Patent Application
20240393042
The invention relates to a method for the cryogenic separation of air and to a corresponding plant in accordance with the preambles of the independent claims.
The production of air products in the liquid or gaseous state by cryogenic fractionation of air in air separation plants is known and described, for example, in H.-W. Häring (Ed.), Industrial Gases Processing, Wiley-VCH, 2006, in particular Section 2.2.5, “Cryogenic Rectification.” Unless expressly defined otherwise, the terms used below have the meanings commonly used in specialist literature.
As is known, so-called main air compressor/booster air compressor (MAC/BAC) methods or so-called high air pressure (HAP) methods can be used for air separation. The methods using a main air compressor and a booster air compressor are the more conventional methods; high air pressure methods are increasingly used as alternatives nowadays. Reference is made to the further explanations below.
As also explained below, despite their advantages, in particular the reduction in the number of rotating machines and thus the lower construction costs, high air pressure methods prove to be disadvantageous for certain product constellations compared to main air compressor/booster air compressor methods.
The object of the invention is therefore to improve the method circuit for high air pressure methods in such a way that the main advantage of the high air pressure method mentioned above is retained, but that there are also advantages over the main air compressor/booster air compressor method when viewed as a whole.
Against this background, the invention proposes a method for the cryogenic separation of air and an air separation plant according to the general concepts of the independent patent claims. Embodiments of the invention are the subject matter of the dependent claims and of the description below.
Some basic principles of the present invention are first explained in more detail and terms used to describe the invention are defined.
Thus, the term “air product” is intended here to refer in particular to a fluid that is provided at least partially by cryogenic separation of atmospheric air. An air product according to the underlying understanding comprises one or more air gases contained in atmospheric air in a different composition than in atmospheric air. An air product can in principle be present or provided in a gaseous, liquid or supercritical state and can be converted from one of these aggregate states to another. In particular, a liquid air product can, by heating at a certain pressure, be converted to a gaseous state (evaporated) or converted to a supercritical state (pseudo-evaporated), depending on whether the pressure is below or above critical pressure during heating. Where “evaporation” is referred to below, it should also include a corresponding pseudo-evaporation.
Air separation plants have rectification column arrangements that can be designed in different ways. In addition to rectification columns for recovering nitrogen and/or oxygen in the liquid and/or gaseous state, i.e., rectification columns for nitrogen-oxygen separation, which can be combined in particular in a known double column, rectification columns for recovering further air components, in particular noble gases, or pure oxygen can be provided.
The rectification columns of typical rectification column arrangements are operated at different pressure levels. Known double-columns have a so-called pressure column (also referred to as a high-pressure column, medium-pressure column or lower column) and a so-called low-pressure column (also referred to as an upper column). The high-pressure column is typically operated at a pressure range of 4 to 7 bar, in particular about 5.3 bar; the low-pressure column on the other hand is operated in a pressure range of typically 1 to 2 bar, in particular about 1.4 bar.
Multi-stage turbocompressors, referred to herein as main air compressors, are used in air separation plants to compress the feed air quantity. In principle, mechanical structure of turbocompressors is known to the skilled person. In a turbocompressor, the medium to be compressed is compressed by means of turbine blades arranged on a turbine wheel or directly on a shaft. A turbocompressor forms a structural unit, but in the case of a multistage turbocompressor it can have a plurality of compressor stages. A compressor stage usually comprises a turbine wheel or a corresponding arrangement of turbine blades. All of such compressor stages can be driven by a common shaft. However, it is also possible to drive the compressor stages in groups with different shafts, wherein the shafts can also be connected to each other via gears.
The main air compressor is further characterized by the fact that the total air quantity fed into the rectification column arrangement and used for the production of air products, i.e., the total feed air quantity, is compressed by said main air compressor. Accordingly, a “booster air compressor” can also be provided, in which, however, only a portion of the feed air quantity compressed in the main air compressor is brought to an even higher pressure. This can also be designed as a turbocompressor. To compress partial quantities of air, additional turbocompressors are typically provided, which are also referred to as boosters, but typically only perform compression on a relatively small scale compared to the main air compressor or the booster air compressor, in particular based on the air quantity compressed. A booster air compressor can also be present in a high air pressure method (see below), but this compresses a partial quantity of the feed air quantity then starting from a higher pressure.
