Method for providing pressurized, oxygen-enriched air products and air separation equipment

Abstract

This invention provides a high-pressure method for manufacturing pressurized oxygen-enriched air products. A first portion of the feed air is supplied to a first turbine unit (5) at a temperature within a first temperature range, where it expands and is fed into a high-pressure tower (11). A second portion of the feed air is supplied to a second turbine unit (6) at a temperature within a second temperature range, where it expands and is fed into a low-pressure tower (12). The pressurized oxygen-enriched air product is provided as an internally compressed product at 16 to 50 bar, wherein evaporation begins at a temperature within a third temperature range. The third temperature range is higher than both the first and second temperature ranges, and the second temperature range is selected such that a two-phase mixture with a liquid content of 5% to 15% is formed at the outlet of the second turbine unit (6), the temperatures within the first and second temperature ranges differ from each other by no more than 10 K, and less than 5% of all air products extracted from the air separation unit (100) are extracted in a liquid, unevaporated form from the air separation unit. The first turbine unit is braked by a cold compressor (4), and the second turbine unit is braked by a generator (G) or a hot-pressurized compressor. Air separation equipment (100) is also the subject of this invention.

Description

[Technical Field]

[0001] This invention relates to a method and a corresponding apparatus for providing pressurized oxygen-enriched air products as described in the preamble of the independent claim. [Previous Technology]

[0002] The production of liquid or gaseous air products by separating air at low temperature in an air separation device is a prior art and is described, for example, in H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH, 2006, and in particular section 2.2.5 "Cryogenic Rectification".

[0003] The term "air product" herein refers at least in part to a fluid provided by cryogenic separation of atmospheric air. Air products as understood herein comprise one or more air gases contained in atmospheric air, whose composition differs from atmospheric air. In principle, air products can exist or be provided in a gaseous, liquid, or supercritical state, and can be converted from one of these aggregated states to another. Specifically, liquid air products can be converted into a gaseous state ("evaporation") or a supercritical state ("pseudo-evaporation") by heating at a certain pressure, depending on whether the heating pressure is below or above the critical pressure. Where "evaporation" is used below, it should also include the corresponding pseudo-evaporation.

[0004] The air separation equipment has a distillation column system, which is traditionally configured as a two-column system, particularly the classic Linde two-column system, but can also be configured as a three-column or multi-column system. In addition to distillation columns for obtaining liquid and / or gaseous nitrogen and / or oxygen gases (i.e., nitrogen-oxygen separation distillation columns), distillation columns for obtaining other air components (especially rare gases such as krypton, xenon, and / or argon) may also be provided. The terms "distillation" and "distillation distillation," as well as "column" and "column," or related compound terms, are often used as synonyms, and this is also the case in this case.

[0005] The distillation column systems described above operate at different pressures. Known two-column systems have a so-called high-pressure column (also called a pressure column, intermediate-pressure column, or lower column) and a so-called low-pressure column (also called an upper column). The high-pressure column typically operates at 4 to 7 bar, particularly about 5.3 bar. The low-pressure column generally operates at 1 to 2 bar, particularly about 1.4 bar. In certain cases, even higher pressures may be used in both distillation columns. The pressures given herein are absolute pressures at the top of the column.

[0006] Air separation can be achieved using either a so-called Main Air Compressor / Booster Air Compressor (MAC-BAC) process or a so-called High Air Pressure (HAP) process. The MAC-BAC process is more traditional, while the HAP process has been increasingly used to replace it in recent years. This invention is used in conjunction with the HAP process; therefore, the following descriptions are generally applicable to this invention. Due to the significantly reduced cost—the MAC-BAC and HAP-BAC are integrated to some extent into a single machine—and the comparable efficiency, the HAP process can be a favorable alternative to the MAC-BAC process.

[0007] The main compressor / booster compressor process is characterized in that only a portion of the feed air supplied to the entire distillation column system is compressed to a pressure significantly higher than the operating pressure of the high-pressure column, i.e., at least 3, 4, 5, 6, 7, 8, 9, or 10 bar higher. Another portion of the feed air is compressed only to this pressure or at a pressure no more than 1 to 2 bar lower, and is fed into the high-pressure column at this lower pressure, particularly without further expansion. For example, Häring (see above) discloses a main compressor / booster compressor process in Figure 2.3A.

[0008] The high-pressure process compresses the entire feed air supplied to the distillation column system to a pressure significantly higher than the operating pressure of the high-pressure column, that is, at least 3, 4, 5, 6, 7, 8, 9, or 10 bar higher, for example, 14, 16, 18, or 20 bar higher. High-pressure processes are disclosed, for example, by EP 2 980 514 A1 and EP 2 963 367 A1.

