoretical shelves. The two curves have substantially the same course. However, it can be seen from the final shelf number curve that in this case a steam volume of about 30-40% greater than the theoretical curve must be used.

  The two curves show that less argon must first be transferred to the crude argon column 14 to obtain the desired purity and amount of argon as the argon concentration increases. The curves each approach the lower limit at an argon concentration of about 50%. When the argon concentration is higher than this, a decrease in the amount of vapor to be supplied cannot be expected, or only a further decrease can be expected.

  The diameter of the crude argon column can be made considerably smaller due to the amount of steam that decreases when the argon concentration in the feed stream to the crude argon column 14 increases. However, a decrease in vapor volume can only be observed up to an argon concentration of about 50%. On the other hand, when the concentration is increased to higher than 50%, further reduction of the vapor amount cannot be achieved under the conditions of the present invention, and further reduction of the crude argon column cross section cannot be achieved. However, the adjustment costs in the low pressure column that accompany the increase in concentration obviously increase.

  The theoretical number of shelves in the crude argon column 14 is not significantly reduced by increasing the argon concentration in the steam 13 to be fed at the desired product purity of 98.5%, but it is the number of shelves at high product purity. Is determined by the final concentration to be achieved and not by the starting concentration.

  The low pressure column 4 is operated in accordance with the invention so that a 45% argon concentration is achieved in the side discharge stream 13. At this concentration, the amount of steam introduced into the crude argon column 14 can be minimized, and the diameter of the crude argon column 14 can be reduced corresponding to the amount of steam.

  FIG. 4 shows the argon yield depending on the argon concentration of the vapor supplied to the argon column. The straight curve indicates the value calculated for the short separation wall, and the dotted curve indicates the value calculated for the long separation wall. At that time, the number of shelves in the low-pressure column is kept constant.

  It can be seen from the linear curve that the argon yield is substantially constant in the range of 10-25% argon concentration in the supplied steam. This curve breaks at 25% because the high argon concentration cannot be achieved with the separation wall length employed. In the case of a long separation wall, which is the basis for the calculation of the dotted curve, a substantially constant argon yield can be seen in the range of high argon concentrations higher than 30% and up to 90%. Therefore, increasing the argon concentration does not adversely affect the yield.

FIG. 2 shows an apparatus for performing the method of the present invention.

It is a figure which shows the other Example of this invention.

It is a figure which shows the specific vapor amount which should be supplied to the crude argon column depending on argon concentration.

It is a figure which shows the argon yield depending on the argon concentration in the vapor | steam supplied to a crude argon column.

Explanation of symbols

  1 Air, 2 Pressure column, 3 Flow, 4 Low pressure column, 5 Separation wall, 6, 7 part, 8 Conduit, 9 Outlet, 10, 11, 12 Conduit, 13 flow, 14 Crude argon column, 15 Condenser, 16 Product, 17 reflux, 18 conduit, 19, 20, 21, 22 rectification part, 23, 24, 25, 26, 27 collector / distributor, 30 side column, 31, 32, 33, 34 conduit

Claims (13)

  A method of obtaining argon by cryogenic decomposition of air in a rectifying apparatus having three rectifying portions arranged in a row, wherein the first and second rectifying portions and the second and third rectifying portions are Each connected to the gas side and the liquid side, the second rectification part has two parts, the two parts are not connected to each other on the gas side and the liquid side, and flow in parallel, In a method for obtaining argon by cryogenic decomposition of air in which a fluid with oxygen and argon is introduced into one part and a stream with oxygen and argon is taken from the second part of the two parts, the second part (7, 30) Argon is obtained by cryogenic decomposition of air, characterized in that the argon concentration in the stream (13) withdrawn from is 15-50%, preferably 15-40%, particularly preferably 20-35% Method.   The rectifying device has at least one air cracking column (4), which has three rectifying parts (19, 20, 21, 22) arranged in a row, wherein the second rectifying part (20, 21) has a separation wall (5) extending in the longitudinal direction of the column, whereby the air cracking column (4) is at the height of the separation wall (5) the first part (6) and the second part ( The method according to claim 1, which is divided into 7).   The rectification apparatus has at least one first air decomposition column (4) and a second column (30), the first air decomposition column (4) on the gas side and the liquid side at the upper end and the lower end. 2), wherein the part (20, 21) and the second column (30) present in the intermediate position of the first air cracking column (4) form two parts. .   4. A process according to claim 3, wherein a stream (13) comprising oxygen and argon is withdrawn from the second column (30).   5. The process as claimed in claim 1, wherein the stream (13) withdrawn from the second part (7, 30) is fed to a crude argon column (14).   6. A method as claimed in claim 5, wherein the pool liquid from the crude argon column (14) is returned to the second part (7, 30).   7. Process according to claim 5 or 6, wherein argon having a purity of greater than 95%, preferably greater than 98%, is obtained in a crude argon column (14).   8. The process as claimed in claim 5, wherein argon having an oxygen content of less than 10 ppm is obtained in the crude argon column (14).   9. The process as claimed in claim 5, wherein the crude argon column (14) has more than 100, preferably 150 to 200 theoretical shelves.   10. The process as claimed in claim 1, wherein at least part of the filling is introduced into the rectification part (19, 20, 21, 22) for rectification.   11. A method according to claim 10, wherein the fluid having oxygen and argon is collected and / or distributed (23, 24, 25, 26, 27), respectively, between two rectifying sections.   10. The fluid according to claim 1, wherein the fluid having oxygen and argon discharged in the gaseous state in the rectification device is subjected to the same pressure loss in the first part and the second part (6, 7). the method of.   The rectification device has a pressure column (2) and a low pressure column (4), in which a separation wall (5) is arranged in the low pressure column (4), with oxygen from the pressure column (2) in the first part (6). 13. The method as claimed in claim 1, wherein the fluid (3) is introduced.

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