A “cold compressor” or “cold booster” is to be understood here to mean a compressor or booster which is supplied to the fluid at a temperature in a temperature range significantly below the ambient temperature of the air separation plant, in particular at a temperature of less than −50° C., or −100° C., and in particular more than −150° C. or −200° C. A hot compressor or hot booster, on the other hand, is supplied with fluid at a temperature in a temperature range of more than −30° C., 0° C., 20° C. or 50° C. and in particular up to 100° C. or 200° C.
Air can also be expanded at a plurality of locations in air separation plants, for which purpose expansion machines in the form of turboexpanders, also referred to here as expansion turbines or turbines for short, can also be used, among other things. Turboexpanders can also be coupled with and drive turbocompressors. If one or more turbocompressors are driven without externally supplied energy, i.e., only via one or more turboexpanders, the term turbine booster is also used for such an arrangement. In a turbine booster, the turboexpander (the expansion turbine) and the turbocompressor (the booster) are mechanically coupled, wherein the coupling can be at the same speed (for example, via a common shaft) or at different speeds (for example, via an intermediate gearbox). Any reference made here to a turbine unit should in particular be understood to mean an arrangement having at least one expansion turbine.
Main air compressor/booster air compressor methods are characterized by the fact that only a portion of the total feed air quantity supplied to the rectification column arrangement is compressed to a pressure level that is substantially, i.e., by at least 3, 4, 5, 6, 7, 8, 9 or 10 bar, above the pressure level of the pressure column, and is thus above the highest pressure level used in the rectification column arrangement. A further portion of the feed air quantity is compressed only to the pressure level of the pressure column or at most to a pressure level that differs by no more than 1 to 2 bar therefrom, and is fed into the pressure column at such lower pressure level without expansion. An example of a main air compressor/booster air compressor method is disclosed in Häring (see above) in
In a high air pressure method, on the other hand, the total feed air quantity that is supplied to the rectification column arrangement is typically compressed to a pressure level that is substantially, i.e., 3, 4, 5, 6, 7, 8, 9 or 10 bar, or more above the pressure level of the pressure column, and is thus above the highest pressure level used in the rectification column arrangement. The pressure difference can be up to 14, 16, 18, or 20 bar or more, for example. High air pressure methods have been described in detail, for example, from EP 2 980 514 A1 and EP 2 963 367 A1.
High air pressure methods are typically used with so-called internal compression (IC). In internal compression, at least one gaseous, pressurized air product provided by means of the air separation plant is formed by taking a cryogenic liquid air product from the rectification column arrangement, subjecting it to an increase in pressure, and at the product pressure converting it to the gaseous or supercritical state by heating. For example, gaseous pressurized oxygen (GOX IV, GOX IC), gaseous pressurized nitrogen (GAN IV, GAN IC) and/or gaseous pressurized argon (GAR IV, GAR IC) can be produced by means of internal compression. The internal compression offers a range of advantages over an alternative, likewise possible external compression and is explained, for example, in Häring (see above), in section 2.2.5.2, “Internal Compression.”
In typical air separation plants, corresponding expansion turbines are present at various points for the generation of cold and liquefaction of mass flows. These are in particular Claude turbines and Lachmann turbines along with Joule-Thomson turbines if necessary. Regarding the function and purpose of corresponding turbines, reference is made to the technical literature, for example F. G. Kerry, Industrial Gas Handbook: Gas Separation and Purification, CRC Press, 2006, in particular sections 2.4, “Contemporary Liquefaction Cycles,” 2.6, “Theoretical Analysis of the Claude Cycle,” and 3.8.1. “The Lachmann Principle.”