[0009] High-pressure processes are often used in conjunction with so-called internal compression (IV, IC). Internal compression involves creating at least one gaseous pressurized air product supplied by an air separation unit by extracting a cold liquid air product from a distillation column system, increasing its pressure to the product pressure, and then heating it at that pressure to convert it into a gaseous or supercritical state. For example, internal compression can produce gaseous pressurized oxygen (GOX IV, GOX IC), gaseous pressurized nitrogen (GAN IV, GAN IC), and / or gaseous pressurized argon (GAR IV, GAR IC). Internal compression offers a number of advantages over external compression, which can also be used as an alternative, as described, for example, in Section 2.2.5.2, "Internal Compression," by Häring (see above).

[0010] High-pressure processes can be used in various designs. These designs are typically classified and differentiated based on the equipment's liquid capacity (i.e., the amount of air product supplied in liquid form and extracted from the equipment in liquid form) or the ratio of internal compressed air product to liquid product. If the liquid capacity is not too high, high-pressure processes will employ, for example, refrigerated boosters or refrigerated compressors of the following types, because this allows excess cooling capacity to be converted into higher air pressure, thereby improving process efficiency.

[0011] High-pressure processes employing the so-called Lachmann turbine or jet turbine (also known as Upper Column Expander) of the following type are also known technologies. Air expanded in the Lachmann turbine is fed into a low-pressure tower. The Lachmann turbine can be supplied as an additional turbine unit besides the turbine unit (through which gaseous compressed air is expanded into a high-pressure tower, i.e., a so-called Claude turbine).

[0012] In particular, when it is necessary to provide primarily or solely internally compressed gaseous oxygen at pressures ranging from 16 to 50 bar (absolute pressure) using a high-pressure process, it is necessary to improve process control. The object of this invention is to improve the efficiency and competitiveness of high-pressure processes, particularly for such typical gas equipment. [Summary of the Invention]

[0013] Against this background, the present invention proposes a method for providing one or more oxygen-enriched air products and a corresponding apparatus, characterized by the relevant independent items. The technical solution of the present invention is the subject of the appendix and the following description.

[0014] First, other principles of the present invention will be explained in detail and the terms used to describe the present invention will be defined.

[0015] "Feed air volume" (or simply "feed air") refers herein to all the air supplied to the distillation column system of the air separation equipment. As previously stated, this feed air volume is only partially compressed to a pressure range significantly higher than the operating pressure range of the high-pressure column in the main compressor / booster compressor process. In the high-pressure process, which is the subject of this invention, all of the feed air volume is compressed to such a high pressure range. For the meaning of the word "significantly" in relation to the main compressor / booster compressor process and the high-pressure process, please refer to the above description.

[0016] "Cold liquid" here refers to a liquid medium with a boiling point significantly lower than the ambient temperature, such as -50°C or lower, and especially -100°C or lower. Examples of cold liquids include liquid air, liquid oxygen, liquid nitrogen, liquid argon, or liquids rich in the above compounds.

[0017] For information on the apparatus or equipment used in air separation equipment, please refer to technical documents such as Häring (see above), particularly Section 2.2.5.6, "Apparatus". In the following text, certain aspects of the apparatus will be described in detail for the purpose of clarification and clearer definition.

[0018] The air separation equipment uses a multi-stage turbo compressor, referred to herein as a "main air compressor," to compress the feed air volume. The mechanical structure of a turbo compressor is generally known to those skilled in the art. In a turbo compressor, the medium to be compressed is compressed by turbine blades arranged on a turbine impeller or directly on a shaft. The turbo compressor forms a structural unit, but in the case of a multi-stage turbo compressor, this structural unit may have several compressor stages. A compressor stage typically includes one turbine impeller or corresponding turbine blade configuration. All such compressor stages can be driven by a common shaft. However, it is also possible to group and drive these compressor stages with different shafts, wherein these shafts can also be connected to each other via a transmission device.

[0019] The main air compressor further has the following characteristics: all the air volume (i.e., all the feed air volume) fed into the distillation column system for producing air products is compressed by the main air compressor. Correspondingly, a "booster compressor" may also be provided, but the booster compressor only brings a portion of the feed air volume already compressed in the main air compressor to a higher pressure. The booster compressor may also be designed as a turbo compressor. To compress a portion of the air volume, other turbo compressors, also known as boosters, are generally provided, but compared to the main air compressor or booster compressor, these other turbo compressors typically provide only a lower degree of compression, especially relative to the compressed air volume. A booster compressor may also be present in high-pressure processes; however, this booster compressor will compress a portion of the feed air volume starting at a higher pressure.

[0020] "Cold compressor" or "cold booster" means herein a compressor or booster that supplies fluid at a temperature significantly lower than the ambient temperature of the air separation equipment, particularly below 0°C, -50°C or -100°C and especially above -150°C or -200°C.

[0021] Furthermore, air can expand at several locations within the air separation device; for this purpose, an expander in the form of a turbo expander, also referred to herein as an "expansion turbine," can be used. The turbo expander can also be coupled to and drive a turbo compressor. If one or more turbo compressors are driven without external power supply, i.e., driven only by one or more turbo expanders, this configuration is also suitable for the use of the term "turbocharger." In a turbocharger, the turbo expander (expansion turbine) is mechanically coupled to the turbo compressor (charger), wherein this coupling can be at the same speed (e.g., through a common shaft) or at different speeds (e.g., through an intermediate drive). When referred to herein as a "turbo unit," it specifically refers to a configuration having at least one expansion turbine.

[0022] In typical air separation equipment, corresponding expansion turbines are present at different locations for cooling and liquefying the material flow. These expansion turbines are in particular the aforementioned Claude turbines and Lachmann turbines, and where appropriate, the so-called Joule-Thomson turbines. For the function and application of the respective turbines, please refer to technical literature such as FG Kerry, Industrial Gas Handbook: Gas Separation and Purification, CRC Press, 2006, especially Section 2.4, "Contemporary Liquefaction Cycles", Section 2.6, "Theoretical Analysis of the Claude Cycle", and Section 3.8.1, "The Lachmann Principle".

[0023] "Drosselstrom" or "Joule-Thomson flow" refers to the amount of air that is pressurized and liquefied in the main heat exchanger of an air separation unit, and then, in particular, sent to the high-pressure tower through a throttle valve. A Joule-Thomson turbine may also be used instead of a throttle valve.

[0024] In the usage of this document, a liquid, gaseous, or supercritical fluid may be rich in or poor in one or more components, where "rich" can mean at least 75%, 90%, 95%, 99%, 99.5%, 99.9%, or 99.99% molar, weight, or volume content, and "poor" can mean a maximum of 25%, 10%, 5%, 1%, 0.1%, or 0.01% molar, weight, or volume content. The term "major" can be equivalent to the definition of "rich," but specifically refers to a content greater than 90%. For example, if "nitrogen" or "oxygen" is mentioned herein, it can refer to a pure gas, but it can also refer to a nitrogen-rich or oxygen-rich gas.

[0025] Pressure and temperature will be characterized hereinafter by pressure and temperature within certain pressure and temperature ranges. This is to show that precise pressure and temperature values ​​are not required to describe pressure and temperature when implementing the concept of the present invention. However, such pressure and temperature typically fluctuate within a corresponding range of ±1%, 5%, or 10% of the average value. Different pressure and temperature ranges may constitute non-overlapping or overlapping ranges. For example, the provided pressure ranges particularly include unavoidable or foreseeable pressure losses, such as those caused by pipeline resistance or similar reasons. The same applies to pressure ranges. Pressure or pressure range limits provided herein in bar refer to absolute pressure unless otherwise specified. Advantages of the Invention

[0026] As mentioned above, conventional high-pressure processes are typically classified and differentiated based on so-called liquid capacity or the ratio of internally compressed product to liquid product. Liquid capacity refers to the amount of air product output from the equipment or corresponding process in a liquid state (i.e., air product that does not undergo evaporation or pseudo-evaporation). That is, such product cannot be used to cool the feed stream of the equipment or process through corresponding evaporation. Therefore, if a small amount of air product is output from the equipment or corresponding process in a liquid state but evaporation or pseudo-evaporation occurs, there is a certain degree of excess cooling.

[0027] Therefore, when the liquid volume is low, a so-called cold booster can be used, for example, to improve process efficiency by converting this excess cold into higher air pressure. The heat input through the cold booster partially "eliminates" the excess cold, but in turn, the cold booster compresses a portion of the feed air, thereby reducing, for example, the power of the main air compressor. As mentioned above, the intake air temperature of the cold booster is lower than the ambient temperature, therefore, assuming ideal gas behavior for simplicity, power consumption will be reduced.

[0028] The present invention applies to a high-pressure process for producing gaseous oxygen without producing (considerable) liquid as described above, wherein in addition to a first turbine unit that expands air into a high-pressure tower in the manner of a Claude turbine, a jet turbine (Lachmann turbine) is also provided as a second turbine unit.

[0029] Specifically, the solution of the present invention to achieve the above-mentioned objective is to supply air to the Lachmann turbine at an inlet temperature significantly lower than that of conventional processes. This causes intense pre-liquefaction at the turbine outlet of the Lachmann turbine. Consequently, the amount of air to be liquefied as one or more controlled flows in the main heat exchanger is significantly reduced, resulting in a significant increase in efficiency. In the lower region of the main heat exchanger, i.e., where the airflow condenses, less heat needs to be transferred, and the power of the refrigeration compressor is reduced.