High air pressure methods in which the mentioned Lachmann turbines are used are particularly well known. The air expanded in a Lachmann turbine is fed (injected into) into the low-pressure column, which is why it is also referred to as an upper column expander. The Lachmann turbine can be provided as a further turbine unit in addition to a turbine unit, by means of which gaseous compressed air is expanded into the pressure column, i.e., a Claude turbine.
The term “injected air quantity” refers to the compressed air expanded by a typical Lachmann turbine (upper column expander) and fed (injected into) into the low-pressure column. The air thus expanded into the low-pressure column interferes with the rectification, which is why the air quantity that can be expanded in the upper column expander and thus the cold that can be generated in this way for a corresponding plant are limited. Nitrogen-rich air products removed from the pressure column as pressurized nitrogen and exported from the air separation plant, along with liquid nitrogen exported from the air separation plant and internally compressed nitrogen exported from the air separation plant, also influence rectification accordingly and/or have joint effects.
The quantity of air injected into the low-pressure column by means of a Lachmann turbine plus the nitrogen removed from the pressure column and exported from the air separation plant plus the liquid nitrogen exported from the air separation plant plus the internally compressed nitrogen exported from the air separation plant (if present in each case) can be specified in relation to the total air quantity supplied to the rectification column arrangement. The value obtained in this way is referred to as the “injection equivalent.”
A “throttle flow” or “Joule-Thomson flow” is understood to mean an air quantity which, in the main heat exchanger of an air separation plant, liquefies at least predominantly under pressure and is then fed, in particular via a throttle valve, in particular into the pressure column. Instead of a throttle valve, a Joule-Thomson turbine can also be used.
In the language as used herein, liquid fluids, gaseous fluids, or also fluids present in a supercritical state may be rich or poor in one or more components, wherein “rich” may refer to a content of at least 75%, 90%, 95%, 99%, 99.5%, 99.9%, or 99.99%, and “poor” may refer to a content of at most 25%, 10%, 5%, 1%, 0.1%, or 0.01% on a molar, weight, or volume basis. The term “predominantly” may correspond to the definition of “rich” as was just given, but in particular denotes a content of more than 90%. If, for example, “nitrogen” is mentioned here, it can be a pure gas, but also a gas rich in nitrogen.
High air pressure methods can be used in different embodiments. These are often classified and differentiated according to the liquid capacity of the plant, i.e., according to the quantity of air products provided in liquid form and removed from the plant in liquid form (also referred to here as “liquid products”), or according to the ratio of internally compressed air products to liquid products.
With a small quantity of liquid products or if no liquid products are formed and with certain internal compression, a high air pressure method with a hot booster (which is driven by a turbine) and a cold booster (which is also driven by a turbine) represents a cost-effective alternative to a main air compressor/booster air compressor method. However, the maximum pressure that can be achieved with hot and cold boosters connected in series may not be high enough to optimally balance the hot and cold flows in the main heat exchanger without increasing the pressure on the main air compressor excessively (this leads to an energy disadvantage compared to the main air compressor/booster air compressor method) or jeopardizing the buildability of the turbine booster arrangements.
With a conventional main air compressor/booster air compressor method, the process can be adapted relatively well to different product constellations, since both compressors used (main air compressor and booster air compressor) are “responsible” for functionally separate tasks. In principle, the main air compressor only supplies the feed air for separating and the booster air compressor supplies the energy for internal compression and liquid production. Excellent energy efficiency can be achieved by a clever circuit of turbines and booster air compressors (with/without intermediate removal) along with the use of additional throttle flows. However, this generally requires a high number of compressor stages, which increases investment costs. The present invention provides a remedy here.
In a high air pressure method, the mentioned tasks are performed by just one compressor (supply of separation air and energy for internal compression and liquid production). Thus, the total feed air must be compressed to a high pressure in order to achieve a good balance between cold and hot flows in the main heat exchanger. The high pressure must be provided by the turbine boosters and main air compressors. In some cases, especially in product constellations with little or no liquid production, efficient balancing is difficult to achieve without jeopardizing the buildability of the booster turbines or raising the pressure on the main air compressor very high.