[0030] In this context, the present invention generally proposes a method for producing pressurized oxygen-enriched air products using an air separation device, the air separation device having a distillation column system as well as a main heat exchanger, a first turbine unit and a second turbine unit, the distillation column system including a high-pressure column and a low-pressure column.

[0031] The high-pressure column operates in a first pressure range of 4 to 7 bar, particularly about 5.3 bar, and the low-pressure column operates in a second pressure range of 1 to 2 bar, particularly about 1.4 bar. At least a dominant portion of the feed air supplied to the entire distillation column system, particularly the total feed air typically supplied in high-pressure processes, is compressed to a pressure within a third pressure range, which is at least 3 bar higher than the first pressure range. For other possible pressure differentials, please refer again to the above description of high-pressure processes.

[0032] A first portion of the feed air, compressed to a pressure within a third pressure range, is supplied to the first turbine unit at a pressure within the third pressure range or at a pressure within a fourth pressure range higher than the third pressure range, and at a temperature within a first temperature range. The first turbine unit expands the feed air to a pressure within the first pressure range and sends it into the high-pressure tower. As described below, to provide the first portion at a temperature within the first temperature range, the main heat exchanger of the air separation device is used, in particular, in the manner described below, and, if necessary, a corresponding pressurization unit is used, in the manner described below, to obtain a pressure within the fourth pressure range. Within the scope of this invention, the first turbine unit is, in particular, a typical Claude turbine as described above, or the first turbine unit comprises a typical Claude turbine as described above.

[0033] A second portion of the feed air, compressed to a pressure within the third pressure range, is supplied to the second turbine unit at a pressure within the third pressure range or at a pressure within a fifth pressure range higher than the third pressure range, and at a temperature within the second temperature range. The second turbine unit expands the feed air to a pressure within the second pressure range and feeds it into a low-pressure tower. As described below, to provide the second portion at a temperature within the second temperature range, the main heat exchanger of the air separation device is used, in particular, in the manner described below, and, if necessary, a corresponding pressurization unit is used, in the manner described below, to obtain a pressure within the fifth pressure range. Within the scope of this invention, the second turbine unit is, in particular, a typical Lachmann turbine as described above, or the second turbine unit comprises a typical Lachmann turbine as described above.

[0034] The present invention includes: to provide a gaseous pressurized oxygen-enriched air product, extracting an oxygen-enriched liquid from a distillation column system, the oxygen-enriched liquid being heated in a liquid state to a temperature within a third temperature range while simultaneously reaching a pressure of 16 to 50 bar or 25 to 50 bar, particularly 40 to 50 bar, for example, about 43 bar, within a sixth pressure range, and then fed into a main heat exchanger, where it evaporates at a temperature within the third temperature range and is discharged from an air separation device. That is, the pressurized oxygen-enriched air product is provided as an internally compressed product.

[0035] According to the present invention, the third temperature range is the temperature range at which the oxygen-rich liquid evaporates in the main heat exchanger after being pressurized into a liquid state, which is higher than both the first temperature range and the second temperature range.

[0036] Within the scope of the invention, the second temperature range is selected such that a two-phase mixture with a liquid content of 5% to 15%, particularly 8% to 13%, is formed at the outlet of the second turbine unit, wherein such percentages are specifically used to represent the mass fraction of the liquid component relative to the total mass of the two-phase mixture.

[0037] Furthermore, within the scope of the present invention, the temperature in the first temperature range and the temperature in the second temperature range differ from each other by no more than 10 K.

[0038] According to the present invention, the air separation device operates in such a manner that less than 5%, particularly less than 2%, of all air products extracted from the air separation device are extracted in a liquid, unevaporated form. The term "air products" includes not only substantially pure products such as oxygen or nitrogen, but also impure streams (so-called waste gases), as explained above. With regard to substantially pure products, this proportion is less than 10%, particularly less than 5% or less than 2%. "Substantially pure" products particularly include nitrogen, oxygen, and argon, or fluids rich in these components.

[0039] By combining the measures proposed in this invention with each other, the advantages mentioned above can be achieved in particular. Please refer to the foregoing description.

[0040] Specifically, the first and second temperature ranges are 110 K to 140 K, and particularly 120 K to 135 K.

[0041] The third temperature range is at least 10 K higher than the first and second temperature ranges, and at most 40 K higher.

[0042] In the method according to the invention, a first portion of the amount of feed air compressed to a pressure within a third pressure range is advantageously provided at a pressure within a fourth pressure range, and at the same time, a pressure within the fourth pressure range is achieved using a pressurization unit.

[0043] The booster unit used at this time can be used to drive the first turbine unit.