High air pressure methods are known with which a throttle flow is generated with the aid of a cold booster and the pressure at the main air compressor can be reduced. However, the energy efficiency is still not equivalent to that of the main air compressor/booster air compressor method. Here, the cold booster is connected downstream of the hot booster. Since the hot booster usually has to compress a large quantity or the quantity ratios between the turbines and boosters have to be adjusted so that the machines can be built, the stage pressure ratio is usually less than 1.4. With cold boosters, a stage pressure ratio of up to 2 or slightly higher can be achieved. The specific speed for the turbine and booster must be within the buildable range and the speed of the machine must not be too high. A corresponding process with two cold compressors connected in series is also known from US 2013/0255313 A1.
The invention is particularly advantageous in the case of low liquid production (with less than 10% liquid removal from the plant, based on internal compression products), and in methods in which the use of a cold compressor is sensible and the injection equivalent is very low, but the nitrogen yield in relation to the oxygen product is very high.
The solution according to the invention takes advantage of the fact that the injection equivalent in the sense explained above is not fully utilized in many plants and operating cases. It is known that an increase in the injection equivalent can improve energy consumption (use of a Lachmann turbine in high air pressure and main air compressor/booster air methods). By increasing the injection equivalent, the air quantity required to supply the required products is increased exponentially, but the pressure required at the main air compressor is reduced, thus reducing the total energy consumption. Furthermore, an increase in the injection equivalent reduces the argon yield. To optimize this, there is an optimum up to which the injection equivalent should (only) be exploited.
In plants with high nitrogen production, the optimum injection equivalent is lower, since increasing the injection equivalent reduces the nitrogen yield.
The idea behind the invention is to utilize the injection equivalent by removing additional pressurized nitrogen from the pressure column at its operating pressure. This pressurized nitrogen is supplied to the turbine, which drives a cold booster (after it has been heated in the main heat exchanger) and expanded to the pressure below the low-pressure column (or to the pressure of the pure nitrogen removed at the top of the low-pressure column). The nitrogen flow expanded in this way is now heated in the main heat exchanger and supplied to the pure nitrogen from the top of the low-pressure column, in particular before it is compressed in an external nitrogen compressor.
The cold booster in turn is supplied with a partial flow of air that has been compressed and then cooled in a hot booster. A partial flow of the air compressed in the main air compressor is supplied to the hot booster. The partial flow compressed in the cold booster is used as high-pressure throttle flow or high-pressure Joule-Thomson flow. This means that a portion of the air from the main air compressor is recompressed twice in order to provide the high-pressure Joule-Thomson flow. In this way, the injection equivalent is optimally adjusted for the plant so that the required nitrogen production can be provided.
From a total cost of ownership (TCO) perspective, the present invention leads to an improvement in the efficiency of high air pressure circuits without any loss of cost advantages or a high degree of complexity in the method. Above all, a reduction in costs can be achieved:
In a conservative calculation of the proposed method compared to the conventional high air pressure cold booster method, energy consumption is the same. Depending on the argon and energy rating and the air products required, the proposed method is very to moderately advantageous. It is very advantageous for plants without argon production.
The method according to the invention for the cryogenic separation of air is carried out using an air separation plant that has a rectification column arrangement with a pressure column and a low-pressure column, wherein the pressure column is operated in a first pressure range and the low-pressure column is operated in a second pressure range, which is below the first pressure range, and at least 90% of a total air quantity separated in the rectification column arrangement is compressed to a pressure in a third pressure range, which is more than 5 bar above the first pressure range. A high air pressure method is therefore carried out, as explained in detail above.