[0044] In one embodiment of the present invention, a first portion of the feed air volume compressed to a pressure within a third pressure range may be cooled in a first cooling step in a main heat exchanger before reaching a pressure within a fourth pressure range using a pressurization unit, and after the first portion of the feed air volume compressed to a pressure within a third pressure range reaches a pressure within a fourth pressure range using a pressurization unit, it may be cooled in a second cooling step in a main heat exchanger, wherein the second cooling step includes cooling to the aforementioned temperature within a first temperature range.

[0045] The third portion of the feed air volume compressed to a pressure within the third pressure range, in particular, can undergo a first cooling step together with the first portion of the feed air volume compressed to a pressure within the third pressure range, and reach a pressure within the fourth pressure range using a pressurization unit. The third portion of the feed air volume compressed to a pressure within the third pressure range and then further compressed to a pressure within the fourth pressure range is liquefied in the main heat exchanger at the pressure within the fourth pressure range, then expands and is sent to the high-pressure tower. The first portion is extracted from the main heat exchanger, particularly at an extraction point corresponding to a temperature within the first temperature range, while the third portion passes through the main heat exchanger until it reaches the cold end. The third portion thus forms a controlled flow.

[0046] In the method according to the invention, a second portion of the feed air volume compressed to a pressure within a third pressure range can be provided, in particular, at a pressure within a fifth pressure range, while simultaneously reaching a pressure within a fourth pressure range using other booster units. In this case, the other booster units can in particular drive a second turbine unit, i.e., implemented as "self-boosting".

[0047] If it is not necessary for the second portion of the feed air volume, which is compressed to the pressure in the third pressure range, to reach the pressure in the fifth pressure range, the second turbine unit may in particular employ a conventional hydraulic braking or generator braking design.

[0048] In all cases, the fourth portion of the feed air volume compressed to the third pressure range can be cooled together with the second portion of the feed air volume compressed to the third pressure range in the main heat exchanger. The second portion can be discharged from the main heat exchanger at a position corresponding to the temperature within the second temperature range, while the fourth portion can be further cooled and liquefied. The fourth portion can be extracted from the cold side of the main heat exchanger and fed into the high-pressure tower as another controlled flow.

[0049] In the method according to the invention, the two-phase mixture formed at the outlet of the second turbine unit is advantageously fed into a suitable phase separator for phase separation, and then fed into a low-pressure tower in phase separation (i.e., in the form of gas flow and liquid flow).

[0050] In another embodiment of the present invention, the two-phase mixture formed at the outlet of the second turbine unit is fed into the low-pressure tower in a two-phase form. By selecting a suitable two-phase pipeline, the use of a pump can be abandoned because the droplets are entrained due to the relatively high flow rate.

[0051] The present invention further relates to an air separation device for providing pressurized oxygen-enriched air products. Features of the air separation device proposed in this invention are specifically referred to in the corresponding independent claim. The corresponding air separation device benefits from the advantages set forth above regarding the method and preferred embodiments according to the invention; therefore, these advantages are specifically referred to. Specifically, such an air separation device is suitable for implementing the method according to one of the above-described technical solutions and has means designed for this purpose.

[0052] The present invention will now be described in detail with reference to the accompanying drawings illustrating the preferred technical solution of the present invention.

Implementation Method

[0054] FIG1 shows an air separation apparatus according to a preferred embodiment of the present invention, designated as 100. The air separation apparatus 100 has a distillation column system 10, which has a high-pressure column 11 and a low-pressure column 12 connected in a conventional manner. Air separation devices of the type shown in

[0055] are described in numerous other places, for example in Häring (see above), particularly in section 2.2.5, "Cryogenic Rectification". Therefore, for a detailed description of the structure and operation, please refer to the relevant technical documents. The air separation device employing the present invention can be designed in various ways.

[0056] In the technical solution illustrated herein, the high-pressure tower 11 operates within a first pressure range, the low-pressure tower 12 operates within a second pressure range, and at least a dominant portion of the feed air supplied to the entire distillation tower system 10 is compressed to a pressure within a third pressure range in the form of compressed air flow a, which is significantly higher than the first pressure range.

[0057] In the air separation device 100 shown in FIG1, the feed air is drawn in by the main air compressor 1, compressed to a pressure in the third pressure range, cooled in a direct contact cooler (not separately labeled), and in particular water and carbon dioxide are removed in the pre-purification unit 2.

[0058] Subsequently, the feed air supplied as the aforementioned compressed air flow a is divided into two streams, b and c, at a pressure within the third pressure range. Both streams are fed into the main heat exchanger 3 on the hot side and cooled therein. Further streams are formed by extraction at an intermediate temperature level on the cold side of the main heat exchanger 3. These streams constitute a portion of the feed air of the compressed air flow a, referred to herein as the "first" to "fourth" portions, and are designated a1 to a4.