A partial quantity of the total separated air quantity is successively supplied to a first booster driven by a first turbine at a temperature in a first temperature range of −30 to 100° C., compressed using the first booster from the pressure in the third pressure range to a pressure in one fourth pressure range, which is above the third pressure range, cooled to a temperature in a second temperature range of −160 to −60° C., supplied at the temperature in the second temperature range to a second booster driven by a second turbine, compressed using the second boosters from the pressure in the fourth pressure range to a pressure in a fifth pressure range, which is above the fourth pressure range, cooled to a temperature in a third temperature range of −200 to −150° C., in particular at least partially liquefied, and fed into the pressure column. In particular, this is a high-pressure Joule-Thomson flow that can be used in addition to a further Joule-Thomson flow provided at the pressure in the third pressure range. All of the cooling steps described here and below can be carried out using the main heat exchanger, provided that cooling does not already result through expansion.
Within the framework of the present invention, gaseous nitrogen is removed from the pressure column at a pressure in the first pressure range and successively heated to a temperature in a fourth temperature range of in particular −100° C. to 50° C., expanded in the second turbine while cooling to a temperature in a fifth temperature range of in particular −150° C. to −40° C. to a pressure in the second pressure range, and heated to a temperature in a sixth temperature range of 0° C. to 50° C. Furthermore, gaseous nitrogen is also removed from the low-pressure column and heated to the temperature in the sixth temperature range.
According to the invention, and for example in contrast to the prior art such as in particular U.S. Pat. No. 9,945,606 B2, the gaseous nitrogen removed from the low-pressure column is heated separately from the gaseous nitrogen removed from the pressure column, i.e., in particular in separate heat exchanger passages of the main heat exchanger, to the temperature in the sixth temperature range, and the fourth temperature range is from −100 to 50° C. and the fifth temperature range is from −140° C. to −40° C.
Within the framework of the present invention, in other words, nitrogen for the nitrogen turbine used (i.e., the second turbine) is heated to the comparatively high temperature of the fourth temperature range, then expanded so that the temperature is set in the fifth temperature range, and then heated in particular in a separate passage in the main heat exchanger and only mixed with the low-pressure nitrogen from the low-pressure column downstream of such heating. The advantage here is that the high inlet temperature of the turbine leads to a lower consumption of nitrogen to provide the necessary power for the cold booster and thus to better energy efficiency than if such expansion takes place at a lower temperature and with a prior mixing with the low-pressure nitrogen.
The higher turbine inlet temperature or the reduction in quantity makes the necessary turbine smaller and also easier to build by improving the specific speed. The higher turbine inlet temperature also reduces the quantity of pressurized nitrogen required, which results in a lower injection equivalent and therefore a lower air factor than with a Lachmann turbine or a pressurized nitrogen turbine with a lower inlet temperature. This leads to a reduction in the required air quantity and higher air pressure, which results in energy and cost savings for pre-cooling along with the molecular sieve adsorber or the regeneration capacity.
The main heat exchanger volume is reduced by the proposed process, since the passage for low pressure nitrogen is from about 200 K to 300 K and not from 96 to 300 K. In contrast to a method with a Lachmann or cold pressurized nitrogen turbine, the main heat exchanger can be significantly smaller for the same output, since less air has to be used for the process. An additional Joule-Thomson flow on the pressure of the main air compressor, as provided according to one embodiment of the invention, leads to an improvement in the balancing of the heat exchanger temperature profile and thus to better energy efficiency. A smaller air quantity must be compressed in the hot booster, so that it can be operated with a higher pressure difference. The additional throttle flows have a very great advantage in terms of energy, especially with processes with two or more different internal compression pressures of, for example, 30 bar (abs.) for gaseous oxygen and 15 bar (abs.) for gaseous oxygen or nitrogen.
Within the framework of the present invention, the first pressure range is in particular 4 to 7 bar, the second pressure range is in particular 1 to 2 bar, the third pressure range is in particular 10 to 18 bar, the fourth pressure range is in particular in a pressure range of 1.2 times to 1.5 times the third pressure range and the fifth pressure range is in particular in a pressure range of 1.6 times to 2.5 times the fourth pressure range.
Advantageously, a further partial quantity of the total separated air quantity is successively supplied to the first booster at the temperature in the first temperature range, compressed using the first booster from the pressure in the third pressure range to the pressure in the fourth pressure range, cooled to the temperature in the second temperature range or a further temperature range, expanded in the first turbine to a pressure in the first pressure range and fed into the pressure column. In other words, a turbine flow is advantageously formed, which is first subjected to joint compression with the high-pressure throttle flow in the hot booster. The subsequent cooling can take place at the same or a different temperature level than the cooling of the high-pressure throttle flow.
As mentioned, in a particularly preferred embodiment, a method according to the present invention can also comprise that a further partial quantity of the total separated air quantity at the pressure in the third pressure range is cooled to the temperature in the third temperature range and fed (as a further throttle flow) into the pressure column. Advantages have already been explained.
The gaseous nitrogen removed from the low-pressure column and the gaseous nitrogen removed from the pressure column can be combined after separate heating to the temperature in the sixth temperature range. The advantages of this combination downstream of the heating have also been explained above.
In the method, one or more liquids are advantageously removed from the rectification column arrangement, subjected to one or each internal compression, and discharged from the air separation plant in the form of one or more gaseous internal compression products.
The one or more gaseous internal compression products advantageously comprise a gaseous internal compression product produced using oxygen-rich liquid from the low-pressure column.
Advantageously, no liquid products are removed from the air separation plant or one or more liquid products are removed from the air separation plant in a total amount that does not exceed 10% of a total amount of the one or more gaseous internal compression products. As mentioned, the present invention is particularly suitable for such cases of low liquid production.
In one embodiment of the present invention, an argon-rich liquid can be removed from the low-pressure column and supplied to an argon recovery system for the recovery of argon. However, an embodiment without argon recovery can also be provided in one embodiment of the invention.
The air separation plant according to the invention for the cryogenic separation of air has a rectification column arrangement with a pressure column and a low-pressure column, wherein the air separation plant is designed to operate the pressure column in a first pressure range and the low-pressure column in a second pressure range, which is below the first pressure range, and to compress at least 90% of a total air quantity separated in the rectification column arrangement to a pressure in a third pressure range, which is more than 5 bar above the first pressure range.
The air separation plant is further designed to supply a partial quantity of the total air quantity separated one after the other at a temperature in a first temperature range of −30 to 100° C. to a first booster driven by a first turbine, using the first booster to compress it from the pressure in the third pressure range to a pressure in a fourth pressure range, which is above the third pressure range, to cool it to a temperature in a second temperature range of −160 to −60° C., to supply it at the temperature in the second temperature range of a second booster driven by a second turbine, using the second booster to compress it from the pressure in the fourth pressure range to a pressure in a fifth pressure range, which is above the fourth pressure range, to cool it to a temperature in a third temperature range of −200 to −150° C., and to feed it into the pressure column.
Furthermore, the air separation plant according to the invention is designed to remove gaseous nitrogen from the pressure column at a pressure in the first pressure range and to heat it successively to a temperature in a fourth temperature range, to expand it in the second turbine while cooling it to a temperature in a fifth temperature range to a pressure in the second pressure range, and to heat it to a temperature in a sixth temperature range of 0 to 50° C., and to remove gaseous nitrogen from the low-pressure column and to heat it to the temperature in the sixth temperature range.
According to the invention, the air separation plant is designed to heat the gaseous nitrogen removed from the low-pressure column separately from the gaseous nitrogen removed the pressure column to the temperature in the sixth temperature range, wherein the fourth temperature range is from −100 to 50° C. and the fifth temperature range is from −150 to −40° C.
The air separation plant proposed according to the invention is in particular designed to carry out a method as previously explained in embodiments. Reference is therefore expressly made to the above explanations with respect to the methods according to the invention and their advantageous embodiments.
The invention will be described in more detail below with reference to the accompanying drawings, which illustrate preferred embodiments of the present invention.
In the figure, elements that correspond to one another structurally or functionally are denoted by identical reference signs and, for the sake of clarity, are not repeatedly explained. Explanations relating to plants and plant components apply in the same way for corresponding methods and method steps.