[0059] In the technical solution illustrated here, the first part of the total feed air volume of the compressed air flow a is compressed to the pressure of the third pressure range, and is supplied to the first turbine unit 5 in the form of a split flow a1 at the pressure of the fourth pressure range which is higher than the third pressure range and the temperature of the first temperature range. The compressed air flow a is expanded to the pressure of the first pressure range by the first turbine unit 5 and is sent into the high pressure tower 11.

[0060] Wherein, the first portion (i.e., the diversion a1) as part of the diversion b is pressurized by the pressurization unit 4 to reach a pressure within the fourth pressure range, wherein the pressurization unit 4 is driven by the first turbine unit 5. Before reaching the pressure within the fourth pressure range using the pressurization unit 4, the first portion (i.e., the diversion a1) is cooled in the main heat exchanger 3 in a first cooling step, and after reaching the pressure within the fourth pressure range using the pressurization unit 4, the first portion (i.e., the material flow a1) is cooled in the main heat exchanger 3 in a second cooling step. The second cooling step includes cooling to a temperature within the aforementioned first temperature range.

[0061] In the technical solution illustrated here, the second portion of the feed air volume of the compressed air flow a, which is compressed to the pressure within the third pressure range, is provided to the second turbine unit 6 as part of the split flow c, at the pressure within the third pressure range and the temperature within the second temperature range, in the form of split flow a2. The second turbine unit 6 expands to the pressure within the second pressure range and is then sent to the low-pressure tower 12. In the technical solution illustrated here, the second turbine unit is coupled to the generator G.

[0062] The second temperature range is selected such that a two-phase mixture containing the liquid components repeatedly mentioned above is formed at the outlet of the second turbine unit 6. In the technical solution illustrated here, the two-phase mixture formed at the outlet of the second turbine unit 6 is fed into a phase separator 7 for phase separation, and then separated into liquid stream a2l and gas stream a2g and fed into the low-pressure tower 12.

[0063] The third portion of the feed air volume of the compressed air flow a, which is compressed to the pressure of the third pressure range, together with the first portion (i.e., the split a1) in the form of the above-mentioned split a3, and thus as part of the split b, undergoes the first cooling step, and also reaches the pressure of the fourth pressure range by means of the pressurization unit 4, wherein the third portion (i.e., the split a3) is liquefied in the main heat exchanger 3 at the pressure of the fourth pressure range, expands and is sent to the high pressure tower 11.

[0064] The fourth portion of the feed air volume of the compressed air flow a, which is compressed to the pressure within the third pressure range, is fed into the main heat exchanger 3 together with the second portion (i.e., the split a2) in the form of the above-mentioned split a4, and thus as part of the split c. However, it is not extracted from the main heat exchanger at the temperature within the second temperature range, but is liquefied in the main heat exchanger, then expanded and fed into the high-pressure tower 11.

[0065] In the technical solution illustrated here, the diverters a3 and a4, which are controlled flows, are combined into a total flow k, which is then sent to the high-pressure tower 11.

[0066] In order to provide a gaseous pressurized oxygen-enriched air product, an oxygen-enriched liquid in the form of a feed stream l is extracted from the bottom of the distillation column system 10, more specifically, from the low-pressure column 11. The oxygen-enriched liquid is heated to a temperature in the third temperature range while being heated in a liquid state to a pressure in the sixth pressure range by the internal compression pump 8, evaporates in the main heat exchanger 3 at a temperature in the third temperature range, and is discharged from the air separation device 100.

[0067] For further connections of components of the air separation device 100, which may also include a subcooled countercurrent heat exchanger 9, please refer to the cited technical documents. In particular, only a small portion of the air product is extracted from the air separation device 100 in a non-evaporated liquid form, for example, in the form of a liquid oxygen stream m.

[0068] The main difference between the air separation device 200 according to Figure 2 and the air separation device 100 according to Figure 1 is that the phase separator 7 is not provided, in which the two-phase flow a2 is fed into the low-pressure tower 12 in a two-phase form.

[0069] The main difference between the air separation device 300 according to FIG3 and the air separation devices 100 and 200 according to FIG1 and FIG2 is that the pressurized oxygen-enriched air product is provided in the form of two fractions or streams l1 and l2, which are formed by stream l and evaporated at different pressures in the main heat exchanger 3.

[0070] The main difference between the air separation device 400 according to FIG. 4 and the air separation devices 100 to 300 according to FIG. 1 to 4 is that the second portion a2 (and the fourth portion a4) of the feed air volume compressed to the pressure of the third pressure range is provided at the pressure of the fifth pressure range, while the pressure of the fifth pressure range is achieved by using other pressurization units 41, which are in particular driven by turbine 6 (i.e., "self-pressurization"). The other pressurization units 41 are formed by a thermal pressurization compressor for air, that is, a pressurization compressor with an inlet temperature higher than 273 K.