In
In the air separation plant 100, air is drawn in by means of a main air compressor 2 via a filter 1 and compressed to a suitable pressure level. After pre-cooling in a pre-cooling device 3, the compressed air flow A formed in this way is freed of residual water and carbon dioxide in a pre-cleaning unit 4, which can be designed in a manner known per se. For the design of the mentioned components, reference is made to the technical literature cited at the outset.
In the example illustrated here, the compressed air flow further designated as A is now divided into two partial flows B and C, of which the partial flow B is guided as a Joule-Thomson flow from the hot to the cold end through a main heat exchanger 4 and fed into the pressure column 11 of a rectification column arrangement 10. The partial flow C is first boosted in a hot booster 6 (previously described as the “first” booster), to which it is supplied at a temperature in a corresponding temperature range (previously the “first” temperature range), and then cooled in the main heat exchanger 4. In the embodiment shown in
The partial flow D is now further increased in pressure in a cold booster (previously the “second” booster), then cooled in the main heat exchanger 4 to a temperature in a cold-side temperature range (previously the “third” temperature range) and fed into the pressure column 11 as a high-pressure Joule-Thomson flow. The partial flow E is expanded in the turbine coupled to the first booster 6 (previously the “first” turbine) and also fed into the pressure column 11. A partial flow F of the partial flow C is also fed into the pressure column 11 (as a further Joule-Thomson flow).
Nitrogen is withdrawn from the pressure column 11 in the form of a material flow G, heated in the main heat exchanger 4 to a temperature in a suitable or advantageous temperature range (previously the “fourth” temperature range), expanded in the turbine coupled to the second booster 8 (previously the “second” turbine) while cooling to a temperature in a corresponding temperature range (previously the “fifth” temperature range), and then heating it again in the main heat exchanger 4 to a temperature in a temperature range on the hot side of the main heat exchanger 4 (previously the “sixth” temperature range).
Gaseous nitrogen in the form of a material flow H is removed from the low-pressure column 12 and heated to the temperature in the sixth temperature range. After heating, it is combined with the material flow H to form a corresponding collective flow I.
In the rectification column arrangement 10, the pressure column 11 is connected to the low-pressure column 12 via a main condenser 13 for heat exchange. A subcooling counterflow device 14 is assigned to the rectification column system 10. An internal compression pump is designated by 15. The air separation plant 100 can have an argon recovery unit of a known type (not shown here).
As explained, the pressure column 11 is fed with cooled, pressurized and, if necessary, liquefied air from material flows B, D, E and F. Immediately downstream of the feed-in point of the material flow F, liquid in the form of a material flow K is withdrawn from the pressure column 11, guided through the subcooling counterflow device 14 and fed into the low-pressure column 12. The low-pressure column 12 is also fed with oxygen-enriched liquid in the form of a sump liquid flow L from the pressure column 11, which is likewise previously guided through the subcooling counterflow device 14. Further top gas from the pressure column 11 is guided through the main condenser 13. The main condenser 13 is operated in a known manner, wherein in particular a material flow M is also transferred to the low-pressure column 12. Impure nitrogen can be withdrawn from the low-pressure column 12 in the form of a material flow h, pure low-pressure nitrogen in the form of a material flow g.
Oxygen-rich sump liquid in the form of a material flow N is withdrawn from the low-pressure column 12 and pressurized in liquid form in the internal compression pump 15. A partial flow O can be provided as a gaseous internal compression product after evaporation in the main heat exchanger. A further partial flow P can be subcooled in the subcooling counterflow device 14 and discharged from the air separation plant 100 in liquid form.
Liquid can also be collected at the top of the low-pressure column 12 and discharged in the form of a material flow Q as a liquid nitrogen product. An impure nitrogen flow R can be withdrawn from the low-pressure column 12 and used in a known manner.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21020490.5 | Sep 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/025406 | 9/1/2022 | WO |