[0071] The main difference between the air separation device 500 according to Figure 5 and the air separation devices 100 to 400 according to Figures 1 to 4 is the use of a conventional type, such as the argon removal tower 51 described in EP 3 067 649 A1. Argon-enriched gaseous stream s is drawn from the argon removal tower 51 and heated in the main heat exchanger 3. The argon removal tower 51 is fed by the low-pressure tower 12, and the bottom liquid (not separately labeled) is returned to the low-pressure tower 12 after the argon is exhausted. The bottom liquid from the high-pressure tower 11 is used to cool the top condenser of the argon removal tower 51 and, after partial evaporation, is sent to the low-pressure tower 12.

[0072] "Argon removal tower" herein refers to a separation tower used for argon-oxygen separation, which is not used to obtain pure argon product, but rather to remove argon from the air to be separated in the pressure tower and the low-pressure tower. The connection of this separation tower differs only slightly from that of the classic crude argon tower, but the separation tower contains significantly fewer theoretical plates, i.e., fewer than 40, particularly between 35 and 15. Like the crude argon tower, the bottom section of the argon removal tower is connected to the middle section of the low-pressure tower, and the argon removal tower is cooled by a top condenser, on the evaporation side of which the expanded bottom liquid from the high-pressure tower is introduced; the argon removal tower does not have a bottom evaporator.

[0073] Figures 6 and 7 show the enthalpy diagram of the main heat exchanger 3 of an air separation device (e.g., air separation devices 100 to 500 according to Figures 1 to 5) according to a technical solution of the present invention, wherein the vertical axis represents the temperature in K, and the horizontal axis represents the corresponding enthalpy in kW, and the graph in Figure 7 is an enlarged view of the graph in Figure 6. Temperature points Ta1 and Ta2 correspond to the extraction temperature levels of the split streams a1 and a2, respectively.

[0074] Of course, the air separation equipment according to Figures 1 to 5 can also be adjusted to obtain low-pressure nitrogen product (LPGAN) as an air separation byproduct. This can be achieved by appropriately using a corresponding separation section in the low-pressure tower 12. [Simplified Explanation of the Diagram]

[0053] [Figure 1] to [Figure 5] are air separation devices according to a preferred embodiment of the present invention. [Figure 6] and [Figure 7] are temperature-enthalpy diagrams.

Claims

1. A method for producing pressurized oxygen-enriched air product using an air separation device (100), the air separation device having a distillation column system (10) and a main heat exchanger (3), a first turbine unit (5) and a second turbine unit (6), the distillation column system including a high-pressure column (11) and a low-pressure column (12), wherein, - The high-pressure column (11) operates in a first pressure range of 4 to 7 bar, the low-pressure column (12) operates in a second pressure range of 1 to 2 bar, and at least a dominant portion of the feed air supplied to the entire distillation column system (10) is compressed to a pressure in a third pressure range, which is more than 3 bar higher than the first pressure range. - A first portion of the feed air compressed to the pressure in the third pressure range is supplied to the first turbine unit (5) at that pressure in the third pressure range or at a pressure in a fourth pressure range higher than the third pressure range, and at a temperature in the first temperature range. The first turbine unit (5) expands the air to the pressure in the first pressure range and feeds it into the high-pressure column (11). A second portion of the feed air volume compressed to the pressure within the third pressure range is supplied to the second turbine unit (6) at the pressure within the third pressure range or at the pressure within the fifth pressure range above the third pressure range and at the temperature within the second temperature range. The second turbine unit (6) expands the air to the pressure within the second pressure range and feeds it into the low-pressure tower (12). – To provide the pressurized oxygen-enriched air product, an oxygen-enriched liquid is extracted from the distillation tower system (10), which is in a liquid state reaching a pressure within the sixth pressure range of 16 to 50 bar, and fed into the main heat exchanger (3). In the main heat exchanger, the liquid evaporates at a temperature within the third temperature range and is discharged from the air separator (100). The second temperature range is selected such that a two-phase mixture with a liquid content of 5% to 15% is formed at the outlet of the second turbine unit (6). Of all the air products extracted from the air separation device (100), less than 5% are extracted from the air separation device (100) in a liquid, unevaporated form. The device is characterized by: – the third temperature range being higher than the first and second temperature ranges; – the temperatures in the first and second temperature ranges differing from each other by no more than 10 K; – the first portion of the feed air volume compressed to the pressure within the third pressure range being provided at the pressure within the fourth pressure range, and simultaneously reaching the pressure within the fourth pressure range using a booster unit (4); – the booster unit (4) being driven using a first turbine unit (5); and – the second turbine unit (6) being coupled to a generator (G) or to a thermal booster compressor (41) for air.

2. The method as described in claim 1, wherein the first temperature range and the second temperature range are 110 K to 140 K.

3. The method as described in claim 1 or 2, wherein the third temperature range is 10 K higher than the second temperature range.

4. The method as described in claim 1 or 2, wherein the pressurization unit (4) is formed by a refrigeration compressor.

5. The method as described in claim 1 or 2, wherein the first portion of the feed air volume compressed to the pressure within the third pressure range is cooled in the main heat exchanger (3) in a first cooling step before reaching the pressure within the fourth pressure range using the pressurization unit (4), and the first portion of the feed air volume compressed to the pressure within the third pressure range is cooled in the main heat exchanger (3) in a second cooling step after reaching the pressure within the fourth pressure range using the pressurization unit (4), wherein the second cooling step includes cooling to the temperature within the first temperature range.

6. The method as described in claim 5, wherein the third portion of the feed air volume compressed to the third pressure range undergoes the first cooling step together with the first portion of the feed air volume compressed to the third pressure range, and the pressure within the fourth pressure range is reached using the pressurization unit (4), wherein, The third portion of the feed air volume compressed to the pressure within the third pressure range is liquefied in the main heat exchanger at the pressure within the fourth pressure range, and then expands and is fed into the high-pressure tower (11).

7. The method as described in claim 1 or 2, wherein the second portion of the feed air volume compressed to the pressure within the third pressure range is provided at the pressure within the fifth pressure range, and the pressure within the fifth pressure range is simultaneously achieved using another pressurization unit (41).

8. The method as described in claim 1 or 2, wherein the two-phase mixture formed at the outlet of the second turbine unit (6) is subjected to phase separation treatment and then fed into the low-pressure tower (12) by phase separation.

9. The method as described in claim 1 or 2, wherein the two-phase mixture formed at the outlet of the second turbine unit (6) is fed into the low-pressure tower (12) in a two-phase form.

10. An air separation apparatus (100) suitable for producing pressurized, oxygen-enriched air products, and comprising a distillation column system (10), a main heat exchanger (3), a first turbine unit (5), and a second turbine unit (6), the distillation column system including a high-pressure column (11) and a low-pressure column (12), wherein the air separation apparatus (100) is adapted to – operate the high-pressure column (11) in a first pressure range of 4 to 7 bar, operate the low-pressure column (12) in a second pressure range of 1 to 2 bar, and compress at least a dominant portion of the feed air supplied to the entire distillation column system (10) to a pressure in a third pressure range, the third pressure range being at least 3 bar higher than the first pressure range, – A first portion of the feed air, compressed to the pressure within the third pressure range or a pressure within a fourth pressure range higher than the third pressure range, and at a temperature within a first temperature range, is provided to the first turbine unit (5), which expands it to the pressure within the first pressure range and feeds it into the high-pressure tower (111). A second portion of the feed air, compressed to the pressure within the third pressure range or a pressure within a fifth pressure range higher than the third pressure range, and at a temperature within a second temperature range, is provided to the second turbine unit (6), which expands it to the pressure within the second pressure range and feeds it into the low-pressure tower (12). To provide the pressurized oxygen-enriched air product, an oxygen-enriched liquid is extracted from the distillation column system (10), and while heating the oxygen-enriched liquid to a temperature within a third temperature range, it is brought to a pressure within a sixth pressure range of 16 to 50 bar, causing it to evaporate in the main heat exchanger (3) at that temperature within the third temperature range and discharged from the air separation unit (100). Furthermore, less than 5% of all air product extracted from the air separation unit (100) is extracted from the air separation unit (100) in an unevaporated liquid state. - The second temperature range is selected such that a two-phase mixture with a liquid content of 5% to 15% is formed at the outlet of the second turbine unit (6), characterized in that: - the air separation device (100) is adapted to make the third temperature range higher than the first temperature range and the second temperature range by extracting from the main heat exchanger (3) at an appropriate location; - the temperature in the first temperature range and the temperature in the second temperature range differ from each other by no more than 10 K; and - the air separation device (100) is adapted to - the first portion of the feed air volume compressed to the pressure in the third pressure range is provided at the pressure in the fourth pressure range, and the pressure in the fourth pressure range is achieved by using the booster unit (4); - the booster unit (4) is driven by using the first turbine unit (5); and - the second turbine unit (6) is coupled to a generator (G) or to a thermal booster compressor (41) for air.

11. The air separation device (100) as claimed in claim 10, wherein the pressurization unit (4) is formed by a cold compressor.

12. The air separation device (100) as described in claim 10 or 11 is adapted to implement the method as described in any one of claims 1 to 9.

Images